Wireless power supply system and power receiving device

Abstract

The invention provides a wireless power supply system and a power receiving device, which can realize overvoltage protection on a power receiving side without adopting a special circuit structure. A power receiving device (3) is provided with: a rectifier (32) that converts a received AC voltage into a DC voltage and outputs the DC voltage between a high-potential-side line (41) and a low-potential-side line (42); an input capacitor (C1) for smoothing the output of the rectifier; a DC-DC converter (5) that uses the DC voltage smoothed by the input capacitor as an input voltage (Vin), controls the ON / OFF of the two or more switching elements (SW1, SW2), converts the input voltage into a desired output voltage (Vout), and outputs the desired output voltage to a load; and an overvoltage detection unit (51) that detects an overvoltage of the input voltage, and when the overvoltage detection unit detects the overvoltage, the DC-DC converter performs an overvoltage protection operation that forms a current path through which a protection current (Ipro) flows between the high-potential-side line (41) and the low-potential-side line (42) by ON control of the switching element.

Description

Technical Field

[0001] Embodiments of the present disclosure relate to a wireless power supply system and a power receiving device. Background Art

[0002] In wireless power transfer (WPT) systems consisting of a power transmitter and a power receiver, excess power can cause input overvoltage in the power receiver, potentially damaging the rectifier and charging circuits. This overvoltage can occur when the distance between the power transmitter and the power receiver becomes greater than expected, or when the battery is disconnected.

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

[0004] Patent Document 1: U.S. Patent Application Publication No. 2021 / 0376642

[0005] Non-Patent Literature 1: Masaki Kato, "Wireless Power Supply for Electric Vehicles Based on Magnetic Field Resonance Coupling," PhD thesis Summary of the Invention

[0006] However, in the prior art, a special circuit structure such as a short-circuit switch or a rectifier composed of switching elements needs to be adopted as an overvoltage protection circuit.

[0007] The present disclosure provides a wireless power supply system and a power receiving device that can implement overvoltage protection on a power receiving side without adopting a special circuit structure.

[0008] The wireless power supply system disclosed herein comprises: a power transmitting device; and a power receiving device that receives an AC voltage transmitted from the power transmitting device in a contactless manner, wherein the power receiving device comprises: 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 that smoothes the output of the rectifier; a DC-DC converter that uses the DC voltage smoothed by the input capacitor as an input voltage, controls the on / off switching of two or more switching elements to convert the input voltage into a desired output voltage, and outputs the desired output voltage to a load; and an overvoltage detection unit that detects an overvoltage in the input voltage. When the overvoltage detection unit detects the overvoltage, the DC-DC converter performs an overvoltage protection operation to form a current path for a protection current to flow between the high-potential side line and the low-potential side line by controlling the on / off switching of the switching elements.

[0009] The wireless power supply system of the present disclosure can perform overvoltage protection using the switching elements of the DC-DC converter 5 included in the power receiving device 3 , thereby achieving overvoltage protection on the power receiving side without adopting a special circuit configuration. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 It is a diagram showing the configuration of a first embodiment of a wireless power supply system.

[0011] Figure 2 It is an explanatory diagram of the overvoltage protection operation in the first embodiment.

[0012] Figure 3 yes Figure 1 The waveform diagram of each part of the DC-DC converter is shown.

[0013] Figure 4 It is a diagram showing the configuration of a second embodiment of a wireless power supply system.

[0014] Figure 5 It is an explanatory diagram of the overvoltage protection operation of the second embodiment.

[0015] Figure 6 yes Figure 4 The waveform diagram of each part of the DC-DC converter is shown.

[0016] Figure 7 It is a diagram showing the configuration of a DC-DC converter in the third embodiment.

[0017] Figure 8 yes Figure 7 The waveform diagram of each part of the DC-DC converter is shown.

[0018] Figure 9 yes Figure 7 The waveform diagram of each part of the DC-DC converter is shown.

[0019] Figure 10 It is a diagram showing the configuration of a power receiving device in the fourth embodiment.

[0020] Figure 11 yes Figure 10 The waveform diagram of each part of the DC-DC converter is shown.

[0021] Figure 12 It is a diagram showing another configuration of the power receiving device in the fourth embodiment.

[0022] Figure 13 It shows Figure 1 The diagram shows an example of a regulator circuit for a DC-DC converter.

[0023] Figure 14 This is a diagram showing an example of a gate signal during overvoltage protection operation.

[0024] Label Description

[0025] 1. 1a: Wireless power supply system; 2: Power transmitting device; 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-side resonator; 24: Power transmitting-side transceiver; 31: Power receiving-side resonator; 32: Rectifier; 33: Power receiving-side transceiver; 41: High-potential side line; 42: Low-potential side line; 51: Overvoltage detection unit; 52: Control unit; 53: Driver; 54: Current detection circuit; 55: Gate resistance switching circuit; 56: Connection disconnection circuit; 57: Regulator circuit; C1: Input capacitor; C2: Output capacitor. DETAILED DESCRIPTION

[0026] Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

[0027] (First embodiment)

[0028] Reference Figure 1 The wireless power supply system 1 of the first embodiment includes a power transmitting device 2 and a power receiving device 3. The power receiving device 3 receives the AC voltage transmitted from the power transmitting device 2 in a contactless manner and outputs the AC voltage to a load 10 such as a battery.

[0029] The power transmission device 2 includes a power supply 21 , an inverter 22 , and a power transmission-side resonator 23 . The power transmission device 2 also includes a power transmission-side transceiver 24 for wirelessly communicating with the power reception device 3 .

[0030] 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 transmission-side resonator 23 .

[0031] The power transmission side resonator 23 includes a power transmission coil L TX ; and the transmission side resonant capacitor C TX , which is connected to the power transmission coil L TX The resonant frequency of the power transmission-side resonator 23 is designed to be a predetermined frequency (eg, several tens of kHz to several tens of MHz) of the AC voltage converted by the inverter 22. The power transmission-side resonator 23 is an example of a resonant circuit and the structure is not particularly limited.

[0032] 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 . Furthermore, the power receiving device 3 includes a power receiving-side transceiver 33 that wirelessly communicates with the power transmitting device 2 .

[0033] The power receiving side resonator 31 includes a power receiving coil L RX ; and the receiving side resonant capacitor C RX , which is connected to the power receiving coil L 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 .

[0034] 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.

[0035] The input capacitor C1 is connected between the high-potential line 41 and the low-potential line 42 , which are output lines of the rectifier 32 , and attenuates the AC component of the output voltage and current of the rectifier 32 .

[0036] The DC-DC converter 5 is a power converter that uses the output voltage of the rectifier 32 as the input voltage V in , the input voltage V in Converted to the desired output voltage V outThe output is then sent to the 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), which are connected in series between a high-potential line 41 and a low-potential line 42. SW1 and SW2 are formed of semiconductor switches such as MOS-FETs (Metal-Oxide-Semiconductor Field-Effect Transistors) or IGBTs (Insulated Gate Bipolar Transistors). Hereinafter, SW1 and SW2 are described as MOS-FETs.

[0037] 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 the inductor L and the output capacitor C2. The voltage between both ends of the output capacitor C2 is the output voltage V out is output.

[0038] 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 the input voltage V in With the preset threshold voltage V th When the input voltage V in is the threshold voltage V th The overvoltage detection unit 51 outputs an overvoltage detection signal OV to the control unit 52, which is low level in normal times (when no overvoltage is detected) and becomes high level when an overvoltage is detected.

[0039] When no overvoltage is detected, the overvoltage detection unit 51 outputs a low-level overvoltage detection signal 0V to the control unit 52, and the control unit 52 controls SW1 and SW2 alternately (complementarily) to turn on and off. Figure 2 As shown in (a), when SW1 is turned on and SW2 is turned off, the output current I flows through the current path through SW1 as shown by the arrow X. out When SW1 is off and SW2 is on, the output current I flows through the current path through SW2 as shown by the arrow Y. out .

[0040] 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 performs an overvoltage protection operation by turning on both SW1 and SW2. Figure 2 As shown by the arrow Z in (b), the protection current I flows through the current path passing through both SW1 and SW2. pro , eliminate overvoltage.

[0041] It is known that when the transmission-side resonator 23 and the reception-side resonator 31 are represented by an equivalent circuit in the wireless power supply system 1, the output of the reception-side resonator 31 has the characteristics of a constant current source (for example, see pages 41-42 of Non-Patent Document 1). Therefore, even if the load 10 changes, the input current I in That is, even if 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 Also through the input current I in In addition, immediately after the overvoltage protection action is executed, the charge stored in the input capacitor C1 is released all at once, so the protection current I pro The peak current is greater than the input current I in big.

[0042] Furthermore, when an overvoltage is detected, the control unit 52 can also transmit an overvoltage notification signal requesting the power transmission device 2 to stop power transmission via the power receiving-side transceiver 33 .

[0043] Figure 3 is the input current I in This is a waveform diagram of each component in the DC-DC converter 5 when the voltage becomes too large.

[0044] When the power transmission coil L TX -Power receiving coil L RX The input current I in When the input voltage V in With input current I in Then, at time t0, the input voltage V in becomes the threshold voltage V th When the voltage is above 0, the overvoltage detection unit 51 detects an overvoltage and changes the overvoltage detection signal OV from a low level to a high level.

[0045] G SW1 , G SW2 Are the gate signals that drive SW1 and SW2 respectively. Gate signal G SW1 , G SW2 Before time t0 when overvoltage is not detected, it is a predetermined complementary signal, and becomes a high level by the overvoltage protection operation when overvoltage is detected.

[0046] By executing the overvoltage protection action, a protection current I is formed through both SW1 and SW2. pro The current path. Input voltage V in By flowing the protection current I proTo drop and eliminate overvoltage. The protection current I flowing through SW1 and SW2 pro The charge stored in the input capacitor C1 causes a large peak current, but when the charge stored in the input capacitor C1 is released, the peak current becomes equal to the input current I in Same value.

[0047] The protection current I flowing through SW2 is monitored by the current detection circuit 54. pro , protection current I pro Less than the preset current threshold I th When the overvoltage protection action is released. Current threshold I th It is set to be higher than the input current I when overvoltage is detected. in0 As a result, the DC-DC converter 5 can automatically recover from the overvoltage protection operation.

[0048] The overvoltage protection operation of the first embodiment described above turns on both SW1 and SW2, which are connected in series between the high-potential line 41 and the low-potential line 42. Therefore, various types of DC-DC converters 5 can be used as long as SW1 and SW2 are connected in series between the high-potential line 41 and the low-potential line 42.

[0049] (Second embodiment)

[0050] Reference Figure 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 buck-boost converter. In addition to the components of the DC-DC converter 5, the DC-DC converter 5a also 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.

[0051] SW3 and SW4 are connected in parallel to the output capacitor C2, and the connection point of SW1 and SW2 is connected to the connection point of 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 line 41 and the low-potential line 42.

[0052] 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 alternately (complementarily) controls the on and off of SW1 and SW2, so that SW3 is always on and SW4 is always off. Figure 5 As shown in (a), when SW1 is turned on and SW2 is turned off, the output current I flows through the current path shown by the arrow Xa through SW1, the inductor L and SW3. outWhen SW1 is off and SW2 is on, the output current I flows in the current path indicated by the arrow Ya through SW2, the inductor L, and SW3. out .

[0053] When an overvoltage is detected, the overvoltage detection unit 51 outputs a high-level overvoltage detection signal OV to the control unit 52. The control unit 52 turns on both SW1 and SW4 and turns off both SW2 and SW3 to perform overvoltage protection. Figure 5 As shown by arrow Za in (b), a protection current I flows through the current path passing through SW1, inductor L and SW4. pro , eliminating overvoltage. In the second embodiment, due to the protection current I pro Since the current flows through the inductor L, the large current immediately after the overvoltage protection operation is performed can be suppressed.

[0054] Figure 6 is the input current I in This is a waveform diagram of each component in the DC-DC converter 5a when the voltage becomes too large.

[0055] When the power transmission coil L TX -Power receiving coil L RX The input current I in When the input voltage V in With input current I in Then, at time t0, the input voltage Vin reaches the threshold voltage V th When the voltage is above 0, the overvoltage detection unit 51 detects an overvoltage and changes the overvoltage detection signal OV from a low level to a high level.

[0056] G SW1 , G SW2 , G SW3 , G SW4 These are the gate signals that drive SW1, SW2, SW3, and SW4 respectively. SW1 , G SW2 Before time t0 when no overvoltage is detected, the gate signal G is a predetermined complementary signal. SW1 Becomes high level, the gate signal G SW2 Becomes low level. Gate signal G SW3 The gate signal G is always high before time t0 when no overvoltage is detected, and becomes low by the overvoltage protection action. SW4 It is always at a low level until time t0 when no overvoltage is detected, and becomes a high level by the overvoltage protection operation.

[0057] By executing the overvoltage protection action, a protection current I flows in the current path through SW1, inductor L and SW4. pro , input voltage V in Since the charge accumulated in the input capacitor C1 is gradually released through the inductor L, the protection current I flowing through SW4 can be suppressed. pro The peak current.

[0058] (Third embodiment)

[0059] Reference Figure 7 In addition to the configuration of the DC-DC converter 5 of the first embodiment, the DC-DC converter 5 b of the third embodiment further includes a gate resistance switching circuit 55 for switching the gate resistances of SW1 and SW2 .

[0060] The gate resistance switching circuit 55 includes, for example, two resistors connected in series, a bypass for short-circuiting one of the resistors, and a switch provided in the bypass. The gate resistance switching circuit 55 is set to a low resistance when the switch is on and to a high resistance when the switch is off.

[0061] When no overvoltage is detected, the overvoltage detector 51 outputs a low-level overvoltage detection signal 0V to the control unit 52. The control unit 52 sets the gate resistance switching circuit 55 to a low resistance and alternately (complementarily) turns on and off SW1 and SW2.

[0062] When overvoltage is detected, the overvoltage detector 51 outputs a high-level overvoltage detection signal 0V to the control unit 52. The control unit 52 sets the gate resistance switching circuit 55 to high resistance and performs an overvoltage protection operation by turning on both SW1 and SW2.

[0063] Figure 8 is the input current I in This is a waveform diagram of each component in the DC-DC converter 5b when the voltage becomes too large.

[0064] When the power transmission coil L TX -Power receiving coil L RX The input current I in When the input voltage V in With input current I in Then, at time t0, the input voltage V in becomes the threshold voltage V th When the voltage is above 0, the overvoltage detection unit 51 detects an overvoltage and changes the overvoltage detection signal OV from a low level to a high level.

[0065] G SW1 , G SW2Are the gate signals that drive SW1 and SW2 respectively. Gate signal G SW1 , G SW2 Before time t0 when no overvoltage is detected, it is a predetermined complementary signal, and becomes high level by the overvoltage protection operation when overvoltage is detected. Since the gate resistance switching circuit 55 is set to low resistance when no overvoltage is detected, the gate signal G SW1 , G SW2 In contrast, when an overvoltage is detected, the gate resistance switching circuit 55 is set to a high resistance, so the gate signal G SW1 , G SW2 That is, the switching speed of SW1 and SW2 during the on-control (when turned on) is set to be faster when no overvoltage is detected, and is set to be slower when an overvoltage is detected.

[0066] In addition, if SW1 or SW2 is already on when an overvoltage is detected, after being turned off (turned off), it is turned on again at a slower switching speed so that both are turned on. Therefore, the gate resistance switching circuit 55 may be provided for only one of SW1 and SW2. For example, Figure 9 As shown, by providing the gate resistance switching circuit 55 only for SW1, it is possible to cope with the situation even when SW1 is already turned on when an overvoltage is detected.

[0067] By executing the overvoltage protection action, the protection current I flows through the current path passing through both SW1 and SW2. pro , input voltage V in The switching current I flowing through SW2 SW2 At this time, since the switching speed of SW1 and SW2 is slow, the charge accumulated in the input capacitor C1 is gradually released, which can suppress the protection current I flowing through SW2. pro The peak current.

[0068] (Fourth embodiment)

[0069] Reference Figure 10 In addition to the configuration of the power receiving device 3 of the first embodiment, the power receiving device 3 c of the fourth embodiment further includes a disconnection circuit 56 that disconnects the electrical connection between the input capacitor C1 and the high-potential line 41 .

[0070] The connection disconnection circuit 56 is comprised of, for example, a disconnection switch connected between the input capacitor C1 and the high-potential line 41. The connection disconnection circuit 56 connects the input capacitor C1 and the high-potential line 41 when the disconnection switch is on, and disconnects the input capacitor C1 and the high-potential line 41 when the disconnection switch is off. Alternatively, the connection disconnection circuit 56 can disconnect the electrical connection between the input capacitor C1 and the low-potential line 42. In this case, the connection disconnection circuit 56 is comprised of a disconnection switch connected between the input capacitor C1 and the low-potential line 42.

[0071] When no overvoltage is detected, the overvoltage detection unit 51 outputs a low-level overvoltage detection signal OV to the control unit 52. The control unit 52 turns on the disconnect switch of the disconnection circuit 56 to connect the input capacitor C1 and the high-potential side line 41, and alternately (complementarily) controls the on and off of SW1 and SW2.

[0072] When an overvoltage is detected, the overvoltage detection unit 51 outputs a high-level overvoltage detection signal OV to the control unit 52. The control unit 52 disconnects the disconnect switch connected to the disconnect circuit 56 to disconnect the input capacitor C1 and the high-potential side line 41, and performs an overvoltage protection action by turning on both SW1 and SW2.

[0073] Figure 11 is the input current I in This is a waveform diagram of each component in the DC-DC converter 5 when the voltage becomes too large.

[0074] When the power transmission coil L TX -Power receiving coil L RX The input current I in When the input voltage V in With input current I in Then, at time t0, the input voltage V in becomes the threshold voltage V th When the voltage is above 0, the overvoltage detection unit 51 detects an overvoltage and changes the overvoltage detection signal OV from a low level to a high level.

[0075] Gate signal G SW1 , G SW2 Before time t0 when no overvoltage is detected, the signal is a complementary signal. When an overvoltage is detected, the overvoltage protection is activated, and a protection current I flows through the current path passing through both SW1 and SW2. pro , input voltage V in Furthermore, by executing the overvoltage protection action, the input capacitor C1 is disconnected from the high potential side line 41 by the connection disconnection circuit 56. Therefore, the charge accumulated in the input capacitor C1 will not be used as the protection current I prois released, thus suppressing the protection current I pro The peak current.

[0076] The disconnection circuit 56 is Figure 12 Even if the structure of the second embodiment is added as shown in the power receiving device 3d, the same effect can be obtained.

[0077] As described above, the first to fourth embodiments employ a method capable of suppressing the protection current I pro The peak current structure, but when the overvoltage protection is activated, only SW2 or both SW1 and SW2 are controlled to make the input voltage V in In this case, the protection current I can be suppressed in the same manner as in the first to fourth embodiments. pro The peak current.

[0078] In the first to fourth embodiments, the DC-DC converters 5 to 5b may be configured as follows. Figure 13 The DC-DC converter 5e shown in FIG. 1 has a regulator circuit 57, which receives power from a load 10 such as a battery. The regulator circuit 57 is an internal power supply that supplies power to various parts of the DC-DC converter 5e. During the overvoltage protection operation, the input voltage V in Although the voltage becomes 0 V, the power supply to the control unit 52 of the DC-DC converters 5 to 5 b can be continued by providing the regulator circuit 57 .

[0079] In the first to fourth embodiments, when the overvoltage protection is activated, 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 flow the protection current I pro In the overvoltage protection action, such as Figure 14 As shown, the period in which both SW1 and SW2 (SW4) are turned on may be intermittently realized.

[0080] Figure 14 The gate signal G is shown when the overvoltage protection operation starts at time t0 and is released at time t1. SW1 , G SW2 In the overvoltage protection operation when the overvoltage detection signal OV is high, the gate signal G SW2 The on timing of SW1 and SW2 (SW4) is advanced to form a period Ta during which both SW1 and SW2 (SW4) are on. In addition, a gate resistance switching circuit 55 is provided for SW2, and the gate signal G during the overvoltage protection operation is SW2 Thus, when both SW1 and SW2 (SW4) are intermittently turned on, the protection current I is suppressed. proThe structures of the second to fourth embodiments may be used.

[0081] As described above, this embodiment is a wireless power supply system 1, which includes: a power transmission device 2; and a power receiving device 3, which receives the AC voltage transmitted from the power transmission device 2 in a contactless manner. The power receiving device 3 includes: a rectifier 32, which converts the received AC voltage into a DC voltage and outputs it between the high-potential side line 41 and the low-potential side line 42; an input capacitor C1, which smoothes the output of the rectifier 32; and a DC-DC converter 5, which uses the DC voltage smoothed by the input capacitor C1 as an input voltage V in , controls the on and off of two or more switching elements SW1 and SW2 to increase the input voltage V in Converted to the desired output voltage V out And output to the load; and an overvoltage detection unit 51, which detects the input voltage V in When the overvoltage is detected by the overvoltage detection unit 51, the DC-DC converter 5 controls the switching elements SW1 and SW2 to form a protection current I between the high potential side line 41 and the low potential side line 42. pro The overvoltage protection of the current path is activated.

[0082] According to this configuration, since the overvoltage protection operation can be executed using SW1 and SW2 of the DC-DC converter 5 included in the power receiving device 3 , overvoltage protection on the power receiving side can be achieved without adopting a special circuit configuration.

[0083] Furthermore, according to this embodiment, the DC-DC converter 5 includes a current detection circuit 54 that monitors the protection current I pro When the current detection circuit 54 detects the protection current I pro When the current is less than a preset current threshold, the DC-DC converter 5 cancels the overvoltage protection action.

[0084] According to this configuration, the DC-DC converter 5 can automatically recover from the overvoltage protection operation.

[0085] In addition, according to this embodiment, when the protection current I pro The current path is configured with an inductor L.

[0086] According to this configuration, the charge accumulated in the input capacitor C1 can be gradually discharged, thereby suppressing the protection current I pro The peak current.

[0087] Furthermore, according to this embodiment, the DC-DC converter 5 includes a gate resistance switching circuit 55 as a switching speed switching circuit for switching the switching speeds of the switching elements SW1 and SW2. During the overvoltage protection operation, the gate resistance switching circuit 55 reduces the switching speeds of the switching elements SW1 and SW2 that are controlled to be turned on.

[0088] According to this configuration, the charge accumulated in the input capacitor C1 can be gradually discharged, thereby suppressing the protection current I pro The peak current.

[0089] Furthermore, according to the present 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 detector 51 detects an overvoltage, the DC-DC converter 5 disconnects the electrical connection between the high-potential-side line 41 or the low-potential-side line 42 and the input capacitor C1 via the disconnection circuit 56.

[0090] According to this configuration, the peak current caused by the charge accumulated in the input capacitor C1 disappears, and thus the protection current I pro The peak current.

[0091] Furthermore, according to this embodiment, the DC-DC converter 5 controls the resistance of the switching elements SW1 and SW2 that are controlled to be turned on during the overvoltage protection operation so that the input voltage V in Become a constant pressure.

[0092] According to this configuration, the power supply of the DC-DC converter 5 can be ensured during the overvoltage protection operation.

[0093] Furthermore, according to this embodiment, the DC-DC converter 5 intermittently generates the protection current I pro current path.

[0094] According to this configuration, the timing of the gate signal in normal operation is changed, thereby ensuring the power supply of the DC-DC converter 5 during the overvoltage protection operation.

[0095] Furthermore, according to the present embodiment, the DC-DC converter 5 includes a regulator circuit 57 , and the regulator circuit 57 receives power supply from the load 10 .

[0096] According to this configuration, the power supply of the DC-DC converter 5 can be ensured during the overvoltage protection operation.

[0097] The present invention is not limited to the above-described embodiments, and it is understood that the embodiments can be appropriately modified within the scope of the technical concept of the present invention. Furthermore, the number, position, and shape of the above-described components are not limited to the above-described embodiments, and may be any number, position, and shape suitable for implementing the present invention. In the accompanying drawings, identical components are denoted by the same reference numerals.

Claims

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

2. The wireless power supply system according to claim 1, wherein: The DC-DC converter has a current detection circuit that monitors the protection current. When the current detection circuit detects that the protection current is less than a preset current threshold, the DC-DC converter cancels the overvoltage protection action.

3. The wireless power supply system according to claim 1 or 2, characterized in that: An inductor is arranged in the current path.

4. The wireless power supply system according to claim 1 or 2, characterized in that: The DC-DC converter includes a switching speed switching circuit that switches the switching speed of the switching element. During the overvoltage protection operation, the switching speed of the switching element that performs on-control is reduced by the switching speed switching circuit.

5. The wireless power supply system according to claim 1 or 2, characterized in that: The power receiving device includes a connection cutoff circuit that cuts off the electrical connection between the high-potential side line or the low-potential side line and the input capacitor. When the overvoltage is detected by the overvoltage detection unit, the DC-DC converter cuts off the electrical connection between the high-potential side line or the low-potential side line and the input capacitor using the connection cutoff circuit.

6. The wireless power supply system according to claim 1 or 2, characterized in that: The DC-DC converter controls the resistance of the switching element that is controlled to be 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, characterized in that: The DC-DC converter intermittently forms the current path.

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

9. A power receiving device that receives an AC voltage transmitted from a power transmitting device in a contactless manner, characterized in that: The power receiving device comprises: a rectifier, which converts the received AC voltage into a DC voltage and outputs the DC voltage between the high-potential side line and the low-potential side line; an input capacitor that smoothes the output of the rectifier; a DC-DC converter that receives the DC voltage smoothed by the input capacitor as an input voltage and controls on and off two or more switching elements to convert the input voltage into a desired output voltage; as well as an overvoltage detection unit for detecting an overvoltage of the input voltage, When the overvoltage is detected by the overvoltage detection unit, the DC-DC converter performs an overvoltage protection operation by controlling the switching element to be turned on to form 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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