HK40038866A

HK40038866A - Wireless power transfer to multiple receiver devices across a variable-sized area

Info

Publication number: HK40038866A
Application number: HK42021028620.9A
Authority: HK
Inventors: R·莫法特; J·延
Original assignee: 爱泽达恩技术有限公司
Priority date: 2016-10-18
Filing date: 2020-04-07
Publication date: 2021-07-02

Description

Wireless power transfer to multiple receiver devices over variable-size regions

The present application is a divisional application of the invention patent application having application number 2017800646720 entitled "wireless power transmission to multiple receiver devices over an area of variable size", filing date 10, month 17, 2017.

Background

Wireless power transfer is the transfer of electrical energy from a power source to an electrical load without using artificial conductors to connect the power source to the electrical load. A wireless power transfer system includes a transmitter and one or more receiver devices. The transmitter is connected to a power source and converts the power into a time-varying electromagnetic field. One or more receiver devices receive power via an electromagnetic field and convert the received power back into electrical current for use by an electrical load.

Disclosure of Invention

In general, in one aspect, the invention relates to a method for wireless power transfer. The method includes adapting a variable form factor transmitter to an adaptation form factor based on a predetermined wireless power transfer region, wherein the variable form factor transmitter in the adaptation form factor includes a characteristic frequency, maintaining the characteristic frequency substantially independent of the adaptation form factor, and transferring RF power over the predetermined wireless power transfer region via a near electromagnetic field of the variable form factor transmitter from a Radio Frequency (RF) power source and based at least in part on the characteristic frequency.

In general, in one aspect, the invention relates to a variable form factor transmitter for wireless power transfer. The variable form factor transmitter comprises a plurality of capacitors, each capacitor having a predetermined capacitance and a plurality of line segments, each line segment having a predetermined segment length and a predetermined inductance per unit length, wherein the plurality of capacitors are connected in series via at least the plurality of conductor segments into a string of distributed capacitors, wherein the string of distributed capacitors is adapted to an adaptation form factor based on a predetermined wireless power transfer region, wherein the string of distributed capacitors in the adaptation form factor comprises a characteristic frequency that is substantially independent of the adaptation form factor, and wherein the variable form factor transmitter is configured to transmit RF power over the predetermined wireless power transfer region via a near electromagnetic field of the string of distributed capacitors from a Radio Frequency (RF) power source and based at least in part on the characteristic frequency.

In general, in one aspect, the invention relates to a system for wireless power transfer. The system includes a Radio Frequency (RF) power source and a variable form factor transmitter that is adaptable to an adaptation form factor based on a predetermined wireless power transfer region, wherein the variable form factor transmitter in the adaptation form factor includes a characteristic frequency, and wherein the variable form factor transmitter is configured to maintain the characteristic frequency substantially independent of the adaptation form factor and to transmit RF power over the predetermined wireless power transfer region via a near electromagnetic field of the variable form factor transmitter from the RF power source and based at least in part on the characteristic frequency.

Other aspects of the invention will become apparent from the following description of the transaction and the appended claims.

Drawings

Fig. 1A, 1B, and 1C show schematic diagrams of an example system with a variable form factor transmitter in accordance with one or more embodiments of the invention.

Fig. 2A, 2B, 2C, 2D, 2E, 2F, 2G, and 2H illustrate schematic diagrams for illustrating an example variable form factor transmitter in accordance with one or more embodiments of the present invention.

Fig. 3A, 3B, 3C, 3D, and 3E illustrate example characteristics of an example variable form factor transmitter in accordance with one or more embodiments of the invention.

FIG. 4 shows a schematic diagram of an example Radio Frequency (RF) power supply in accordance with one or more embodiments of the invention.

Fig. 5A, 5B, and 5C show schematic diagrams of an example receiver device in accordance with one or more embodiments of the invention.

FIG. 6 shows a flow diagram in accordance with one or more embodiments of the invention.

Detailed Description

Specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings. Like elements in the various figures are denoted by like reference numerals for consistency. Furthermore, in the figures, three or more collinear points means that there may optionally be more elements of the same type as three or more collinear points in accordance with one or more embodiments of the present invention.

In the following detailed description of embodiments of the invention, numerous specific details are set forth in order to provide a more thorough understanding of the invention. It will be apparent, however, to one skilled in the art that the present invention may be practiced without these specific details. In other instances, well-known features have not been described in detail to avoid unnecessarily complicating the description of the transaction.

In general, embodiments of the invention provide methods, transmitter devices and systems for wireless power transfer. In one or more embodiments of the invention, the method, transmitter device and system provide functionality for adapting a variable form factor transmitter to a particular form factor (referred to as an adaptation form factor) based on a predetermined wireless power transfer area. In particular, the variable form factor transmitter in the adaptation form factor has a characteristic frequency that is kept substantially independent of the adaptation form factor. Thus, RF power is transmitted from a Radio Frequency (RF) power source and based at least in part on a characteristic frequency via a near electromagnetic field of a variable form factor transmitter across a predetermined wireless power transfer region. In one or more embodiments of the invention, the characteristic frequencies are within the industrial, scientific, and medical (ISM) radio frequency band defined by the International Telecommunications Union (ITU) radio rules. For example, within the class a frequency range specified in ITU "radio rules" article 5, footnote 5.138 (i.e., 6.765MHz-6.795MHz), the characteristic frequency may be maintained as the adaptation form factor changes.

FIG. 1A shows a schematic diagram of an example system (100) in accordance with one or more embodiments of the invention. In one or more embodiments, one or more of the modules and elements shown in fig. 1A may be omitted, repeated, and/or replaced. Accordingly, embodiments of the present invention should not be considered limited to the particular arrangement of modules shown in FIG. 1A.

As shown in fig. 1A, the system (100) includes a variable form factor transmitter (102) that receives power from an RF power source (108) for wireless power transfer across a wireless power transfer region (101) having one or more receiver devices disposed therein (e.g., represented by the circular icons labeled A, B, C, D, E and F). Each of these components is described in detail below.

In one or more embodiments of the invention, the wireless power transfer region (101) is any three-dimensional (3D) physical space in which one or more receiver devices receive power from a variable form factor transmitter (102). For example, the wireless power transfer area (101) may comprise a 3D space within a building or vehicle, such as a room, hallway, passenger cabin of a car, bus, train, airplane or spacecraft, or any part of a building or vehicle. In another example, the wireless power transfer area (101) may include an unenclosed 3D space, such as a game floor, a road, an amusement park, or any type of floor on the ground, above the ground, or away from the earth in space (e.g., the atmosphere or interplanetary space). In yet another example, the wireless power transfer region (101) may include an underground or underwater space, such as a cavern, an underwater region near a sea platform or sea bed, or the like. In yet another example, the wireless power transfer region (101) may comprise a combination of the above examples.

In one or more embodiments of the invention, the variable form factor transmitter (102) is disposed entirely within the wireless power transfer region (101), overlapping the wireless power transfer region (101), or near the wireless power transfer region (101). In one or more embodiments, at least a portion of the variable form factor transmitter (102) may be inserted into a protective sleeve, embedded in a sheet of material, placed separately in the wireless power transfer region (101), or attached to the wireless power transfer region (101). In one or more embodiments, at least a portion of the variable form factor transmitter (102) may be fixed or movable relative to the wireless power transfer region (101) and/or one or more receiver devices disposed therein (e.g., represented by the circular icons labeled A, B, C, D, E and F). In one or more embodiments of the invention, the form factor of the variable form factor transmitter (102) is adapted according to geometric constraints imposed by the wireless power transfer region (101). For example, the variable form factor transmitter (102) may be made of a pliable material such that the form factor of the variable form factor transmitter (102) is changed by a user to fit the physical shape of a room, hallway, passenger cabin, amusement park, field, cave, underwater area, etc. of the wireless power transfer area (101). For example, the form factor of the variable form factor transmitter (102) may include a 3D portion, such as a curved surface, a spiral curve, or the like.

In one or more embodiments of the invention, the receiver devices (a) to (F) may be of the same type or different types used by one or more users (e.g., individuals). In one or more embodiments, one or more of the receiver devices (a) through (F) are disposed at user-specified locations throughout the wireless power transfer region (101) and are stationary during wireless power transfer. In one or more embodiments, one or more of the receiver devices (a) through (F) have a size that is less than a size of the wireless power transfer region (101). In one or more embodiments, one or more of the receiver devices (a) through (F) have a size comparable to or larger than the size of the wireless power transfer region (101). For example, the receiver device (a) may be a lighting device placed by a user on the ceiling of a room or corridor. In one or more embodiments, one or more of the receiver devices (a) through (F) are carried by respective users moving around in the wireless power transfer area (101) from time to time during wireless power transfer. Based on the nature of the near-electromagnetic field of the variable form factor transmitter (102), power of the near-electromagnetic field not received by any receiver device is returned to the variable form factor transmitter (102) and the RF power supply (108). This is in contrast to the remote electromagnetic field via which the radiated power results in energy losses, which are ineffective for wireless power transfer. Examples of the receiver device (a), the receiver device (B), the receiver device (C), the receiver device (D), the receiver device (E), and the receiver device (F) are described below with reference to fig. 5A, 5B, and 5C.

In one or more embodiments of the invention, the variable form factor transmitter (102) includes a string of distributed capacitors. In particular, the string of distributed capacitors includes a plurality of capacitor line segments connected in series to conduct a Radio Frequency (RF) current (105) generated by a power source (108). The RF current (105) induces a magnetic field (e.g., magnetic field (106)) that exists throughout the wireless power transfer region (101). In one or more embodiments, RF current (105) enters/exits the wire at terminal a (107a) and terminal B (107B). In one or more embodiments, additional intermediate components (not shown) may also be inserted in the series of capacitor line segments or between the series of capacitor line segments and one or more terminals (e.g., terminal a (107a), terminal B (107B)) without interfering with the operation of the variable form factor transmitter (102).

In one or more embodiments, each capacitor line segment includes a capacitor (e.g., capacitor (103)) connected to the line segment (e.g., line segment (104)). In one or more embodiments, each capacitor (e.g., capacitor (103)) in the variable form factor transmitter (102) has the same nominal capacitance value as any other capacitor therein, which is determined prior to placement of the variable form factor transmitter (102) in the wireless power transfer region (101). For example, a capacitor (e.g., capacitor (103)) in the variable form factor transmitter (102) may be installed in the factory before the user uses the variable form factor transmitter (102) to wirelessly provide power within the wireless power transfer area (101). The capacitor (e.g., capacitor (103)) may be of a suitable type, such as a ceramic capacitor, a film and paper capacitor, an electrolyte capacitor, a polymer capacitor, a silver mica capacitor, and the like. In one or more embodiments, one or more capacitors may include two aluminum or other metal sheets, foils, or films separated by an aluminum or other metal oxide layer. As is typical in factory manufacturing processes, the capacitance values of all capacitors (e.g., capacitor (103)) in the variable form factor transmitter (102) may vary over a range (referred to as a capacitance range), for example, due to manufacturing tolerances.

In one or more embodiments, each capacitor line segment comprises a line segment having a predetermined segment length and a predetermined inductance per unit length. For example, a line segment (e.g., line segment (104)) in the variable form factor transmitter (102) may be installed in the factory before the user uses the variable form factor transmitter (102) to wirelessly provide power within the wireless power transfer area (101). The wire segments (e.g., segment (104)) may be of a suitable type, such as insulated or non-insulated wires, sheets, foils, or films, made of copper, aluminum, or other suitable metal and/or alloy materials. In one or more embodiments, one or more line segments (e.g., line segment (104)) are flexible or pliable such that a user can bend, stretch, or otherwise change the shape of the one or more line segments. As is typical in factory manufacturing processes, the length and inductance values of each and all of the line segments (e.g., line segment (104)) in the variable form factor transmitter (102) may vary over a range, referred to as a length range and an inductance range, for example, due to manufacturing tolerances.

In one or more embodiments of the invention, a capacitor (e.g., capacitor (103)) in the variable form factor transmitter (102) reduces stray electric fields and a resultant induced voltage of a line segment (e.g., line segment (104)) by limiting the electric field. Thus, the capacitor (e.g., capacitor (103)) in the variable form factor transmitter (102) reduces the proportion of energy stored in the stray capacitance of the line segment (e.g., line segment (104)) relative to the total energy in the system (100). The reduction in induced voltage and stored energy associated with stray capacitance reduces losses due to environmental interactions and improves user safety.

In one or more embodiments of the invention, the variable form factor transmitter (102) is associated with a characteristic frequency that is based on at least a predetermined capacitance, a predetermined segment length, and a predetermined inductance per unit length. The characteristic frequencies of the variable form factor transmitter (102) are described below with reference to fig. 2A, 2B, 2D, 2E, 3A, 3B, 3C, 3D, and 3E. Throughout this document, the terms "characteristic frequency" and "resonant frequency" may be used interchangeably depending on the context.

In one or more embodiments, instead of a direct connection to the power source (108), the variable form factor transmitter (102) receives power from the power source (108) via the drive loop (109a) using inductive coupling. Fig. 1B shows a schematic diagram of an example system (100) in an inductively coupled power configuration. Details of the power received by the drive loop (109a) are described below with reference to fig. 1C.

Fig. 1C shows a schematic diagram of power supply via the drive circuit (109a) depicted in fig. 1B above. In one or more embodiments, one or more of the modules and elements shown in fig. 1C may be omitted, repeated, and/or replaced. Accordingly, embodiments of the present invention should not be considered limited to the particular arrangement of modules shown in FIG. 1C.

As shown in FIG. 1C, the drive loop (109a) includes one or more conductor loops (e.g., having an inductance L)₁) Coupled to a power source (108) via a balun (108 a). The balun (108a) includes a tuning capacitor a (109d) (e.g., having a variable capacitance C)₁) Tuning capacitor B (109e) (e.g., having variable capacitance C)₂) And a coaxial cable (109c) (e.g., wound around a ferrite core (109 b)) and having an inductance L₂). Specifically, the drive loop (109a) is placed at a distance (110) from the variable form factor transmitter (102) such that the power source (108) powers the variable form factor transmitter (102) through electromagnetic coupling across the distance (110). In one or more embodiments, the tuning capacitor B (109e) is tuned to the inductance L of the ferrite core (109B)₂Resonates to form a parallel resonant LC circuit, which imposes a high impedance between the two opposite ends of the coaxial cable (109 c). Furthermore, the tuning capacitor a (109d) is used to tune the resonant frequency of the drive loop (109a) to match the frequency of the RF power supply (108). The distance (110) between the drive loop (109a) and the variable form factor transmitter (102) may be adjusted to match the apparent input impedance of the variable form factor transmitter (102) to the impedance of the coaxial cable (109c) and the output impedance of the RF power supply (108).

Fig. 2A shows a schematic diagram of a parallel line transmission line (201) according to one or more embodiments of the invention. In one or more embodiments, one or more of the modules and elements shown in fig. 2A may be omitted, repeated, and/or replaced. Accordingly, embodiments of the present invention should not be considered limited to the particular arrangement of modules shown in FIG. 2A.

As shown in fig. 2A, sinusoidal icons (201a) and (201b) represent electromagnetic waves propagating along parallel line transmission lines (201). The parallel line transmission line (201) is made up of two parallel lines (201d), each line having line segments connected by capacitors, where s represents the length of each line segment, C represents the capacitance of each capacitor, and q represents the displacement of charge along the parallel line transmission line (201). In the case where two parallel lines (201d) conduct RF current, such as current (105) shown in fig. 1A, each of the two parallel lines (201d) is also referred to as a wire throughout the document. The distance between the sinusoidal icons (201a) and (201b) corresponds to the length of the parallel line transmission line (201), and the spacing between two parallel series of capacitors corresponds to the width of the parallel line transmission line (201). The width of the parallel line transmission line (201) may range from less than 1 centimeter to the width or other dimension of the wireless power transfer region (101), although the length of the parallel line transmission line (201) may be comparable to the length of other dimensions of the wireless power transfer region (101). In one or more embodiments, the parallel line transmission line (201) corresponds to a portion of the variable form factor transmitter (102) depicted in fig. 1A above. In other words, the two line segments of the string of distributed capacitors depicted in fig. 1A may be arranged parallel to each other. In general, the charge q displaced along a parallel line transmission line (201) is a function of position and time along the parallel line transmission line (201). Corresponding charge density (i.e., charge per unit length) ρ_λAnd the current I is given by equation (1) below for a parallel line transmission line (201). In equation (1), x and t represent the position and time, respectively, along a parallel line transmission line (201).

Table 1 shows other definitions of the variables used in the equations in this document.

TABLE 1

c is capacitance per unit length

Inductance per unit length

C-capacitance of each connected capacitor

s-length of each segment

q-charge displacement

ρ_λDensity of charge

λ ═ wavelength in free space

I is current

U_jEnergy stored in two connected capacitors

u_EElectric energy stored per unit length

u_BMagnetic energy stored per unit length

v-asymptotic velocity

ω₀Cut-off frequency

v_pPhase velocity

v_gGroup velocity

Electrical energy U stored in a pair of adjacent capacitors (e.g., capacitor pair (201c)) in a parallel line transmission line (201)_jGiven by equation (2) below.

In the case of a spatial variation where s is substantially smaller than q, the energy stored U_jThe division by the length s of the segment can be considered as the energy density stored in the capacitor C along the parallel line transmission line (201). Let c denote the stray capacitance per unit length between two parallel lines of the parallel line transmission line (201). Total electrical energy u stored per unit length along a parallel line transmission line (201)_EGiven by equation (3) below.

Total magnetic energy u stored per unit length along a parallel line transmission line (201)_BGiven by equation (4) below.

Thus, the lagrangian of the parallel line transmission line (201) is given by the following equation (5).

The generalized momentum pi, the Euler-Lagrange equation of motion, and the wave equation of the parallel line transmission line (201) are given by equation (6), equation (7), and equation (8) below.

Based on the fluctuation equation (8), the dispersion relation of the parallel line transmission line (201) is given by the following equations (9a), (9b), and (9 c).

In equations (9a), (9b), and (9c), ω represents angular frequency, k represents wave number, v represents the asymptotic wave velocity defined in equation (9a), and ω represents the asymptotic wave velocity₀Representing the cut-off angular frequency as defined in equation (9b). In particular, the cut-off angular frequency ω₀Independent of length and varies logarithmically with the width of the parallel line transmission line (201). In one or more embodiments, one or more line segments of an associated capacitor having parallel line transmission lines (201) are detachable. Thus, parallel line transmission lines (201) may be reconfigured by a user without substantially changing ω₀To change the total length according to the size of the wireless power transfer area (101).

Based on equation (9c), fig. 3A shows a graph of angular frequency ω versus wave number k to show the dispersion relationship of the parallel line transmission line (201). In addition, the phase velocity v_pAnd group velocity v_gGiven in equations (10a) and (10b) below.

Note that as the wave number k approaches asymptotically 0, the phase velocity v_pAsymptotic to infinity, group velocity v_gAsymptotically approaches 0, and the angular frequency ω asymptotically approaches ω₀。

Fig. 2B shows a schematic diagram of a parallel line transmission line (201) driven by an RF power supply (108) in accordance with one or more embodiments of the invention. In one or more embodiments, one or more of the modules and elements shown in fig. 2B may be omitted, repeated, and/or replaced. Accordingly, embodiments of the present invention should not be considered limited to the particular arrangement of modules shown in FIG. 2B.

As shown in fig. 2B, the parallel line transmission line (201) is driven by an RF power supply (108) connected via a terminal a (204a) and a terminal B (204B). Furthermore, the parallel line transmission line (201) is terminated (terminated) by a conductive connection (202) and is at a characteristic frequency ω₀And (5) operating. In one or more embodiments of the invention, the conductive connection (202) may be replaced by a variable capacitor or other electronic component that may be used to fine tune the characteristics of the parallel line transmission line (201)And (5) characterizing the frequency.

In one or more embodiments of the invention, the configuration of the parallel line transmission lines (201) shown in fig. 2B approximates the variable form factor transmitter (102) shown in fig. 1A above. Similar to fig. 1A, the receiver devices (e.g., represented as circular icons labeled A, B, C, D, E and F) are disposed around the parallel line transmission line (201) shown in fig. 2B. This approximation is particularly applicable where the wireless power transfer region (101) has an elongated shape and a string of distributed capacitors of the variable form factor transmitter (102) are arranged in a pair of parallel lines according to the elongated shape of the wireless power transfer region (101). As described below, the characteristic frequency of the variable form factor transmitter (102) corresponds to ω described above with reference to FIG. 2A₀And is substantially independent of length and varies logarithmically with the width of the parallel line transmission line (201).

In the configuration shown in fig. 2B, the standing wave along the parallel line transmission line (201) excited by the RF power source (108) has an infinite phase velocity. Thus, the voltage and current along the parallel line transmission line (201) are all in phase at different locations of the parallel line transmission line (201). In other words, the effective electrical length of the parallel line transmission line (201) is equal to zero regardless of the physical length of the parallel line transmission line (201). The input impedance of the parallel line transmission line (201) provided to the RF power supply (108) is equal to zero regardless of the physical length of the parallel line transmission line (201) without energy loss in the parallel line transmission line (201). In other words, the parallel line transmission line (201) is equivalent to the line at ω₀An RLC circuit (not shown) at resonance regardless of whether the physical length of the parallel line transmission line (201) is greater than the driving frequency, i.e., [ omega ]₀Is much shorter or longer (e.g., based on the transmission medium of the wireless power transfer region (101)). Thus, a parallel line transmission line (201) driven by an RF power supply (108) and terminated by a conductive connection (202) may be used as a resonant power supply for wireless power transmission to induce resonance of a receiver device placed in the vicinity of the parallel line transmission line (201). In particular, the resonant receiver device couples to and receives power from an electric and/or magnetic field generated by a standing wave of parallel line transmission lines (201).

In one or more embodiments, the resonant receiver device receives power from the near electromagnetic field of a parallel line transmission line (201). Even if the physical length of the parallel line transmission line (201) is much longer than the free space wavelength of the drive frequency (e.g., the transmission medium based on the wireless power transfer region (101)), the power provided from the RF power source (108) is substantially retained in the parallel line transmission line (201) for transmission to nearby resonant receiver devices without losing far field radiation. The quality factor of a parallel line transmission line due to radiation losses depends only on the line distance and the line radius and not on the length.

Fig. 2C shows a variant of a parallel line transmission line (201) with distributed capacitance, where one wire forms a conductive shield (203), hereinafter referred to as shielded transmission line (201a), around the other wire. For example, the conductive shield (203) may be substantially cylindrical. The shielded transmission line (201a) shown in fig. 2C operates on the same principle as the parallel line transmission line (201) shown in fig. 2B above, except that the distributed capacitance is placed only on the center conductor. In some configurations, the center conductor may not be concentric with the outer conductor (i.e., conductive shield 203). Further, the cross-section of the center conductor and the outer conductor (i.e., conductive shield 203) may not be circular.

In one or more embodiments of the invention, the configuration of the shielded transmission line (201A) shown in fig. 2C approximates the variable form factor transmitter (102) shown in fig. 1A above. Similar to fig. 1A, the receiver devices (e.g., represented as circular icons labeled A, B, C, D, E and F) are disposed around the parallel line transmission line (201) shown in fig. 2C. This approximation is particularly applicable where the wireless power transfer region (101) corresponds to an interior space within a conductive enclosure, such as within a metal pipe, fuselage of an aircraft or space shuttle, or the like. As shown in FIG. 2C, the characteristic frequency of the variable form factor transmitter (102) corresponds to ω described above with reference to FIGS. 2A and 2B₀And is substantially independent of the length of the conductive shield (203) and varies logarithmically from the diameter of the conductive shield (203). The characteristic frequency of the shielded transmission line (201a) shown in fig. 2C is given by equation (11). Note that this differs from equation (9b) by a factorSince only one wire comprises a distributed capacitor.

Figure 3B shows a graph of the quality factor Q of a parallel line transmission line of arbitrary length (e.g., as shown in figure 2A or figure 2B) consisting of 14AWG copper line driven at 14.78MHz as a function of the distance d (between the two lines) divided by the free space wavelength λ. For large line distances relative to the free space wavelength, Q is suppressed due to radiation losses. However, for small line distances compared to the free space wavelength, radiation is suppressed and losses are mainly determined by ohmic losses in the copper lines.

Note that the shielded transmission line (201) has no radiation losses due to the fact that the conductive shield (203) completely surrounds the internal electromagnetic field.

Conversely, while a wire loop driven by the RF power supply (108) (described with reference to fig. 2D below) may also transfer power to nearby resonant receiver devices, the efficiency of power transfer is reduced due to far field radiation as the size of the wire loop is increased to free space wavelengths near or beyond the drive frequency. Figure 3C shows a graph of the quality factor Q of a circular ring of 14AWG copper wire driven at 6.78MHz as a function of the ring radius a divided by the free space wavelength λ. Note that Q becomes low, and therefore the efficiency of wireless power transmission is suppressed because the loop radius becomes large with respect to the free-space wavelength.

Fig. 2D shows a schematic diagram of a wire loop (204) with distributed capacitors and driven by an RF power supply (108) in accordance with one or more embodiments of the invention. In one or more embodiments, one or more of the modules and elements shown in fig. 2D may be omitted, repeated, and/or replaced. Accordingly, embodiments of the present invention should not be considered limited to the particular arrangement of modules shown in FIG. 2D.

In one or more embodiments, the wire loop (204) has a circular loopRadius a and wire radius (corresponding to the gauge of the wire) b (not shown) and is made up of a plurality of capacitor C connected segments of length s. In one or more embodiments of the invention, the configuration of the wire loop (204) shown in fig. 2D approximates the variable form factor transmitter (102) depicted in fig. 1A above. The approximation is particularly suitable for the case where the specific shape of the wireless power transfer region (101) matches the circular form factor of the variable form factor transmitter (102). As described below, the characteristic frequency of the variable form factor transmitter (102) corresponds to the resonant frequency ω of the wire loop (204)₀And substantially independent of the width and/or length (i.e., form factor) of the wire loop (204).

Inductance L and total capacitance C of wire loop (204)_totAnd resonant angular frequency ω₀Given by equation (12a), equation (12b), and equation (12c) below.

In equations (12a), (12b), and (12C), N represents the number of line segments or capacitors C in the wire loop (204), and μ represents the electromagnetic permeability of the transmission medium in the wireless power transmission region (101). In one or more embodiments, the resonant angular frequency ω₀Depends only weakly on the radius a or the wire radius b of the wire loop (204). In one or more embodiments, one or more wire segments of an associated capacitor having a wire loop (204) are detachable. Thus, depending on the size of the wireless power transfer area (101), the user may reconfigure the wire loop (204) without substantially changing the resonance angular frequency ω₀To change the loop radius a.

With the parallel line transmission line (2) shown in figure 2A above01) Instead, the wire loop (204) becomes an effective far-field radiator because the radius a becomes equal to the drive frequency, i.e., ω₀Comparable to or exceeding its free space wavelength (e.g., a transmission medium based on a wireless power transmission region (101)). Radiation resistance (i.e., effective series resistance due to far field radiation) R of closed loop wire carrying uniform current_radGiven by the double integral over the wire path, as given by equation (13a) below.

In equation (13a), based on the transmission medium of the wireless power transmission region (101),is the impedance of free space and k is the free space wavenumber. Based on equation (13a) applied to the wire loop (204), fig. 3D shows a plot of the radiation resistance divided by the impedance of free space as a function of radius divided by wavelength. As can be seen from fig. 3D, the radiation resistance has an asymptotic form of the large and small loop radii given in equation (14) below.

The quality factor Q of the loop caused by radiation is equal to the inductive reactance omega₀L divided by the total series resistance R (which includes the radiated power)Resistance R_rad) The ratio of (a) to (b). As the radiation resistance increases, the quality factor decreases, resulting in a decrease in the efficiency of wireless power transfer.

For the circular wire loop (204) shown in fig. 2D, equation (12c) applies,where a is the ring radius and b is the line radius. For the parallel line transmission line (201) shown in fig. 2B, equation (9B) applies and may showWhere d is the width of the parallel line transmission line and b is the line radius. If ln (a/b) ≈ ln (d/b), the characteristic frequency ω₀With similar values for the circular loop and parallel line configurations. In this manner, a single variable form factor transmitter (102) may be manufactured for use in both an elongated shaped service area and a circular shaped service area based on a user adapted elongated form factor or circular form factor. In other words, based on the wire radius b used to fabricate the variable form factor transmitter (102), the user can select the loop radius a and the wire transmission line width d such that ln (a/b) ≈ ln (d/b). In this manner, a single variable form factor transmitter manufactured at the factory may be configured as a parallel line form factor depicted in FIG. 2B or a circular form factor depicted in FIG. 2D to tune to a particular resonant frequency ω₀The same set of receiving devices.

Fig. 2E shows a schematic diagram of a rectangular ring (206) with distributed capacitors and driven by an RF power supply (108) in accordance with one or more embodiments of the invention. In one or more embodiments of the invention, the configuration of the rectangular annulus (206) approximates the variable form factor transmitter (102) depicted in fig. 1A above. Similar to fig. 1A, the receiver devices (e.g., represented as circular icons labeled A, B, C, D, E and F) are disposed around the rectangular ring (206) shown in fig. 2E. For example, the rectangular ring (206) may correspond to the parallel transmission shown in FIG. 2BA transmission line (201) that has been adapted by a user to fit a rectangular wireless power transmission area. In another example, the rectangular loop (206) may correspond to the loop of wire (204) shown in fig. 2D, which has been adapted by a user to fit a rectangular wireless power transfer area. As shown in fig. 2E, the rectangular ring (206) is driven by the RF power supply (108) using a transformer coupling scheme. In particular, the transformer (206a) comprises a primary winding L₁Parallel capacitor C₂And a secondary coil L₁Parallel capacitor C₁. In addition, the conductive connection (202) shown in FIG. 2B is made by capacitor C₂Instead. Capacitor C₁、C₂And C₃May be adjusted at the factory and/or by the user for impedance matching between the power supply (108) and the rectangular loop (206) and for tuning the resonant frequency of the rectangular loop (206).

Fig. 2F shows a schematic diagram of connecting the power supply (108) using a capacitive coupling scheme. In particular, the power supply (108) is at the tuning capacitor C₁Is connected to the distributed capacitor string (207) via a coaxial cable (208) and a twisted pair (209). The tuning capacitor C can be adjusted in factor or by the user₁To provide proper impedance matching to the RF power supply (108) and the coaxial cable (208). By attaching the shield of the coaxial cable (208) to the voltage node of the distributed capacitor string (207), the outer connector of the coaxial cable (208) is held at ground potential.

In one or more embodiments, the distributed capacitor string (207) may correspond to a portion of a parallel line transmission line (201) shown in fig. 2B and 2C, a portion of a wire loop (204) shown in fig. 2D, or a portion of a rectangular loop (206) shown in fig. 2E. The magnitude (210) of the voltage relative to ground induced by the power supply (108) is shown as a function of position along the distributed capacitor string (207).

Fig. 2G shows a schematic diagram of connecting a power supply (108) to a variable form factor transmitter using an alternative capacitive coupling scheme. As shown in fig. 2G, a resonant balun (211) is used to connect the power supply (108) to the tuning capacitor C₁。

Fig. 3E is a graph of inductance as a function of aspect ratio (represented by width/half perimeter) of a rectangular loop (e.g., rectangular loop (206) shown in fig. 2E above) (made of 83 feet of 14AWG wire and driven at 6.78 MHz). The rectangular rings with the aspect ratio ranges shown in fig. 3E represent various shapes, and the wire ring (204) shown in fig. 2D may be adjusted by the user to fit any wireless power transfer area. The graph shows the inductance of a rectangular loop when the circumference (i.e., the circumference corresponding to the wire loop (204)) remains fixed but the aspect ratio is varied. It can be seen from the figure that the inductance varies by less than 20% when the aspect ratio varies over a wide range between 0.05 and 0.95. Thus, the characteristic frequency of the wire loop (204) varies by less than 10% while fitting into a rectangular loop of a wide range of aspect ratios. This demonstrates the relative insensitivity of the resonant frequency of the loop with distributed capacitance to adapting to changes in the form factor.

Referring back to the discussion of fig. 1A, in one or more embodiments of the invention, the system (100) provides wireless power transfer across the wireless power transfer region (101) based on the ISM band. In the case where the variable form factor transmitter (102) is approximated by a parallel line transmission line (201) as shown in fig. 2A, 2B or 2C, the value of the line segment length s, the inductance per unit length l, and the capacitor C may be selected in the factory based on equation (9B) to maintain the resonant angular frequency ω of the parallel line transmission line (201)₀Equal to the angular frequency of the RF power source, which may be in the class a frequency range defined in international union "radio rules" article 5, footnote 5.138 (i.e., 6.765MHz-6.795 MHz).

In the case of a variable form factor transmitter (102) approximated by the wire loop (204) shown in fig. 2D, the length of the wire segment s and the value of the capacitor C may be selected in the factory based on equation (12C) to maintain the resonant angular frequency ω of the wire loop (204)₀Equal to the angular frequency of the RF power source, which may be in the class a frequency range defined in international union "radio rules" article 5, footnote 5.138 (i.e., 6.765MHz-6.795 MHz).

In one or more embodiments of the invention, the manufacturing tolerances described above are controlled such that the resulting capacitance range, length range, and inductance range do not result in a resonant angular frequency ω₀Deviating from the class a frequency range (i.e., 6.765MHz-6.795 MHz). In addition, forIn both cases, there is an approximation error due to the physical difference between the user-adapted form factor of the variable form factor transmitter (102) and the simplified form factor of the parallel line transmission line (201) or wire loop (204). In one or more embodiments of the invention, the input impedance and the characteristic frequency of the variable form factor transmitter (102) may be adjusted in the factory and by the user in order to compensate for the manufacturing tolerances and approximation errors described above.

Fig. 2H shows a schematic diagram of an equivalent circuit a (205a) and an equivalent circuit B (205B) of the variable form factor transmitter (102). For optimal power transfer from the power supply (108), the input impedance of the variable form factor transmitter (102) and the output impedance of the power supply (108) (by resistor R)_LRepresentation) are matched. The resistor R is an effective series resistance representing all sources of loss (e.g., ohmic loss, radiative loss, dielectric loss, etc.) of the variable form factor transmitter (102). Variable capacitor C₁Determining an apparent input impedance of the variable form factor transmitter (102) at its resonant frequency, and a variable capacitor C₂The resonant frequency is set.

Equivalent circuit B (205B) corresponds to a simplified version of equivalent circuit A (205a), where C₂、 C₃And L have been combined into a single reactance χ. When C is present₁Having the value given by equation (15), the input impedance of the variable form factor transmitter (102) is equal to R_L。

For R_L<In the case of R, the transformer coupling scheme shown in fig. 2E may be used. For R_LIn the case of ≧ R, the capacitive coupling scheme shown in FIG. 2F can be used.

FIG. 4 shows a schematic diagram of an example RF power supply in accordance with one or more embodiments of the invention. In particular, the exemplary RF power supply shown in fig. 4 may operate as the power supply (108) depicted in fig. 1A, 1C, 2B, 2C, and 2D above based on the ISM band. Specifically, the exemplary RF power supply shown in fig. 4 includes a terminal a (204a) and a terminal B (204B) corresponding to the two terminals of the power supply (108) shown in fig. 1A, 1C, 2B, 2C, and 2D above. The schematic specifies the capacitance, inductance, and resistance values of various RLC circuit elements and the commercial part numbers of various integrated circuit elements. In one or more embodiments, one or more of the modules and elements shown in fig. 4 may be omitted, repeated, and/or replaced. Accordingly, embodiments of the present invention should not be considered limited to the particular arrangement of modules shown in FIG. 4.

Fig. 5A shows a schematic diagram of an example receiver device a (500a) in accordance with one or more embodiments of the invention. In one or more embodiments, one or more of the modules and elements shown in fig. 5A may be omitted, repeated, and/or replaced. Accordingly, embodiments of the present invention should not be considered limited to the particular arrangement of modules shown in FIG. 5A.

As shown in fig. 5A, receiver device a (500a) includes a plurality of Light Emitting Diodes (LEDs) (e.g., LEDs (502)) connected in parallel to form an LED string. Both ends of the LED string are connected to a rectifying circuit a (501a) to form a loop. For example, the loop may be a circular loop used as a mobile LED lighting device used within the wireless power transfer area (101) depicted in fig. 1A above. In one or more embodiments of the invention, the rectifier circuit A (501a) includes a capacitor C₁、C₂And C₃And a rectifier diode D₁And D₂. When the receiver device a (500a) is present with an oscillating magnetic field, the change in magnetic flux through the loop of the LED string causes a voltage difference between the two ends of the LED string. The induced voltage difference oscillates with time. Adjusting capacitance C₃So that the LED string resonates with the oscillating magnetic field to enhance the induced oscillating voltage. Rectifier diode D₁And D₂The induced oscillating voltage is rectified to create a DC voltage difference between the outer wire (503a) and the inner wire (503b) of the LED string, thereby powering the parallel connected LEDs (e.g., LED (502)). Capacitor C₁And C₂Acts as an RF bypass capacitor to keep the outer lead (503a) and the inner lead (503b) of the LED string appear shorted to the RF current. The receiver device A (500a) is configured by coupling with a rectifier diode D₁Or D₂Combined forward voltage drop limits on series connected LEDsLoop voltage, which improves safety for the user.

Similar to fig. 5A, fig. 5B shows an example receiver device B (500B), which is a larger version of receiver device a (500a) having multiple rectifier circuits (i.e., rectifier circuit B (501B), rectifier circuit C (501C), rectifier circuit D (501D), rectifier circuit E (50 le)). The operation of receiver device B (500B) is substantially the same as receiver device a (500 a). The number of segments in the receiver device B (500B) may be selected to provide optimal impedance matching to the load (i.e., parallel connected LEDs).

In addition to fig. 5A and 5B, fig. 5C shows a schematic diagram of other example receiver devices.

Fig. 5C shows a schematic diagram of an example receiver device circuit (500C) in accordance with one or more embodiments of the invention. In one or more embodiments, the receiver device circuitry (500c) is used for various types of receiver devices having different shapes, sizes, form factors, etc., for various different types of mobile or stationary applications within the wireless power transfer region (101) as shown in fig. 1A above. In one or more embodiments, at least the inductor L of the receiver device circuitry (500c) is placed within the wireless power transfer region (101) for receiving wireless power transfer. The remaining components shown in fig. 5C are configured to convert the received wireless power to be delivered by the load (via resistor R)_LRepresentation) of the consumption.

As shown in fig. 5C, the inductor L and the capacitor C₁、C₂And C₃Tuned together to resonate at the characteristic frequency of the variable form factor transmitter (102) and the RF power supply (108) described with reference to fig. 1A-2G above. Selection capacitor C₁To provide impedance matching between the resonant receiver and the input of the DC-DC converter (504). The DC-DC converter (504) converts the rectified voltage into a constant voltage to drive a load R_L. The DC-DC converter (504) allows the receiver device circuit (500c) to supply a load R_LA constant voltage is provided even if the receiver device circuitry (500c) moves through a region of varying magnetic field strength within the wireless power transfer region (101). Note that the load R_LNeed not necessarily beAre linear devices (i.e., devices having a linear voltage to current relationship). Load R_LExamples of (d) include, but are not limited to, LEDs, microcontrollers, motors, sensors, actuators, and the like.

In one or more embodiments of the invention, receiver device a (500a), receiver device B (500B), or receiver device circuitry (500c) may wirelessly receive power from any electromagnetic transmitter, such as a dipole transmitter (e.g., a magnetic dipole transmitter), a loop antenna with distributed capacitance, a parallel line transmission line with distributed capacitance, a shielded transmission line with distributed capacitance, etc. In one or more embodiments of the invention, a receiver device a (500a), a receiver device B (500B), and/or a receiver device circuit (500C) are placed within the wireless power transfer region (101) as a receiver device (a), a receiver device (B), a receiver device (C), a receiver device (D), a receiver device (E), or a receiver device (F) to wirelessly receive power from the variable form factor transmitter (102).

FIG. 6 shows a flow diagram in accordance with one or more embodiments of the invention. In one or more embodiments of the invention, the method of fig. 6 may be practiced using the example systems and example variable form factor transmitters described above with reference to fig. 1A, 1C, 2A, 2B, and/or 2D. In one or more embodiments of the invention, one or more of the elements shown in fig. 6 may be omitted, repeated, and/or performed in a different order than that shown in fig. 6. Accordingly, the particular arrangement of steps shown in FIG. 6 should not be construed as limiting the scope of the invention.

Initially, in element 601, a variable form factor transmitter is adapted to adapt a form factor based on a predetermined wireless power transfer region. In one or more embodiments, the variable form factor transmitter in the adapted form factor has a characteristic frequency.

In element 602, the eigenfrequency of the variable form factor transmitter remains substantially independent of the adaptation form factor while adapting to the variable form factor transmitter.

In one or more embodiments, the variable form factor transmitter includes a plurality of capacitors connected in series by line segments into a string of distributed capacitors.

In one or more embodiments, adapting the variable form factor transmitter includes adjusting a length of the string of distributed capacitors based on a size of the predetermined wireless power transfer area by cutting or splicing line segments. In particular, the characteristic frequency is substantially independent of the adjusted length of the string of distributed capacitors.

In one or more embodiments, adapting the variable form factor transmitter comprises: based on the shape of the predetermined wireless power transfer area, a string of distributed capacitors is arranged to occupy the multi-dimensional surface. In particular, the eigenfrequency is substantially independent of the form factor of the multi-dimensional surface.

In one or more embodiments, adapting the variable form factor transmitter includes folding a string of distributed capacitors into a pair of parallel lines based on the elongated shape of the predetermined wireless power transfer area. In particular, the eigenfrequency is substantially independent of the form factor of the pair of parallel lines.

In one or more embodiments, adapting the variable form factor transmitter includes disposing a string of distributed capacitors within a cylindrical conductive shield (e.g., along a centerline). One end of the string of distributed capacitors is connected to the cylindrical conductive shield as a return path to the power supply. In particular, the characteristic frequency is substantially independent of the length of the series-connected capacitors.

In one or more embodiments, a dimensional tolerance of the adaptation form factor is determined to ensure that the range of wireless power transfer covers the predetermined wireless power transfer area. In particular, the characteristic frequency is maintained within a predetermined range while the variable form factor transmitter is fitted within dimensional tolerances.

In element 603, from a Radio Frequency (RF) power source and based at least in part on a characteristic frequency, RF power is transmitted over a predetermined wireless power transfer area via a near-electromagnetic field of a variable form factor transmitter. In one or more embodiments, the drive wire loop is disposed proximate to the variable form factor transmitter. In particular, the drive wire loop is powered by an RF power source and, in turn, energizes the variable form factor transmitter.

In one or more embodiments, the RF power supply is connected to a matching capacitor, the value of which is selected to provide impedance matching between the RF power supply and the variable form factor transmitter. In one or more embodiments, the RF power supply is connected to the matching capacitor through a resonant balun. In one or more embodiments, the RF power supply is connected to a matching capacitor through an unbalanced coaxial transmission line, which shields a voltage node attached to the variable form factor transmitter.

In element 604, the receiver device is disposed within a predetermined wireless power transfer region. In one or more embodiments, a portion of the RF power transmitted by the RF power source via the variable form factor transmitter is received by the receiver device. In particular, the characteristic frequency is also substantially independent of the number or arrangement of receiver devices.

Claims

1. A wireless power receiver that wirelessly receives power from a variable form factor transmitter that generates an oscillating magnetic field, comprising:

a receive coil circuit comprising:

a diode string formed of an external wire, an internal wire, and a plurality of diodes, each of the plurality of diodes having a first end coupled to the external wire and a second end coupled to the internal wire such that each of the plurality of diodes is connected in parallel with each other, the diode string forming a circular loop; and

a rectifier circuit coupled to an end of the diode string, the rectifier circuit comprising:

a plurality of capacitors, wherein at least one capacitor is configured to resonate the diode string with the oscillating magnetic field and enhance an induced oscillating voltage; and

a plurality of rectifier diodes rectifying the induced oscillating voltage to generate a DC voltage difference between an external lead and an internal lead of the diode string to power the diodes connected in parallel.

2. The wireless power receiver of claim 1, wherein:

a first end of each diode coupled to the external lead is an anode; and

a second terminal of each diode coupled to the internal conductor is a cathode.

3. The wireless power receiver of claim 2, wherein the plurality of diodes are a plurality of Light Emitting Diodes (LEDs).

4. The wireless power receiver of claim 3, wherein the wireless power receiver is implemented in a Light Emitting Diode (LED) lighting device.

5. The wireless power receiver of claim 1, wherein:

the plurality of capacitors includes a first bypass capacitor C₁And a second bypass capacitor C₂Said first bypass capacitor C₁And a second bypass capacitor C₂Shorting the outer and inner leads of the diode string to Radio Frequency (RF) current; and

the at least one capacitor configured to resonate the diode string is a third capacitor C₃。

6. The wireless power receiver of claim 5, wherein the third capacitor C₃Is a variable capacitor.

7. The wireless power receiver of claim 6, wherein the first bypass capacitor C₁And said second bypass capacitor C₂In parallel with each of said diodes.

8. The wireless power receiver of claim 1, wherein the configuration of the receive coil circuit limits the voltage in the circular loop by a combined forward voltage drop across a diode in series with one of the rectifier diodes.

9. The wireless power receiver of claim 1, wherein the rectifying circuit is one of a plurality of rectifying circuits in the receive coil circuit.

10. An apparatus having a wireless power receiver implemented therein that wirelessly receives power from a transmit coil circuit that generates an oscillating magnetic field, comprising:

a receive coil circuit comprising:

a diode string formed of a first conductive element, a second conductive element, and a plurality of diodes, each of the plurality of diodes having a first end coupled to the first conductive element and a second end coupled to the second conductive element such that each of the plurality of diodes are connected in parallel with each other, the diode string forming a loop; and

a plurality of rectifier diodes rectifying the induced oscillating voltage to generate a DC voltage difference between the first and second conductive elements of the diode string to power the parallel connected diodes.

11. The apparatus of claim 10, wherein the first conductive element is an external wire and the second conductive element is an internal wire.

12. The apparatus of claim 10, wherein the loop is a circular loop.

13. The apparatus of claim 10, wherein the transmit coil circuit is implemented in a variable form factor transmitter.

14. The apparatus of claim 11, wherein:

the first terminal of each diode is an anode; and

the second terminal of each diode is a cathode.

15. The apparatus of claim 14, wherein the plurality of diodes are a plurality of Light Emitting Diodes (LEDs).

16. The device of claim 15, wherein the wireless power receiver is implemented in a Light Emitting Diode (LED) lighting device.

17. The apparatus of claim 11, wherein:

the at least one capacitor configured to resonate the diode string is a third capacitor C₃Wherein the third capacitor C₃Is a variable capacitor.

18. The apparatus of claim 17, wherein the first bypass capacitor C₁And said second bypass capacitor C₂In parallel with each of said diodes.

19. The apparatus of claim 10, wherein the configuration of the receive coil circuit limits the voltage in the loop by a combined forward voltage drop across a diode in series with one of the rectifier diodes.

20. The apparatus of claim 10, wherein the rectifying circuit is one of a plurality of rectifying circuits in the receive coil circuit.