HK1193508B - Tunable wireless power architectures - Google Patents

Description

Tunable wireless power supply architecture

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority from U.S. provisional patent application 61/515,324 filed on 8/4/2011.

Technical Field

The present disclosure relates to wireless energy transfer, methods, systems, and apparatus, and applications to accomplish such transfer.

Background

Various well-known radiated or far-field and non-radiated or near-field techniques may be used to wirelessly Transfer Energy or power, such as those described in detail in commonly owned U.S. patent application Ser. No. 12/613,686 entitled "Wireless Energy Transfer System" published as US2010/010909445 at 5/6 2010, U.S. patent application Ser. No. 12/860,375 entitled "Integrated Resonator-Shield Structure" published as 2010/0308939 at 12/9 2010, U.S. patent application Ser. No. 13/222,006915 entitled "Low Resistance electric Conductor" published as 2012/2345 at 3/15 2012, U.S. patent application Ser. No. 13/283,811 entitled "Multi-Resonator Wireless Energy Transfer for Lighting", the contents of which are incorporated by reference. Prior art wireless energy transfer systems are limited by various factors, including concerns over user safety, low energy transfer efficiency, and limited physical proximity/alignment tolerances of the energy supply (power supply) and receiver components.

One particular challenge in wireless energy transfer is the control and tuning of the resonator structure and power supply to deliver a controlled power supply to the load. In a wireless energy transfer system, the source and device may move or change positions. As the relative positioning of the system elements changes, the characteristics of the wireless energy transfer also change. The coupling between the source and the device may be varied, for example to reduce the efficiency of the energy transfer. Changes in the wireless energy transfer characteristics may change the power delivered to the load or cause unwanted fluctuations in the power delivered to the load at the device. There is a need for methods and designs for tunable wireless energy transfer systems having tunable components to maintain efficient and constant energy transfer to the load of the device regardless of variations in positioning, coupling, orientation, etc. of the system components.

Disclosure of Invention

In various embodiments, various systems and processes provide wireless energy transfer using coupled resonators. In certain embodiments, the wireless energy transfer system may require or benefit from the ability to verify and authenticate the source and receiver of the wireless energy. The features of these embodiments are generic and can be applied to a wide range of resonators, regardless of the specific examples described herein.

In embodiments, the magnetic resonator may include some combination of inductors and capacitors. Additional circuit elements such as capacitors, inductors, resistors, switches, etc. may be interposed between the magnetic resonator and the power source, and/or between the magnetic resonator and the power load. In the present disclosure, the conductive coil of the high Q inductive loop including the resonator may be referred to as an inductor and/or an inductive load. An inductive load may also refer to an inductor when it is wirelessly coupled (through mutual inductance) to other systems or foreign objects. In the present disclosure, circuit elements other than inductive loads may also be referred to as components of an impedance matching network or IMN. It should be understood that all, some of the elements referred to as components of the impedance matching network may or may not be components of the magnetic resonator. Which elements are part of the resonator and which are separate from the resonator will depend on the particular magnetic resonator and wireless energy transfer system design.

Unless otherwise indicated, this disclosure uses the terms wireless energy transfer, wireless power transfer, and the like interchangeably. Those skilled in the art will appreciate that a wide range of wireless system designs and functions described in this application may support a variety of system architectures.

In the wireless energy transfer system described herein, power may be wirelessly exchanged between at least two resonators. The resonator may provide, receive, hold, transfer, and distribute energy. The source of wireless power may be referred to as a source or power source and the recipient of wireless power may be referred to as a device, receiver, and power load. The resonator may be a source, a device, or both, or may change from one function to another in a controlled manner. Resonators configured to hold or distribute energy that do not have a wired connection to a power source or power drain may be referred to as repeaters.

The resonator of the wireless energy transfer system of the present invention is capable of transferring power over a large distance compared to the size of the resonator itself. That is, if the resonator size is characterized by the radius of the smallest sphere that can enclose the resonator structure, the wireless energy transfer system of the present invention can transfer power over a distance that is greater than the characteristic size of the resonator. The system is capable of exchanging energy between resonators, wherein the resonators have different characteristic dimensions, and wherein the inductive elements of the resonators have different dimensions, different shapes, are composed of different materials, etc.

The wireless energy transfer system of the present invention can be described as having a coupling region, powered region or volume by stating that energy can be transferred between resonant objects that are separated from each other, which can be at variable distances from each other and can move relative to each other. In certain embodiments, the area or mention through which energy is transferred may be referred to as an active field area or mention. Additionally, the wireless energy transfer system may include more than two resonators, each of which may be coupled to the power source, the power load, or both, or neither.

The wirelessly provided energy may be used to power an electrical or electronic device, recharge a battery or charge an energy storage unit. Multiple devices may be charged or powered simultaneously, or power transfer to multiple devices may be serialized such that one or more devices receive power for a period of time, after which power transfer may be switched to other devices. In various embodiments, multiple devices may share power from one or more sources with one or more other devices simultaneously, or in a time-multiplexed manner, or in a frequency-multiplexed manner, or in a space-multiplexed manner, or in a directional-multiplexed manner, or in any combination of time-multiplexed, frequency-multiplexed, space-multiplexed, and directional-multiplexed. Multiple devices may share power with each other, with at least one device continuously, intermittently, periodically, occasionally, or temporarily reconfiguring to operate as a wireless power source. One of ordinary skill in the art will appreciate that there are various ways of powering and/or charging a device that are suitable for the techniques and applications described herein.

The present disclosure makes reference to certain individual circuit components and elements such as capacitors, inductors, resistors, diodes, transformers, switches, and the like; combinations of these elements as networks, topologies, circuits, and the like; and objects with intrinsic properties, such as "self-resonant" objects with capacitance or inductance distributed throughout the object (or locally, as opposed to completely lumped). It will be appreciated by those of ordinary skill in the art that adjusting and controlling variable components within a circuit or network may adjust the performance of the circuit or network, and that such adjustments may be generally described as tuning, adjusting, matching, correcting, etc. Other methods of tuning or adjusting the operating point of a wireless power transfer system may be used alone or in addition to adjusting tunable components such as inductors and capacitors, or a combination of inductors and capacitors. Those skilled in the art will appreciate that the particular topologies described in this disclosure may be implemented in a variety of other ways.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. This specification, including definitions, will control in case of conflict with publications, patent applications, patents, and other references mentioned or incorporated herein by reference.

Any of the features described above may be used alone or in combination without departing from the scope of the present disclosure. Other features, objects, and advantages of the systems and methods disclosed herein will be apparent from the detailed description and drawings that follow.

Drawings

Fig. 1 is a system block diagram of a wireless energy transfer configuration.

Fig. 2A-2E are exemplary structures and schematic diagrams of a simple resonator structure.

Fig. 3 is a block diagram of a wireless source with a single-ended amplifier.

Fig. 4 is a block diagram of a wireless source with a differential amplifier.

Fig. 5A and 5B are block diagrams of a sensing circuit.

Fig. 6A, 6B, and 6C are block diagrams of wireless sources.

Fig. 7 is a graph showing the effect of duty cycle on the parameters of the amplifier.

Fig. 8 is a simplified circuit diagram of a wireless power supply with a switching amplifier.

Fig. 9 shows a graph of the effect of a change in a parameter of a wireless power supply.

Fig. 10 shows a graph of the effect of a change in a parameter of a wireless power supply.

Fig. 11A, 11B, and 11C are graphs showing the influence of parameter variations of the wireless power supply.

Fig. 12 shows a graph of the effect of a change in a parameter of a wireless power supply.

Fig. 13 is a simplified circuit diagram of a wireless energy transfer system including a wireless power supply with a switching amplifier and a wireless power device.

Fig. 14 shows a graph of the effect of a change in a parameter of a wireless power supply.

Fig. 15 is a diagram of a resonator showing a possible inhomogeneous magnetic field distribution due to irregular spacing between tiles of magnetic material.

Fig. 16 is a diagram of resonators having a tiled arrangement in a block of magnetic material that can reduce hot spots in the block of magnetic material.

Fig. 17A is a resonator with a block of magnetic material comprising a smaller single block of bricks, and fig. 17B and 17C are resonators with additional strips of thermally conductive material for thermal management.

Fig. 18 is a block diagram of a wireless energy transfer system with in-band and out-of-band communication channels.

Fig. 19A and 19B are steps that may be used to validate an energy delivery channel using an out-of-band communication channel.

Fig. 20A and 20B are block diagrams of wireless energy transfer system electronics.

Fig. 21A and 21B are block diagrams of wireless energy transfer systems with tunable electronics.

Fig. 22A and 22B are simplified schematic diagrams of a wireless energy transfer system with tunable electronics, and fig. 22C is a specific embodiment of a switching element.

Fig. 23A to 23D are diagrams illustrating the operation of the amplifier.

Fig. 24 is a block diagram of an embodiment of a tunable wireless energy transfer system.

Fig. 25 is a schematic diagram of an embodiment of a tunable wireless energy transfer system.

Fig. 26 is a schematic diagram of an embodiment of a source with a balanced impedance matching network.

Detailed Description

As mentioned above, the present disclosure relates to wireless energy transfer using coupled electromagnetic resonators. Such energy transfer is not limited to electromagnetic resonators and the wireless energy transfer systems described herein are more general and can be implemented using a wide range of resonators and resonant objects.

Those skilled in the art will appreciate that important considerations for resonator-based power transfer include resonator efficiency and resonator coupling. An extensive discussion of such problems, such as Coupling Mode Theory (CMT), coupling coefficients and factors, quality factors (also referred to as Q factors) and impedance matching, is provided, FOR example, in U.S. patent APPLICATION 12/789,611 entitled "RESONATOR arrysfor WIRELESS ENERGY TRANSFER," published as US20100237709 at 23.2010, and U.S. patent APPLICATION 12/722,050 entitled "WIRELESS ENERGY TRANSFER FOR regenerative APPLICATION," published as US20100181843 at 22.2010, and is hereby incorporated by reference herein in its entirety as if fully set forth herein.

A resonator may be defined as a resonant structure capable of storing energy in at least two different forms, and wherein the stored energy oscillates between the two forms. The resonant structure has a specific oscillation mode, with a resonant (modal) frequency f and a resonant (modal) field. The angular resonance frequency ω may be defined as ω =2 π f, the resonance period T may be defined as T =1/f =2 π/ω, and the resonance wavelength λ may be defined as λ = c/f, where c is the velocity of the relevant field wave (light for an electromagnetic resonator). In the absence of a loss mechanism, a coupling mechanism, or an external energy supply or drain mechanism, the total amount of energy W stored by the resonator remains fixed, but the form of the energy will oscillate between the two forms supported by the resonator, where one form is the smallest and the other is the largest, and vice versa.

For example, the resonator may be constructed such that the two forms of energy stored are magnetic energy and electrical energy. Furthermore, the resonator may be constructed such that the electrical energy stored by the electric field is confined primarily within the structure, while the magnetic energy stored by the magnetic field is primarily in the region surrounding the resonator. In other words, the total electrical and magnetic energy will be equal, but their positioning will be different. With this structure, the energy exchange between the at least two structures can be regulated by the resonant magnetic near fields of the at least two resonators. These types of resonators may be referred to as magnetic resonators.

An important parameter of a resonator for a wireless power transfer system is the quality factor or Q-factor or Q of the resonator, which characterizes the energy attenuation and is inversely proportional to the energy loss of the resonator. It may be defined as Q = ω W/P, where P is the time average power consumption at steady state. That is, a resonator with a high Q has a relatively low intrinsic loss and can store energy for a relatively long time. Since the resonator loses energy at its intrinsic decay rate 2 Γ, its Q, also called its intrinsic Q, is given by Q = ω × W/2 Γ. The quality factor also represents the number of oscillation periods T, which is the energy in the resonator by a factor e^-2πThe attenuation costs. Note that the quality factor or intrinsic quality factor or Q of the resonator is due only to intrinsic loss mechanisms. The Q of a resonator connected or coupled to the generator g or to the load l may be referred to as the "loaded quality factor" or "loaded Q". In the case where there are external objects that are not intended to be components of the energy transfer system, the Q of the resonator may be referred to as a "perturbation quality factor" or "perturbation Q".

Resonators coupled through any part of their near field can interact and exchange energy. The efficiency of this energy transfer is significantly improved if the resonators are operated at substantially the same resonant frequency. By way of example, but not limitation, it is contemplated to have Q_sAnd a source resonator having Q_dThe device resonator of (1). High Q wireless energy transfer systems may utilize high Q resonators. The Q of each resonator may be high. Geometric averaging of resonator QMay also or instead be high.

Coupling factork is a number between 1 ≦ k ≦ 1, which may be independent (or nearly independent) of the resonant frequency of the source and device resonators when they are placed over sub-wavelength long distances. Instead, the coupling factor k may be determined primarily by the relative geometry and distance between the source and the device resonator, taking into account the laws of physical attenuation of the field that regulates its coupling. Coupling coefficient for use in MTMay be a strong function of the resonant frequency as well as other characteristics of the resonator structure. In applications of wireless energy transfer utilizing the near field of the resonator, it is desirable to make the size of the resonator much smaller than the resonant wavelength in order to reduce power loss due to radiation. In some embodiments, the high Q resonator is a sub-wavelength structure. In certain electromagnetic embodiments, the high Q resonator structure is designed to have a resonant frequency above 100 kHz. In other embodiments, the resonant frequency may be less than 1 GHz.

In an exemplary embodiment, the power radiated into the far field by these sub-wavelength resonators may be further reduced by lowering the resonant frequency of the resonators and the operating frequency of the system. In other embodiments, far field radiation may be reduced by arranging two or more resonators for the far field to interfere destructively in the far field.

In a wireless energy transfer system, the resonator may function as a wireless energy source, a wireless energy capture device, a repeater, or a combination thereof. In embodiments, the resonator may alternate between transferring energy, receiving energy, or relaying energy. In a wireless energy transfer system, one or more magnetic resonators may be coupled to an energy source, energized to generate an oscillating magnetic near-field. Other resonators within the oscillating magnetic near field can capture these fields and convert the energy into electrical energy, which can be used to power or charge a load, thereby enabling wireless transfer of useful energy.

So-called "useful" energy in the exchange of useful energy is energy or power that must be transferred to a device in order to power or charge it at an acceptable rate. The transfer efficiency corresponding to the exchange of useful energy may be system or application dependent. For example, high power vehicle charging applications that deliver several kilowatts of power need to be at least 80% efficient in order to provide a useful amount of power, resulting in a useful energy exchange that is sufficient to charge the vehicle battery without significant heating of the various components of the delivery system. In certain consumer electronics applications, useful energy exchange may include any energy transfer efficiency greater than 10% or any other amount that is acceptable to keep the rechargeable battery "finished" and running for a long period of time. In implanted medical device applications, the useful energy exchange may be any exchange that does not harm the patient but extends battery life, or wakes up sensors or monitors or actuators. In such applications, 100mW or less of power is useful. In distributed sensing applications, milliwatt power transfer may be useful, and transfer efficiency may be much lower than 1%.

Useful energy exchange for wireless energy transfer in power or charging applications may be efficient, extremely efficient, or sufficiently efficient, provided that the degree of wasted energy, heat dissipation, and associated field strength are within allowable limits and properly balanced with relevant factors, such as cost, weight, size, and the like.

The resonators may be referred to as a source resonator, a device resonator, a first resonator, a second resonator, a repeater resonator, etc., and implementations may include three (3) or more resonators. For example, a single source resonator may transfer energy to multiple device resonators or multiple devices. Energy may be transferred from a first device to a second device, then from the second device to a third device, and so on. Multiple sources may transfer energy to a single device, or multiple devices connected to a single device resonator, or multiple devices connected to multiple device resonators. The resonators may alternately or simultaneously act as sources, devices, and/or they may be used to relay power from a source at one location to a device at another location. The intermediate electromagnetic resonator may be used to extend the range of the wireless energy transfer system and/or to generate a concentrated magnetic near field region. Multiple resonators may be daisy chained together to exchange energy over extended distances with a wide range of sources and devices. For example, a source resonator may transfer power to a device resonator via several repeater resonators. Energy from the source may be transferred to a first transponder resonator, which may transfer power to a second transponder resonator, second through third, and so on until the final transponder resonator transfers its energy to the device resonator. In this regard, the range or distance of wireless energy transfer may be extended and/or adjusted by adding a repeater resonator. The high power level may be divided among multiple sources, delivered to multiple devices and recombined at a remote location.

The resonator may be designed using a coupling mode theoretical model, a circuit model, an electromagnetic field model, and the like. The resonator may be designed with tunable feature sizes. The resonator may be designed to handle different power levels. In an exemplary embodiment, a high power resonator may require a larger conductor and higher current or voltage rated components than a low power resonator.

Fig. 1 shows a diagram of an exemplary structure and arrangement of a wireless energy transfer system. The wireless energy transfer system may include at least one source resonator (R1) 104 (optionally R6, 112) coupled to an energy source 102 and optionally a sensor and control unit 108. The energy source may be any type of energy source that can be converted to electrical energy that may be used to drive the source resonator 104. The energy source may be a battery, solar panel, electric mains, wind or water turbine, electromagnetic resonator, generator, or the like. The electric energy for driving the magnetic resonator is converted into an oscillating magnetic field by the resonator. The oscillating magnetic field may be captured by other resonators, which may be device resonators (R2) 106, (R3) 116, which may optionally be coupled to energy-consuming devices 110. The oscillating field may optionally be coupled to a transponder resonator (R4, R5) configured to expand or adjust the wireless energy transfer region. The device resonator may capture magnetic fields in the vicinity of the source resonator, transponder resonator, and other device resonators and convert them into electrical energy, which may be used by the energy consumer. Energy consuming device 110 may be an electrical, electronic, mechanical, or chemical device, or the like, configured to receive electrical energy. The transponder resonator may capture magnetic fields in the vicinity of the source, device, and transponder resonator and may transfer energy to other resonators.

The wireless energy transfer system may include a single source resonator 104 coupled to the energy source 102 and a single device resonator 106 coupled to the energy consumer 110. In embodiments, the wireless energy transfer system may include a plurality of source resonators coupled to one or more energy sources, and may include a plurality of device resonators coupled to one or more energy consuming devices.

In an embodiment, energy may be transferred directly between the source resonator 104 and the device resonator 106. In other embodiments, energy may be transferred from one or more source resonators 104, 112 to one or more device resonators 106, 116 via any number of intermediate resonators, which may be device resonators, source resonators, repeater resonators, or the like. Energy may be transferred via the network or devices of the resonator 114, which may include sub-networks 118, 120 arranged in any combination of topologies such as token ring, mesh, ad hoc, etc.

In an embodiment, the wireless energy transfer system may include a centralized sensing and control system 108. In an embodiment, parameters of the resonator, energy source, energy consumer, network topology, operating parameters, etc. may be monitored and adjusted by the control processor to meet specific operating parameters of the system. The central control processor may adjust parameters of individual components of the system to optimize overall energy transfer efficiency, optimize the amount of power transferred, and the like. Other embodiments may be designed with a substantially distributed sensing and control system. Sensing and control may be included in each resonator or group of resonators, energy sources, energy consumers, etc., and may be configured to adjust parameters of individual components in the group to maximize or minimize power delivered, maximize energy transfer efficiency in the group, etc.

In embodiments, components of a wireless energy transfer system may have wireless or wired data communication links to other components such as devices, sources, repeaters, power sources, resonators, and the like, and may send or receive data, which may be used to implement distributed or centralized sensing and control. The wireless communication channel may be separate from the wireless energy transfer channel, or it may be the same. In one embodiment, the resonators used for power exchange may also be used to exchange information. In some cases, information may be exchanged by modulating components in the source or device circuitry and sensing the change with a port parameter or other monitoring device. The resonators may signal each other by tuning, varying, changing, dithering, etc. resonator parameters, such as resonator impedance, which may affect the reflected impedance of other resonators in the system. The systems and methods described herein may enable the simultaneous transmission of power and communication signals between resonators in a wireless power transfer system, or may enable the transmission of power and communication signals in different time periods or at different frequencies using the same magnetic field as in a wireless energy transfer process. In other embodiments, wireless communication may be implemented in a separate wireless communication channel, such as WiFi, bluetooth, infrared, NFC, or the like.

In embodiments, the wireless energy transfer system may comprise a plurality of resonators, and the overall system performance may be improved by control of a plurality of elements in the system. For example, a device with lower power requirements may tune its resonant frequency away from the resonant frequency of a high power source supplying the device with higher power requirements. For another example, devices requiring less power may adjust their rectifier circuits so that they draw less power from the source. In these ways, both low and high power devices may be safely operated or charged from a single high power source. In addition, multiple devices in the charging region may find their available power, adjusted according to any of various consumption control algorithms, e.g., first come first serve, best effort, guaranteed power, etc. The power consumption algorithm may be hierarchical in nature, giving priority to certain users or classes of devices, or it may support any number of users by equally sharing the power available in the source. Power may be shared by any multiplexing technique described in this disclosure.

In embodiments, electromagnetic resonators may be implemented or embodied using a combination of shapes, structures, and configurations. The electromagnetic resonator may comprise an inductive element, a distributed inductance, or a combination of inductances with a total inductance L, and a combination of capacitive elements, distributed capacitances, or capacitances with a total capacitance C. The minimum circuit model of an electromagnetic resonator includes capacitance, inductance, and resistance, shown in fig. 2F. The resonator may include an inductive element 238 and a capacitive element 240. In the event that initial energy is provided, such as electric field energy stored in the capacitor 240, the system will oscillate as the capacitor discharges, transferring energy to magnetic field energy stored in the inductor 138, which in turn transfers energy back to the electric field energy stored in the capacitor 240. Intrinsic losses in these electromagnetic resonators include losses due to resistive and radiative losses in the inductive and capacitive elements, represented by resistor R242 in fig. 2F.

Fig. 2A shows a simplified diagram of an exemplary magnetic resonator structure. The magnetic resonator may comprise a conductor loop, acting as an inductive element 202 and a capacitive element 204 at the ends of the conductor loop. The inductor 202 and capacitor 204 of the electromagnetic resonator may be bulk circuit elements, or the inductance and capacitance may be distributed and may result from the manner in which the conductors are formed, shaped or positioned in the structure.

For example, inductor 202 may be obtained by shaping a conductor to surround a surface area, as shown in fig. 2A. Such resonators may be referred to as capacitively loaded loop inductors. Note that we can use the term "loop" or "coil" to generally refer to a conductive structure (wire, tube, ribbon, etc.) that encompasses a surface of any shape and size, with any number of bends. In FIG. 2A, the enclosed surface area is circular, but the surface may be any of a variety of other shapes and sizes and may be designed to achieve a particular system performance specification. In embodiments, inductance may be implemented using inductor elements, distributed inductance, networks, arrays, series and parallel combinations of inductors and inductances, and so forth. The inductance may be fixed or variable and may be used to vary the impedance matching and resonant frequency operating conditions.

There are various ways to obtain the capacitance required to achieve the desired resonant frequency of the resonator structure. Capacitor plates 204 may be formed and used as shown in fig. 2A, or the capacitance may be distributed and may be implemented between adjacent windings of a multi-loop conductor. Capacitance may be implemented using capacitor elements, distributed capacitance, networks, arrays, series and parallel combinations of capacitance, and the like. The capacitance may be fixed or variable and may be used to vary the impedance matching and resonant frequency operating conditions.

An inductive element used in a magnetic resonator may contain more than one loop and may spiral inward or outward or upward or downward or in some combination of directions. In general, magnetic resonators can have bends of various shapes, sizes, and numbers, which can be composed of various conductive materials. For example, the conductor 210 may be a wire, strand, tape, tube, trace formed from conductive ink, paint, gel, or the like, or a trace formed from a single or multiple traces printed on a circuit board. An exemplary embodiment of the trace pattern on the backplane 208 that forms the conductive loop is shown in fig. 2B.

In embodiments, the inductive element may be formed using any size, shape, thickness, etc. of magnetic material or from materials having a wide range of permeability and loss values. These magnetic materials may be solid blocks that may enclose a hollow volume, they may be made up of many smaller bricks of magnetic material laid and/or stacked together, they may be integrated with a conductive sheet or housing made of highly conductive material. A conductor may be wrapped around the magnetic material to generate a magnetic field. These conductors may be wound around one or more axes of the structure. Multiple conductors may be wound around the magnetic material, in parallel or in series or combined via switches to form a specifically tailored near-field pattern and/or dipole moment of the directional structure. Examples of resonators comprising magnetic material are shown in fig. 2C, 2D, 2E. In fig. 2D, the resonator includes a loop of conductor 224, wrapped around a core of magnetic material 222, creating a structure with a magnetic dipole moment 228 parallel to the axis of the loop of conductor 224. Depending on how the conductors are driven, the resonator may include multiple loops of conductors 216, 212 wound in orthogonal directions around magnetic material 214, constituting a resonator with magnetic dipole moments 218, 220 oriented in more than one direction, as shown in fig. 2C.

An electromagnetic resonator may have a characteristic, intrinsic property, or resonant frequency determined by its physical properties. This resonance frequency is the energy W stored by the resonator in the electric field of the resonator_E（W_E=q²/2C, where q is the charge on the capacitor C) and the energy W stored by the magnetic field_B（W_B=Li²Where i is the current through the inductor L). The frequency at which it exchanges energy may be referred to as the characteristic frequency, natural frequency or resonant frequency of the resonator, given by omega,

the resonance frequency of the resonator can be changed by tuning the inductance L and/or the capacitance C of the resonator. In one embodiment, the system parameters are dynamically adjustable or tunable to achieve as close to optimal operating conditions as possible. Based on the above discussion, however, a sufficiently efficient energy exchange can be achieved even when certain system parameters are not variable or components cannot be dynamically adjusted.

In an embodiment, the resonator may comprise an inductive element coupled to more than one capacitor and a circuit element arranged in a capacitor network. In an embodiment, a coupling network of capacitors and circuit elements may be used to define more than one resonance frequency of a resonator. In embodiments, the resonator may resonate or partially resonate at more than one frequency.

In an embodiment, the wireless power source may comprise at least one resonator coil coupled to a power source, which may be a switching amplifier, such as a class D amplifier or a class E amplifier, or a combination thereof. In this case, the resonator is actually the power load of the power supply. In an embodiment, a wireless power device may include at least one resonator coil coupled to a power load, which may be a switching rectifier, such as a class D rectifier or a class E rectifier, or a combination thereof. In this case, the resonator coil is actually the power source for the power load, and the impedance of the load is also directly related to the work-rejection rate of the load from the resonator coil. The efficiency of power transfer between a power source and a power load can be affected by how closely the output impedance of the power source matches the input impedance of the load. When the input impedance of the load is equal to the complex conjugate of the internal impedance of the power supply, power can be delivered to the load with as much efficiency as possible. Designing the power supply or power load impedance to achieve maximum power transfer efficiency is often referred to as "impedance matching," and may also be referred to as optimizing the ratio of useful-lost power in the system. Impedance matching may be performed by adding a network or group of elements, such as capacitors, inductors, transformers, switches, resistors, etc., to form an impedance matching network between the power source and the power load. In embodiments, mechanical adjustments and changes in component positioning may be used to achieve impedance matching. For varying loads, the impedance matching network may include variable components that are dynamically tunable to ensure that the impedance at the power supply end towards the load and the characteristic impedance of the power supply remain substantially complex conjugates of each other, even under dynamic environments and operating conditions.

In embodiments, impedance matching may be accomplished by tuning the duty cycle and/or phase and/or frequency of the drive signal of the power supply, or by tuning physical components within the power supply, such as capacitors. This tuning mechanism is advantageous because it can allow impedance matching between the power supply and the load without the use of a tunable impedance matching network, or with a simplified tunable impedance matching network, e.g., a network with fewer tunable components. In embodiments, tuning to the duty cycle and/or frequency and/or phase of the drive signal of the power supply may result in a dynamic impedance matching system, with extended tuning range or accuracy, with higher power, voltage and/or current performance, with faster electronic control, with fewer external components, and/or the like.

In some wireless energy transfer systems, resonator parameters such as inductance can be affected by environmental conditions, such as surrounding objects, temperature, orientation, number and location of other resonators, and the like. Changes in the resonator's operating parameters may change certain system parameters, such as the efficiency of power transfer in wireless energy transfer. For example, a highly conductive material located near the resonator may shift the resonant frequency of the resonator and detune it from other resonant objects. In some embodiments, a resonator feedback mechanism is used that corrects its frequency by changing a reactive element (e.g., an inductive element or a capacitive element). At least some of the system parameters need to be dynamically adjustable or tunable in order to achieve acceptable matching conditions. All system parameters may be dynamically adjustable or tunable to achieve substantially optimal operating conditions. However, a sufficiently efficient energy exchange can be achieved even if all or part of the system parameters are not variable. In some instances, at least some of the devices may not be dynamically adjustable. In some instances, at least some of the sources may not be dynamically adjustable. In some instances, at least some of the intermediate resonators may not be dynamically adjustable. In some instances, none of the system parameters may be dynamically adjustable.

In some embodiments, variations in parameters of a component may be mitigated by selecting a component whose characteristics change in a complementary or opposite manner or direction when subject to differences in operating environment or operating point. In an embodiment, the system may be designed with components such as capacitors having opposite dependencies or parameter variations depending on temperature, power level, frequency, etc. In some embodiments, the component values as a function of temperature may be stored in a look-up table in the system microcontroller and readings from the temperature sensor may be used in a system control feedback loop to adjust other parameters to compensate for temperature-induced component value changes.

In some embodiments, variations in component parameter values may be compensated for by means of an active tuning circuit comprising a tunable component. Circuits that monitor the operating environment and operating point of the components and systems may be integrated into the design. The monitoring circuit may provide the signals necessary to actively compensate for changes in the component parameters. For example, the temperature readings may be used to calculate a desired change in system capacitance, or to indicate a previously measured system capacitance value, allowing compensation by switching in other capacitors or tuning capacitors to maintain a desired capacitance over a temperature range. In an embodiment, the RF amplifier switching waveform may be adjusted to compensate for component value or load variations in the system. In certain embodiments, changes in component parameters may be compensated for by active cooling, heating, active environmental adjustments, and the like.

Parameter measurement circuits may measure or monitor specific power, voltage and current, signals in the system, and a processor or control circuit may adjust specific settings or operating parameters based on these measurements. In addition, the magnitude and phase of the voltage and current signals, and the magnitude of the power signals, throughout the system may be obtained to measure or monitor system performance. The measurement signals referred to throughout this disclosure may be port parameter signals as well as any combination of voltage signals, current signals, power signals, temperature signals, and the like. These parameters may be measured using analog or digital techniques, sampled and processed, and digitized or converted using well-known analog and digital processing techniques. In an embodiment, preset values for certain measurements may be loaded into a system controller or memory unit and used in a plurality of feedback and control loops. In embodiments, any combination of measured, monitored, and/or preset signals may be used in a feedback circuit or system to control the operation of the resonator and/or system.

The adjustment algorithm may be used to adjust the frequency, Q, and/or impedance of the magnetic resonator. The algorithm may take as input a reference signal that is related to a degree of deviation from a desired operating point of the system and may output a correction or control signal related to the deviation that controls a variable or tunable element of the system to bring the system back to the desired operating point or points. The reference signal for the magnetic resonators may be obtained when the resonators exchange power in a wireless power transfer system, or they are cut off from the circuit during system operation. Corrections to the system may be applied or performed continuously, periodically, based on crossing a threshold, digitally, using analog methods, and so forth.

In embodiments, lossy external materials and objects may introduce potential efficiency degradation by absorbing magnetic and/or electrical energy of resonators of a wireless power transfer system. In various embodiments, these effects are mitigated by positioning the resonators to minimize the effects of lossy external materials and objects, and by arranging the structured field shaping elements (e.g., conductive structures, plates and sheets, magnetic material structures, plates and sheets, combinations thereof) to minimize their effects.

One way to reduce the effect of lossy materials on the resonator is to shape the resonator field using high conductivity materials, magnetic materials, or a combination thereof, so that they avoid the lossy objects. In an exemplary embodiment, the layered structure of high conductivity materials and magnetic materials may adjust, shape, point, redirect, etc., the electromagnetic fields of the resonators such that they avoid lossy objects in their vicinity by deflecting the fields. Fig. 2D shows a top view of a resonator with a conductor foil 226 under the magnetic material, which can be used to adjust the field of the resonator so that they avoid lossy objects under the conductor foil 226. The good conductor layer or sheet 226 may comprise any highly conductive material, such as copper, silver, aluminum, as is most appropriate for a given application. In some embodiments, the layer or sheet of good conductor is thicker than the skin depth of the conductor at the resonator operating frequency. The conductor foil may preferably be larger than the dimensions of the resonator, extending beyond the physical extent of the resonator.

In environments and systems where the amount of power transferred poses a safety hazard to humans or animals intruding into the active field volume, safety measures may be included in the system. In embodiments where the power stage requires specialized safety measures, the packaging, structure, materials, etc. of the resonator may be designed to provide a separation or "keep-out" zone from the conductive loop in the magnetic resonator. To provide further protection, high Q resonators and power and control circuitry may be provided within the enclosure that confines high voltages or currents within the enclosure, protecting the resonators and electrical components from weather, humidity, sand, dust and other external factors, as well as shock, vibration, scratching, explosion and other types of mechanical shock. Such enclosures focus on a number of factors such as heat dissipation in order to maintain an acceptable operating temperature range for the electrical components and resonators. In embodiments, the housing may be constructed of non-destructive materials, such as composites, plastics, wood, concrete, etc., and may be used to provide a minimum distance from the lossy object to the resonator component. The efficiency of wireless energy transfer may be improved from a minimum separation distance that may include metallic objects, salt water, oil, etc., that are damaging to the object or environment. In an embodiment, the "keep-out" zone may be used to increase the disturbance Q of the resonator or the system of resonators. In both embodiments, the minimum separation distance may provide a more reliable or constant resonator operating parameter.

In embodiments, the resonators and their respective sensors and control circuits may have multiple levels of integration with other electronics and control systems and subsystems. In some embodiments, the power and control circuitry is a completely separate module or housing from the device resonator, with minimal integration with existing systems, providing power output and control and diagnostic interfaces, in some embodiments, the device is configured to house the resonator and circuit components within a cavity in the housing, or integrated into the chassis or housing of the device.

Exemplary resonator Circuit

Fig. 3 and 4 show high-level block diagrams illustrating power generation, monitoring and control components for an exemplary source of a wireless energy transfer system. Fig. 3 is a block diagram of a source including a half-bridge switching power amplifier and some associated measurement, tuning and control circuitry. Fig. 4 is a block diagram of a source including a full bridge switching power amplifier and some associated measurement, tuning and control circuitry.

The half-bridge system topology shown in fig. 3 may include a processing unit that executes a control algorithm 328. The processing unit executing the control algorithm 328 may be a microcontroller, an application specific integrated circuit, a field programmable gate array, a processor, a digital signal processor, or the like. The processing unit may be a single device or it may be a network of devices. The control algorithm may run on any part of the processing unit. The algorithms may be customized for a particular application and may include a combination of analog and digital circuits and signals. The main algorithm can measure and adjust voltage signals and levels, current signals and levels, signal phases, digital count settings, etc.

The system may include an optional source/device and/or source/other resonator communication controller 332 coupled to the wireless communication circuit 312. The optional source/device and/or source/other resonator communication controller 332 may be a component of the same processing unit as executes the main control algorithm, may be a component or circuitry within the microcontroller 302, may be external to the wireless power transfer module, may be substantially similar to a communication controller used in wired-powered or battery-powered applications, but adapted to include some new or different functionality to enhance or support wireless power transfer.

The system may include a PWM generator 306 coupled to at least two transistor gate drivers 334 and may be controlled by a control algorithm. The two transistor gate drivers 334 may be coupled to two power transistors 336, either directly or via gate drive transformers, which drive the source resonator coils 344 through impedance matching network components 342. The power transistor 336 may be coupled to and powered by the adjustable DC power supply 304, and the adjustable DC power supply 304 may be controlled by the variable bus voltage Vbus. The Vbus controller may be controlled by a control algorithm 328 and may be a component of or integrated into microcontroller 302 or other integrated circuit. Vbus controller 326 may control the voltage output of adjustable DC power supply 304, which may be used to control the power output of the amplifier and the power delivered to resonator coil 344.

The system may include sensing and measurement circuitry, including signal filtering and buffering circuitry 318, 320, which may shape, modify, filter, process, buffer, etc. the signals before they are input to a processor and/or converters, such as analog-to-digital converters (ADCs) 314, 316. The processor and converters, such as ADCs 314, 316, may be integrated into microcontroller 302, or may be separate circuits, which may be coupled to processing core 330. Based on the measured signals, the control algorithm 328 may generate, limit, start, end, control, adjust, or modify the operation of any of the PWM generator 306, the communication controller 332, the Vbus control 326, the source impedance matching controller 338, the filter/buffer elements 318, 320, the converters 314, 316, the resonator coil 344, and may be a component of or integrated into the microcontroller 302, or a separate circuit. The impedance matching network 342 and the resonator coil 344 may include electrically controllable, variable, or tunable components, such as capacitors, switches, inductors, and the like, which may have their component values or operating points adjusted according to signals received from the source impedance matching controller 338, as described herein. The components may be tuned to adjust the operation and characteristics of the resonator, including the power delivered to the resonator, and the power delivered by the resonator, the resonant frequency of the resonator, and the impedance of the resonator. The Q of the resonator, any other coupled system, etc. The resonator may be any type or structure of resonator described herein, including a capacitively-loaded loop resonator, a planar resonator including a magnetic material, or any combination thereof.

The full-bridge system topology shown in fig. 4 may include a processing unit that executes a master control algorithm 328. The processing unit executing the control algorithm 328 may be a microcontroller, an application specific integrated circuit, a field programmable gate array, a processor, a digital signal processor, or the like. The system may include a source/device and/or source/other resonator communication controller 332 coupled to the wireless communication circuit 312. The source/device and/or source/other resonator communication controller 332 may be a component of the same processing unit as that executing the main control algorithm, may be a component or circuitry within the microcontroller 302, may be external to the wireless power transfer module, may be substantially similar to a communication controller used in wired-powered or battery-powered applications, but adapted to include some new or different functionality to enhance or support wireless power transfer.

The system may include a PWM generator 410 having at least two outputs coupled to at least four transistor gate drivers 334 and may be controlled by signals generated in a master control algorithm. The four transistor gate driver 334 may be coupled to four power transistors 336, either directly or via gate drive transformers, which drive the source resonator coil 344 through an impedance matching network component 342. Power transistor 336 may be coupled to and powered by adjustable DC power supply 304, and adjustable DC power supply 304 may be controlled by Vbus controller 306, which may be controlled by a main control algorithm. Vbus controller 326 may control the voltage output of adjustable DC power supply 304, which may be used to control the power output of the amplifier and the power delivered to resonator coil 344.

The system may include sensing and measurement circuitry, including signal filtering and buffering circuitry 318, 320, and differential/single-ended conversion circuitry 402, 404, which may shape, modify, filter, process, buffer, etc. the signals before they are input to a processor and/or converter, such as analog-to-digital converter (ADC) 314, 316. The processor and converters, such as ADCs 314, 316, may be integrated into microcontroller 302, or may be separate circuits, which may be coupled to processing core 330.

Based on the measured signals, the main control algorithm may generate, limit, start, end, control, adjust, or modify the operation of any of PWM generator 410, communication controller 332, Vbus controller 326, source impedance matching controller 338, filter/buffer elements 318, 320, differential/single-ended conversion circuits 402, 404, converters 314, 316, resonator coil 344, and may be a component of or integrated into microcontroller 302, or a separate circuit.

The impedance matching network 342 and the resonator coil 344 may include electrically controllable, variable, or tunable components, such as capacitors, switches, inductors, and the like, which may have their component values or operating points adjusted according to signals received from the source impedance matching controller 338, as described herein. The components may be tuned to achieve tuning of the operation and characteristics of the resonator, including the power delivered to the resonator, and the power delivered by the resonator, the resonant frequency of the resonator, and the impedance of the resonator. The Q of the resonator, any other coupled system, etc. The resonator may be any type or structure of resonator described herein, including a capacitively-loaded loop resonator, a planar resonator including a magnetic material, or any combination thereof.

The impedance matching network may include fixed value components such as capacitors, multifunctional components, and component networks as described herein. The partial impedance matching networks A, B and C may include inductors, capacitors, transformers, and series and parallel combinations of these components, as described herein. In some embodiments, the partial impedance matching networks A, B and C may be empty (short-circuited). In certain embodiments, portion B comprises a series combination of an inductor and a capacitor, and portion C is empty.

The full-bridge topology may allow operation at higher output power levels using the same DC bus voltage as an equivalent half-bridge amplifier. The half-bridge exemplary topology of fig. 3 may provide a single-ended drive signal, while the exemplary full-bridge topology of fig. 4 may provide a differential drive to the source resonator 308. The impedance matching topology and components and resonator structure may be different for the two systems, as described herein.

The exemplary system shown in fig. 3 and 4 may further include a fault detection circuit 340 that may be used to trigger shutdown of a microcontroller in the source amplifier or to change or interrupt operation of the amplifier. This protection circuit may include a high speed comparator to monitor the amplifier return current, the amplifier bus voltage (Vbus) from the DC power supply 304, the voltage across the source resonator 308 and/or optional tuning plate, or any other voltage or current signal that may cause damage to components in the system or may create undesirable operating conditions. The preferred embodiments may depend on potentially undesirable modes of operation associated with different applications. In an alternative embodiment, no protection circuitry may be implemented or populated. In some embodiments, system and component protection may be implemented as part of the main control algorithm and other system monitoring and control circuitry. In an embodiment, the dedicated fault circuit 340 may include an output (not shown) coupled to the main control algorithm 328 that may trigger a system shutdown, a reduction in output power (e.g., a reduction in Vbus), a change to a PWM generator, a change in operating frequency, a change to a tuning element, or any other reasonable operation implemented by the control algorithm 328 to adjust operating point modes, improve system performance, and/or provide protection.

As described herein, a source in a wireless power transfer system may drive the source resonator coil 344 as an error or control signal to a system control loop that is part of a master control algorithm using a measurement of the input impedance of the impedance matching network 342. In an exemplary embodiment, changes in any combination of the three parameters may be used to tune the wireless power source to compensate for changes in environmental conditions, changes in coupling, changes in device power requirements, changes in module, circuit, component, or subsystem performance, increases or decreases in the number of sources, devices, or repeaters in the system, user-initiated changes, and the like. In an exemplary embodiment, variations in amplifier duty cycle, component values of variable electrical components such as variable capacitors and inductors, and DC bus voltage may be used to change the operating point or operating range of a wireless source and improve certain system operating values. The specific details of the control algorithm for different applications may vary depending on the desired system performance and state.

Impedance measurement circuits such as those described herein and shown in fig. 3 and 4 may be implemented using dual channel simultaneous sampling ADCs that may be integrated into the controller chip or may be components of a separate circuit. Simultaneous sampling of the voltage and current signals at the input to the source resonator impedance matching network and/or the source resonator may yield phase and magnitude information of the current and voltage signals, and may be processed using well-known signal processing techniques to yield complex impedance parameters. In some embodiments, it may be sufficient to monitor only the voltage signal or only the current signal.

The impedance measurements described herein may use a direct sampling method, which is relatively simpler than some other known sampling methods. In an embodiment, the measured voltage and current signals may be conditioned, filtered, and scaled by a filter/buffer circuit before being input to the ADC. In embodiments, the filter/buffer circuit may be adapted to operate at multiple signal levels and frequencies, and circuit parameters such as filter shape and width may be adjusted manually, electronically, automatically, by a master control algorithm, or the like, in response to control signals. Exemplary embodiments of the filtering/buffering circuit are shown in fig. 3, 4 and 5.

Fig. 5 shows a more detailed view of exemplary circuit components that may be used in the filtering/buffering circuit. In an embodiment, depending on the type of ADC used in the system design, the single-ended amplifier topology may reduce the complexity of the analog signal measurement path used to characterize the performance of the system, subsystem, module, and/or component by eliminating the need for hardware to convert from differential to single-ended signal format. In other implementations, a differential signal format may be preferred. The implementation shown in fig. 5 is exemplary and should not be construed as the only possible way to implement the functionality described herein. Rather, it should be understood that analog signal paths may use components with different input requirements and thus may have different signal path architectures.

In single-ended and differential amplifier topologies, the input current to the impedance matching network 342 driving the resonator coil 344 may be obtained by measuring the voltage across the capacitor 324, or via some type of current sensor. For the exemplary single-ended amplifier topology in fig. 3, the current may be sensed on the ground return path from the impedance matching network 342. For the exemplary differential power amplifier shown in fig. 4, the input current to the impedance matching network 342 driving the resonator coil 344 may be measured using a differential amplifier across the terminals of the capacitor 324, or via some type of current sensor. In the differential topology of fig. 4, a capacitor 324 may be replicated at the negative output of the source power amplifier.

In both topologies, after a single-ended signal representing the input voltage and current to the source resonator and impedance matching network is obtained, the signal may be filtered 502 to obtain a desired portion of the signal waveform. In an embodiment, the signal may be filtered to obtain a fundamental component of the signal. In embodiments, the type of filtering performed, e.g., low pass, band pass, notch, etc., and the filter circuit topology used, e.g., ellipse, chebyshev, butterworth, etc., may depend on the particular requirements of the system. In some embodiments no filtering is required.

The voltage and current signals may be amplified by an optional amplifier 504. The optional amplifier 504 may be fixed or variable. The gain of the amplifier may be controlled manually, electronically, automatically, in response to a control signal, etc. The gain of the amplifier, etc., may be adjusted in a feedback loop by a main control algorithm in response to the control algorithm. In an embodiment, the required performance specifications for the amplifier may depend on the signal strength and the desired measurement accuracy, and may be different for different application scenarios and control algorithms.

The measured analog signals may have a DC offset 506 added to them, which is needed to bring the signals into the input voltage range of the ADC, which for some systems may be 0 to 0.33V. In some systems, this stage may not be required, depending on the specifications of all of the particular ADCs.

As described above, the efficiency of power transfer between the generator and the power load may be affected by how closely the output impedance of the generator matches the input impedance of the load. In the exemplary system shown in fig. 6A, power can be delivered to the load with as much efficiency as possible when the input impedance of the load 604 is equal to the complex conjugate of the internal impedance of the generator or power amplifier 602. Designing the generator or load impedance to achieve high and/or maximum power transfer efficiency may be referred to as "impedance matching". Impedance matching may be performed by inserting an appropriate network or group of elements, such as capacitors, resistors, inductors, transformers, switches, etc., to form an impedance matching network 606 between the generator 602 and the power load 604 shown in fig. 6B. In other embodiments, mechanical adjustments and changes in component positioning may be used to achieve impedance matching. As described above for varying loads, the impedance matching network 606 may include variable components that are dynamically adjustable to ensure that the impedance at the generator end towards the load and the characteristic impedance of the generator remain substantially complex conjugates of each other, even under dynamic environmental and operating conditions. In embodiments, dynamic impedance matching may be accomplished by tuning the duty cycle and/or phase and/or frequency of the drive signal of the generator, or by tuning physical components within the generator, such as capacitors, as shown in fig. 6C. This tuning mechanism is advantageous because it may allow impedance matching between the generator 608 and the load without the use of a tunable impedance matching network, or with a simplified tunable impedance matching network 606, such as a network with fewer tunable components. In embodiments, tuning to the duty cycle and/or frequency and/or phase of the drive signal of the generator may produce a dynamic impedance matching system, with extended tuning range or accuracy, with higher power, voltage and/or current performance, with faster electronic control, with fewer external components, and the like. The impedance matching methods, architectures, algorithms, protocols, circuits, measurements, controls, etc. described below are useful in systems where the generator drives a high Q magnetic resonator, or in high Q wireless power transfer systems as described herein. In a wireless power transfer system, the generator may be a power amplifier driving a resonator, sometimes referred to as a source resonator, which may be a load to the power amplifier. In wireless power applications, impedance matching between the power amplifier and the resonator load is preferably controlled to control the efficiency of power transfer from the power amplifier to the resonator. Impedance matching may be accomplished, or partially accomplished, by tuning or adjusting the duty cycle and/or phase and/or frequency of the drive signal of the power amplifier driving the resonator.

Efficiency of switching amplifier

Switching amplifiers, such as class D, E, F amplifiers and the like, or any combination thereof, deliver power to a load with maximum efficiency when little power is dissipated across the switching elements of the amplifier. This operating condition can be achieved by designing the system such that the most critical switching operations (i.e. those most likely to cause switching losses) are performed when either or both of the voltage across the switching element and the current through the switching element are almost 0. These conditions may be referred to as Zero Voltage Switching (ZVS) and Zero Current Switching (ZCS) conditions, respectively. When the amplifier operates at ZVS and/or ZCS, the voltage across or current through the switching elements is zero, so that no power is dissipated in the switches. Since the switching amplifier can convert DC (or very low frequency AC) power to AC power of a particular frequency or range of frequencies, a filter can be introduced in front of the load to avoid unwanted harmonics from reaching the load and being dissipated there, where the harmonics are generated by the switching process. In an embodiment, the switching amplifier may be designed to have a quality factor (e.g., Q) when connected to>5) And a specific impedanceResulting in simultaneous ZVS and ZCS, operating at maximum power conversion efficiency. We will turn z_o＝R_o-jX_oIs defined as the characteristic impedance of the amplifier such that achieving maximum power transfer efficiency is equivalent to matching the resonant load impedance to the characteristic impedance of the amplifier.

In a switching amplifier, the switching frequency f of the switching element_switchWherein f is_switch= ω/2 π, and duration of the on state of the switching elementThe duty cycle dc is the same for all switching elements of the amplifier. In this specification we will use the term "class D" to denote class D and class DE amplifiers, that is to say having dc<Switch amplifier of = 50%.

The value of the characteristic impedance of the amplifier may depend on the operating frequency, the amplifier topology and the switching order of the switching elements. In some embodiments, the switching amplifier may be a half-bridge topology, and in some embodiments a full-bridge topology. In some embodiments, the switching amplifier may be class D, and in some embodiments, class E. In any of the above embodiments, the characteristic impedance of the switching amplifier has a form, assuming symmetry of the elements of the bridge

R_O=F_R(dc)/ωC_a,X_O=F_X(dc)/ωC_a， （1）

Where dc is the duty cycle of the on-state of the switching element, function F_R(dc) and F_X(dc) is plotted in fig. 7 (both for class D and E), ω is the frequency of the switching element, C_a=n_aC_switcWherein, C_switcIs the capacitance across each switch, including the transistor output capacitance and possibly an external capacitor arranged in parallel with the switch, while for the full bridge n_aFor half bridge n =1_aAnd (2). For class D, analytical expressions can also be written

F_R(dc)=sin²u/π，F_X(dc)＝(u-sinu*cosu）/π, (2)

Where u = pi (1-2 dc), indicating that the characteristic impedance level of the class D amplifier decreases as the duty cycle dc increases towards 50%. For class D amplifier operation with dc =50%, there is practically no output capacitance (C) only at the switching element(s)_a= 0), and the load is actually resonant (X)_O= 0), and R_OIt may be that in any case, it is only possible to implement ZVS and ZCS.

Impedance matching network

In application, the driven load may have an impedance that is very different from the characteristic impedance of the external driving circuit to which it is connected. Also, the driven load may not be a resonant network. An Impedance Matching Network (IMN) is a circuit network, as shown in fig. 6B, that can be connected in front of a load in order to adjust the impedance seen at the input of the network consisting of the IMN circuit and the load. IMN circuits can typically achieve this adjustment by producing resonances close to the drive frequency. Since this IMN circuit achieves all the conditions (resonance and impedance matching-ZVS and ZCS for switching amplifiers) needed to maximize the efficiency of power transfer from the generator to the load, in embodiments, an IMN circuit may be used between the driver circuit and the load.

For the arrangement shown in fig. 6B, the input impedance of the network consisting of the Impedance Matching Network (IMN) circuit and the load (denoted as IMN + load from here on) is made Z_l=R_l(ω)+jX_l(ω). The network has a characteristic impedance z_o＝R_o-jX_oThen the impedance matching condition of the external circuit is R_l(ω)=R_O，X_l(ω)=X_O。

Method for tunable impedance matching of variable loads

In embodiments where the load is variable, impedance matching between the load and an external drive circuit, such as a linear or switching power amplifier, may be achieved by using an adjustable/tuning component in the IMN circuit, which may be adjusted to match the varying load to a fixed characteristic impedance Z of the external circuit_oMatch (fig. 6B). In order to match the real and imaginary parts of the impedance, two tunable/variable components are required in the IMN circuit.

In an embodiment, the load may be inductive (e.g. a resonator coil) with an impedance R + j ω L, so the two tunable elements in the IMN circuit may be two tunable capacitance networks, or one tunable capacitance network and one tunable mutual inductance network.

At the negativeIn variable-load embodiments, impedance matching between a load and a driver circuit, such as a linear or switching power amplifier, may be achieved by using adjustable/tunable components or parameters in the amplifier circuit, which may be adjusted to match the characteristic impedance Z of the amplifier_oMatched to the varying (due to load variations) network input impedance, the network consists of an IMN circuit and a load (IMN + load), wherein the IMN circuit is also tunable (fig. 6C). A total of two tunable/variable elements or parameters are required in the amplifier and IMN circuits in order to match the real and imaginary parts of the impedance. The disclosed impedance matching methods may reduce the number of tunable/variable elements required in the IMN circuitry, or even eliminate the need for tunable/variable elements in the IMN circuitry altogether. In some instances, one tunable element in the power amplifier and one tunable element in the IMN circuitry may be used. In some instances, two tunable elements in the power amplifier may be used instead of the tunable elements in the IMN circuitry.

In an embodiment, the tunable element or parameter in the power amplifier may be a drive signal frequency, amplitude, phase, waveform, duty cycle, etc. applied to a transistor, switch, diode, etc.

In an embodiment, the power amplifier with tunable characteristic impedance may be a class D, E, F tunable switching amplifier or any combination thereof. Combining equations (1) and (2), the impedance matching conditions for this network are:

R_l(ω)=F_R(dc)/ωC_a，X_l(ω)=F_X(dc)/ωC_a， （3）

in some examples of tunable switching amplifiers, one tunable element may be a capacitor C_aWhich can be tuned by tuning an external capacitor arranged in parallel with the switching element.

In some examples of tunable switching amplifiers, one tunable element may be the duty cycle dc of the on-state of the switching elements of the amplifier. Output power control is achieved by adjusting the duty cycle dc by means of Pulse Width Modulation (PWM) has been used in switching amplifiers. In this specification we disclose that PWM can also be used to achieve impedance matching, i.e. to satisfy equation (3), thereby maximizing amplifier efficiency.

In some examples of tunable switching amplifiers, one tunable element may be the switching frequency, which may also be the drive frequency of the IMN + load network, and may be designed to be substantially close to the resonant frequency of the IMN + load network. Tuning the switching frequency can change the characteristic impedance of the amplifier and the impedance of the IMN + load network. The switching frequency of the amplifier may be appropriately tuned along with one or more tunable parameters so as to satisfy equation (3).

The benefit of tuning the duty cycle and/or drive frequency of the amplifier for dynamic impedance matching is that these parameters can be tuned electronically, quickly, and over a wide range. In contrast, for example, tunable capacitors that can withstand large voltages and have a sufficiently large tunable range and quality factor are expensive, slow, or unavailable to the necessary component specifications.

Examples of methods for tunable impedance matching of variable loads

A simplified circuit diagram showing the circuit level structure of a class D power amplifier 802, an impedance matching network 804 and an inductive load 806 is shown in fig. 8. The circuit diagram shows the basic components of the system with a switching amplifier 804 comprising a power supply 810, a switching element 808 and a capacitor. The impedance matching network 804, including the inductor and capacitor, and the load 806 are modeled as an inductor and resistor.

An exemplary embodiment of the inventive tuning scheme comprises a half bridge class D amplifier operating at a switching frequency f and driving a low loss inductive element R + j ω L via IMN, as shown in fig. 8.

In certain embodiments, L' is tunable. Can be made by a variable tap on the inductor or by connecting a tunable capacitor in series or in parallel with the inductorThe connection is taken to tune L'. In certain embodiments, C_aIs tunable. For half-bridge topologies, one or two capacitors C can be changed_switcTo tune C_aSince it is simply the parallel sum of these capacitors that is relevant to amplifier operation. For a full-bridge topology, any one, two, three or all of the capacitors C can be changed_switcTo tune C_aSince only their combination (the series sum of the two parallel sums associated with the two half bridges of the bridge) is relevant for the amplifier operation.

In some embodiments of tunable impedance matching, two components of the IMN are tunable. In certain embodiments, L' and C₂Is tunable. Thus, fig. 9 shows the values of the two tunable components required to achieve impedance matching as a function of R and L for a change in the inductive element, and the associated change in the output power of the amplifier (at a given DC bus voltage), where f =250kHz, DC =40%, C_a=640pF，C₁=10 nF. Since the IMN is adjusted up to the fixed characteristic impedance of the amplifier, the output power is constant as the inductive element changes.

In some embodiments of tunable impedance matching, the elements of the switching amplifier may also be tuned. In some embodiments, an IMN capacitor C may be included₂Tuning capacitors C together_a. Thus, fig. 10 shows the values of the two tunable components required to achieve impedance matching as a function of R and L for a change in the inductive element, and the associated change in the output power of the amplifier (at a given DC bus voltage), where f =250kHz, DC =40%, C₁=10nF, ω L ═ 1000 Ω. From FIG. 10, it can be inferred that tuning C is primarily required in response to changes in L₂And as R increases, the output power decreases.

In some embodiments of tunable impedance matching, an IMN capacitor C may be included along with₂The duty cycles dc are tuned together. Thus, fig. 11 shows the values of the two tunable parameters required to achieve impedance matching, and the output power of the amplifier (at a given output power) as a function of R and L for a change in the inductive elementDC bus voltage), where f =250kHz, C_a=640pF，C₁=10nF, ω L ═ 1000 Ω. From FIG. 11, it can be inferred that tuning C is primarily required in response to changes in L₂And as R increases, the output power decreases.

In some embodiments of tunable impedance matching, the capacitance C may be tuned along with the IMN inductor L_a. Thus, fig. 11A shows the values of the two tunable components required to achieve impedance matching as a function of R for a change in the inductive element, and the associated change in the output power of the amplifier (at a given DC bus voltage), where f =250kHz, DC =40%, C₁=10nF，C₂=7.5 nF. As can be inferred from fig. 11A, as R increases, the output power decreases.

In some embodiments of tunable impedance matching, the duty cycle dc may be tuned along with the IMN inductor L'. Thus, fig. 11B shows the values of the two tunable parameters required to achieve impedance matching as a function of R for a change in the inductive element, where f =250kHz, C is a function of R for a change in the inductive element, and the associated change in the output power of the amplifier (at a given DC bus voltage)_a=640pF，C₁=10nF，C₂=7.5 nF. As can be inferred from fig. 11B, and as R increases, the output power decreases.

In some embodiments of tunable impedance matching, only the elements of the switching amplifier are tunable, and none of the elements in the IMN are tunable. In some embodiments, a capacitor C may be included_aThe duty cycles dc are tuned together. Thus, fig. 11C shows the values of two tunable parameters required to achieve impedance matching as a function of R for a change in the inductive element, where f =250kHz, C, and the associated change in the output power of the amplifier (at a given DC bus voltage), where f =250kHz₁=10nF，C₂=7.5nF, ω L ═ 1000 Ω. From fig. 11C, it can be inferred that the output power is a non-monotonic function of R. These embodiments enable dynamic impedance matching when the variation in L (and thus the resonant frequency) is moderate.

At a certain pointIn some embodiments, as explained earlier, when L varies greatly, dynamic impedance matching to fixed elements in the IMN can be achieved by changing the drive frequency of the external frequency f (e.g., the switching frequency of a switching amplifier) so that it follows the changing resonant frequency of the resonator. Using the switching frequency f and the switching duty cycle dc as two variable parameters, complete impedance matching can be achieved as R and L vary without any variable components. Thus, fig. 12 shows the values of two tunable parameters required to achieve impedance matching as a function of R and L for a change in the inductive element, and the associated change in the output power of the amplifier (at a given DC bus voltage), where C_a=640pF，C₁=10nF，C₂=7.5nF, L' ═ 637 μ H. From fig. 12 it can be concluded that the tuning frequency f is mainly needed in response to changes in L, as explained earlier.

Tunable impedance matching for systems for wireless power transfer

In wireless power transfer applications, the low-loss inductive element may be a coil of a source resonator coupled to one or more device resonators or other resonators, such as a transponder resonator. The impedance R + j ω L of the inductive element may comprise the reflected impedance of the other resonator on the coil of the source resonator. The R and L of the inductive element may change due to external disturbances in the vicinity of the source resonator and/or thermal drift of other resonators or components. Changes in R and L of the inductive elements may also occur during normal use of the wireless power transfer system due to relative motion of the device and other resonators with respect to the source. Relative movement of these devices and other resonators relative to the source, or relative movement or position of other sources, can result in changing the device-to-source coupling (and thus the reflected impedance). Furthermore, variations in R and L of the inductive elements may also occur during normal use of the wireless power transfer system due to variations in other coupled resonators, such as variations in the power draw of their loads. All the methods and embodiments disclosed so far are equally applicable in this case in order to achieve a dynamic impedance matching of this inductive element to the external circuit driving it.

To illustrate the presently disclosed dynamic impedance matching method for a wireless power transfer system, consider that the source resonator comprises a low-loss source coil inductively coupled to the device coil of the device resonator driving a resistive load.

In some embodiments, dynamic impedance matching may be implemented at the source circuit. In some embodiments, dynamic impedance matching may also be implemented in the device circuitry. When a complete impedance match is obtained (at the source and the device), the effective resistance of the source inductive element (i.e. the resistance R of the source coil)_sPlus reflected impedance from the device) is(similarly, the effective resistance of the inductive element of the device isWherein R is_dIs the resistance of the device coil). Due to dynamic variation of mutual inductance between coils in motionIs dynamically changed. Therefore, when the source and the device are dynamically tuned at the same time, the change in the mutual inductance is regarded as a change in the source inductive element resistance R from the source circuit side. Note that in such a variation, the resonant frequency of the resonator does not substantially change, as L may not change. Thus, all of the methods and examples presented for dynamic impedance matching may be used for the source circuit of a wireless power transfer system.

It should be noted that since the resistance R represents the source and device coil-to-source coil reflected impedance, in fig. 9-12, the associated wireless power transfer efficiency increases as R increases due to increasing U. In some embodiments, substantially constant power may be required at a load driven by the device circuitry. To achieve a constant power level delivered to the device, the required output power of the source circuit needs to decrease as U increases. If dynamic impedance matching is achieved by tuning certain amplifier parameters, the output power of the amplifier can be changed accordingly. In some embodiments, the automatic change in output power preferably decreases monotonically with R so that it matches a constant device power requirement. In embodiments where the output power level is reached by adjusting the DC drive voltage of the generator, using an impedance matched combination of tunable parameters, which results in a monotonic decrease in the output power vs.r, means that a constant power can be maintained at the power load of the device with only a modest adjustment of the DC drive voltage. In embodiments where the "knob" adjusting the output power stage is the duty cycle dc or phase of a component within a switching amplifier or impedance matching network, using an impedance matching set of tunable parameters means that constant power can be maintained at the power load of the device with only a modest adjustment of this power "knob", where the impedance matching combination of tunable parameters results in a monotonic decrease in output power vs.

In the examples of FIGS. 9-12, if R is_s=0.19 Ω, the range R =0.2-2 Ω corresponds approximately to U_sdAnd (5) = 0.3-10.5. For these values, we show in dashed lines in fig. 14 the output power (normalized as DC voltage squared) required to maintain a constant power level at the load when both source and device are dynamically impedance matched. A similar trend between the solid and dashed lines explains why a set of tunable parameters with this variation in output power is preferred.

In some embodiments, dynamic impedance matching may be implemented at the source circuit, while impedance matching may not be implemented or only partially implemented at the device circuit. As the mutual inductance between the source and the device coil changes, the changing reflected impedance from device to source may cause a change in the effective resistance R and the effective inductance L of the source inductive element. The methods proposed so far for dynamic impedance matching are applicable and can be used for tunable source circuits of wireless power transfer systems.

For example, consider the circuit of fig. 14, where f =250kHz, C_a=640pF，R_s=0.19Ω，L_s＝100μH，C_1s=10nF，ωL’＝1000Ω，R_d=0.3Ω，L_d＝40μH，C_1d=87.5nF，C_2d=13nF，ωL’_d＝400Ω，Z_l=50 Ω, where s and d denote the source and device resonators, respectively, and the system is in U_sdAnd =3 matching. Tuning the duty cycle dc of a switching amplifier and a capacitor C_2sDynamic impedance matching of the source may be used because the non-tunable device moves relative to the source, changing the mutual inductance M between the source and the device. In fig. 14 we show the required values of the tuning parameters, together with the output power per DC voltage of the amplifier. The dashed line again indicates the output power of the amplifier, which is needed so that the power at the load is a constant value.

In some embodiments, for a system of wireless power transfer between a source and one or more devices, tuning the drive frequency f of the source drive circuit may still be used to achieve dynamic impedance matching at the source. As explained earlier, this approach achieves full dynamic impedance matching of the source, even when the source inductance L is present_sAnd thus the source resonant frequency, is also changed. For efficient power transfer from source to device, the device resonant frequency must be tuned to follow the changes in the matched drive and source resonant frequencies. Tuning device capacitance when there is a change in the resonant frequency of the source or device resonator (e.g., in the embodiment of FIG. 13, C_1dOr C_2d) Is necessary. Indeed, in a wireless power transfer system with multiple sources and devices, tuning the drive frequency alleviates the need to tune only one source-object resonant frequency, but all objects remaining require a mechanism (e.g., tunable capacitance) to tune their resonant frequency to match the drive frequency.

Resonator thermal management

In wireless energy transfer systems, a portion of the energy lost during inefficient transfer is dissipated as heat. Energy may be dissipated in the resonator component itself. Even high Q conductors and components, for example, have some loss or resistance, and these conductors and components become hot when current and/or electromagnetic fields flow through them. Energy may be dissipated in materials and objects surrounding the resonator. For example, eddy currents that are dissipated in a poor conductor or dielectric around or near the resonator may heat these objects. In addition to affecting the material properties of these objects, this heat can be transferred to the resonator component by conduction, radiation or convection processes. Any of these heating effects may affect the resonator Q, impedance, frequency, etc., and thus the performance of the wireless energy transfer system.

In a resonator comprising a block or core of magnetic material, heat may be generated in the magnetic material due to hysteresis losses and resistive losses caused by induced eddy currents. Both effects depend on the magnetic flux density in the material, and both can generate a significant amount of heat, especially in areas where the magnetic flux density or eddy currents are concentrated or localized. In addition to magnetic flux density, the frequency of the oscillating magnetic field, the magnetic material composition and losses, the environment or operating temperature of the magnetic material can all affect how hysteresis and resistive losses heat the material.

In embodiments, the properties of the magnetic material, such as the type of material, the size of the block, etc., and the magnetic field parameters may be selected for a particular operating power level and environment to minimize heating of the magnetic material. In certain embodiments, the change, crack or defect in the block of magnetic material may increase the loss and heating of the magnetic material in wireless power transfer applications.

For magnetic blocks having defects, or consisting of tiles and sheets of magnetic material of smaller size arranged in larger cells, the losses in the blocks may be non-uniform and may be concentrated in areas where there is non-uniformity or relatively narrow gaps between adjacent tiles or sheets of magnetic material. For example, if an irregular gap exists in a magnetic mass of material, the effective reluctance of the plurality of flux paths through the material is substantially irregular, and the magnetic field may be more concentrated in the portion of the mass where the reluctance is lowest. In some cases, the effective reluctance may be lowest where the gap between the tiles or sheets is narrowest or where the density of defects is lowest. Because the magnetic material directs the magnetic field, the magnetic flux density is not substantially uniform across the block, but is concentrated in areas that provide relatively low reluctance. Irregular concentrations of magnetic fields within the bulk of the magnetic material are undesirable because they can lead to uneven losses and heat dissipation in the material.

For example, consider a magnetic resonator that includes a conductor 1506 wrapped around a block of magnetic material that is made up of two individual bricks 1502, 1504 of joined magnetic material such that they form a seam 1508 that is perpendicular to the axis of the loop of the conductor 1506, as shown in fig. 15. The irregular gap in the seam 1508 between the blocks of magnetic material 1502 and 1504 may force the magnetic field 1512 (schematically represented by dashed magnetic field lines) in the resonator to be concentrated in a sub-region 1510 of the cross-section of the magnetic material. Since the magnetic field will follow a path of least reluctance, a path that includes an air gap between two pieces of magnetic material can create a path of substantially higher reluctance than a path that traverses the width of the magnetic material at the point where the pieces of magnetic material contact or have a smaller air gap. The magnetic flux density therefore preferably flows through a relatively small intersection region of the magnetic material, resulting in a high concentration of magnetic flux in this small region 1510.

In many magnetic materials of interest, more of the non-uniform flux density distributions have higher total losses. Furthermore, a more uneven flux density distribution may lead to saturation of the material and local heating of the areas where the magnetic flux is concentrated. Local heating can change the properties of the magnetic material, in some cases exacerbating losses. For example, in the relevant operating conditions of certain materials, hysteresis losses and resistance losses increase with temperature. If heating the material increases material loss, resulting in more heat generation, the material temperature can continue to increase and even run away if corrective action is not taken. In some instances, temperatures may reach 100 ℃ or higher and may degrade the properties of the magnetic material and the performance of the wireless power transfer. In some instances, the magnetic material may be damaged, or surrounding electronic components, packaging, and/or housings may be damaged due to overheating.

In an embodiment, the variations or irregularities between the tiles or sheets of the block of magnetic material may be achieved by matching, polishing, grinding, etc. the edges of the tiles or sheets to ensure a tight fit between the tiles of magnetic material, which provides a substantially more uniform magnetic reluctance across the entire cross-section of the block of magnetic material. In an embodiment, blocks of magnetic material may require modules for providing pressure between the tiles to ensure that the tiles are pressed together without gaps. In an embodiment, an adhesive may be used between the tiles to ensure that they remain in intimate contact.

In an embodiment, the irregular spacing of adjacent tiles of magnetic material may be reduced by adding a carefully considered gap between adjacent tiles of magnetic material. In embodiments, carefully considered gaps may be used as spacers to ensure uniform or regular separation between the tiles or sheets of magnetic material. Careful consideration of the gaps in the flexible material may also reduce irregularities in the spacing due to movement or vibration of the tiles. In an embodiment, the edges of adjacent tiles of magnetic material may be taped, soaked, coated, etc. with electrical insulation to avoid eddy currents flowing through the reduced block cross-sectional area, thereby reducing eddy current losses in the material. In an embodiment, the splitter may be integrated into the resonator package. The spacers may provide a spacing of 1mm or less.

In an embodiment, the mechanical properties of the spacers between the tiles may be selected so as to improve the resistance of the overall structure to mechanical effects, such as variations in the size and/or shape of the tiles resulting from intrinsic effects (e.g. magnetostriction \ thermal expansion, etc.), as well as external shocks and vibrations. For example, the spacers may have a desired amount of mechanical elasticity, accommodate expansion and/or contraction of the individual tiles, and may help reduce stress on the tiles when the tiles are subjected to mechanical vibrations, thereby helping to reduce the occurrence of cracks and other defects in the magnetic material.

In an embodiment, the single tiles comprising blocks of magnetic material are preferably arranged such that the number of seams or gaps between the tiles perpendicular to the dipole moment of the resonator is minimized. In an embodiment, the tiles of magnetic material are preferably arranged and oriented such that the gap between the tiles perpendicular to the axis formed by the conductor loop including the resonator is minimal.

For example, consider the resonator structure shown in fig. 16. The resonator includes a conductor 1604 wrapped around a magnetic material that includes 6 separate monolithic tiles 1602 arranged in a 3 by 2 array. This arrangement of tiles results in two tile seams 1606, 1608 when traversing the piece of magnetic material in one direction, and only one tile seam 1610 when traversing the piece of magnetic material in a perpendicular direction. In an embodiment, conductor wire 1604 is preferably wrapped around the block of magnetic material such that the dipole moment of the resonator is perpendicular to the smallest number of tile seams. The inventors have observed that relatively little heat is induced around seams 1606, 1608 that are parallel to the dipole moment of the resonator. The seams and gaps that are perpendicular to the dipole moment of the resonator may also be referred to as critical seams or critical seam regions. It is also desirable to electrically insulate the gaps (e.g., 1606, 1608) parallel to the dipole moments of the resonators to reduce eddy current losses. Uneven contact between tiles divided by such parallel gaps can result in eddy currents flowing through narrow contact points, causing large losses at such points.

In an embodiment, irregularities in the spacing may be tolerated by proper cooling of the critical seam region to avoid local degradation of material properties when the magnetic material is heated. Maintaining the temperature of the magnetic material below the critical temperature may avoid runaway effects caused by sufficiently high temperatures. With proper cooling of the critical joint area, wireless energy transfer performance is satisfactory regardless of additional losses or heating effects due to irregular spacing, cracks or gaps between the tiles.

The effective heat dissipation of resonator structures to avoid local overheating of magnetic materials poses several challenges. The metallic materials typically used for heat sinks and heat conduction can come into contact with the magnetic field used by the resonator for wireless energy transfer and affect the performance of the system. Their location, size, orientation, and use should be designed so as to be, in the presence of these heat sink materials, not to be, however, below the perturbation Q of the resonator. In addition, due to the relatively criss-cross thermal conductivity of magnetic materials such as ferrites, a relatively large contact area may be required between the heat sink and the magnetic material to provide adequate cooling, which may require a large amount of lossy material to be placed close to the magnetic resonator.

In an embodiment, proper cooling of the resonator may be achieved by strategically placing thermally conductive materials to minimize the impact on wireless energy transfer performance. In an embodiment, a strip of thermally conductive material may be placed between the loops of conductor wire and in thermal contact with the block of magnetic material.

One exemplary embodiment of a resonator having a strip of thermally conductive material is shown in fig. 17. Figure 17A shows a resonator structure without conductive strips, with a block of magnetic material, including small bricks of magnetic material forming gaps or seams. Thermally conductive strip 1708 material may be placed between the loops of conductor 1702 in thermal contact with the volume 1704 of magnetic material, as shown in FIGS. 17B and 17C. In order to minimize the influence of the strips on the resonator parameters, it is preferred in some embodiments to arrange the strips parallel to the conductor loops or perpendicular to the dipole moment of the resonator. The strips of conductor may be arranged to cover as large or as large seams or gaps between tiles as possible, in particular between tiles perpendicular to the dipole moment of the resonator.

In an embodiment, the thermally conductive material may include copper, aluminum, brass, thermal epoxy, paste, pads, etc., and may be any material having a thermal conductivity of at least the magnetic material of the resonator (5W/(K-m) for certain commercial ferrite materials). In embodiments where the thermally conductive material is also electrically conductive, the material may require a layer or coating of electrical insulation to avoid shorting or direct electrical contact with the resonator's magnetic material loops.

In an embodiment, a strip of thermally conductive material may be used to conduct heat from the resonator structure to a structure or medium, which may safely dissipate the heat. In embodiments, the strip of thermally conductive material may be connected to a heat sink, such as a large flat plate on the conductor strip, which may dissipate thermal energy using passive or forced convection, radiation, or conduction to the environment. In embodiments, the system may include any number of active cooling systems external or internal to the resonator structure that may dissipate thermal energy from the thermally conductive strip, and may include liquid cooling systems, compressed air systems, and the like. For example, the thermally conductive strip may be hollow or include channels for coolant, and coolant may be pumped or pressurized through the channels to cool the magnetic material. In an embodiment, a field deflector constructed of a good electrical conductor (e.g., copper, silver, aluminum, etc.) may double as part of a heat sink. Adding a thermally and electrically conductive strip to the space between the magnetic material and the field deflector can have a marginal effect on the perturbation Q, since the electromagnetic field in this space is usually suppressed due to the presence of the field deflector. Such conductive strips may be thermally connected to the magnetic material and the field deflector to make the temperature distribution in the different strips more uniform.

In an embodiment, the thermally conductive strips are spaced apart to allow at least one conductor loop to be wrapped around the magnetic material. In an embodiment, the strip of thermally conductive material may be located only at gaps or seams of the magnetic material. In other embodiments, the strip may be positioned to contact the magnetic material over substantially its entire length. The strips may be distributed to match the flux density within the magnetic material. The region of magnetic material under normal operation of the resonator may have a higher magnetic flux density and may have a higher density of contact with the thermally conductive strip. For example, in the embodiment shown in fig. 17A, the highest magnetic flux density in the magnetic material may be observed towards the center of the block of magnetic material, and the lower density may be towards the ends of the block in the direction of the dipole moment of the resonator.

To illustrate how the use of thermal conductive strips helps reduce the overall temperature in the magnetic material, and the temperature at potential hot spots, the inventors performed finite element simulations similar to the resonator structure shown in fig. 17C. A structure was simulated, operating at a frequency of 235kHz and comprising a block of EPCOS N95 magnetic material, measuring 30cm x30cm x5mm, excited by 10 turns of litz wire each carrying a peak current of 10A (symmetrically arranged at 15mm, 40mm, 55mm, 90mm and 105mm from the plane of symmetry of the structure) and thermally connected to a field deflector of 50cm x4mm by means of three 3x3/4x 1' hollow square tubes of aluminium (alloy 6063) (wall thickness 1/8 "), the central axes of which are arranged at-75 mm, 0mm and +75 from the plane of symmetry of the structure. The Q is 1400 (compared to 1710 for the same structure without the hollow tube) due to the field deflector and the hollow tube conductance disturbance. The power dissipated in the shield and tube was calculated to be 35.6W, while the power dissipated in the magnetic material was 58.3W. Assuming that the structure is cooled by air convection and radiation, and the ambient temperature is 24 ℃, the maximum temperature in the structure is 85 ℃ (a point in the magnetic material approximately half way between the hollow tubes), while the temperature in the portion of the magnetic material contacting the hollow tubes is about 68 ℃. By comparison, for the same excitation current at a peak of 40W, the same resonator without the thermally conductive hollow tube dissipates 62.0W and the maximum temperature in the magnetic material is found to be 111 ℃.

The advantages of the conductive strips are even more pronounced if we introduce defects in a portion of the magnetic material, which is in good thermal contact with the tube. An air gap 10cm long and 0.5mm apart in the center of the magnetic material, and oriented perpendicular to the dipole moment, increases the power dissipated in the magnetic material to 69.9W (11.6W increased over the previously discussed defect-free example where the high concentration is near the gap), but the conductive strip tube ensures that the maximum temperature in the magnetic material is only increased relatively moderately by 11c to 96 c. In contrast, the same defect without the conductive tube results in a maximum temperature of 161 ℃ in the vicinity of the defect. Other cooling solutions besides convection and radiation, such as thermally connecting the conductive pipe bodies with a large thermal mass or actively cooling them, can produce even lower operating temperatures for the resonator at the same current level.

In an embodiment, the thermally conductive strips of material may be positioned in areas where cracks are most likely to occur, which may result in irregular gaps in the magnetic material. Such areas may be areas of high stress or strain on the material, or areas of poor support or support from the resonator package. Strategically placing the thermally conductive strips can ensure that the temperature of the magnetic material remains below its critical temperature despite the presence of cracks or irregular gaps in the magnetic material. The critical temperature may be defined as the curie temperature of the magnetic material, or any temperature at which the properties of the resonator degrade beyond desired performance parameters.

In an embodiment, the heat dissipation structure may provide mechanical support for the magnetic material. In embodiments, the heat dissipation structure may be designed to have a desired amount of mechanical elasticity (e.g., by using epoxy, thermal pads, etc., which have suitable mechanical properties to thermally connect the different elements of the structure) so as to provide the resonator with a greater tolerance to variations in the inherent dimensions of its elements (due to thermal expansion, magnetostriction, etc.) as well as external impacts and initiatives, and to avoid the formation of cracks and other defects.

In embodiments where the resonator comprises a winding wound vertically around the magnetic material, the strip of conductive material may be adapted to obtain thermal contact with the magnetic material in an area bounded by two vertically adjacent sets of loops. In an embodiment, the strip may comprise suitable indentations to fit around the conductor of at least one orthogonal winding while being in thermal contact with the magnetic material at least one point. In an embodiment, the magnetic material may be in thermal contact with a plurality of thermally conductive blocks placed between adjacent loops. The thermally conductive blocks may in turn be thermally connected to each other by means of a good thermal conductor and/or a heat sink.

Throughout this specification, although the term thermally conductive strip of material is used as an illustrative example of a shape of material, it will be understood by those skilled in the art that any shape and profile may be substituted without departing from the spirit of the invention. Square, oval, bar, dot, elongated, etc. are within the spirit of the invention.

Communication in a wireless energy transfer system

Wireless energy transfer systems may require a validation step to ensure that energy is transferred between designated resonators. For example, in a wireless energy transfer system, the source resonator, the device resonator, and the repeater resonator need not be in physical contact with each other for the purpose of exchanging energy, but depending on the size and number of resonators in the system, the resonators may be separated from each other by a distance of centimeters or meters. In some configurations, multiple resonators are capable of generating or receiving power, but only two or some of these resonators are designated resonators.

Communication of information between resonators in a wireless energy transfer system may be used to designate the resonators. Communication of information between resonators may be accomplished using in-band or out-of-band communications or communication channels. If at least a portion of the magnetic resonators used to exchange power are also used to exchange information and the carrier frequency of the information exchange is close to the resonant frequency used for the power exchange, we refer to the communication as in-band. Any other type of communication between magnetic resonators is referred to as out-of-band. The out-of-band communication channel may use an antenna and a signal transmission protocol that is different from the energy transfer resonator and the magnetic field. The out-of-band communication channel may use or be based on bluetooth, WiFi, Zigbee, NFC technology, etc.

Communication between resonators may be used to coordinate wireless energy transfer, or adjust parameters of a wireless energy transfer system, identify and authenticate available power sources and devices, optimize efficiency, power transfer, etc., track and account for energy preferences, usage, etc., as well as monitor system performance, battery condition, vehicle health, external objects, also known as foreign objects, etc. The method for specifying and validating resonators for energy transfer may be different when in-band and out-of-band communication channels are used, as the distance through which communication signals are exchanged using out-of-band techniques may greatly exceed the distance through which power signals are exchanged. Furthermore, the bandwidth of the out-of-band communication signal may be greater than the in-band communication signal. This difference in communication range and performance may affect the coordination of the wireless energy transfer system. For example, the number of resonators that can be handled using out-of-band communication can be very large, with communication resonators being located far apart, which can be much further than they can efficiently exchange energy.

In some embodiments, all signal transmission and communication may be performed using an in-band communication channel, and the signal may be modulated on the field for energy transfer. In other embodiments, in-band communication may use substantially the same spectrum as used for energy transfer, but not transfer substantial energy while communicating. If separate or multiple authentication steps are problematic, it is preferable to use only the in-band communication channel, since the range of communication can be limited to the same range as the power exchange, or since the information arrives as a modulation on the power signal itself. But in some embodiments a separate out-of-band communication channel is more desirable. For example, out-of-band communication channels are cheaper to implement and can support higher data rates. The out-of-band communication channel may support more distant communication, allowing resonator discovery and power system mapping. The out-of-band communication channel may be operated regardless of whether power transfer is in progress, and may be performed without interruption of power transfer.

An exemplary embodiment of a wireless energy system is shown in fig. 18. This exemplary embodiment includes two device resonators 1802, 1816, each having an out-of-band communication module 1804, 1818, respectively, and two source resonators 1806, 1810, each having its own out-of-band communication module 1808, 1812, respectively. The system may use an out-of-band communication channel to regulate and coordinate energy delivery. The communication channel may be used to discover or find nearby resonators, initiate power transfer, and communicate adjustments in operating parameters, such as power output, impedance, frequency, etc., of the individual resonators.

In some cases, the device resonator may not accurately communicate with one source, but receive energy from another source resonator. For example, consider the device 1802 transmitting an out-of-band communication signal requesting power from a source. The source 1810 may respond and begin providing power to the device 1802. It is contemplated that device 1816 also sends out-of-band communication signals requesting power from the source, and source 1806 responds and begins providing power to device 1816. Because the device 1802 is close to the source 1806, the device 1802 may receive some or most of its power from the source 1806. If the power level received by the device 1802 becomes too high, the device 1802 may transmit an out-of-band communication signal to the source 1810 to reduce the power it transmits to the device 1802. The device 1802 may still receive excessive power because it is receiving power from the source 1806 but is not transmitting control signals to the source 1806.

Thus, the separation of the energy transfer channel from the communication channel can create performance, control, security, privacy, reliability, etc. issues in a wireless energy transfer system. In an embodiment, it is necessary for a resonator in a wireless energy transfer system to identify/designate and authenticate any or all resonators with which it exchanges power. Those skilled in the art will appreciate that the example shown in fig. 18 is merely one example, and that there are many configurations and arrangements of wireless power transfer systems that may benefit from explicit or implicit energy transfer verification steps.

In an embodiment, potential performance, control, security, privacy, reliability, etc. issues may be avoided by providing an additional verification step that ensures that the energy transfer channel and the communication channel used by a pair of resonators are associated with the same pair of resonators.

In an embodiment, the step of verifying may include some additional exchange of information or signaling over the wireless energy transfer channel. A verification step that includes field communication or information exchange using an energy transfer channel or energy transfer channel may be used to verify that an out-of-band communication channel is exchanging information between the same two resonators that are or will be exchanging energy.

In embodiments with an out-of-band communication channel, the verification step may be implicit or explicit. In some embodiments, verification may be implicit. In an embodiment, the energy delivery channel may be implicitly verified by monitoring and comparing the condition of the energy delivery channel to an expected condition or parameter in response to the out-of-band information exchange. For example, after establishing out-of-band communication, the device may request that the wireless source increase the amount of power it transmits. While parameters of the wireless energy transfer channel and resonator may be monitored. The increase in transmitted power observed at the device may be used to infer that the out-of-band communication channel and the energy transfer channel are properly connected to the designated resonator.

In embodiments, the implicit verification step may include monitoring any number of parameters of the wireless energy transfer, or parameters of the resonator and components, for the wireless energy transfer. In an embodiment, the resonator's current, voltage, impedance, frequency, efficiency, temperature, its drive circuitry, etc. may be monitored and compared to expected values, trends, variations, etc. as a result of the out-of-band communication exchange.

In an embodiment, the resonator may store measured parameters and a table of expected values, trends, and/or changes to those parameters as a result of the communication exchange. The resonator may store a history of communication and observed parameter changes, which may be used to validate the energy transfer channel. In some cases, a single unexpected parameter change resulting from the communication exchange may be insufficient to conclusively determine that the out-of-band channel is incorrectly paired. In some embodiments, a history of parameter changes may be scanned or monitored over several or many communication exchanges to perform verification.

An exemplary algorithm is shown in fig. 19A, which illustrates a series of steps that may be used to implicitly validate an energy transfer channel in a wireless energy transfer system using out-of-band communication. In a first step 1902, an out-of-band communication channel between a source and a device is established. In a next step 1904, the source and the device may exchange information regarding adjusting parameters of the wireless energy transfer or parameters of components for the wireless energy transfer. The exchange of information on the out-of-band communication channel may be a normal exchange in normal operation for system control and regulation of energy transfer. In some systems, the out-of-band communication channel may be encrypted to avoid eavesdropping, counterfeiting, etc. In a next step 1906, the source and device, or just the source or just the device, may monitor and keep track of any changes in the parameters of the wireless energy transfer, or in the components used for energy transfer. The tracked changes may be compared to expected changes to the parameters as a result of any out-of-office communication exchanges. A validation failure may be considered when one or many of the observed changes in the parameter do not correspond to the expected changes in the parameter.

In some embodiments of the wireless energy transfer system, the verification may be explicit. In an embodiment, the source or device may change parameters of the wireless energy transfer, dither, modulation, etc., or parameters of the resonator used for the wireless energy transfer, to transmit or provide the verifiable signal to the source or device over the energy transfer channel. Explicit verification may include changing, altering, modulating, etc. certain parameters of the wireless energy transfer or parameters of the resonator or component used for energy transfer for explicit verification purposes and may not be associated with optimizing, tuning, or adjusting the energy transfer.

Varying, changing, modulating, etc. certain parameters of the wireless energy transfer or parameters of the resonator or component used for energy transfer may also be referred to as in-band communication for the purpose of signal transmission or communication with another wireless energy resonator or component. In embodiments, the in-band communication channel may be implemented as part of the wireless energy transfer resonator and components. Information can be transmitted from one resonator to another by varying the parameters of the resonators. Parameters such as inductance, impedance, resistance, etc. may be dithered or varied by a resonator. These changes may affect the impedance, resistance, or inductance of other resonators surrounding the signal transfer resonator. The variations may manifest themselves as corresponding jitters of the resonator's voltage, current, etc., that can be detected or decoded into the message. In embodiments, in-band communication may include changing, varying, modulating, etc., the power level, amplitude, phase, direction, frequency, etc., of the magnetic field used for energy transfer.

In one embodiment, explicit in-band verification may be performed after the out-of-band communication channel is established. Using the out-of-band communication channel, the source and the device may exchange information regarding power transfer performance and in-band signaling performance. Wireless energy transfer between the source and the device may then be initiated. A source or device may request or challenge other sources or devices for signal transmission using the in-band communication channel to verify the connection between the out-of-band communication channel and the energy delivery channel. When the in-band communication channel observes that an agreed signal transmission is established in the out-of-band communication channel, the channel is verified.

In an embodiment, the verification may be performed only during a specific or predetermined time period of the energy exchange protocol, e.g. during energy transfer initiation. In other embodiments, the explicit verification step may be performed periodically during normal operation of the wireless energy transfer system. When the efficiency or characteristics of the wireless power transfer changes, a verification step may be triggered, which may signal a physical orientation change. In an embodiment, the communication controller may retain a history of the energy transfer characteristics and initiate verification of the transfer, including signaling using the resonator when a change in the characteristics is observed. Changes in energy transfer characteristics can be observed in terms of changes in efficiency, impedance, voltage, current, etc. of energy transfer of the resonator or resonator components, and power and control circuitry.

Those skilled in the art will appreciate that the signaling and communication channels over which messages can be sent may be secured with any number of encryption, authentication, and privacy algorithms. In an embodiment, out-of-band communications may be encrypted and a secure communication channel may be used to transmit a random sequence for authentication using an in-band channel. In embodiments, the in-band communication channel may be encrypted, randomized, or protected by any well-known security and encryption protocols and algorithms. Security and encryption algorithms may be used to authenticate and verify compatibility between resonators and may use Public Key Infrastructure (PKI) and secondary communication channels for authorization and authentication.

In embodiments of an energy transfer system between a source and a device, the device may validate the energy transfer channel to ensure that it receives energy from an expected or assumed source. The source may validate the energy delivery channel to ensure that energy is delivered to the desired or assumed source. In some embodiments, authentication may be bi-directional, and both the source and the device may authenticate their energy delivery channels in one step or protocol operation. In embodiments, there may be more than two resonators, and there may be repeater resonators. In a multiple resonator embodiment, communication and control may be centralized in one or a few resonators, or communication and control may be distributed among many, most, or all resonators in the network. In embodiments, communication and/or control may be implemented by one or more semiconductor chips or microcontrollers, which may be coupled to other wireless energy transfer components.

An exemplary algorithm is shown in fig. 19B, which illustrates a series of steps that may be used to explicitly authenticate an energy transfer channel in a wireless energy transfer system using out-of-band communication. In a first step 1908, an out-of-band communication channel between the source and the device is established. In a next step 1910, the source and device may coordinate or agree on a signal transmission protocol, method, scheme, etc. that may be transmitted over the wireless energy transfer channel. To avoid eavesdropping and to provide privacy, the out-of-band communication channel, source and device may follow any number of well-known cryptographic authentication protocols. In systems that are afforded cryptographic protocol capabilities, the passcode may include a challenge-response type exchange that may provide an increased level of confidentiality and authentication capabilities. For example, the device may challenge the source to encrypt a random authentication code that it sends to the source via an out-of-band communication channel using a common secret encryption key or private key. The verification code may then be transmitted in an out-of-band communication channel via in-band communication channel signaling 1912. In the case of sources and devices that are given cryptographic protocol capabilities, the verification code of the signal transmission in the in-band communication channel may be encrypted or modified by the sender with a reversible cryptographic function, allowing the receiver to further authenticate the sender and verify that the in-band communication channel is connected to the same source or device associated with the out-of-band communication channel.

In case of a failure of the authentication, the wireless energy transfer system may attempt to repeat the confirmation process. In some embodiments, the system may attempt to re-acknowledge the wireless energy delivery channel by exchanging another authentication sequence for signaling using the in-band communication channel. In some embodiments, the system may change or alter the sequence or type of information used to authenticate the in-band communication channel after a failure to attempt to authenticate the in-band communication channel. The system may vary the type of signaling, protocol, length, complexity, etc. of the in-band communication authentication code.

In some embodiments, the system may adjust the power level, modulation intensity, modulation frequency, etc. of the signal transmission in the in-band communication channel based on the failure of the in-band communication channel, and thus the energy delivery channel, to verify. For example, based on a device failing to verify the source, the system may attempt to perform verification at a higher energy transfer level. The system can increase the power output of the source, producing a stronger magnetic field. In another example, a source transmitting an authentication code to a device may increase or even multiply the amount of change in the impedance of the source resonator for signal transmission by changing the impedance of its source resonator based on the device failing to authenticate the source.

In an embodiment, based on a failure to verify the energy delivery channel, the system may attempt to probe, find, or discover other possible sources or devices using the out-of-band communication channel. In an embodiment, the out-of-band communication channel may be used to find other possible candidates for wireless energy transfer. In some embodiments, the system may change or adjust the output power or range of the out-of-band communication channel to help minimize failed pairings.

The out-of-band communication channel may be power modulated to have several modes, a long-range mode to detect a source, a short-range mode or a low-power mode to ensure communication with another device or source in the vicinity. In an embodiment, the out-of-band communication channel may be matched to the range of the wireless channel for each application. After the authentication of the energy delivery channel fails, the output power of the out-of-band communication channel may be slowly increased to find other possible sources or devices for wireless energy delivery. As described above, the out-of-band communication channel may exhibit interference and blockage, which may be different from that of the energy transfer channel, and the sources and devices requiring higher power levels for out-of-band communication may be close enough to allow wireless energy transfer.

In certain embodiments, the out-of-band communication channel may be oriented, arranged, focused, etc. using shielding or positioning so as to be effective only in a limited area (i.e., in the case of a vehicle) to ensure that it can only establish communication with another source or device in close enough proximity, location, and orientation for energy transfer.

In embodiments, the system may use one or more supplemental sources of information to establish an out-of-band communication channel or to validate an in-band energy delivery channel. For example, during initial establishment of the out-of-band communication channel, the location of the source or device may be compared to a database of known or graphically-located locations or locations of wireless sources or devices to determine the pairs for which energy delivery is most likely to succeed. Out-of-band communication channel discovery may be supplemented with GPS data from one or more GPS receivers, data from positioning sensors, inertial navigation systems, and so forth.

Tunable wireless power transfer system architecture

One embodiment of a system diagram for a source unit in a wireless power transfer system is shown in fig. 20A. The DC/DC converter in this embodiment may be used to allow adjustment of at least one source parameter, such as the DC bus voltage of the switching amplifier, and thus the amplifier output power. One embodiment of a system diagram for a device unit in a wireless power transfer system is shown in fig. 20B. The DC/DC converter in this embodiment may be used to allow adjustment of at least one device parameter, such as the DC load voltage at the output of the DC/DC converter, or the impedance seen at the input of the rectifier. In this specification we will demonstrate that it is possible to adjust the same parameters in the source and device units and achieve full tuning of the system without using a DC/DC converter, but only using a controllable (tunable) switching amplifier and rectifier, as shown in fig. 21A and 21B. Since each power system level in the system (e.g., DC/DC converter) is typically associated with some efficiency cost, the cancellation stages may cancel the energy loss of these stages. Thus, wireless power transfer system embodiments that do not use a DC/DC converter may have improved system efficiency relative to systems that use a DC/DC converter.

Tunable switching converter

The switching amplifier and rectifier may have a class D or E half-bridge or full-bridge topology. For one illustrative embodiment, we consider a class D half-bridge topology, where the voltage on the DC side of the converter (amplifier or rectifier) can be approximately constant and can be implemented by using an appropriately sized DC filtered shunt capacitor, and the current on the AC side of the converter can be approximately sinusoidal and can be implemented by using an appropriately sized filtered series inductor to filter out higher order current harmonics generated by the switching converter. The topologies of an exemplary amplifier and an exemplary rectifier are shown in fig. 22A and 22B. Although specific exemplary topologies may be investigated herein, it should be understood that any topology may be used in a system for wireless power transfer designed with the general principles of this specification. For example, a full-bridge converter with a DC-filtered series inductor and an AC-filtered shunt capacitor may be designed to provide a sinusoidal AC voltage and a constant DC current.

A switching converter suffers losses during conduction through the switch and in the case of switching if the switch with the parallel capacitance is conducting at a non-zero voltage or if the switch with the series inductance is off at a non-zero current.

Rectifier

Rectifiers often use diodes as switches, which may have a small parallel capacitance. Since diodes can be considered to be self-switching, in the topology of fig. 22B, they can typically self-turn on at near zero voltage and turn off at near zero current, so they do not suffer from switching losses. But they suffer from large conduction losses due to the diode voltage drop. Thus, a MOSFET or any type of active switch, including but not limited to, a transistor, a Field Effect Transistor (FET), an IGBT, etc., preferably can be used as a switch and can be synchronized with the input current waveform and configured to operate in a manner similar to a diode, but suffer only much less conduction loss due to the MOSFET's small on-resistance. Replacing the diode with a MOSFET creates an architecture sometimes referred to as a synchronous rectifier. The mosfet may have a parallel output capacitance and a parallel inverted body diode. In some embodiments, the external capacitor and/or diode may be integrated with the capacitorEach MOSFET of the current bridge is connected in parallel. The external diode may be a schottky diode. Effective capacitance C of MOSFET bridge_rCan be defined as the capacitance from the input towards the bridge when the switch is on. Since the switch is in series with the input during conduction, the smaller the real part of the AC input rectifier impedance, the greater the effect on efficiency due to the on-resistance of the switch. In some embodiments, a MOSFET may be selected that has an on-resistance that is substantially less than the desired real part of the input impedance.

In some embodiments, the MOSFET may be switched on and off at substantially the same point in time as the diode is switched on and off, so that the parallel capacitance may discharge (i.e., zero voltage) when conducting (a so-called zero voltage switching ZVS condition) and render the parallel diode non-conductive. Instead, the current flows through the MOSFET itself. Thus, the rectifier can operate with minimal losses, small conduction losses of the on-resistance of the MOSFET. For the topology of FIG. 22B, the corresponding voltage, current and switching waveforms are shown in FIG. 23A, where they can be seen to be symmetric for both halves of the cycle, with dead time (dead time) when both switches are off. In this mode of operation, the dead time phase of the upper switchOn duty D, input complex impedance Z of rectifier_rAnd DC output voltage V_DCWith amplitude I of the input sinusoidal current_ACRatio of (A to (B))_IOMay depend only on the DC load resistance R_lAnd an effective capacitance C_r. For the half bridge embodiment of FIG. 22B, Z_IORatio, dead time phase and complex input impedance Z of the rectifier_rGiven by the following equation:

in some embodiments, C may be used during operation by a microcontroller or other processor component within the device unit_rAnd a DC load resistance R_lThe appropriate dead-time phase is calculated and adjusted in real-time. The MOSFET rectifier during operation can be dynamically adjusted so that ZVS can be maintained and the parallel diode is non-conductive (or only minimally conductive) so that its efficiency can be optimized while varying the load. In some embodiments, the full input voltage waveform may be monitored and the dead-time phase may be adjusted to substantially maintain ZVS and minimum conduction or non-conduction through the parallel diodes.

It should be noted that in this mode of this embodiment of the rectifier, the switch may also be opened at another zero current (so-called zero current switch ZCS condition). This is because the diode switch can be self-opening and we can design the MOSFET to mimic diode operation. Since the diode and MOSFET may have substantially no series inductance, maintaining ZCS at off may not be important. Thus, in some embodiments, the MOSFET rectifier can be designed so that the MOSFET may not turn off at ZCS time, but at a later time. This design may not compromise the ZVS bandpass MOSFETs, which is feasible by simply adjusting the associated dead time during which both switches are open. Fig. 23B shows voltage, current, and switching waveforms for an embodiment where only one (lower) switch is open at a time offset from ZCS time. Fig. 23C shows the waveform for an embodiment where both (lower and upper) switches are shifted the same phase from ZCS so that the waveform is still symmetric in both halves of the cycle. Fig. 23C shows waveforms for an embodiment where both switches are shifted from ZCS, but shifted by different phases. Fig. 23B and 23D are asymmetric for two halves of the period. Thus, in the above embodiments of the switching sequence for the lower and upper MOSFETs of the half-bridge rectifier, the off-times can be tuned independently(delayed from ZCS). Thus, with tuning these, even the DC load resistance R_lCan be fixed or variable, and can adjust the input complex impedance Z of the rectifier_r. These adjustments can be made without substantially sacrificing efficiency, since ZCS may not be lost and the parallel diode is almost never or minimally conducting. Each of the above operating mode embodiments may give a different AC input impedance even for the same DC load impedance. In this way, the mode of operation can be selected according to the desired output voltage or power adjustment or according to the subsequent real part of the AC input impedance, so that the effect of the on-resistance of the MOSFET on the efficiency is minimal.

In the operating mode shown in fig. 23B, the on duty cycle D of the upper switch can be independently tuned to zero and D_oA value in between. The electrical characteristics of this half-bridge rectifier embodiment are determined by the relationship between Z and_IO、and Z_rThe formula of (a) gives:

φ_ON＝cos^-1[ωC_rZ_IO-cos(2πD)],φ₁＝π-2πD,φ₂＝cos^-1(ωC_rZ_IO-1)

note that becauseThus, theAnd D = D_oResults of previous rectifier embodiments are given, whereinThe duty cycle is tuned for the DC load and ZCS is maintained.

In some embodiments, C may be used during operation by a microcontroller or other processor component within the device unit_rAnd knowledge of real-time measurements of DC load resistance, and/or knowledge of one or more desired system performance characteristics, e.g., duty cycle D, ratio Z_IOAnd/or real part of rectifier impedance in equal real time and adjusting appropriate phaseAndin such an embodiment, the tunable MOSFET rectifier can be dynamically adjusted during operation so that ZCS can be maintained and the parallel diode is nearly never or minimally conducting, thereby optimizing its efficiency, while the load can be varied and the desired output voltage or power or input impedance level can be adjusted. In some embodiments, the full input voltage waveform may be monitored and the phase may be adjustedTo substantially maintain ZVS with little or no conduction through the parallel diode.

Similar conclusions can be drawn for the modes of operation of fig. 23C and 23D. Likewise, the input impedance, output voltage, and power level of the rectifier may be adjusted by tuning one or both phase shifts from the ZCS.

In some embodiments, the rectifier may have a full bridge topology. To achieve the same duty cycle tuning without compromising efficiency in the full bridge, in some embodiments the left and right sides of the bridge may be operated with the switching waveforms shown in fig. 23C but phase shifted by half a cycle, and in some embodiments operated with the switching waveforms shown in fig. 23A but phase shifted by some value less than half a cycle.

Amplifier with a high-frequency amplifier

In one embodiment of the rectifier in fig. 22A, MOSFETs may be used as switches. The MOSFET may have a parallel output capacitance and a parallel inverted body diode. In some embodiments, an external capacitor and/or diode may be connected in parallel to each MOSFET of the amplifier bridge. In some embodiments, the ambient diode may be a schottky diode. Effective capacitance C of MOSFET bridge_aCan be defined as the capacitance seen from the amplifier output when no switch is on. Since the switch can be in series with the output during conduction, the smaller the real part of the AC impedance, the greater the effect on efficiency due to the on-resistance of the switch. In some embodiments, a MOSFET may be selected that has an on-resistance that is substantially less than the desired real part of the output impedance. Since the topologies of fig. 22A, 22B of the MOSFET amplifier and rectifier are identical, the possible different operating modes of the amplifier can be analyzed by time-inverting the waveforms of the respective rectifiers.

In some embodiments, for the low and high switching of the half bridge, a switching sequence may be used that is symmetric between the two halves of the cycle. In such an embodiment, if the value Z is connected to the output of the amplifier_r ^*Complex impedance of (2), wherein Z_rGiven in equation (1), then the DC input impedance R of the amplifier_aMay be equal to the corresponding R in equation (1)_lThe on duty cycle of the upper switch may be D given in equation (1)_oThe voltage and current waveforms may be time inversions of those in fig. 23A, indicating that simultaneous ZVS and ZCS are achieved. If any R is connected at the output of the amplifier_lEquation (1) does not give a complex impedance of a value that ZVS and ZCS cannot be achieved simultaneously. For a set of complex impedances that are inductive, ZVS can be implemented so that high efficiency can be maintained, the waveforms can be time inversions of those in fig. 23C. Also note that the ZCS condition may not be critical to the switching efficiency of the amplifier, as the MOSFETs may not have substantial series inductance. When following this ZVS, ZCS during switch turn-on may primarily mean that the ZVS condition is also achieved by a zero derivative voltage, thus at timingAspects allow for improved tolerance for implementing ZVS times. That is, certain time ranges are allowed in which ZVS is sufficiently close. In these embodiments, the symmetric switching sequence and duty cycle D may be uniquely determined by the AC complex impedance at the amplifier output, the requirement to achieve ZVS at the turn-on instant, and little or no conduction through the parallel diodes. Thus, given a fixed DC input voltage, it may not be possible to independently adjust the power stage to a desired amount without sacrificing some efficiency.

In some embodiments, C may be used during operation by other processor components within the microcontroller or source unit_aAnd knowledge of real-time measurements of the AC output impedance, determine (i.e., calculate, know using a look-up table, etc.) and adjust the appropriate duty cycle D and dead time in real-time. The MOSFET amplifier during operation can be dynamically adjusted so that ZVS can be maintained, with the parallel diode non-conducting or only minimally conducting, allowing its efficiency to be optimized while varying the load. In some embodiments, the full input voltage waveform may be monitored and the switching sequence may be adjusted to substantially maintain ZVS and little or no conduction through the parallel diodes.

In some embodiments, for the low and high switching of the half bridge, a switching sequence may be used that is asymmetric between the two halves of the cycle. That is, the on-time of the MOSFET may occur at or near ZVS to maintain adequate efficiency, but the off-time of the upper MOSFET may be tunable. This solution provides a separate tuning knob by means of which the power of the amplifier can be adjusted. If the value Z is connected at the output of the amplifier_r ^*Complex impedance of (2), wherein Z_rGiven in equation (2), then the DC input impedance R of the amplifier_aMay be equal to the corresponding R in equation (2)_lThe on duty cycle of the upper switch may be D given in equation (2), and the voltage and current waveforms may be time reversals of those in fig. 23B, indicating that ZVS is achieved at two on times and ZCS is achieved at one on time. If connected at the output of the amplifier for any D and R_lEquation (2) Complex impedances of no given value, ZCS cannot be achieved at any time. For a set of complex impedances that are inductive, ZVS can be implemented so that high efficiency can be maintained, the waveforms can be time-reversed versions of those in fig. 23D.

In some embodiments, C may be used during operation by other processor components within the microcontroller or source unit_aAnd knowledge of at least one of real-time measurement of the AC output impedance, and knowledge of one or more desired system performance characteristics, e.g., duty cycle D, ratio Z_IOAnd/or DC input impedance, etc., determining and adjusting the appropriate duty cycle D and dead time in real time. The tunable MOSFET amplifier during operation can be dynamically adjusted so that ZVS can be maintained, the parallel diode is almost never or minimally conducting, so that its efficiency can be optimized while changing the output impedance and the desired power level can be adjusted. In some embodiments, the full input voltage waveform may be monitored and the switching sequence may be adjusted to substantially maintain ZVS and little or no conduction through the parallel diodes.

In some embodiments, the amplifier has a full-bridge topology. To achieve the same duty cycle without compromising efficiency in the full bridge, the left and right sides of the bridge may be operated with the switching waveforms shown in fig. 23C but time reversed and phase shifted by half a cycle, or with the switching waveforms shown in fig. 23A but time reversed and phase shifted by some value less than half a cycle.

From the above, it can be concluded that: the switching amplifier and switching rectifier can be designed such that high efficiency is maintained while the independent duty cycle "knobs" are tuned to adjust certain characteristics of the converter. This knob or adjustable parameter may be shown to be able to provide tuning tasks in the wireless power transfer system that would otherwise be accomplished using a DC/DC converter.

Tunable wireless power transfer system

As an exemplary embodiment, consider wireless power transferCase of system WPT, which may not change (R)_s、L_s、R_d、L_dAnd M_sdMay not change) the load may have a constant resistance R_l. Fig. 22A and 22B show this exemplary embodiment. For this fixed overall system, tunable elements may not be needed in the source and device units to optimize end-to-end efficiency. Conversely, to optimize the efficiency of the system, the impedance matching network IMN of the device may be designed, as previously disclosed_dSo that at an operating frequency f = ω/2 π, the input impedance Z of the rectifier, as seen from the device coil to the load, is_rCan be changed intoOr equivalently, in the IMN_dWhen looking into the load, is subtracted from the device coil (R)_d+jωL_d) Then is transformed intoThe reflected impedance to the source coil may beOr equivalently, the source coil impedance (R) is added_s+jωL_s) After that, at the terminals of the source coilThe impedance matching network of the source can thus be designed such that at the operating frequency this impedance can be transformed into the appropriate impedance Z_sSo that the amplifier operates with minimal loss (e.g., at ZVS and ZCS) and outputs the desired amount of power. When the above impedance levels are achieved, we can say that the system operates under impedance matching conditions.

The above impedance levels may achieve good WPT efficiency. The power level may be adjusted by means of a tunable amplifier, which may be used to modify its output power by tuning its duty cycle (giving up ZCS). In this way, the impedance level of the entire WPT system may not change (the impedance matching of the system may be maintained), so that good overall efficiency may be maintained. In some embodiments, a tunable rectifier may be used to modify its output power by tuning its duty cycle (giving up ZCS) and thus its input impedance. In this way, the impedance level of the WPT system may be changed, but in some cases there is substantially no effect on efficiency.

As another example, consider the case of a WPT system as follows: the load in the equipment unit has a constant resistance R_lBut the coil parameter (R)_s、L_s、R_d、L_dAnd M_sd) May change due to a change in its relative position or a changing external disturbance. In order to maintain maximum WPT efficiency, it is desirable to be tunable at the source and device impedance levels so that the impedance is available when looking from the device coil to the loadAnd impedances providing ZVS and ZCS can be obtained at the amplifier output. Since each of these two impedances may be complex and may have real and imaginary parts, in some embodiments two tunable "knobs" (otherwise referred to as components, parameters, quantities, values, etc.) may be used for the device, and two for use in the source unit. In certain embodiments, as described above, two knobs used in the source unit may provide the ability to tune for ZVS and ZCS as the system varies, which may be the duty cycle and IMN of the amplifier_sThe value of the inner one of the tunable components, e.g. the value of the tunable capacitor. Similarly, in some embodiments, two knobs for use in an equipment unit may be provided for system-wide variationsAbility to tune, which may be the duty cycle and IMN of the rectifier_dThe value of the inner one of the tunable components, e.g. the value of the tunable capacitor. Tunable amplifiers can be used to reduce their output power by reducing their duty cycle (giving up ZCS). In this way, the impedance level of the entire WPT system may not change, thereby maintaining good performanceThe overall efficiency of (a). Maintaining a real impedance at a deviceMay mean that the device needs to be kept resonant. Similarly, maintaining ZVS and ZCS for the source amplifier may mean that the source resonance needs to be maintained otherwise the output impedance of the amplifier gets a value that does not deliver sufficient power to it and is either capacitive so that ZVS cannot be achieved or very inductive so that ZCS is lost to a large extent and the on-resistance of the MOSFET may be comparable to the real part of the output impedance, resulting in a drop in efficiency due to conduction losses. The purpose of the tunable IMN in such embodiments may thus be to keep the resonant frequency of the resonator sufficiently close to the operating frequency.

In some embodiments, if only coupling between coils, i.e. M_sdAnd can vary substantially, there is no need for a tunable IMN to provide sufficient power to a load with sufficient efficiency. The fixed IMN may be designed such that a desired amount of power may be delivered to the load over a desired coupling operating range, while the tunable rectifier may be used to improve efficiency by adjusting its input impedance, the tunable amplifier may be used to fully achieve ZVS with little or no diode conduction, and additional adjustment of power levels if needed.

In another exemplary embodiment, consider now the case of a WPT system as follows: the coil parameters and coupling may not be changed (R)_s、L_s、R_d、L_dAnd M_sdMay not change) but the load may require a varying amount of power and may need to be at a constant voltage. In some embodiments, this load may be a battery charging circuit for a battery, an LED light, or the like. For this case, a DC/DC converter may be used after the rectifier in the device unit to regulate the output voltage to a desired level, as shown in fig. 20B. In this specification we propose that this DC/DC converter may not be required. It is contemplated that the system may be initially designed at a maximum load power level to achieve impedance matching throughout the WPT systemThe WPT efficiency is optimized and the correct output DC voltage is seen at the load. In some embodiments, a tunable amplifier may be used at the source unit so that as the power required by the load decreases, the output power of the tunable amplifier may also decrease by the same amount (by reducing its duty cycle and losing ZCS), which may result in the DC load voltage and the degree of impedance matching remaining substantially the same because the system coupling the resonators is substantially linear. In some embodiments, a tunable rectifier may be used to maintain a desired output DC voltage level at the load, while load power requirements may be reduced. In this embodiment, the efficiency of the WPT system may be affected, but the efficiency may be sufficient for some applications, by losing the optimum impedance match and the power output of the source amplifier changing only in accordance with changes in its output impedance.

In another exemplary embodiment, loads of the above type may be used in a WPT system, as the coupling between the coils may change and external disturbances may affect the system, the system may also change (R)_s、L_s、R_d、L_dAnd M_sdMay vary). The desired operational goals that need to be maintained in the system are four: (1) DC load voltage for specified operation of the load, (2, 3) matching the impedance level seen from the device coil to the load(real and imaginary parts) to maximize WPT efficiency, and (4) resonance at the source so that the impedance at the amplifier output (essentially the ratio of its real to imaginary parts) can be at an appropriate level to allow sufficient power to be delivered to it (and thus the device load) and to avoid capacitive or polar impedances that would result in reduced amplifier efficiency.

To maintain these four system goals, typically four tunable knobs would be required in the system. In the proposed embodiment, the four knobs may be the tunable duty cycle of the source amplifier, the tunable duty cycle of the device rectifier, IMN_sIn (1) canTuning elements (e.g. capacitors), and IMN_dA tunable element (e.g., a capacitor) in (1). In some embodiments, all four knobs may be tuned to achieve all four desires simultaneously. In some embodiments, each knob may target one desire, and the system may converge to an overall desired condition as all knobs tune to their individual targets. In one such embodiment, the duty cycle of the rectifier may be tuned to maintain a desired DC output voltage at the load, and the IMN may be tuned_sTo maintain source resonance, to tune the duty cycle and IMN of the amplifier_dTo maintain impedance matching conditions at the device. This last step can be achieved because adjusting the power stage adjusts the AC input impedance of the rectifier (due to the non-linear load connected to its output) and the IMN can be tuned_dThe element may adjust the resonance of the device. In another embodiment, the duty cycle of the amplifier may be tuned to adjust for a constant DC load voltage, as may the IMN_sTo maintain source resonance, to tune the duty cycle and IMN of the rectifier_dTo maintain impedance matching conditions at the device.

In some embodiments, if the resonance of the device resonator does not substantially change (typically because the inductance of the device coil does not substantially change due to perturbations), the IMN may not be required_dTo achieve the desired power delivered to the load at the desired DC voltage and with sufficiently high efficiency. In some such embodiments, the IMN may be tuned_sThe duty cycle of the rectifier can be tuned to maintain the DC load voltage, and the duty cycle of the amplifier can be tuned to maximize the overall transfer efficiency. In some embodiments, the roles of the duty cycles of the amplifier and rectifier may be reversed. In some embodiments, instead of maximizing efficiency, one duty cycle knob may be tuned to achieve a particular AC impedance level at the rectifier input.

In some embodiments, if only a lineCoupling between turns, i.e. M_sdIt can be varied in nature that the tunable IMN is not required at both the source and the device to provide the required power to the load at the required voltage level with sufficient efficiency. In some embodiments, the duty cycle of the rectifier may be tuned to maintain the DC load voltage and the duty cycle of the amplifier may be tuned to maximize the overall transfer efficiency. In some embodiments, the roles of the duty cycles of the amplifier and rectifier may be reversed. In some embodiments, instead of maximizing efficiency, one duty cycle knob may be tuned to achieve a particular AC impedance level at the rectifier input.

In some embodiments, an additional knob that can be tuned at the amplifier is the switching (and thus operating) frequency. Tuning the frequency may provide power adjustment. In certain embodiments of WPTs with high Q resonators, where close resonance is required between the resonators, the tuning frequency may be used to adjust the power, as long as all device elements may include a tunable IMN such that their resonance frequency may be adjusted to substantially match the operating frequency.

In some embodiments, the additional tunable knobs available may be additional tunable elements in the IMN of the source and device.

In a typical battery powered device, a charging circuit may be in front of the battery to charge the battery with a particular charging profile over each charging cycle. In embodiments, the ability of the WPT system embodiments of the present description to regulate the output of the device unit may allow for direct connection of the device unit to the battery without additional charging circuitry, or if additional charging circuitry is still needed, it may be smaller, less expensive, and may include fewer components. That is, in an embodiment, the WPT system itself may be the battery charging circuit of the battery, which performs all battery management, such as monitoring the battery status (e.g., voltage or temperature), and requiring different amounts of power at different portions of the charging cycle. A typical charging profile, such as for a Li-ion or NiMH battery, may include time intervals of constant current or constant voltage provided by the charging circuit. It has been demonstrated in this specification that in certain embodiments, a WPT system can maintain a DC load voltage at the rectifier output by tuning at least one system knob. In some embodiments, this knob may be the duty cycle of a tunable rectifier. When directly connected to a battery, the battery often automatically sets the output voltage to its own internal instantaneous voltage. Thus, in some embodiments, the system tuning knob may be tuned to maintain the DC load current (instead of voltage) at the rectifier output. In some embodiments, this tuning knob may also be the duty cycle of a tunable rectifier. In certain embodiments, the WPT system achieves any desired charging profile, including constant current or constant voltage intervals, by tuning at least one system knob. In some embodiments, this tuning knob may be the duty cycle of a tunable rectifier.

In an embodiment of the WPT system, the system control that causes its tuning may depend on the measurement of the parameter list. In the source unit, the DC voltage and current may be measured to determine the input power and DC impedance to the source amplifier. The measurement of the source DC power, voltage and/or current may be used to tune the duty cycle of the amplifier in order to adjust the power, voltage and/or current input to the source unit. Also in the source unit, the AC voltage and/or current may be measured to determine the output power and/or the AC impedance of the source amplifier. As explained before, the measurement of the AC impedance can be used to tune the switching time of the amplifier MOSFET in order to achieve ZVS and the current almost never passes through the parallel diode, but through the MOSFET. The measurement of the AC impedance may also be used to tune the value of one or more tunable elements in the source impedance matching network in order to maintain the source resonance and/or to modify the AC impedance to a value that allows for the desired output power from the amplifier, but with better amplifier efficiency. In the plant unit, the DC voltage and/or current may be measured to determine the output power delivered by the plant rectifier to the load and the instantaneous DC load impedance. The measurement of the device DC power, voltage and/or current may be used to tune the duty cycle of the rectifier in order to regulate the power, voltage and/or current output from the device unit to the load. Also in the device unit, the AC voltage and/or current may be measured to determine the input power and/or the AC input impedance to the device rectifier. As explained earlier, the measurement of the DC impedance and the synchronization with the input AC current waveform can be used to tune the switching time of the MOSFET in order to achieve ZVS, and the current almost never passes through the parallel diode, but through the MOSFET.

In some embodiments, an analog filter may be used to filter the sensed AC source and/or device voltage waveform. In some embodiments, the filter may comprise a Single Amplifier Biquad (SAB) high Q low pass or band pass filter.

In some embodiments, the AC source and/or device current may be measured using a current sensing transformer. In some embodiments, if the impedance matching network includes an inductor connected in series to the AC side of the amplifier and/or rectifier, the AC current may be measured by modifying the inductor into a transformer by adding one or more secondary turns. In some embodiments, an analog filter may be used to filter the sensed current waveform. In some embodiments, the filter may comprise a Single Amplifier Biquad (SAB) high Q low pass or band pass filter.

In the tunable rectifier embodiment, synchronization of the switching waveform of the rectifier MOSFET with the AC current input to the rectifier may be achieved using analog circuitry, digital circuitry, a microcontroller, or any combination thereof. In some embodiments, the AC current may be sensed, filtered, and input to a comparator to generate a synchronization signal. In some embodiments, the comparator may be internal to the microcontroller. The switching waveform of the rectifier MOSFET needs to be delayed with respect to the synchronization signal. In some embodiments, the delay may be implemented with discrete analog or digital components or internally within the microcontroller. In some embodiments, the variable duty cycle (or phase shift) switching waveforms of the rectifier MOSFETs may be generated using analog and digital logic circuits or internally within a microcontroller.

In embodiments of the WPT system, the system control that causes its tuning may also require running algorithms in the processing unit, which may be in the source unit, the device unit, or both. The algorithm may utilize one or more measured system parameters and may determine the necessary modifications to the tunable parameters of the system. The algorithm may be a global algorithm that accepts all measured parameters and passes all necessary tuning. The algorithm may be a summation of multiple algorithms that run in series or parallel, resulting in overall convergence. In such multiple algorithm embodiments, some algorithms may be run in the source unit and some may be run in the device unit.

In an embodiment of the WPY system, a control algorithm running in one unit of the WPT system may require information about parameters measured at different units of the WPT system. Such information may be communicated in different units via a communication channel. In some embodiments, the communication channel for information transfer may be the same as for energy transfer. In such embodiments of in-band communication, at least one parameter or component of the information transmitting unit needs to be tunable so that measurable changes to the operation of the information receiving unit can be achieved. The tunable parameter or component may be a duty cycle in a converter of the unit, or a tunable element in an IMN of the unit, etc. In some embodiments, the communication channel for information transfer may be a different channel than the energy transfer. In such out-of-band communication embodiments, any standard method and platform for communication operating at any frequency other than the WPT operating frequency may be used.

In embodiments of the WPT system, the symmetry of the tunable MOSFET amplifier and rectifier may allow for the interchanging of roles of the cells of the WPT system. That is, the source unit may operate as a device and the device unit may operate as a source. The system may thus allow bidirectional flow of power. This feature is useful for several reasons in the control of the system and its application. Bidirectional operation is more advantageous when the load in the equipment unit is the battery itself. The system can then run in reverse without any topology modifications.

In some embodiments of system control, some communication protocols may periodically, but in a very short amount of time, condition the system to perform the following algorithm: all units in the WPT system except for one that operates as a source unit operate as devices so that the unit that operates as a source unit can perform measurements (and possibly receive information about measurements performed at other units by means of communication) and tune itself; all units act as this tuning unit in turn, so that when all units are tuned, the system reaches its optimum tuning state. In other embodiments, different algorithm changes may require that a unit change roles in a short amount of time from what it normally has during power transfer.

In an embodiment of the application, the ability of the unit to operate bi-directionally allows this unit, which normally operates as a device powered by a particular source, to operate as a source at other times, powering different devices. Illustratively, a notebook computer may include a WPT unit that typically operates as a device powered by a source unit in a built-in desk, but at other times (e.g., during travel) it may operate as a source, powering device units within a mobile phone, smart phone, headset, digital camera, etc.

The above description of the logical structure and configuration of the high efficiency tunable converters in WPT systems may be extended to systems with multiple units, e.g. multiple sources and/or multiple devices, possibly multiple repeater units. In such embodiments, the tunable rectifier in each device unit may tune its duty cycle to adjust for a fixed DC voltage or fixed DC current or any desired battery charging profile at the load output. In some embodiments, the tunable amplifier in each source unit may tune its duty cycle to adjust its output power. This power adjustment may allow the overall system efficiency to be optimized. In some embodiments, where tunable elements are present in the IMN of some or all of the system elements, additional tuning knobs may allow for more complex system control with the ultimate goal of optimizing system efficiency, subject to constraints on required DC load voltage, load power requirements, maximum source power delivery capability, and the like. In general, different devices may have conflicting interests with respect to increasing or decreasing power output from one or more source units. In some embodiments, the power output from the source unit may be adjusted to meet the maximum power requirements from all devices up to the maximum output power level possible. Thus, in devices that require less power, if they are tuned close to resonance, there is a large amount of cycling and thus power dissipated. In certain embodiments, one or more tunable elements are present in the IMN of a device, which in a WPT system with multiple devices, may be tuned in devices that require less power to reduce the power dissipated in the device while maintaining a desired output power, voltage, or current.

Exemplary System embodiments

Fig. 24 shows an exemplary block diagram of a wireless energy transfer system according to the present invention. The system of fig. 24 includes a wireless energy source that delivers energy to at least one wireless energy capture device. The system includes a tunable source element and a tunable device element that enable adjustment of the energy transfer of the system. The adjustment of the energy conduction may be used to control the amount of energy delivered to the device. The adjustments may be used to control the power delivered to the load under different load conditions and different device positions/orientations relative to the source. The adjustment of energy transfer may be used to ensure efficient transfer of energy by reducing energy wasted or dissipated in system elements due to excess energy stored or flowing through the system elements.

The source of the system may include a tunable switching amplifier and a tunable impedance matching network. The tunable elements of the source may be used to adjust the power output of the source, the efficiency of the source and the resonant frequency of the source resonator. In an exemplary embodiment, the tunable switching amplifier 2402 is connected to an energy source, such as a DC voltage source, for example. The DC voltage of the energy source may be converted to a switching or oscillating voltage by switching amplifier 2402 and used to drive source resonator coil 2422 through impedance network 2404. The switching amplifier may have an adjustable or tunable switching frequency. In some embodiments, the frequency of the switching amplifier may be used to adjust the power output of the amplifier. Driving the source resonator below or above the resonant frequency of the source can be used to vary the power output of the amplifier. In an exemplary embodiment, the switching amplifier preferably has a substantially fixed or constant switching frequency during normal operation of the amplifier. The switching frequency of the amplifier is preferably matched to the system frequency or may be substantially equal to the resonant frequency of the source resonator. In this embodiment, the power control of the source is preferably controlled by adjusting the duty cycle of the amplifier or the phase shift of the amplifier.

The impedance matching network of source 2404 may be tuned to provide efficient operation of the amplifier. The impedance matching network may include tunable components to provide impedance matching between the amplifier and the resonator of the source for efficient energy transfer. The impedance matching network may also include tunable components to provide control and adjustment of the resonant frequency of the source. Since the parameters of the resonator are disturbed by the environment, the tunable component may be used to maintain the resonant frequency of the source substantially at the system frequency, due to changes in device operation, device movement, etc.

The tunable elements of the source may be controlled by means of a feedback or control loop in the source. The tunable elements of the source can be controlled by means of a feedback or control loop based on measured parameters of the source voltage, current, temperature, field strength, etc. The tunable elements of the source may be controlled by means of a feedback or control loop using information exchanged with the devices of the system.

For example, in the exemplary embodiment shown in fig. 24, the source may include an amplifier control 2410 that takes one or more measurements of DC voltage and DC current at the input to the amplifier. Measuring the input voltage and current at the amplifier input 2416 can determine the power input to the source and can infer the power output of the source. The amplifier control may adjust the duty cycle or phase shift of the switching elements of the amplifier 2402 to adjust the power input or output of the amplifier. The amplifier control may be communicatively coupled to the device and may adjust a duty cycle or phase shift of the amplifier based on the power delivered to the device or the power requested by the device.

In a system, the duty cycle or phase shift of the amplifier needs to be adjusted periodically or continuously as a result of changes in the amount of power delivered to or required by the device. The power required by the device may change due to changes in the coupling between the source resonator coil 2422 and the device resonator coil 2424, movement of the device, power draw by other devices, and the like. For example, if the device is far from the source, the coupling between the source resonator coil and the device resonator coil may decrease. Due to the distance, the power delivered to the device resonator coil 2424 is reduced. To maintain a specified power delivered to the device, the amplifier control may increase the duty cycle of the switching elements of the amplifier to deliver more power at the output of the source resonator coil.

In the exemplary embodiment shown in fig. 24, the source may include an impedance matching control 2412 that makes one or more measurements of AC voltage and AC current 2418 at the output of the amplifier 2402. By measuring the waveform characteristics at the amplifier output, the amplifier control 2410 may adjust the switching elements of the amplifier 2402 to achieve zero voltage switching at the switching elements of the amplifier 2402. The measurement of the waveform characteristics may be used by the impedance matching control to determine the resonant frequency of the source. The components of the IMN may be adjusted so that the resonant frequency substantially reaches the switching frequency of the amplifier. The measurement of the waveform characteristics may be used by the impedance matching control to determine a value for a tunable element of the impedance matching network that adjusts the power input or output of the amplifier to a desired degree with improved amplifier efficiency.

In embodiments, the amplifier control and the impedance matching control may be physically the same controller, or may be separate circuits or blocks. Those skilled in the art will appreciate that there are various ways in which a control block having the functionality described herein can be implemented. In an embodiment, the control may be implemented using analog circuitry, which implements comparators, sensors, and the like. In embodiments the control may be implemented in digital hardware, e.g. FPGA, microcontroller, ASIC, etc.

The devices of the system may include an impedance matching network 2406 and a tunable rectifier 2408. The oscillating voltage induced on the resonator coil may be passed through an impedance matching network 2406 and rectified to a substantially DC voltage and current at the rectifier output 2408 to power a load, such as a battery, an electronic device, or the like. The rectifier may be a controlled zero voltage switching rectifier, with a tunable duty cycle or phase shift of the switching elements, and may be used to control the output voltage or output current delivered to the device load.

The tunable elements of the switching mode rectifier may be controlled by means of a feedback loop in the device. The rectifier control 2414 may take one or more measurements of the voltage and current of the device and adjust the duty cycle or phase shift of the switching elements of the rectifier. In an embodiment, the rectifier control may measure the DC voltage and current output at the rectifier 2420. In an embodiment, the duty cycle and/or phase shift of the switching elements of the rectifier may be controlled and/or adjusted to achieve a constant voltage at the load or rectifier 2420 output. In an embodiment, the duty cycle and/or phase shift of the switching sources of the rectifier may be controlled and/or adjusted to achieve a substantially constant current at the load or rectifier 2420 output.

In a wireless energy transfer system, the voltage and/or current at the output of the load or rectifier 2420 may require periodic or even continuous adjustment due to changes in load parameters. In an embodiment, the power requirements of the load may be changed periodically or continuously. In an exemplary embodiment where the load is a battery, the power requirements may change continuously as the state of charge of the battery changes. As the battery discharges, the battery may require a constant current during its initial charge cycle, but as the battery is charged, the current requirements may decrease. In the system, the rectifier control device 2414 may adjust the duty cycle and/or phase shift of the switching elements of the rectifier to provide the desired voltage and/or current to the load.

In a system, the duty cycle and/or phase shift of the rectifier may require periodic or constant adjustment as a result of changes in the amount of power received from the source. As the source outputs less power, changes in coupling between the source resonator coil 2422 and the device resonator coil 2424, movement of the device, conditions or power draw of other devices in the system, etc., the power delivered to the device resonator coil 2424 can change. For example, if the device is far from the source, the coupling between the source resonator coil and the device resonator coil may decrease. Due to the distance, the power delivered to the device resonator coil 2424 is reduced. To maintain the voltage, current, or power output at the load despite variations in the power delivered to the device resonator coil, the rectifier control may increase the duty cycle of the switching elements of the rectifier to allow a greater percentage of the power captured at the device resonator coil to flow to the load.

In an embodiment, the rectifier control is communicatively coupled to a source of the system. In an embodiment, the rectifier control may signal the source to increase or decrease its power output based on the voltage and current at the rectifier output, or an operating parameter of the rectifier. If the rectifier is outside or near its maximum operating range, its duty cycle or phase shift cannot be increased to meet the power requirements of the load, the device may signal the source to output more power. In an embodiment, the rectifier control may signal to the source to output more power when the rectifier is near 50% duty cycle or near 40% duty cycle or less. In an embodiment, the rectifier may signal to the source to reduce its output power. In an embodiment, when the rectifier is operating at a 40% or lower duty cycle, or 30% or lower duty cycle, the device will receive more power than it needs to meet the load power requirements. In an embodiment, additional circulating power in the device and source resonator coil may result in a reduction in energy transfer efficiency. In an embodiment, the device rectifier control may signal to the source to reduce the source power output to match the power requirements at the load.

In an embodiment, the system may adjust the power output at the source to enable the rectifier at the device to operate at substantially 50% duty cycle or between 40% and 50% duty cycle to meet the power requirements of the load at the device. Operating the rectifier at a duty cycle near 50% may allow the rectifier to be more efficient and reduce losses due to additional circulating current in the source or device resonator coils and components. In an embodiment, the device may periodically signal the source to adjust the power output of the source. In an embodiment, the device may periodically signal the source to identify its power requirements and allow the source to determine the most appropriate power output power.

In some embodiments, the device may include detuning capabilities. In an embodiment, if the device receives too much power, or more power than it needs, the device may detune its resonant frequency away from the resonant frequency of the source to reduce the power delivered to the device. In some systems, a device may first attempt to communicate its power requirements to the source and wait for the source to reduce its power output. If, however, the source power output is not reduced after a specified period of time, the device may detune its resonant frequency to reduce the energy it captures. A device may detune its resonant frequency by adjusting one or more components in its impedance matching network. In an embodiment, the return of the power requirement to the source and the detuning of the device resonant frequency may be performed based on the measured load power requirement and parameters of the rectifier required to meet the load power requirement. If the rectifier is operating at less than 30% duty cycle and meets the power requirements of the load, the rectifier control may detune the device or communicate to the source to reduce its power output.

FIG. 25 shows a system embodiment in a more detailed representation of system elements. The source may include a switching amplifier 2402 and an impedance matching network 2404. The amplifier may be a switched half-bridge amplifier having two switching elements S1 and S2. The switching elements may be any number of types of switches including Field Effect Transistors (FETs), BJTs, electromechanical switches, and the like. The switch may be periodically turned on and off at a fixed frequency to change the DC input voltage and current to an oscillating voltage and current at the output of the amplifier. The switching frequency and duty ratio of the switching elements S1 and S2 may be controlled by the amplifier control device 2410. Those skilled in the art will appreciate that the amplifier may comprise four or more switching elements and may comprise a full bridge topology.

The impedance matching network 2404 may include a network of inductor L2 and capacitors C6, C5, C4 in series and a parallel configuration with the source resonator coil 2422. The topology of the elements of the impedance matching network may be designed and adjusted to the operational requirements of the system. The network may be designed to reduce the current or peak voltage across the capacitors in some systems. In other systems, the network may be designed to minimize the number of components in the network.

In an embodiment, impedance matching network 2404 may include one or more tunable components. In an embodiment, the network 2404 may include tunable capacitors C5, C4 in parallel with the resonator coil 2422. The tunable capacitance may comprise one or more capacitor banks that may be connected or disconnected from the circuit using one or more electronically controllable switches. For example, in fig. 25, the parallel capacitance can be adjusted by connecting or disconnecting the connecting capacitor C5 using an electronically controllable switch S3. The change in capacitance may be used to tune the resonant frequency of the source to correct for any perturbations or changes to the resonant frequency of the source. In an embodiment, capacitive tuning may be used to keep the resonant frequency of the source substantially at the fixed frequency of the system. In an embodiment, capacitance tuning may be used to adjust the power input or output of an amplifier with improved amplifier efficiency.

The impedance matching network may have other tunable elements such as inductors, other capacitors, resistors, and the like. The elements may be adjusted by switching elements such as in capacitor C5 in fig. 25. The switching elements may be electronically controlled by an impedance matching control 2412, which may change capacitance by connecting or removing one or more capacitors for the circuit.

The impedance matching network 2406 of the device may include a network of capacitors and inductors that set the resonant frequency of the device and impedance match the resonator coil 2424 to the rectifier 2408. The rectifier 2408 may include at least one active switching element. One or more switching elements S4, S5 may be synchronized with the oscillating voltage at the input of the rectifier and may be turned on and off to substantially rectify the oscillating voltage and current into DC voltage and current at the output of the rectifier. The switches are preferably electronically controlled switches, such as transistors controlled by a rectifier control 2414. The rectifier control 2414 may control a switching characteristic, such as a duty cycle of the switch, to control the output voltage or current at the rectifier output. In an embodiment, the rectifier may include one or more filters to smooth or reduce the output ripple of the output voltage. The filter may be one or more capacitors, or any number of other passive and active filtering topologies.

In an embodiment, the amplifier topology and the rectifier topology may be based on the full bridge design shown in fig. 26. In a full bridge topology of the source, the amplifier 2402 may include four switching elements S1, S2, S3, S4. In the full-bridge topology, the impedance matching network 2404 is preferably symmetric around the resonator selection 2422. The elements of the impedance matching network may be identical at both outputs of the amplifier. For example, inductor L2 may be duplicated to two outputs as L2a and L2b in the exemplary network. The symmetric impedance matching network may include tunable components, such as capacitor banks, that may be switched in and out of the circuit. In an embodiment, the switchable capacitor banks may also be symmetric, e.g. C5a and C5b, and switched using symmetric switches S5, S6 around the circuit center point.

Exemplary system embodiments with tunable source amplifiers and tunable device rectifiers have important advantages for wireless energy transfer to mobile or transportable devices or for systems with more than one device. In embodiments with more than one device, a source with fixed or constant switching and output frequency allows more than one device to receive power simultaneously. Tuning of the source impedance matching network is necessary to maintain the resonant frequency of the source as the device moves and changes the load and disturbance on the source resonator coil.

While the invention has been described in connection with certain preferred embodiments, those skilled in the art will understand that other embodiments are also intended to be within the scope of the disclosure, which should be construed in the broadest sense permitted by law.

All documents mentioned herein are incorporated by reference herein in their entirety as if fully set forth herein.

Claims (12)

1. A wireless energy transfer system for transferring energy between a power source and a load, comprising:

a source resonator coil;

a device resonator coil inductively coupled to the source resonator coil;

a tunable switching amplifier configured to be driven by the power supply and to drive the source resonator coil through a source impedance matching network, the switching amplifier having electronically controllable switching elements;

a tunable switching rectifier configured to drive the load and receive energy from the device resonator coil through a device impedance matching network, the switching rectifier having electronically controllable switching elements;

a source amplifier control device configured to control a switching characteristic of the switching element of the amplifier to regulate power extracted from a power supply; and

a rectifier control configured to control switching characteristics of the switching elements of the rectifier to adjust characteristics of an output provided to the load, the rectifier control configured to be communicatively coupled to the source amplifier control;

wherein, during operation of the system:

the source amplifier control device is configured to provide a fixed switching frequency to the switching elements of the amplifier;

the source amplifier control device is configured to control at least one dead time of the switching characteristic of the switching element of the amplifier to maintain zero voltage switching;

at a maximum load power level, impedance matching is achieved throughout the wireless energy transfer system such that the tunable switching amplifier maintains zero current switching and provides a predetermined output dc voltage to the load; and

the source amplifier control device is configured to reduce the output power level of the tunable switching amplifier by reducing the duty cycle of the switching elements of the tunable switching amplifier when the power requirement of the load is less than the maximum load power level, thereby losing zero current switching and maintaining the impedance match throughout the wireless energy transfer system.

2. The system of claim 1, wherein the amplifier has a half-bridge topology.

3. The system of claim 1, wherein the amplifier has a full-bridge topology and the source amplifier control device is configured to control the phase of the switching elements of the amplifier.

4. The system of claim 1, wherein the rectifier has a half-bridge topology and the rectifier control is configured to control a switching duty cycle of the switching elements of the rectifier.

5. The system of claim 1, wherein the rectifier has a full bridge topology and the rectifier control is configured to control switching phases of the switching elements of the rectifier.

6. The system of claim 1, wherein the at least one dead time is controlled in response to measurements of an output voltage and an output current of the amplifier.

7. The system of claim 1, wherein during operation of the system, the rectifier control device is configured to control at least one dead time of the switching characteristic of the switching element of the rectifier to maintain zero voltage switching.

8. The system of claim 7, wherein the at least one dead time of the switching characteristic of the switching element of the rectifier is controlled in response to measurements of an output voltage and an output current of the amplifier or the rectifier.

9. The system of claim 1, wherein the source impedance matching network comprises at least one tunable element.

10. The system of claim 9, wherein the at least one tunable element is an adjustable capacitor.

11. The system of claim 10, wherein during operation of the system, the source amplifier control device is configured to adjust the capacitor to maintain the source resonant frequency.

12. A method for controlling energy transfer to a load in a wireless energy transfer system, the method comprising:

providing a source with a tunable switching amplifier comprising a controllable switching element;

providing a tunable switching rectifier for a device, the tunable switching rectifier including a controllable switching element, the rectifier communicatively coupled to the amplifier of the source;

using a source amplifier control device to provide a fixed switching frequency to the switching elements of the tunable switching amplifier; and

controlling at least one dead time of the switching elements of the tunable switching amplifier to maintain zero voltage switching,

wherein at a maximum load power level, impedance matching is achieved throughout the wireless energy transfer system while maintaining zero current switching, and a predetermined output DC voltage is provided at the load; and

wherein when the power requirement of the load is less than the maximum load power level, the method further comprises reducing the output power level of the tunable switching amplifier by reducing the duty cycle of the switching element of the tunable switching amplifier, thereby losing zero current switching and maintaining the impedance match throughout the wireless energy transfer system.