In-vehicle power receiver with check of short-circuit function and wireless power transfer system

Abstract

A in-vehicle power receiver (100) includes a rectifier circuit (200) that functions as a protection circuit to short-circuit a power receiver coil (110) and cut off power supply from the power receiver coil, a voltage sensor (330), and a power-receiver controller (231) that implements short-circuit control using the rectifier circuit when a detected voltage of the voltage sensor is greater than or equal to a determination threshold. The determination threshold is changeable, and the power-receiver controller decreases the determination threshold and determines whether the short-circuit control is executed normally when main switches (301H, 301L) are turned on and voltage is applied from a high-voltage storage battery (300) to the power receiver before power supply from a power transmitter coil.

Description

IN-VEHICLE POWER RECEIVER WITH CHECK OF SHORT-CIRCUIT FUNCTION AND WIRELESS POWER TRANSFER SYSTEMCross Reference

[0001] This application is based on Japanese Patent Application No. 2024-168826 filed on September 27, 2024, the contents of which are incorporated herein by reference.

[0002] The present disclosure relates to an in-vehicle power receiver and a wireless power transfer system.

[0003] Patent Literature 1 discloses a system for executing wireless power transfer from a ground-based power transmitter to a power receiver installed in an electric vehicle. The power transmitter includes a power transmitter coil and a controller that energizes the power transmitter coil. The power receiver includes a power receiver coil that is supplied with power wirelessly from the power transmitter coil.

[0004] The power transmitter and the power receiver include communication coils for narrow area wireless communication. The power receiver supplies a power supply request signal to the communication coil of the power receiver. The power transmitter determines whether there is a power supply request based on an output signal from the communication coil of the power transmitter. When the power transmitter determines that there is a power supply request, the power transmitter energizes the power transmitter coil.

[0005] Patent Literature 1: JP 2024-008088 A

[0006] Controls and circuits to check whether a protection circuit of the power receiver is in normal operation before supplying power can be complex.

[0007] The main purpose of the present disclosure is to provide an in-vehicle power receiver and a wireless power transfer system that can check whether a protection circuit of the power receiver is in normal operation before supplying power, using a simple configuration.

[0008] According to an aspect of the present disclosure, an in-vehicle power receiver is connected to a power storage unit through a power switch. The in-vehicle power receiver includes a power receiver coil, a protection circuit, a state detection unit, and a power-receiver controller. The power receiver coil is configured to wirelessly receive power supply from a power transmitter coil of a power transmitter. The protection circuit is configured to short one of paths from the power receiver coil to the power storage unit to cut off power supply from the power receiver coil. The state detection unit is configured to detect a physical quantity indicative of a state of the in-vehicle power receiver or the power storage unit. The power-receiver controller is configured to execute short-circuit control using the protection circuit when the physical quantity detected by the state detection unit is greater than or equal to a determination threshold. The determination threshold is changeable. The power-receiver controller is configured to decrease the determination threshold and determine whether the short-circuit control is normally executed based on the determination threshold when the power switch is turned on and voltage is applied from the power storage unit to the power receiver before power transmission from the power transmitter coil.

[0009] Accordingly, by simply changing the decision threshold, a mechanism used during the power supply from the power transmitter coil is utilized. Therefore, it can be checked whether the protection circuit of the power receiver operates normally before the power supply, using a simple configuration.

[0010] According to an aspect of the present disclosure, a wireless power transfer system includes a power transmitter having a power transmitter coil, and an in-vehicle power receiver having a power receiver coil and mounted on a vehicle. The power transmitter coil is configured to wirelessly supply power to the power receiver coil. The in-vehicle power receiver is connected to a power storage unit through a power switch. The in-vehicle power receiver includes a protection circuit, a state detection unit, and a power-receiver controller. The protection circuit is configured to short one of paths from the power receiver coil to the power storage unit to cut off power supply from the power receiver coil. The state detection unit is configured to detect a physical quantity indicative of a state of the in-vehicle power receiver or the power storage unit. The power-receiver controller is configured to execute short-circuit control using the protection circuit when the physical quantity detected by the state detection unit is greater than or equal to a determination threshold. The determination threshold is changeable. The power-receiver controller is configured to decrease the determination threshold and determine whether the short-circuit control is normally executed based on the determination threshold when the power switch is turned on and voltage is applied from the power storage unit to the power receiver before power transmission from the power transmitter coil.

[0011] Accordingly, by simply changing the decision threshold, a mechanism used during the power supply from the power transmitter coil is utilized. Therefore, it can be checked whether the protection circuit of the power receiver operates normally before the power supply, using a simple configuration.

[0012] The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure.FIG. 1 is an overall configuration diagram of a wireless power transfer system according to a first embodiment.FIG. 2 is an overall configuration diagram of the wireless power transfer system.FIG. 3 is a diagram illustrating a power transmitter and a power receiver.FIG. 4 is a diagram illustrating an electrical circuit of the power receiver.FIG. 5 is a flowchart illustrating a flow a protection process.FIG. 6 is a diagram illustrating an electric circuit of a power receiver according to a second embodiment.FIG. 7 is a flowchart illustrating a flow of a protection process according to a third embodiment.FIG. 8 is a diagram illustrating a protection circuit according to a modification.FIG. 9 is a diagram illustrating a protection circuit according to a modification.FIG. 10 is a diagram illustrating a protection circuit according to a modification.FIG. 11 is a diagram illustrating a protection circuit according to a modification.FIG. 12 is a diagram illustrating a protection circuit according to a modification.FIG. 13 is a diagram illustrating a protection circuit according to a modification.FIG. 14 is a diagram illustrating a protection circuit according to a modification.

[0013] Multiple embodiments will be described with reference to the drawings. In the embodiments, parts that functionally and / or structurally correspond to or are associated with each other may be assigned the same reference numeral, or reference numerals different in digit in the hundreds or higher place. The corresponding and / or associated parts may refer to the explanation in the other embodiments.

[0014] First Embodiment A first embodiment of a wireless power transfer system of the present disclosure will be described below with reference to the drawings.

[0015] First, an overall configuration of the wireless power transfer system will be described. As shown in FIGS. 1, 2, and 3, the wireless power transfer system 10 includes a power transmitter 20 and a power receiver 100 (corresponding to "in-vehicle power receiver"). The power receiver 100 is mounted on a vehicle 11 as a moving object that travels on a road RS. The vehicle 11 is, for example, an electric automobile or a hybrid vehicle. The power is supplied from the power transmitter 20 to the power receiver 100 while the vehicle 11 is travelling or stopped. The wireless power transfer system 10 executes wireless power transfer from the power transmitter 20 to the power receiver 100 through magnetic field resonance coupling (magnetic field resonance). The wireless power transfer system 10 is also referred to as a dynamic wireless power transfer (D-WPT) system.

[0016] The power transmitter 20 has a power-transmitter coil unit 21 and a power-transmitter power supply unit 51 that supplies power to the power-transmitter coil unit 21. The power-transmitter coil unit 21 is buried in the road RS. The power-transmitter power supply unit 51 is installed, for example, on the side of the road RS. The power-transmitter coil unit 21 is connected to the power-transmitter power supply unit 51. The power-transmitter power supply unit 51 is connected to an AC power source 15 and supplies AC (alternating-current) power from the AC power source 15 to the power-transmitter coil unit 21. The AC power source 15 is, for example, a commercial power source. Multiple power-transmitter coil units 21 are arranged along the lanes of the road RS. FIG. 2 shows an example of four power-transmitter coil units 21 aligned along the road RS and connected to one power-transmitter power supply unit 51. In other words, one power-transmitter power supply unit 51 is provided for each of the four power-transmitter coil units 21.

[0017] The configuration is not limited to one power-transmitter power supply unit 51 for each of the multiple power-transmitter coil units 21, but one power-transmitter power supply unit 51 may be provided for each power-transmitter coil unit 21.

[0018] The power-transmitter power supply unit 51 includes a PFC (Power Factor Correction) circuit 61, an inverter 60, and a filter circuit 52. The PFC circuit 61 includes an AC / DC converter and is connected to the AC power source 15. The PFC circuit 61 includes switching elements (e.g., IGBTs or MOSFETs) that are switched and controlled to convert the input AC power to DC (direct current) power and improve a power factor of the AC power input from the AC power source 15.

[0019] The inverter 60 is connected to the PFC circuit 61. The inverter 60 includes switching elements (e.g., IGBTs or MOSFETs) that are switched and controlled to convert the DC power input from the PFC circuit 61 to AC power.

[0020] The filter circuit 52 removes noise contained in the AC current input from the inverter 60 and supplies the AC current from which noise has been removed to the power-transmitter coil unit 21. The filter circuit 52 is, for example, an LC filter that includes a coil and a capacitor. Circuits having various configurations can be used as the filter circuit 52, and, for example, a T-type filter circuit is used as the filter circuit 52.

[0021] The power-transmitter coil unit 21 includes a power transmitter coil 22, a power-transmitter resonant circuit 30, and a power-transmitter communication coil 40. The power-transmitter resonant circuit 30 supplies the AC power supplied by the filter circuit 52 to the power transmitter coil 22.

[0022] The power receiver 100 includes a power-receiver coil unit 101 and a power-receiver power supply unit 181. The power-receiver coil unit 101 includes a power receiver coil 110. The power-receiver coil unit 101 is located at the bottom of the vehicle body of the vehicle 11. When the vehicle 11 travels on the road RS where the power transmitter coil 22 is buried, the power transmitter coil 22 on the ground side and the power receiver coil 110 of the vehicle 11 face each other in the vertical direction.

[0023] The power receiver 100 includes a power-receiver resonant circuit 140. The power receiver coil 110 is connected to the power-receiver resonant circuit 140. The power receiver coil 110 is supplied with power from the power transmitter coil 22. The power receiver coil 110 supplies the received power to the power-receiver resonant circuit 140.

[0024] The power-receiver power supply unit 181 of the power receiver 100 includes a filter circuit 182 and a rectifier circuit 200 that also functions as a "protection circuit." In this embodiment, the rectifier circuit 200 corresponds to a "protection circuit." Additionally, the protection circuit can also be provided by connecting semiconductor switches to both ends of the power receiver coil 110 or to an input of the rectifier circuit 200, and turning these switches on, instead of using the rectifier circuit 200.

[0025] The configurations of the power-receiver resonant circuit 140, the filter circuit 182, and the rectifier circuit 200 will be described. As shown in FIG. 4, the power-receiver resonant circuit 140 includes a first resonant capacitor 141 and a second resonant capacitor 142. The power-receiver resonant circuit 140 is not limited to the circuit shown in FIG. 4, but various circuits can be employed.

[0026] The rectifier circuit 200 is a full bridge circuit and includes a first upper arm switch QH1, a first lower arm switch QL1, a second upper arm switch QH2, and a second lower arm switch QL2. In this embodiment, each switch QH1, QL1, QH2, QL2 is a semiconductor switching device, and specifically, is an N-channel MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor). Each switch QH1, QL1, QH2, QL2 has a body diode DH1, DL1, DH2, DL2.

[0027] The rectifier circuit 200 may includes an IGBT (Insulated Gate Bipolar Transistor) instead of the N-channel MOSFET. In this case, a freewheel diode may be connected in inverse parallel to the IGBT.

[0028] The source of the first upper arm switch QH1, which is the low potential terminal of the first upper arm switch QH1, and the drain of the first lower arm switch QL1, which is the high potential terminal of the first lower arm switch QL1, are connected to one end of the first resonant capacitor 141. The other end of the first resonant capacitor 141 is connected to a first end of the power receiver coil 110. The source of the second upper arm switch QH2 and the drain of the second lower arm switch QL2 are connected to one end of the second resonant capacitor 142. The second resonant capacitor 142 is connected to a second end of the power receiver coil 110. The drains of the first and second upper arm switches QH1, QH2 are connected to a high potential path H1, and the sources of the first and second lower arm switches QL1, QL2 are connected to a low potential path L1.

[0029] The filter circuit 182 removes noise contained in the current input from the rectifier circuit 200 and supplies the current from which noise has been removed toward a high-voltage storage battery 300. The filter circuit 182 is an LC filter (low-pass filter) that includes a reactor 183 and a capacitor 185. The filter circuit 182 is not limited to the circuit shown in FIG. 4, but various circuits can be employed.

[0030] The power receiver 100 includes a smoothing capacitor 210 between the filter circuit 182 and the high-voltage storage battery 300. One end of the smoothing capacitor 210 is connected to the high potential path H1, and the other end of the smoothing capacitor 210 is connected to the low potential path L1.

[0031] The vehicle 11 includes a high potential main switch 301H, a low potential main switch 301L, and a high-voltage storage battery 300 as a power storage unit. The high potential main switch 301H and the low potential main switch 301L are, for example, relays (specifically, mechanical relays). A positive terminal of the high-voltage storage battery 300 is connected to the high potential path H1 via a high potential main switch 301H. A negative terminal of the high-voltage storage battery 300 is connected to the low potential path L1 via a low potential main switch 301L. The high-voltage storage battery 300 is a secondary battery that can be charged and discharged and has a rated voltage of several hundred volts, for example. The high-voltage storage battery 300 is, for example, a lithium-ion storage battery or a nickel-metal hydride storage battery. The high potential main switch 301H and the low potential main switch 301L correspond to a "power switch".

[0032] The vehicle 11 includes a travelling inverter 310 and a rotary electric machine 320. The travelling inverter 310 is a 3-phase inverter and is connected to the high-voltage storage battery 300 via the high potential main switch 301H and the low potential main switch 301L. The armature windings of the rotary electric machine 320 are connected to the upper and lower arm switches that constitute the travelling inverter 310. By switching control of the upper and lower arm switches of the travelling inverter 310 while the high potential main switch 301H and the low potential main switch 301L are turned on, the travelling inverter 310 converts the DC power supplied from the high-voltage storage battery 300 into AC power and supplies it to the armature winding. This causes the rotor of the rotary electric machine 320 to rotate, and the rotational power of the rotor rotates drive wheels of the vehicle 11. As a result, the vehicle 11 travels.

[0033] As shown in FIG. 3, the power-transmitter power supply unit 51, which constitutes the power transmitter 20, includes a power-transmitter control unit 70. The power-transmitter control unit 70 includes a power-transmitter controller 71. The power-transmitter controller 71 is an electronic control unit (ECU) that executes various controls of the power transmitters 20 and includes a processor as hardware, a storage unit, and a communication bus connecting the processor and storage unit.

[0034] The storage unit includes a memory and a storage as hardware. The memory is a storage device for storing data used in the processing of the power-transmitter controller 71. The memory, for example, provides the processor with a work area for temporary use when the processor performs processing. The memory includes, for example, RAM and ROM. The storage is a storage device that stores various programs and data to be read and executed by the processor and is a non-transitory tangible storage medium. The storage includes, for example, HDD or flash memory. The storage contains program information and other information for various processes.

[0035] For example, the program information stored on the non-transitory tangible storage medium is installed in the storage unit. The storage medium is, for example, a USB memory, CD-ROM or DVD. In addition, the program information transmitted over a communication network, such as OTA (Over The Air), for example, is installed in the storage unit.

[0036] The power-receiver power supply unit 181, which constitutes the power receiver 100, includes a power-receiver controller 231. The power-receiver controller 231 is an ECU that executes various controls of the power receiver 100, and as shown in FIG. 4, includes a processor 232 as hardware, a storage unit 233, and a communication bus 234 that connects the processor 232 and storage unit 233.

[0037] The storage unit 233 includes a memory and a storage as hardware. The memory is a storage device for storing data used in the processing of the power-receiver controller 231. The memory, for example, provides the processor 232 with a work area for temporary use when the processor 232 performs processing. The memory includes, for example, RAM and ROM. The storage is a storage device that stores various programs and data to be read and executed by the processor 232 and is a non-transitory tangible storage medium. The storage includes, for example, HDD or flash memory. The storage contains program information and other information for various processes.

[0038] For example, the program information stored on the non-transitory tangible storage medium is installed in the storage unit 233. The storage medium is, for example, a USB memory, CD-ROM or DVD. In addition, the program information transmitted over a communication network, such as OTA (Over The Air), for example, is installed in the storage unit 233.

[0039] The power-transmitter controller 71 executes a switching control of the PFC circuit 61 and a switching control of the inverter 60. Through the switching control of the inverter 60, a high-frequency AC voltage is applied to the power transmitter coil 22. This causes a high-frequency current to flow in the power transmitter coils 22 and a magnetic field for power transmission is generated in the power transmitter coils 22.

[0040] In this embodiment, the power-transmitter controller 71 switches and controls the inverter 60 so that the frequency of the high-frequency voltage applied to the power transmitter coil 22 is becomes a first specified frequency between 10 kHz and 100 GHz, specifically, 85 kHz. The resonant frequencies of the power-transmitter resonant circuit 30 and the power-receiver resonant circuit 140 are set at the same frequency or close to the first specified frequency.

[0041] When the magnetic field generated in the power transmitter coil 22 links with the power receiver coil 110 of the vehicle 11, a high-frequency current flows in the power receiver coil 110, varying with the frequency of the high-frequency current flowing in the power transmitter coil 22. The high-frequency current flowing in the power transmitter coil 22 is supplied to the rectifier circuit 200 through the power-receiver resonant circuit 140.

[0042] The power-receiver controller 231 converts the supplied AC current into DC current by executing switching control (i.e., synchronous rectification control) of each of the switches QH1, QL1, QH2, and QL2 and outputs it.

[0043] While the high potential main switch 301H and the low potential main switch 301L are turned on, the output current of the rectifier circuit 200 is supplied to the high-voltage storage battery 300 or the travelling inverter 310 through the filter circuit 182.

[0044] The high potential main switch 301H and the low potential main switch 301L can actually be controlled by a different controller than the power-receiver controller 231. For convenience, however, the high potential main switch 301H and the low potential main switch 301L are controlled by the power-receiver controller 231.

[0045] The vehicle 11 includes a low-voltage storage battery 302. The rated voltage of the low-voltage storage battery 302 is lower than the rated voltage of the high-voltage storage battery 300, and is, for example, 12V. The low-voltage storage battery 302 is, for example, a lead-acid battery. The power supplied from the low-voltage storage battery 302 to the power-receiver controller 231 enables the power-receiver controller 231 to operate.

[0046] The vehicle 11 includes a voltage sensor 330, a current sensor 340, and a temperature sensor 350. A voltage sensor detects voltages of various in-vehicle devices of the vehicle 11 (specifically, components of the power receiver 100), and the voltage sensor 330 of the present embodiment detects, for example, a voltage between terminals of the smoothing capacitor 210. A current sensor detects currents flowing in various in-vehicle devices of the vehicle 11 (specifically, the components of the power receiver 100). The current sensor 340 of the present embodiment detects a current flowing through an electrical path H2 between the low-voltage storage battery 302 and an isolated power supply 360 which will be described later. A temperature sensor detects temperatures of the various in-vehicle devices of the vehicle 11 (specifically, components of the power receiver 100), and the temperature sensor 350 of the present embodiment detects, for example, temperatures of the smoothing capacitor 210 and the rectifier circuit 200. The detected values of each sensor 330, 340, 350 are input to the power-receiver controller 231.

[0047] The power receiver 100 and the power transmitter 20 each have a configuration for communication between the power receiver 100 and the power transmitter 20. In detail, the power-receiver coil unit 101, which constitutes the power receiver 100, includes a power-receiver communication coil 170. A power-receiver control unit 230 includes a signal transmitter 240.

[0048] The power-transmitter coil unit 21, which constitutes the power transmitter 20, includes the power-transmitter communication coil 40. The power-transmitter control unit 70 includes a signal receiver 80. The power-receiver communication coil 170 and the power-transmitter communication coil 40 are communication coils for narrow area wireless communication. Narrow area wireless communications are those with a communication distance of less than 10 meters (e.g., 2-3 meters). Narrow area wireless communication is a communication with a shorter communication distance than wide area wireless communication.

[0049] Various short-range wireless communications can be used as the narrow area wireless communication. For example, communications compliant with any communication standards established by IEEE, ISO, and IEC can be used. Specifically, for example, Wi-Fi (registered trademark), Bluetooth (registered trademark), ZigBee (registered trademark), RFID (Radio Frequency Identification), or DSRC (Dedicated Short Range Communication) can used as the narrow area wireless communication.

[0050] The signal transmitter 240 is connected to the power-receiver controller 231. The signal transmitter 240 is connected to the power-receiver communication coil 170. The power-receiver controller 231 controls the signal transmitter 240 to supply a power supply request signal to the power-receiver communication coil 170. The power supply request signal is a signal requesting the power transmitter coil 22 near the vehicle 11 to transmit power to the power receiver coil 110.

[0051] The power-receiver control unit 230 controls the signal transmitter 240 to supply a single frame to the power-receiver communication coil 170, and the single frame includes the power supply request signal, ID information of the vehicle 11, and a requested power Weq that is a requested value of the power supply to the vehicle 11. This control causes a high-frequency voltage to be applied from the signal transmitter 240 to the power-receiver communication coil 170. Consequently, a high-frequency current flows in the power-receiver communication coil 170, and a magnetic field for information communication is generated in the power-receiver communication coil 170.

[0052] When the power-receiver coil unit 101 of the vehicle 11 approaches the power-transmitter coil unit 21 on the ground side, the generated magnetic field links to the power-transmitter communication coil 40, and a high-frequency current flows through the power-transmitter communication coil 40. This high-frequency current is input to the signal receiver 80. The signal receiver 80 recognizes the presence or absence of a power supply request and ID information based on the input signal from the power-transmitter communication coil 40. The signal receiver 80 also acquires the required power Weq for the vehicle 11 with the recognized ID information, based on the signal from the power-transmitter communication coil 40. The information recognized by the signal receiver 80 and the requested power Weq are input to the power-transmitter controller 71.

[0053] In this embodiment, the power-receiver controller 231 controls the signal transmitter 240 so that the frequency of the high-frequency voltage applied to the power-receiver communication coil 170 becomes a second specified frequency between 10 kHz and 100 GHz. In this embodiment, the second specified frequency is a frequency that deviates from the first specified frequency above, specifically a frequency higher than the first specified frequency (e.g., 13.56 MHz).

[0054] When the power-transmitter controller 71 determines that there is a power supply request based on input information from the signal receiver 80, the power-transmitter controller 71 applies high-frequency voltage to the power transmitter coil 22 by controlling the inverter 60 and the PFC circuit 61. This results in a wireless power transmission from the power transmitter coil 22 to the power receiver coil 110.

[0055] The rectifier circuit 200 of this embodiment functions as a protection circuit that shorts the power receiver coil 110 and cuts off the supply of power from the power receiver coil 110 to the high-voltage storage battery 300 if an abnormality occurs in the power receiver 100. This function as a protection circuit can prevent, for example, an overvoltage from being applied to the high-voltage storage battery 300 or the travelling inverter 310. For this reason, before supplying power, it is desirable to check whether the rectifier circuit 200 functions normally as a protection circuit. In the present disclosure, an event resembling an overvoltage for the operation check of the rectifier circuit 200 is artificially created, but an actual overvoltage event does not occur.

[0056] The operation check of the rectifier circuit 200, i.e., checking whether each switch QH1, QL1, QH2, QL2 is turned on or off based on a command, can be performed, for example, by detecting the current flowing through each switch QH1, QL1, QH2, QL2.

[0057] However, since the rectifier circuit 200 is arranged in a high voltage region, the current sensors that detect the currents flowing through the switches QH1, QL1, QH2, QL2 are arranged in the high voltage region. On the other hand, a determination device (determination circuit) determines whether the switches are turned on and off normally based on the detected current, and the determination device is, for example, the power-receiver controller 231 which receives power from the low-voltage storage battery 302 and operates with a low-voltage current. Thus, signals from the current sensors of the switches QH1, QL1, QH2, QL2 installed in the high voltage region are necessary to be input to the determination device provided in a low voltage region via an insulating circuit (e.g., photocoupler). In this case, there are problems in that the number of parts increases, and the circuit structure becomes complicated. Another problem is that the control and configuration for forcibly executing short-circuit control when performing the operation check is also becoming more complex.

[0058] Therefore, in this embodiment, the power receiver 100 is configured so that the operation of the rectifier circuit 200 can be checked based on the results detected in the low voltage region using simple mechanism. This will be described below in detail.

[0059] As shown in FIG. 4, in the power receiver 100, the power-receiver controller 231 is disposed in the low voltage region where a low voltage current flows, which is lower than a high voltage current. On the other hand, in the power receiver 100, the power receiver coil 110, the power-receiver resonant circuit 140, the filter circuit 182, and the rectifier circuit 200 are arranged in the high voltage region where the high voltage current flows. The high-voltage storage battery 300 is also disposed in the high voltage region. Furthermore, the voltage sensor 330 is disposed in the high voltage region, and inputs a detected voltage acquired in the high voltage region to the power-receiver controller 231 in the low voltage region via an interface unit (not shown). The interface unit has a function of transmitting signals between the high voltage region and the low voltage region while electrically insulating these systems, and is, for example, a photocoupler.

[0060] Similarly, drive circuits 370 for the switches QH1, QL1, QH2, QL2 of the rectifier circuit 200 are also arranged in the high voltage region. More specifically, the drive circuits 370 are provided individually corresponding to the respective switches QH1, QL1, QH2, QL2. In FIG. 4, they are all expressed as one box. The drive circuits 370 receive a switching command from the power-receiver controller 231, and drives the switches QH1, QL1, QH2, QL2 based on the received switching command.

[0061] Specifically, the power-receiver controller 231 generates the switching command to turn on and off the switches QH1, QL1, QH2, QL2, and outputs the command to the drive circuits 370 of the switches QH1, QL1, QH2, QL2 via the above-described interface unit.

[0062] When a drive circuit 370 determines that the switching command is an ON command, the drive circuit 370 supplies a charging current to a gate of a switch QH1, QL1, QH2, QL2 with a power supply voltage VCC that is an output voltage of the isolated power supply 360. As a result, the gate voltage of the switch QH1, QL1, QH2, QL2 become equal to or higher than a threshold voltage Vth, and the switch QH1, QL1, QH2, QL2 is turned on. The threshold voltage Vth is lower than the power supply voltage VCC.

[0063] The isolated power supply 360 that supplies power to the drive circuits 370 is disposed across the high voltage region and low voltage region. The isolated power supply 360 is a switching power supply (isolated DC-DC converter) that transforms a voltage inputted from the low-voltage storage battery 302 and outputs the transformed voltage to the drive circuits 370. The isolated power supply 360 may be controlled by the power-receiver controller 231, for example.

[0064] As described above, when the switching command is an ON command, the drive circuits 370 supply a charging current to the gates of the switches QH1, QL1, QH2, QL2. Therefore, when the switches QH1, QL1, QH2, QL2 are turned on, the amount of current supplied from the isolated power supply 360 to the drive circuits 370 also increases. Accordingly, when the switches QH1, QL1, QH2, QL2 are turned on, the amount of current supplied from the low-voltage storage battery 302 to the isolated power supply 360 also increases. That is, the power consumption increases. The more the switches QH1, QL1, QH2, QL2 are turned on, the greater the amount of current.

[0065] Therefore, the current sensor 340 is provided in an electrical path H2 between the low-voltage storage battery 302 and the isolated power supply 360 to detect the amount of current flowing from the low-voltage storage battery 302 to the isolated power supply 360. The electrical path H2 and the current sensor 340 are disposed in the low voltage region. The power-receiver controller 231 has a function of determining whether the rectifier circuit 200 is operating normally as a protection circuit, based on the current detected by the current sensor 340.

[0066] Next, various functions provided by the power-receiver controller 231 will be described. The power-receiver controller 231 includes a function as a determination unit 235, a function as a short-circuit control unit 236, and a function as a threshold setting unit 237. These functions are realized by the processor 232 implementing the program stored in the storage unit. The ability of the threshold setting unit 237 to change the threshold value offers the advantage of setting an optimal overvoltage threshold for each vehicle type. Since the threshold can be easily changed, a single design can be used for many car models and costs can be reduced. The threshold setting unit 237 may be realized by a digital-to-analog converter (DAC).

[0067] The short-circuit control unit 236 acquires a physical quantity indicating the state of the power receiver 100, determines whether to execute the short-circuit control based on whether said physical quantity is above a determination threshold, and controls the rectifier circuit 200 to execute the short-circuit control when the short-circuit control is determined to be executed.

[0068] In the present embodiment, the voltage sensor 330 detects a voltage in the high potential path H1 (i.e., a voltage between the terminals of the smoothing capacitor 210) as said physical quantity and inputs it to the power-receiver controller 231. Then, the short-circuit control unit 236 of the power-receiver controller 231 determines whether the input (acquired) voltage is greater than or equal to the predetermined determination threshold. When the determination result is affirmative, the short-circuit control unit 236 turns on the lower arm switches QL1 and QL2 to implement the short-circuit control. The determination threshold is set by the threshold setting unit 237 described below. The determination threshold is, for example, predetermined based on specifications of a battery serving as a load and the maximum voltage of other devices connected to the load, taking into account design margins and other factors.

[0069] The threshold setting unit 237 adjusts and sets the determination threshold depending on whether it is before power supply from the power transmitter coil 22. In detail, the threshold setting unit 237 sets a first determination threshold when it is not before the power supply (i.e., when the power is being supplied). The first determination threshold is a value (voltage value) that is sufficient to determine that an overvoltage is applied to the power receiver 100 or the high-voltage storage battery 300. In other words, the first determination threshold is a value that exceeds the rated voltage (or withstand voltage) of each component (rectifier circuit 200, smoothing capacitor 210, etc.) constituting the power receiver 100 or the rated voltage of the high-voltage storage battery 300. The first determination threshold is an appropriate value determined by experiment or other means and stored in advance in the storage unit. When it is not before the power supply, the threshold setting unit 237 reads the first determination threshold from the storage unit and notifies the short-circuit control unit 236.

[0070] On the other hand, the threshold setting unit 237 sets a second determination threshold when it is before the power supply. The second determination threshold is smaller than the first determination threshold, and is a value (voltage value) at which an overvoltage cannot be determined to be applied. Specifically, the second determination threshold is smaller than the voltage (rated voltage) that can be applied by the high-voltage storage battery 300, and is an appropriate value determined by experiment or other means and stored in the storage unit in advance. In this embodiment, when the high potential main switch 301H and the low potential main switch 301L are turned on, the high-voltage storage battery 300 is connected to the power receiver 100, and the voltage of the high-voltage storage battery 300 is applied to the power receiver 100, a value smaller than the detected voltage by the voltage sensor 330 is set as the second determination threshold. When it is before the power supply, the threshold setting unit 237 reads the second determination threshold from the storage unit and notifies the short-circuit control unit 236.

[0071] While the rectifier circuit 200 is executing short-circuit control to short-circuit the power receiver coil 110, the determination unit 235 acquires the detected current from the current sensor 340. When the detected current is greater than a predetermined current threshold, the determination unit 235 determines that the rectifier circuit 200 is operating normally as a protection circuit. When the detected current is equal to or less than the current threshold, the determination unit 235 determines that there is an abnormality.

[0072] Next, a flow of a protection process using the rectifier circuit 200 will be described with reference to FIG. 5. The protection process is executed by the power-receiver controller 231 at predetermined intervals after the power receiver 100 is started (for example, after the ignition switch is turned on).

[0073] When starting the protection process, the power-receiver controller 231 determines whether it is before the power supply (step S101). For example, when narrow area wireless communication cannot be established between the power-receiver communication coil 170 and the power-transmitter communication coil 40, the power-receiver controller 231 may determine that it is before the power supply.

[0074] When the determination result is affirmative, the threshold setting unit 237 of the power-receiver controller 231 sets the second determination threshold (step S102). When the determination result is negative, the threshold setting unit 237 sets the first determination threshold (step S103). Then, the short-circuit control unit 236 of the power-receiver controller 231 causes the voltage sensor 330 to detect the voltage applied to the smoothing capacitor 210 and acquires the detected voltage from the voltage sensor 330 (step S104).

[0075] Next, the short-circuit control unit 236 of the power-receiver controller 231 determines whether the acquired detected voltage is greater than or equal to the determination threshold set in step S102 or step S103 (step S105). When the determination result in step S105 is negative, the power-receiver controller 231 ends the protection process.

[0076] When the determination result in step S105 is affirmative, the power-receiver controller 231 executes the short-circuit control to short circuit the power receiver coil 110 by the rectifier circuit 200 (step S106). In step S106, the power-receiver controller 231 turns off the upper arm switches QH1 and QH2 and turns on the lower arm switches QL1 and QL2. As a result, the first end and the second end of the power receiver coil 110 are connected to each other, and a current flows through a path indicated by the dashed line in FIG. 4.

[0077] Next, the power-receiver controller 231 acquires a detected current from the current sensor 340 (step S107). That is, the current sensor 340 detects the amount of current supplied from the low-voltage storage battery 302 to the isolated power supply 360, and the power-receiver controller 231 acquires the detected current. In this embodiment, the current sensor 340 corresponds to a "detection unit" that detects a current supplied to the isolated power supply 360.

[0078] Then, the determination unit 235 of the power-receiver controller 231 determines whether the detected current is greater than a predetermined current threshold (step S108). When the result of this determination is affirmative, the power-receiver controller 231 determines that the rectifier circuit 200 is functioning normally as a protection circuit (step S109). Then, the protection process ends. On the other hand, when the determination result in step S108 is negative, the power-receiver controller 231 determines that an abnormality has occurred (step S110). That is, the power-receiver controller 231 determines that the rectifier circuit 200 is not functioning normally as a protection circuit. When it is determined that an abnormality has occurred, the power-receiver controller 231 notifies an external device, such as a higher level ECU or the like, of that fact.

[0079] The power receiver 100 according to the present embodiment provides the following effects.

[0080] When it is before power is transmitted from the power transmitter coil 22, the high potential main switch 301H and the low potential main switch 301L are turned on, and voltage is applied from the high-voltage storage battery 300 to the power receiver 100, the power-receiver controller 231 sets the second determination threshold. The second determination threshold value is smaller than the first determination threshold value used at the time of power supply from the power transmitter coil 22. The first determination threshold is a value for detecting overvoltage, while the second determination threshold is a value lower than the first determination threshold and for detecting normal voltage (non-overvoltage) applied from the high-voltage storage battery 300. When the detected voltage becomes equal to or greater than the determination threshold, the power-receiver controller 231 implements short-circuit control, and during said short-circuit control, it determines whether the short-circuit control is being normally executed.

[0081] According to this, during the power supply, the power-receiver controller 231 determines whether the short-circuit control executed based on detecting an overvoltage (i.e., an abnormality of the power receiver 100) is normal. Before the power supply, the power-receiver controller 231 intentionally executes the short-circuit control by utilizing the mechanism for detecting overvoltage during the power supply, even if there is no overvoltage, triggered by the high-voltage storage battery 300 and the power receiver 100 being energized. Then, the power-receiver controller 231 can determine whether the short-circuit control is being executed normally during the short-circuit control. Therefore, no special mechanism is required to determine whether the short-circuit control is normally executed before the power supply, and the operation of the short-circuit control can be checked with a simple configuration. In other words, an overvoltage condition can be emulated with a simple configuration, and it can be checked whether the protection circuit of the power receiver operates normally, without actually having an overvoltage incident.

[0082] The current sensor 340 arranged in the low voltage region detects the current supplied to the isolated power supply 360, and the determination unit 235 of the power-receiver controller 231 determines whether the rectifier circuit 200 is functioning normally as a protection circuit based on the detected current from the current sensor 340. Since the current sensor 340 and the power-receiver controller 231 are both arranged in the low voltage region, an insulating circuit such as the interface unit is not required between the current sensor 340 and the power-receiver controller 231, and the number of components can be reduced.

[0083] The isolated power supply 360 is an isolated DC-DC converter that supplies a charging current (i.e., driving power) to the gates of the switches QH1, QL1, QH2, and QL2 via the drive circuits 370. Since no current is flowing in order to perform the operation check of the rectifier circuit 200, the current consumption associated with the determination can be reduced.

[0084] The current supplied to the isolated power supply 360 is proportional to the number of switches QH1, QL1, QH2, and QL2 that are turned on. Therefore, the determination unit 235 can determine whether the switches QH1, QL1, QH2, QL2 of the rectifier circuit 200 are functioning normally based on whether the detected current is larger than the current threshold.

[0085] Modification of First Embodiment In the above embodiment, an arbitrary method may be adopted for determining whether it is before power is supplied from the power transmitter coil 22. For example, the position information of the vehicle 11 may be obtained using a GPS or the like, and the position information (e.g., location information of a power supply lane) where the power-transmitter coil unit 21 is buried may be obtained from map information or the like. These two positions may be compared to determine whether it is before power supply from the power transmitter coil 22. It may also be determined by detecting the position information of the power transmitter 20 through narrow area wireless communication between the power-receiver communication coil 170 and the power-transmitter communication coil 40, and comparing the detected position information of the power transmitter 20 with that of the vehicle 11. The power-receiver controller 231 may use wide area wireless communication to acquire location information on where the power-transmitter coil unit 21 is buried and compare it with the location information of the vehicle 11 to determine whether it is before the power supply.

[0086] In the above embodiment, when an abnormality of the rectifier circuit 200 is detected before the power supply, that is, when the processing of step S110 is executed based on the second determination threshold being set, the power-receiver controller 231 may regulate power transmission from the power transmitter 20 thereafter. As a result, safety can be ensured.

[0087] In the above embodiment, the execution of the short-circuit control is determined based on the detected voltage (voltage between the terminals of the smoothing capacitor 210) obtained from voltage sensor 330, but the execution of the short-circuit control may be determined based on physical quantities other than voltage that indicate the state of the power receiver 100 or the high-voltage storage battery 300.

[0088] For example, the current flowing in the high potential path H1, the low potential path L1, the high potential main switch 301H, the low potential main switch 301L, the high-voltage storage battery 300, etc., is detected by a current sensor, and the power-receiver controller 231 may determine the execution of the short-circuit control based on said detected current, that is, on a comparison of the detected current and a determination threshold. In this case, the first determination threshold may be a value for detecting overcurrent, and the second determination threshold may be a value smaller than the first determination threshold and less than the appropriate current value. In other words, the second determination threshold may be smaller than the current that flows from the high-voltage storage battery 300 to the smoothing capacitor 210, etc. of the power receiver 100 when the high-voltage storage battery 300 and the power receiver 100 are energized. By setting these values, the short-circuit control can be intentionally implemented by turning on the main switches 301H, 301L to energize the high-voltage storage battery 300 and the power receiver 100 before power is supplied from the power transmitter coil 22. In this case, a current sensor corresponds to the "state detection unit."

[0089] For example, a temperature of the rectifier circuit 200 or the high-voltage storage battery 300 may be detected as a physical quantity by a temperature sensor, and the power-receiver controller 231 may determine the execution of the short-circuit control based on the detected temperature, that is, on a comparison between the detected temperature and a determination threshold. In this case, the first determination threshold may be a value for detecting overheating, and the second determination threshold may be a value smaller than the first determination threshold. More specifically, the second determination threshold may be a temperature that the rectifier circuit 200 and the high-voltage storage battery 300 can take under normal conditions (e.g., at the time of startup). By setting these values, the short-circuit control can be intentionally implemented by turning on the main switches 301H, 301L to energize the high-voltage storage battery 300 and the power receiver 100 before power is supplied from the power transmitter coil 22. In this case, the temperature sensor 350 corresponds to the "state detection unit."

[0090] Multiple combinations of parameters (voltage, current, temperature, etc.) as described above may be used to determine the execution of the short-circuit control.

[0091] In step S110 in the first embodiment, the power-receiver controller 231 may determine the number of switches QL1, QL2 that are operating normally, depending on the magnitude of the detected current. This information is useful when identifying the location of malfunction.

[0092] Second Embodiment A second embodiment in which the power receiver 100 of the first embodiment is partially modified will be described below. In addition, the same components as those in the first embodiment are assigned the same reference numerals, and the description thereof will be omitted.

[0093] A power receiver 100 according to the second embodiment will be described with reference to FIG. 6. The source of the first upper arm switch QH1, which is the low potential terminal of the first upper arm switch QH1, and the drain of the first lower arm switch QL1, which is the high potential terminal of the first lower arm switch QL1, are connected to an electrical path H3 connected to the isolated power supply 360. The electrical path H3 is provided with a diode D1 that allows a current to flow from the isolated power supply 360 to the rectifier circuit 200.

[0094] Similarly, the source of the second upper arm switch QH2, which is the low potential terminal of the second upper arm switch QH2, and the drain of the second lower arm switch QL2, which is the high potential terminal of the second lower arm switch QL2, are connected to an electrical path H4 connected to the isolated power supply 360. The electrical path H4 is provided with a diode D2 that allows a current to flow from the isolated power supply 360 to the rectifier circuit 200.

[0095] The isolated power supply 360 of the second embodiment is an energization-confirmation isolated power supply. The isolated power supply 360 supplies current to the power receiver coil 110 via the first lower arm switch QL1 and the second lower arm switch QL2 when the first lower arm switch QL1 and the second lower arm switch QL2 are turned on during the short-circuit control.

[0096] During the short-circuit control, the isolated power supply 360 supplies current to the power receiver coil 110. Therefore, when the switches QL1, QL2 are normally on, the amount of current supplied from the low-voltage storage battery 302 to the isolated power supply 360 also increases. That is, the power consumption increases.

[0097] Therefore, while the rectifier circuit 200 is executing the short-circuit control to short circuit the power receiver coil 110, the determination unit 235 obtains the detected current from the current sensor 340. When the detected current is greater than a predetermined current threshold, the power-receiver controller 231 determines that the rectifier circuit 200 is operating normally as a protection circuit. When the detected current is equal to or less than the current threshold, the power-receiver controller 231 determines that there an abnormality has occurred. The flow of the protection process is similar to that in the first embodiment, and therefore will not be described.

[0098] The power receiver 100 according to the second embodiment has the following effects.

[0099] Because current flows from the isolated power supply 360 to the power receiver coil 110, the amount of current supplied from the low-voltage storage battery 302 to the isolated power supply 360 can be made larger than a case where current is supplied to the drive circuits 370. As a result, the detection current can be increased, making detection easier.

[0100] In addition, since a current is actually passed through the power receiver coil 110, it is also possible to check whether a break has occurred in the electrical path between the power receiver coil 110 and the rectifier circuit 200.

[0101] Modification of Second Embodiment In the above embodiment, the isolated power supply 360 (energization-confirmation isolated power supply) that supplies current to the rectifier circuit 200 and the isolated power supply 360 (driving isolated power supply) that supplies current to the drive circuit 370 may be provided separately.

[0102] In the above embodiment, a current may be supplied from the isolated power supply 360 to the rectifier circuit 200 via the electrical paths H3 and H4 only when the operation of the rectifier circuit 200 is checked during the short-circuit control.

[0103] Third Embodiment A third embodiment in which the power receiver 100 of the first embodiment is partially modified will be described below. In addition, the same components as those in the first embodiment are assigned the same reference numerals, and the description thereof will be omitted.

[0104] In the third embodiment, the determination threshold is gradually decreased before power supply from the power transmitter coil 22. A protection process according to the third embodiment will be described below with reference to FIG. 7. The protection process is executed by the power-receiver controller 231 every predetermined cycle after the power receiver 100 is started up.

[0105] After starting the protection process, the power-receiver controller 231 determines whether it is before the power supply (step S201) in the same way as in step S101 of the first embodiment. When this determination result is negative, the threshold setting unit 237 of the power-receiver controller 231 sets the first determination threshold (step S202). The short-circuit control unit 236 of the power-receiver controller 231 causes the voltage sensor 330 to detect the voltage applied to the smoothing capacitor 210 and acquires the detected voltage from the voltage sensor 330 (step S203). Next, the short-circuit control unit 236 of the power-receiver controller 231 determines whether the acquired detection voltage is greater than or equal to the first determination threshold (step S204). On the other hand, when the determination result in step S204 is negative, the power-receiver controller 231 ends the protection process. When the determination result of step S204 is affirmative, the power-receiver controller 231 performs processing of step S205 and thereafter. Steps S205 to S209 are the same processing as steps S106 to S110 in the first embodiment, so the explanation thereof is omitted.

[0106] On the other hand, when the determination result of step S201 is affirmative (i.e., it is before the power supply), the threshold setting unit 237 of the power-receiver controller 231 sets the initial value of the second determination threshold (step S210). The initial value of the second determination threshold may be less than the first determination threshold and higher than the rated voltage of the high-voltage storage battery 300. In this embodiment, the first determination threshold is used as the initial value of the second determination threshold.

[0107] The short-circuit control unit 236 of the power-receiver controller 231 causes the voltage sensor 330 to detect the voltage applied to the smoothing capacitor 210 and acquires the detected voltage from the voltage sensor 330 (step S211). Next, the short-circuit control unit 236 of the power-receiver controller 231 determines whether the acquired detection voltage is greater than or equal to the second determination threshold (step S212). When this determination result is negative, the threshold setting unit 237 of the power-receiver controller 231 subtracts a predetermined value from the second determination threshold and re-sets the subtracted value as a new second determination threshold (step S213). Then, the processing of step S212 is executed again. In other words, the power-receiver controller 231 repeats the process of steps S212 to S213 until the second determination threshold is the same as or slightly smaller than the detected voltage.

[0108] When the determination result of step S212 is affirmative, the power-receiver controller 231 determines whether the second determination threshold used in step S212 is within a normal range determined in advance(step S214). Here, the detected voltage obtained in step S211 is equal to the applied voltage by the high-voltage storage battery 300 because it is before the power supply. The second determination threshold is approximately equal to this detection voltage. The normal range means a normal range of the voltage of the high-voltage storage battery 300. In other words, in step S214, the power-receiver controller 231 determines whether the voltage of the high-voltage storage battery 300 is normal or not.

[0109] When the result of this determination is negative, the power-receiver controller 231 detects that there is some abnormality in the voltage sensor 330 or the high-voltage storage battery 300 (step S215). When an abnormality is detected, the power-receiver controller 231 notifies an external device such as a higher level ECU of the abnormality. Then, the protection process ends. In general, the high-voltage storage battery 300 is equipped with a battery monitoring device, and if there is an abnormality in the high-voltage storage battery 300, the battery monitoring device notifies the user of the abnormality. Therefore, the notification from the battery monitoring device, together with the notification in step S215, makes it possible to determine whether the voltage sensor 330 is in normal operation.

[0110] On the other hand, when the determination result of step S214 is affirmative, the power-receiver controller 231 performs processing of step S205 and thereafter.

[0111] According to the power receiver 100 of the third embodiment, the following effects are provided.

[0112] The threshold setting unit 237 of the power-receiver controller 231 gradually reduces the second determination threshold before power is transmitted from the power transmitter coil 22 and identifies the second determination threshold that is equivalent to the detected voltage by the voltage sensor 330. The power-receiver controller 231 determines whether the identified second determination threshold is in the normal range as the applied voltage of the high-voltage storage battery 300. This allows the power-receiver controller 231 to detect that there is some abnormality in the voltage sensor 330 or the high-voltage storage battery 300.

[0113] Modification of Third Embodiment The power receiver 100 of each of the above embodiments may be partially modified. The following describes modifications.

[0114] In step S213 of the above third embodiment, when the second determination threshold after re-setting is below the normal range, the power-receiver controller 231 may proceed to step S215 to determine that an abnormality has occurred in the voltage sensor 330 or the high-voltage storage battery 300.

[0115] When there is an abnormality in the high-voltage storage battery 300, the high potential main switch 301H and the low potential main switch 301L are generally not turned on. Under this premise, when the process proceeds to step S215, the power-receiver controller 231 may determine that an error has occurred in the voltage sensor 330.

[0116] Modifications In the above embodiment, when the ignition switch is turned on, the power-receiver controller 231 may determine that it is before power supply from the power transmitter coil 22. A notification switch may be installed in the vehicle 11 and when the notification switch is manually operated on, the power-receiver controller 231 may determine that it is before the power supply.

[0117] In step S110 of the above embodiment, when the short-circuit control cannot be executed, the switch to be turned on in the short-circuit control may be changed. For example, the power-receiver controller 231 may turn on the upper arm switches QH1, QH2 and turn off the lower arm switches QL1, QL2. Even if the lower arm switches QL1, QL2 malfunctions, the short-circuit control can be executed as long as the upper arm switches QH1, QH2 are normal.

[0118] In the above embodiment, the power-receiver controller 231 executes the operation check based on the detected current. However, the power-receiver controller 231 may detect the voltage in the electrical path H2 from the low-voltage storage battery 302 to the isolated power supply 360 and execute the operation check based on the detected voltage. Specifically, when the detected voltage in the electrical path H2 is smaller than the voltage threshold, it may be determined that the electrical path H2 is normal. This information is useful when identifying the location of malfunction.

[0119] In the above embodiment, the protection circuit may have any circuit configuration as long as it can short-circuit the power receiver coil 110. In addition, a protection circuit may be provided separately from the rectifier circuit 200.

[0120] In the above embodiment, the determination unit 235 is provided in the power-receiver controller 231 that controls the rectifier circuit 200. However, the determination unit 235 may be provided in a device other than the power-receiver controller 231.

[0121] In the above embodiment, the positions of the rectifier circuit 200 and the filter circuit 182 may be interchanged.

[0122] In the above embodiment, the rectifier circuit 200 functions as a protection circuit. However, the rectifier circuit 200 and the protection circuit may be provided separately. For example, as shown in FIGS. 8 to 11, a protection circuit 500 includes a bidirectional switch in which two semiconductor switches 501 and 502 are connected in series. The protection circuit 500 is disposed between the high potential path H1 and the low potential path L1. The layout of the protection circuit 500 may be changed arbitrarily. For example, as shown in FIG. 8, the protection circuit 500 may be located inside the power-receiver coil unit 101, between the power receiver coil 110 and the power-receiver resonant circuit 140. Alternatively, as shown in FIG. 9, the protection circuit 500 may be located inside the power-receiver coil unit 101, between the power-receiver resonant circuit 140 and the filter circuit 182. Alternatively, as shown in FIG. 10, the protection circuit 500 may be located inside the power-receiver power supply unit 181, between the power-receiver resonant circuit 140 and the filter circuit 182. Alternatively, as shown in FIG. 11, the protection circuit 500 may be located inside the power-receiver power supply unit 181, between the filter circuit 182 and the rectifier circuit 200.

[0123] The configuration of the protection circuit is not limited to the bidirectional switch, and a protection circuit 1000 including a rectifier circuit 200a and a semiconductor switch SW10 may be adopted. The rectifier circuit 200a includes diodes D11 to D14 as shown in FIG. 12, and the semiconductor switch SW10 is connected in parallel to the rectifier circuit 200a. The position of the protection circuit 1000 may be changed arbitrarily. For example, the protection circuit 1000 may be used instead of the protection circuit 500 shown in FIGS. 8 to 11.

[0124] In the above embodiment, the rectifier circuit 200 may employ rectifier circuits 200b and 200c that includes diodes D11 to D14 as shown in FIGS. 13 and 14. In this case, as shown in FIG. 13, semiconductor switches SW13 and SW14 may be connected in parallel to diodes D13 and D14 constituting the lower arm, thereby allowing the rectifier circuit 200b to function as a protection circuit. Furthermore, as shown in FIG. 14, semiconductor switches SW11 and SW12 may be connected in parallel to diodes D11 and D12 constituting the upper arm, thereby allowing the rectifier circuit 200c to function as a protection circuit.

[0125] While the present disclosure has been described with reference to various exemplary embodiments thereof, it is to be understood that the disclosure is not limited to the disclosed embodiments and constructions. To the contrary, the disclosure is intended to cover various modifications and equivalent arrangements. In addition, while the various elements of the disclosure are shown in various combinations and configurations, which are exemplary, other various combinations and configurations, including more, less or only a single element, are also within the spirit of the disclosure.

Claims

1. An in-vehicle power receiver (100) connected to a power storage unit (300) through a power switch (301H, 301L), the in-vehicle power receiver (100) comprising: a power receiver coil (110) configured to wirelessly receive power supply from a power transmitter coil (22) of a power transmitter (20); a protection circuit (200) configured to short one of paths from the power receiver coil to the power storage unit to cut off power supply from the power receiver coil; a state detection unit (330) configured to detect a physical quantity indicative of a state of the in-vehicle power receiver or the power storage unit; and a power-receiver controller (231) configured to execute short-circuit control using the protection circuit when the physical quantity detected by the state detection unit is greater than or equal to a determination threshold, wherein the determination threshold is changeable, and the power-receiver controller is configured to decrease the determination threshold and determine whether the short-circuit control is normally executed based on the determination threshold when the power switch is turned on and voltage is applied from the power storage unit to the power receiver before power transmission from the power transmitter coil.

2. The in-vehicle power receiver according to claim 1, wherein the power-receiver controller is configured to gradually decrease the determination threshold before the power transmission from the power transmitter coil, and determine whether the determination threshold is in a normal range at time when the physical quantity detected by the state detection unit becomes greater than or equal to the changed determination threshold.

3. The in-vehicle power receiver according to claim 2, wherein the normal range is set based on voltage of the power storage unit, and the power-receiver controller is configured to determine that there is a possibility of an abnormality in the state detection unit when the determination threshold is below the normal range.

4. The in-vehicle power receiver according to any one of claims 1 to 3, further comprising: an isolated power supply (360) arranged across a high voltage region where the protection circuit is disposed and a low voltage region, and configured to supply power to the protection circuit; a detection unit (340) disposed in the low voltage region and detecting a current supplied to or a voltage applied to the isolated power supply; and a determination unit (235) disposed in the low voltage region and configured to determine whether the protection circuit is operating normally based on the current or voltage detected by the detection unit.

5. The in-vehicle power receiver according to claim 4, wherein the protection circuit includes at least one semiconductor switching element (QH1, QH2, QL1, QL2), the in-vehicle power receiver further comprises a drive circuit (370) configured to drive the at least one semiconductor switching element, and the isolated power supply is a driving isolated power supply configured to supply driving power to a gate of the at least one semiconductor switching element via the drive circuit.

6. The in-vehicle power receiver according to claim 5, wherein the detection unit is configured to detect a current supplied to or a voltage applied to the driving isolated power supply from a low-voltage storage battery (302) disposed in the low voltage region, and the determination unit is configured to determine that the at least one semiconductor switching element of the protection circuit is operating normally when the detected current is greater than a current threshold or when the detected voltage is less than a voltage threshold.

7. The in-vehicle power receiver according to claim 6, wherein the at least one semiconductor switching element is one of semiconductor switching elements (QH1, QH2, QL1, QL2), and the determination unit is configured to determine a number of semiconductor switching elements operating among the semiconductor switching elements based on a magnitude of the detected current or voltage.

8. The in-vehicle power receiver according to claim 4, wherein the protection circuit includes at least one semiconductor switching element (QH1, QH2, QL1, QL2), and the isolated power supply is an energization-confirmation isolated power supply configured to supply a current to the power receiver coil via the at least one semiconductor switching element when the at least one semiconductor switching element is turned on.

9. The in-vehicle power receiver according to claim 8, wherein the detection unit is configured to detect a current supplied to or a voltage applied to the energization-confirmation isolated power supply from a low-voltage storage battery disposed in the low voltage region, and the determination unit is configured to determine that the at least one semiconductor switching element of the protection circuit is turned on in normal operation when the detected current is greater than a current threshold or when the detected voltage is less than a voltage threshold.

10. A wireless power transfer system (10) comprising: a power transmitter (20) having a power transmitter coil (22); and an in-vehicle power receiver (100) having a power receiver coil (110) and mounted on a vehicle (11), wherein the power transmitter coil is configured to wirelessly supply power to the power receiver coil, the in-vehicle power receiver (100) is connected to a power storage unit (300) through a power switch (301H, 301L), the in-vehicle power receiver includes a protection circuit (200) configured to short one of paths from the power receiver coil to the power storage unit to cut off power supply from the power receiver coil, a state detection unit (330) configured to detect a physical quantity indicative of a state of the in-vehicle power receiver or the power storage unit, and a power-receiver controller (231) configured to execute short-circuit control using the protection circuit when the physical quantity detected by the state detection unit is greater than or equal to a determination threshold, the determination threshold is changeable, and the power-receiver controller is configured to decrease the determination threshold and determine whether the short-circuit control is normally executed based on the determination threshold when the power switch is turned on and voltage is applied from the power storage unit to the power receiver before power transmission from the power transmitter coil.

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