Wireless power supply system and power reception device

Abstract

To provide a wireless power supply system in which overvoltage protection can be realized at the power reception side without adopting a special circuitry configuration.SOLUTION: A power reception device 3 includes a rectifier 32 that converts received AC voltage to DC voltage and outputs the DC voltage to between a high-potential side line 41 and a low-potential side line 42, an input capacitor C1 that smooths the output of the rectifier 32, a DCDC converter 5 that receives the DC voltage smoothed by the input capacitor C1 as input voltage Vin, converts the input voltage Vin to desired output voltage Vout by controlling the on / off of at least two switching elements SW1, SW2, and outputs the output voltage to a load, and an overvoltage detection unit 51 that detects overvoltage of the input voltage Vin. When the overvoltage detection unit 51 detects overvoltage, the DCDC converter 5 executes overvoltage protection operation of forming a current path to allow protection current Ipro to flow therethrough between the high-potential side line 41 and the low-potential side line 42 by controlling the switching elements SW1, SW2 to be on.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] An embodiment of the present disclosure relates to a wireless power supply system and a power receiving device. [Background technology]

[0002] In a wireless power transfer (WPT) system consisting of a power transmitter and a power receiver, excessive power reception can cause input overvoltage in the power receiver, damaging the rectifier circuit or charging circuit. Input overvoltage can occur when the power transmitter and power receiver are closer than expected, or when the battery is disconnected.

[0003] Therefore, a technology has been proposed for overvoltage protection that prevents damage due to input overvoltage by discharging to the ground line when an input overvoltage is detected on the power receiving side (see, for example, Patent Document 1). In Patent Document 1, a short-circuit switch is used in the diode bridge section as an overvoltage protection circuit. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] U.S. Patent Application Publication No. 2021 / 0376642 [Non-patent literature]

[0005] [Non-Patent Document 1] Masaki Kato, "Wireless Power Supply to Electric Vehicles Using Magnetic Resonance Coupling," doctoral dissertation Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the prior art, it was necessary to employ a special circuit configuration such as a short-circuit switch or a rectifier made up of switching elements as an overvoltage protection circuit.

[0007] The present disclosure aims to provide a wireless power supply system and a power receiving device that can achieve overvoltage protection on the power receiving side without employing a special circuit configuration. [Means for solving the problem]

[0008] The wireless power supply system disclosed herein is a wireless power supply system including a power transmitting device and a power receiving device that contactlessly receives AC voltage transmitted from the power transmitting device, wherein the power receiving device includes a rectifier that converts the received AC voltage into a DC voltage and outputs it between a high-potential side line and a low-potential side line, an input capacitor that smooths the output of the rectifier, a DCDC converter that uses the DC voltage smoothed by the input capacitor as an input voltage and controls the on / off of two or more switching elements to convert the input voltage into a desired output voltage and output it to a load, and an overvoltage detection unit that detects overvoltage of the input voltage, wherein when the overvoltage detection unit detects the overvoltage, the DCDC converter performs an overvoltage protection operation that forms a current path through which a protection current flows between the high-potential side line and the low-potential side line by controlling the on-off of the switching elements. [Effects of the Invention]

[0009] The wireless power feeding system of the present disclosure can perform overvoltage protection operation using the switching element of the DC-DC converter 5 included in the power receiving device 3, and therefore can achieve overvoltage protection on the power receiving side without employing a special circuit configuration. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a diagram illustrating a configuration of a first embodiment of a wireless power supply system. [Figure 2] FIG. 3 is an explanatory diagram of an overvoltage protection operation according to the first embodiment. [Figure 3] 2 is a waveform diagram of each part of the DC-DC converter shown in FIG. 1. [Figure 4] FIG. 10 is a diagram illustrating a configuration of a second embodiment of a wireless power supply system. [Figure 5] FIG. 10 is an explanatory diagram of an overvoltage protection operation according to the second embodiment. [Figure 6] 5A to 5C are waveform diagrams of the various parts of the DC-DC converter shown in FIG. [Figure 7] FIG. 10 is a diagram illustrating a configuration of a DC-DC converter according to a third embodiment. [Figure 8] 8A to 8C are waveform diagrams of the various parts of the DC-DC converter shown in FIG. 7. [Figure 9] 8A to 8C are waveform diagrams of the various parts of the DC-DC converter shown in FIG. 7. [Figure 10] FIG. 10 is a diagram illustrating a configuration of a power receiving device according to a fourth embodiment. [Figure 11] 11A to 11C are waveform diagrams of the various parts of the DC-DC converter shown in FIG. [Figure 12] FIG. 13 is a diagram illustrating another configuration of a power receiving device according to the fourth embodiment. [Figure 13] 2 is a diagram illustrating an example of a regulator circuit of the DC-DC converter shown in FIG. 1. [Figure 14] FIG. 10 is a diagram illustrating an example of a gate signal during an overvoltage protection operation. DETAILED DESCRIPTION OF THE INVENTION

[0011] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings.

[0012] (First embodiment) 1, a wireless power supply system 1 according to the first embodiment includes a power transmitting device 2 and a power receiving device 3. The power receiving device 3 receives AC voltage transmitted from the power transmitting device 2 in a wireless manner and outputs the AC voltage to a load 10 such as a battery.

[0013] The power transmitting device 2 includes a power source 21, an inverter 22, and a power transmitting-side resonator 23. The power transmitting device 2 also includes a power transmitting-side transceiver 24 that communicates with the power receiving device 3 wirelessly.

[0014] The power supply 21 converts AC voltage supplied from a commercial power supply (not shown) into DC voltage. The inverter 22 converts the DC voltage supplied from the power supply into AC voltage of a predetermined frequency, and transmits it to the power receiving device 3 via the power transmitting side resonator 23.

[0015] The power transmitting side resonator 23 is a power transmitting coil L TX and the transmitting coil L TX The transmitting-side resonant capacitor C is connected in series with TX The resonant frequency of the power transmission side resonator 23 is designed to be a predetermined frequency (for example, about several tens of kilohertz to several tens of megahertz) of the AC voltage converted by the inverter 22. The power transmission side resonator 23 is an example of a resonant circuit, and the configuration is not particularly limited.

[0016] The power receiving device 3 includes a power receiving side resonator 31, a rectifier 32, an input capacitor C1, and a DC-DC converter 5. The power receiving device 3 also includes a power receiving side transceiver 33 that communicates with the power transmitting device 2 wirelessly.

[0017] The power receiving side resonator 31 is connected to the power receiving coil L RX and the receiving coil L RX The receiving-side resonant capacitor C is connected in series to RX The resonant frequency of the power receiving side resonator 31 is designed to be the same as or close to the resonant frequency of the power transmitting side resonator 23.

[0018] The rectifier 32 is configured as a well-known full-wave rectifier such as a diode bridge circuit, and converts the AC voltage received by the power receiving side resonator 31 into a DC voltage.

[0019] The input capacitor C1 is connected between the high potential side line 41 and the low potential side line 42, which are the output lines of the rectifier 32, and attenuates the AC components of the output voltage and current of the rectifier 32.

[0020] The DC-DC converter 5 converts the output voltage of the rectifier 32 into the input voltage V in and the input voltage V in to the desired output voltage Vout and outputs it to a load 10. The DC-DC converter 5 includes a high-side switching element SW1 (hereinafter referred to as SW1) and a low-side switching element SW2 (hereinafter referred to as SW2) connected in series between a high-potential side line 41 and a low-potential side line 42. SW1 and SW2 are configured with semiconductor switches such as MOS-FETs (Metal-Oxide Semiconductor Field-Effect Transistors) and IGBTs (Insulated Gate Bipolar Transistors). In the following description, SW1 and SW2 will be described as MOS-FETs.

[0021] The connection point between the source terminal of SW1 and the drain terminal of SW2 is connected to the low potential side line 42 via an inductor L and an output capacitor C2, and the voltage across the output capacitor C2 is equal to the output voltage V out is output as

[0022] The DC-DC converter 5 includes an overvoltage detection unit 51, a control unit 52, a driver 53, and a current detection circuit 54. The overvoltage detection unit 51 detects an input voltage V in By comparing the input voltage V with a preset threshold voltage Vth, in becomes equal to or greater than the threshold voltage Vth, an overvoltage is detected. The overvoltage detection unit 51 outputs to the control unit 52 an overvoltage detection signal OV that is normally low (when no overvoltage is detected) and goes high when an overvoltage is detected.

[0023] When no overvoltage is detected, the overvoltage detection unit 51 outputs a low-level overvoltage detection signal OV to the control unit 52, and the control unit 52 controls the on / off of SW1 and SW2 alternately (complementarily). As a result, when no overvoltage is detected, as shown in FIG. 2(a), an output current I flows through a current path indicated by an arrow X passing through SW1 when SW1 is on and SW2 is off, and through a current path indicated by an arrow Y passing through SW2 when SW1 is off and SW2 is on. out is playing.

[0024] When an overvoltage is detected, the overvoltage detection unit 51 outputs a Hi-level overvoltage detection signal OV to the control unit 52, and the control unit 52 executes an overvoltage protection operation by turning on both SW1 and SW2. As a result, when an overvoltage is detected, a protection current I flows through a current path that passes through both SW1 and SW2, as shown by arrow Z in FIG. 2(b). pro flows, and the overvoltage is eliminated.

[0025] It is known that when the wireless power supply system 1 is expressed as an equivalent circuit between the power transmitting side resonator 23 and the power receiving side resonator 31, the output of the power receiving side resonator 31 has the characteristics of a constant current source (see, for example, pages 41-42 of Non-Patent Document 1). in remains constant even when the load 10 is changed. In other words, even when both SW1 and SW2 are turned on to short-circuit the high potential side line 41 and the low potential side line 42, the protection current I pro is the input current I in Immediately after the overvoltage protection operation is performed, the charge stored in the input capacitor C1 is discharged all at once, so the protection current I pro is the input current I in A larger peak current will flow than

[0026] Furthermore, when an overvoltage is detected, the control unit 52 can also transmit an overvoltage notification signal to the power transmitting device 2 via the power receiving side transmitting / receiving unit 33, requesting that power transmission be stopped.

[0027] Figure 3 shows the input current I in 10 is a waveform diagram of each part in the DC-DC converter 5 when the current becomes excessively large. Power transmission coil L TX - Receiving coil L RX The input current I in When increases, the input voltage Vin increases, and the input current I in Then, at time t0, the input voltage V in becomes equal to or greater than the threshold voltage Vth, the overvoltage detection unit 51 detects an overvoltage and causes the overvoltage detection signal OV to transition from a low level to a high level.

[0028] G SW1 , G SW2 are the gate signals that drive SW1 and SW2, respectively. SW1 , G SW2 are predetermined complementary signals before time t0 when no overvoltage is detected, and both become Hi level due to the overvoltage protection operation when an overvoltage is detected.

[0029] When overvoltage protection is activated, a protection current I flows through both SW1 and SW2. pro The current path is formed as follows: Input voltage V in is the protection current I pro The protection current I flows through SW1 and SW2, which drops and eliminates the overvoltage. pro becomes a large peak current due to the charge stored in the input capacitor C1, but when the charge stored in the input capacitor C1 is discharged, the input current I in is the same value as

[0030] The overvoltage protection operation is released when the protection current I flowing through SW2 is detected by the current detection circuit 54. pro It monitors the protection current I pro is the preset current threshold I th The current threshold I th is the input current I when overvoltage is detected in0 This allows the DC-DC converter 5 to automatically recover from the overvoltage protection operation.

[0031] The overvoltage protection operation of the first embodiment described above turns on both SW1 and SW2 connected in series between the high potential side line 41 and the low potential side line 42. Therefore, various types of DC-DC converters 5 can be adopted as long as they are provided with SW1 and SW2 connected in series between the high potential side line 41 and the low potential side line 42.

[0032] (Second embodiment) 4, in the wireless power supply system 1a of the second embodiment, the DC-DC converter 5a of the power receiving device 3a is configured as a full-bridge type buck-boost converter. In addition to the configuration of the DC-DC converter 5, the DC-DC converter 5a includes a high-side switching element SW3 (hereinafter referred to as SW3) and a low-side switching element SW4 (hereinafter referred to as SW4). SW3 and SW4 are MOS-FETs.

[0033] SW3 and SW4 are connected in parallel to the output capacitor C2, and the connection point between SW1 and SW2 is connected to the connection point between SW3 and SW4 via the inductor L. Therefore, in the DC-DC converter 5a, SW1, the inductor L, and SW4 are connected in series between the high-potential side line 41 and the low-potential side line 42.

[0034] When no overvoltage is detected, overvoltage detection unit 51 outputs a low-level overvoltage detection signal OV to control unit 52, and control unit 52 alternately (complementarily) turns SW1 and SW2 on and off, keeping SW3 always on and SW4 always off. As a result, when no overvoltage is detected, as shown in Figure 5(a), output current Iout flows through the current path indicated by arrow Xa, which passes through SW1, inductor L, and SW3, when SW1 is on and SW2 is off, and through the current path indicated by arrow Ya, which passes through SW2, inductor L, and SW3, when SW1 is off and SW2 is on.

[0035] When an overvoltage is detected, the overvoltage detection unit 51 outputs a Hi-level overvoltage detection signal OV to the control unit 52, and the control unit 52 turns on both SW1 and SW4 and turns off both SW2 and SW3 as an overvoltage protection operation. As a result, when an overvoltage is detected, a protection current I flows through a current path passing through SW1, inductor L, and SW4, as shown by an arrow Za in FIG. 5(b). pro In the second embodiment, the protective current I pro flows via inductor L, suppressing the large current that occurs immediately after the overvoltage protection operation is performed.

[0036] Figure 6 shows the input current Iin 10 is a waveform diagram of each part in the DC-DC converter 5a when the current becomes excessively large. Power transmission coil L TX - Receiving coil L RX The input current I in When increases, the input voltage Vin increases, and the input current I in Then, at time t0, the input voltage V in becomes equal to or greater than the threshold voltage Vth, the overvoltage detection unit 51 detects an overvoltage and causes the overvoltage detection signal OV to transition from a low level to a high level.

[0037] G SW1 , G SW2 , G SW3 , G SW4 are the gate signals that drive SW1, SW2, SW3, and SW4, respectively. SW1 , G SW2 is a predetermined complementary signal before time t0 when no overvoltage is detected, and the gate signal G SW1 becomes Hi level, and the gate signal G SW2 The gate signal G SW3 is always at a high level before time t0 when no overvoltage is detected, and becomes a low level when the overvoltage protection operation is performed. SW4 is always at a low level before time t0 when no overvoltage is detected, and becomes a high level when the overvoltage protection operation is performed.

[0038] When overvoltage protection is performed, a protection current I flows through the current path that passes through SW1, inductor L, and SW4. pro flows, and the input voltage V in The protection current I flows through SW4. pro In this case, the charge stored in the input capacitor C1 is gradually discharged via the inductor L, so that the peak current is suppressed.

[0039] (Third embodiment) Referring to FIG. 7, a DC-DC converter 5b according to the third embodiment includes a gate resistance switching circuit 55 that switches the gate resistances of SW1 and SW2 in addition to the configuration of the DC-DC converter 5 according to the first embodiment.

[0040] The gate resistance switching circuit 55 includes, for example, two resistors connected in series, a bypass that short-circuits one of the resistors, and a selector switch provided in the bypass. The gate resistance switching circuit 55 is set to a low resistance when the selector switch is on, and to a high resistance when the selector switch is off.

[0041] When no overvoltage is detected, the overvoltage detection unit 51 outputs a low-level overvoltage detection signal OV to the control unit 52, and the control unit 52 sets the gate resistance switching circuit 55 to a low resistance and controls the on / off of SW1 and SW2 alternately (complementarily).

[0042] When an overvoltage is detected, the overvoltage detection unit 51 outputs a high-level overvoltage detection signal OV to the control unit 52, and the control unit 52 sets the gate resistance switching circuit 55 to a high resistance and performs an overvoltage protection operation by turning on both SW1 and SW2.

[0043] Figure 8 shows the input current I in 10 is a waveform diagram of each part in the DC-DC converter 5b when the current becomes excessively large. Power transmission coil L TX - Receiving coil L RX The input current I in When increases, the input voltage Vin increases, and the input current I in Then, at time t0, the input voltage V in becomes equal to or greater than the threshold voltage Vth, the overvoltage detection unit 51 detects an overvoltage and causes the overvoltage detection signal OV to transition from a low level to a high level.

[0044] G SW1 , G SW2 are the gate signals that drive SW1 and SW2, respectively. SW1 , G SW2are predetermined complementary signals before time t0 when no overvoltage is detected, and both become Hi level due to the overvoltage protection operation when an overvoltage is detected. When no overvoltage is detected, the gate resistance switching circuit 55 is set to a low resistance, so that the gate signal G SW1 , G SW2 On the other hand, when an overvoltage is detected, the gate resistor switching circuit 55 is set to a high resistance, so that the gate signal G SW1 , G SW2 That is, the switching speed when SW1 and SW2 are turned on (turned on) is set to be fast when no overvoltage is detected, and set to be slow when an overvoltage is detected.

[0045] If SW1 or SW2 is on when an overvoltage is detected, both are turned on by turning them off (turning them off) and then turning them on again at a slow switching speed. This allows the gate resistance switching circuit 55 to be provided for only one of SW1 and SW2. For example, as shown in FIG. 9, the gate resistance switching circuit 55 can be provided for only SW1, so that it can handle the case where SW1 is on when an overvoltage is detected.

[0046] When overvoltage protection is activated, the protection current I flows through the current paths that pass through both SW1 and SW2. pro flows, and the input voltage V in The switch current I flowing through SW2 drops and the overvoltage is eliminated. SW2 At this time, the charge stored in the input capacitor C1 is gradually discharged due to the slow switching speed of SW1 and SW2, and the protection current I pro Therefore, the peak current is suppressed.

[0047] (Fourth embodiment) Referring to Figure 10, the power receiving device 3c of the fourth embodiment has, in addition to the configuration of the power receiving device 3 of the first embodiment, a connection disconnection circuit 56 that cuts off the electrical connection between the input capacitor C1 and the high-potential side line 41.

[0048] The connection / disconnection circuit 56 is configured, for example, by a disconnection switch connected between the input capacitor C1 and the high-potential side line 41. When the disconnection switch is on, the connection / disconnection circuit 56 connects the input capacitor C1 and the high-potential side line 41, and when the disconnection switch is off, the connection / disconnection circuit 56 disconnects the input capacitor C1 from the high-potential side line 41. The connection / disconnection circuit 56 may also cut off the electrical connection between the input capacitor C1 and the low-potential side line 42. In this case, the connection / disconnection circuit 56 is configured by a disconnection switch connected between the input capacitor C1 and the low-potential side line 42.

[0049] When no overvoltage is detected, the overvoltage detection unit 51 outputs a low-level overvoltage detection signal OV to the control unit 52, and the control unit 52 turns on the disconnection switch of the disconnection circuit 56 to connect the input capacitor C1 to the high-potential side line 41, and controls the on / off of SW1 and SW2 alternately (complementarily).

[0050] When an overvoltage is detected, the overvoltage detection unit 51 outputs a Hi-level overvoltage detection signal OV to the control unit 52, and the control unit 52 performs an overvoltage protection operation by turning off the disconnection switch of the disconnection circuit 56 to disconnect the input capacitor C1 from the high-potential side line 41 and turning on both SW1 and SW2.

[0051] Figure 11 shows the input current I in 10 is a waveform diagram of each part in the DC-DC converter 5 when the current becomes excessively large. Power transmission coil L TX - Receiving coil L RX The input current I in When increases, the input voltage Vin increases, and the input current I in Then, at time t0, the input voltage V in becomes equal to or greater than the threshold voltage Vth, the overvoltage detection unit 51 detects an overvoltage and causes the overvoltage detection signal OV to transition from a low level to a high level.

[0052] Gate signal G SW1 , G SW2are predetermined complementary signals before time t0 when no overvoltage is detected. When an overvoltage is detected, the overvoltage protection operation causes a protection current I to flow through the current path that passes through both SW1 and SW2. pro flows, and the input voltage V in The overvoltage protection circuit 56 disconnects the input capacitor C1 from the high-potential side line 41. Therefore, the charge stored in the input capacitor C1 flows through the protection current I pro The protection current I pro Therefore, the peak current is suppressed.

[0053] The same effect can be obtained even if the connection / disconnection circuit 56 is added to the configuration of the second embodiment, as in the case of a power receiving device 3d shown in FIG.

[0054] As described above, in the first to fourth embodiments, the protective current I pro However, during overvoltage protection operation, only SW2 or both SW1 and SW2 may be resistance-controlled so that the input voltage Vin becomes a constant voltage. In this case, as in the first to fourth embodiments, the protection current I pro The peak current can be suppressed.

[0055] In the first to fourth embodiments, the DC-DC converters 5 to 5 b may include a regulator circuit 57 that receives power from a load 10 such as a battery, as in the DC-DC converter 5 e shown in Fig. 13. The regulator circuit 57 is an internal power supply that supplies power to each component of the DC-DC converter 5 e. During overvoltage protection operation, the input voltage Vin becomes 0 V, but providing the regulator circuit 57 allows power to continue to be supplied to the control unit 52 of the DC-DC converters 5 to 5 b.

[0056] In the first to fourth embodiments, during overvoltage protection operation, both SW1 and SW2 (SW4) connected in series between the high potential side line 41 and the low potential side line 42 are turned on to supply a protection current I proIn the overvoltage protection operation, the period during which both SW1 and SW2 (SW4) are turned on may be intermittent, as shown in FIG.

[0057] FIG. 14 shows the gate signal G when the overvoltage protection operation starts at time t0 and is released at time t1. SW1 , G SW2 When the overvoltage detection signal OV is at Hi level, the gate signal G SW2 By accelerating the turn-on timing of SW1 and SW2 (SW4), a period Ta is formed in which both SW1 and SW2 (SW4) are turned on. In addition, SW2 is provided with a gate resistance switching circuit 55, and the gate signal G SW2 In this way, when both SW1 and SW2 (SW4) are turned on intermittently, the protection current I pro It is preferable to adopt the configurations of the second to fourth embodiments in which the peak current is suppressed.

[0058] As described above, this embodiment is a wireless power supply system 1 including a power transmitter 2 and a power receiver 3 that receives AC voltage transmitted from the power transmitter 2 in a wireless manner. The power receiver 3 includes a rectifier 32 that converts the received AC voltage into DC voltage and outputs it between a high-potential side line 41 and a low-potential side line 42, an input capacitor C1 that smoothes the output of the rectifier 32, and a converter that converts the DC voltage smoothed by the input capacitor C1 into an input voltage V. in and controls the on / off of two or more switching elements SW1 and SW2 to control the input voltage V in to the desired output voltage V out and outputs it to a load, and an overvoltage detection unit 51 that detects an overvoltage of the input voltage Vin. When an overvoltage is detected by the overvoltage detection unit 51, the DC-DC converter 5 controls the switching elements SW1 and SW2 to turn on, thereby causing a protection current I to flow between the high-potential side line 41 and the low-potential side line 42. pro This performs overvoltage protection by forming a current path through which With this configuration, overvoltage protection operation can be performed using SW1 and SW2 of the DC-DC converter 5 included in the power receiving device 3, so overvoltage protection on the power receiving side can be achieved without employing a special circuit configuration.

[0059] Furthermore, according to this embodiment, the DC-DC converter 5 has a protection current I pro The current detection circuit 54 detects the protection current I pro becomes less than a preset current threshold, the DC-DC converter 5 cancels the overvoltage protection operation. This configuration enables the DC-DC converter 5 to automatically recover from the overvoltage protection operation.

[0060] Furthermore, according to this embodiment, the protection current I pro An inductor L is placed in this current path. This configuration allows the charge stored in the input capacitor C1 to be gradually discharged, thereby reducing the protection current I pro The peak current can be suppressed.

[0061] According to the present embodiment, the DC-DC converter 5 includes a gate resistance switching circuit 55 as a switching speed switching circuit for switching the switching speed of the switching elements SW1 and SW2. In the overvoltage protection operation, the gate resistance switching circuit 55 reduces the switching speed of the switching elements SW1 and SW2 that are turned on. This configuration allows the charge stored in the input capacitor C1 to be gradually discharged, thereby reducing the protection current I pro The peak current can be suppressed.

[0062] Furthermore, according to this embodiment, the power receiving device 3 includes a disconnection circuit 56 that disconnects the electrical connection between the high-potential side line 41 or the low-potential side line 42 and the input capacitor C1. When the overvoltage detection unit 51 detects an overvoltage, the DC-DC converter 5 causes the disconnection circuit 56 to electrically disconnect the high potential side line 41 or the low potential side line 42 from the input capacitor C1. This configuration eliminates the peak current caused by the charge stored in the input capacitor C1, so the protection current I pro The peak current can be suppressed.

[0063] According to this embodiment, the DC-DC converter 5 controls the switching elements SW1 and SW2, which are turned on during overvoltage protection operation, based on the input voltage V in The resistance is controlled so that the voltage becomes constant. This configuration ensures that the power supply for the DC-DC converter 5 is maintained during overvoltage protection operation.

[0064] Furthermore, according to this embodiment, the DC-DC converter 5 has a protection current I pro The current path is intermittently formed. With this configuration, by changing the timing of the gate signal during normal operation, it is possible to ensure the power supply for the DC-DC converter 5 during overvoltage protection operation.

[0065] According to this embodiment, the DC-DC converter 5 includes a regulator circuit 57 that receives power supply from the load 10. This configuration ensures that the power supply for the DC-DC converter 5 is maintained during overvoltage protection operation.

[0066] It is clear that the present invention is not limited to the above-described embodiments, and that each embodiment can be appropriately modified within the scope of the technical concept of the present invention. Furthermore, the number, position, shape, etc. of the above-described components are not limited to the above-described embodiments, and the number, position, shape, etc. can be set to be suitable for implementing the present invention. Note that the same components are denoted by the same reference numerals in each drawing. [Explanation of symbols]

[0067] 1, 1a Wireless Power Supply System 2. Power transmission equipment 3, 3a, 3b, 3c, 3d, 3e Power receiving device 5, 5a, 5b, 5e DC-DC converter 10 Load 21 Power supply 22 Inverter 23 Power transmitting resonator 24 Power transmission side transceiver 31 Receiving side resonator 32 Rectifier 33 Power receiving side transmitter / receiver 41 High potential line 42 Low potential line 51 Overvoltage detection section 52 Control section 53 Driver 54 Current detection circuit 55 Gate resistor switching circuit 56 Disconnect Circuit 57 Regulator circuit C1 Input capacitor C2 output capacitor

Claims

1. A wireless power supply system including a power transmitting device and a power receiving device that receives AC voltage transmitted from the power transmitting device in a wireless manner, The power receiving device is a rectifier that converts the received AC voltage into a DC voltage and outputs the DC voltage between a high-potential side line and a low-potential side line; an input capacitor for smoothing the output of the rectifier; a DC-DC converter that uses the DC voltage smoothed by the input capacitor as an input voltage, controls on / off of two or more switching elements to convert the input voltage into a desired output voltage, and outputs the output voltage to a load; an overvoltage detection unit that detects an overvoltage of the input voltage, When the overvoltage detection unit detects the overvoltage, the DC-DC converter a wireless power supply system that performs an overvoltage protection operation by controlling the switching element to be on, thereby forming a current path through which a protection current flows between the high-potential side line and the low-potential side line.

2. the DC-DC converter includes a current detection circuit that monitors the protection current; 2. The wireless power supply system according to claim 1, wherein when the protection current is detected by the current detection circuit to be less than a preset current threshold, the DC-DC converter cancels the overvoltage protection operation.

3. 3. The wireless power supply system according to claim 1, wherein an inductor is disposed in the current path.

4. the DC-DC converter includes a switching speed switching circuit that switches the switching speed of the switching element; 3. The wireless power supply system according to claim 1, wherein in the overvoltage protection operation, the switching speed of the switching element to be turned on is reduced by the switching speed changeover circuit.

5. the power receiving device includes a disconnection circuit that disconnects an electrical connection between the high-potential side line or the low-potential side line and the input capacitor; 3. The wireless power supply system according to claim 1, wherein when the overvoltage is detected by the overvoltage detection unit, the DC-DC converter disconnects the electrical connection between the high-potential side line or the low-potential side line and the input capacitor using the disconnection circuit.

6. 3. The wireless power supply system according to claim 1, wherein the DC-DC converter performs resistance control on the switching element that is turned on during the overvoltage protection operation so that the input voltage becomes a constant voltage.

7. The wireless power supply system according to claim 1 or 2, wherein the DC-DC converter forms the current path intermittently.

8. 2. The wireless power supply system according to claim 1, wherein the DC-DC converter includes a regulator circuit that receives power from the load.

9. A power receiving device that wirelessly receives AC voltage transmitted from a power transmitting device, a rectifier that converts the received AC voltage into a DC voltage and outputs the DC voltage between a high-potential side line and a low-potential side line; an input capacitor for smoothing the output of the rectifier; a DC-DC converter that uses the DC voltage smoothed by the input capacitor as an input voltage and controls on / off of two or more switching elements to convert the input voltage into a desired output voltage; an overvoltage detection unit that detects an overvoltage of the input voltage, When the overvoltage detection unit detects the overvoltage, the DC-DC converter The power receiving device performs an overvoltage protection operation by controlling the switching element to be on, thereby forming a current path through which a protection current flows between the high-potential side line and the low-potential side line.

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