JP2022012250A - Power reception device, power transmission device and wireless power transmission system - Google Patents

Abstract

To achieve communication from a power reception device to a power transmission device with a simple configuration.SOLUTION: The power reception device includes: a power reception antenna which receives AC power transmitted by radio from a power transmission antenna provided on the power transmission device; a rectifier circuit including a plurality of switching elements and a bridge circuit having a plurality of diodes respectively connected in parallel with the plurality of switching elements, so as to convert the AC power received by the power reception antenna into DC power to output the DC power; and a power reception control circuit which controls the plurality of switching elements according to information to be transferred to the power transmission device, to thereby control to modulate at least one of a current and a voltage at the power transmission device, so as to transfer the information to the power transmission device through the power reception antenna and the power transmission antenna.SELECTED DRAWING: Figure 5

Description

The present 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 electric 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 to 3 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 power transmission electrode to a power receiving electrode in a state where two or more power transmission electrodes and two or more power receiving electrodes face 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 4 discloses an example of a wireless power transmission system by an electric field coupling method.

In a wireless power transmission system, a configuration in which a power receiving device communicates with a power transmitting device is generally adopted for safety and stability of power transmission. For example, Patent Document 3 discloses an example of a wireless power transmission system that transmits a signal from a power receiving device to a power transmitting device by load modulation.

Japanese Unexamined Patent Publication No. 2014-79107 Japanese Unexamined Patent Publication No. 2019-176683 Japanese Unexamined Patent Publication No. 2017-055591 Japanese Unexamined Patent Publication No. 2018-108012

The present disclosure provides a technique for realizing communication from a power receiving device to a power transmitting device with a simpler configuration.

The power receiving device according to one aspect 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 is a bridge including a power receiving antenna that receives AC power wirelessly transmitted from a power transmitting antenna included in the power transmitting device, a plurality of switching elements, and a plurality of diodes connected in parallel to the plurality of switching elements. By controlling the rectifying circuit having a circuit and converting the AC power received by the power receiving antenna into DC power and outputting the AC power, and controlling the plurality of switching elements according to the information to be transmitted to the power transmission device. It comprises a power receiving control circuit that modulates at least one of a current and a voltage in the power transmitting device through the power receiving antenna and the power transmitting antenna and transmits the information to the power transmitting device.

Comprehensive or specific embodiments of the present disclosure may be implemented in systems, devices, methods, integrated circuits, computer programs, or recording media. Alternatively, it may be realized by any combination of a system, an apparatus, a method, an integrated circuit, a computer program and a recording medium.

According to the technique of the present disclosure, communication from a power receiving device to a power transmitting device can be realized with a simpler configuration.

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 structure of the wireless power transmission system shown in FIG. 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 structure of the wireless power transmission system shown in FIG. It is a block diagram which shows typically the structure of the wireless power transmission system by an exemplary embodiment. 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. It is a figure which shows the example of the waveform of the gate voltage G1 to G4 of four switching elements in the 1st operation mode. It is a figure which shows the 1st example of the waveform of the gate voltage G1 to G4 of four switching elements in a 2nd operation mode. It is a figure which shows typically the current which flows in the rectifier circuit when the switching operation for communication in the example of FIG. 11A is performed. It is a figure which shows the 2nd example of the waveform of the gate voltage G1 to G4 of four switching elements in a 2nd operation mode. It is a figure which shows typically the current which flows in the rectifier circuit when the switching operation for communication in the example of FIG. 12A is performed. It is a figure which shows the 3rd example of the waveform of the gate voltage G1 to G4 of four switching elements in the 2nd operation mode. It is a figure which shows typically the current which flows in the rectifier circuit when the switching operation for communication in the example of FIG. 13A is performed. It is a graph which shows the example of the time change of the input DC current of a power transmission circuit when a normal switching operation is performed. It is a graph which shows the example of the time change of the input DC current of a power transmission circuit at the time of switching between a normal switching operation and a switching operation for communication. It is a figure for demonstrating an example of the method of transmitting a plurality of kinds of information. It is a figure for demonstrating another example of the method of transmitting a plurality of kinds of information. It is a figure which shows the example of the method of transmitting binary information. It is a timing chart for demonstrating an example of operation of a power transmission device and a power receiving device. It is a flowchart which shows the example of the operation of a power receiving device. It is a flowchart which shows the other example of the operation of a power receiving device. It is a block diagram which shows the configuration example in which the impedance adjustment circuit is arranged between the rectifier circuit and the charge control circuit. It is a figure which shows the structural example of the impedance adjustment circuit. It is a figure which shows the example which includes the communication circuit which communicates with the external abnormality transmission system of a power receiving device. It is a figure which shows the other example of the structure of each bridge of a rectifier circuit. It is a figure which shows the example which the transmission electrode was laid on the side surface such as a wall. It is a figure which shows the example which the transmission electrode was laid on the ceiling.

(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"). Group refers to a transmission method in which power is transmitted wirelessly, that is, in a non-contact manner. 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 mobile body 10 provided with a power receiving device. The mobile body 10 in this example is an automated guided vehicle (AGV). The mobile body 10 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 mobile body 10 includes a pair of power receiving electrodes (not shown) facing the pair of power transmission electrodes 120a and 120b. The mobile body 10 receives AC power transmitted from the transmission electrodes 120a and 120b by a 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 mobile body 10. As a result, the moving body 10 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 mobile body 10. The mobile body 10 includes a power receiving device 200 and a load 300.

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 includes 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. be.

According to the wireless power transmission system as described above, the mobile body 10 can receive electric power wirelessly while moving along the transmission electrode 120. The mobile body 10 can move along the power transmission electrode 120 while maintaining a state in which the power transmission electrode 120 and the power reception electrode 220 are close to each other and face each other. As a result, the mobile body 10 can move while charging a power storage device such as a battery or a capacitor.

In the wireless power transmission system as described above, it may be required to transmit a signal from the power receiving device 200 to the power transmission device 100 from the viewpoint of safety and stability of power transmission. For example, when some abnormality occurs in the power receiving device 200 or the load 300, or when the power storage device is almost fully charged, the power receiving device 200 sends a notification to the power transmission device 100 to stop or suppress the power transmission. May be required. Alternatively, the power receiving device 200 may notify the power transmission device 100 of the operating state of the load 300 (for example, voltage or current), and the power transmission device 100 may be required to adjust the transmitted power according to the operating state of the load. ..

Various methods can be considered as a method of transmitting information from the power receiving device 200 to the power transmitting device 100. For example, a signal can be transmitted from the power receiving device 200 to the power transmitting device 100 by using a communication module conforming to a wireless communication standard such as ZigBee (registered trademark) or Bluetooth (registered trademark). Alternatively, by changing the impedance of the load modulation circuit provided in the power receiving device 200, the current or voltage in the power transmitting device 100 can be changed, thereby transmitting a signal.

However, in the above method, it becomes necessary to separately provide a circuit for information communication in the power receiving device 200. In addition, the wireless communication method may cause a delay in communication. With a simpler configuration, it is required to transmit a signal from the power receiving device 200 to the power transmitting device 100 at high speed. This problem is not limited to the above-mentioned wireless power transmission system based on the electric field coupling method, but may also occur in, for example, a wireless power transmission system using a magnetic field coupling method using magnetic field coupling between coils.

Based on the above considerations, the inventors have come up with the configuration of the embodiments of the present disclosure described below. 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, a rectifier circuit, and a power receiving control circuit. The power receiving antenna receives AC power wirelessly transmitted from a power transmission antenna included in the power transmission device. The rectifier circuit has a plurality of switching elements and a bridge circuit including a plurality of diodes connected in parallel to the plurality of switching elements, respectively, and converts the AC power received by the power receiving antenna into DC power. Output. The power receiving control circuit controls at least one of the current and the voltage in the power transmission device via the power receiving antenna and the power transmission antenna by controlling the plurality of switching elements according to the information to be transmitted to the power transmission device. Is modulated, and the information is transmitted to the power transmission device.

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. In an electric field coupling type wireless power transmission system, a power transmitting antenna includes two or more power transmitting electrodes, and a power receiving antenna includes two or more power receiving electrodes. On the other hand, in the magnetic field coupling type wireless power transmission system, the power transmission antenna includes a power transmission coil, and the power reception antenna includes a power reception coil. Although the present specification mainly describes an example of an electric field coupling type wireless power transmission system, the technique of the present disclosure can be similarly applied to a magnetic field coupling type wireless power transmission system.

According to the above configuration, a rectifier circuit having a plurality of switching elements and a bridge circuit including a plurality of diodes connected in parallel to the plurality of switching elements is used. By controlling a plurality of switching elements according to the information to be transmitted to the power transmission device, at least one of the current and the voltage in the power transmission device is modulated through the power receiving antenna and the power transmission antenna, and the information is transmitted to the power transmission device. can do. As a result, information can be transmitted from the power receiving device to the power transmission device without providing a communication circuit separately from the rectifier circuit.

The technique of the present disclosure may be used in combination with other communication techniques such as wireless communication or load modulation. That is, the power receiving device may include other communication means such as a wireless communication circuit or a load modulation circuit in addition to the above-mentioned rectifier circuit. By providing a plurality of communication means, it is possible to transmit various signals according to the purpose.

In the above configuration, the power receiving control circuit may include a signal generation circuit that generates a signal according to information to be transmitted to the power transmission device, and a drive circuit that controls each switching element of the rectifier circuit. The signal generation circuit can generate a signal according to, for example, the state of the electric power received by the power receiving device or the state of the load. Here, the load may include any device operated by electric power, for example, a power storage device charged by DC electric power output from a rectifying circuit, or an electric motor operated by the DC electric power.

The bridge circuit in the rectifier circuit may include a plurality of oxide semiconductor field effect transistors (MOSFETs) each functioning as the plurality of switching elements. In that case, the parasitic diodes of the plurality of MOSFETs function as the plurality of diodes. The power receiving control circuit can transmit the information to the power transmission device by controlling the gate voltage of each of the plurality of MOSFETs according to the information to be transmitted.

In the above configuration, one MOSFET has the functions of both a switching element and a diode. As described above, the switching element and the diode do not need to be provided separately, and may be realized by one circuit element.

The power receiving control circuit switches between a first operation mode in which the plurality of switching elements are controlled by the first switching pattern and a second operation mode in which the plurality of switching elements are controlled by the second switching pattern. Can be configured to transmit the information to the power transmission device. The first switching pattern may be, for example, a pattern that causes a rectifier circuit to execute a rectifier operation. In the first operation mode, the power receiving control circuit can cause the rectifier circuit to execute a rectifier operation by periodically changing the on / off state of each of the plurality of switching elements.

The second switching pattern can be any pattern different from the first switching pattern. By adding a second operation mode for driving the rectifier circuit in the second switching pattern, a desired signal can be transmitted to the power transmission device via the power receiving antenna and the power transmission antenna.

The power receiving control circuit transmits the information to the power transmission device by turning off all of the plurality of switching elements in the second operation mode so that a current flows through the plurality of diodes. You may.

The power receiving control circuit executes a rectifying operation on the rectifying circuit by periodically changing the on / off state of each of the plurality of switching elements at the first duty ratio in the first operation mode. In the second operation mode, the information may be transmitted to the power transmission device by periodically changing the on / off state of each of the plurality of switching elements at the second duty ratio. good.

The bridge circuit may include first and second input terminals to which the AC power is input and first and second output terminals to which the DC power is output. The plurality of switching elements are between a first switching element connected between the first input terminal and the first output terminal, and between the second input terminal and the first output terminal. A second switching element connected to, a third switching element connected between the first input terminal and the second output terminal, the second input terminal, and the second output. It may include a fourth switching element connected to and from the terminal. In the power receiving control circuit, in the first operation mode, the first and fourth switching elements are turned on, the second and third switching elements are turned off, and the first and fourth switching elements are switched. By periodically changing the state in which the element is turned off and the state in which the second and third switching elements are turned on, the rectifier circuit can be made to perform the rectification operation.

In the second operation mode, the power receiving control circuit has the first and second switching elements turned on, the third and fourth switching elements turned off, and the first and second switching elements. The information may be transmitted to the power transmission device by periodically changing the state in which the element is turned off and the state in which the third and fourth switching elements are turned on.

The power receiving control circuit may transmit the information to the power transmission device by periodically changing the first operation mode and the second operation mode. In this case, the signal can be transmitted to the power transmission device by changing the pattern of the periodic fluctuation between the first operation mode and the second operation mode.

The power receiving control circuit includes a first operation mode in which the plurality of switching elements are controlled by a first switching pattern, a second operation mode in which the plurality of switching elements are controlled by a second switching pattern, and a plurality of the above. The information may be transmitted to the power transmission device by switching between a third operation mode in which the switching element is controlled by the third switching pattern and the third operation mode. The power receiving control circuit may further operate in a fourth operation mode in which the plurality of switching elements are controlled by the fourth switching pattern. In this way, by driving the rectifier circuit in three or more different operation modes, various information can be transmitted to the power transmission device. The first operation mode may be a mode in which a normal rectification operation is performed, as described above. Each of the second to fourth operation modes may be the same as or different from any of the above-mentioned operation modes described as the second operation mode. Various information can be transmitted to the power transmission device by combining these operation modes.

The power receiving control circuit changes the length of the cycle for switching between the first operation mode and the second operation mode or the period of the second operation mode according to the information, thereby changing the cycle or the second operation mode. Different information may be transmitted to the power transmission device depending on the length of the period of the second operation mode.

The power receiving control circuit sets a rectification operation period that operates only in the first operation mode and a communication operation period that operates by switching between the first operation mode and the second operation mode, and the communication. By changing the time ratio of the period of operation in the second operation mode, different information may be transmitted to the power transmission device according to the time ratio. Alternatively, the power receiving control circuit switches between the first operation mode and the second operation mode according to the information to be transmitted during the communication operation period, so that the power receiving control circuit has a binary value according to the switching pattern. The signal may be transmitted to the power transmission device.

The power receiving device may further include a detector that detects at least one of the current, voltage, and power in the power receiving device. The power receiving control circuit may determine the information to be transmitted to the power transmission device based on at least one of the detected current, voltage, and power.

When the power receiving control circuit determines that at least one of the detected current, voltage, and power values is an abnormal value, the power receiving control circuit may determine a request for stopping power transmission as the information.

The power receiving control circuit may determine the information to be transmitted to the power transmission device based on the charging state of the power storage device charged by the DC power output from the rectifier circuit. For example, the power receiving control circuit may determine a request for stopping power transmission as the information when the amount of electricity stored in the electricity storage device exceeds a threshold value. The amount of electricity stored can be expressed, for example, by the charge rate (State of Charge: SOC), that is, the ratio of the current remaining capacity to the fully charged capacity or a percentage thereof. The amount of electricity stored can be estimated, for example, from the integral of the voltage applied to the energy storage device (meaning the effective value of the voltage, the same applies hereinafter) or the current flowing into the energy storage device.

The power transmission device according to one embodiment of the present disclosure is used in combination with the power receiving device in any of the above examples. The transmission device detects an AC output circuit, a transmission antenna that sends AC power output from the AC output circuit to the power receiving device, and a detector that detects at least one of current and voltage in the transmission device. It includes a transmission control circuit that reads information transmitted from the power receiving device based on the fluctuation of at least one of the current and the voltage, and controls the AC output circuit according to the information.

The detector may be arranged to detect a direct current input to the alternating current output circuit. The detector may be arranged so as to detect a DC voltage input to the AC output circuit. Alternatively, the detector may be configured to detect at least one of an AC current and an AC voltage output from the AC output circuit. In that case, the power transmission control circuit detects fluctuations in the amplitude of at least one of the AC current and the AC voltage, or fluctuations in the phase difference between the AC current and the AC voltage, and the information is based on the detection result. To read.

The power transmission control circuit may be configured to read the information based on the period of fluctuation of at least one of the current and the voltage in the power transmission device.

The wireless power transmission system according to the 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 may be mounted on a moving body, for example. As used in the present disclosure, the term "moving body" is not limited to a vehicle such as the above-mentioned automatic guided vehicle (AGV), but means any movable object driven by electric power. The moving body includes, for example, an electric vehicle equipped with an electric motor and 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, 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, and may be mounted on an electronic device such as a mobile phone.

Hereinafter, more specific embodiments 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. do not have. In the following description, components having the same or similar functions are designated by the same reference numerals.

(Embodiment)
FIG. 5 is a block diagram schematically showing a configuration of a wireless power transmission system according to an exemplary embodiment of the present disclosure. This wireless power transmission system includes a power transmission device 100 and a mobile body 10. The mobile body 10 includes a power receiving device 200, an electric motor 320, and a power storage device 330. FIG. 5 also shows a DC power supply 400, which is an external element of the wireless power transmission system. The mobile body 10 can be an automatic guided vehicle as shown in FIG.

The power transmission device 100 includes a power transmission circuit 110 which is an AC output circuit, a plurality of power transmission electrodes 120 functioning as a power transmission antenna, 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 power receiving device 200 includes a plurality of power receiving electrodes 220 that function as a power receiving antenna, a power receiving circuit 210, a power receiving control circuit 250, a detector 240, and a charging control circuit 270. The power receiving circuit 210 includes a matching circuit 280 and a rectifying circuit 260. The power receiving control circuit 250 includes a signal generation circuit 252 that generates a signal according to information to be transmitted to the power transmission device 100, and a drive circuit 254 that drives the rectifier circuit 260.

The details of each component will be described below.

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. 6 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 illustrated full-bridge type inverter circuit, a half-bridge type inverter circuit or another type of oscillation circuit such as class E may be used.

The frequency of power transfer may be set, for example, 50 Hz to 300 GHz, 20 kHz to 10 GHz in some examples, 20 kHz to 20 MHz in other examples, and 80 kHz to 14 MHz in other examples. 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. 7A to 7D are diagrams showing a configuration example of the matching circuit 180.

FIG. 7A 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. 7B is a diagram showing a second example of the matching circuit 180. In addition to the configuration shown in FIG. 7A, 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. 7A. According to such a configuration, the transmission efficiency can be further improved.

FIG. 7C 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. 7A. 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. 7A. Compared with the configuration of FIG. 7B, 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. 7D 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. 7A. 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. 7A. 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 configuration of the matching circuit 180 is not limited to the above example, and different circuit configurations may be adopted depending on the purpose. Further, if impedance matching is not necessary, the matching circuit 180 may be omitted.

The detector 140 detects at least one of the current and the voltage in the power transmission device 100. In the example of FIG. 5, the detector 140 detects the direct current input to the inverter circuit 160. The detector 140 may be configured to detect a DC voltage input to the inverter circuit 160, or an AC current or AC voltage output from the inverter circuit 160 or the matching circuit 180.

The power transmission control circuit 150 reads the information transmitted from the power receiving device 200 based on the fluctuation of at least one of the current and the voltage detected by the detector 140, and controls the inverter circuit 160 based on the information. The power transmission control circuit 150 can read the transmitted information, for example, based on the magnitude variation of the DC current or DC voltage detected by the detector 140. Alternatively, in a configuration in which the detector 140 detects an AC current or an AC voltage, the transmission control circuit 150 changes the amplitude of the detected AC current or the AC voltage, or the phase difference between the AC current and the AC voltage. Information can also be read based on. Further, the power transmission control circuit 150 can also read the transmitted information based on the period of fluctuation of at least one of the current and the voltage in the power transmission device 100. When the power transmission control circuit 150 receives, for example, a signal from the power receiving device 200 to the effect that power transmission should be stopped, the power transmission control circuit 150 stops the switching operation of the inverter circuit 160 and stops the output of AC power.

The matching circuit 280 in the power receiving device 200 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. 7A to 7D. For the matching circuit 280 in the power receiving device 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 configuration example shown in FIGS. 7A to 7D. The matching circuit 280 is not limited to the examples shown in FIGS. 7A to 7D, and various configurations can be adopted. Further, if there is no need for impedance matching, the matching circuit 280 may be omitted.

The rectifier circuit 260 converts the AC power output from the matching circuit 280 into DC power and outputs it. FIG. 8 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 bridge circuit 261 including a plurality of switching elements 263 and a smoothing capacitor 262. The rectifier circuit 260 shown in FIG. 8 includes four sets of switching elements 263 and diodes 264 connected in parallel to each other, and each set of switching elements 263 and diode 264 is realized by MOSFETs. In this case, the parasitic diode of the MOSFET functions as the diode 264. The switching element 263 may be composed of a transistor different from the MOSFET. In that case, the diode 264 is connected in parallel to each transistor. The rectifier circuit 260 may have other configurations, such as a half-wave rectifier circuit. The number of pairs of the switching element 263 and the diode 264 is not limited to four, and is determined depending on the configuration of the rectifier circuit 260. 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.

In the bridge circuit 261 in the example of FIG. 8, the bridge circuit 261 has a first input terminal Ti1 and a second input terminal Ti2 to which AC power is input, and a first output terminal To1 and a second output terminal To2 to output DC power. And. The plurality of switching elements 263 include first to fourth switching elements, and the plurality of diodes 264 include first to fourth diodes. The first switching element and the first diode are connected between the first input terminal Ti1 and the first output terminal To1. The second switching element and the second diode are connected between the second input terminal Ti2 and the first output terminal To1. The third switching element and the third diode are connected between the first input terminal Ti1 and the second output terminal To2. The fourth switching element and the fourth diode are connected between the second input terminal Ti2 and the second output terminal To2. Gate voltages G1 to G4 are applied to the gates of the first to fourth switching elements, respectively. The gate voltages G1 to G4 control the on (conducting) and off (non-conducting) states of the first to fourth switching elements.

The power receiving control circuit 250 includes a signal generation circuit 252 and a drive circuit 254. The signal generation circuit 252 may be a circuit including a processor and a storage medium such as a memory, such as an MCU. The signal generation circuit 252 determines the information to be transmitted to the power transmission device 100 based on the current or voltage detected by the detector 240, the current, voltage, or temperature detected by the charge control circuit 270, and uses the information. The corresponding signal is output to the drive circuit 254. The drive circuit 254 may include a gate driver that outputs a control signal that controls the on and off states of each switching element 263 in the rectifier circuit 260. The drive circuit 254 controls the on and off states of each switching element 263 based on the signal output from the signal generation circuit 252.

Normally, the power receiving control circuit 250 causes the rectifier circuit 260 to execute a rectifier operation by controlling a plurality of switching elements 263 in the rectifier circuit 260 with a predetermined switching pattern. As a result, DC power is output from the rectifier circuit 260. The DC power is supplied to the electric motor 320 and the power storage device 330 via the charge control circuit 270. The power receiving control circuit 250 can transmit a signal to the power transmission device 100 by changing the switching pattern of the rectifying circuit 260 while the rectifying operation is being performed. The power receiving control circuit 250 changes the switching pattern of each switching element 263 according to the information to be transmitted to the power transmission device 100. In the example of FIG. 8, the power receiving control circuit 250 controls the gate voltages G1 to G4 of the first to fourth MOSFETs according to the information to be transmitted to the power transmission device 100. As a result, the current in the power transmission device 100 can be modulated and information can be transmitted to the power transmission device 100.

The detector 240 is a measuring instrument that detects at least one of the current, voltage, and power in the power receiving device 200. In the example of FIG. 5, the detector 240 detects the DC current or DC voltage output from the rectifier circuit 260. The detector 240 may be provided at any place in the power receiving device 200 without being limited to the illustrated example. For example, the detector 240 may be provided between the power receiving electrode 220 and the power receiving circuit 210, inside the power receiving circuit 210, between the charge control circuit 270 and the load, or inside the charge control circuit 270.

The power receiving control circuit 250 determines the information to be transmitted to the power transmission device 100 based on at least one of the detected current, voltage, and power. The power receiving control circuit 250 may determine, for example, a request to stop power transmission as information to be transmitted to the power transmission device 100 when at least one of the detected current, voltage, and power values is an outlier. can. Alternatively, the power receiving control circuit 250 may determine the information to be transmitted to the power transmission device 100 based on the charging state of the power storage device 330. For example, when the amount of electricity stored in the electricity storage device 330 exceeds the threshold value, the request for stopping power transmission may be determined as the information. Instead of a detector that detects current, voltage, or power, a detector that detects the temperature around the load, such as a motor 320 or a power storage device 330, may be provided. In that case, the power receiving control circuit 250 can transmit a notification to the power transmission device 100 when the temperature shows an abnormal value.

The charge control circuit 270 is connected between the power receiving circuit 210 and the power storage device 330, and controls charging and discharging of the power storage device 330. FIG. 9 is a diagram showing a configuration example of the charge control circuit 270. The charge control circuit 270 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. In this example, the current detection resistor 274 or thermistor 273 may be used as the detector. In that case, the power receiving control circuit 250 may determine the information to be transmitted to the power transmission device 100 based on the current detected by the current detection resistor 274 or the temperature measured by the thermistor 273. The configuration shown in FIG. 9 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 270, 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 10. 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 power receiving device 200, which is a mobile body, drives and moves the motor 320 by the electric power stored in the capacitor or the secondary battery.

The sizes of the housing of the mobile body 10, 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 10 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 10 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 10 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.

Next, the operation of the wireless power transmission system in this embodiment will be described.

The power transmission device 100 transmits power to the power reception device 200 in a state where the plurality of power receiving electrodes 220 in the power receiving device 200 face each of the plurality of power transmission electrodes 120 in the power transmission device 100. The power transmission control circuit 150 drives the inverter circuit 160 to supply AC power to the power transmission electrode 120. The transmission electrode 120 sends the AC power to the space, and the power receiving electrode 220 receives at least a part of the power. The AC power received by the power receiving electrode 220 passes through the matching circuit 280 and is converted into DC power by the rectifier circuit 260. The DC power is supplied to the motor 320 and the power storage device 330 via the charge control circuit 270.

The power receiving device 200 in the present embodiment can transmit a signal to the power transmission device 100 by changing the switching pattern of the rectifier circuit 260 during the power receiving operation. The power transmission device 100 can read the signal based on the pattern of changes such as current or voltage in the power transmission device 100.

The power receiving control circuit 250 can switch between a first operation mode for causing the rectifier circuit 260 to perform a normal rectification operation and a second operation mode for transmitting information. In the first operation mode, the power receiving control circuit 250 controls a plurality of switching elements 263 by the first switching pattern. More specifically, the power receiving control circuit 250 causes the rectifying circuit 260 to execute the rectifying operation by periodically changing the on / off state of each of the plurality of switching elements 263 in the first operation mode. .. In the second operation mode, the power receiving control circuit 250 controls the plurality of switching elements 263 with a second switching pattern different from the first switching pattern. The power receiving control circuit 250 switches between the first operation mode and the second operation mode, for example, at a constant cycle.

FIG. 10 is a diagram showing an example of waveforms of gate voltages G1 to G4 applied to the gate of the switching element 263 in the first operation mode in which the normal rectification operation is performed. In this example, the power receiving control circuit 250 has the first state in which the first and fourth switching elements shown in FIG. 8 are turned on and the second and third switching elements are turned off, and the first and fourth switching. The element is turned off, and the second state in which the second and third switching elements are turned on is periodically changed. The frequency of this switching operation is set so as to substantially match the frequency of the AC power transmitted from the power transmission device 100. In the example shown in FIG. 10, a pulse voltage having a duty ratio of less than 50% is applied to the gate of each switching element 263. By such an operation, the rectifier circuit 260 converts the input AC power into DC power.

On the other hand, in the second operation mode for information transmission, the power receiving control circuit 250 controls each switching element 263 with a pattern different from the pattern shown in FIG. For example, the switching element 263 can be controlled by any of the following patterns.
(A) Turn off all switching elements 263 (b) Drive each switching element 263 with a duty ratio different from that of the first switching pattern (c) Switch on the combination of switching elements 263 at the same time. Make a combination different from the pattern

Hereinafter, each example will be described in more detail.

FIG. 11A is a diagram showing an example of waveforms of gate voltages G1 to G4 of each switching element 263 when all switching elements 263 of the rectifier circuit 260 are turned off in the second operation mode. In the example of FIG. 11A, the first operation mode in which the normal switching operation is performed and the second operation mode in which the switching operation for communication is performed are switched by turning on / off the trigger signal. In this example, in the second operating mode, all four switching elements 263 are set to off.

FIG. 11B is a diagram schematically showing a current flowing in the rectifier circuit 260 when the switching operation for communication in the example of FIG. 11A is performed. The left and right figures of FIG. 11B show the current paths in two states having opposite phases to each other. In this example, since all switching elements 263 are off, current flows through the plurality of diodes 264. In the following description, this operation may be referred to as "diode rectification operation". The forward resistance value of the diode 264 is higher than the resistance value of the switching element 263 when the switching element 263 is on. Therefore, by turning off all the switching elements 263, the current in the power transmission device 100 fluctuates, and information can be transmitted to the power transmission device 100. In this example, there is an advantage that a relatively large change can be caused in the current in the power transmission device 100.

FIG. 12A shows an example of waveforms of the gate voltages G1 to G4 of each switching element 263 when driving each switching element 263 of the rectifier circuit 260 with a duty ratio different from that of the first switching pattern in the second operation mode. It is a figure which shows. In this example, the ratio of the time during which each switching element 263 is turned on, that is, the duty ratio, is different between the first operation mode and the second operation mode. In the second operation mode, the combination of the two switching elements 263 that are turned on at the same time among the four switching elements 263 is the same as the combination in the first operation mode. The power receiving control circuit 250 periodically changes the on / off state of each of the plurality of switching elements 263 by the first duty ratio in the first operation mode. In the second operation mode, the power receiving control circuit 250 periodically changes the on / off state of each of the plurality of switching elements 263 by the second duty ratio.

FIG. 12B is a diagram schematically showing a current flowing in the rectifier circuit 260 when the switching operation for communication in the example of FIG. 12A is performed. In this example, in the second operating mode, current flows through both the switching element 263 and the diode 264. However, since the duty ratio in the second operation mode is lower than the duty ratio in the first operation mode, the current flowing through the rectifier circuit 260 is reduced. Information can be transmitted to the power transmission device 100 by transmitting the influence to the power transmission device 100. In this example, there is an advantage that the loss when the second switching operation is performed can be reduced as compared with the diode rectification operation described above.

FIG. 13A shows an example of waveforms of the gate voltages G1 to G4 of each switching element 263 when the combination of the switching elements 263 to be turned on at the same time is changed to a combination different from the first switching pattern in the second operation mode. It is a figure. In this example, the power receiving control circuit 250 is in a state where the first and second switching elements are turned on and the third and fourth switching elements are turned off in the second operation mode, and the first and second switching. The state in which the element is turned off and the third and fourth switching elements are turned on is periodically changed.

FIG. 13B is a diagram schematically showing a current flowing in the rectifier circuit 260 when the switching operation for communication in the example of FIG. 13A is performed. In this example, in the second operation mode, the recirculation operation in which the current flows through the first and second switching elements and the recirculation operation in which the current flows through the third and fourth switching elements are repeated. Is done. In this example, the stress on each circuit is relatively large, but there is an advantage that the current in the power transmission device 100 can be greatly changed.

Next, with reference to FIGS. 14A and 14B, an example of a change in current in the power transmission device 100 caused by a switching operation for communication will be described.

FIG. 14A is a graph showing an example of a time change of the input DC current of the power transmission circuit 110 when a normal switching operation is performed. FIG. 14B is a graph showing an example of the time change of the input DC current of the power transmission circuit 110 when the normal switching operation and the switching operation for communication are switched. As an example, FIG. 14B shows an example in which a diode rectification operation in which all four switching elements 263 are set to off is executed during a switching operation for communication, as shown in FIG. 11A. As shown in FIG. 14B, the input current of the power transmission circuit 110 changes when the operation mode is switched. The power transmission control circuit 150 can read the signal transmitted from the power receiving device 200 from the change in the value of the current detected by the detector 140. Alternatively, if the power receiving control circuit 250 periodically performs mode switching, the power transmission control circuit 150 reads the transmitted signal based on the frequency of the current fluctuation detected by the detector 140. You can also.

Even when a pattern different from the switching pattern shown in FIG. 11A is adopted, the transmitted signal can be read by the same principle. Further, the detector 140 is not limited to the input current of the power transmission circuit 110, and may be arranged so as to detect the input voltage of the power transmission circuit 110 or the AC current or AC voltage output from the power transmission circuit 110.

Next, an example of an operation of transmitting a plurality of types of information from the power receiving device 200 to the power transmitting device 100 will be described with reference to FIGS. 15A to 15C.

FIG. 15A is a diagram for explaining an example in which the power receiving device 200 changes the length or period of the communication operation according to the information to be transmitted to the power transmission device 100. In this example, the power receiving control circuit 250 periodically switches between a rectification operation period for executing a normal rectification operation and a communication operation period for executing a communication operation. In the example of FIG. 15A, n times the cycle of the transmitted AC power is set as one cycle, and the period corresponding to the m cycle in one cycle is set as the communication operation period. In this case, the ratio of the communication operation period to one cycle, that is, the duty ratio is m / n. When the frequency of the AC power output from the power transmission circuit 110 is, for example, 100 kHz, the period is 10 microseconds (μs). In this case, if 10 to 100 cycles are set as one cycle, the current in the power transmission device 100 can be changed in the order of 100 microseconds to 1 millisecond (ms). As an example, when n = 100 and m = 20, 20% of one cycle is allocated to the communication operation period. The power receiving control circuit 250 may change n, which determines the length of one cycle, or m, which determines the length of the communication operation period, according to the information to be transmitted. Thereby, a plurality of types of information can be transmitted to the power transmission device 100. In this way, the power receiving control circuit 250 determines the length of the cycle of switching between the first operation mode and the second operation mode or the period of operation in the second operation mode according to the information to be transmitted to the power transmission device 100. It may be changed. Thereby, different information can be transmitted to the power transmission device 100 depending on the period or the period of operation in the second operation mode.

FIG. 15B is a diagram for explaining another example of a method of transmitting a plurality of types of information. In this example, the power receiving control circuit 250 sets a rectification operation period that operates only in the first operation mode and a communication operation period that operates by switching between the first operation mode and the second operation mode. The power receiving control circuit 250 transmits different information according to the time ratio to the power transmission device 100 by changing the time ratio of the period of the communication operation period during which the second operation mode is operated. In the example of FIG. 15B, the ratio of the communication operation period to one cycle is 50%, and the ratio of the second operation mode period to the communication operation period is also 50%. The ratio of the period of the second operation mode to the communication operation period can be changed according to the information to be transmitted. Further, the ratio of the communication operation period to one cycle can be changed according to the information to be transmitted.

FIG. 15C is a diagram showing an example of a method of transmitting binary information from the power receiving device 200 to the power transmitting device 100. In this example, the power receiving control circuit 250 sets a fixed communication operation period in one cycle. During the communication operation period, the power receiving control circuit 250 switches between the first operation mode and the second operation mode according to the information to be transmitted, thereby transmitting a binary signal according to the switching pattern to the power transmission device 100. introduce. The determination of switching between the first operation mode and the second operation mode is made every unit period sufficiently shorter than the communication operation period. In the example of FIG. 15C, the unit period in which the first operation mode is executed is assigned to "0", and the unit period in which the second operation mode is executed is assigned to "1". Assuming that the number of unit periods included in the communication operation period in one cycle is N, N-bit data can be transmitted.

As described above, the power receiving control circuit 250 can change the switching pattern of the rectifier circuit 260 by various methods and transmit information to the power transmission device 100. By arbitrarily combining these methods, various information can be transmitted to the power transmission device 100.

The information transmitted from the power receiving device 200 to the power transmitting device 100 is diverse, and for example, the following information can be transmitted.
-Current, voltage, or power at any point in the power receiving device 200-Current, voltage, or power input to the load-Abnormal information of each circuit or load (for example, overvoltage or overcurrent)
-Information indicating the charging status of the power storage device 330 (for example, full charge, etc.)-The temperature of each circuit or load-Impedance setting value of the rectifying circuit 260 or other circuits-Anomalies notified from the external system (for example, mobile system) Error etc.)

The power transmission control circuit 150 of the power transmission device 100 can read the information transmitted from the power reception device 200 and perform the following control, for example.
-Stop of the inverter circuit 160-Change of control parameters (for example, frequency, dead time, etc.) of the inverter circuit 160-Increase / decrease of the input voltage of the AC / DC converter in the previous stage of the inverter circuit 160-Signal transmission to other equipment-Transmission Suspension, resumption of power transmission after a certain period of time (in the case of temperature information)

Hereinafter, as an example, an example of an operation in which the power receiving device 200 transmits a power transmission stop request to the power transmission device 100 when the power storage device 330 approaches a fully charged state will be described.

FIG. 16 is a timing chart for explaining the operation of the power transmission device 100 and the power reception device 200 in this example. FIG. 17 is a flowchart showing the operation of the power receiving device 200 in this example. In this example, when the voltage applied to the power storage device 330 (hereinafter referred to as “battery voltage”) exceeds the threshold value, the power receiving device 200 issues a power transmission stop request to the power transmission device 100, and the power transmission is stopped. More specifically, when the power transmission is started, the charge control circuit 270 measures the voltage applied to the power storage device 330 (step S101). The charge control circuit 270 compares the measured battery voltage with a preset threshold value and determines whether or not the battery is in a fully charged state (step S102). When the battery voltage exceeds the threshold value, the charge control circuit 270 determines that the power storage device 330 is in a fully charged state, and sets the fully charged flag to "1". When the full charge flag becomes "1", the power receiving control circuit 250 starts the communication operation by any of the above-mentioned methods (step S103). The power receiving control circuit 250 changes the switching pattern in the rectifier circuit 260 in a preset manner. Then, as shown by the dotted line frame in FIG. 16, the input current of the power transmission circuit 110 in the power transmission device 100 increases. When the power transmission control circuit 150 detects an increase in the current value for a certain period of time or longer, it determines that the power storage device 330 is fully charged, and stops driving the inverter circuit 160 to stop power transmission. As a result, the power supply to the power receiving device 200 is stopped, and overcharging is prevented. After that, the charge control circuit 270 determines whether or not the battery has escaped from the fully charged state (step S104). When the battery voltage falls below the threshold value again, the charge control circuit 270 determines that the battery has escaped from the fully charged state. In that case, the charge control circuit 270 returns the full charge flag to "0", the power transmission stop request ends, and the normal operation is restarted (step S105).

Next, as another example, an example of operation when power control for maintaining the power supplied to the power receiving device 200 within an appropriate range will be described.

FIG. 18 is a flowchart showing the operation of the power receiving device 200 in this example. In this example, after the power transmission is started, the detector 240 measures the power in the power receiving device 200 (step S201). The power receiving control circuit 250 determines whether or not the measured power is smaller than the first threshold value (step S202). The first threshold value can be set to a value that is about 5% smaller than the power value specified in the specifications, for example. If the measured power is smaller than the first threshold value, the process proceeds to step S211. If the measured power is equal to or greater than the first threshold value, the process proceeds to step S203. In step S203, the power receiving control circuit 250 determines whether or not the measured power is larger than the second threshold value, which is larger than the first threshold value. If the measured power is larger than the second threshold value, the process proceeds to step S221. If the measured power is equal to or less than the second threshold value, the process returns to step S201.

In step S211th, the power receiving control circuit 250 sends a signal requesting an increase in electric power to the power transmission device 100 by continuously switching between the first operation mode and the second operation mode (step S211). Here, the first operation mode is a mode in which a normal rectification operation is performed. The second operation mode may be, for example, a mode in which the diode rectification operation shown in FIGS. 11A and 11B is performed. The second operation mode may be different from the first operation mode, and is not limited to the mode in which the diode rectification operation is performed. The continuous switching between the first operation mode and the second operation mode causes a change in the current in the power transmission device 100. The power transmission control circuit 150 detects that a request for increasing power is issued from the pattern of change in the current, and increases the power transmission. The increase in the transmitted power can be performed by, for example, increasing the duty ratio of the pulse of the control signal input to each switching element of the inverter circuit 160. After a lapse of a certain period of time, the process returns to step S201.

In step S221, the power receiving control circuit 250 sends a signal requesting a reduction in power to the power transmission device 100 by continuously switching between the first operation mode and the third operation mode (step S221). Here, the third operation mode may be, for example, a mode in which the reflux operation shown in FIGS. 13A and 13B is performed. The third operation mode may be different from the first and second operation modes, and is not limited to the mode in which the reflux operation is performed. The continuous switching between the first operation mode and the third operation mode causes a change in the current in the power transmission device 100. The power transmission control circuit 150 detects that a request for power reduction has been issued from the pattern of change in the current, and reduces the power transmission. The reduction of the transmitted power can be performed by, for example, reducing the duty ratio of the pulse of the control signal input to each switching element of the inverter circuit 160. After a lapse of a certain period of time, the process returns to step S201.

In the example shown in FIG. 18, the power receiving control circuit 250 has a first operation mode in which the plurality of switching elements 263 in the rectifier circuit 260 are controlled by the first switching pattern, and the plurality of switching elements 263 in the second switching pattern. By switching between the second operation mode to be controlled and the third operation mode in which the plurality of switching elements 263 are controlled by the third switching pattern, a plurality of types of information are transmitted to the power transmission device 100. The power receiving control circuit 250 may be further configured to operate in a fourth operation mode in which a plurality of switching elements 263 are controlled by a fourth switching pattern different from the first to third switching patterns. For example, in order to execute both the operation shown in FIG. 17 and the operation shown in FIG. 18, the first to fourth operation modes may be switched. The pattern of change in current or voltage in the power transmitting device 100 depends on the switching pattern of the rectifier circuit 260 by the power receiving device 200. Data or a program that defines the correspondence between the notified information and the pattern of change in current or voltage in the power transmission device 100 is recorded in advance in the storage medium of the power transmission device 100. Using the data or program, the power transmission control circuit 150 can read the notified information from the detected current or voltage change pattern.

Next, another configuration example of the wireless power transmission system will be described.

FIG. 19 is a block diagram showing a configuration example in which the impedance adjusting circuit 230 is arranged between the rectifier circuit 260 and the charge control circuit 270. The impedance adjustment circuit 230 is a circuit capable of changing the impedance in response to an input control signal.

FIG. 20 is a diagram showing a configuration example of the impedance adjusting circuit 230. The impedance adjustment circuit 230 in this example is a DC / DC converter. The DC / DC converter in this example is a step-down converter (back converter) including two switches SW1 and SW2, two capacitors, and a reactor. The input impedance can be finely adjusted by the duty control of the high side switch SW1.

In this example, the drive circuit 254 of the power receiving control circuit 250 changes the impedance by changing the duty ratio of the control signal input to the high side switch SW1 included in the impedance adjusting circuit 230. As a result, the input impedance of the impedance adjusting circuit 230 as seen from the power transmission side can be changed, and the power transmission state of the system can be changed.

By adding the impedance adjustment circuit 230 as in this example, communication by the impedance adjustment circuit 230 becomes possible in addition to the communication by the rectifier circuit 260. As the number of communication means increases, it becomes possible to transmit a wider variety of signals.

FIG. 21 is a diagram showing an example in which the power receiving device 200 includes a communication circuit 290 that communicates with an external abnormal transmission system 500. The abnormality transmission system 500 includes, for example, a computer that manages the operation of the mobile body 10. When an abnormality occurs in the mobile system, the abnormality transmission system 500 transmits an error notification to the power receiving device 200. When the communication circuit 290 receives the error notification, the power receiving control circuit 250 drives the rectifier circuit 260 or the impedance adjusting circuit 230 in order to transmit a signal corresponding to the error content to the power transmission device 100. As a result, the signal corresponding to the error content can be transmitted to the power transmission device 100. The impedance adjustment circuit 230 may be excluded from the configuration shown in FIG. In that case, the signal can be transmitted to the power transmission device 100 by the switching control in the rectifier circuit 260.

In the above embodiment, the functions of the switching element 263 and the diode 264 in the bridge circuit 261 of the rectifier circuit 260 are realized by the MOSFET, but a switching element different from the MOSFET may be used. For example, as shown in FIG. 22, a configuration in which a switching element 263 and a diode 264, which are separate elements, are connected in parallel may be adopted. As shown in FIG. 22, a resistor 265 may be connected to the diode 264. By providing the resistor 265, it is possible to increase the fluctuation of the current or voltage in the power transmission device 100 due to the switching of the switching element 263.

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 10 is determined according to the location and orientation in which the power transmission electrode 120 is laid.

FIG. 23A 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 10. FIG. 23B 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 10. As in these examples, there are various variations in the arrangement of the power transmission electrode 120 and the power reception electrode 220.

In the above embodiments, the wireless power transmission system by the electric field coupling method has been described, but the technique of the present disclosure can be similarly applied to the wireless power transmission system by the magnetic field coupling method. In the wireless power transmission system by the magnetic field coupling method, a power transmission coil is used instead of the power transmission electrode 120, and a power reception coil is used instead of 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 a warehouse or a factory, for example. The moving body 10 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.

The techniques of the present disclosure can be applied to any power driven device. For example, it can be suitably used for electric vehicles such as automatic guided vehicles (AGVs) and portable devices.

10 Mobile 30 Floor 100 Transmission device 110 Transmission circuit 120 Transmission electrode 140 Detector 150 Transmission control circuit 160 Inverter circuit 180 Matching circuit 200 Power receiving device 210 Power receiving circuit 220 Power receiving electrode 230 Impedance adjustment circuit 240 Detector 250 Power receiving control circuit 252 Signal Generation circuit 254 Drive circuit 260 Rectification circuit 261 Bridge circuit 262 Smoothing capacitor 263 Switching element 264 Diode 265 Resistor 270 Charge control circuit 280 Matching circuit 290 Communication circuit 300 Load 310 Charge control circuit 320 Electric motor 330 Power storage device 400 Power supply 500 Abnormal transmission system

Claims (20)

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 receives AC power wirelessly transmitted from the power transmission antenna of the power transmission device, and
A rectifier circuit having a bridge circuit including a plurality of switching elements and a plurality of diodes connected in parallel to the plurality of switching elements, and converting the AC power received by the power receiving antenna into DC power and outputting the circuit. ,
By controlling the plurality of switching elements according to the information to be transmitted to the power transmission device, at least one of the current and the voltage in the power transmission device is modulated via the power receiving antenna and the power transmission antenna, and the information. With a power receiving control circuit that transmits power to the power transmission device,
A power receiving device equipped with. The bridge circuit includes a plurality of MOSFETs, each of which functions as the plurality of switching elements.
The plurality of diodes are parasitic diodes of the plurality of MOSFETs, and the plurality of diodes are
The power receiving control circuit transmits the information to the power transmission device by controlling the gate voltage of each of the plurality of MOSFETs according to the information.
The power receiving device according to claim 1. The power receiving control circuit is
A first operation mode in which the plurality of switching elements are controlled by the first switching pattern, and
A second operation mode in which the plurality of switching elements are controlled by the second switching pattern, and
The power receiving device according to claim 1 or 2, wherein the information is transmitted to the power transmission device by switching between. The power receiving control circuit is
In the first operation mode, the rectifier circuit is made to execute a rectifier operation by periodically changing the on / off state of each of the plurality of switching elements.
In the second operation mode, the information is transmitted to the power transmission device by turning off all of the plurality of switching elements so that a current flows through the plurality of diodes.
The power receiving device according to claim 3. The power receiving control circuit is
In the first operation mode, the rectifier circuit is made to execute the rectification operation by periodically changing the on / off state of each of the plurality of switching elements by the first duty ratio.
In the second operation mode, the information is transmitted to the power transmission device by periodically changing the on / off state of each of the plurality of switching elements at the second duty ratio.
The power receiving device according to claim 3. The bridge circuit includes first and second input terminals to which the AC power is input, and first and second output terminals to which the DC power is output.
The plurality of switching elements are
A first switching element connected between the first input terminal and the first output terminal, and
A second switching element connected between the second input terminal and the first output terminal, and
A third switching element connected between the first input terminal and the second output terminal, and
A fourth switching element connected between the second input terminal and the second output terminal, and
Including
The power receiving control circuit is
In the first operation mode, the first and fourth switching elements are turned on, the second and third switching elements are turned off, and the first and fourth switching elements are turned off. By periodically changing the state in which the second and third switching elements are turned on, the rectifier circuit is made to execute a rectifier operation.
In the second operation mode, the first and second switching elements are turned on, the third and fourth switching elements are turned off, and the first and second switching elements are turned off. The information is transmitted to the power transmission device by periodically changing the state in which the third and fourth switching elements are turned on.
The power receiving device according to claim 3. The power receiving control circuit is
In the first operation mode, the rectifier circuit is made to execute a rectifier operation by changing the on / off state of each of the plurality of switching elements.
By periodically changing the first operation mode and the second operation mode, the information is transmitted to the power transmission device.
The power receiving device according to claim 3. The power receiving control circuit is
A first operation mode in which the plurality of switching elements are controlled by the first switching pattern, and
A second operation mode in which the plurality of switching elements are controlled by the second switching pattern, and
A third operation mode in which the plurality of switching elements are controlled by a third switching pattern, and
By switching the above, the information is transmitted to the power transmission device.
The power receiving device according to claim 1 or 2. The power receiving control circuit changes the length of the cycle for switching between the first operation mode and the second operation mode or the period of the second operation mode according to the information, thereby changing the cycle or the second operation mode. The power receiving device according to claim 3, wherein different information is transmitted to the power transmission device depending on the length of the period of the second operation mode. The power receiving control circuit is
A rectification operation period that operates only in the first operation mode and a communication operation period that operates by switching between the first operation mode and the second operation mode are set.
By changing the time ratio of the period during which the communication operation period is operated in the second operation mode, different information is transmitted to the power transmission device according to the time ratio.
The power receiving device according to claim 3. The power receiving control circuit is
A rectification operation period that operates only in the first operation mode and a communication operation period that operates by switching between the first operation mode and the second operation mode are set.
By switching between the first operation mode and the second operation mode according to the information to be transmitted in the communication operation period, a binary signal corresponding to the switching pattern is transmitted to the power transmission device. ,
The power receiving device according to claim 3. Further equipped with a detector for detecting at least one of the current, voltage, and power in the power receiving device.
The power receiving control circuit determines the information to be transmitted to the power transmission device based on at least one of the detected current, voltage, and power.
The power receiving device according to any one of claims 1 to 11. The power receiving device according to claim 12, wherein the power receiving control circuit determines a request for stopping power transmission as the information when the detected at least one value of the current, voltage, and power is an abnormal value. .. One of claims 1 to 13, wherein the power receiving control circuit determines the information to be transmitted to the power transmission device based on the charging state of the power storage device charged by the DC power output from the rectifying circuit. The power receiving device described in. The power receiving device according to claim 14, wherein the power receiving control circuit determines a request for stopping power transmission as the information when the storage amount of the power storage device exceeds a threshold value. A power transmission device used in combination with the power receiving device according to any one of claims 1 to 15.
AC output circuit and
A power transmission antenna that sends AC power output from the AC output circuit to the power receiving device, and
A detector that detects at least one of the current and voltage in the power transmission device,
A power transmission control circuit that reads information transmitted from the power receiving device based on the detected fluctuation of at least one of the current and voltage, and controls the AC output circuit according to the information.
A power transmission device equipped with. 16. The detector detects at least one of a DC current and a DC voltage input to the AC output circuit, and reads the information based on the fluctuation of the DC current and the at least one of the DC voltage. The power transmission device described in. The detector detects at least one of the AC current and the AC voltage output from the AC output circuit, and detects the AC current and the AC voltage.
The power transmission control circuit reads the information based on the fluctuation of the amplitude of the AC current and the at least one of the AC voltage, or the fluctuation of the phase difference between the AC current and the AC voltage.
The power transmission device according to claim 16. The power transmission device according to claim 16, wherein the power transmission control circuit reads the information based on the cycle of the fluctuation of the current and the voltage in the power transmission device. The power receiving device according to any one of claims 1 to 15.
The power transmission device according to any one of claims 16 to 19.
A wireless power transmission system equipped with.

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