Inspection method, electric power-receiving device, and non-contact electric power supply system

Abstract

An inspection method comprises: a first step for electrically connecting a first transmission line (TLa) and a second transmission line (TLb), by turning on a protection switch (SWp) during a period in which electric power is being received; and a second step for determining, after the first step, whether an abnormality has occurred, by using the electric current value of an output electric current that flows from a protection circuit (CRp) to a load.

Description

Inspection Method, Power Receiving Device, and Contactless Power Supply System Cross - Reference to Related Applications

[0001] This application is based on Japanese Application No. 2024 - 205890 filed on November 27, 2024, the contents of which are incorporated herein by reference.

[0002] This disclosure relates to an inspection method, a power receiving device, and a contactless power supply system.

[0003] In Patent Document 1, in a power receiving device for contactless power supply, in order to recycle the received alternating current, a device for short - circuiting, for example, the first diode of a diode bridge for rectifying the alternating current by a switch is disclosed.

[0004] Japanese Patent Translation of PCT International Publication No. 2013 - 535948

[0005] When the power receiving device includes a switch for circulating the alternating current as in the above - mentioned technology, this switch may fail. Note that this problem is not limited to the case where the rectifying circuit for rectifying the alternating current is a diode bridge, but is common in rectifying circuits with other circuit configurations.

[0006] This disclosure can be realized in the following forms.

[0007] In a first aspect of this disclosure, an inspection method for a power receiving device that receives power non - contactlessly from a power transmission device is provided. The power receiving device includes a power receiving circuit having a power receiving coil that magnetically couples with a power transmission coil included in the power transmission device, a load to which power received by the power receiving coil is supplied, a protection circuit having a protection switch disposed between the power receiving circuit and the load and electrically connectable between a first transmission line connected to one end of the power receiving coil and a second transmission line connected to the other end of the power receiving coil. The inspection method includes a first step of electrically connecting the first transmission line and the second transmission line by turning on the protection switch during the power - receiving period, and a second step of determining whether there is an abnormality using the current value of the output current flowing from the protection circuit to the load after the first step.

[0008] This configuration allows for testing whether or not the protective switch included in the protective circuit is malfunctioning.

[0009] In a second embodiment of the present disclosure, a power receiving device is provided that receives power from a power transmission device in a non-contact manner. This power receiving device includes a power receiving circuit having a power receiving coil that is magnetically coupled to a power transmission coil of the power transmission device, a load to which power received by the power receiving coil is supplied, a protection circuit having a protection switch capable of electrically connecting a first transmission line connected to one end of the power receiving coil and a second transmission line connected to the other end of the power receiving coil, a current sensor for detecting the current value of the output current flowing from the protection circuit to the load, and a control device, wherein the control device performs a first step of electrically connecting the first transmission line and the second transmission line by turning on the protection switch during the period of power reception, and a second step of determining whether there is an abnormality using the detected current of the current sensor after the first step.

[0010] This configuration allows for testing whether or not the protective switch included in the protective circuit is malfunctioning.

[0011] A third embodiment of the present disclosure provides a contactless power supply system comprising a power transmission device and a power receiving device. The power transmission device comprises a power transmission coil, and the power receiving device comprises a power receiving circuit having a power receiving coil magnetically coupled to the power transmission coil, a load to which power received by the power receiving coil is supplied, a protection circuit having a protection switch capable of electrically connecting a first transmission line connected to one end of the power receiving coil and a second transmission line connected to the other end of the power receiving coil, a current sensor for detecting the current value of the output current flowing from the protection circuit to the load, and a control device, wherein the control device performs a first step of electrically connecting the first transmission line and the second transmission line by turning on the protection switch during the period of power reception, and a second step of determining whether there is an abnormality using the detected current of the current sensor after the first step.

[0012] This configuration allows for testing whether or not the protective switch included in the protective circuit is malfunctioning.

[0013] The above-mentioned and other purposes, features and advantages of this disclosure will be further clarified by the following detailed description with reference to the attached drawings. The drawings are as follows: Figure 1 is a schematic diagram of the contactless power supply system; Figure 2 is a circuit diagram of the contactless power supply system; Figure 3 is a flowchart showing the procedure for the inspection process; Figure 4 is a circuit diagram of the contactless power supply system of the second embodiment; Figure 5 is a diagram showing the change in the positional relationship between the power transmitting coil and the power receiving coil over time; Figure 6 is a flowchart showing the procedure for the inspection process of the second embodiment; Figure 7 is a circuit diagram of the power receiving circuit of the third embodiment; Figure 8 is a circuit diagram of the power receiving circuit of the fourth embodiment; and Figure 9 is a circuit diagram of another embodiment of the protection circuit.

[0014] A. First Embodiment: A1. Schematic Configuration of the Contactless Power Supply System: As shown in Figure 1, the contactless power supply system 1 comprises a power transmission device 10 and a power receiving device 80. In this embodiment, the power transmission device 10 is buried under the road RS. The power receiving device 80 is mounted on a vehicle VE, which is a mobile body traveling on the road RS. While the vehicle VE is traveling, the power receiving device 80 is supplied with power from the power transmission device 10. Here, "while traveling" includes cases where the vehicle VE is moving and cases where the vehicle is stopped, such as at a traffic light. The vehicle VE is configured as, for example, an electric vehicle or a hybrid vehicle.

[0015] The power transmission device 10 includes a power transmission circuit 12 having a power transmission coil L1, and an AC power supply 11 that supplies power to the power transmission circuit 12. The AC power supply 11 supplies power to multiple power transmission circuits 12. The multiple power transmission coils L1 are arranged along the direction of extension of the road RS.

[0016] Furthermore, the mobile device on which the power receiving device 80 is mounted is not limited to vehicles VE traveling on road RS, but may also be, for example, an AGV (Automated Guided Vehicle) or a mobile robot. Also, the power transmission device 10 may be installed not under the road RS, but on a sidewalk adjacent to the road RS, a parking lot, or along the route where the AGV travels.

[0017] The power receiving device 80 includes a battery 84, an auxiliary battery 94, a rectifier circuit 82, a power receiving circuit 81 having a power receiving coil L2, a DC-DC converter 92, an inverter 91, a motor generator 93, an auxiliary device 95, a control device 96, and a vehicle sensor 97. In this embodiment, the power receiving coil L2 is located on the underside of the vehicle VE, opposite the power transmission coil L1.

[0018] A rectifier circuit 82 is connected to the power receiving circuit 81. In the power receiving state, the rectifier circuit 82 converts the AC power received by the power receiving circuit 81 into DC power, and supplies the converted DC power to the battery 84, the DC-DC converter 92, and the inverter 91.

[0019] The battery 84 is a secondary battery that is charged by the supplied DC power. The inverter 91 uses the supplied DC power to drive the motor generator 93. The motor generator 93 operates as a three-phase AC motor and generates the driving force for propulsion. In addition, the motor generator 93 operates as a generator when the vehicle VE is decelerated and regenerates power. The regenerated three-phase AC power is converted to DC power by the inverter 91 and used to charge the battery 84.

[0020] The DC-DC converter 92 steps down the DC power supplied from the rectifier circuit 82 and supplies the stepped-down DC power to the auxiliary battery 94 and the auxiliary equipment 95. The auxiliary equipment 95 includes the vehicle VE's air conditioning system, electric power steering system, headlights, turn signals, wipers and other peripheral equipment, and vehicle VE accessories. The auxiliary battery 94 is a secondary battery for powering the auxiliary equipment 95. The vehicle sensor 97 detects the vehicle VE's speed and its tilt in the longitudinal and lateral directions, and outputs signals indicating the detected speed and tilt of the vehicle VE to the control device 96.

[0021] The control device 96 controls various parts of the power receiving device 80, such as the inverter 91. The control device 96 is implemented including an ECU (engine control unit). The ECU may be implemented with a single microcontroller or with multiple microcontrollers. When multiple microcontrollers are included, for example, it may include a microcontroller that controls mechanisms related to the drive of the vehicle VE, such as the motor generator 93, and a microcontroller that controls mechanisms related to the battery 84, such as the rectifier circuit 82. Furthermore, the control device 96 may be implemented including an ECU that controls various parts and a higher-level ECU that controls multiple ECUs in a unified manner.

[0022] A microcontroller is configured as a computer, including a processor and memory. Each function is realized by the processor executing programs stored in memory.

[0023] A2. Circuit configuration of the contactless power supply system: As shown in Figure 2, the power transmission device 10 is equipped with a power transmission capacitor C1 in addition to the above configuration. The power transmission capacitor C1 is connected in series with the power transmission coil L1 to form a power transmission circuit 12. Note that in Figure 2, only one of the multiple power transmission circuits 12 connected to the AC power supply 11 is shown, and the other power transmission circuits 12 are not shown.

[0024] The AC power supply 11 applies AC power at a predetermined operating frequency to the power transmission circuit 12. In this embodiment, the operating frequency is 85 kHz. When the power transmission coil L1 and the power receiving coil L2 are magnetically coupled, the power transmission circuit 12 enters a resonant state at the operating frequency.

[0025] In addition to the above configuration, the power receiving device 80 includes two power receiving capacitors C2, a filter 88, and an SMR (system main relay) 89 as a relay circuit. The power receiving coil L2 has one end L2a and the other end L2b. The two power receiving capacitors C2 are connected in series to each of the two ends L2a and L2b of the power receiving coil L2, respectively, to form the power receiving circuit 81.

[0026] In this embodiment, the rectifier circuit 82 is configured as a synchronous rectifier circuit. The rectifier circuit 82 has a plurality of leg circuits 98 and a smoothing capacitor C3. The plurality of leg circuits 98 include a first leg circuit 98a and a second leg circuit 98b. The first leg circuit 98a has a first element Q1 and a third element Q3. The second leg circuit 98b has a second element Q2 and a fourth element Q4. In this embodiment, the first element Q1, the second element Q2, the third element Q3, and the fourth element Q4 are realized as N-channel MOSFETs (metal-oxide-semiconductor field-effect transistors), which are switching elements.

[0027] The rectifier circuit 82 has a first output terminal T1 and a second output terminal T2. The drain of the first element Q1 is connected to the first output terminal T1. The third element Q3 is connected in series with the first element Q1. The drain of the second element Q2 is connected to the second output terminal T2. The fourth element Q4 is connected in series with the second element Q2.

[0028] The transmission path through which the received AC current is transmitted, connected to one end L2a of the receiving coil L2, is called the first transmission path TLa. In this embodiment, the first transmission path TLa is the transmission path from one end L2a to the connection point between the first element Q1 and the third element Q3. The transmission path through which the received AC current is transmitted, connected to the other end L2b of the receiving coil L2, is called the second transmission path TLb. In this embodiment, the second transmission path TLb is the transmission path from the other end L2b to the connection point between the second element Q2 and the fourth element Q4.

[0029] Filter 88 suppresses the passage of noise components and allows signals in the desired frequency band to pass through. In Figure 2, filter 88 is shown as a second-order filter, but other filters such as low-pass filters or band-pass filters may also be used.

[0030] The SMR 89 electrically connects the rectifier circuit 82 and the battery 84 when it is ON, and disconnects the electrical connection between the rectifier circuit 82 and the battery 84 when it is OFF. The ON state of the SMR 89 refers to the state in which the contacts of the relay built into the SMR 89 are in contact. The OFF state of the SMR 89 refers to the state in which the contacts of the relay built into the SMR 89 are not in contact. Typically, when an abnormality occurs in the power receiving device 80, the control device 96 sets the SMR 89 to the OFF state, disconnecting the electrical connection between the rectifier circuit 82 and the SMR 89. In Figure 2, a circuit configuration with two relays is shown for the SMR 89, but the circuit configuration is not limited to this. The SMR 89 may have only one relay, or it may be configured with three or more relays.

[0031] The control device 96 controls the rectifier circuit 82 using the first signal Sig1 input to the gates of the first element Q1, the second element Q2, the third element Q3, and the fourth element Q4.

[0032] The control device 96 drives the rectifier circuit 82 to rectify when power is received. During rectification, the first element Q1 and the second element Q2, which constitute the upper arm connected to the positive terminal of the battery 84, are driven complementaryly to each other. Similarly, during rectification, the third element Q3 and the fourth element Q4, which constitute the lower arm connected to the negative terminal of the battery 84, are driven complementaryly to each other. The first element Q1 and the fourth element Q4 are set to the ON state when an ON signal is input to them simultaneously, and set to the OFF state when an OFF signal is input to them simultaneously. Similarly, the second element Q2 and the third element Q3 are set to the ON state when an ON signal is input to them simultaneously, and set to the OFF state when an OFF signal is input to them simultaneously. As a result, the DC power output from the power receiving circuit 81 is rectified by the rectifier circuit 82 and supplied to the battery 84 as a load. The control device 96 drives the rectifier circuit 82 so that a constant current is input to the battery 84. The above driving method is a typical example, and the on and off periods of each element can be adjusted as appropriate.

[0033] The power receiving device 80 further includes a current sensor 71. The current sensor 71 detects the current and transmits a detection signal indicating the detected current to the control device 96. In this embodiment, the current sensor 71 includes a first current sensor 71a and a second current sensor 71b. The first current sensor 71a detects the current value of the input current Iin that is input from the power receiving coil L2 to the rectifier circuit 82 when power is received. The second current sensor 71b detects the current value of the output current Iout that is output from the rectifier circuit 82 when power is received.

[0034] In Figure 2, the first current sensor 71a is positioned between the power receiving circuit 81 and the rectifier circuit 82. However, the position of the first current sensor 71a is not limited to being positioned between the power receiving circuit 81 and the rectifier circuit 82. For example, the first current sensor 71a may be positioned between the power receiving coil L2 and the power receiving capacitor C2. Also, in Figure 2, the second current sensor 71b is positioned between the rectifier circuit 82 and the filter 88. However, the position of the second current sensor 71b is not limited to being positioned between the rectifier circuit 82 and the filter 88. For example, the second current sensor 71b may be positioned between the filter 88 and the SMR 89.

[0035] In the contactless power supply system 1, contactless power is supplied to the power receiving device 80 by magnetic field resonance between the power transmission coil L1 and the power receiving coil L2.

[0036] A3. Function of the protective switch: The protective switch SWp is a switch that has the function of electrically connecting the first transmission line TLa and the second transmission line TLb. By electrically connecting the first transmission line TLa and the second transmission line TLb, a current path CA is formed between one end L2a of the receiving coil L2 and the other end L2b of the receiving coil L2 through which current flows.

[0037] In this embodiment, the third element Q3 and the fourth element Q4 function as a protection switch SWp. The circuit including the protection switch SWp is called the protection circuit CRp. In this embodiment, the rectifier circuit 82 is the protection circuit CRp.

[0038] In this embodiment, by setting the protective switch SWp to the ON state, the current path CA shown by the dashed arrow in Figure 2 is formed. The protective switch SWp is used to protect the circuit, for example, when an abnormality occurs in the power receiving device 80. Specifically, for example, if an abnormality occurs in which the voltage of the battery 84 is abnormally high, the SMR 89 is set to the OFF state. This cuts off the input current to the battery 84, thus protecting the battery 84. In this case, the protective switch SWp is further set to the ON state. This protects the circuit elements of the circuit preceding the battery 84. If current continues to flow to the circuit preceding the battery 84 while the SMR 89 is set to OFF, there is a risk that a voltage exceeding the rated voltage will be applied to the circuit elements of the circuit preceding the battery 84. In this regard, the circuit elements can be protected by forming the current path CA and creating a current loop.

[0039] In the above explanation, it was stated that the SMR89 is set to the off state when an abnormality occurs. However, the above explanation is only one example of operation in the event of an abnormality. The control device 96 does not only turn on the protection switch SWp when the SMR89 is set to the off state. Regardless of whether the SMR89 is in the off or on state, turning on the protection switch SWp protects the circuit preceding the battery 84.

[0040] For example, circuit elements such as protective switches SWp can experience failures such as short circuits. Therefore, the inspection method described below is used to inspect these circuit elements.

[0041] A4. Inspection Method: The control device 96 controls the power receiving device 80 by executing a control program that includes an inspection process program stored in memory. The inspection method for the power receiving device 80 is realized when the control device 96 executes the control program stored in memory. The control device 96 performs the inspection process during the period when the power receiving coil L2 is receiving power. Since the coil current flowing through the power receiving coil L2 increases when power is being received, the control device 96 can determine whether or not power is currently being received using the detected current of the first current sensor 71a.

[0042] In step S20 of FIG. 3, the control device 96 sets the SMR 89 to on and rectifier drives the rectifier circuit 82. As a result, the alternating current received by the power receiving coil L2 is rectified by the rectifier circuit 82, and a direct current is supplied to the battery 84.

[0043] In step S22, the control device 96 turns on the protection switch SWp. In the present embodiment, the control device 96 turns off the first element Q1 and the second element Q2 and turns on the third element Q3 and the fourth element Q4.

[0044] As described above, when the protection switch SWp is turned on, a current path CA is formed. Therefore, when the rectifier circuit 82 is normal, the current value of the output current Iout from the rectifier circuit 82 becomes almost zero amperes. On the other hand, when the rectifier circuit 82 is abnormal, the current value of the output current Iout from the rectifier circuit 82 does not become sufficiently small. Note that the case where the rectifier circuit 82 is normal means the case where there is no failure in the rectifier circuit 82. The case where the rectifier circuit 82 is abnormal means the case where there is a failure in the rectifier circuit 82. Therefore, it is possible to determine whether there is an abnormality by using the current value of the output current Iout flowing from the rectifier circuit 82 to the battery 84.

[0045] In the present embodiment, in order to determine whether the current value of the output current Iout has become sufficiently small, a determination using the difference between the current value of the input current Iin and the current value of the output current Iout is performed. The smaller the current value of the output current Iout, the larger the current difference dI. In step S24, the control device 96 determines whether the current difference dI between the current value of the input current Iin and the current value of the output current Iout is smaller than a predetermined first reference value Is1. The first reference value Is1 is a value smaller than the current difference dI when the rectifier circuit 82 is normal, is obtained by experiments or the like, and is stored in the memory of the control device 96.

[0046] In the present embodiment, in step S24, the difference between the effective current value of the output current Iout and the effective current value of the input current Iin is compared with the first reference value Is1.

[0047] In step S24, if it is determined that the current difference dI is smaller than the first reference value Is1, since there is a high possibility that the rectifier circuit 82 is abnormal, in step S26, the control device 96 determines that it is abnormal and ends this processing routine. In step S24, if it is determined that the current difference dI is not smaller than the first reference value Is1, since there is a high possibility that the rectifier circuit 82 is normal, the control device 96 ends this processing routine.

[0048] When the control device 96 determines that it is abnormal in step S26, for example, it prompts the repair of the failure using an indicator light (not shown) provided in the power receiving device 80.

[0049] Step S22 is also referred to as the first step. Step S24 is also referred to as the second step.

[0050] According to the first embodiment described above, the power receiving device 80 includes a power receiving circuit 81, a battery 84, and a protection circuit CRp having a protection switch SWp. In the inspection process, in step S22, the protection switch SWp is turned on. In step S24, when it is determined that the current difference dI between the current value of the input current Iin flowing into the rectifier circuit 82, which is the protection circuit CRp, and the current value of the output current Iout is equal to or less than the first reference value Is1, in step S26, it is determined that there is an abnormality. Thereby, when the power receiving device 80 receives power, an abnormality of the protection switch SWp can be detected.

[0051] B. Second Embodiment: FIG. 4 is a diagram showing a circuit configuration of the non-contact power supply system 1 of the second embodiment. The circuit configurations of the power transmission device 110 and the power receiving device 180 of this embodiment are different from those of the first embodiment. The same components and processing steps as those in the first embodiment are denoted by the same reference numerals, and detailed descriptions thereof are omitted as appropriate. In FIG. 4, the illustration of the filter 88 is omitted.

[0052] As shown in FIG. 4, the power transmission device 110 of this embodiment includes, in addition to the above configuration, a power transmission side communication unit 14, a current sensor 16, a voltage sensor 17, and a power transmission side control device 20.

[0053] The transmitting-side communication unit 14 communicates wirelessly with the receiving-side communication unit 89 of the receiving device 80. The current sensor 16 detects the current value flowing through the transmitting coil L1 and transmits a signal indicating the detected current value to the transmitting-side control device 20. The voltage sensor 17 detects the voltage value of the transmitting coil L1 and transmits a signal indicating the detected voltage value to the transmitting-side control device 20. The transmitting-side control device 20 controls each part included in the transmitting device 10, such as the transmitting-side communication unit 14. The transmitting-side control device 20 includes a computer, which includes a processor and memory.

[0054] The power transmission capacitor C1 of the power transmission circuit 112 in this embodiment includes a first power transmission capacitor C1a and a second power transmission capacitor C1b. The power transmission circuit 112 also further includes a power transmission switch 18. The power transmission capacitor C1 in this embodiment has the function of making the power transmission circuit 112 resonant at the operating frequency and also making the power transmission circuit 112 non-resonant at the operating frequency.

[0055] The first power transmission capacitor C1a is connected in series with the power transmission coil L1. The second power transmission capacitor C1b is connected in series with the power transmission switch 18. The connection between the second power transmission capacitor C1b and the power transmission switch 18 is connected in parallel with the first power transmission capacitor C1a. In this embodiment, the power transmission switch 18 is a bidirectional switch with the sources of two FETs connected to each other. The gates of the two FETs are input to the switching signal Sig2 output from the power transmission side control device 20. This controls the on / off state of the power transmission switch 18.

[0056] When a high-level switching signal Sig2 is input to the power transmission switch 18, the power transmission switch 18 turns ON, i.e., becomes conductive, and current flows through the second power transmission capacitor C1b. Here, the combined capacitance of the first power transmission capacitor C1a and the second power transmission capacitor C1b, and the inductance of the power transmission coil L1 are set to values ​​that result in a resonant state at the operating frequency when the power transmission coil L1 and the power receiving coil L2 are magnetically coupled. As a result, when the power transmission switch 18 is ON, the power transmission circuit 112 becomes resonant due to the first power transmission capacitor C1a, the second power transmission capacitor C1b, and the power transmission coil L1. Conversely, when a low-level switching signal Sig2 is input to the power transmission switch 18, the power transmission switch 18 turns OFF, i.e., becomes non-conductive. Then, since the resonant frequency of the resonant circuit formed by the first power transmission capacitor C1a and the power transmission coil L1 deviates from the operating frequency, the power transmission circuit 112 becomes non-resonant.

[0057] The power transmission control device 20 sets the power transmission circuit 112 to a resonant state when transmitting power, and sets the power transmission circuit 112 to a non-resonant state when not transmitting power. The power transmission control device 20 also uses the current sensor 16 and the voltage sensor 17 to determine whether contactless power supply is functioning correctly. Specifically, in determining whether contactless power supply is functioning correctly, the power transmission control device 20 determines that normal contactless power supply is not occurring if the difference between the phase of the current detected by the current sensor 16 and the phase of the voltage detected by the voltage sensor 17 is different from the difference between the phase of the current and the phase of the voltage in the power transmission coil L1 when the power transmission coil L1 and the power receiving coil L2 are magnetically coupled as intended.

[0058] The rectifier circuit 182 in this embodiment is implemented as a diode bridge. The protection circuit CRp in this embodiment is composed of a bidirectional switch including switching elements Q5 and Q6, which are protection switches SWp. The protection circuit CRp is located between the power receiving coil L2 and the power receiving capacitor C2. The switching elements Q5 and Q6 are N-channel MOSFETs. The switching elements Q5 and Q6 are connected in series with respect to each other so that their respective sources are connected. The drain of switching element Q5 is connected to the first transmission line TLa. The drain of switching element Q6 is connected to the second transmission line TLb. The first signal Sig1 is input to the gates of switching elements Q5 and Q6. In this embodiment as well, the current path CA is formed when switching elements Q5 and Q6 are turned on.

[0059] In this embodiment, the first current sensor 71a is positioned between the power receiving coil L2 and the protection circuit CRp. In this embodiment, the second current sensor 71b is positioned between the protection circuit CRp and the power receiving capacitor C2.

[0060] The power receiving device 180 of this embodiment includes a voltage sensor 72 that detects the battery voltage, which is the voltage of the battery 84. The voltage sensor 72 transmits a detection signal indicating the detected voltage to the control device 96. The voltage sensor 72 is used to determine the remaining charge of the battery 84.

[0061] In addition to the above configuration, the power receiving device 80 includes a power receiving side communication unit 89. The power receiving side communication unit 89 communicates wirelessly with the power transmitting side communication unit 14 of the power transmitting device 10.

[0062] In this embodiment, when the power receiving device 80 approaches the power transmitting device 10, the control device 96 controls the power receiving side communication unit 89 to send a request signal to the power transmitting device 10 requesting power reception. When the power transmitting side communication unit 14 of the power transmitting device 10 receives the request signal, the power transmitting side control device 20 uses a switching signal Sig2 to turn on the power transmission switch 18. As a result, the power transmission circuit 112 enters a resonant state, and power for power transmission is supplied to the power transmission coil L1. This enables contactless power supply from the power transmitting device 10 to the power receiving device 80.

[0063] There are various methods by which the power receiving device 80 can detect when it has approached a position where it can receive power from the power transmitting device 10 in order to transmit a request signal. For example, the control device 96 can detect when it has approached a position where it can receive power from the power transmitting device 10 by acquiring the position information of the power receiving device 80 and the position information of the vehicle VE. Alternatively, for example, the power transmitting device 110 may, during periods when it is not transmitting power, flow a current smaller than the power supply current through the power transmitting coil L1 to cause the power transmitting coil L1 to radiate a magnetic field. The power receiving device 180 can detect whether or not the power transmitting device 110 is present in a position where it can receive power by detecting the magnetic field generated by the power transmitting coil L1 using a magnetic field sensor (not shown). Alternatively, for example, a visible mark may be placed on the road RS where the power transmitting device 110 is located, and the power receiving device 180 can detect whether or not the power transmitting device 110 is present in a position where it can receive power by imaging this mark with a camera (not shown).

[0064] As shown in Figure 5, the transmission coils L1 are arranged in the direction of the road RS, and the receiving coil L2 receives contactless power from the nearest transmission coil L1. In Figure 5, the transmission coils L1 and receiving coil L2 that are exchanging power are shown by hatching. The arrows in Figure 5 indicate the direction of travel of the vehicle VE on which the receiving coil L2 is mounted. At "time t1" in Figure 5, the receiving coil L2 is shown approaching the arranged transmission coils L1. As shown at "time t2" in Figure 3, when the receiving coil L2 approaches the end transmission coil L1, contactless power supply begins. As shown in "time t3" in Figure 3, as the vehicle VE moves forward, when the distance between the transmission coil L1 adjacent to the terminal transmission coil L1 and the receiving coil L2 becomes shorter than the distance between the terminal transmission coil L1 and the receiving coil L2, the transmission coil L1 that transmits and receives power switches from the terminal transmission coil L1 to the transmission coil L1 adjacent to the terminal transmission coil L1.

[0065] When the power receiving device 80 starts receiving power via the power receiving coil L2, it performs the inspection process shown in Figure 6 within a predetermined time from the moment power receiving begins. When power receiving begins, the detected current of the first current sensor 71a increases, so the control device 96 can determine that power receiving has started. The predetermined time is, for example, a few microseconds. By performing the inspection process within a predetermined time from the moment power receiving via the power receiving coil L2 begins, abnormalities in the protection circuit CRp can be detected early. If power is received when there is an abnormality in the protection circuit CRp, the scope of the failure in the power receiving device 180 may expand. In this regard, by performing the inspection process early and stopping power receiving if an abnormality is found, the expansion of the failure can be suppressed.

[0066] In this embodiment, as shown in Figure 5, the inspection process is performed when power reception begins with the terminal power transmission coil L1 that is the first to receive power among the multiple power transmission coils L1 arranged in the extending direction of the road RS. In other words, the inspection process is performed only while power is being received with one of the multiple power transmission coils L1 arranged in the road RS. In another embodiment, the control device 96 may perform the inspection process while power is being received with each of the multiple power transmission coils L1 arranged in the road RS.

[0067] The control device 96 performs steps 22 and S25 within a predetermined time from the moment power reception by the receiving coil L2 begins. This allows for early detection of abnormalities in the rectifier circuit 182.

[0068] In step S10 of Figure 6, the control device 96 determines whether the remaining charge of the battery 84 is equal to or greater than a predetermined reference amount. In this embodiment, the control device 96 uses the detected voltage of the voltage sensor 72 to determine the remaining charge of the battery 84. When the protection switch SWp is turned on, no current is supplied to the battery 84. Therefore, if the battery charge is low, charging the battery 84 is prioritized over inspection. In this embodiment, the reference amount used for determination is set to 10% when expressed as a percentage with full charge being 100%.

[0069] In step S10, if the control device 96 determines that the battery charge is not equal to or greater than the standard amount, it terminates this processing routine.

[0070] In step S10, if it is determined that the battery level is above the standard amount, in step S12, the control device 96 determines whether the vehicle VE is traveling uphill with a gradient greater than or equal to the standard gradient. In this embodiment, the control device 96 uses a signal indicating the longitudinal tilt of the vehicle VE transmitted from the vehicle sensor 97 to determine the gradient of the road RS on which the vehicle VE is traveling. When traveling uphill with a steep gradient, the power consumed by the motor generator 93 is large, so the rate at which the charge level of the battery 84 decreases increases. Therefore, if the vehicle is traveling uphill with a gradient greater than or equal to the standard gradient, charging the battery 84 is prioritized over inspection. In this embodiment, the standard gradient used for determination is set to 10%.

[0071] In step S12, if the control device 96 determines that the vehicle VE is traveling uphill on a slope with a gradient greater than or equal to the standard gradient, the control device 96 terminates this processing routine.

[0072] In step S12, if the control device 96 determines that the vehicle VE is not traveling uphill on a gradient greater than or equal to the standard gradient, in step S14, the control device 96 transmits a start notification signal to the power transmission device 10. When the power transmission side control device 20 of the power transmission device 110 receives the start notification signal, it does not perform an abnormality determination to determine whether contactless power supply is being performed normally until it receives the end notification signal. When the protection switch SWp is turned on in the power receiving device 80, the coupling state between the power transmission coil L1 and the power receiving coil L2 changes, making it impossible to perform an abnormality determination with accuracy. Therefore, the power transmission device 110 can suppress erroneous determinations in abnormality determination by not performing an abnormality determination during the period when the power receiving device 80 is performing an abnormality determination.

[0073] In step S22, the control device 96 turns on the switching elements Q5 and Q6, which are protective switches SWp.

[0074] In this embodiment, when the protection switch SWp is turned on, the output current Iout is compared with a predetermined second reference value Is2 to determine whether the output current Iout has decreased sufficiently. Specifically, in step S24, the control device 96 uses the signal from the second current sensor 71b to determine whether the output current Iout is greater than the second reference value Is2. The second reference value Is2 is a value greater than the output current Iout when the rectifier circuit 82 is functioning normally, and is determined by experimentation or other means and stored in memory. Step S25 is performed within a predetermined time from the time step S22 is performed.

[0075] In step S25, if it is determined that the output current Iout is greater than the second reference value Is2, there is a high possibility that the rectifier circuit 182 is abnormal. Therefore, in step S26, the control device 96 determines that there is an abnormality and proceeds to step S28. In step S25, if it is determined that the output current Iout is not greater than the second reference value Is2, the control device 96 proceeds to step S28.

[0076] In step S28, the control device 96 transmits a termination notification signal to the power transmission device 10, and terminates this processing routine.

[0077] In this embodiment, if the control device 96 determines in step S26 that there is an abnormality, it sends a stop request signal to the power transmission device 110 to stop power transmission. As a result, power transmission from the power receiving device 180 is stopped, which helps to prevent the spread of the malfunction in the power receiving device 180.

[0078] Step S10 is also called the remaining amount determination step. Step S14 is also called the first transmission step. Step S28 is also called the second transmission step. Step S12 is also called the driving determination step.

[0079] According to the second embodiment described above, in step S25, if the current value of the output current Iout from the protection circuit CRp is determined to be greater than the second reference value Is2, then in step S26, an abnormality is determined. This makes it possible to detect an abnormality in the protection switch SWp when the power receiving device 80 receives power.

[0080] Furthermore, steps S22 to S26 are performed when the power transmission device 110 does not determine an abnormality in its abnormality determination. In this embodiment, a start notification signal is transmitted to the power transmission device 110 before step S22. A termination notification signal is transmitted to the power transmission device 110 after step S26. The power transmission device 110 does not perform abnormality determination during the period from when it receives the start notification signal until when it receives the termination notification signal. This suppresses erroneous determinations in the abnormality determination of the power transmission device 110.

[0081] Furthermore, in step S10, the control device 96 performs an inspection if it determines that the remaining charge of the battery 84 is above a standard amount. This allows for both proper maintenance of the battery 84's charge level and inspection. Also, in step S12, the control device 96 performs an inspection if it determines that the vehicle VE is not traveling uphill with a gradient greater than or equal to a standard gradient. This allows for both proper maintenance of the battery 84's charge level and inspection.

[0082] C. Third Embodiment: Figure 7 shows a power receiving device 280 of the third embodiment, which differs from the second embodiment in the placement of the protection circuit CRp. In the second embodiment described above, the protection circuit CRp is placed between the power receiving coil L2 and the power receiving capacitor C2. The placement of the protection circuit CRp is not limited to between the power receiving coil L2 and the power receiving capacitor C2. For example, the protection circuit CRp may be placed between the power receiving circuit 81 and the rectifier circuit 182.

[0083] Furthermore, if the power receiving device 80 includes a filter 86 between the power receiving circuit 81 and the rectifier circuit 182, a protection circuit CRp may be placed between the power receiving capacitor C2 and the filter 86, as shown in Figure 7(C1). Alternatively, a protection circuit CRp may be placed between the filter 86 and the rectifier circuit 182, as shown in Figure 7(C2).

[0084] Furthermore, when the power receiving circuit 81 is located at the lower part of the vehicle VE near the road RS, and the rectifier circuit 182 is located closer to the motor generator 93 than the power receiving circuit 81, the power receiving circuit 81 and the rectifier circuit 182 are electrically connected by relatively long wiring. In this case, the protection circuit CRp may be located near the power receiving circuit 81 or near the rectifier circuit 182. For example, if the power receiving circuit 81 is unitized, the protection circuit CRp may be located within this unit. For example, if the rectifier circuit 182 is unitized, the protection circuit CRp may be located within this unit. Also, although Figure 7 shows an example in which the power receiving device 280 is equipped with a filter 86, the power receiving device 280 does not have to be equipped with a filter 86. In the power receiving device 280 of the third embodiment, the protection circuit CRp can also be inspected using the current value of the output current of the protection circuit CRp.

[0085] D. Fourth Embodiment: Figure 8 shows a power receiving device 380 of the fourth embodiment in which the rectifier circuit 182 is composed of diodes and a protection switch SWp is connected in parallel to the diodes. In this embodiment, the rectifier circuit 182 functions as a protection circuit CRp. As shown in (D1) of Figure 8, a protection switch SWp may be connected to each of the two diodes of the rectifier circuit 82 that are connected to the negative terminal of the battery 84. Alternatively, as shown in (D2) of Figure 8, a protection switch SWp may be connected to each of the two diodes of the rectifier circuit 82 that are connected to the positive terminal of the battery 84. In both (D1) and (D2), a current path CA is formed when the two protection switches SWp are turned on. In the power receiving device 380 of the fourth embodiment, the protection circuit CRp can also be inspected using the current value of the output current of the protection circuit CRp.

[0086] E. Other Embodiments (Circuit Configuration of Protection Switch): In the second embodiment described above, the protection circuit CRp is implemented with a bidirectional switch. In another embodiment, as shown in Figure 9, the protection circuit CRp may be implemented with a rectifier circuit and a protection switch SWp which is a MOSFET. In this case as well, when the protection switch SWp is turned on, the current path CA is formed. With this configuration, a current path CA that loops the AC current can be formed with a single protection switch SWp. Note that in Figure 9, the protection circuit CRp is shown to be placed between the power receiving coil L2 and the power receiving capacitor C2, but the placement is not limited to this. For example, as shown in Figure 8, it may be placed between the power receiving capacitor C2 and the rectifier circuit 182.

[0087] F. Other Embodiments: (F1) In each of the above embodiments, the protection switch SWp is implemented with an N-channel MOSFET. In other embodiments, the protection switch SWp may be a P-channel MOSFET, or other transistors such as IGBTs, thyristors, or triacs. Also, in the first embodiment, the third element Q3 and the fourth element Q4 are the protection switch SWp, but the first element Q1 and the second element Q2 may also be the protection switch SWp.

[0088] (F2) In the second embodiment described above, when the power transmission device 110 does not determine that there is an abnormality in its abnormality determination, the power receiving device 180 performs steps S14 and S28 in order to perform inspection processing. The method by which the power receiving device 180 performs inspection processing when the power transmission device 110 does not determine that there is an abnormality in its abnormality determination is not limited to this. For example, the power transmission device 110 performs inspection processing within a predetermined time from the start of power reception. Therefore, the power transmission device 110 may perform abnormality determination after a predetermined time has elapsed from the start of power reception.

[0089] (F3) In the first embodiment described above, the inspection process includes step S20. In other embodiments, the inspection process may not include step S20.

[0090] (F4) In each of the above embodiments, the current values ​​of the input current Iin and the output current Iout are detected by the current sensor 71. The method for detecting the current values ​​of the input current Iin and the output current Iout is not limited to the current sensor 71, but may also be a magnetic flux sensor or a voltage sensor, for example.

[0091] (F5) In the second embodiment described above, the control device 96 calculates the remaining charge of the battery 84 using the voltage sensor 72. In other embodiments, the control device 96 may calculate the remaining charge of the battery 84 using the discharge current of the battery 84, or it may calculate the remaining charge of the battery 84 using the usage status of the battery 84.

[0092] (F6) In the first embodiment described above, the difference between the effective current value of the output current Iout and the effective current value of the input current Iin is compared with a first reference value Is1. The current values ​​to be compared are not limited to the effective current value, but may be, for example, the maximum current value or the current value at a predetermined timing.

[0093] (F7) In the first embodiment described above, reference values ​​such as the first reference value Is1 and the second reference value Is2 are stored in the memory of the control device 96 in advance. The method for comparing the magnitude relationship between the detected current and the reference values ​​is not limited to the above embodiment. For example, a generation circuit that generates a reference current may be provided, and a comparison circuit may be used to compare the reference current generated from the generation circuit with the detected current.

[0094] (F8) In the first embodiment described above, the power transmission circuit 12 has a power transmission capacitor C1 connected in series with the power transmission coil L1, and the power receiving circuit 81 has a power receiving capacitor C2 connected in series with the power receiving coil L2, which is a so-called S-S circuit configuration. The circuit configuration of the power transmission circuit 12 and the circuit configuration of the power receiving circuit 81 are not limited to the S-S method. (a) For example, the power transmission circuit 12 may have a power transmission capacitor C1 connected in parallel with the power transmission coil L1, and the power receiving circuit 81 may have a so-called P-S circuit configuration, where the power receiving coil L2 has a power receiving capacitor C2 connected in series. (b) In addition, the power transmission circuit 81 may have a so-called P-SS circuit configuration, where, in addition to the power transmission capacitor C1 connected in series with the power transmission coil L1, a capacitor is also provided that is connected in parallel with the power transmission coil L1, and each of the two power receiving capacitors C2 is connected in series with each of the ends of the power receiving coil L2. (c) The power transmission circuit 12 may also include a closed circuit in which a coil and a capacitor are connected in series. The coil in this closed circuit is positioned so as to be magnetically coupled with the receiving coil L2 when the power transmission coil L1 and the receiving coil L2 are magnetically coupled. (d) Furthermore, the capacitor in the closed circuit may be connected in parallel with the coil instead of in series. (e) The power transmission circuit 12 may also include a coil connected in series with the power transmission coil L1, as well as a capacitor connected in parallel with the coil. This coil is positioned so as to be magnetically coupled with the receiving coil L2 when the power transmission coil L1 and the receiving coil L2 are magnetically coupled.

[0095] The control devices and methods described herein may be implemented by a dedicated computer provided by configuring a processor and memory programmed to perform one or more functions embodied by a computer program. Alternatively, the control devices and methods described herein may be implemented by a dedicated computer provided by configuring a processor by one or more dedicated hardware logic circuits. Alternatively, the control devices and methods described herein may be implemented by one or more dedicated computers configured by a combination of a processor and memory programmed to perform one or more functions and a processor configured by one or more hardware logic circuits. Furthermore, the computer program may be stored as instructions executed by the computer on a computer-readable non-transitional tangible recording medium.

[0096] This disclosure is not limited to the embodiments and modifications described above, and can be implemented in various configurations without departing from its spirit. For example, the technical features in the embodiments and modifications corresponding to the technical features in each form described in the summary of the invention can be replaced or combined as appropriate in order to solve some or all of the above-mentioned problems, or to achieve some or all of the above-mentioned effects. Furthermore, if a technical feature is not described as essential in this specification, it can be deleted as appropriate.

[0097] Other Embodiments: Features of the present disclosure are as follows: (Embodiment 1) A method for inspecting a power receiving device (80, 180, 280, 380) that receives power from a power transmitting device (10, 110) in a non-contact manner, wherein the power receiving device comprises: a power receiving circuit (81) having a power receiving coil (L2) that is magnetically coupled to a power transmitting coil (L1) provided by the power transmitting device; a load (84) to which power received by the power receiving coil is supplied; and a protection circuit (CRp) having a protection switch (SWp) that can electrically connect a first transmission line (TLa) connected to one end (L2a) of the power receiving coil and a second transmission line (TLb) connected to the other end (L2b) of the power receiving coil, wherein the inspection method comprises: a first step of electrically connecting the first transmission line and the second transmission line by turning on the protection switch during the period of power receiving; An inspection method comprising: (1) After the first step, a second step of determining whether there is an abnormality using the current value of the output current flowing from the protection circuit to the load. (2) An inspection method according to the inspection method of (Form 5) An inspection method according to any one of Forms 1 to 4, wherein the power receiving device is mounted on a vehicle (VE), power receiving by the power receiving coil is performed while the vehicle is in motion, and the first step and the second step are performed within a predetermined time from the time when power receiving by the power receiving coil begins.(Embodiment 6) An inspection method according to any one of Embodiments 1 to 5, wherein the power receiving device is mounted on a vehicle (VE), power receiving by the power receiving coil is performed while the vehicle is running, the load is a battery, and further includes a remaining charge determination step of determining whether the remaining charge of the battery is equal to or greater than a predetermined standard amount, and if it is determined in the remaining charge determination step that the remaining charge of the battery is equal to or greater than the standard amount, the first step and the second step are performed. (Embodiment 7) An inspection method according to any one of Embodiments 1 to 6, wherein the power transmitting device makes an abnormality determination regarding power supply using the current flowing through the power transmitting coil and the voltage of the power transmitting coil, and the inspection method further includes a first transmission step of transmitting a start notification signal to the power transmitting device before the first step, and a second transmission step of transmitting an end notification signal to the power transmitting device after the second step, and the power transmitting device does not make the abnormality determination during the period from when it receives the start notification signal until when it receives the end notification signal. (Embodiment 8) An inspection method according to any one of embodiments 1 to 7, wherein the power receiving device is mounted on a vehicle, power is received by the power receiving coil while the vehicle is in motion, and the inspection method further includes a driving determination step of determining whether the vehicle is traveling up a slope with a predetermined standard gradient or higher, and if it is determined in the driving determination step that the vehicle is not traveling up a slope with a standard gradient or higher, the inspection method is performed by performing the first step and the second step.(Form 9) A power receiving device (80, 180, 280, 380) that receives power from a power transmission device (10, 110) in a non-contact manner, comprising: a power receiving circuit (81) having a power receiving coil (L2) that is magnetically coupled to a power transmission coil (L1) provided by the power transmission device; a load (84) to which the power received by the power receiving coil is supplied; a protection circuit (CRp) having a protection switch (SWp) capable of electrically connecting a first transmission line (TLa) connected to one end (L2a) of the power receiving coil and a second transmission line (TLb) connected to the other end (L2b) of the power receiving coil; a current sensor (71) that detects the current value of the output current flowing from the protection circuit to the load; and a control device (96), wherein the control device, during the period of power reception, performs a first step of electrically connecting the first transmission line and the second transmission line by turning on the protection switch, A power receiving device that, after the first step, performs a second step of determining whether or not there is an abnormality using the detected current of the current sensor. (Embodiment 10) A contactless power supply system (1) comprising a power transmission device (10, 110) and a power receiving device (80, 180, 280, 380), wherein the power transmission device comprises a power transmission coil (L1), the power receiving device comprises a power receiving circuit (81) having a power receiving coil (L2) that is magnetically coupled to the power transmission coil, a load (84) to which power received by the power receiving coil is supplied, a protection circuit (CRp) having a protection switch (SWp) capable of electrically connecting a first transmission line (TLa) connected to one end (L2a) of the power receiving coil and a second transmission line (TLb) connected to the other end (L2b) of the power receiving coil, a current sensor (71) for detecting the current value of the output current flowing from the protection circuit to the load, and a control device (96), wherein the control device performs a first step of electrically connecting the first transmission line and the second transmission line by turning on the protection switch during the period of power reception, A contactless power supply system that, after the first step, performs a second step of determining whether or not there is an abnormality using the detected current of the current sensor.

Claims

1. A method for inspecting a power receiving device (80, 180, 280, 380) that receives power from a power transmitting device (10, 110) in a non-contact manner, wherein the power receiving device comprises: a power receiving circuit (81) having a power receiving coil (L2) that is magnetically coupled to a power transmitting coil (L1) provided by the power transmitting device; a load (84) to which power received by the power receiving coil is supplied; and a protection circuit (CRp) having a protection switch (SWp) that is arranged between the power receiving circuit and the load and electrically connects a first transmission line (TLa) connected to one end (L2a) of the power receiving coil and a second transmission line (TLb) connected to the other end (L2b) of the power receiving coil, wherein the inspection method comprises: a first step of electrically connecting the first transmission line and the second transmission line by turning on the protection switch during the period of power reception; An inspection method comprising: a second step of determining whether there is an abnormality using the current value of the output current flowing from the protection circuit to the load, after the first step.

2. An inspection method according to claim 1, wherein in the second step, an abnormality is determined when the difference between the current value of the input current flowing from the power receiving circuit to the protection circuit and the current value of the output current is smaller than a predetermined first reference value.

3. An inspection method according to claim 1, wherein in the second step, an abnormality is determined if the current value of the output current is greater than a predetermined second reference value.

4. An inspection method according to claim 1, wherein the power transmission device performs an abnormality determination regarding power supply using the current flowing through the power transmission coil and the voltage of the power transmission coil, and the first step and the second step are performed when the power transmission device does not determine an abnormality in the abnormality determination.

5. An inspection method according to claim 1, wherein the power receiving device is mounted on a vehicle (VE), power receiving by the power receiving coil is performed while the vehicle is in motion, and the first step and the second step are performed within a predetermined time from the time when power receiving by the power receiving coil begins.

6. An inspection method according to claim 1, wherein the power receiving device is mounted on a vehicle (VE), power receiving by the power receiving coil is performed while the vehicle is running, the load is a battery, and the method further includes a remaining charge determination step of determining whether the remaining charge of the battery is equal to or greater than a predetermined standard amount, and if it is determined in the remaining charge determination step that the remaining charge of the battery is equal to or greater than the standard amount, the first step and the second step are performed.

7. An inspection method according to claim 1, wherein the power transmission device performs an abnormality determination regarding power supply using the current flowing through the power transmission coil and the voltage of the power transmission coil, the inspection method further comprises: a first transmission step of transmitting a start notification signal to the power transmission device before the first step; and a second transmission step of transmitting a end notification signal to the power transmission device after the second step, wherein the power transmission device does not perform the abnormality determination during the period from when it receives the start notification signal until when it receives the end notification signal.

8. An inspection method according to claim 1, wherein the power receiving device is mounted on a vehicle, power is received by the power receiving coil while the vehicle is in motion, and the inspection method further includes a driving determination step of determining whether the vehicle is traveling up a slope with a predetermined standard gradient or higher, and if it is determined in the driving determination step that the vehicle is not traveling up a slope with a standard gradient or higher, the inspection method is performed by performing the first step and the second step.

9. A power receiving device (80, 180, 280, 380) that receives power from a power transmission device (10, 110) in a non-contact manner, comprising: a power receiving circuit (81) having a power receiving coil (L2) that is magnetically coupled to a power transmission coil (L1) provided by the power transmission device; a load (84) to which the power received by the power receiving coil is supplied; a protection circuit (CRp) having a protection switch (SWp) capable of electrically connecting a first transmission line (TLa) connected to one end (L2a) of the power receiving coil and a second transmission line (TLb) connected to the other end (L2b) of the power receiving coil; a current sensor (71) that detects the current value of the output current flowing from the protection circuit to the load; and a control device (96), wherein the control device, during the period of power reception, performs a first step of electrically connecting the first transmission line and the second transmission line by turning on the protection switch; A power receiving device that, after the first step, performs a second step of determining whether or not there is an abnormality using the detected current of the current sensor.

10. A contactless power supply system (1) comprising power transmission devices (10, 110) and power receiving devices (80, 180, 280, 380), wherein the power transmission device comprises a power transmission coil (L1), the power receiving device comprises a power receiving circuit (81) having a power receiving coil (L2) that is magnetically coupled to the power transmission coil, a load (84) to which power received by the power receiving coil is supplied, a protection circuit (CRp) having a protection switch (SWp) capable of electrically connecting a first transmission line (TLa) connected to one end (L2a) of the power receiving coil and a second transmission line (TLb) connected to the other end (L2b) of the power receiving coil, a current sensor (71) for detecting the current value of the output current flowing from the protection circuit to the load, and a control device (96), wherein the control device performs a first step of electrically connecting the first transmission line and the second transmission line by turning on the protection switch during the period of power reception, A contactless power supply system that, after the first step, performs a second step of determining whether or not there is an abnormality using the detected current of the current sensor.

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