WO2021235523A1

WO2021235523A1 - Power reception device, power transmission device, and wireless power transmission system

Info

Publication number: WO2021235523A1
Application number: PCT/JP2021/019210
Authority: WO
Inventors: 寿則佐藤; 浩司山本; 勉坂田
Original assignee: パナソニックＩｐマネジメント株式会社
Priority date: 2020-05-22
Filing date: 2021-05-20
Publication date: 2021-11-25

Abstract

This power reception device is used in a wireless power transmission system comprising a power transmission device and a power reception device. The power reception device comprises: a power reception antenna that receives AC power wirelessly from a power transmission antenna provided to the power transmission device; a power reception circuit that converts the AC power received by the power reception antenna to DC power and outputs the power; a load that operates using the DC power outputted from the power reception circuit, and is started up when the voltage of the DC power exceeds a prescribed startup voltage; a resistance circuit connected between the power reception circuit and the load, the resistance circuit including a resistor connected in parallel to the load; and a power reception control circuit that controls the impedance of the resistance circuit so as to suppress fluctuations in the load impedance of the power reception circuit due to the power reception device approaching the power transmission device and the load starting up.

Description

Power receiving equipment, power transmission equipment, and wireless power transmission system

This disclosure relates to a power receiving device, a power transmitting device, and a wireless power transmission system.

In recent years, the development of wireless power transmission technology for transmitting power wirelessly, that is, non-contactly, to mobile devices such as mobile phones and electric vehicles has been promoted. Wireless power transmission technology includes methods such as a magnetic field coupling method and an electric field coupling method. In a wireless power transmission system based on a magnetic field coupling method, power is wirelessly transmitted from the power transmission coil to the power reception coil with the power transmission coil and the power reception coil facing each other. Patent Documents 1 and 2 disclose an example of a wireless power transmission system by a magnetic field coupling method. On the other hand, in a wireless power transmission system based on an electric field coupling method, power is wirelessly transmitted from a pair of power transmission electrodes to a pair of power receiving electrodes with the pair of power transmission electrodes and the pair of power receiving electrodes facing each other. A wireless power transmission system based on an electric field coupling method can be used in an application of supplying power to a moving body having a load such as a battery from a plurality of power transmission electrodes provided on a floor surface, for example. Patent Document 3 discloses an example of a wireless power transmission system by an electric field coupling method.

International Publication No. 2015/0832223 Japanese Unexamined Patent Publication No. 2009-189231 Japanese Unexamined Patent Publication No. 2018-108012

The present disclosure provides a technique for suppressing heat generation or damage of a circuit element that may occur when a power receiving device starts receiving power from a power transmitting device.

The power receiving device according to one aspect of the present disclosure is a power receiving device used in a wireless power transmission system including a power transmitting device and a power receiving device, and is a power receiving antenna that wirelessly receives AC power from a power transmitting antenna included in the power transmitting device. A power receiving circuit that converts the AC power received by the power receiving antenna into DC power and outputs it, and a load that operates by the DC power output from the power receiving circuit, and the voltage of the DC power is a predetermined starting voltage. A load that starts when the voltage exceeds the above, a resistance circuit that is a resistance circuit connected between the power receiving circuit and the load, and includes a resistor connected in parallel to the load, and the power receiving device. It is provided with a power receiving control circuit that controls the impedance of the resistance circuit so as to suppress fluctuations in the load impedance of the power receiving circuit caused by approaching the power transmission device and activating the load.

The power transmission device according to another aspect of the present disclosure is a power transmission device used in a wireless power transmission system including a power transmission device and a power receiving device. The power receiving device operates by a power receiving antenna, a power receiving circuit that converts the AC power received by the power receiving antenna into DC power and outputs the power, and the DC power output from the power receiving circuit, and operates with the DC power voltage. It comprises a load that starts when a predetermined starting voltage is exceeded. The power transmission device includes a power transmission circuit that converts power supplied from a power source into AC power for power transmission and outputs the power transmission device, a power transmission antenna that wirelessly transmits the AC power to the power reception antenna, and the power reception device. A detector that detects the approach to the power transmission device and a power transmission control circuit that controls the power transmission circuit, and is output from the power transmission circuit when the approach of the power receiving device to the power transmission device is detected. It comprises a power transmission control circuit that controls the power transmission circuit so that the AC power is increased and the input voltage of the load is maintained within a preset range.

Comprehensive or specific embodiments of the present disclosure may be realized in devices, systems, methods, integrated circuits, computer programs, or recording media. Alternatively, it may be realized by any combination of devices, systems, methods, integrated circuits, computer programs and recording media.

According to the technique of the present disclosure, it is possible to suppress heat generation and damage of the circuit element that may occur when the power receiving device starts receiving power from the power transmitting device.

It is a figure which shows typically an example of the wireless power transmission system by the electric field coupling method. It is a figure which shows the schematic structure of the wireless power transmission system shown in FIG. 1. It is a figure which shows the example of the wireless power transmission system which each of a transmission electrode group and a power receiving electrode group includes four electrodes. It is a figure which shows the schematic structure of the wireless power transmission system shown in FIG. It is a figure which shows the example of the relationship between the ratio of the area of the part overlapping with a power transmission electrode, and the output voltage of a power receiving circuit among the power receiving electrodes. It is a figure which shows the structure which the resistor is connected in parallel between a power receiving circuit and a load. It is a figure which shows the structure which the switch is connected in addition to the resistor between a power receiving circuit and a load. It is a figure which shows the structure of the power transmission apparatus in an embodiment. It is a figure which shows the structure of the power receiving device in an embodiment. It is a figure which shows an example of the control method of a resistance circuit by a power receiving control circuit. It is a figure which shows another example of the control method of a resistance circuit by a power receiving control circuit. It is a figure which shows still another example of the control method of a resistance circuit by a power receiving control circuit. It is a figure which shows still another example of the control method of a resistance circuit by a power receiving control circuit. It is a sequence diagram which shows the example of the operation of a power transmission device and a power receiving device. It is a figure which shows the example of the time change of the input impedance of a load, the resistance value of a resistance circuit, and the load impedance of a power receiving circuit. It is a figure which shows the example of the time change of the transmission power output from a power transmission circuit, the output voltage of a power receiving circuit, and the load impedance of a power receiving circuit. It is a figure which shows the example of the configuration in which the detector is connected between a power source and a power transmission circuit. It is a figure which shows the example of the configuration in which the detector is connected between the power transmission circuit and a plurality of power transmission electrodes. It is a figure which shows the structure of the power transmission device by a modification. It is a figure which shows the configuration example which provided the voltage detector in the front stage of a load of a power receiving device. It is a figure which shows the example of the power receiving device which the load and the power receiving control circuit have a communication function. It is a figure which shows the example of the power transmission apparatus which a power transmission control circuit communicates with a load. It is a figure which shows the example which a load was provided with a charge control circuit and a power storage device. It is a figure which shows the example which includes the charge control circuit, the power storage device, and the load of a device such as a robot. It is a block diagram which shows the structural example of a wireless power transmission system schematically. It is a figure which shows the structural example of the inverter circuit schematically. It is a figure which shows the 1st example of a matching circuit. It is a figure which shows the 2nd example of a matching circuit. It is a figure which shows the 3rd example of a matching circuit. It is a figure which shows the 4th example of a matching circuit. It is a figure which shows the structural example of a rectifier circuit schematically. It is a figure which shows the structural example of the charge control circuit. An example is shown in which a power transmission electrode is laid on a side surface such as a wall. An example in which a power transmission electrode is laid on the ceiling is shown. It is a figure which shows the other example of the wireless power transmission system by the electric field coupling system schematically. It is a figure which shows typically the structure of the power receiving device and the power transmission device in another example of a wireless power transmission system. It is a figure which shows the other example of a power receiving device.

(Findings underlying this disclosure)
Before explaining the embodiments of the present disclosure, the findings underlying the present disclosure will be described.

FIG. 1 is a diagram schematically showing an example of a wireless power transmission system by an electric field coupling method. The "electric field coupling method" is a power receiving electrode group including a plurality of power transmitting electrodes and a power receiving electrode group including a plurality of power receiving electrodes by electric field coupling (also referred to as "capacitive coupling"). A transmission method in which power is transmitted wirelessly, that is, non-contactly to a group. For simplicity, an example in which each of the power transmission electrode group and the power reception electrode group is composed of a pair of two electrodes will be described first.

The wireless power transmission system shown in FIG. 1 is a system that wirelessly transmits power to a power receiving device 200 which is a mobile body. The power receiving device 200 in this example is an automated guided vehicle (AGV). The power receiving device 200 is used for transporting goods, for example, in a factory or a warehouse. In this system, a pair of flat plate-shaped

power transmission electrodes

120a and 120b are arranged on the floor surface 30. The pair of

power transmission electrodes

120a and 120b have a shape extending in the first direction (Y direction in FIG. 1). AC power is supplied to the pair of

power transmission electrodes

120a and 120b from a power transmission circuit (not shown).

The power receiving device 200 includes a pair of power receiving electrodes (not shown) facing the pair of

power transmission electrodes

120a and 120b. The power receiving device 200 receives the AC power transmitted from the

power transmitting electrodes

120a and 120b by the pair of power receiving electrodes. The received electric power is supplied to a load such as a motor, a secondary battery, or a capacitor for storing electricity included in the power receiving device 200. As a result, the power receiving device 200 is charged or driven.

FIG. 1 shows XYZ coordinates indicating X, Y, and Z directions orthogonal to each other. In the following description, the illustrated XYZ coordinates are used. The direction in which the

power transmission electrodes

120a and 120b extend is the Y direction, the direction perpendicular to the surfaces of the

power transmission electrodes

120a and 120b is the Z direction, and the direction perpendicular to the Y and Z directions is the X direction. The X direction is the direction in which the

power transmission electrodes

120a and 120b are lined up. The orientation of the structure shown in the drawings of the present application is set in consideration of easy-to-understand explanation, and does not limit the orientation when the embodiment of the present disclosure is actually implemented. Also, the shape and size of all or part of the structure shown in the drawings does not limit the actual shape and size.

FIG. 2 is a diagram showing a schematic configuration of the wireless power transmission system shown in FIG. 1. This wireless power transmission system includes a power transmission device 100 and a power receiving device 200. The power transmission device 100 includes a pair of

power transmission electrodes

120a and 120b, and a power transmission circuit 110 that supplies AC power to the

power transmission electrodes

120a and 120b. The power transmission circuit 110 is, for example, an AC output circuit including an inverter circuit. The power transmission circuit 110 converts the DC power supplied from a power source (not shown) into AC power for power transmission and outputs the DC power to the pair of

power transmission electrodes

120a and 120b. The power transmission circuit 110 may include a matching circuit for impedance matching between the

power transmission electrodes

120a and 120b and the inverter circuit. The power source is not limited to a DC power source and may be an AC power source. When the power source is an AC power source, a power conversion circuit that converts the input AC power into, for example, another AC power having a different frequency or voltage and outputs it may be used instead of the inverter circuit.

The power receiving device 200 includes a pair of

power receiving electrodes

220a and 220b, a power receiving circuit 210, and a load 300. The power receiving circuit 210 converts the AC power received by the

power receiving electrodes

220a and 220b into other forms of power required by the load 300 and supplies the AC power to the load 300. The power receiving circuit 210 outputs DC power of a predetermined voltage or AC power of a predetermined frequency and voltage required by the load 300. The power receiving circuit 210 may include various circuits such as a rectifier circuit and an impedance matching circuit. The load 300 may include devices that consume or store power, such as motors, capacitors for storage, or secondary batteries, and circuits that control those devices. Due to the electric field coupling between the pair of

power transmitting electrodes

120a and 120b and the pair of

power receiving electrodes

220a and 220b, electric power is transmitted wirelessly with the two facing each other.

Each of the

power transmission electrodes

120a and 120b and the

power reception electrodes

220a and 220b may be divided into two or more portions. For example, the configurations shown in FIGS. 3 and 4 may be adopted.

3 and 4 are diagrams showing an example of a wireless power transmission system in which each of the power transmission electrode group and the power reception electrode group includes four electrodes. In this example, the power transmission device 100 includes two first power transmission electrodes 120a and two second power transmission electrodes 120b. The two first power transmission electrodes 120a and the two second power transmission electrodes 120b are arranged alternately. Similarly, the power receiving device 200 includes two first power receiving electrodes 220a and two second power receiving electrodes 220b. The two first power receiving electrodes 220a and the two second power receiving electrodes 220b are also arranged alternately. At the time of power transmission, the two first power receiving electrodes 220a face each of the two first power transmission electrodes 120a, and the two second power receiving electrodes 220b face each of the two second power transmission electrodes 120b.

The power transmission circuit 110 has two terminals for outputting AC power. One terminal is connected to the two first power transmission electrodes 120a and the other terminal is connected to the two second power transmission electrodes 120b. During power transmission, the power transmission circuit 110 applies a first voltage to the two first power transmission electrodes 120a, and applies a second voltage having a phase opposite to the first voltage to the two second power transmission electrodes 120b. Apply. As a result, electric power is transmitted wirelessly by electric field coupling between the power transmission electrode group including the four power transmission electrodes and the power reception electrode group including the four power reception electrodes. According to such a configuration, it is possible to obtain the effect of suppressing the leakage electric field on the boundary between any two adjacent power transmission electrodes. As described above, in each of the power transmission device 100 and the power reception device 200, the number of electrodes that transmit or receive power is not limited to two.

In the following embodiments, as shown in FIGS. 1 and 2, a configuration in which the power transmission device 100 includes two power transmission electrodes and the power reception device 200 includes two power reception electrodes will be mainly described. In each of the following embodiments, each of the transmitting electrode group and the receiving electrode group may include more than two electrodes as illustrated in FIGS. 3 and 4. In either case, the electrodes to which the first voltage is applied at a certain moment and the electrodes to which the second voltage having the phase opposite to the first voltage is applied are arranged alternately. Here, the "opposite phase" is defined to include not only the case where the phase difference is 180 degrees but also the case where the phase difference is in the range of 90 degrees to 270 degrees. In the following description, the plurality of power transmission electrodes included in the power transmission device 100 may be referred to as “transmission electrode 120” without distinction, and the plurality of power receiving electrodes included in the power receiving device 200 may be referred to as “power receiving electrode 220” without distinction.

According to the wireless power transmission system as described above, the power receiving device 200, which is a mobile body, can receive electric power wirelessly while moving along the power transmission electrode 120. The power receiving device 200 can move along the power transmitting electrode 120 while maintaining a state in which the power transmitting electrode 120 and the power receiving electrode 220 are close to each other and face each other. As a result, the power receiving device 200 can move while charging a power storage device such as a battery or a capacitor. The power receiving device 200 may receive power wirelessly in a stationary state instead of receiving power while moving. Further, the power receiving device 200 is not limited to a moving body, and may be a device not provided with a power device for moving.

In such a wireless power transmission system, the power transmission device 100 detects that the power receiving device 200 has entered or is installed in the area where the power transmission electrode 120 is laid (hereinafter, referred to as “power transmission area”). May have functionality. The power transmission device 100 may be configured to output a relatively large amount of power for power transmission when it detects that the power receiving device 200 has entered or is installed in the power transmission area. If the power transmission device 100 outputs power for power transmission before the power receiving device 200 reaches the power transmission area or is installed, the resonance circuit in the power transmission circuit 110 is greatly deviated from the matched state. As a result, the circuit element in the power transmission circuit 110 may generate heat, be damaged, or be destroyed. Therefore, the power transmission circuit 110 may be configured to start power transmission after detecting a state in which the power receiving electrode 220 of the power receiving device 200 faces the power transmission electrode 120. Further, particularly when the power receiving device 200 is a mobile body, it is desirable to transmit power as long as possible while the power receiving electrode 220 overlaps the power transmission electrode 120. Therefore, the power transmission circuit 110 may be configured to start power transmission immediately after the power receiving device 200 reaches the power transmission area.

The approach of the power receiving device 200 to the power transmission device 100 can be detected based on the result of measuring the current, voltage, or power in the power transmission circuit 110, for example, in a state where the power transmission circuit 110 is outputting weak power. For example, the approach of the power receiving device 200 can be detected based on the change in the input current of the power transmission circuit 110. In the following description, a mode in which the power transmission circuit 110 outputs weak power in order to detect the approach of the power receiving device 200 is referred to as a “detection power transmission mode”. When the power transmission circuit 110 detects the approach of the power receiving device 200, the power transmission circuit 110 increases the output power to a relatively large power for power transmission. A mode in which the power transmission circuit 110 outputs a relatively large amount of power for power transmission is referred to as a "main power transmission mode". Instead of detecting the power receiving device 200 by the detection power transmission mode, the approach of the power receiving device 200 may be detected by a sensor such as a camera or a distance measuring device. When the power transmission circuit 110 detects the approach of the power receiving device 200, the power transmission circuit 110 shifts to the main power transmission mode.

Here, the load 300 includes, in addition to a power storage device such as a battery and a drive device such as an electric motor, various electronic circuits such as a DC-DC converter and a control circuit thereof that supply necessary power to those devices. Is done. These circuits start when the applied voltage exceeds a certain value. Hereinafter, this constant value is referred to as "starting voltage", and starting the electronic circuit included in the load 300 is expressed as "starting the load 300". The load 300 operates at a specific input impedance during constant operation, that is, during stable operation. The power transmission circuit 110 and the power reception circuit 210 are designed so that the efficiency is maximized while the load 300 is in stable operation. In this case, in the following description, the input impedance of the load 300 during stable operation, that is, the load impedance of the power receiving circuit 210 is expressed as "design value" for the power transmission circuit 110 and the power receiving circuit 210.

The input impedance of the load 300 is higher than the design value before the load 300 is started and until the operation is stable after the load 300 is started. In that state, the loss in the power transmission circuit 110 and the power reception circuit 210 increases, the output voltage of the power reception circuit 210 rises, and there is a risk of heat generation, damage or destruction of the circuit element.

FIG. 5 is a diagram showing an example of the relationship between the ratio of the area of the portion of the power receiving electrode 220 that overlaps the power transmission electrode 120 and the output voltage of the power receiving circuit 210 in an exemplary wireless power transmission system. In this example, the load impedance of the power receiving circuit 210 is substantially infinite in the state before the load 300 is started, and the input voltage of the power transmission circuit 110 in that state is 12V. The power transmission circuit 110 and the power reception circuit 210 are designed so that the input voltage of the power transmission circuit 110 and the output voltage of the power reception circuit 210 are equal to each other when the load impedance of the power reception circuit 210 is the design value. That is, if the load impedance of the power receiving circuit 210 is a design value, the vertical axis: the power receiving circuit output voltage (V) is 12V when the horizontal axis: electrode overlapping area ratio (%) in FIG. 5 is 100%. However, as shown in FIG. 5, when the load impedance of the power receiving circuit 210 is higher than the design value, the output voltage becomes larger than the input voltage of the power transmission circuit 110 as the overlap of the electrodes increases. To increase. The portion shown by the dotted line in FIG. 5 indicates that the output voltage of the power receiving circuit 210 rises so much that it may cause damage to the circuit element. Therefore, measures are required to mitigate the rise in output voltage.

FIG. 6A is a diagram showing a configuration in which a resistor 232 is connected in parallel between the power receiving circuit 210 and the load 300. By arranging the resistor 232 in this way, the impedance of the power receiving device 200 as seen from the power transmission device 100 can be reduced. Therefore, even if the load 300 is in a high impedance state, it is possible to suppress an increase in the voltage of the power transmission circuit 110 and the power reception circuit 210. This enables safe detection of the power receiving device 200 and activation of the load 300. However, in this configuration, when the power transmission device 100 shifts to the main power transmission mode, a large current flows through the resistor 232, so that there is a risk of heat generation and destruction.

FIG. 6B is a diagram showing a configuration in which a switch 234 is connected in addition to the resistor 232 between the power receiving circuit 210 and the load 300. In this example, the switch 234 is controlled to be on until the load 300 is activated and turned off after the load 300 is activated. As a result, after the load 300 is started, the current path to the resistor 232 is cut off. With such a configuration, it is possible to avoid a voltage increase before the load 300 is started, and it is possible to reduce the risk of heat generation after the power transmission device 100 shifts to the main power transmission mode after the start. However, the load impedance of the power receiving circuit 210 (that is, the input impedance of the circuit after the power receiving circuit 210) suddenly changes due to the operation of switching the switch 234. As a result, the output voltage of the power receiving circuit 210 fluctuates greatly, and in some cases, the rated voltage of the load 300 may be exceeded.

The above problems may occur not only in the electric field coupling type wireless power transmission system but also in the magnetic field coupling type wireless power transmission system. That is, even in a system in which power is transmitted not by electric field coupling between the power transmission electrode 120 and the power reception electrode 220 but by magnetic field coupling between the power transmission coil and the power reception coil, the above-mentioned problem may occur at the start of the main power transmission. ..

The present inventors have come up with the configuration of the embodiment of the present disclosure described below in order to solve the above-mentioned problems. Hereinafter, an outline of the embodiments of the present disclosure will be described.

The power receiving device according to the embodiment of the present disclosure is used in a wireless power transmission system including a power transmitting device and a power receiving device. The power receiving device includes a power receiving antenna that wirelessly receives AC power from a power transmitting antenna included in the power transmitting device, a power receiving circuit that converts the AC power received by the power receiving antenna into DC power and outputs the power, and outputs from the power receiving circuit. A load operated by the DC power, which is a load that starts when the voltage of the DC power exceeds a predetermined starting voltage, and a resistance circuit connected between the power receiving circuit and the load. Then, the resistance circuit including the resistor connected in parallel with the load and the power receiving device approach the power transmitting device so as to suppress the fluctuation of the load impedance of the power receiving circuit caused by the activation of the load. , A power receiving control circuit for controlling the impedance of the resistance circuit.

Here, the "power transmission antenna" is an element that sends electric power to space, such as the above-mentioned power transmission electrode and power transmission coil. The “power receiving antenna” is an element that receives power transmitted from the power transmission antenna, such as the above-mentioned power receiving electrode and power receiving coil. The "load impedance of the power receiving circuit" means the input impedance of the circuit after the power receiving circuit. "Load" includes any equipment and circuit operated by DC power output from the powered circuit. The load may include, for example, a DC-DC converter that converts DC power output from a power receiving circuit into other DC power having a different voltage, and a control circuit thereof. In such a configuration, when the voltage applied to the control circuit exceeds a predetermined starting voltage, the control circuit starts driving the DC-DC converter.

According to the above configuration, the power receiving control circuit is the impedance of the resistance circuit so as to suppress the fluctuation of the load impedance of the power receiving circuit caused by the power receiving device approaching the power transmission device and activating the load. To control. Therefore, it is possible to suppress the increase in voltage due to the fluctuation of the load impedance and reduce the risk of heat generation, damage, and destruction of the circuit element.

The power receiving control circuit may be configured to control the impedance of the resistance circuit so as to maintain the load impedance within a preset range. By such control, the load impedance is maintained within a certain range, so that the operation before and after the start of the load can be further stabilized.

The resistance circuit may include a resistor connected in parallel with the load and a switch connected in parallel with the load and in series with the resistor. The power receiving control circuit may control the impedance of the resistance circuit by controlling the switch.

The power receiving control circuit turns on the switch before the load is activated, controls the switch so that the impedance of the resistance circuit increases after the load is activated, and transmits power from the power transmission device. The switch may be turned off after the power is supplied.

The power receiving control circuit may turn on the switch after the power transmission from the power transmission device to the power receiving device is completed.

The resistance value of the resistor may be substantially equal to the resistance value of the load when power for power transmission is supplied from the power transmission device.

The resistance circuit may include a variable resistor connected in parallel with the load. The power receiving control circuit may control the impedance of the resistance circuit by controlling the resistance value of the variable resistor.

The load may include a DC-DC converter. The activation of the load may be the activation of the DC-DC converter.

The power transmission device according to another embodiment of the present disclosure is used in a wireless power transmission system including a power transmission device and a power receiving device. The power receiving device operates by a power receiving antenna, a power receiving circuit that converts the AC power received by the power receiving antenna into DC power and outputs the power, and the DC power output from the power receiving circuit, and operates with the DC power voltage. It comprises a load that starts when a predetermined starting voltage is exceeded. The power transmission device includes a power transmission circuit that converts power supplied from a power source into AC power for power transmission and outputs the power transmission device, a power transmission antenna that wirelessly transmits the AC power to the power reception antenna, and the power reception device. A detector that detects the approach to the power transmission device and a power transmission control circuit that controls the power transmission circuit, and is output from the power transmission circuit when the approach of the power receiving device to the power transmission device is detected. It includes a power transmission control circuit that controls the output voltage of the power transmission circuit so that the AC power is increased and the input voltage of the load is maintained within a preset range.

According to the above configuration, when the power transmission control circuit detects the approach of the power receiving device to the power transmission device, the power transmission control circuit increases the AC power output from the power transmission circuit, and the input voltage of the load is set in advance. The power transmission circuit is controlled so as to be maintained within a set range. The lower limit of the range may be, for example, the starting voltage. The upper limit of the range may be, for example, the rated voltage of the load. By the above control, the input voltage of the load is maintained within the preset range. Therefore, for example, it is possible to prevent the input voltage of the load from falling below the starting voltage of the load or exceeding the rated voltage of the load.

The wireless power transmission system according to another embodiment of the present disclosure includes any of the above-mentioned power transmission devices and any of the above-mentioned power receiving devices.

The power receiving device can be, for example, a mobile body. As used in the present disclosure, the term "moving body" is not limited to a vehicle such as the automatic guided vehicle (AGV) described above, but means any movable object driven by electric power. Mobiles include, for example, electric motors and electric vehicles with one or more wheels. Such vehicles may be, for example, the aforementioned AGVs, transfer robots, electric vehicles (EVs), electric carts, electric wheelchairs. The "moving body" in the present disclosure also includes a movable object having no wheels. For example, unmanned aerial vehicles (UAVs, so-called drones) such as biped robots and multicopters, and manned electric aircraft, and elevators are also included in the "mobile body". The power receiving device is not limited to such a mobile body, but may be any portable device such as a charging pole, a smartphone, a tablet computer, or a laptop computer.

Hereinafter, a more specific embodiment of the present disclosure will be described. However, more detailed explanation than necessary may be omitted. For example, detailed explanations of already well-known matters and duplicate explanations for substantially the same configuration may be omitted. This is to avoid unnecessary redundancy of the following description and to facilitate the understanding of those skilled in the art. It should be noted that the inventor intends to limit the subject matter described in the claims by those skilled in the art by providing the accompanying drawings and the following description in order to fully understand the present disclosure. No. In the following description, components having the same or similar functions are designated by the same reference numerals.

(Embodiment)
A wireless power transmission system according to an exemplary embodiment of the present disclosure will be described. The wireless power transmission system of the present embodiment includes a power transmission device 100 and a power receiving device 200 that receives power wirelessly from the power transmission device 100, similar to the system described with reference to FIGS. 1 to 4. The power receiving device 200 can be a moving body such as an automatic guided vehicle. In the present embodiment, an example in which the power receiving device 200 is a mobile body will be mainly described, but the configuration and operation of the present embodiment are similarly applied to the case where the power receiving device 200 is a device other than the mobile body. Can be done.

FIG. 7 is a diagram showing the configuration of the power transmission device 100 in the present embodiment. The power transmission device 100 includes a power transmission circuit 110, a plurality of power transmission electrodes 120, a power transmission control circuit 150, and a detector 140. FIG. 7 also shows a power supply 400 that outputs DC power. The power source 400 may be a component of the power transmission device 100 or an external element of the power transmission device 100. The power transmission circuit 110 converts the DC power output from the power source 400 into AC power and outputs it. The power transmission electrode 120 transmits the AC power output from the power transmission circuit 110 to the space. The detector 140 is a circuit or a sensor that detects that the power receiving device 200 has approached the power transmission area in which the power transmission electrode 120 is laid. The power transmission control circuit 150 controls the power transmission circuit 110 to output desired AC power from the power transmission circuit 110. When the detector 140 detects the approach of the power receiving device 200, the power transmission control circuit 150 sends an instruction to increase the output voltage to the power transmission circuit 110. In response to this instruction, the power transmission circuit 110 increases the AC power supplied to the power transmission electrode 120.

When the power receiving device 200 approaches the power transmission device 100, for example, the detector 140 measures the current, voltage, or power in the power transmission circuit 110 while the power transmission control circuit 150 outputs a weak power to the power transmission circuit 110. Can be detected based on the results of the above. As described above, the mode in which the power transmission circuit 110 outputs weak power for the detection of the power receiving device 200 is referred to as a “detection power transmission mode”. On the other hand, a mode in which the power transmission circuit 110 outputs a relatively large amount of power for power transmission is referred to as a "main power transmission mode". Instead of detecting the power receiving device 200 by the detection power transmission mode, the approach of the power receiving device 200 may be detected by a sensor such as a camera or a distance measuring device. In that case, the power transmission control circuit 150 does not need to output the above-mentioned weak electric power to the power transmission circuit 110. Here, "detecting the approach of the power receiving device 200 to the power transmission device 100" means that the plurality of power receiving electrodes 220 in the power receiving device 200 are at least partially opposed to or coupled to the plurality of power transmission electrodes 120 in the power transmission device 100. It means to detect the state to do.

FIG. 8 is a diagram showing the configuration of the power receiving device 200 in the present embodiment. The power receiving device 200 includes a plurality of power receiving electrodes 220, a power receiving circuit 210, a resistance circuit 230, a power receiving control circuit 250, and a load 300. The resistance circuit 230 is connected between the power receiving circuit 210 and the load 300. The resistor circuit 230 includes a resistor 232 and a switch 234 connected in series with each other. The resistor 232 and the switch 234 are connected in parallel to the load 300. Although one resistor 232 is shown in FIG. 8, the resistor 232 may be a set of a plurality of resistors.

The plurality of power receiving electrodes 220 wirelessly receive AC power from the plurality of power transmission electrodes 120 included in the power transmission device 100. The power receiving circuit 210 converts the AC power received by the power receiving electrode 220 into DC power and outputs it. The load 300 operates by the DC power output from the power receiving circuit 210. The load 300 includes a power storage device such as a battery, a drive device such as an electric motor, and a circuit such as a DC-DC converter that supplies necessary power to those devices. The DC-DC converter is activated when the voltage of the DC power output from the power receiving circuit 210 exceeds a predetermined starting voltage. In the present embodiment, starting the DC-DC converter is expressed as "starting the load 300".

When the power receiving device 200 is separated from the power transmitting device 100, the impedance of the power receiving device 200 as seen from the power transmitting device 100 is substantially infinite. In this state, the power transmission device 100 operates in the detection power transmission mode that outputs power far smaller than the power output in the main power transmission mode, or operates in the mode in which power transmission is stopped and the power receiving device 200 is detected by the sensor. do. These modes for detecting the power receiving device 200 are referred to as "detection modes". When the power receiving device 200 approaches the power transmission device 100 to charge the power storage device, the power transmission device 100 detects the approach and increases the output power of the power transmission circuit 110. As a result, the electric power supplied to the load 300 gradually increases. When the input voltage of the load 300 exceeds the starting voltage, the load 300 starts starting. During the activation of the load 300, the impedance of the load 300 fluctuates and decreases. When the start of the load 300 is completed, the impedance of the load 300 becomes a specific value. As described above, the load impedance of the power receiving circuit 210 decreases with the activation of the load 300. The power receiving control circuit 250 controls the impedance of the resistance circuit 230 so as to suppress the fluctuation of the load impedance of the power receiving circuit 210 caused by the activation of the load 300. The power receiving control circuit 250 controls the impedance of the resistance circuit 230 so that the load impedance of the power receiving circuit 210 is maintained within a preset range regardless of the state of the load 300. By such control, the voltage in the power receiving device 200 can be maintained in an appropriate range, and the risk of heat generation, damage, or destruction of the circuit element can be reduced. The impedance of the resistance circuit 230 can be controlled, for example, by controlling the switch 234.

The power receiving control circuit 250 in the present embodiment turns on the switch 234 before the load 300 is activated, and after the load 300 is activated, controls the switch 234 so that the impedance of the resistance circuit 230 increases to transmit power. After the power for transmission is supplied from the device 100, the switch 234 is turned off. The power receiving control circuit 250 turns on the switch 234 again after the power transmission from the power transmitting device 100 to the power receiving device 200 is completed. The resistance value of the resistor 232 may be set to a value substantially equal to the resistance value of the load 300 when the power for transmission is supplied from the power transmission device 100 to the power receiving device 200. By such an operation, the load impedance of the power receiving circuit 210 can be maintained within an appropriate range.

Next, some examples of the control method of the resistance circuit 230 will be described with reference to FIGS. 9 to 12.

FIG. 9 is a diagram showing an example of a control method of the resistance circuit 230 by the power receiving control circuit 250. In this example, the switch 234 is a semiconductor switch such as a MOSFET, and the resistor 232 has a fixed resistance value. The power receiving control circuit 250 controls the resistance value, that is, the impedance of the resistance circuit 230 by adjusting the voltage input to the gate of the semiconductor switch.

FIG. 10 is a diagram showing another example of the control method of the resistance circuit 230 by the power receiving control circuit 250. In this example, the power receiving control circuit 250 controls the impedance of the resistance circuit 230 by adjusting the on / off duty ratio of the switch 234, that is, the ratio of the on time to the period.

FIG. 11 is a diagram showing still another example of the control method of the resistance circuit 230 by the power receiving control circuit 250. In this example, the resistor circuit 230 includes a variable resistor 233 connected in parallel with the load 300. The power receiving control circuit 250 controls the impedance of the resistance circuit 230 by controlling the resistance value of the variable resistor 233. In this example as well, the power receiving control circuit 250 may turn on the switch 234 before starting the load 300 and turn off the switch 234 after the start of the main power transmission. Alternatively, the switch 234 may be omitted, and the same function may be realized only by adjusting the resistance value of the variable resistor 233.

FIG. 12 is a diagram showing still another example of the control method of the resistance circuit 230 by the power receiving control circuit 250. In this example, the resistor circuit 230 includes a resistor 232 and a switch 234, each of which comprises a plurality of modules connected in parallel to the load 300. The power receiving control circuit 250 adjusts the combined resistance, that is, the combined impedance of all the modules by controlling the switch 234 in each module in the same manner as in the example of FIG. 9 or FIG. This controls the combined impedance of the entire resistance circuit 230. As in the example of FIG. 11, a variable resistor 233 may be provided instead of the resistor 232, and the combined impedance of the resistance circuit 230 may be controlled by adjusting the resistance value of each variable resistor 233. In that case, the switch 234 may be omitted.

Next, the operation of the power transmission device 100 will be described in more detail with reference to FIG. 7 again.

The power transmission control circuit 150 in the present embodiment adjusts the output voltage of the power transmission circuit 110 so that the voltage input to the load 300 is maintained within a preset appropriate operating voltage range. Here, the lower limit of the operating voltage range may be set to a value substantially equal to, for example, the starting voltage of the load 300. The upper limit of the operating voltage range may be set to a value substantially equal to, for example, the rated voltage of the load 300. By such control, the voltage input to the load 300 can be maintained in an appropriate range, and stable operation can be realized.

FIG. 13 is a sequence diagram showing an example of the operation of the power transmission device 100 and the power receiving device 200 in the present embodiment. In this example, the power transmission device 100 operates in the detection power transmission mode as the detection mode, and after detecting the power receiving device 200, shifts to the main power transmission mode.

Before the power receiving device 200 enters or is installed in the power transmission area, the power transmission control circuit 150 sets the output voltage of the power transmission circuit 110 to the initial value and starts the power transmission mode for detection (step S100). On the other hand, the power receiving control circuit 250 sets the resistance value of the resistance circuit 230 to the initial value. This initial value may be set to, for example, a value equal to the input impedance of the load 300 in the main transmission mode. At this time, the switch 234 is kept on.

The power receiving device 200 enters or is installed in the power transmission area for charging (step S201). Then, the detector 140 of the power transmission device 100 detects the entry or installation of the power receiving device 200 into the power transmission area based on the change of the current, the voltage, or the power in the power transmission device 100 (step S101). After the detection, the power transmission control circuit 150 starts controlling the output voltage of the power transmission circuit 110 (step S102). After that, the power transmission control circuit 150 adjusts the output voltage of the power transmission circuit 110 so that the voltage input to the load 300 is maintained within a preset range. In the present embodiment, how the input voltage of the load 300 changes from the time when the power receiving device 200 reaches the power transmission area to the time when the power transmission device 200 passes through the power transmission area when the power transmission control by the power transmission control circuit 150 is not performed. Is known in advance. Based on that information, data defining the relationship between the elapsed time since the power receiving device 200 reaches the power transmission area and the voltage to be output by the power transmission circuit 110 is prepared in advance, and is stored in the storage medium of the power transmission control circuit 150. It has been recorded. Based on the data, the power transmission control circuit 150 adjusts the output voltage of the power transmission circuit 110 until the main power transmission is started.

When the voltage input to the load 300 exceeds the preset start voltage, the start of the load 300 starts (step S202). After the start of the load 300 is started, the power receiving control circuit 250 starts controlling the impedance of the resistance circuit 230 (step S203). The power receiving control circuit 250 grasps the activation of the load 300 based on, for example, a signal sent from the load 300. The load 300 may include, for example, a voltage detector in front of the DC-DC converter. In such a configuration, when the voltage detected by the voltage detector exceeds the threshold value, the power receiving control circuit 250 can determine that the load 300 has been activated. Impedance control is started immediately after the start of the load 300 or after a certain period of time has elapsed. In the present embodiment, it is known in advance how the impedance of the load 300 changes from the start to the completion of the start of the load 300 when the impedance is not controlled. Based on that information, data that defines the relationship between the elapsed time from the start of the load 300 and the resistance value of the resistance circuit 230 to be set is prepared in advance and recorded in the storage medium of the power receiving control circuit 250. Has been done. The power receiving control circuit 250 adjusts the resistance value of the resistance circuit 230 based on the data. When the activation process of the load 300 is completed in step S204, the power receiving control circuit 250 turns off the switch 234 and ends the impedance control of the resistance circuit 230 (step S205). By turning off the switch 234 before the start of the main power transmission, heat generation and damage of the resistor 232 can be suppressed.

After that, the power transmission control circuit 150 completes the transition to the main power transmission mode, and causes the power transmission control circuit 150 to output electric power for power transmission (step S103). As a result, the power receiving device 200 starts charging (step S206). The power receiving device 200 ends charging when the storage amount of the power storage device reaches the upper limit or when the power receiving device 200 passes through the power transmission area (step S207). After the charging is completed, the power receiving control circuit 250 turns on the switch 234 (step S208).

By the above operation, the load impedance at the start of charging and the input voltage of the load 300 can be maintained in an appropriate range, heat generation and damage of the circuit element can be suppressed, and the operation can be stabilized.

FIG. 14 is a diagram showing an example of time change of the input impedance of the load 300, the resistance value of the resistance circuit 230, and the load impedance of the power receiving circuit 210. In this example, after the detector 140 detects that the entire surface of the power receiving electrode 220 overlaps the power transmission electrode 120, the transition from the detection mode to the main power transmission mode is started. However, the above-mentioned mode transition condition is only an example, and other conditions may be adopted. For example, the transition from the detection mode to the main power transmission mode may be started after the detector 140 detects that a part of the power receiving electrode 220 overlaps the power transmission electrode 120. The dotted line in FIG. 14 shows an example of a waveform in a comparative example in which impedance control is not performed, and the solid line shows an example of a waveform in this embodiment in which impedance control is performed. In the comparative example, the configuration shown in FIG. 6B is adopted, and the switch 234 is switched from on to off after the start of the load 300 is started. In the present embodiment, the power receiving control circuit 250 monotonically increases the resistance value of the resistance circuit 230 from the start of the load 300 to the completion of the start. By this control, the change in the load impedance of the power receiving circuit 210, that is, the combined impedance of the resistance circuit 230 and the load 300 is suppressed as compared with the comparative example, and is maintained within a preferable range.

FIG. 15 is a diagram showing an example of time-dependent changes in the power transmitted from the power transmission circuit 110, the output voltage of the power receiving circuit 210, and the load impedance of the power receiving circuit. In this example as well, the transition from the detection mode to the main power transmission mode is started after the detector 140 detects that the entire surface of the power receiving electrode 220 overlaps the power transmission electrode 120. As described above, the above-mentioned mode transition condition is only an example, and other conditions may be adopted. The dotted line in FIG. 15 shows an example of a waveform in a comparative example in which the transmitted power is linearly increased, and the solid line shows an example of a waveform in the present embodiment in which the transmitted power is adjusted. In FIG. 15, the origin of the time axis is the time when the power receiving device 200 reaches the power transmission area. In this example, in order to explain the effect of controlling the transmitted power, the impedance control shown in FIG. 14 is not performed, and only the switch 234 during activation of the load 300 is switched. In the comparative example, the output voltage of the power receiving circuit 210 drops immediately after the start of the load 300, and rises sharply when the switch 234 is switched off. In this case, after the start of the load 300 is started, the load 300 may stop again below the start voltage, or a high voltage exceeding the rated voltage of the load 300 may be applied to the load 300. On the other hand, in the present embodiment, the power transmission control circuit 150 adjusts the power transmission power so that the output voltage of the power receiving circuit 210 is maintained within a predetermined range from the start of the load to the completion of the start of the load. As a result, the voltage input to the load 300 is maintained within the range from the starting voltage to the rated voltage, and stable operation can be realized. By using the control of the transmitted power shown in FIG. 15 and the impedance control shown in FIG. 14 in combination, the operation at the start of charging can be further stabilized.

Next, an example of a method of detecting the approach of the power receiving device 200 by the power transmitting device 100 will be described.

FIG. 16 is a diagram showing an example of a configuration in which a detector 140 is connected between a power supply 400 and a power transmission circuit 110. In this example, the detector 140 detects the current, voltage, or power input to the power transmission circuit 110. Before the power receiving device 200 reaches the power transmission area, the power transmission control circuit 150 causes the power transmission circuit 110 to output a weak electric power. The detector 140 measures, for example, the current input to the power transmission circuit 110. The detector 140 can determine that the power receiving device 200 has entered or is installed in the power transmission area when the current becomes equal to or higher than a preset threshold value. Alternatively, the detector 140 is installed or entered into the power transmission area when the amount of change from the measured value of the current when the power receiving device 200 is not present in the power transmission area becomes equal to or more than the threshold value. You may judge that it was.

FIG. 17 is a diagram showing an example of a configuration in which a detector 140 is connected between a power transmission circuit 110 and a plurality of power transmission electrodes 120. As in this example, the detector 140 may be arranged on the output side of the power transmission circuit 110. The detector 140 can detect the entry or installation of the power receiving device 200 into the power transmission area, for example, based on the change in the output current of the power transmission circuit 110. Alternatively, the detector 140 may detect the approach of the power receiving device 200 based on the phase difference between the output voltage and the output current of the power transmission circuit 110. For example, when the output current is in a delayed phase with respect to the output voltage, it can be determined that the power receiving device 200 has entered or is installed in the power transmission area.

The detector 140 may include a sensor located away from the power transmission circuit 110 and the power transmission electrode 120. The sensor can be, for example, a camera or a ranging device. Based on the position of the power receiving device 200 detected by the sensor, it can be determined that the power receiving device 200 has entered or is installed in the power transmission area.

The power transmission device 100 may have a configuration of any combination of the above-mentioned plurality of types of detection functions. It may be determined that the power receiving device 200 has entered or is installed in the power transmission area by satisfying the entry determination condition of one type or two or more types of detection functions among the plurality of types of detection functions.

Next, a modified example of this embodiment will be described.

FIG. 18 is a diagram showing a configuration of a power transmission device 100 according to a modified example. In this example, different power paths are provided between the detection power transmission mode and the main power transmission mode. In the detection transmission mode, the first power path is used, and in the main transmission mode, the second power path is used. A switch 170 is provided on the first path and the second path. The power transmission control circuit 150 controls the switch 170 to switch the power path to be used when shifting from the detection power transmission mode to the main power transmission mode. In the example of FIG. 18, the detector 140 is located only on the first power path. With such a configuration, it is possible to detect a circuit response such as current or voltage with high resolution as compared with the case where a common power path is used between the detection transmission mode and the main transmission mode.

FIG. 19 is a diagram showing a configuration example in which the power receiving device 200 is provided with a voltage detector 290 in front of the load 300. In this example, after the voltage detected by the voltage detector 290 reaches a threshold value (for example, the starting voltage of the load 300), the power receiving control circuit 250 starts impedance control of the resistance circuit 230.

FIG. 20 is a diagram showing an example of a power receiving device 200 in which the load 300 and the power receiving control circuit 250 have a communication function. FIG. 21 is a diagram showing an example of a power transmission device 100 in which the power transmission control circuit 150 communicates with the load 300. In this example, the load 300 includes a transmitter, and the power receiving control circuit 250 and the power transmission control circuit 150 include a receiver. The power receiving control circuit 250 and the power transmission control circuit 150 receive, for example, a signal indicating the input voltage of the load 300, a signal indicating the start or completion of the start of the load 300, or a signal indicating the start or completion of charging from the load 300. Can be done. As a result, the power receiving control circuit 250 and the power transmission control circuit 150 can always maintain the impedance of the resistance circuit 230 and the output voltage of the power transmission circuit 110 within an appropriate range according to the state of the load 300. After the main power transmission is started, a signal such as an input voltage of the load 300 may be transmitted to the power transmission control circuit 150. As a result, the power transmission control circuit 150 can control the power transmission circuit 110 so that appropriate power is supplied to the load 300.

FIG. 22 is a diagram showing an example in which the load 300 includes a charge control circuit 310 and a power storage device 330. The power storage device 330 is any rechargeable device, such as a secondary battery or a capacitor for storage. The charge control circuit 310 is a circuit that controls charging and discharging of the power storage device. In this example, the activation of the charge control circuit 310 corresponds to the above-mentioned "activation of the load 300". The power receiving control circuit 250 can grasp the activation state of the load 300 based on the signal output from the charge control circuit 310.

FIG. 23 is a diagram showing an example in which the load 300 includes a charge control circuit 310, a power storage device 330, and a load 340 (for example, a motor) of a device such as a robot. The load 340 of the device is connected in parallel with the power storage device 330. The charge control circuit 310 adjusts the power supply balance between the power storage device 330 and the load 340 of the device according to the received power. When the power receiving device 200 is not performing the power receiving operation, power can be supplied from the power storage device 330 to the load 340 of the device.

Next, an example of a wireless power transmission system including the above-mentioned power transmission device 100 and power receiving device 200 will be described.

FIG. 24 is a block diagram schematically showing the configuration of the wireless power transmission system of the present embodiment. This wireless power transmission system includes a power transmission device 100 and a power receiving device 200. FIG. 24 also shows a DC power supply 400, which is an external element of the wireless power transmission system. The power receiving device 200 in this embodiment is a mobile body as shown in FIG. Therefore, in the following description, the power receiving device 200 is also referred to as a “mobile body 200”.

The power transmission device 100 includes a power transmission circuit 110, a plurality of power transmission electrodes 120, a power transmission control circuit 150, and a detector 140. The power transmission circuit 110 includes an inverter circuit 160 and a matching circuit 180.

The inverter circuit 160 converts the DC power output from the power supply 400 into AC power and outputs it in response to a command from the power transmission control circuit 150. FIG. 25 is a diagram schematically showing a configuration example of the inverter circuit 160. In this example, the inverter circuit 160 is a full bridge type inverter circuit including four switching elements. Each switching element can be realized by a transistor such as an IGBT, MOSFET, or GaN. Each switching element is controlled by the power transmission control circuit 150. The power transmission control circuit 150 includes a gate driver that outputs a control signal that controls the on (conducting) and off (non-conducting) states of each switching element, and a processor such as a microcontroller (MCU) that causes the gate driver to output a control signal. And can be prepared. The power transmission control circuit 150 outputs AC power having a desired frequency and voltage from the inverter circuit 160 by controlling the on and off states of each switching element. Instead of the full-bridge type inverter circuit shown in the figure, a half-bridge type inverter circuit or another type of oscillation circuit such as class E may be used.

The frequency of power transmission can be set, for example, 50 Hz to 300 GHz, 20 kHz to 10 GHz in one example, 20 kHz to 20 MHz in another example, and 80 kHz to 14 MHz in another example. However, it is not limited to these frequency ranges.

The matching circuit 180 matches the impedance between the inverter circuit 160 and the power transmission electrode 120. 26A to 26D are diagrams showing a configuration example of the matching circuit 180.

FIG. 26A is a diagram showing a first example of the matching circuit 180. The matching circuit 180 in this example includes a first inductor Lt1, a second inductor Lt2, and a capacitor Ct1. The first inductor Lt1 is connected as a series circuit element between the power transmission electrode 120a and the first terminal 60a of the inverter circuit 160. The second inductor Lt2 is connected as a series circuit element between the power transmission electrode 120b and the second terminal 60b of the inverter circuit 160. The capacitor Ct1 is connected as a parallel circuit element between the wiring between the power transmission electrode 120a and the inductor Lt1 and the wiring between the power transmission electrode 120b and the inductor Lt2.

The first inductor Lt1 and the second inductor Lt2 are magnetically coupled. The coupling coefficient k of these inductors can be set to a value satisfying, for example, -1 <k <0. The first inductor Lt1 and the second inductor Lt2 can function as a common mode choke filter. In that case, it is possible to reduce the frequency used for power transmission and the common mode noise in the low-order harmonic band. In such a configuration, the resonator composed of the first inductor Lt1, the second inductor Lt2, and the first capacitor Ct1 may be referred to as a "common mode choke resonator".

FIG. 26B is a diagram showing a second example of the matching circuit 180. In addition to the configuration shown in FIG. 26A, the matching circuit 180 further includes a second capacitor Ct2, a third capacitor Ct3, and a third inductor Lt3. The second capacitor Ct2 is connected as a series circuit element between the first inductor Lt1 and the first terminal 60a. The third capacitor Ct3 is connected as a series circuit element between the second inductor Lt2 and the second terminal 60b. The third inductor Lt3 is connected as a parallel circuit element between the wiring between the first inductor Lt1 and the second capacitor Ct2 and the wiring between the second inductor Lt2 and the third capacitor Ct3. Will be done. It can be said that this configuration is a configuration in which a high-pass filter having a symmetrical circuit configuration is added in front of the configuration of the matching circuit 180 shown in FIG. 26A. According to such a configuration, the transmission efficiency can be further improved.

FIG. 26C is a diagram showing a third example of the matching circuit 180. The matching circuit 180 further includes a second capacitor Ct2 and a third inductor Lt3 in addition to the configuration shown in FIG. 26A. The second capacitor Ct2 is connected as a series circuit element between the first inductor Lt1 and the first terminal 60a. The third inductor Lt3 is connected as a parallel circuit element between the wiring between the first inductor Lt1 and the second capacitor Ct2 and the wiring between the second inductor Lt2 and the second terminal 60b. Will be done. It can be said that this configuration is a configuration in which a high-pass filter having an asymmetric circuit configuration is added in front of the configuration of the matching circuit 180 shown in FIG. 26A. Compared with the configuration of FIG. 26B, the positive / negative symmetry of the circuit is lowered, but the number of elements can be reduced. The transmission efficiency can be further improved by such a configuration.

FIG. 26D is a diagram showing a fourth example of the matching circuit 180. The matching circuit 180 further includes a third inductor Lt3 and a second capacitor Ct2 in addition to the configuration shown in FIG. 26A. The third inductor Lt3 is connected as a series circuit element between the first inductor Lt1 and the first terminal 60a. The second capacitor Ct2 is connected as a parallel circuit element between the wiring between the first inductor Lt1 and the third inductor Lt3 and the wiring between the second inductor Lt2 and the second terminal 60b. Will be done. It can be said that this configuration is a configuration in which a low-pass filter having an asymmetric circuit configuration is added in front of the configuration of the matching circuit 180 shown in FIG. 26A. The transmission efficiency can be further improved by such a configuration.

The matching circuit 180 in each of the above examples may include other circuit elements, for example, a network that functions as a filter, in addition to the circuit elements shown in the figure. Further, in each figure, the element represented as one inductor or one capacitor may be an aggregate of a plurality of inductors or a plurality of capacitors.

The detector 140 detects the input current of the inverter circuit 160. The power transmission control circuit 150 can detect the approach of the mobile body 200 based on the change in the current detected by the detector 140, and can shift from the above-mentioned detection power transmission mode to the main power transmission mode.

The mobile body 200 includes a plurality of power receiving electrodes 220, a power receiving circuit 210, a power receiving control circuit 250, a charging control circuit 310, a power storage device 330, and an electric motor 320. The power receiving circuit 210 includes a matching circuit 280, a rectifier circuit 260, and a resistance circuit 230.

The matching circuit 280 matches the impedance between the power receiving electrode 220 and the rectifier circuit 260. The matching circuit 280 may have the same configuration as the matching circuit 180 described, for example, with reference to FIGS. 26A to 26D. For the matching circuit 280 in the mobile body 200, it is possible to adopt a configuration in which the input side (left side in the figure) and the output side (right side in the figure) are inverted in each of the above configuration examples.

The rectifier circuit 260 converts the AC power output from the matching circuit 280 into DC power. FIG. 27 is a diagram schematically showing a configuration example of the rectifier circuit 260. The rectifier circuit 260 in this example is a full-wave rectifier circuit including a diode bridge and a smoothing capacitor. The rectifier circuit 260 may have other configurations, such as a half-wave rectifier circuit. The rectifier circuit 260 converts the received AC energy into DC energy that can be used by loads such as the power storage device 330 and the motor 320.

The power receiving control circuit 250 can be realized by a circuit including a processor and a storage medium such as a memory, such as an MCU. As described above, the power receiving control circuit 250 adjusts the resistance value of the resistance circuit 230 according to the operating state of the charge control circuit 310.

The charge control circuit 310 is connected between the resistance circuit 230 and the power storage device 330 to control charging and discharging of the power storage device 330.

FIG. 28 is a diagram showing a configuration example of the charge control circuit 310. The charge control circuit 310 in this example includes a cell balance controller 271, an analog front-end IC (AFE-IC) 272, a thermistor 273, a current detection resistor 274, an MCU 275, a communication driver IC 276, and a protection FET 277. including. The cell balance controller 271 is a circuit for equalizing the stored energy of each cell of the secondary battery including a plurality of cells. The AFE-IC272 is a circuit that controls the cell balance controller 271 and the protection FET 277 based on the cell temperature measured by the thermistor 273 and the current detected by the current detection resistor 274. The MCU 275 is a circuit that controls communication with other circuits via the communication driver IC 276. The configuration shown in FIG. 28 is only an example, and the circuit configuration may be changed according to the required function or characteristic.

The electric motor 320 is connected to the power storage device 330 and the charge control circuit 310, and is driven by the energy stored in the power storage device 330. The motor 320 can be any motor, such as a DC motor, a permanent magnet synchronous motor, an induction motor, a stepping motor, or a reluctance motor. The motor 320 rotates the wheels of the moving body via a shaft, gears, and the like to move the moving body 200. Depending on the type of motor, various circuits such as a rectifier circuit, an inverter circuit, and an inverter control circuit may be provided in front of the motor 320.

The power storage device 330 may be, for example, a secondary battery or a capacitor for power storage. As the secondary battery, for example, a lithium ion battery or a nickel hydrogen battery can be used. The capacitor for storage can be a high capacity and low resistance capacitor such as an electric double layer capacitor or a lithium ion capacitor. The mobile body 200 moves by driving the motor 320 by the electric power stored in the capacitor or the secondary battery.

When the mobile body 200 moves, the amount of electricity stored in the electricity storage device 330 decreases. Therefore, recharging is required to continue moving. Therefore, for example, when the charge amount falls below a predetermined threshold value during movement, the mobile body 200 charges from the power transmission device 100.

The sizes of the housing of the mobile body 200, the power transmission electrode 120, and the power reception electrode 220 in the present embodiment are not particularly limited, but may be set to the following sizes, for example. The length of each transmission electrode 120 (ie, the size in the Y direction) can be set, for example, in the range of 50 cm to 20 m. The width of each transmission electrode 120 (ie, the size in the X direction) can be set, for example, within the range of 5 cm to 2 m. The respective sizes of the housing of the moving body 200 in the moving direction and the lateral direction can be set within the range of, for example, 20 cm to 5 m. The size of the housing of the mobile body 200 in the moving direction may be set to less than half the length of each power transmission electrode 120 so that power can be supplied from the power transmission electrode 120 to two or more mobile bodies 200 at the same time. The length (that is, the size in the moving direction) of the power receiving electrode 220a can be set in the range of, for example, 5 cm to 2 m. The width (that is, the size in the lateral direction) of the power receiving electrode 220a can be set in the range of, for example, 2 cm to 2 m. The gap between the transmission electrodes 120 and the gap between the power receiving electrodes 220 can be set, for example, in the range of 1 mm to 40 cm. However, it is not limited to these numerical ranges.

In the above embodiment, the power transmission electrode 120 is laid on the ground or the floor surface, but the power transmission electrode 120 may be laid on a side surface such as a wall or an upper surface such as a ceiling. The arrangement and orientation of the power receiving electrode 220 of the mobile body 200 is determined according to the location and orientation in which the power transmission electrode 120 is laid.

FIG. 29A shows an example in which the power transmission electrode 120 is laid on a side surface such as a wall. In this example, the power receiving electrode 220 is arranged on the side of the moving body 200. FIG. 29B shows an example in which the power transmission electrode 120 is laid on the ceiling. In this example, the power receiving electrode 220 is arranged on the top plate of the moving body 200. As in these examples, there are various variations in the arrangement of the power transmission electrode 120 and the power reception electrode 220.

As described above, the wireless power transmission system according to the embodiment of the present disclosure can be used as a system for transporting goods in, for example, a warehouse or a factory. The mobile body 200 has a loading platform for loading articles, and functions as a trolley that autonomously moves in the factory and transports articles to a required place. However, the wireless power transmission system and the mobile body in the present disclosure are not limited to such applications, and may be used for various other applications. For example, the moving body is not limited to the AGV, and may be another industrial machine, a service robot, an electric vehicle, a multicopter (drone), or the like. Wireless power transfer systems can be used not only in factories or warehouses, but also in, for example, stores, hospitals, homes, roads, runways and anywhere else. Further, the power receiving device is not limited to a mobile body, and may be any portable device such as a charging pole, a smartphone, a tablet computer, or a laptop computer.

Hereinafter, an example of a wireless power transmission system in which the power receiving device is not equipped with a power device for movement will be described.

FIG. 30 is a perspective view schematically showing an example of a wireless power transmission system that supplies power to a portable power receiving device 400. FIG. 31 is a schematic cross-sectional view of this system.

As shown in FIG. 30, in this system, a portable power receiving device 400, not a mobile body, receives power from the power transmission device 100 and operates. Although two power receiving devices 400 are illustrated in FIG. 30, the number of power receiving devices 400 is arbitrary. The power receiving device 400 may be, for example, a portable charging pole. The power receiving device 400 is arranged and used on the power transmission sheet 190 included in the power transmission device 100. The power transmission sheet 190 includes a pair of power transmission electrodes 120 extending in one direction. The power receiving device 400 includes a power receiving sheet 240 facing the power transmission sheet 190 when in use. The power receiving sheet 240 includes a pair of power receiving electrodes 220. Electric power is transmitted wirelessly with the pair of power receiving electrodes 220 facing each other of the pair of power transmission electrodes 120. The power receiving device 400 is portable and can be slid along the direction in which the power transmission electrode 120 extends. The dimension of the power receiving device 400 in the direction in which the power transmission electrode 120 extends is less than half the length of the power transmission electrode 120. Therefore, two or more power receiving devices 400 can be arranged on the power transmission sheet 190 at the same time.

As shown in FIG. 31, the pair of power transmission electrodes 120 are connected to the power transmission circuit 110. Similar to the above-described embodiment, the power transmission circuit 110 supplies AC power to the pair of power transmission electrodes 120. As a result, AC energy is transmitted from the power transmission electrode 120 to the space. The power receiving device 400 includes a power receiving circuit 210, a power storage device 330, and a load 340 in addition to the power receiving sheet 240. The power receiving circuit 210 is connected to a pair of power receiving electrodes 220, and converts the AC power received by the power receiving electrodes 220 into DC power and outputs the power. The power storage device 330 stores the DC power output from the power receiving circuit 210. The load 340 is connected to the power storage device 330 and operates by the electric power stored in the power storage device 330. The load 340 is any device operated by electric power and may include, for example, an electric motor, a power unit, or a lighting device. When the power receiving device 400 is a charging pole, the power receiving device 400 may include one or more outlets for supplying power to other devices. Although not shown in FIG. 31, the power receiving device 400 has a function of adjusting impedance, as in the examples shown in FIGS. 8 to 12 and the like. As a result, it is possible to suppress heat generation and damage of the circuit element at the start of charging and stabilize the operation.

FIG. 32 is a diagram showing another example of the power receiving device 400. As shown in FIG. 32, the power receiving device 400 may be a smartphone 400A, a tablet computer 400B, or a laptop computer 400C. Not limited to these examples, the power receiving device 400 can be any portable device. Regardless of the type of the power receiving device 400, by applying the technique of the present disclosure, it is possible to suppress heat generation and damage of the circuit element at the start of charging and stabilize the operation.

The technology of the present disclosure can be used for any device driven by electric power. For example, the techniques of the present disclosure can be applied to electric vehicles such as automatic guided vehicles (AGVs) or portable devices such as charging poles, smartphones, tablet computers, or laptop computers.

30 Floor surface 100 Power transmission device 110 Power transmission circuit 120 Power transmission electrode 140 Detector 150 Power transmission control circuit 160 Inverter circuit 170 Switch 180 Matching circuit 200 Mobile unit (power receiving device)
210 Power receiving circuit 220 Power receiving electrode 230 Resistance circuit 232 Resistor 234 Switch 250 Power receiving control circuit 260 Rectifier circuit 280 Matching circuit 290 Voltage detector 300 Load 310 Charge control circuit 320 Electric motor 330 Power storage device 340 Equipment load 400 Power supply

Claims

A power receiving device used in a wireless power transmission system including a power transmitting device and a power receiving device.
A power receiving antenna that wirelessly receives AC power from the power transmission antenna of the power transmission device,
A power receiving circuit that converts the AC power received by the power receiving antenna into DC power and outputs it.
A load operated by the DC power output from the power receiving circuit, and a load that starts when the voltage of the DC power exceeds a predetermined starting voltage.
A resistance circuit connected between the power receiving circuit and the load, including a resistor connected in parallel with the load, and a resistance circuit.
A power receiving control circuit that controls the impedance of the resistance circuit so as to suppress fluctuations in the load impedance of the power receiving circuit caused by the power receiving device approaching the power transmission device and activating the load.
A power receiving device equipped with.
The power receiving device according to claim 1, wherein the power receiving control circuit controls the impedance of the resistance circuit so as to maintain the load impedance within a preset range.
The resistance circuit is
With a resistor connected in parallel with the load,
A switch connected in parallel with the load and in series with the resistor.
Including
The power receiving control circuit controls the impedance of the resistance circuit by controlling the switch.
The power receiving device according to claim 1 or 2.
The power receiving control circuit is
Before the load is activated, the switch is turned on and the switch is turned on.
After the load is activated, the switch is controlled so that the impedance of the resistance circuit increases.
After the power for transmission is supplied from the power transmission device, the switch is turned off.
The power receiving device according to claim 3.
The power receiving device according to claim 4, wherein the power receiving control circuit turns on the switch after the power transmission from the power transmitting device to the power receiving device is completed.
The power receiving device according to any one of claims 3 to 5, wherein the resistance value of the resistor is substantially equal to the resistance value of the load when power for power transmission is supplied from the power transmission device.
The resistance circuit includes a variable resistor connected in parallel with the load.
The power receiving control circuit controls the impedance of the resistance circuit by controlling the resistance value of the variable resistor.
The power receiving device according to claim 1 or 2.
The load includes a DC-DC converter.
The activation of the load is the activation of the DC-DC converter.
The power receiving device according to any one of claims 1 to 7.
A power transmission device used in a wireless power transmission system including a power transmission device and a power receiving device.
The power receiving device operates by a power receiving antenna, a power receiving circuit that converts the AC power received by the power receiving antenna into DC power and outputs it, and the DC power output from the power receiving circuit, and operates with the DC power voltage. With a load that starts when the specified starting voltage is exceeded,
The power transmission device
A power transmission circuit that converts the power supplied from the power supply into AC power for power transmission and outputs it.
A power transmission antenna that wirelessly transmits the AC power to the power receiving antenna,
A detector that detects the approach of the power receiving device to the power transmission device, and
It is a power transmission control circuit that controls the power transmission circuit, and when the approach of the power receiving device to the power transmission device is detected, the AC power output from the power transmission circuit is increased, and the input voltage of the load is set in advance. A power transmission control circuit that controls the power transmission circuit so that it is maintained within the set range.
A power transmission device equipped with.
The power transmission device according to claim 9, wherein the lower limit of the range is the starting voltage.
The power transmission device according to claim 9 or 10, wherein the upper limit of the range is the rated voltage of the load.
The power receiving device according to any one of claims 1 to 8.
With the power transmission device
A wireless power transmission system equipped with.
A wireless power transmission system including a power receiving device and a power transmitting device that supplies power to the power receiving device.
The power transmission device
Power transmission circuit and
A power transmission antenna electrically connected to the power transmission circuit,
The power transmission control circuit that controls the power transmission circuit and
A detector that detects the approach of the power receiving device and
Equipped with
The power receiving device is
With the power receiving antenna
A power receiving circuit electrically connected to the power receiving antenna and
The load electrically connected to the power receiving circuit and
Equipped with
The power transmission circuit outputs AC power to the power transmission antenna.
The power transmission antenna outputs the AC power to the power reception antenna, and the power transmission antenna outputs the AC power to the power reception antenna.
The power receiving antenna outputs the AC power to the power receiving circuit, and the power receiving antenna outputs the AC power to the power receiving circuit.
The power receiving circuit converts the AC power into DC power and outputs it to the load.
When the detector detects the approach of the power receiving device, the power transmission control circuit outputs the AC power so that the voltage input to the load is maintained within a preset range. Increase,
When the voltage input to the load exceeds a predetermined starting voltage, the load starts.
Wireless power transmission system.
The power receiving device is
A resistor circuit containing a resistor connected in parallel with the load,
A power receiving control circuit that controls the resistance circuit and controls the impedance of the resistance circuit so as to suppress fluctuations in the load impedance of the power receiving circuit caused by the activation of the load.
13. The wireless power transmission system according to claim 13.