JP6593648B2 - Power receiving apparatus and wireless power transmission system - Google Patents

Description

  The present disclosure relates to a power receiving device used in a wireless power transmission system that wirelessly transmits power.

  In recent years, development of wireless (contactless) power transmission technology for transmitting power wirelessly (contactlessly) to devices with mobility, such as a mobile phone or an electric vehicle, has been promoted. For example, Patent Document 1 discloses a non-contact power transmission system that can control the voltage after rectification of power transmitted in a non-contact manner to be constant.

JP 2007-336717 A

  Conventional wireless power transmission systems generally have high transmission efficiency at heavy loads (high power), but low transmission efficiency at low loads (low power). For this reason, there is a problem that power efficiency per hour is lowered when power is supplied to a load in which many light load states occur.

In order to solve the above problem, a power receiving device according to one embodiment of the present disclosure is provided.
A power receiving device that receives the AC power from a power transmission device including a power transmission antenna that wirelessly transmits AC power,
A power receiving antenna for receiving the AC power;
A rectifier circuit for converting the AC power into DC power;
A detection circuit for detecting a value of the DC power;
A load driven by the DC power;
A battery for storing the DC power;
i) connection / disconnection between the rectifier circuit and the load; and ii) a switching circuit that switches connection / disconnection between the load and the capacitor;
A control circuit for controlling the power receiving device,
The control circuit includes:
First, detection is performed using the detection circuit in a state where the rectifier circuit and the load are connected, the rectifier circuit and the capacitor are disconnected, and the DC power is supplied from the rectifier circuit to the load. Determining whether the value of the direct-current power that has been obtained is equal to or less than a power threshold;
When the value of the DC power is less than or equal to the power threshold, it is determined that the AC power of a predetermined value or more is not required for driving the load, the rectifier circuit and the load are disconnected, and Controlling the switching circuit to connect a load and the capacitor;
The load is driven by the DC power charged in the capacitor.

  The comprehensive or specific aspect described above may be realized by a system, a method, an integrated circuit, a computer program, or a recording medium. Alternatively, the present invention 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 one aspect of the present disclosure, in a low load state where the transmission efficiency of wireless power transmission is low, the load is driven by the capacitor, and power transmission by wireless power transmission is performed only in a load state where the efficiency is high or higher. To be implemented. Thereby, it becomes possible to improve the power efficiency per time.

1 is a block diagram illustrating a configuration example (comparative example) of a wireless power transmission system 10. FIG. It is a figure which shows an example of the power-efficiency characteristic in the wireless power transmission which has a general structure like a comparative example. It is a figure which shows an example of the time change of the rotational speed of a motor, and the electric current which flows into a motor, when load is a motor. 1 is a block diagram illustrating a configuration of a wireless power transmission system according to a first embodiment of the present disclosure. It is a figure which shows an example of the equivalent circuit of the power transmission antenna 110 and the power receiving antenna 210 which have a structure of a series resonance circuit. 3 is a diagram illustrating a configuration example of an inverter circuit 130. FIG. FIG. 6 is a diagram illustrating another configuration example of the inverter circuit 130. 3 is a diagram illustrating a first configuration example of a switching circuit 240. FIG. 6 is a diagram illustrating a second configuration example of the switching circuit 240. FIG. 6 is a diagram illustrating a third configuration example of the switching circuit 240. FIG. 6 is a diagram illustrating a fourth configuration example of the switching circuit 240. FIG. It is a figure which shows the state in which the rectifier circuit 230 and the load 320 are connected, the rectifier circuit 230 and the battery 310 are not connected, and the load 320 and the battery 310 are not connected. It is a figure which shows the state which the rectifier circuit 230 and the load 320 were connected, the rectifier circuit 230 and the electrical storage device 310 were connected, and the load 320 and the electrical storage device 310 were connected. The rectifier circuit 230 and the load 320 are not connected, the rectifier circuit 230 and the capacitor 310 are not connected, and the load 320 and the capacitor 310 are connected. The rectifier circuit 230 and the load 320 are not connected, the rectifier circuit 230 and the capacitor 310 are connected, and the load 320 and the capacitor 310 are not connected. It is a figure which shows the power transmission control sequence in a comparative example. It is a figure which shows an example of the power transmission control sequence in this embodiment. It is a figure which shows the other example of the power transmission control sequence in this embodiment. It is a figure which shows the example of a power-efficiency characteristic. It is a figure which shows the example of the relationship between the time change of the electric power supplied from the receiving circuit 220, and the voltage (or electrical storage amount) of the electrical storage device, and the electric power supply state in each timing, and the state of an electrical storage switch. 5 is a flowchart illustrating an example of a power path switching operation during load driving executed by the power reception control circuit 250. 10 is a flowchart illustrating another example of a power path switching operation during load driving executed by the power reception control circuit 250. 6 is a flowchart illustrating an example of a charging process when power supply to a load 420 executed by a power reception control circuit 250 is stopped. 10 is a flowchart illustrating another example of charging processing when power supply to a load 420 executed by the power reception control circuit 250 is stopped.

(Knowledge that became the basis of this disclosure)
Prior to describing the embodiments of the present disclosure, the knowledge underlying the present disclosure will be described.

  FIG. 1 is a block diagram illustrating a configuration example (comparative example) of the wireless power transmission system 10. The wireless power transmission system 10 includes a power transmission device 100 and a power reception device 200. FIG. 1 also shows a power supply 50 and a load driving device 300 which are external elements of the wireless power transmission system 10. The power supply 50 and the load driving device 300 may be included in the wireless power transmission system 10.

  The power transmission device 100 includes a power transmission antenna 110, an inverter circuit 130, a power transmission control circuit 150, and a power transmission side receiver 180. The power receiving apparatus 200 includes a power receiving antenna 210, a rectifier circuit (rectifier) 230, a power reception control circuit 250, and a power reception side transmitter 280. The load driving device 300 includes a power storage device (power storage device) 310 and a power unit 330.

  The power transmitting antenna 110 and the power receiving antenna 210 are resonators having a coil and a capacitor. Electric power is transmitted in a non-contact manner by magnetic field coupling between the coil of the power transmission antenna 110 and the coil of the power reception antenna 210.

  The inverter circuit 130 is connected between the power supply 50 and the power transmission antenna 110. The inverter circuit 130 converts the DC power supplied from the power supply 50 into AC power and supplies the AC power to the power transmission antenna 110. The inverter circuit 130 is controlled by the power transmission control circuit 150.

  The rectifier circuit 230 is connected between the power receiving antenna 210 and the battery 310. The rectifier circuit 230 converts the AC power received by the power receiving antenna 210 into DC power and supplies it to the battery 310. The power reception control circuit 250 detects the voltage value of the DC power output from the rectifier circuit 230 and causes the power reception side transmitter 280 to transmit information on the voltage value.

  The power transmission control circuit 150 adjusts the voltage of the AC power output from the inverter circuit 130 based on the voltage information on the power receiving device 200 side received by the power transmission side receiver 180. Thereby, feedback control is performed to keep the DC voltage supplied to the load driving device 300 constant.

  The load driving device 300 includes a power storage device 310 such as a battery (secondary battery) or a capacitor, and a power device 330 such as a motor. The battery 310 is charged with the DC power output from the rectifier circuit 230. Power device 330 is driven by electric power stored in power storage device 310.

  The inventors of the present invention have found that the configuration of the comparative example has a problem that power transmission efficiency is reduced at low load (that is, at low power). Hereinafter, this problem will be described.

  FIG. 2A is a diagram illustrating an example of power-efficiency characteristics in wireless power transmission having a general configuration like the above-described comparative example. Generally, the wireless power transmission system is designed so as to be able to cope with a light load state to a heavy load state while placing importance on the peak efficiency at the time of heavy load (at the time of high power). That is, the impedance of each circuit in the power transmitting device 100 and the power receiving device 200 is set so that the peak efficiency at the time of heavy load is as high as possible. As a result, as shown in FIG. 2A, the transmission efficiency is high when the transmission power is large, but the transmission efficiency is generally low when the transmission power is small. As described above, since the efficiency tends to decrease at the time of light load (low power), the power efficiency per hour becomes low when power is supplied to a load (for example, a motor) in which many light load conditions occur. There was a problem.

  FIG. 2B is a diagram illustrating an example of a temporal change in the rotational speed of the motor and the current flowing through the motor when the load is a motor. When the load is a motor, generally, as shown in FIG. 2B, a period during which the rotation speed of the motor is kept constant, that is, a period of low torque (low load) is long. For this reason, a light load state in which the current flowing through the motor is small frequently occurs. In this case, since the state where the transmission efficiency of the wireless power transmission system is low becomes long, the power efficiency per time is low.

  The present inventors have found the above-mentioned problem and studied a configuration for solving this problem. The present inventors have found that the above problem can be solved by appropriately switching the mutual connection state of the rectifier circuit, the capacitor, and the load according to the magnitude of the driven load (or electric power).

  Based on the above considerations, the present inventors have arrived at each aspect disclosed below.

A power receiving device according to an aspect of the present disclosure is provided.
A power receiving device that receives the AC power from a power transmission device including a power transmission antenna that wirelessly transmits AC power,
A power receiving antenna for receiving the AC power;
A rectifier circuit for converting the AC power into DC power;
A detection circuit for detecting a value of the DC power;
A load driven by the DC power;
A battery for storing the DC power;
i) connection / disconnection between the rectifier circuit and the load; and ii) a switching circuit that switches connection / disconnection between the load and the capacitor;
A control circuit for controlling the power receiving device,
The control circuit includes:
First, detection is performed using the detection circuit in a state where the rectifier circuit and the load are connected, the rectifier circuit and the capacitor are disconnected, and the DC power is supplied from the rectifier circuit to the load. Determining whether the value of the direct-current power that has been obtained is equal to or less than a power threshold;
When the value of the DC power is less than or equal to the power threshold, it is determined that the AC power of a predetermined value or more is not required for driving the load, the rectifier circuit and the load are disconnected, and Controlling the switching circuit to connect a load and the capacitor;
The load is driven by the DC power charged in the capacitor.

According to the above aspect,
The control circuit first places the rectifier circuit and the load in a connected state and puts the rectifier circuit and the capacitor in a non-connected state (not connected). As a result, the DC power is supplied from the rectifier circuit to the load. In this state, it is determined whether or not the value of the DC power detected using the detection circuit is equal to or lower than a predetermined threshold (power threshold). When the value of the DC power is less than or equal to the power threshold, it is determined that the AC power of a predetermined value or more is not required for driving the load, the rectifier circuit and the load are disconnected, and The switching circuit is controlled so as to connect a load and the battery. Then, the load is driven by the DC power charged in the capacitor.

  Thereby, in the low power state, the power supply from the rectifier circuit to the load is stopped, and the power supply from the capacitor to the load is started. As a result, power supply by wireless power transmission in a low power state with low efficiency can be avoided, and the efficiency of the entire system can be improved.

  Here, the load includes, for example, a motor. “A state where the predetermined amount or more of the AC power is not required for driving the load” means, for example, a state in which the change in the rotation speed of the motor is within a predetermined range for a certain period of time, or the stop of rotation of the motor is maintained. Including the state to be

A wireless power transmission system according to another aspect of the present disclosure is provided.
A power receiving device that receives the AC power from a power transmission device including a power transmission antenna that wirelessly transmits AC power,
A power receiving antenna for receiving the AC power;
A rectifier circuit for converting the AC power into DC power;
A first detection circuit for detecting a value of the DC power;
A load driven by the DC power;
A battery for storing the DC power;
A second detection circuit for detecting a storage amount of the capacitor;
i) connection / disconnection between the rectifier circuit and the load, ii) connection / disconnection between the rectifier circuit and the capacitor, and iii) a switching circuit that switches connection / disconnection between the load and the capacitor. When,
A control circuit for controlling the power receiving device,
The control circuit includes:
First, the rectifier circuit and the load are connected, the rectifier circuit and the capacitor are disconnected, and the load and the capacitor are disconnected, and the DC power is supplied from the rectifier circuit to the load In a state, it is determined whether or not the value of the DC power detected using the first detection circuit is equal to or lower than a power threshold;
When the value of the DC power is equal to or less than the power threshold, it is determined that the AC power of a predetermined level or more is not required for driving the load, the rectifier circuit and the load are connected, and the rectification Connecting the circuit and the capacitor, and controlling the switching circuit to connect the load and the capacitor;
When the storage device has a storage amount equal to or greater than a first storage threshold, the rectifier circuit and the load are disconnected, the rectifier circuit and the capacitor are disconnected, and the load and the capacitor are connected The switching circuit is controlled to a state, and the load is driven by the DC power charged in the battery.

According to the above aspect,
The control circuit first connects the rectifier circuit and the load, disconnects the rectifier circuit and the capacitor, and disconnects the load and the capacitor. As a result, the DC power is supplied from the rectifier circuit to the load. In this state, it is determined whether or not the value of the DC power detected using the first detection circuit is equal to or lower than a power threshold value. When the value of the DC power is less than or equal to the power threshold, it is determined that the AC power of a predetermined value or more is not required for driving the load, and the rectifier circuit and the load are connected, A rectifier circuit and the battery are connected, and the switching circuit is controlled so that the load and the battery are connected. That is, in a low power state, not only the load but also the capacitor is fed (charged) from the rectifier circuit, and is also fed from the capacitor to the load.

  Further, when the storage device has a storage amount equal to or greater than a first storage threshold, the control circuit disconnects the rectifier circuit and the load, disconnects the rectifier circuit and the capacitor, and The switching circuit is controlled to connect the load and the battery. As a result, power supply from the rectifier circuit to the load and charging of the capacitor are stopped, and the load is driven by the DC power charged in the capacitor.

  As a result, the battery is charged in a low power state, and when the amount of electricity stored in the battery is sufficiently large, power supply from the rectifier circuit to the load and the battery can be stopped and power can be supplied from the battery to the load. . As a result, power supply by wireless power transmission in a low power state with low efficiency can be suppressed, and the efficiency of the entire system can be improved.

  Note that “the capacitor has a storage amount equal to or higher than the first storage threshold value” is equivalent to the voltage of the capacitor being equal to or higher than a predetermined threshold value (first voltage threshold value). The voltage of the capacitor increases with the amount of charge. Therefore, it can be determined whether or not “the storage battery has a storage amount equal to or higher than the first storage threshold value” by determining whether or not the voltage of the storage battery is equal to or higher than the first voltage threshold value.

  In this aspect, the control circuit disconnects the rectifier circuit and the load when the storage device does not have a storage amount equal to or greater than the first storage threshold (that is, when the storage amount is insufficient). The switching circuit may be controlled to connect the rectifier circuit and the capacitor, and the load and the capacitor are disconnected, and the capacitor may be charged with the DC power from the rectifier circuit. Good.

  As a result, when the amount of electricity stored in the capacitor is insufficient, power supply from the rectifier circuit to the load and power supply from the capacitor to the load are stopped, and power supply (charging) from the rectifier circuit to the capacitor is performed with priority. Can do.

  Alternatively, the control circuit connects the rectifier circuit and the load and connects the rectifier circuit and the capacitor when the capacitor does not have a storage amount equal to or greater than the first storage threshold value. And controlling the DC power from the rectifier circuit to charge the battery.

  As a result, when the amount of electricity stored in the capacitor is insufficient, the capacitor can be charged with DC power from the rectifier circuit without being fed from the capacitor to the load, and can be fed to the load.

  Alternatively, the control circuit connects the rectifier circuit and the load when the storage amount of the capacitor becomes equal to or less than a second storage threshold after the supply of the DC power from the capacitor to the load is started. Then, the rectifier circuit and the battery may be connected, the DC power may be supplied from the rectifier circuit to the load, and the battery may be charged with the DC power from the rectifier circuit. The second power storage threshold may be a value equal to or lower than the first power storage threshold, for example.

  As a result, after the power supply from the capacitor to the load is started, when the amount of stored power decreases, the power supply from the capacitor to the load is stopped, and instead, the power supply (charging) from the rectifier circuit to the load and the capacitor is started. . Thereby, it is possible to switch between a state where power is supplied from the capacitor to the load and a state where the capacitor is charged according to the amount of stored electricity.

  Note that “the capacitor has a storage amount equal to or higher than the second storage threshold value” is equivalent to the voltage of the capacitor being equal to or higher than a predetermined threshold value (second voltage threshold value). By determining whether or not the voltage of the battery is equal to or higher than the second voltage threshold, it can be determined whether or not “the battery has a power storage amount equal to or higher than the second power storage threshold”.

A wireless power transmission system according to still another aspect of the present disclosure is provided.
A power receiving device that receives the AC power from a power transmission device including a power transmission antenna that wirelessly transmits AC power,
A power receiving antenna for receiving the AC power;
A rectifier circuit for converting the AC power into DC power;
A detection circuit for detecting a value of the DC power;
A load driven by the DC power;
A battery for storing the DC power;
A switching circuit that switches connection / disconnection between the load and the capacitor;
A control circuit for controlling the power receiving device,
The control circuit includes:
First, whether or not the value of the DC power detected using the detection circuit is equal to or less than a threshold value in a state where the load and the battery are disconnected and the DC power is supplied from the rectifier circuit to the load Determine whether
When the value of the DC power is equal to or less than the threshold value, the switching circuit determines that the AC power of a predetermined value or more is not required for driving the load, and connects the load and the battery. And transmitting a power transmission stop signal for stopping transmission of the AC power from the power transmission device to the power reception device to the power transmission device,
The load is driven by the DC power charged in the capacitor.

  According to the above aspect, the control circuit first detects the detection circuit using the detection circuit in a state in which the load and the battery are disconnected and the DC power is supplied from the rectifier circuit to the load. It is determined whether or not the value of the DC power is equal to or less than a threshold value. Then, when the value of the DC power is equal to or less than the threshold value, it is determined that the AC power of a predetermined value or more is not required for driving the load, and the load is connected to the capacitor. A switching circuit is controlled, and a power transmission stop signal for stopping transmission of the AC power from the power transmission device to the power reception device is transmitted to the power transmission device. Then, the load is driven by the DC power charged in the capacitor. The power transmission control circuit in the power transmission device receives the power transmission stop signal and stops power transmission using the inverter circuit.

  Thereby, when it will be in a low electric power state, power transmission can be stopped and the electric power feeding from a capacitor | condenser can be started. As a result, power supply by wireless power transmission in a low power state with low efficiency can be avoided, and the efficiency of the entire system can be improved.

A wireless power transmission system according to still another aspect of the present disclosure is provided.
A power receiving device that receives the AC power from a power transmission device including a power transmission antenna that wirelessly transmits AC power,
A power receiving antenna for receiving the AC power;
A rectifier circuit for converting the AC power into DC power;
A first detection circuit for detecting a value of the DC power;
A load driven by the DC power;
A battery for storing the DC power;
A second detection circuit for detecting a storage amount of the capacitor;
A switching circuit that switches connection / disconnection between the load and the capacitor;
A control circuit for controlling the power receiving device,
The control circuit includes:
First, in a state where the load and the capacitor are disconnected and the DC power is supplied from the rectifier circuit to the load, the value of the DC power detected using the first detection circuit is equal to or less than a threshold value. Determine whether or not
When the value of the DC power is equal to or less than the threshold value, the switching circuit determines that the AC power of a predetermined value or more is not required for driving the load, and connects the load and the battery. And transmitting a power transmission stop signal for stopping transmission of the AC power from the power transmission device to the power reception device to the power transmission device,
When the storage device has a storage amount greater than or equal to a predetermined amount, the load is driven by the DC power charged in the storage device.

  According to the above aspect, the control circuit is first detected using the first detection circuit in a state where the load and the battery are disconnected and the DC power is supplied from the rectifier circuit to the load. It is then determined whether or not the value of the DC power is below a threshold value. Then, when the value of the DC power is equal to or less than the threshold value, it is determined that the AC power of a predetermined value or more is not required for driving the load, and the load is connected to the capacitor. A switching circuit is controlled, and a power transmission stop signal for stopping transmission of the AC power from the power transmission device to the power reception device is transmitted to the power transmission device. Then, when the storage battery has a storage amount greater than or equal to a predetermined amount, the load is driven by the DC power charged in the storage battery.

  That is, when the low power state is entered, the control circuit connects the load and the battery and transmits a power transmission stop signal to the power transmission device. In response to the power transmission stop signal, the power transmission control circuit in the power transmission device stops power transmission using the inverter circuit. Then, when the amount of electricity stored in the battery is greater than or equal to a predetermined value, electric power is supplied from the battery to the load. Thereby, it is possible to avoid power feeding by wireless power transmission in a low power state with low efficiency, and when the amount of stored power is sufficient, power can be supplied from the capacitor to the load.

A wireless power transmission system according to still another aspect of the present disclosure is provided.
A power receiving device that receives the AC power from a power transmission device including a power transmission antenna that wirelessly transmits AC power,
A power receiving antenna for receiving the AC power;
A rectifier circuit for converting the AC power into DC power;
A first detection circuit for detecting a value of the DC power;
A load driven by the DC power;
A battery for storing the DC power;
A second detection circuit for detecting a storage amount of the capacitor;
A switching circuit that switches connection / disconnection between the load and the capacitor;
A control circuit for controlling the power receiving device,
The control circuit includes:
First, in a state where the load and the capacitor are disconnected and the DC power is supplied from the rectifier circuit to the load, the value of the DC power detected using the first detection circuit is equal to or less than a threshold value. Determine whether or not
When the value of the DC power is equal to or less than the threshold, it is determined that the AC power of a predetermined amount or more is not required for driving the load, and further, when the power storage device has a predetermined amount of storage or more, Controlling the switching circuit to connect the load and the battery, and transmitting a power transmission stop signal to the power transmission device to stop transmission of the AC power from the power transmission device to the power reception device,
Driving the load with the DC power charged in the capacitor;
Power receiving device.

  According to the above aspect, the control circuit is first detected using the first detection circuit in a state where the load and the battery are disconnected and the DC power is supplied from the rectifier circuit to the load. It is then determined whether or not the value of the DC power is below a threshold value. When the value of the DC power becomes equal to or less than the threshold value, the control circuit determines that the predetermined amount or more of the AC power is not required for driving the load, and further stores a predetermined amount or more of power in the capacitor. When there is an amount, the switching circuit is controlled to connect the load and the battery, and a power transmission stop signal for stopping transmission of the AC power from the power transmission device to the power reception device is transmitted to the power transmission device. . Thereby, the load is driven by the DC power charged in the capacitor.

  That is, when the battery is in a low power state and the storage amount of the capacitor is sufficiently high, the load and the capacitor are connected, a power transmission stop signal is transmitted to the power transmission device, and power supply from the capacitor to the load is started. As a result, wireless power transmission at low power with low efficiency is avoided, and power supply from the capacitor with relatively high efficiency to the load is started.

  As described above, the wireless power transmission system according to one aspect of the present disclosure connects a capacitor as a storage load to a power receiving circuit when the size of a driven load decreases below a predetermined value, and performs charging in parallel. Do. If the total load consisting of the drive load and the storage load drops to a certain value due to charging of the capacitor, stop power transmission or disconnect all or part of the load from the rectifier circuit and load from the capacitor. To supply power.

  As a result, in a load state where the transmission efficiency of wireless power transmission is low, the load is driven by the capacitor, and power transmission by wireless power transmission is performed only in a load state where the efficiency is high or higher. As a result, it is possible to increase the power efficiency per hour.

  Hereinafter, more specific embodiments of the present disclosure will be described. However, more detailed explanation than necessary may be omitted. For example, detailed descriptions of already well-known matters and repeated descriptions for substantially the same configuration may be omitted. This is to avoid the following description from becoming unnecessarily redundant and to facilitate understanding by those skilled in the art. In addition, the inventors provide the accompanying drawings and the following description in order for those skilled in the art to fully understand the present disclosure, and these are intended to limit the subject matter described in the claims. is not. In the following description, the same or similar components are denoted by the same reference numerals.

  In this specification, for the sake of easy understanding, expressions such as “power transmission side˜” are used for terms related to the power transmission device, and “power reception side˜” is used for terms related to the power reception device. Terms such as “power transmission side” and “power reception side” may be omitted for brevity.

(Embodiment 1)
FIG. 3 is a block diagram illustrating a configuration of the wireless power transmission system according to the first embodiment of the present disclosure. The wireless power transmission system of this embodiment includes a power transmission device 100 and a power reception device 200. FIG. 3 also shows a power supply 50 that is an external element of the wireless power transmission system. The power supply 50 may be included in the wireless power transmission system.

  The power transmission device 100 includes a power transmission circuit 120 that converts the first direct current (DC) power supplied from the power supply 50 into alternating current (AC) power, and a power transmission antenna 110 that wirelessly transmits the AC power supplied from the power transmission circuit 120. And a power transmission side receiver (communication circuit) 180 that performs communication with the power receiving apparatus 200. The power transmission circuit 120 includes an inverter circuit 130, a pulse generation circuit 160, and a power transmission control circuit 150. The pulse generation circuit 160 outputs a pulse signal that controls the conduction / non-conduction state of the plurality of switching elements in the inverter circuit 130. The power transmission control circuit 150 controls the level of the voltage output from the inverter circuit 130 by determining the output timing of the pulse signal output from the pulse generation circuit 160.

  The power receiving device 200 includes a power receiving antenna 210 that receives AC power transmitted from the power transmitting device 100, a power receiving circuit 220, a power storage device (power storage device) 310, a load 320, and a power receiving side transmitter (communication circuit) 280. Prepare.

  The power receiving circuit 220 includes a rectifier circuit 230 that converts AC power received by the power receiving antenna 210 into second DC power, and a power detection circuit that detects the value of the second DC power output from the rectifier circuit 230 (first 1 detection circuit) 260, a storage voltage detection circuit (second detection circuit) 270 that detects a storage amount by detecting the voltage of the storage device 310, and the rectification circuit 230, the load 320, and the storage device 310 are connected / not connected to each other. A switching circuit 240 that switches connection and a power reception control circuit 250 that controls the entire operation of the power receiving apparatus 200 are included.

  The power receiving device 200 may be a device that operates with electric power, such as an electric vehicle, an automatic guided vehicle (AGV), a robot arm device, or a surveillance camera. The battery 310 is a power storage device such as a battery (secondary battery) or a capacitor that stores the DC power output from the rectifier circuit 230. When a secondary battery is used as the battery 310, for example, an arbitrary secondary battery such as a lithium ion battery, a nickel hydride battery, or a lead battery can be used. When a capacitor is used as the battery 310, an arbitrary capacitor such as an electric double layer capacitor or a lithium ion capacitor can be used. The load 320 is a device such as a motor that is driven by DC power output from the rectifier circuit 230. The load 320 may be, for example, a device including a motor such as an actuator mounted on a joint part of a robot arm. The load 410 may be a camera or an illuminating device having an image sensor such as a CCD mounted on the rotating part of the surveillance camera.

  Each of the power transmitting antenna 110 and the power receiving antenna 210 can be realized by a resonant circuit including a coil and a capacitor, for example. FIG. 4 shows an example of an equivalent circuit of the power transmitting antenna 110 and the power receiving antenna 210 having a configuration of a series resonant circuit. Not only the example illustrated, but each antenna may have a parallel resonant circuit configuration. In this specification, a coil in the power transmission antenna 110 is referred to as a “power transmission coil”, and a coil in the power reception antenna 210 is referred to as a “power reception coil”. Electric power is transmitted wirelessly by inductive coupling (that is, magnetic field coupling) between the power transmission coil and the power reception coil. Each antenna may be configured to transmit power wirelessly using electric field coupling instead of magnetic field coupling. In that case, each antenna may comprise two electrodes for power transmission or reception, and a resonant circuit including an inductor and a capacitor. A power transmission antenna and a power reception antenna using electric field coupling can be suitably used when power is wirelessly transmitted to a moving device such as a transport robot in a factory.

  The power transmission control circuit 150 and the power reception control circuit 250 may be integrated circuits including a processor and a memory, such as a microcontroller (microcomputer). The memory can store a control program (software) and various tables for realizing operations described later. The function described later is realized by the processor executing the control program. The power transmission control circuit 150 and the power reception control circuit 250 may be realized only by hardware, not by software.

  The pulse generation circuit 160 in the power transmission circuit 120 is a gate driver, for example, and drives the inverter circuit 130 based on a control signal from the power transmission control circuit 150 to generate desired AC power.

  FIG. 5A is a diagram illustrating a configuration example of the inverter circuit 130. Inverter circuit 130 has a plurality of switching elements S <b> 1 to S <b> 4 that switch between a conductive state and a non-conductive state in accordance with a pulse signal supplied from pulse generation circuit 160. By changing the conduction and non-conduction states of each switching element, the input DC power can be converted into AC power. In the example shown in FIG. 5A, a full bridge type inverter circuit including four switching elements S1 to S4 is used. In this example, each switching element is an IGBT (Insulated-gate bipolar transistor), but other types of switching elements such as a MOSFET (Metal Oxide Semiconductor Field-Effect Transistor) may be used.

  In the example shown in FIG. 5A, among the four switching elements S1 to S4, the switching elements S1 and S4 (first switching element pair) output a voltage having the same polarity as the supplied DC voltage when conducting. On the other hand, switching elements S2 and S3 (second switching element pair) output a voltage having a polarity opposite to the supplied DC voltage when conducting. The pulse generation circuit 160 supplies a pulse signal to the gates of the four switching elements S1 to S4 in accordance with an instruction from the power transmission control circuit 150. At this time, by adjusting the phase difference between the two pulse signals supplied to the first switching element pair (S1 and S4) and the phase difference between the two pulse signals supplied to the second switching element pair (S2 and S3). The time average value of the amplitude of the output voltage can be controlled.

  FIG. 5B is a diagram illustrating another configuration example of the inverter circuit 130. The inverter circuit 130 in this example is a half-bridge type inverter circuit. When a half-bridge type inverter circuit is used, the above-described phase control cannot be applied. In this case, the time average value of the voltage amplitude can be controlled by controlling the duty ratio of the pulse signal input to each switching element.

  The inverter circuit 130 illustrated in FIG. 5B is a half-bridge type inverter circuit including two switching elements S1 and S2 and two capacitors. The two switching elements S1 and S2 and the two capacitors C1 and C2 are connected in parallel. One end of the power transmission antenna 110 is connected to a point between the two switching elements S1 and S2, and the other end is connected to a point between the two capacitors C1 and C2.

  The power transmission control circuit 150 and the pulse generation circuit 160 supply a pulse signal to each switching element so that the switching elements S1 and S2 are alternately turned on. Thereby, direct-current power is converted into alternating current power.

  In this example, the output time ratio of the output voltage V can be adjusted by adjusting the duty ratio of the pulse signal (that is, the ratio of the period during which the pulse signal is turned on in one cycle). Thereby, the AC power input to the power transmission antenna 140 can be adjusted. Such duty control can be applied even when the inverter circuit 130 shown in FIG. 5A is used.

  Control of the inverter circuit 130 is not limited to the above example, and may be performed by other methods such as frequency control. The amplitude of the voltage output from the inverter circuit 130 can also be changed by adjusting the frequency.

  The power transmission side receiver 180 receives data (control information) indicating the voltage value of the second DC power transmitted from the power reception side transmitter 280. The power transmission control circuit 150 performs feedback control that suppresses fluctuations in the voltage of the second DC power supplied to the load 320 based on the voltage value information. Thereby, the voltage supplied to the load 320 can be kept constant. Note that such feedback control is not essential and may be implemented as necessary.

  In an example, the power reception control circuit 250 transmits a power transmission stop signal for stopping power transmission from the power transmission apparatus 100 to the power reception apparatus 200 to the power reception side transmitter 280 and a power transmission start signal for starting power transmission. To 180. In that case, the power transmission control circuit 150 starts power transmission by the inverter circuit 130 in response to the power transmission start signal, and stops power transmission by the inverter circuit 130 in response to the power transmission stop signal.

  The communication method between the power transmission side receiver 180 and the power reception side transmitter 280 is not limited to a specific method, and may be any method. For example, a wireless communication method such as an amplitude modulation method, a frequency modulation method, a wireless LAN, or Zigbee (registered trademark) can be used.

  The power reception control circuit 250 controls the switching circuit 240 based on the electric power supplied to the load 320 and the charged amount of the battery 310 based on the detection results of the power detection circuit 260 and the stored voltage detection circuit 270. The switching circuit 240 is connected / disconnected between the rectifier circuit 230 and the capacitor 310, connected / disconnected between the rectifier circuit 230 and the load 320, and connected between the capacitor 310 and the load 320 in accordance with an instruction from the power reception control circuit 250. / Switch the disconnected state. In this embodiment, when power is low, power supply to the load 320 by wireless power transmission is suppressed, and power supply from the battery 310 to the load 320 is prioritized. Thereby, the fall of the efficiency of the electric power transmission at the time of low electric power can be suppressed.

  The configuration of the switching circuit 240 and the control method by the power reception control circuit 250 are various. Hereinafter, some examples of the configuration and control method of the switching circuit 240 will be described.

  FIG. 6A is a diagram illustrating a first configuration example of the switching circuit 240. The switching circuit 240 in this example is disposed between the power receiving switch circuit 240b disposed between the rectifier circuit 230 and the load 320, between the power receiving switch circuit 240b and the capacitor 310, and between the capacitor 310 and the load 320. A storage switch circuit 240a. The power receiving switch circuit 240b is controlled when switching the connection / disconnection state between the rectification circuit 230 and the load 320 and the connection / disconnection state between the rectification circuit 230 and the battery 310. The storage switch circuit 240a is controlled when switching the connection / disconnection state between the rectifier circuit 230 and the storage device 310 and the connection / disconnection state between the storage device 310 and the load 320.

  Each of the storage switch circuit 240a and the power reception switch circuit 240b may be a semiconductor switch such as a transistor. Each switch circuit is not limited to a semiconductor switch, and may be a circuit including an arbitrary switching element. The storage switch circuit 240 a and the power reception switch circuit 240 b are controlled to be in a conductive (connected) / non-conductive (disconnected) state by the power reception control circuit 250. In the following description, the conductive (connected) state may be referred to as “ON”, and the non-conductive (disconnected) state may be referred to as “OFF”.

  FIG. 6B is a diagram illustrating a second configuration example of the switching circuit 240. The switching circuit 240 in this example includes a storage switch circuit 240 a disposed between the rectifier circuit 230 and the storage battery 310 and between the storage battery 310 and the load 320. The storage switch circuit 240a is controlled when switching the connection / disconnection state between the rectification circuit 230 and the storage device 310 and the connection / disconnection state between the storage device 310 and the load 320. In this example, switching of the connection / disconnection state between the rectifier circuit 230 and the load 320 is performed when the power reception control circuit 250 sends a power transmission stop signal and a power transmission start signal to the power transmission apparatus 100 via the power reception side transmitter 280. Done by sending. In this example, when power supply from the rectifier circuit 230 to the load 320 is stopped, power supply (charging) from the rectifier circuit 230 to the battery 310 is also stopped.

  FIG. 6C is a diagram illustrating a third configuration example of the switching circuit 240. The switching circuit 240 in this example includes a storage switch circuit 240a, a power reception switch circuit 240b, and a load switch circuit 240c. The storage switch circuit 240a and the power reception switch circuit 240b are disposed at the same positions as in the example of FIG. 6A. The load switch circuit 240c is provided between the power receiving switch circuit 240b and the load 320 and between the storage switch circuit 240a and the load 320. The load switch circuit 240c may also be a semiconductor switch such as a transistor. In this example, the power reception control circuit 250 controls the path through which the second DC power is supplied by switching the connection / disconnection state of the three switch circuits 240a, 240b, and 240c. The load switch circuit 240c is turned off only in a state where the load 320 is completely off (for example, a state where no power supply is required, such as before the load 320 is activated).

  FIG. 6D is a diagram illustrating a fourth configuration example of the switching circuit 240. The switching circuit 240 in this example includes a storage switch circuit 240a and a load switch circuit 240c. The storage switch circuit 240a and the load switch circuit 240c are disposed at the same positions as in the example of FIG. 6C. In this example, the power reception control circuit 250 controls the path through which the second DC power is supplied by switching the connection / disconnection state of the two switch circuits 240a and 240c. The load switch circuit 240c is turned off only when the load 320 is completely turned off.

  The configuration of the switching circuit 240 is not limited to the illustrated configuration, and various configurations are possible. For example, the rectifier circuit 230 and the load 320 may be connected, the rectifier circuit 230 and the capacitor 310 may be connected, and the load 320 and the capacitor 310 may be disconnected. Further, various switching controls may be possible by combining the configuration of the switching circuit 240 shown in FIGS. 6A to 6D.

  Next, several patterns of the connection / disconnection states of the rectifier circuit 230, the capacitor 310, and the load 320 will be described.

  FIG. 7A shows a state where the rectifier circuit 230 and the load 320 are connected, the rectifier circuit 230 and the capacitor 310 are not connected, and the load 320 and the capacitor 310 are not connected. In this state, power is supplied from the rectifier circuit 230 to the load 320, and power supply (charging) from the rectifier circuit 230 to the battery 310 and power supply from the battery 310 to the load 320 are not performed. This state is selected when the load 320 consumes more than a certain value of power.

  FIG. 7B shows a state where the rectifier circuit 230 and the load 320 are connected, the rectifier circuit 230 and the capacitor 310 are connected, and the load 320 and the capacitor 310 are connected. When wireless power transmission is performed in this state, power is supplied from the rectifier circuit 230 to both the load 320 and the battery 310. This state is selected when power of a certain value (power threshold) or more is consumed by power feeding to the load 320 and charging of the battery 310. In this state, driving of the load 320 and charging of the battery 310 can be performed simultaneously. This state can also be selected when wireless power transmission is stopped by the aforementioned power transmission stop signal and power is supplied from the battery 310 to the load 320.

  FIG. 7C shows a state where the rectifier circuit 230 and the load 320 are disconnected, the rectifier circuit 230 and the capacitor 310 are disconnected, and the load 320 and the capacitor 310 are connected. In this state, power is not supplied to the battery 310 and the load 320 by wireless power transmission, and power is supplied from the battery 310 to the load 320. This state is selected when power less than a certain value (power threshold) is consumed by feeding power to the load 320 and charging the battery 310. As the charging of the battery 310 proceeds, the power consumed by the battery 310 decreases. By shifting to a state where power is supplied from the capacitor 310 to the load 320 when fully charged, wireless power transmission in a low load state with low efficiency can be avoided, and the load 320 from the capacitor 310 with relatively high efficiency can be avoided. Power is supplied to

  FIG. 7D shows a state where the rectifier circuit 230 and the load 320 are not connected, the rectifier circuit 230 and the capacitor 310 are connected, and the load 320 and the capacitor 310 are not connected. In this state, power is supplied from the rectifier circuit 230 to the battery 310, and power is not supplied to the load 320. This state is selected when the battery 320 is charged while the load 320 is stopped.

  Next, the operation of the present embodiment will be described in comparison with the operation in the comparative example.

  FIG. 8 is a diagram illustrating a power transmission control sequence in the comparative example. In this example, the power receiving circuit 220 basically drives the load 320 via the battery 310 while charging the battery 310 (for example, a battery). This operation is continued even when the power reception control circuit 250 in the power reception circuit 220 detects a decrease in voltage output from the rectifier circuit 230 (hereinafter also referred to as “power reception voltage”). When the power reception voltage decreases, the power transmission control circuit 150 controls the inverter circuit 130 so that the power reception voltage approaches the specified voltage (feedback control). The power receiving circuit 220 continues the operation of driving the load 320 via the battery 310 while charging the battery 310 even after detecting that the power receiving voltage has returned to the predetermined voltage. When the voltage (charged amount) of the battery 310 decreases, the rectifier circuit 230 in the power receiving circuit 220 directly drives the load 320, and the battery 310 is charged with surplus power. As shown in FIG. 8, when it is detected that the voltage of the battery has further decreased and a decrease in the received voltage is detected, the power reception control circuit 250 charges the battery 310 while supplying power to the load 320. . When the amount of power stored in the battery 310 is recovered, the driving of the load 320 via the battery 310 is performed again.

  In the operation of the comparative example shown in FIG. 8, even when the load 320 is in a low load state, the driving of the load 320 by wireless power transmission is continued. As a result, when power is supplied to a load 320 such as a motor in which a low load state frequently occurs, there is a problem that the efficiency per operation of the entire operation is lowered. Therefore, in the present embodiment, when detecting that the load 320 is in a low load state, the power reception control circuit 250 stops driving the load 320 by wireless power transmission and starts driving the load 320 by the capacitor 310. Thereby, the efficiency in a low load state is improved, and the efficiency per time of the entire operation is improved.

  FIG. 9A is a diagram illustrating an example of a power transmission control sequence in the present embodiment. The power receiving circuit 220 basically drives the load 420 directly from the rectifier circuit 230 and charges the battery 310 with the surplus power. In the example illustrated in FIG. 9A, power is first supplied from the rectifier circuit 230 to the load 420. Power supply to the battery 310 is not performed. When a decrease in power is detected (step S21), the power reception control circuit 250 connects the rectifier circuit 230 and the battery 310, and performs charging of the battery 310 and power supply to the load 320 in parallel. In this state, when it is detected that the voltage of the battery 310 is sufficient (the battery 310 has a charged amount equal to or greater than the first charge threshold) (step S22), the power reception control circuit 250 connects the rectifier circuit 230 and the load 320. The switching circuit 240 is controlled so that the rectifier circuit 230 and the battery 310 are disconnected and the load 320 and the battery 310 are connected. Thereby, the load 320 is driven by the DC power charged in the battery 310.

  When the power reception control circuit 250 detects that the storage amount (or voltage) of the battery 310 is reduced and the storage amount is less than the first storage threshold (step S23), the power reception control circuit 250 connects the rectifier circuit 230 and the load 320, The switching circuit 240 is controlled so that the rectifier circuit 230 and the battery 310 are connected and the load 320 and the battery 310 are disconnected. Thereby, power transmission is started again (step S24), and DC power from the rectifier circuit 230 is supplied to the load 320 and the battery 310.

  FIG. 9B is a diagram illustrating another example of the power transmission control sequence in the present embodiment. In this example, the power receiving circuit 220 basically drives the load 420 directly from the rectifier circuit 230 and charges the battery 310 with the surplus power. Initially, power is supplied from the rectifier circuit 230 to the load 420, but power is not supplied to the battery 310. When a decrease in power is detected (step S31), the power reception control circuit 250 connects the rectifier circuit 230 and the battery 310, and performs charging of the battery 310 and power supply to the load 320 in parallel. When a decrease in power is detected as the battery 310 is charged (step S <b> 32), the power reception control circuit 250 transmits a power transmission stop signal to the power transmission device 100 via the power reception side transmitter 280. In response to the power transmission stop signal, the power transmission control circuit 150 in the power transmission device 100 stops the operation of the inverter circuit 130 (step S33). That is, the power reception control circuit 250 stops power transmission from the rectifier circuit 230 when the entire load including the battery 310 is equal to or lower than the specified value (that is, when the power value is equal to or lower than the power threshold). Switching to driving of the load 320 by the capacitor 310 is performed.

  Thereafter, when the amount of power stored in the battery 310 is equal to or less than a predetermined threshold (step S34), the power reception control circuit 250 transmits a power transmission start signal to the power transmission device 100. Thereby, the load 320 is directly driven again from the rectifier circuit 230, and the battery 310 is charged with the surplus power.

  Thereafter, when the amount of electricity stored in the battery 310 is recovered and the load 320 becomes equal to or less than the specified value, power transmission is stopped again, and the load 320 is driven via the battery 310.

  With the power transmission control in the present embodiment, the efficiency per time when the transmitted power is low can be increased.

  FIG. 10 is a diagram illustrating an example of power-efficiency characteristics in the present embodiment. A solid line indicates the efficiency of power transmission from the rectifier circuit 230. The broken line indicates the efficiency of power transmission from the battery 310. As shown in the figure, the efficiency of power transmission from the rectifier circuit 230 rapidly decreases as the power decreases. On the other hand, the efficiency of power transmission from the battery 310 is substantially constant when the power is low, and is relatively high. Therefore, the power threshold when the power supply from the rectifier circuit 230 to the load 320 is stopped and the power supply from the capacitor 310 to the load 320 is started is, for example, that the efficiency of power transmission from the capacitor 310 is It can be set to a power value that exceeds the efficiency of power transmission. By setting the power threshold in this way, the power supply with higher efficiency is selected from among the power supply from the rectifier circuit 230 and the power supply from the battery 310, so that the efficiency per hour can be improved as compared with the conventional case. it can.

  As described with reference to FIG. 2B, when the load 320 is driven at a constant rotational speed such as a motor for a long time, a light load state frequently occurs during operation. In order to improve the efficiency in the light load state which occurs frequently, in this embodiment, the power supply from the capacitor 310 is given priority over the power supply from the rectifier circuit 230 in the light load state (low power state).

  FIG. 11 is a diagram illustrating an example of the relationship between the time change of the power supplied from the power receiving circuit 220 and the voltage (or the amount of stored electricity) of the battery 310, and the power supply state and the state of the storage switch at each timing. “Power transmission” in the power supply state means a state in which power is supplied from the rectifier circuit 230 to the load 320 or the capacitor 310, and “power transmission stopped” means that power is not supplied from the rectifier circuit 230 to the load 320 or the capacitor 310. Means state. The power supply state may be switched by, for example, the power receiving switch circuit 240b or the load switch circuit 240c illustrated in FIGS. 6A, 6C, and 6D, or may be switched by transmitting a power transmission stop signal and a power transmission start signal to the power transmission device 100. . “ON” and “OFF” in the storage switch state represent the conductive and non-conductive states of the storage switch circuit 240a shown in FIGS. 6A to 6D, respectively.

  The power supplied from the power receiving circuit 220 is the sum of the power supplied to the load 320 and the battery 310. If the power is below a specified value (power threshold Wth), power supply (power transmission) by wireless power transmission is stopped. This avoids inefficient power supply in low load situations.

  While power transmission by wireless power transmission is stopped, the load 320 is driven by the capacitor 310. By monitoring the voltage or the amount of electricity stored, a decrease in the capacity of the battery 310 can be detected. When the voltage of the battery 310 decreases and becomes equal to or lower than a predetermined threshold (second voltage threshold Vth2), power transmission by wireless power transmission is resumed, and the battery 310 is charged (high load state). As described above, it is equivalent that the voltage of the battery 310 is equal to or less than a predetermined threshold (voltage threshold) and the amount of charge is equal to or less than a predetermined threshold (power storage threshold).

  Next, a specific example of the operation of the embodiment will be described.

  FIG. 12 is a flowchart illustrating an example of a power path switching operation during load driving executed by the power reception control circuit 250. Here, as shown in FIG. 6A, an example in which the switching circuit 240 includes a storage switch circuit 240a and a power reception switch circuit 240b will be described. The power reception control circuit 250 first turns on the power reception switch circuit 240b (connected state) (step S101). As a result, power is supplied from the rectifier circuit 230 to the load 320. The power reception control circuit 250 acquires the second DC power Wl by the power detection circuit 260 (step S102). Then, it is determined whether the second DC power Wl is larger than the power threshold Wth (step S103). When Wl> Wth, the power reception control circuit 250 acquires the voltage Vb of the battery 310 using the storage voltage detection circuit 270 (step S104). Then, it is determined whether or not the voltage Vb of the battery 310 is larger than the first voltage threshold Vth1 (step S105). The first power storage threshold value Vth1 can be set to a value close to the voltage value when the battery 310 is fully charged, for example. Assuming that the voltage at the time of full charge is Vmax, Vth1 can be set to a value of, for example, 0 · 97 Vmax or more and 0.99Vmax or less. However, Vth1 is not limited to this range. If Vb ≦ Vth1, it is determined that charging is not yet sufficient, and the process returns to step S101. When Vb> Vth1, the power reception control circuit 250 determines that the battery 310 is close to a fully charged state, switches the storage switch circuit 240a to OFF (disconnected state), and returns to step S102. Thereby, the power supply from the rectifier circuit 230 to the battery 310 is stopped.

  In step S103, when Wl ≦ Wth, the power reception control circuit 250 determines whether or not the power storage switch circuit 240a is ON (step S107). If the storage switch circuit 240a is OFF, the storage switch circuit 240a is turned ON (step S108), and the process returns to step S102. Thereby, charging is started. In step S107, when the storage switch circuit 240a is ON, the power reception control circuit 250 acquires the voltage Vb of the battery 310 using the storage voltage detection circuit 270 (step S109). Then, it is determined whether the voltage Vb is larger than the first voltage threshold value Vth1 (step S110). When Vb ≦ Vth1, it is determined that charging is insufficient, and the process returns to step S109. When Vb> Vth1, the power reception control circuit 250 determines that the battery 310 is almost fully charged, and turns off the power reception switch circuit 240b (step S111). As a result, power supply from the rectifier circuit 230 to the load 320 is stopped, and power is supplied from the battery 310 to the load 320.

  Thereafter, the power reception control circuit 250 acquires the voltage Vb of the battery 310 using the battery voltage detection circuit 270 (step S112). Then, it is determined whether the voltage Vb is smaller than the second voltage threshold Vth2 (step S113). The second voltage threshold value Vth2 is a value smaller than the first voltage threshold value Vth1, and may be set to a value of 0.94 Vth1 or more and 0.97 Vth1 or less (0.92 Vmax or more and 0.96 Vmax or less), for example. However, the value of Vth2 is not limited to this range. If Vb ≧ Vth2, the process returns to step S112. When Vb <Vth2, it is determined that the remaining amount of the battery 310 (battery) has decreased, and the power reception control circuit 250 returns to step S110 and turns on the power reception switch circuit 240b.

  With the above operation, driving of the load 320 by wireless power transmission at low power is avoided, and furthermore, suitable power feeding and charging operations according to the amount of power stored in the battery 310 are realized.

  FIG. 13 is a flowchart illustrating another example of the power path switching operation during load driving executed by the power reception control circuit 250. In this example, as shown in FIG. 6B, the switching circuit 240 has a storage switch circuit 240a. First, the power reception control circuit 250 requests the power transmission circuit 120 of the power transmission device 100 to start power transmission (step S201). Specifically, the power reception control circuit 250 transmits a power transmission start signal to the power transmission device 100 via the power reception side transmitter 280. When the power transmission control circuit 150 in the power transmission device 100 receives the power transmission start signal via the power transmission side receiver 180, the power transmission control circuit 150 drives the inverter circuit 130 to start power transmission. As a result, power is supplied from the rectifier circuit 230 to the load 320. The power reception control circuit 250 acquires the second DC power Wl by the power detection circuit 260 (step S202). And it is judged whether the 2nd DC electric power Wl is larger than the electric power threshold value Wth (step S203). When Wl> Wth, the power reception control circuit 250 acquires the voltage Vb of the battery 310 using the storage voltage detection circuit 270 (step S204). Then, it is determined whether the voltage Vb of the battery 310 is greater than the first voltage threshold Vth1 (step S205). The first voltage threshold value Vth1 is set to a value close to the voltage value when the battery 310 is fully charged. If Vb ≦ Vth1, it is determined that charging is not yet sufficient, and the process returns to step S101. When Vb> Vth1, the power reception control circuit 250 determines that the battery 310 is almost fully charged, switches the power storage switch circuit 240a to OFF, and returns to step S102. As a result, power supply (charging) from the rectifier circuit 230 to the battery 310 is stopped.

  In step S203, when Wl ≦ Wth, the power reception control circuit 250 determines whether the power storage switch circuit 240a is ON (step S207). If the storage switch circuit 240a is OFF, the storage switch circuit 240a is turned ON (step S208), and the process returns to step S202. Thereby, charging is started. In step S207, when the storage switch circuit 240a is ON, the power reception control circuit 250 acquires the voltage Vb of the battery 310 using the storage voltage detection circuit 270 (step S209). Then, it is determined whether the voltage Vb is larger than the first voltage threshold value Vth1 (step S210). When Vb ≦ Vth1, it is determined that charging is insufficient, and the process returns to step S209. When Vb> Vth1, the power reception control circuit 250 determines that the battery 310 is nearly fully charged, and transmits a power transmission stop signal to the power transmission control circuit 150 in the power transmission circuit 120 (step S211). As a result, power supply from the rectifier circuit 230 to the load 320 is stopped, and power is supplied from the battery 310 to the load 320.

  Thereafter, the power reception control circuit 250 acquires the voltage Vb of the battery 310 using the battery voltage detection circuit 270 (step S212). Then, it is determined whether the voltage Vb is smaller than the second voltage threshold Vth2 (step S213). If Vb ≧ Vth2, the process returns to step S212. When Vb <Vth2, it is determined that the remaining amount of the battery 310 (battery) has decreased, and the power reception control circuit 250 returns to step S210 and transmits a power transmission start signal to the power transmission circuit 120.

  With the above operation, driving of the load 320 by wireless power transmission at low power is avoided, and furthermore, suitable power feeding and charging operations according to the amount of power stored in the battery 310 are realized.

  FIG. 14 is a flowchart illustrating an example of a charging process when power supply to the load 420 executed by the power reception control circuit 250 is stopped. In this example, as illustrated in FIG. 6C, the switching circuit 240 includes a power storage switch circuit 240a, a power reception switch circuit 240b, and a load switch circuit 240c. First, the power reception control circuit 250 turns off the load switch circuit 240c, turns on the storage switch circuit 240a, and turns on the power reception switch circuit 240b (steps S301 to S303). As a result, power supply to the load 420 is stopped and only the battery 310 is charged.

  The power reception control circuit 250 acquires the voltage Vb of the battery 310 using the stored voltage detection circuit 270 (step S304). Then, it is determined whether the voltage Vb of the battery 310 is larger than the first voltage threshold Vth1 (step S305). In the case of Vb ≦ Vth1, it is determined that charging is not yet sufficient, and the process returns to step S304. When Vb> Vth1, the power reception control circuit 250 determines that the battery 310 is close to a fully charged state, and switches the power reception switch circuit 240b to OFF (step S306). Thereby, charging is stopped. Thereafter, the power reception control circuit 250 turns on the load switch circuit 240c (step S307). Thereby, power supply from the battery 310 to the load 320 is started. Thereafter, the operation at the time of load driving shown in FIG. 12 or 13 may be executed (step S308). In step S306, the storage switch circuit 240a may be turned off instead of the power receiving switch circuit 240b. In this case, when the load switch circuit 240c is turned on in step S307, power supply from the rectifier circuit 230 to the load 320 is started.

  FIG. 15 is a flowchart illustrating another example of the charging process when power supply to the load 420 executed by the power reception control circuit 250 is stopped. In this example, as illustrated in FIG. 6D, the switching circuit 240 includes a storage switch circuit 240a and a load switch circuit 240c. First, the power reception control circuit 250 turns off the load switch circuit 240c and turns on the storage switch circuit 240a (steps S401 and S402). Then, a power transmission start signal is transmitted to the power transmission circuit 120 (step S403). As a result, power supply to the load 420 is stopped and only the battery 310 is charged.

  The power reception control circuit 250 acquires the voltage Vb of the battery 310 using the battery voltage detection circuit 270 (step S404). Then, it is determined whether or not the voltage Vb of the battery 310 is larger than the first voltage threshold Vth1 (step S405). If Vb ≦ Vth1, it is determined that charging is not yet sufficient, and the process returns to step S404. When Vb> Vth1, the power reception control circuit 250 determines that the battery 310 is close to a fully charged state, and transmits a power transmission stop signal to the power transmission circuit 120 (step S406). Thereby, charging is stopped. Thereafter, the power reception control circuit 250 turns on the load switch circuit 240c (step S407). Thereby, power supply from the battery 310 to the load 320 is started. Thereafter, the operation at the time of load driving shown in FIG. 12 or 13 can be executed (step S408).

  With the above operation, in a low load state where the transmission efficiency of wireless power transmission is low, the load is driven by the capacitor, and power transmission by wireless power transmission is performed only in a load state where the efficiency is high or higher. Thereby, it becomes possible to improve the power efficiency per time. Furthermore, according to the present embodiment, the timing of charging and discharging is appropriately controlled according to the amount of power stored in the battery. For this reason, it is possible to stably supply power to the load while suppressing a decrease in transmission efficiency.

  As described above, the present disclosure includes the wireless power transmission system described in the following items.

[Item 1]
A power receiving device that receives the AC power from a power transmission device including a power transmission antenna that wirelessly transmits AC power,
A power receiving antenna for receiving the AC power;
A rectifier circuit for converting the AC power into DC power;
A detection circuit for detecting a value of the DC power;
A load driven by the DC power;
A battery for storing the DC power;
i) connection / disconnection between the rectifier circuit and the load; and ii) a switching circuit that switches connection / disconnection between the load and the capacitor;
A control circuit for controlling the power receiving device,
The control circuit includes:
First, detection is performed using the detection circuit in a state where the rectifier circuit and the load are connected, the rectifier circuit and the capacitor are disconnected, and the DC power is supplied from the rectifier circuit to the load. Determining whether the value of the direct-current power that has been obtained is equal to or less than a power threshold;
When the value of the DC power is less than or equal to the power threshold, it is determined that the AC power of a predetermined value or more is not required for driving the load, the rectifier circuit and the load are disconnected, and Controlling the switching circuit to connect a load and the capacitor;
Driving the load with the DC power charged in the capacitor;
Power receiving device.

[Item 2]
A power receiving device that receives the AC power from a power transmission device including a power transmission antenna that wirelessly transmits AC power,
A power receiving antenna for receiving the AC power;
A rectifier circuit for converting the AC power into DC power;
A first detection circuit for detecting a value of the DC power;
A load driven by the DC power;
A battery for storing the DC power;
A second detection circuit for detecting a storage amount of the capacitor;
i) connection / disconnection between the rectifier circuit and the load, ii) connection / disconnection between the rectifier circuit and the capacitor, and iii) a switching circuit that switches connection / disconnection between the load and the capacitor. When,
A control circuit for controlling the power receiving device,
The control circuit includes:
First, the rectifier circuit and the load are connected, the rectifier circuit and the capacitor are disconnected, and the load and the capacitor are disconnected, and the DC power is supplied from the rectifier circuit to the load In a state, it is determined whether or not the value of the DC power detected using the first detection circuit is equal to or lower than a power threshold;
When the value of the DC power is equal to or less than the power threshold, it is determined that the AC power of a predetermined level or more is not required for driving the load, the rectifier circuit and the load are connected, and the rectification Connecting the circuit and the capacitor, and controlling the switching circuit to connect the load and the capacitor;
When the storage device has a storage amount equal to or greater than a first storage threshold, the rectifier circuit and the load are disconnected, the rectifier circuit and the capacitor are disconnected, and the load and the capacitor are connected Controlling the switching circuit to a state, and driving the load with the DC power charged in the capacitor;
Power receiving device.

[Item 3]
The control circuit disconnects the rectifier circuit and the load, connects the rectifier circuit and the capacitor, and does not connect the load and the load when the capacitor does not have a storage amount equal to or greater than the first storage threshold value. Controlling the switching circuit in a state of disconnecting the capacitor, and charging the capacitor with the DC power from the rectifier circuit,
Item 2. The power receiving device according to item 2.

[Item 4]
The control circuit controls the switching circuit to connect the rectifier circuit and the load, and to connect the rectifier circuit and the capacitor when the capacitor does not have a storage amount equal to or greater than the first storage threshold value. , Charging the accumulator with the DC power from the rectifier circuit,
Item 2. The power receiving device according to item 2.

[Item 5]
The control circuit connects the rectifier circuit and the load when the storage amount of the capacitor is equal to or lower than a second storage threshold after the supply of the DC power from the capacitor to the load is started, Connecting the rectifier circuit and the battery, supplying the DC power from the rectifier circuit to the load, and charging the battery with the DC power from the rectifier circuit;
Item 2. The power receiving device according to item 2.

[Item 6]
The second power storage threshold is a value equal to or less than the first power storage threshold.
Item 5. The power receiving device according to item 5.

[Item 7]
A power receiving device that receives the AC power from a power transmission device including a power transmission antenna that wirelessly transmits AC power,
A power receiving antenna for receiving the AC power;
A rectifier circuit for converting the AC power into DC power;
A detection circuit for detecting a value of the DC power;
A load driven by the DC power;
A battery for storing the DC power;
A switching circuit that switches connection / disconnection between the load and the capacitor;
A control circuit for controlling the power receiving device,
The control circuit includes:
First, whether or not the value of the DC power detected using the detection circuit is equal to or less than a threshold value in a state where the load and the battery are disconnected and the DC power is supplied from the rectifier circuit to the load Determine whether
When the value of the DC power is equal to or less than the threshold value, the switching circuit determines that the AC power of a predetermined value or more is not required for driving the load, and connects the load and the battery. And transmitting a power transmission stop signal for stopping transmission of the AC power from the power transmission device to the power reception device to the power transmission device,
Driving the load with the DC power charged in the capacitor;
Power receiving device.

[Item 8]
A power receiving device that receives the AC power from a power transmission device including a power transmission antenna that wirelessly transmits AC power,
A power receiving antenna for receiving the AC power;
A rectifier circuit for converting the AC power into DC power;
A first detection circuit for detecting a value of the DC power;
A load driven by the DC power;
A battery for storing the DC power;
A second detection circuit for detecting a storage amount of the capacitor;
A switching circuit that switches connection / disconnection between the load and the capacitor;
A control circuit for controlling the power receiving device,
The control circuit includes:
First, in a state where the load and the capacitor are disconnected and the DC power is supplied from the rectifier circuit to the load, the value of the DC power detected using the first detection circuit is equal to or less than a threshold value. Determine whether or not
When the value of the DC power is equal to or less than the threshold value, the switching circuit determines that the AC power of a predetermined value or more is not required for driving the load, and connects the load and the battery. And transmitting to the power transmission device a power transmission stop signal for stopping transmission of the AC power from the power transmission device to the power receiving device,
When the storage battery has a storage amount greater than or equal to a predetermined amount, the load is driven by the DC power charged in the storage battery.
Power receiving device.

[Item 9]
A power receiving device that receives the AC power from a power transmission device including a power transmission antenna that wirelessly transmits AC power,
A power receiving antenna for receiving the AC power;
A rectifier circuit for converting the AC power into DC power;
A first detection circuit for detecting a value of the DC power;
A load driven by the DC power;
A battery for storing the DC power;
A second detection circuit for detecting a storage amount of the capacitor;
A switching circuit that switches connection / disconnection between the load and the capacitor;
A control circuit for controlling the power receiving device,
The control circuit includes:
First, in a state where the load and the capacitor are disconnected and the DC power is supplied from the rectifier circuit to the load, the value of the DC power detected using the first detection circuit is equal to or less than a threshold value. Determine whether or not
When the value of the DC power is equal to or less than the threshold, it is determined that the AC power of a predetermined amount or more is not required for driving the load, and further, when the power storage device has a predetermined amount of storage or more, Controlling the switching circuit to connect the load and the battery, and transmitting a power transmission stop signal to the power transmission device to stop transmission of the AC power from the power transmission device to the power reception device,
Driving the load with the DC power charged in the capacitor;
Power receiving device.

[Item 10]
The load includes a motor,
Item 10. The power receiving device according to any one of Items 1 to 9.

[Item 11]
The state where the predetermined amount or more of the AC power is not required for driving the load includes a state in which the change in the rotation speed of the motor is within a predetermined range for a certain period of time.
Item 13. The power receiving device according to Item 10.

[Item 12]
The state where the predetermined amount or more of the AC power is not required for driving the load includes a state in which the rotation stop of the motor is maintained.
Item 13. The power receiving device according to Item 10.

  The technology of the present disclosure can be used for an electronic device that needs to transmit power, such as an electric vehicle, a monitoring camera, and a robot.

DESCRIPTION OF SYMBOLS 50 Power supply 100 Power transmission apparatus 110 Power transmission antenna 120 Power transmission circuit 130 Inverter circuit 150 Power transmission control circuit 160 Pulse generation circuit 180 Power transmission side receiver 200 Power reception apparatus 210 Power reception antenna 210
220 power receiving circuit 230 rectifier circuit 240 switching circuit 250 power receiving control circuit 260 power detection circuit (first detection circuit)
270 Storage voltage detection circuit (second detection circuit)
280 Power-receiving-side transmitter 310 Power storage device (power storage device)
320 load

Claims (10)

A power receiving device that receives the AC power from a power transmission device including a power transmission antenna that wirelessly transmits AC power,
A power receiving antenna for receiving the AC power;
A rectifier circuit for converting the AC power into DC power;
A detection circuit for detecting a value of the DC power;
A load driven by the DC power;
A battery for storing the DC power;
i) connection / disconnection between the rectifier circuit and the load; and ii) a switching circuit that switches connection / disconnection between the load and the capacitor;
A control circuit for controlling the power receiving device,
The control circuit includes:
First, detection is performed using the detection circuit in a state where the rectifier circuit and the load are connected, the rectifier circuit and the capacitor are disconnected, and the DC power is supplied from the rectifier circuit to the load. Determining whether the value of the direct-current power that has been obtained is equal to or less than a power threshold;
When the value of the DC power is less than or equal to the power threshold, it is determined that the AC power of a predetermined value or more is not required for driving the load, the rectifier circuit and the load are disconnected, and Controlling the switching circuit to connect a load and the capacitor;
Driving the load with the DC power charged in the capacitor;
Power receiving device. A power receiving device that receives the AC power from a power transmission device including a power transmission antenna that wirelessly transmits AC power,
A power receiving antenna for receiving the AC power;
A rectifier circuit for converting the AC power into DC power;
A first detection circuit for detecting a value of the DC power;
A load driven by the DC power;
A battery for storing the DC power;
A second detection circuit for detecting a storage amount of the capacitor;
i) Connection / disconnection of the rectifier circuit and the load, ii) Connection / connection of the rectifier circuit and the battery
And iii) a switching circuit that switches connection / disconnection between the load and the capacitor, and
A control circuit for controlling the power receiving device,
The control circuit includes:
First, the rectifier circuit and the load are connected, the rectifier circuit and the capacitor are disconnected, and the load and the capacitor are disconnected, and the DC power is supplied from the rectifier circuit to the load In a state, it is determined whether or not the value of the DC power detected using the first detection circuit is equal to or lower than a power threshold;
When the value of the DC power is equal to or less than the power threshold, it is determined that the AC power of a predetermined level or more is not required for driving the load, the rectifier circuit and the load are connected, and the rectification Connecting the circuit and the capacitor, and controlling the switching circuit to connect the load and the capacitor;
When the storage device has a storage amount equal to or greater than a first storage threshold, the rectifier circuit and the load are disconnected, the rectifier circuit and the capacitor are disconnected, and the load and the capacitor are connected Controlling the switching circuit to a state, and driving the load with the DC power charged in the capacitor;
Power receiving device. The control circuit disconnects the rectifier circuit and the load, connects the rectifier circuit and the capacitor, and does not connect the load and the load when the capacitor does not have a storage amount equal to or greater than the first storage threshold value. Controlling the switching circuit in a state of disconnecting the capacitor, and charging the capacitor with the DC power from the rectifier circuit,
The power receiving device according to claim 2. The control circuit controls the switching circuit to connect the rectifier circuit and the load, and to connect the rectifier circuit and the capacitor when the capacitor does not have a storage amount equal to or greater than the first storage threshold value. , Charging the accumulator with the DC power from the rectifier circuit,
The power receiving device according to claim 2. The control circuit connects the rectifier circuit and the load when the storage amount of the capacitor is equal to or lower than a second storage threshold after the supply of the DC power from the capacitor to the load is started, Connecting the rectifier circuit and the battery, supplying the DC power from the rectifier circuit to the load, and charging the battery with the DC power from the rectifier circuit;
The power receiving device according to claim 2. The second power storage threshold is a value equal to or less than the first power storage threshold.
The power receiving device according to claim 5. A power receiving device that receives the AC power from a power transmission device including a power transmission antenna that wirelessly transmits AC power,
A power receiving antenna for receiving the AC power;
A rectifier circuit for converting the AC power into DC power;
A detection circuit for detecting a value of the DC power;
A load driven by the DC power;
A battery for storing the DC power;
A switching circuit that switches connection / disconnection between the load and the capacitor;
A control circuit for controlling the power receiving device,
The control circuit includes:
First, whether or not the value of the DC power detected using the detection circuit is equal to or less than a threshold value in a state where the load and the battery are disconnected and the DC power is supplied from the rectifier circuit to the load Determine whether
When the value of the DC power is equal to or less than the threshold value, the switching circuit determines that the AC power of a predetermined value or more is not required for driving the load, and connects the load and the battery. And transmitting a power transmission stop signal for stopping transmission of the AC power from the power transmission device to the power reception device to the power transmission device,
Driving the load with the DC power charged in the capacitor;
Power receiving device. A power receiving device that receives the AC power from a power transmission device including a power transmission antenna that wirelessly transmits AC power,
A power receiving antenna for receiving the AC power;
A rectifier circuit for converting the AC power into DC power;
A first detection circuit for detecting a value of the DC power;
A load driven by the DC power;
A battery for storing the DC power;
A second detection circuit for detecting a storage amount of the capacitor;
A switching circuit that switches connection / disconnection between the load and the capacitor;
A control circuit for controlling the power receiving device,
The control circuit includes:
First, in a state where the load and the capacitor are disconnected and the DC power is supplied from the rectifier circuit to the load, the value of the DC power detected using the first detection circuit is equal to or less than a threshold value. Determine whether or not
When the value of the DC power is equal to or less than the threshold value, the switching circuit determines that the AC power of a predetermined value or more is not required for driving the load, and connects the load and the battery. And transmitting a power transmission stop signal for stopping transmission of the AC power from the power transmission device to the power reception device to the power transmission device,
When the storage battery has a storage amount greater than or equal to a predetermined amount, the load is driven by the DC power charged in the storage battery.
Power receiving device. A power receiving device that receives the AC power from a power transmission device including a power transmission antenna that wirelessly transmits AC power,
A power receiving antenna for receiving the AC power;
A rectifier circuit for converting the AC power into DC power;
A first detection circuit for detecting a value of the DC power;
A load driven by the DC power;
A battery for storing the DC power;
A second detection circuit for detecting a storage amount of the capacitor;
A switching circuit that switches connection / disconnection between the load and the capacitor;
A control circuit for controlling the power receiving device,
The control circuit includes:
First, in a state where the load and the capacitor are disconnected and the DC power is supplied from the rectifier circuit to the load, the value of the DC power detected using the first detection circuit is equal to or less than a threshold value. Determine whether or not
When the value of the DC power is equal to or less than the threshold, it is determined that the AC power of a predetermined amount or more is not required for driving the load, and further, when the power storage device has a predetermined amount of storage or more, Controlling the switching circuit to connect the load and the battery, and transmitting a power transmission stop signal to the power transmission device to stop transmission of the AC power from the power transmission device to the power reception device,
Driving the load with the DC power charged in the capacitor;
Power receiving device. The load includes a motor,
The power receiving device according to any one of claims 1 to 9.

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