Non-contact power supply system, power transmission device, and power reception device

Abstract

A non-contact power supply system (1) includes a power transmission device (10) and a power reception device (80) that receives power from the power transmission device in a non-contact manner. This power receiving device is provided with: a secondary-side resonance circuit (81) having a secondary-side capacitor (C2) and a secondary-side coil (L2); a rectifier circuit (83); a transient circuit (82); a load device (83); a protection switch that sets the secondary-side resonant circuit to a non-resonant state by setting the protection switch to a conductive state or a non-conductive state; and a secondary-side control circuit (85) that switches the state of the protection switch between a conductive state and a non-conductive state, the primary-side control circuit changing the impedance of the impedance variable element using a detection value of the primary-side detection circuit that changes by switching the protection switch to the conductive state or the non-conductive state, and the secondary-side control circuit changing the impedance of the impedance variable element using a detection value of the primary-side detection circuit that changes by switching the protection switch to the conductive state or the non-conductive state. A power receiving device is transferred from a power transmission state to a standby state.

Description

Citation of Related Applications

[0001] This application is based on Japanese Patent Application No. 2022-191017 filed on November 30, 2022, the content of which is incorporated herein by reference. Technical Field

[0002] The present disclosure relates to a non-contact power supply device, a power transmission device, and a power reception device. Background Art

[0003] Conventionally, there has been a technology for protecting a load that supplies power received by a power reception device that is powered non-contact from a power transmission device (for example, Patent Document 1). In Patent Document 1, after turning on a transistor included in a rectifier, a relay arranged in a current path from a resonator coil to the rectifier is opened to protect the load. Prior Art Documents Patent Documents

[0004] Patent Document 1: Japanese Patent Publication No. 2022-533250 Summary of the Invention

[0005] Since the power transmission device continues to transmit power even after the power reception device stops receiving power, power loss sometimes occurs in the power transmission device.

[0006] The present disclosure can be implemented in the following manner.

[0007] In a first aspect of the present disclosure, a non-contact power supply system is provided that supplies power from a power transmission device to a power reception device in a non-contact manner. The power transmission device includes: a primary resonance circuit having a primary coil and a primary capacitor; an AC power supply that applies AC power of a predetermined operating frequency to the primary resonance circuit; an impedance variable element that is connected between the primary coil and the AC power supply and is used to switch the state of the power transmission device between a power transmission state and a standby state; a primary control circuit that changes the impedance of the impedance variable element; and a primary detection circuit that is used to detect either the magnitude of the magnetic flux linked to the primary coil or the magnitude of the magnetic flux near the primary coil. The power reception device includes: a secondary resonance circuit having a secondary capacitor and a secondary coil that is magnetically coupled to the primary coil; a rectification circuit that rectifies the AC power output from the secondary resonance circuit; a transient circuit that is connected between the rectification circuit and the secondary resonance circuit; a load device that receives the DC power output from the rectification circuit; a protection switch that sets the secondary resonance circuit to a non-resonant state by being set to either a conducting state or a non-conducting state; and a secondary control circuit that sets the state of the protection switch to either the conducting state or the non-conducting state. The primary control circuit changes the impedance of the impedance variable element using the detection value of the primary detection circuit that changes by setting the protection switch to either the conducting state or the non-conducting state, so that the power reception device transfers from the power transmission state to the standby state.

[0008] According to this aspect, since the power reception device has a protection switch, in the case where the power reception device is in an abnormal state or the like, the protection switch can be used to reduce the current supplied to the load device to protect the load device. In addition, if the magnetic flux near the primary coil becomes small in the power transmission state, the primary control circuit increases the impedance of the primary resonance circuit and transfers to the standby state. Thereby, power consumption that does not contribute to the power supply to the power transmission device can be suppressed.

[0009] In a second aspect of the present invention, there is provided a contactless power supply system that supplies power from a power transmission device to a power reception device in a contactless manner. The power transmission device includes: a primary resonance circuit having a primary coil and a primary capacitor; an AC power supply that applies AC power of a predetermined operating frequency to the primary resonance circuit; an impedance variable element that is connected between the primary coil and the AC power supply and is used to switch the state of the power transmission device between a power transmission state and a standby state; a primary control circuit that changes the impedance of the impedance variable element; and a primary detection circuit that is used to detect either the magnitude of the magnetic flux linked to the primary coil or the magnitude of the magnetic flux near the primary coil. The power reception device includes: a secondary resonance circuit having a secondary capacitor and a secondary coil for magnetic coupling with the primary coil; a rectifier circuit that rectifies the AC power output from the secondary resonance circuit and has a switch in at least one of the lower arm and the upper arm; a transient circuit that is connected between the rectifier circuit and the secondary resonance circuit; a load device that receives the DC power output from the rectifier circuit; a protection switch that sets the secondary resonance circuit to a non-resonant state by being set to either a conducting state or a non-conducting state; a secondary control circuit that sets the state of the protection switch to either the conducting state or the non-conducting state; and a state detection circuit that is used to detect the state of the power transmission device. The secondary control circuit, when receiving a power supply stop signal, performs a first process of setting the switch to the conducting state before setting the protection switch to the conducting state. After the first process, when the state of the power transmission device detected by the state detection circuit is in the power transmission state, the secondary control circuit sets the protection switch to the conducting state. The primary control circuit changes the impedance of the impedance variable element by using at least one of the detection value of the primary detection circuit that changes by setting the switch to the conducting state and the detection value of the primary detection circuit that changes by setting the protection switch to either the conducting state or the non-conducting state, so as to transfer the power reception device from the power transmission state to the standby state.

[0010] According to this method, since the power receiving device includes a protection switch and a rectifying circuit having a switch, in the case where the power receiving device is in an abnormal state or the like, the protection switch or the switch of the rectifying circuit can be used to reduce the current supplied to the load device and protect the load device. Further, if the magnetic flux near the primary coil becomes small in the power transmission state, the primary control circuit increases the impedance of the primary resonance circuit and shifts to the standby state. Thereby, it is possible to suppress power consumption that does not contribute to the power supply to the power transmission device.

[0011] In the third method of the present disclosure, there is provided a power transmission device that supplies power to a power receiving device in a non-contact manner. The power transmission device includes: a primary resonance circuit having a primary coil and a primary capacitor; an AC power supply that applies AC power having a predetermined operating frequency to the primary resonance circuit; an impedance variable element that is connected between the primary coil and the AC power supply and is configured to switch the state of the power transmission device between a power transmission state and a standby state; a primary control circuit that changes the impedance of the impedance variable element; and a primary detection circuit that is configured to detect either the magnitude of the magnetic flux linked with the primary coil or the magnitude of the magnetic flux near the primary coil. The power receiving device includes: a secondary resonance circuit having a secondary capacitor and a secondary coil configured to be magnetically coupled with the primary coil; a rectifying circuit that rectifies the AC power output from the secondary resonance circuit; a transient circuit that is connected between the rectifying circuit and the secondary resonance circuit; a load device that receives the DC power output from the rectifying circuit; a protection switch that sets the secondary resonance circuit to a non-resonant state by being set to either a conducting state or a non-conducting state; and a secondary control circuit that sets the state of the protection switch to either the conducting state or the non-conducting state. The primary control circuit changes the impedance of the impedance variable element using the detection value of the primary detection circuit that changes by setting the protection switch to either the conducting state or the non-conducting state, thereby causing the power receiving device to shift from the power transmission state to the standby state.

[0012] According to this method, since the power receiving device has a protection switch, in the case where the power receiving device is in an abnormal state or the like, by using the protection switch, it is possible to reduce the current supplied to the load device and protect the load device. Further, if the magnetic flux near the primary coil becomes small in the power transmission state, the primary control circuit increases the impedance of the primary resonance circuit and shifts to the standby state. Thereby, it is possible to suppress power consumption that does not contribute to the power supply to the power transmission device.

[0013] In a fourth embodiment of the present disclosure, there is provided a power receiving device that receives power from a power transmitting device in a non-contact manner. The power transmitting device includes: a primary resonance circuit having a primary coil and a primary capacitor; an AC power supply that applies AC power at a predetermined operating frequency to the primary resonance circuit; an impedance variable element connected between the primary coil and the AC power supply and configured to switch the state of the power transmitting device between a power transmission state and a standby state; a primary control circuit that changes the impedance of the impedance variable element; and a primary detection circuit that detects either the magnitude of the magnetic flux linked to the primary coil or the magnitude of the magnetic flux near the primary coil. The power receiving device includes: a secondary resonance circuit having a secondary capacitor and a secondary coil configured to magnetically couple with the primary coil; a rectifier circuit that rectifies the AC power output from the secondary resonance circuit; a transient circuit connected between the rectifier circuit and the secondary resonance circuit; a load device that receives the DC power output from the rectifier circuit; a protection switch that sets the secondary resonance circuit to a non-resonant state by being set to either a conductive state or a non-conductive state; and a secondary control circuit that sets the state of the protection switch to either the conductive state or the non-conductive state. The primary control circuit changes the impedance of the impedance variable element using the detection value of the primary detection circuit that changes by setting the protection switch to either the conductive state or the non-conductive state, thereby transferring the power receiving device from the power transmission state to the standby state.

[0014] According to this embodiment, since the power receiving device has a protection switch, in the case where the power receiving device is in an abnormal state or the like, the protection switch can be used to reduce the current supplied to the load device to protect the load device. Further, if the magnetic flux near the primary coil becomes small in the power transmission state, the primary control circuit increases the impedance of the primary resonance circuit and transfers to the standby state. Thereby, power consumption that does not contribute to the power supply to the power transmitting device can be suppressed. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The above objects, other objects, features, and advantages of the present disclosure can be made more apparent by referring to the accompanying drawings and the following detailed description. The drawings are as follows. Figure 1 is a schematic configuration diagram of a non-contact power supply system. Figure 2 is a circuit diagram of the non-contact power supply system of the first embodiment. Figure 3 It is a diagram illustrating the power supply sequence of the first embodiment. Figure 4 It is a circuit diagram of the non-contact power supply system of the second embodiment. Figure 5 It is a diagram illustrating the power supply sequence of the second embodiment. Figure 6 It is a circuit diagram of the non-contact power supply system of the third embodiment. Figure 7 It is a diagram illustrating the power supply sequence of the third embodiment. Figure 8 It is a circuit diagram of the non-contact power supply system of the fourth embodiment. Figure 9 It is a circuit diagram of the non-contact power supply system of the fifth embodiment. Figure 10 It is a diagram illustrating the power supply sequence of the fifth embodiment. Detailed Embodiments

[0016] A. First Embodiment: A1. Structure of the Non-Contact Power Supply System: As Figure 1 shown, the non-contact power supply system 1 includes a power transmission device 10 and a power reception device 80. In this embodiment, the power transmission device 10 is buried under the road RS. The power reception device 80 is installed on a vehicle VE which is a moving body traveling on the road RS. During the travel of the vehicle VE, the power reception device 80 receives power supply from the power transmission device 10. Here, the travel includes the case where the vehicle VE moves and the case where the vehicle stops due to waiting for a signal or the like. The vehicle VE is configured as an electric vehicle or a hybrid vehicle, for example.

[0017] The power transmission device 10 includes a primary resonance circuit 12 having a primary side coil L1 and an AC power supply 11 that supplies power to the primary resonance circuit 12. The AC power supply 11 supplies power to a plurality of primary resonance circuits 12. The plurality of primary side coils L1 are arranged along the extending direction of the road RS.

[0018] In addition, the moving body equipped with the power reception device 80 is not limited to the vehicle VE traveling on the road RS. For example, it can also be an AGV (Automated Guided Vehicle), a traveling robot, etc. Furthermore, the power transmission device 10 can also be provided on a sidewalk or a parking lot adjacent to the road RS, or in the path where the AGV travels, instead of being provided under the road RS.

[0019] The power receiving device 80 includes: a battery 84 as a load device, an auxiliary battery 94, a rectifier circuit 83, a secondary resonance circuit 81 having a secondary coil L2 for magnetically coupling with the primary coil L1, a DC / DC converter 92, an inverter 91, an electric generator 93, an auxiliary 95, and a power receiving side control unit 96. In the present embodiment, the secondary coil L2 is disposed at a position opposite to the primary coil L1, that is, on the lower surface of the vehicle VE.

[0020] The rectifier circuit 83 is connected to the secondary resonance circuit 81. In the power receiving state, the rectifier circuit 83 rectifies the AC power received by the secondary resonance circuit 81, and supplies the rectified DC power to the battery 84, the DC / DC converter 92, and the inverter 91.

[0021] The battery 84 is a secondary battery charged by the supplied DC power. The inverter 91 uses the supplied DC power to drive the electric generator 93. The electric generator 93 operates as a three-phase AC motor and generates a driving force for traveling. In addition, the electric generator 93 operates as a generator when the vehicle VE decelerates, and regenerates power. The regenerated three-phase AC power is converted into DC power by the inverter 91 and used for charging the battery 84.

[0022] The DC / DC converter 92 steps down the DC power supplied from the rectifier circuit 83, and supplies the stepped-down DC power to the auxiliary battery 94 and the auxiliary 95. The auxiliary 95 includes peripheral devices such as an air conditioner device, an electric power steering device, headlights, direction indicators, wipers, etc. of the vehicle VE, and accessories of the vehicle VE. The auxiliary battery 94 is a secondary battery for driving the auxiliary 95.

[0023] The power receiving side control unit 96 controls each part in the power receiving device 80 such as the inverter 91. The power receiving side control unit 96 is implemented by including an ECU (engine control unit). The ECU can be implemented by one microcontroller, or can include multiple microcontrollers. The case of including multiple microcontrollers refers to, for example, a case of including a microcontroller for controlling mechanisms related to the drive of the vehicle VE such as the electric generator 93, and a microcontroller for controlling mechanisms related to the battery 84 such as the rectifier circuit 83.

[0024] A2. Circuit structure of the non-contact power supply system: As Figure 2 shown, in addition to the above structure, the power transmission device 10 further includes a primary capacitor C1 as a variable capacitor, a primary control circuit 13, and a magnetic flux detection circuit 14 as a primary detection circuit. In addition, in Figure 2Only one of the plurality of primary resonant circuits 12 connected to the AC power supply 11 is shown, and the illustration of the other primary resonant circuits 12 is omitted.

[0025] The AC power supply 11 applies AC power of a predetermined operating frequency to the primary resonant circuit 12. In the present embodiment, the operating frequency is 85 kHz. The primary capacitor C1 as an impedance variable element has a function of bringing the primary resonant circuit 12 into a resonant state at the operating frequency and bringing the primary resonant circuit 12 into a non-resonant state at the operating frequency. The primary capacitor C1 is connected between the primary coil L1 and the AC power supply 11. The primary capacitor C1 switches the state of the power transmission device 10 between the standby state and the power transmission state described later.

[0026] In the present embodiment, the primary capacitor C1 is configured to be able to switch to a first capacitance value and a second capacitance value smaller than the first capacitance value. Then, the capacitance value of the primary capacitor C1 is switched to either the first capacitance value or the second capacitance value by the switching signal Sig1 output from the primary control circuit 13. When the primary coil L1 and the secondary coil L2 are magnetically coupled and the primary capacitor C1 has the first capacitance value, the primary resonant circuit 12 becomes a resonant state at the operating frequency. That is, the first capacitance value of the primary capacitor C1 is set to a value at which the resonant frequency of the primary resonant circuit 12 coincides with the operating frequency. In contrast, when the primary capacitor C1 has the second capacitance value, since the resonant frequency of the primary resonant circuit 12 deviates from the operating frequency, the primary resonant circuit 12 becomes a non-resonant state at the operating frequency.

[0027] The primary coil L1 and the primary capacitor C1 are connected in series to form the primary resonant circuit 12. The magnetic flux detection circuit 14 detects the magnitude of the magnetic flux near the primary coil L1. Specifically, the magnetic flux detection circuit 14 has a detection coil Lsp disposed near the secondary coil L2 built therein, and uses the change in the current flowing through the detection coil Lsp to detect the magnitude of the magnetic flux density. The magnetic flux detection circuit 14 outputs a signal representing the detected magnitude of the magnetic flux density to the primary control circuit 13.

[0028] The primary control circuit 13 outputs the switching signal Sig1 to the primary capacitor C1 using the signal output from the magnetic flux detection circuit 14.

[0029] In addition, the primary-side detection circuit is not limited to the flux detection circuit 14 that detects the magnitude of the magnetic flux density, but can also be a sensor capable of detecting the magnitude of the magnetic flux linked to the primary-side coil L1. Specifically, the primary-side detection circuit can also be a current sensor that detects the current flowing through the primary-side coil L1 or a voltage sensor that detects the voltage of the primary-side coil L1. In addition, "detecting the magnitude of the magnetic flux linked to the primary-side coil L1" includes not only the case of detecting all the magnetic flux linked to the primary-side coil L1, but also the case of detecting a part of the magnetic flux linked to the primary-side coil L1 as in the present embodiment.

[0030] In addition to the above structure, the power receiving device 80 further includes secondary-side capacitors C2, C3, a transient circuit 82, a secondary-side control circuit 85, and an abnormality detection circuit 86. A secondary-side capacitor C2 is connected in series at one terminal of the secondary-side coil L2, and a secondary-side capacitor C3 is connected in series at the other terminal of the secondary-side coil L2, thereby forming a secondary-side resonance circuit 81. In addition, as another embodiment of the secondary-side resonance circuit 81, the secondary-side resonance circuit 81 may have either the secondary-side capacitor C2 or the secondary-side capacitor C3.

[0031] The transient circuit 82 is connected between the secondary-side resonance circuit 81 and the rectifier circuit 83. When AC power at the resonance frequency of the transient circuit 82 is input to the transient circuit 82, the transient circuit 82 functions as an impedance transient converter. When AC power at a frequency other than the resonance frequency of the transient circuit 82 is input to the transient circuit 82, the transient circuit 82 functions as a low-pass filter.

[0032] In the present embodiment, the transient circuit 82 includes coils L3 to L6 and a capacitor C4. Coils L3 and L4 are connected in series with the first power supply line N1 connected to one terminal of the secondary-side coil L2. Coils L5 and L6 are connected in series with the second power supply line N2 connected to the other terminal of the secondary-side coil L2. The capacitor C4 is connected to the connection point of coils L3 and L4 and the connection point of coils L5 and L6, and is connected in parallel with the secondary-side coil L2.

[0033] The secondary resonant circuit 81 further includes a protection switch SW1. The protection switch SW1 is connected in parallel with the secondary coil L2. Thus, compared with the case where the protection switch SW1 is connected in series with the secondary coil L2, that is, inserted into the first power supply line N1 or the second power supply line N2, power loss can be reduced, and the current rating of the protection switch SW1 can be decreased. The protection switch SW1 sets the secondary resonant circuit 81 to a non-resonant state by becoming conductive. In the present embodiment, the protection switch SW1 is implemented by two MOSFETs, i.e., a bidirectional switch, to which respective source terminals are connected. Thus, the size of the protection switch SW1 can be reduced.

[0034] The secondary control circuit 85 switches the state of the protection switch SW1 between a conductive state and a non-conductive state. In the present embodiment, the secondary control circuit 85 changes the voltage value of the signal Sig2 input to the gate terminals of the two MOSFETs constituting the protection switch SW1 and switches the state of the protection switch SW1.

[0035] The rectifier circuit 83 is implemented by a diode bridge.

[0036] The abnormality detection circuit 86 detects an abnormal state in the power receiving device 80. Specifically, it has a voltage sensor (not shown) for detecting the voltage of the detection battery 84. When the voltage of the battery 84 is outside a predetermined voltage range, it is determined that an abnormal state exists, and an abnormal signal is output to the secondary control circuit 85.

[0037] When power supply from the secondary resonant circuit 81 to the battery 84 is prohibited, the power receiving side control unit 96 outputs a stop signal to the secondary control circuit 85. For example, when the state of the battery 84 is not a state suitable for charging, the power receiving side control unit 96 outputs a stop signal.

[0038] When the primary coil L1 and the secondary coil L2 are magnetically coupled, the resonant frequency of the primary resonant circuit 12 and the resonant frequency of the secondary resonant circuit 81 are set to be substantially the same. Thus, non-contact power supply to the power receiving device 80 can be performed through magnetic field resonance between the primary coil L1 and the secondary coil L2. As described above, the DC power output from the secondary resonant circuit 81 is rectified by the rectifier circuit 83 and supplied to the battery 84.

[0039] A3. Power supply sequence: The primary coil L1 is arranged along the extending direction of the road RS, and the secondary coil L2 receives non-contact power supply from the closest primary coil L1.

[0040] In the standby state, the power transmission device 10 generates magnetic flux from the primary coil L1 by passing a standby current through the primary coil L1. When the power receiving device 80 approaches the primary coil L1, the power receiving device 80 uses a secondary detection circuit (not shown) to detect the magnetic flux generated by the primary coil L1. When the magnetic flux generated by the primary coil L1 is detected, the power receiving device 80 generates a starting magnetic flux in step S1 shown in Figure 3 . Specifically, the power receiving device 80 applies alternating current power to a magnetic flux generating coil (not shown). Thereby, the magnetic flux generating coil generates magnetic flux.

[0041] In addition, the method for the power receiving device 80 to detect the closest primary coil L1 is not limited to the above. For example, it can also be detected by photographing an identifier displayed near the primary coil L1 using a camera provided in the power receiving device 80.

[0042] When it is determined that the magnetic flux density represented by the signal output from the magnetic flux detection circuit 14 is greater than the threshold value, the primary side control circuit 13 changes the impedance of the primary side capacitor C1, which is an impedance variable element, in step S3 shown in Figure 3 . Specifically, the primary side control circuit 13 outputs a switching signal Sig1 to the primary side capacitor C1. Thereby, the capacitance value of the primary side capacitor C1 is switched from the second capacitance value to the first capacitance value. As a result, the primary side resonance circuit 12 becomes a resonance state at the operating frequency and transfers to a power transmission state in which a power transmission current flows through the primary coil L1, thereby starting power supply. In this way, when the power transmission device 10 detects an increase in the magnetic flux near the primary coil L1 by the magnetic flux detection circuit 14, it transfers from the standby state to the power transmission state. At the time point when the capacitance value of the primary side capacitor C1 is switched, the power transmission device 10 transfers from the standby state to the power transmission state. Similarly, at the time point when the capacitance value of the primary side capacitor C1 is switched, the power receiving device 80 transfers from the non-power receiving state to the power receiving state. In the power receiving state of the power receiving device 80, the protection switch SW1 is set to the non-conducting state.

[0043] As Figure 3 shown, after starting power reception, the secondary side control circuit 85 of the power receiving device 80 determines in step S5 whether a stop signal, which is a power supply stop signal, is input. If it is determined that the stop signal is input, then in step S7, the secondary side control circuit 85 determines whether an abnormal signal, which is a power supply stop signal, is input. If it is determined that the abnormal signal is not input, the secondary side control circuit 85 returns the process to step S5.

[0044] On the other hand, when it is determined in step S5 that a stop signal has been input and when it is determined in step S7 that an abnormal signal has been input, the secondary-side control circuit 85 sets the protection switch SW1 to the on state in step S15. Specifically, the secondary-side control circuit 85 switches the protection switch SW1 from the non-conductive state to the conductive state. Specifically, the secondary-side control circuit 85 outputs a high-level signal Sig2 to the protection switch SW1. As a result, the protection switch SW1 becomes conductive, and one terminal and the other terminal of the secondary-side coil L2 are short-circuited. As a result, the impedance of the secondary-side resonance circuit 81 increases, and the current flowing through the secondary-side coil L2 decreases. Therefore, the current supplied to the battery 84 decreases, thereby protecting the battery 84. In addition, by short-circuiting one terminal and the other terminal of the secondary-side coil L2, the secondary-side coil L2 can function as a cancellation coil for canceling the magnetic flux generated by the primary-side coil L1.

[0045] Specifically, when the inductance of the secondary-side coil L2 is set to "L", the capacitance value of the secondary-side capacitor C2 is set to "C / 2", the capacitance value of the secondary-side capacitor C3 is set to "C / 2", and the resistance value of the resistance component of the secondary-side resonance circuit 81 is set to "r", the impedance "Z" of the secondary-side resonance circuit 81 when the protection switch SW1 is in the non-conductive state is represented by Equation (1). Z = r + j(ωL - 1 / ωC)…(1) In addition, in Equation (1), j represents the imaginary unit, and ω represents the angular frequency. The frequency at which the imaginary part of Equation (1) is zero is the resonance frequency. When the protection switch SW1 becomes conductive, the impedance of the secondary-side resonance circuit 81 becomes a value different from Equation (1). Therefore, when AC power at the resonance frequency is input to the secondary-side resonance circuit 81, the imaginary part of Equation (1) is not zero, and the impedance of the secondary-side resonance circuit 81 increases. Therefore, the current flowing through the secondary-side coil L2 decreases compared to the current flowing through the secondary-side coil L2 when the protection switch SW1 is in the non-conductive state.

[0046] Since the impedance of the secondary resonant circuit 81 increases, the input impedance of the primary resonant circuit 12 increases. As a result, the current flowing through the primary coil L1 decreases, and the magnetic flux density detected by the magnetic flux detection circuit 14 becomes smaller. If it is determined in step S17 that the detected value Bd of the magnetic flux density represented by the signal output from the magnetic flux detection circuit 14 is less than the reference magnetic flux density Bth, the primary control circuit 13 outputs a switching signal Sig1 for switching to the second capacitance value to the primary capacitor C1 in step S19. As a result, the primary resonant circuit 12 becomes a non-resonant state at the operating frequency and power transmission stops. Therefore, when the power receiving device 80 stops receiving power, power transmission in the power transmission device 10 can be stopped without additional communication. Thereby, power consumption that does not contribute to the power supply to the power transmission device 10 can be suppressed.

[0047] According to the first embodiment described above, the power receiving device 80 has a protection switch SW1. Therefore, in the case where the power receiving device 80 is in an abnormal state or the like, the protection switch SW1 can be used to reduce the current flowing through the secondary coil L2 to protect the battery 84. If the magnetic flux near the primary coil L1 becomes smaller during the power transmission state, the primary control circuit 13 changes the capacitance value of the primary capacitor C1 to increase the impedance of the primary resonant circuit 12 and shifts to the standby state. Thereby, power consumption that does not contribute to the power supply to the power transmission device 10 can be suppressed.

[0048] B. Second Embodiment: As Figure 4 shown, the circuit structure of the primary resonant circuit 212, the circuit structure of the transient circuit 282, the circuit structure of the rectifying circuit 283, the implementation manner of the protection switch, and the power supply sequence of the non-contact power supply system 201 of the present embodiment are different from those of the first embodiment described above. The same reference numerals are used for the same structures and processing steps as those in the first embodiment, and detailed descriptions are appropriately omitted.

[0049] The primary resonant circuit 212 includes a first capacitor C21, a second capacitor C22, and a primary coil L1. The first capacitor C21 and the second capacitor C22 are connected in series with the primary coil L1. The capacitance value of the first capacitor C21 is smaller than that of the second capacitor C22. In addition, the power transmission device 210 includes a switch SW21 that bypasses the first capacitor C21. In the power transmission state of the power transmission device 210, the switch SW21, which is an impedance variable element, is set to the conducting state. In the standby state of the power transmission device 210, the switch SW21 is set to the non-conducting state. When the switch SW21 is set to the conducting state, the capacitance value of the second capacitor C22 is set to a value that causes the primary coil L1 to be in the resonant state at the operating frequency. When the switch SW21 is set to the non-conducting state, the impedance of the primary resonant circuit 212 increases, and a standby current smaller than the power transmission current flows through the primary coil L1.

[0050] In the present embodiment, instead of the magnetic flux detection circuit 14 of the first embodiment, a voltage sensor M1 is provided as the primary side detection circuit. The voltage sensor M1 is used to detect the magnitude of the magnetic flux linked to the primary coil. Specifically, the voltage sensor M1 detects the voltage of the second capacitor C22 and outputs a signal representing the detected value to the primary side control circuit 13. The larger the current value flowing through the primary coil L1, the larger the detected value of the voltage sensor M1 becomes. Therefore, similarly to the first embodiment, it is possible to detect a decrease in the current flowing through the secondary coil L2 in the power receiving device 280.

[0051] The transient circuit 282 of the present embodiment is different from that of the first embodiment in that it does not have the coils L3 and L5 of the transient circuit 82 of the first embodiment. In the present embodiment, the leakage inductance of the secondary coil L2 is used as the coils L3 and L5 of the transient circuit 82 of the first embodiment. That is, the transient circuit 282 functions as a transient circuit through the leakage inductance of the secondary coil L2, the coils L4 and L6, and the capacitor C4.

[0052] The rectifier circuit 283 of the present embodiment is configured to use two switching elements instead of two of the four diodes of the diode bridge. Specifically, the rectifier circuit 283 includes diodes D1 and D2 and switching elements Q1 and Q2 as switches. The diodes D1 and D2 form an upper arm connected to the positive side supply line N3 connected to the positive terminal of the battery 84. The switching elements Q1 and Q2 form a lower arm connected to the negative side supply line N4 connected to the negative terminal of the battery 84. The switching elements Q1 and Q2 are driven in a complementary manner. The control signals output from the secondary side control circuit 85 are input to the gate terminals of the switching elements Q1 and Q2 respectively. In the present embodiment, the switching elements Q1 and Q2 are MOSFETs.

[0053] In the present embodiment, a triac TR is provided as a protection switch. The signal output from the secondary control circuit 85 is input to the gate terminal of the triac TR.

[0054] As Figure 5 shown, when it is determined in step S5 that a stop signal has been input and when it is determined in step S7 that an abnormal signal has been input, the secondary control circuit 85 sets the switching elements Q1 and Q2 of the rectifying circuit 283 to the conducting state in step S11. As a result, since the first power supply line N1 and the second power supply line N2 are short-circuited via the switching elements Q1 and Q2, the current supplied to the battery 84 can be reduced. Therefore, it is possible to suppress the application of an overcurrent or overvoltage to the battery 84 and protect the battery 84. Since the transient circuit 282 becomes a constant current source when viewed from the output side, even when the two output nodes of the transient circuit 282 are short-circuited due to the switching elements Q1 and Q2 being set to the conducting state, different from a constant voltage source, it is possible to suppress the flow of an excessive current. Therefore, it is possible to protect the battery 84 while avoiding the application of an excessive current or voltage to the switching elements Q1 and Q2.

[0055] The secondary control circuit 85 switches the triac TR, which is the protection switch, to the conducting state in step S15. As a result, similarly to the first embodiment, the current flowing through the secondary coil L2 can be reduced. Before switching the triac TR to the conducting state, by setting the switching elements Q1 and Q2 to the conducting state, the battery 84 can be protected earlier.

[0056] When it is determined in step S17 that the voltage value Vd represented by the signal output from the voltage sensor M1 is less than the reference voltage Vth, the primary control circuit 13 outputs a high-level signal for setting the switch SW21 to the conducting state to the switch SW21 in step S19. As a result, the primary resonance circuit 212 becomes a non-resonant state at the operating frequency and power transmission stops.

[0057] According to the second embodiment described above, the same effects as those of the first embodiment are achieved. In addition, during the period when the protection switch SW1 is switched to the conducting state, by setting the switching elements Q1 and Q2 of the rectifying circuit to the conducting state, the battery 84 can be protected earlier.

[0058] C. Third Embodiment: As Figure 6As shown, the circuit structure of the primary resonance circuit 312 of the power transmission device 310, the circuit structure of the power reception device 380, the implementation manner of the protection switch, and the power supply sequence of the non-contact power supply system 301 of this embodiment are different from those of the above embodiments. The same symbols are used to label the same structures and processing steps as those of the above embodiments, and detailed descriptions are appropriately omitted.

[0059] In the primary resonance circuit 312 of this embodiment, the primary capacitor C31 is connected in parallel with the primary coil L1. The power transmission device 310 of this embodiment further includes a resistor R1. The resistor R1 is connected in series with the primary coil L1.

[0060] In this embodiment, the voltage sensor M1 serving as the primary detection circuit detects the voltage of the resistor R1 and outputs a signal representing the detected value to the primary control circuit 13. The larger the current value flowing through the primary coil L1, the larger the detected value of the voltage sensor M1 becomes. Therefore, similar to the first embodiment, it is possible to detect a decrease in the current flowing through the secondary coil L2 in the power reception device 280. In addition, the power transmission device 310 may have a coil instead of the resistor R1. In this case, the voltage sensor M1 detects the voltage of the coil.

[0061] In addition, in this embodiment, the switch SW31 serving as the impedance variable element is connected in series with the primary coil L1. When the switch SW31 is in the non-conducting state, the impedance of the switch SW31 becomes large, and the primary resonance circuit 312 becomes a non-resonant state.

[0062] The power reception device 380 includes a semiconductor relay RE as the protection switch. In this embodiment, the semiconductor relay RE bypasses the secondary capacitor C3. In addition, the semiconductor relay RE may be connected to bypass the secondary capacitor C2 instead of the secondary capacitor C3.

[0063] As Figure 7 shown, when it is determined in step S5 that a stop signal has been input or when it is determined in step S7 that an abnormal signal has been input, the secondary control circuit 85 sets the switching elements Q1 and Q2 of the rectifier circuit 283 to the non-conducting state in step S13. The secondary control circuit 85 switches the semiconductor relay RE to the conducting state in step S15. Since the semiconductor relay RE is connected in parallel with the secondary capacitor C3, if the semiconductor relay RE is switched to the conducting state while the switching elements Q1 and Q2 of the rectifier circuit 283 are in the conducting state, it is possible for an excessive current to flow through the secondary coil L2. Therefore, by switching the semiconductor relay RE to the conducting state while the switching elements Q1 and Q2 of the rectifier circuit 283 are in the non-conducting state, damage to the secondary coil L2 can be avoided.

[0064] According to the third embodiment described above, the same effects as those of the above-described embodiments can be achieved, and by switching the semiconductor relay RE to the conducting state in the non-conducting states of the switching elements Q1 and Q2 of the rectifier circuit 283, damage to the secondary-side coil L2 can be avoided.

[0065] D. Fourth Embodiment: As Figure 8 shown, the circuit structure of the power transmission device 410 and the circuit structure of the power reception device 480 of the non-contact power supply system 401 of the present embodiment are different from those of the above-described embodiments. The same symbols are used to denote the same structures and processing steps as those of the above-described embodiments, and detailed descriptions are appropriately omitted.

[0066] The power transmission device 410 includes a characteristic change circuit 15. The characteristic change circuit 15 is a closed circuit formed by connecting a coil L41 and a capacitor C42 in series. The coil L41 is arranged at a position where it can be magnetically coupled with the primary-side coil L1. The resonance frequency of the characteristic change circuit 15 is greater than the operating frequency.

[0067] The characteristic change circuit 15 has a function of reducing the current flowing through the primary-side coil L1 when the distance between the primary-side coil L1 and the secondary-side coil L2 is long and the coupling coefficient between the primary-side coil L1 and the secondary-side coil L2 is small. Specifically, the capacitance value of the primary-side capacitor C1 is set to a value that becomes a resonant state at the operating frequency when the coupling coefficient between the primary-side coil L1 and the secondary-side coil L2 is the target value. Here, the target value of the coupling coefficient is the coupling coefficient when the distance between the primary-side coil L1 and the secondary-side coil L2 is close and is the target distance at which non-contact power supply is possible. When the coupling coefficient between the primary-side coil L1 and the secondary-side coil L2 is small, the inductance of the primary-side resonance circuit 12 increases, and the current flowing through the primary-side coil L1 decreases.

[0068] The power reception device 480 includes two protection switches SW41 and SW42. The protection switches SW41 and SW42 are semiconductor switching elements. In the present embodiment, the protection switches SW41 and SW42 are MOSFETs. The protection switch SW41 is inserted into the first power supply line N1. The protection switch SW42 is inserted into the second power supply line N2.

[0069] As other forms of the protection switches SW41 and SW42, a bidirectional switch having two MOSFETs may also be used. Additionally, a form in which a protection switch is inserted only into either the first power supply line N1 or the second power supply line N2 may also be used.

[0070] The rectifier circuit 483 includes two diodes forming the lower arm and two switching elements Q1 and Q2 forming the upper arm.

[0071] Similar to the first embodiment, when it is determined that a stop signal has been input or when it is determined that an abnormal signal has been input, the secondary control circuit 85 sets the protection switches SW41 and SW42 from the conducting state to the non-conducting state. As a result, since the power supply to the battery 84 is cut off, the battery 84 can be protected.

[0072] When the protection switches SW41 and SW42 are set to the non-conducting state, the secondary resonant circuit 81 becomes a non-resonant state, and the current flowing through the secondary coil L2 decreases. In this case, when observed from the primary resonant circuit 12, it can be regarded that the secondary coil L2 does not exist, and the current I1 flowing through the primary resonant circuit 12 is represented by Equation (2). I1 = r3 / (ω 2 ·L 13 3 ) ·V1· · · (2) In Equation (2), r3 is the winding resistance value of the coil L41, L 13 is the mutual inductance between the primary coil L1 and the coil L41, and V1 is the output voltage of the AC power supply 11. In Equation (2), since the denominator "ω 2 ·L 13 3 " is sufficiently large with respect to the numerator "r3", the current I1 is almost zero amperes.

[0073] According to the fourth embodiment described above, the same effects as those of the above-described embodiments are achieved.

[0074] E. Fifth Embodiment: As Figure 9 shown, the difference between the non-contact power supply system 501 of this embodiment and the above-described second embodiment is that the power receiving device 580 has a state detection circuit 87. The same symbols are assigned to the same structures and processing steps as those of the above-described embodiments, and detailed descriptions are appropriately omitted.

[0075] The state detection circuit 87 detects whether the state of the power transmission device 210 is the standby state or the power transmission state. The state detection circuit 87 has a temperature sensor M4. The temperature sensor M4 is arranged near the transient circuit 282. In addition, the temperature sensor M4 may be arranged near the switching elements Q1 and Q2 instead of near the transient circuit 282 to detect the temperature near the switching elements Q1 and Q2.

[0076] The state detection circuit 87 detects the transient circuit 282 and the temperature, and when the detected temperature Td is greater than a predetermined reference temperature Tth, outputs a signal indicating that the power transmission device 210 is in the power transmission state to the secondary control circuit 85.

[0077] As shown Figure 10 In the secondary - side control circuit 85, in step S11 which is the first process, after setting the switching elements Q1 and Q2 of the rectifier circuit 283 to the conducting state, if it is determined in step S14 that the detected temperature Td of the temperature sensor M4 is greater than a predetermined reference temperature Tth, then in step S15, the triac TR which is a protection switch is switched to the conducting state.

[0078] In step S11, when the switching elements Q1 and Q2 of the rectifier circuit 283 are set to the conducting state, as described above, the current flowing through the secondary - side coil L2 decreases. However, when the circuit constants of the primary - side resonant circuit 212 deviate from the design values, the detected value of the voltage sensor M1 of the current flowing through the primary - side coil L1 may sometimes be not less than the reference voltage. In this case, the power - transmission device 210 does not shift to the standby state, and the same current as in the power - receiving state flows through the primary - side coil L1. Therefore, the temperature of the transient circuit 282 does not decrease. Thus, in step S14, when the secondary - side control circuit 85 determines that the detected temperature Td of the temperature sensor M4 is greater than the reference temperature Tth, it switches the triac TR to the conducting state. Thereby, in the case where the power - transmission device 210 does not shift to the standby state even when the switching elements Q1 and Q2 of the rectifier circuit 283 are set to the conducting state, by switching the triac TR to the conducting state, the power - transmission device 210 can be shifted to the standby state. Additionally, when it is determined that the detected temperature Td of the temperature sensor M4 is not greater than the reference temperature Tth, since the power - transmission device 210 has already shifted to the standby state after the switching elements Q1 and Q2 of the rectifier circuit 283 are set to the conducting state, the secondary - side control circuit 85 does not switch the protection switch SW1 to the conducting state.

[0079] According to the fifth embodiment described above, the same effects as those of the above - described respective embodiments are achieved. Additionally, when the temperature detected by the temperature sensor M4 is higher than the reference temperature Tth and the current during power supply continuously flows through the secondary - side coil L2, by switching the triac TR to the non - conducting state in step S15, the power - transmission device 210 can be shifted to the standby state.

[0080] F. Other Embodiments: (F1)In the above-described first embodiment, in the primary resonance circuit 12, the primary capacitor C1 and the primary coil L1 are connected in series, and in the secondary resonance circuit 81, the secondary capacitor C2 and the secondary coil L2 are connected in series, which is a so-called S-S type circuit configuration. The circuit configurations of the primary resonance circuit 12 and the secondary resonance circuit 81 are not limited to the S-S type. (a) For example, in the primary resonance circuit 12, the primary capacitor C1 and the primary coil L1 may be connected in parallel, and in the secondary resonance circuit 81, the secondary capacitor C2 and the secondary coil L2 may be connected in series, which is a so-called P-S type circuit configuration. (b) Additionally, in addition to the primary capacitor C1 connected in series with the primary coil L1, it may further include a capacitor connected in parallel with the primary coil L1, and in the secondary resonance circuit 81, two secondary capacitors C2 may be respectively connected in series at both terminals of the secondary coil L2, which is a so-called P-SS type circuit configuration. (c) Further, the primary resonance circuit 12 may also have a closed circuit in which a coil and a capacitor are connected in series. The coil of the closed circuit is arranged at a position where it can be magnetically coupled with the secondary coil L2 when the primary coil L1 and the secondary coil L2 are magnetically coupled. (d) In addition, the capacitor of the closed circuit may be connected in parallel with the coil instead of in series with the coil. (e) Additionally, the primary resonance circuit 12 may further include a coil connected in series with the primary coil L1 and a capacitor connected in parallel with the coil. The coil is arranged at a position where it can be magnetically coupled with the secondary coil L2 when the primary coil L1 and the secondary coil L2 are magnetically coupled.

[0081] (F2)In the above-described second embodiment, the switching elements Q1 and Q2 included in the rectifying circuit 83 are implemented by MOSFETs. In other embodiments, the switching elements Q1 and Q2 may also be implemented by other semiconductor elements, for example, by an IGBT (Insulated Gate Bipolar Transistor) connected with a freewheeling diode.

[0082] (F3)In the above-described second embodiment, the lower arm of the rectifying circuit 283 is composed of the switching elements Q1 and Q2, and the upper arm is composed of diodes. As another method, the rectifying circuit 283 may also be implemented by a synchronous rectifying circuit in which both the upper arm and the lower arm are composed of switching elements. In this case, the synchronous rectifying circuit can be used to apply AC power from the battery 84 to the secondary coil L2. Therefore, in step S1, the secondary coil L2 can also function as a magnetic flux generating coil by applying AC power to the secondary coil L2.

[0083] (F4) In the above-described fifth embodiment, the state detection circuit 87 detects the transient circuit 282 and the temperature. When the detected temperature Td is greater than a predetermined reference temperature Tth, a signal indicating that the power transmission device 210 is in a power transmission state is output to the secondary side control circuit 85. As another mode of the state detection circuit 87, the detected temperature Td of the temperature sensor M4 in step S11 may be stored as the reference temperature, and when the difference between the reference temperature and the current detected temperature is within a predetermined reference range, a signal indicating that the power transmission device 210 is in a power transmission state is output to the secondary side control circuit 85.

[0084] (F5) In the above-described fifth embodiment, the state detection circuit 87 detects the state of the power transmission device 210 by detecting the temperature of the transient circuit 282. As another mode, it may also include a sensor that detects the current flowing through the secondary side coil L2 or the voltage of the secondary side coil L2. When the current flowing through the secondary side coil L2 or the voltage of the secondary side coil L2 does not decrease, it is determined that the power transmission device 210 is in a power transmission state.

[0085] The present disclosure is not limited to the above-described embodiments and modifications, and can be implemented in various structures without departing from its gist. For example, the technical features in the respective embodiments and modifications corresponding to the technical features in each mode described in the Summary of the Invention section can be appropriately replaced or combined to solve part or all of the above technical problems, or to achieve part or all of the above effects. In addition, if a certain technical feature is not described as essential in this specification, it can be appropriately deleted.

[0086] Although the present disclosure has been described based on the embodiments, it should be understood that the present disclosure is not limited to the above embodiments and structures. The present disclosure also includes various modifications and modifications within the equivalent range. In addition, various combinations, modes, and further combinations, modes including only one element, more than one element, or less than one element also belong to the scope and thought range of the present disclosure.

[0087] Other forms: The features of the present disclosure are as follows. (Mode 1) A non-contact power supply system, The above non-contact power supply system (1, 101 to 401) supplies power to the power receiving device (80, 280 to 480) from the power transmission device (10, 210 to 410) in a non-contact manner, The above power transmission device has: A primary side resonance circuit (12, 212, 312), the primary side resonance circuit having a primary side coil (L1) and a primary side capacitor (C1); An AC power supply (11) that applies AC power at a predetermined operating frequency to the primary resonance circuit; An impedance variable element (C1, SW21, SW31) that is connected between the primary coil and the AC power supply and is used to switch the state of the power transmission device between a power transmission state and a standby state; A primary control circuit (13) that changes the impedance of the impedance variable element; and A primary detection circuit (14, M1) that is used to detect either the magnitude of the magnetic flux linked to the primary coil or the magnitude of the magnetic flux near the primary coil, The power receiving device has: A secondary resonance circuit (81) that has secondary capacitors (C2, C3) and a secondary coil (L2) for magnetically coupling with the primary coil; A rectifier circuit (83, 283, 483) that rectifies the AC power output from the secondary resonance circuit; A transient circuit (82, 282) that is connected between the rectifier circuit and the secondary resonance circuit; A load device (83) that receives the DC power output from the rectifier circuit; A protection switch (SW1, TR, RE, SW41, SW42) that sets the secondary resonance circuit to a non-resonant state by being set to either a conducting state or a non-conducting state; and A secondary control circuit (85) that sets the state of the protection switch to either the conducting state or the non-conducting state, The primary control circuit uses the detection value of the primary detection circuit that changes by setting the protection switch to either the conducting state or the non-conducting state, and by changing the impedance of the impedance variable element, transfers the power receiving device from the power transmission state to the standby state. (Mode 2) In the non-contact power supply system described in Mode 1, wherein, The secondary capacitors are connected in series with the secondary coil, The protection switch is connected in parallel with the secondary coil, The secondary control circuit sets the protection switch to the conducting state when receiving a power supply stop signal. (Mode 3) In the non-contact power supply system described in Mode 2, The protection switch is any one of a bidirectional switch using two MOSFETs, a semiconductor relay, and a triac. (Mode 4) In the non-contact power supply system described in Mode 2 or 3, The rectifier circuit has switches (Q1, Q2) in at least one of the lower arm and the upper arm. When the secondary side control circuit receives a power supply stop signal, before setting the protection switch to the conductive state, it sets the switch to the conductive state. (Mode 5) In the non-contact power supply system described in Mode 1, The secondary side capacitor is connected in series with the secondary side coil. The protection switch is connected in parallel with the secondary side capacitor. When the secondary side control circuit receives a power supply stop signal, it sets the protection switch to the conductive state. (Mode 6) In the non-contact power supply system described in Mode 5, The protection switch is any one of a bidirectional switch using two MOSFETs, a semiconductor relay, and a triac. (Mode 7) In the non-contact power supply system described in Mode 5 or 6, The rectifier circuit has switches (Q1, Q2) in at least one of the lower arm and the upper arm. When the secondary side control circuit receives a power supply stop signal, after setting the switch to the non-conductive state, it sets the protection switch to the conductive state. (Mode 8) In the non-contact power supply system described in Mode 1, The secondary side capacitor is connected in series with the secondary side coil. The protection switch is a semiconductor switch element, and the secondary side coil is connected in series between the secondary side capacitor and the rectifier circuit. When the secondary side control circuit receives a power supply stop signal, it switches the protection switch to the non-conductive state. (Mode 9) In the non-contact power supply system described in Mode 8, The protection switch is a bidirectional switch using two MOSFETs. (Mode 10) In the contactless power supply system described in Mode 8, where the protection switch is a MOSFET. (Mode 11) A contactless power supply system, the contactless power supply system (501) supplies power to the power receiving device (580) from the power transmitting device (210) in a contactless manner, the power transmitting device has: a primary resonance circuit (212), the primary resonance circuit having a primary coil (L1) and a primary capacitor (C1); an AC power supply (11), the AC power supply applying AC power at a predetermined operating frequency to the primary resonance circuit; an impedance variable element (SW21), the impedance variable element being connected between the primary coil and the AC power supply and used to switch the state of the power transmitting device between a power transmission state and a standby state; a primary control circuit (13), the primary control circuit changing the impedance of the impedance variable element; and a primary detection circuit (M1), the primary detection circuit being used to detect either the magnitude of the magnetic flux linked to the primary coil or the magnitude of the magnetic flux near the primary coil, the power receiving device has: a secondary resonance circuit (81), the secondary resonance circuit having secondary capacitors (C2, C3) and a secondary coil (L2) for magnetic coupling with the primary coil; a rectifier circuit (283), the rectifier circuit rectifying the AC power output from the secondary resonance circuit and having a switch in at least one of the lower arm and the upper arm; a transient circuit (282), the transient circuit being connected between the rectifier circuit and the secondary resonance circuit; a load device (84), the load device receiving the DC power output from the rectifier circuit; a protection switch (TR), the protection switch setting the secondary resonance circuit to a non-resonant state by being set to either a conducting state or a non-conducting state; and a secondary control circuit (85), the secondary control circuit setting the state of the protection switch to either the conducting state or the non-conducting state; and a state detection circuit (87), the state detection circuit being used to detect the state of the power transmitting device, When the secondary - side control circuit receives a power - supply stop signal, before setting the protection switch to the conducting state, it performs a first process (S11) of setting the switch to the conducting state. After the first process, when the state of the power - transmitting device detected by the state - detection circuit is in the power - transmitting state, the protection switch is set to the conducting state. The primary - side control circuit changes the impedance of the impedance - variable element by using at least one of the detection value of the primary - side detection circuit that changes by setting the switch to the conducting state and the detection value of the primary - side detection circuit that changes by setting the protection switch to either the conducting state or the non - conducting state, so that the power - transmitting device transfers from the power - transmitting state to the standby state. (Mode 12) In the non - contact power - supply system described in Mode 11, The state - detection circuit detects the temperature of at least one of the switch and the transient circuit. When the detected temperature is greater than a pre - determined reference temperature (Tth), it outputs a signal indicating that the power - transmitting device is in the power - transmitting state to the secondary - side control circuit. (Mode 13) A power - transmitting device The power - transmitting device (10, 210 - 410) supplies power to the power - receiving device (80, 280 - 480) in a non - contact manner. The power - transmitting device includes: A primary - side resonant circuit (12, 212, 312), the primary - side resonant circuit having a primary - side coil (L1) and a primary - side capacitor (C1); An AC power source (11), the AC power source applying AC power of a pre - determined operating frequency to the primary - side resonant circuit; An impedance - variable element (C1, SW21, SW31), the impedance - variable element being connected between the primary - side coil and the AC power source and used to switch the state of the power - transmitting device between the power - transmitting state and the standby state; A primary - side control circuit (13), the primary - side control circuit changing the impedance of the impedance - variable element; and A primary - side detection circuit (14, M1), the primary - side detection circuit being used to detect either the magnitude of the magnetic flux linked with the primary - side coil or the magnitude of the magnetic flux near the primary - side coil. The power - receiving device includes: A secondary-side resonant circuit (81), the secondary-side resonant circuit having secondary-side capacitors (C2, C3) and a secondary-side coil (L2) for magnetically coupling with the primary-side coil; A rectifying circuit (83, 283, 483), the rectifying circuit rectifying the AC power output from the secondary-side resonant circuit; A transient circuit (82, 282), the transient circuit being connected between the rectifying circuit and the secondary-side resonant circuit; A load device (83), the load device receiving the DC power output from the rectifying circuit; A protection switch (SW1, TR, RE, SW41, SW42), the protection switch setting the secondary-side resonant circuit to a non-resonant state by being set to either a conducting state or a non-conducting state; and A secondary-side control circuit (85), the secondary-side control circuit setting the state of the protection switch to either the conducting state or the non-conducting state, The primary-side control circuit uses the detection value of the primary-side detection circuit that changes by setting the protection switch to either the conducting state or the non-conducting state, and changes the impedance of the impedance variable element, causing the power receiving device to transfer from the power transmission state to the standby state. (Mode 14) A power receiving device, The power receiving device (80, 280 to 480) receives power supply from a power transmission device (10, 210 to 410) in a non-contact manner, The power transmission device has: A primary-side resonant circuit (12, 212, 312), the primary-side resonant circuit having a primary-side coil (L1) and a primary-side capacitor (C1); An AC power supply (11), the AC power supply applying AC power of a predetermined operating frequency to the primary-side resonant circuit; An impedance variable element (C1, SW21, SW31), the impedance variable element being connected between the primary-side coil and the AC power supply and being used to switch the state of the power transmission device between a power transmission state and a standby state; A primary-side control circuit (13), the primary-side control circuit changing the impedance of the impedance variable element; and A primary-side detection circuit (14, M1), the primary-side detection circuit being used to detect either the magnitude of the magnetic flux linked with the primary-side coil or the magnitude of the magnetic flux near the primary-side coil; The power receiving device has: Secondary-side resonant circuit (81), the secondary-side resonant circuit having secondary-side capacitors (C2, C3) and a secondary-side coil (L2) for magnetically coupling with the primary-side coil; Rectifier circuit (83, 283, 483), the rectifier circuit rectifying the AC power output from the secondary-side resonant circuit; Transient circuit (82, 282), the transient circuit being connected between the rectifier circuit and the secondary-side resonant circuit; Load device (83), the load device receiving the DC power output from the rectifier circuit; Protection switch (SW1, TR, RE, SW41, SW42), the protection switch setting the secondary-side resonant circuit to a non-resonant state by being set to either a conductive state or a non-conductive state; and Secondary-side control circuit (85), the secondary-side control circuit setting the state of the protection switch to either the conductive state or the non-conductive state, The primary-side control circuit uses the detection value of the primary-side detection circuit that changes by setting the protection switch to either the conductive state or the non-conductive state, and changes the impedance of the impedance variable element to transfer the power receiving device from the power transmission state to the standby state.

Claims

1. A non-contact power supply system, the non-contact power supply system (1, 101 - 401) supplies power to a power receiving device (80, 280 - 480) from a power transmitting device (10, 210 - 410) in a non-contact manner. The power transmitting device has: A primary side resonant circuit (12, 212, 312), the primary side resonant circuit having a primary side coil (L1) and a primary side capacitor (C1); An AC power supply (11), the AC power supply applying AC power of a predetermined operating frequency to the primary side resonant circuit; An impedance variable element (C1, SW21, SW31), the impedance variable element being connected between the primary side coil and the AC power supply and being used to switch the state of the power transmitting device between a power transmission state and a standby state; A primary side control circuit (13) that changes the impedance of the impedance variable element; And A primary side detection circuit (14, M1), the primary side detection circuit being used to detect either the magnitude of the magnetic flux linked with the primary side coil or the magnitude of the magnetic flux near the primary side coil. The power receiving device has: A secondary side resonant circuit (81), the secondary side resonant circuit having secondary side capacitors (C2, C3) and a secondary side coil (L2) for magnetic coupling with the primary side coil; A rectifying circuit (83, 283, 483), the rectifying circuit rectifying the AC power output from the secondary side resonant circuit; A transient circuit (82, 282), the transient circuit being connected between the rectifying circuit and the secondary side resonant circuit; A load device (83), the load device receiving the DC power output from the rectifying circuit; A protection switch (SW1, TR, RE, SW41, SW42), the protection switch setting the secondary side resonant circuit to a non-resonant state by being set to either a conducting state or a non-conducting state; And A secondary side control circuit (85), the secondary side control circuit setting the state of the protection switch to either the conducting state or the non-conducting state. The primary side control circuit uses the detection value of the primary side detection circuit that changes by setting the protection switch to either the conducting state or the non-conducting state, and changes the impedance of the impedance variable element to transfer the power receiving device from the power transmission state to the standby state.

2. The non-contact power supply system according to claim 1, wherein The secondary side capacitor is connected in series with the secondary side coil, The protection switch is connected in parallel with the secondary side coil, When receiving a power supply stop signal, the secondary side control circuit sets the protection switch to the conducting state.

3. The non-contact power supply system according to claim 2, wherein The protection switch is any one of a bidirectional switch using two MOSFETs, a semiconductor relay, and a triac.

4. The non-contact power supply system according to claim 2, wherein The rectifying circuit has a switch (Q1, Q2) in at least one of the lower arm and the upper arm. Before setting the protection switch to the conducting state when receiving a power supply stop signal, the secondary side control circuit sets the switch to the conducting state.

5. The contactless power supply system according to claim 1, wherein the secondary side capacitor is connected in series with the secondary side coil, the protection switch is connected in parallel with the secondary side capacitor, when receiving a power supply stop signal, the secondary side control circuit sets the protection switch to the conducting state.

6. The contactless power supply system according to claim 5, wherein the protection switch is any one of a bidirectional switch using two MOSFETs, a semiconductor relay, and a triac.

7. The contactless power supply system according to claim 5, wherein the rectifier circuit has switches (Q1, Q2) in at least one of the lower arm and the upper arm, when receiving a power supply stop signal, after setting the switches to the non-conducting state, the secondary side control circuit sets the protection switch to the conducting state.

8. The contactless power supply system according to claim 1, wherein the secondary side capacitor is connected in series with the secondary side coil, the protection switch is a semiconductor switch element, and the secondary side coil is connected in series between the secondary side capacitor and the rectifier circuit, when receiving a power supply stop signal, the secondary side control circuit switches the protection switch to the non-conducting state.

9. The contactless power supply system according to claim 8, wherein the protection switch is a bidirectional switch using two MOSFETs.

10. The contactless power supply system according to claim 8, wherein the protection switch is one MOSFET.

11. A contactless power supply system, the contactless power supply system (501) supplies power to a power receiving device (580) from a power transmitting device (210) in a contactless manner, the power transmitting device includes: a primary side resonant circuit (212) having a primary side coil (L1) and a primary side capacitor (C1); an AC power supply (11) that applies AC power of a predetermined operating frequency to the primary side resonant circuit; an impedance variable element (SW21) connected between the primary side coil and the AC power supply and used to switch the state of the power transmitting device between a power transmission state and a standby state; The primary control circuit (13) changes the impedance of the impedance variable element; and a primary side detection circuit (M1) for detecting either the magnitude of the magnetic flux linked with the primary side coil or the magnitude of the magnetic flux near the primary side coil, the power receiving device includes: a secondary side resonant circuit (81) having secondary side capacitors (C2, C3) and a secondary side coil (L2) for magnetic coupling with the primary side coil; a rectifier circuit (283) that rectifies the AC power output from the secondary side resonant circuit and has switches in at least one of the lower arm and the upper arm. A transient circuit (282) connected between the rectifying circuit and the secondary resonant circuit; A load device (84) that receives DC power output from the rectifying circuit; A protection switch (TR) that sets the secondary resonant circuit to a non-resonant state by being set to either a conducting state or a non-conducting state; And A secondary control circuit (85) that sets the state of the protection switch to either the conducting state or the non-conducting state; And A state detection circuit (87) for detecting the state of the power transmission device, When receiving a power supply stop signal, the secondary control circuit performs a first process (S11) of setting the switch to the conducting state before setting the protection switch to the conducting state. After the first process, when the state of the power transmission device detected by the state detection circuit is in the power transmission state, the protection switch is set to the conducting state. The primary control circuit changes the impedance of the impedance variable element using at least one of the detection value of the primary detection circuit that changes by setting the switch to the conducting state and the detection value of the primary detection circuit that changes by setting the protection switch to either the conducting state or the non-conducting state, so that the power receiving device transfers from the power transmission state to the standby state.

12. The non-contact power supply system according to claim 11, wherein The state detection circuit detects the temperature of at least one of the switch and the transient circuit, and outputs a signal indicating that the power transmission device is in the power transmission state to the secondary control circuit when the detected temperature is greater than a predetermined reference temperature (Tth).

13. A power transmission device (10, 210 - 410) that supplies power to a power receiving device (80, 280 - 480) in a non-contact manner, The power transmission device has: A primary resonant circuit (12, 212, 312) having a primary coil (L1) and a primary capacitor (C1); An AC power supply (11) that applies AC power of a predetermined operating frequency to the primary resonant circuit; An impedance variable element (C1, SW21, SW31) connected between the primary coil and the AC power supply and used to switch the state of the power transmission device between a power transmission state and a standby state; The primary side control circuit (13) changes the impedance of the impedance variable element; And A primary detection circuit (14, M1) for detecting either the magnitude of the magnetic flux linked with the primary coil or the magnitude of the magnetic flux near the primary coil, The power receiving device has: A secondary resonant circuit (81) having secondary capacitors (C2, C3) and a secondary coil (L2) for magnetic coupling with the primary coil; A rectifying circuit (83, 283, 483) that rectifies the AC power output from the secondary-side resonant circuit; A transient circuit (82, 282) connected between the rectifying circuit and the secondary-side resonant circuit; A load device (83) that receives the DC power output from the rectifying circuit; A protection switch (SW1, TR, RE, SW41, SW42) that sets the secondary-side resonant circuit to a non-resonant state by being set to either a conducting state or a non-conducting state; And A secondary-side control circuit (85) that sets the state of the protection switch to either the conducting state or the non-conducting state, The primary-side control circuit uses the detection value of the primary-side detection circuit that varies by setting the protection switch to either the conducting state or the non-conducting state, and changes the impedance of the impedance variable element to transfer the power receiving device from the power transmission state to the standby state.

14. A power receiving device (80, 280 - 480) that receives power non-contact from a power transmission device (10, 210 - 410), The power transmission device includes: A primary-side resonant circuit (12, 212, 312) having a primary-side coil (L1) and a primary-side capacitor (C1); An AC power source (11) that applies AC power of a predetermined operating frequency to the primary-side resonant circuit; An impedance variable element (C1, SW21, SW31) connected between the primary-side coil and the AC power source and used to switch the state of the power transmission device between a power transmission state and a standby state; A primary side control circuit (13) that changes the impedance of the impedance variable element; And A primary-side detection circuit (14, M1) that detects either the magnitude of the magnetic flux linked to the primary-side coil or the magnitude of the magnetic flux near the primary-side coil; The power receiving device includes: A secondary-side resonant circuit (81) having a secondary-side capacitor (C2, C3) and a secondary-side coil (L2) for magnetic coupling with the primary-side coil; A rectifying circuit (83, 283, 483) that rectifies the AC power output from the secondary-side resonant circuit; A transient circuit (82, 282) connected between the rectifying circuit and the secondary-side resonant circuit; A load device (83) that receives the DC power output from the rectifying circuit; A protection switch (SW1, TR, RE, SW41, SW42) that sets the secondary-side resonant circuit to a non-resonant state by being set to either a conducting state or a non-conducting state; And A secondary-side control circuit (85) that sets the state of the protection switch to either the conducting state or the non-conducting state, The primary - side control circuit uses the detection value of the primary - side detection circuit that varies by setting the protection switch to either the conducting state or the non - conducting state, changes the impedance of the impedance - variable element, and causes the power - receiving device to transfer from the power - transmitting state to the standby state.

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