Power reception device

Abstract

A power reception device (100) receives AC power in a non-contact manner by means of a magnetic field. The power reception device comprises a resonance circuit (110), a synchronous rectification circuit (120), a load device (130), and a control circuit (150), wherein the control circuit executes a power supply mode (M1) in which DC power is output from the synchronous rectification circuit in a half cycle of the AC power, and a short-circuit mode (M2) in which a high-potential-side second switch (SwLH), which is a second switch to which a voltage is applied in the reverse direction of a parallel diode (Di) among a plurality of second switches (SwL) in a plurality of leg circuits, is controlled to be in an on-state, and controls a low-potential-side second switch (SwLL), which is a second switch through which a current flows to the parallel diode, among the plurality of second switches in the short-circuit mode, to be in an on-state for a first period shorter than one cycle and longer than a half cycle of the AC power.

Description

Powered Device CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based on and claims the benefit of priority from patent application serial number 2024-002917, filed January 12, 2024, the entire contents of which are incorporated herein by reference.

[0002] The present disclosure relates to a power receiving device.

[0003] For power receiving devices used in vehicle contactless power transfer systems, there is a technology that uses a switch in a rectifier circuit, as disclosed in Patent Document 1. The rectifier circuit of Patent Document 1 rectifies AC power received by a resonant circuit including a power receiving coil, thereby supplying DC power to a load device. The rectifier circuit of Patent Document 1 uses a switch to short-circuit the output section of the resonant circuit, which is also the input section of the rectifier circuit. The received power is not supplied to the load device. In other words, the technology of Patent Document 1 can control the power supplied to the load device by using the switch in the rectifier circuit.

[0004] The rectifier circuit of Patent Document 1 is configured with a circuit in which a switch is connected in series to the anode side of a diode. Furthermore, the output part of the resonant circuit is connected between the diode and the switch in the rectifier circuit. The rectifier circuit of Patent Document 1 short-circuits the output part of the resonant circuit by turning on the switch while the diode is conducting.

[0005] Patent No. 6240503

[0006] However, the above technology has the following problem. When the diode is conducting, a voltage is applied to the switch that is in the off state. When the switch is turned on, the switch changes from a voltage-applied state to an on state. In other words, the switch generates switching loss due to hard switching.

[0007] Furthermore, when a current flows through a switch, the forward current of the diode drops sharply, which increases the recovery current that causes losses during switching.

[0008] That is, when controlling the power supplied to the load device by using the switches of the rectifier circuit, a large loss occurs during switching, which has been a problem.

[0009] The present disclosure can be realized in the following aspects. According to a first aspect of the present disclosure, there is provided a power receiving device that receives AC power contactlessly using a magnetic field. The power receiving device includes a resonant circuit having a predetermined resonant frequency and including a power receiving coil that receives the AC power, a plurality of leg circuits, the resonant circuit including a resonant circuit having a predetermined resonant frequency and including a power receiving coil that receives the AC power, a synchronous rectifier circuit that rectifies the AC power to DC power, a load device that consumes the DC power, and a control circuit that controls the power receiving device, each of the plurality of leg circuits being configured by connecting a rectifier diode or a first switch and a second switch in series, the first switch and the second switch each including a parallel diode connected in parallel, and the leg circuit is configured such that the anode of the rectifier diode or the parallel diode of the first switch is connected to the cathode of the parallel diode of the second switch. an output section of the resonant circuit is connected between the rectifier diode or the first switch and the second switch in the leg circuit, and the control circuit executes a power supply mode in which the DC power is output from the synchronous rectifier circuit during a half cycle of the AC power, and a short-circuit mode in which a high-potential side second switch, which is a second switch to which a voltage is applied in the reverse direction of the parallel diode, among the plurality of second switches in the plurality of leg circuits, is controlled to an on state, and controls a low-potential side second switch, which is a second switch through which a current flows in the parallel diode, among the plurality of second switches in the short-circuit mode, to an on state for a first period shorter than one cycle of the AC power and longer than the half cycle.

[0010] With this configuration, the low-potential-side second switch, through which current flows in the parallel diode, remains on as the current of the AC power reversals. That is, the short-circuit mode is implemented in response to the reversal of the current of the AC power. Therefore, when the low-potential-side second switch is turned on, zero-voltage switching is performed, reducing switching loss. Furthermore, the short-circuit mode is implemented when the rectifier diode or the parallel diode of the first switch is not conducting. As a result, recovery current is unlikely to occur in the rectifier diode or the parallel diode of the first switch when the short-circuit mode is implemented. Therefore, the power receiving device of the present disclosure can prevent large losses during switching when controlling the power supplied to the load device in the short-circuit mode.

[0011] The above and other objects, features, and advantages of the present disclosure will become more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which Fig. 1 is an explanatory diagram showing the configuration of a contactless power transfer system according to a first embodiment, Fig. 2 is a switch timing chart, Fig. 3 is an explanatory diagram showing the operation of a synchronous rectifier circuit in mode A, Fig. 4 is an explanatory diagram showing the operation of a synchronous rectifier circuit in mode B, Fig. 5 is an explanatory diagram showing the operation of a synchronous rectifier circuit in mode C, Fig. 6 is an explanatory diagram showing the operation of a synchronous rectifier circuit in mode D, Fig. 7 is an explanatory diagram showing the operation of a synchronous rectifier circuit in mode DE, Fig. 8 is an explanatory diagram showing the operation of a synchronous rectifier circuit in mode E, Fig. 9 is an explanatory diagram showing the operation of a synchronous rectifier circuit in mode F, and Fig. 10 is an explanatory diagram showing the operation of a synchronous rectifier circuit in mode G. 11 is an explanatory diagram showing the operation of the synchronous rectifier circuit in mode H, FIG. 12 is an explanatory diagram showing the operation of the synchronous rectifier circuit in mode HA, FIG. 13 is an explanatory diagram showing the configuration of a contactless power supply system of the second embodiment, FIG. 14 is an explanatory diagram showing the configuration of a contactless power supply system of the third embodiment, FIG. 15 is an explanatory diagram showing the configuration of a contactless power supply system of the fourth embodiment, FIG. 16 is an explanatory diagram showing a resonance method of a modified example, FIG. 17 is an explanatory diagram showing a resonance method of a modified example, FIG. 18 is an explanatory diagram showing a resonance method of a modified example, FIG. 19 is an explanatory diagram showing a resonance method of a modified example, FIG. 20 is an explanatory diagram showing the configuration of a filter circuit, and FIG. 21 is an explanatory diagram showing the configuration of a filter circuit.

[0012] A. First Embodiment: A-1. Device Configuration: A contactless power transfer system 10 shown in Fig. 1 supplies power to a load device 130 in a contactless manner using a magnetic field. As shown in Fig. 1, the contactless power transfer system 10 includes a power transmission device 200 and a power receiving device 100. The contactless power transfer system 10 supplies power from the power transmission device 200 to the power receiving device 100 in a contactless manner. The contactless power transfer system 10 supplies power in a contactless manner to the power receiving device 100 mounted on a vehicle, for example.

[0013] The power transmitting device 200 uses a magnetic field to contactlessly supply AC power to the power receiving device 100. The power transmitting device 200 includes an AC power supply device 210 and a power transmitting resonant circuit 220.

[0014] The AC power supply device 210 supplies AC power of a predetermined operating frequency to the power transmitting resonant circuit 220. The AC power supply device 210 includes a power supply circuit and a power transmitting circuit. The power supply circuit is, for example, an AC / DC converter circuit, and converts AC power supplied from a power grid into DC power. The power transmitting circuit is an inverter that converts DC power supplied from the power supply circuit into AC power of the operating frequency. The operating frequency is, for example, 85 kHz, and is set using a predetermined power transmission frequency stipulated by the Radio Law and the like. Note that the resonant frequencies of the power transmitting resonant circuit 220 and the power receiving resonant circuit 110, which will be described later, are frequencies set according to the operating frequency of the AC power supply device 210.

[0015] The power transmitting resonant circuit 220 is magnetically coupled to and resonates with the power receiving coil 111 of the power receiving device 100. The power transmitting resonant circuit 220 includes a power transmitting coil 222 and a power transmitting resonant capacitor 221 connected in series to the power transmitting coil 222. The "power transmitting resonant circuit" is also called a "primary resonant circuit."

[0016] When the power transmitting coil 222 and the power receiving coil 111 are magnetically coupled, the power transmitting resonant capacitor 221 resonates the power transmitting resonant circuit 220 with AC power at the operating frequency of the AC power supply device 210. That is, the capacitance of the power transmitting resonant capacitor 221 is set so that when the power transmitting coil 222 and the power receiving coil 111 are magnetically coupled, the operating frequency and the resonant frequency of the power transmitting resonant circuit 220 approximately match.

[0017] The power transmitting coil 222 generates a magnetic field corresponding to the operating frequency of the AC power supply device 210. Furthermore, the power transmitting coil 222 transmits AC power to the power receiving coil 111 by magnetically coupling with the power receiving coil 111. In other words, the power transmitting coil 222 transmits power contactlessly by utilizing the electromagnetic induction phenomenon.

[0018] The power transmitting coil 222 is used by being laid on the ground, for example. More specifically, the power transmitting coil 222 is laid on the ground in an orientation that allows it to face the power receiving coil 111 mounted on the vehicle.

[0019] The power receiving device 100 receives AC power from the power transmitting device 200 in a contactless manner using a magnetic field. The power receiving device 100 includes a power receiving resonant circuit 110, a synchronous rectifier circuit 120, a load device 130, a control circuit 150, and a smoothing capacitor 140. The power receiving device 100 is mounted on a vehicle, for example, and receives power from a power transmitting coil 222 laid on the ground.

[0020] The power receiving resonant circuit 110 is magnetically coupled to and resonates with the power transmitting coil 222. The power receiving resonant circuit 110 includes a power receiving coil 111 and a power receiving resonant capacitor 112 connected in series to the power receiving coil 111. The "power receiving resonant circuit" is also called a "secondary resonant circuit" or simply a "resonant circuit."

[0021] The power receiving coil 111 is magnetically coupled to the power transmitting coil 222 by receiving the magnetic field emitted by the power transmitting coil 222. The power receiving coil 111 is used in a state facing the power transmitting coil 222, and is thereby subjected to the magnetic field emitted by the power transmitting coil 222. In this way, the power receiving coil 111 is magnetically coupled to the power transmitting coil 222, and thereby receives AC power at the operating frequency of the AC power supply device 210 in a wireless manner.

[0022] When the power receiving coil 111 and the power transmitting coil 222 are magnetically coupled, the power receiving resonant capacitor 112 causes the power receiving resonant circuit 110 to resonate with AC power at the operating frequency of the AC power supply device 210. In other words, the capacitance of the power receiving resonant capacitor 112 is set so that when the power transmitting coil 222 and the power receiving coil 111 are magnetically coupled, the operating frequency of the AC power supply device 210 and the resonant frequency of the power receiving resonant circuit 110 approximately match. Therefore, the power receiving resonant circuit 110 has a resonant frequency that is predetermined according to the operating frequency of the AC power supply device 210.

[0023] In this embodiment, the power receiving resonant capacitor 112 is arranged on the positive side line Lacp of the power receiving resonant circuit 110. The "power receiving resonant capacitor" may also be simply called a "resonant capacitor."

[0024] The synchronous rectifier circuit 120 converts the received AC power into DC power. In this embodiment, the synchronous rectifier circuit 120 is a single-phase rectifier circuit that uses four MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors) as rectifier elements. The synchronous rectifier circuit 120 includes two leg circuits: a first leg circuit 121 and a second leg circuit 122. Note that the "synchronous rectifier circuit" may also be simply referred to as a "rectifier circuit."

[0025] The leg circuit has two switches Sw connected in series. Furthermore, the leg circuit connects the positive line Ldcp and negative line Ldcn of the DC power. One of the output terminals of the power receiving resonant circuit 110 is connected between the two switches Sw of the leg circuit. Therefore, the position of the input terminal of the synchronous rectifier circuit 120 is located between the two switches Sw of the leg circuit. That is, the output section 110o of the power receiving resonant circuit 110 is connected between the first switch SwH and the second switch SwL in the leg circuit. Regarding the input terminals of the synchronous rectifier circuit 120, the leg circuit having the terminal P1 is the first leg circuit 121. The leg circuit having the terminal P2 is the second leg circuit 122. A current due to the received AC power is input to the synchronous rectifier circuit 120 via the terminals P1 and P2.

[0026] Each of the two leg circuits is configured by a series connection of a first switch SwH as a rectifying element on the positive line Ldcp side and a second switch SwL as a rectifying element on the negative line Ldcn side. That is, the switch Sw constitutes all of the rectifying elements in the synchronous rectifier circuit 120.

[0027] The first switch SwH includes a parallel diode Di connected in parallel. The parallel diode Di is, for example, a body diode of a MOSFET. That is, the drain of the first switch SwH is arranged on the positive line Ldcp side, and the source of the first switch SwH is arranged on the negative line Ldcn side. The cathode of the parallel diode Di is connected to the drain. The anode of the parallel diode Di is connected to the source. Furthermore, the gate of the first switch SwH is connected to the control circuit 150. The first switch SwH is driven by receiving a voltage at its gate in response to a command from the control circuit 150.

[0028] The second switch SwL includes a parallel diode Di connected in parallel with the first switch SwH. The parallel diode Di between the second switch SwL and the parallel diode Di between the first switch SwH is configured similarly to the parallel diode Di between the first switch SwH and the parallel diode Di between the first switch SwH.

[0029] That is, in the leg circuit, the cathode of the parallel diode of the second switch SwL is connected to the anode of the parallel diode Di of the first switch SwH.

[0030] In this specification, the "positive line side" is also referred to as the "high side," and the "negative line side" is also referred to as the "low side." Therefore, the "first switch" is also referred to as the "high-side switch," and the "second switch" is also referred to as the "low-side switch."

[0031] The operation of the synchronous rectifier circuit 120 during power conversion will be described in detail later.

[0032] The smoothing capacitor 140 is connected in parallel to the output of the synchronous rectifier circuit 120 and the load device 130. The smoothing capacitor 140 smoothes the DC current and DC voltage supplied to the load device 130.

[0033] The load device 130 consumes DC power. The load device 130 is, for example, a device including a battery and a battery protection circuit. That is, if the load device 130 includes a battery, the load device 130 is charged with DC power output from the synchronous rectifier circuit 120. The power charged in the load device 130 is used, for example, in a vehicle in which the power receiving device 100 is installed.

[0034] The control circuit 150 controls the power receiving device 100. The control circuit 150 includes a control unit 151 and a drive circuit 152.

[0035] The drive circuit 152 drives the switch Sw. More specifically, the drive circuit 152 outputs power required to drive the switch Sw in response to a command from the control unit 151. The drive circuit 152 is connected to the gates of all the switches Sw in the synchronous rectifier circuit 120. The drive circuit 152 drives the switch Sw by applying a gate voltage required for turning the switch Sw on and off to the gate of the switch Sw. Note that in FIG. 1 , the connection between the drive circuit 152 and the gate is omitted to facilitate understanding of the technology.

[0036] The control unit 151 generates a signal that controls the on / off operation of the switch Sw. The control unit 151 is mainly composed of, for example, a microcomputer, and includes a CPU, a ROM, a RAM, etc. (not shown).

[0037] The control unit 151 executes a power supply mode M1 in which DC power is output from the synchronous rectifier circuit 120 during a half cycle of the received AC power, and a short-circuit mode M2 ​​in which DC power is not output from the synchronous rectifier circuit 120. A control method of the power receiving device 100 by the control unit 151 will be described below.

[0038] A-2. Control Method of Power Receiving Device: In the upper part of Fig. 2, a sine wave of the input current of the synchronous rectifier circuit 120 is shown.

[0039] 2, below the sine wave of the input current of the synchronous rectifier circuit 120, timing charts of the gate-source voltages of the high-side switch SwH of the second leg circuit 122, the low-side switch SwL of the second leg circuit 122, the high-side switch SwH of the first leg circuit 121, and the low-side switch SwL of the first leg circuit 121 are shown. In the timing chart of the gate-source voltages, "H" indicates the voltage value required to turn on the switch Sw, and "L" indicates the voltage value required to turn off the switch Sw. Below the timing chart of the gate-source voltages, waveforms of the drain-source voltages of the low-side switch SwL of the second leg circuit 122 and the low-side switch SwL of the first leg circuit 121 are shown. Note that the drain-source voltage waveforms are shown for ease of understanding of the technology, but are waveforms acquired by the first sensor 160 of the second embodiment.

[0040] The control unit 151 controls the power receiving device 100 to one of a plurality of modes using the switch Sw during one cycle of the input current to the synchronous rectifier circuit 120. The multiple modes of the power receiving device 100 will be described in order, starting from the start of the negative half cycle of the input current to the synchronous rectifier circuit 120. Note that in Figures 3 to 12 used to describe the modes of the power receiving device 100, some components such as the power transmitting device 200 and the control circuit 150 are not shown to facilitate technical understanding. Note that the duration of each mode of the multiple modes of the power receiving device 100 will be described later.

[0041] 2 , the control unit 151 controls the low-side switches SwL of the first leg circuit 121 and the second leg circuit 122 to the on state. Furthermore, the control unit 151 controls the high-side switches SwH of the first leg circuit 121 and the second leg circuit 122 to the off state. As a result, the input current of the synchronous rectifier circuit 120 during the period of mode A returns to the power receiving coil 111 via the two low-side switches SwL, as indicated by the arrow Aia in FIG. 3 . In other words, because no DC power is output from the synchronous rectifier circuit 120, no power is supplied to the load device 130.

[0042] 2 , the control unit 151 controls the low-side switch SwL of the second leg circuit 122 to an off state. The control unit 151 maintains the switches Sw other than the low-side switch SwL of the second leg circuit 122 in the same state as in Mode A. As a result, the input current of the synchronous rectifier circuit 120 during Mode B flows to the load device 130 via the parallel diode Di of the high-side switch SwH in the second leg circuit 122 and the low-side switch SwL of the first leg circuit 121, as indicated by the arrow Aib in FIG. 4 . In other words, DC power is output from the synchronous rectifier circuit 120, and power is supplied to the load device 130.

[0043] 2 , the control unit 151 controls the high-side switch SwH of the second leg circuit 122 to an on state. The control unit 151 maintains the switches Sw other than the high-side switch SwH of the second leg circuit 122 in the same state as in Mode B. As a result, the input current of the synchronous rectifier circuit 120 during Mode C flows to the load device 130 via the high-side switch SwH in the second leg circuit 122 and the low-side switch SwL of the first leg circuit 121, as indicated by the arrow Aic in FIG. 5 . In other words, DC power is output from the synchronous rectifier circuit 120, and power is supplied to the load device 130.

[0044] In Mode B of FIG. 2 , a current flows through the parallel diode Di of the high-side switch SwH in the second leg circuit 122, and therefore the drain-source voltage is 0 V. Therefore, when switching from Mode B to Mode C, that is, when the high-side switch SwH of the second leg circuit 122 is controlled to the on state, the high-side switch SwH of the second leg circuit 122 performs switching while the drain-source voltage is 0 V. This reduces switching loss. In other words, the high-side switch SwH of the second leg circuit 122 performs soft switching. This switching method is generally referred to as "zero voltage switching" or "ZVS (Zero Voltage Switching)."

[0045] 2 , the control unit 151 controls the high-side switch SwH of the second leg circuit 122 to an off state. The control unit 151 maintains the switches Sw other than the high-side switch SwH of the second leg circuit 122 in the same state as in Mode C. As a result, the input current of the synchronous rectifier circuit 120 during Mode D flows to the load device 130 via the parallel diode Di of the high-side switch SwH in the second leg circuit 122 and the low-side switch SwL of the first leg circuit 121, as indicated by the arrow Aid in FIG. 6 . In other words, DC power is output from the synchronous rectifier circuit 120, and power is supplied to the load device 130.

[0046] 2 , the current flowing through the high-side switch SwH in the second leg circuit 122 flows between the drain and the source via the parallel diode Di. That is, when transitioning from Mode C to Mode D, the high-side switch SwH in the second leg circuit 122 is controlled to be in the off state when the drain-source voltage is 0 V. Therefore, the high-side switch SwH in the second leg circuit 122 is switched to the off state by zero-voltage switching, thereby reducing switching loss.

[0047] In FIG. 2 , mode DE occurs as a transition from mode D occurs when the input current of the synchronous rectifier circuit 120 reverses from negative to positive. In mode DE, the switch Sw of the synchronous rectifier circuit 120 is in the same state as in mode D. As a result, the input current of the synchronous rectifier circuit 120, which has reversed to positive, begins to flow toward the receiving coil 111 via the low-side switch SwL of the first leg circuit 121 and the parallel diode Di of the low-side switch SwL in the second leg circuit 122, as indicated by arrow Aide in FIG. 7 . At this time, in mode D, the current flowing through the parallel diode Di of the high-side switch SwH of the second leg circuit 122 gradually decreases to 0 A in a sinusoidal manner. Therefore, short-circuit mode M2 ​​is executed when the parallel diode Di of the high-side switch SwH of the second leg circuit 122 is not conducting. That is, loss due to recovery current is unlikely to occur in the parallel diode Di of the high-side switch SwH of the second leg circuit 122.

[0048] 2 , the control unit 151 controls the low-side switch SwL of the second leg circuit 122 to an on state. The control unit 151 maintains the switches Sw other than the low-side switch SwL of the second leg circuit 122 in the same state as in Mode D. As a result, the input current of the synchronous rectifier circuit 120 during Mode E returns to the power receiving coil 111 via the low-side switch SwL of the first leg circuit 121 and the low-side switch SwL of the second leg circuit 122, as indicated by arrow Aie in FIG. 8 . In other words, no DC power is output from the synchronous rectifier circuit 120, and therefore no power is supplied to the load device 130.

[0049] 2 , a current flows through the parallel diode Di of the low-side switch SwL in the second leg circuit 122, and therefore the drain-source voltage is 0 V. Therefore, when switching from mode DE to mode E, that is, when the low-side switch SwL of the second leg circuit 122 is controlled to be in the on state, the low-side switch SwL of the second leg circuit 122 performs switching while the drain-source voltage is 0 V. That is, the low-side switch SwL of the second leg circuit 122 switches to the on state by zero-voltage switching, thereby reducing switching loss.

[0050] 2 , the control unit 151 controls the low-side switch SwL of the first leg circuit 121 to an off state. The control unit 151 maintains the switches Sw other than the low-side switch SwL of the first leg circuit 121 in the same state as in Mode E. As a result, the input current of the synchronous rectifier circuit 120 during Mode F flows to the load device 130 via the parallel diode Di of the high-side switch SwH in the first leg circuit 121 and the low-side switch SwL of the second leg circuit 122, as indicated by the arrow Aif in FIG. 9 . In other words, DC power is output from the synchronous rectifier circuit 120, and power is supplied to the load device 130.

[0051] 2 , the control unit 151 controls the high-side switch SwH of the first leg circuit 121 to an on state. The control unit 151 maintains the switches Sw other than the high-side switch SwH of the first leg circuit 121 in the same state as in Mode F. As a result, the input current of the synchronous rectifier circuit 120 during Mode G flows to the load device 130 via the high-side switch SwH in the first leg circuit 121 and the low-side switch SwL of the second leg circuit 122, as indicated by the arrow Aig in FIG. 10 . In other words, DC power is output from the synchronous rectifier circuit 120, and power is supplied to the load device 130.

[0052] 2 , a current flows through the parallel diode Di of the high-side switch SwH in the first leg circuit 121, and therefore the drain-source voltage is 0 V. Therefore, when switching from mode F to mode G, that is, when the high-side switch SwH of the second leg circuit 121 is controlled to the on state, the high-side switch SwH of the second leg circuit 122 performs switching while the drain-source voltage is 0 V. That is, the high-side switch SwH of the second leg circuit 122 switches to the on state by zero-voltage switching, thereby reducing switching loss.

[0053] 2 , the control unit 151 controls the high-side switch SwH of the second leg circuit 122 to an off state. The control unit 151 maintains the switches Sw other than the high-side switch SwH of the second leg circuit 122 in the same state as in Mode G. As a result, the input current of the synchronous rectifier circuit 120 during Mode H flows to the load device 130 via the high-side switch SwH of the first leg circuit 121 and the low-side switch SwL of the second leg circuit 122, as indicated by arrow Aih in FIG. 11 . In other words, DC power is output from the synchronous rectifier circuit 120, and power is supplied to the load device 130.

[0054] 2 , the current flowing through the high-side switch SwH in the first leg circuit 121 flows between the drain and the source via the parallel diode Di. That is, when transitioning from Mode G to Mode H, the high-side switch SwH in the first leg circuit 121 is controlled to be in the off state when the drain-source voltage is 0 V. Therefore, the high-side switch SwH in the first leg circuit 121 is switched to the off state by zero-voltage switching, thereby reducing switching loss.

[0055] 2 , mode HA occurs as a transition from mode H due to the input current of the synchronous rectifier circuit 120 reversing from positive to negative. In mode HA, the switch Sw of the synchronous rectifier circuit 120 is in the same state as in mode H. As a result, the input current of the synchronous rectifier circuit 120, which has been reversed to negative, begins to flow toward the receiving coil 111 via the parallel diode Di of the low-side switch SwL in the first leg circuit 121 and the low-side switch SwL in the second leg circuit 122, as indicated by arrow Aiha in FIG. 12 . At this time, in mode H, the current flowing through the parallel diode Di of the high-side switch SwH in the first leg circuit 121 gradually decreases to 0 A in a sinusoidal manner. Therefore, short-circuit mode M2 ​​is executed when the parallel diode Di of the high-side switch SwH in the first leg circuit 121 is not conducting. That is, in the parallel diode Di of the high-side switch SwH of the first leg circuit 121, loss due to recovery current is unlikely to occur.

[0056] 2 , a current flows through the parallel diode Di of the low-side switch SwL in the first leg circuit 121, and therefore the drain-source voltage is 0 V. Therefore, when switching from mode HA to mode A, that is, when the low-side switch SwL of the first leg circuit 121 is controlled to be in the on state, the low-side switch SwL of the first leg circuit 121 performs switching while the drain-source voltage is 0 V. In other words, the low-side switch SwL of the first leg circuit 121 switches to the on state by zero-voltage switching, thereby reducing switching loss.

[0057] Regarding the above, as shown in the upper part of FIG. 2 , short-circuit mode M2 ​​corresponds to mode A, mode DE, mode E, and mode HA. The other modes correspond to power supply mode M1. In short-circuit mode M2, as shown in FIGS. 3 and 8 , the control unit 151 controls, to an on state, a high-side low-side switch SwLH, which is a low-side switch SwL to which a voltage is applied in the reverse direction of the parallel diode Di of the low-side switch SwL, among the plurality of low-side switches SwL in the plurality of leg circuits. Note that the high-side refers to a leg circuit having an input terminal of the synchronous rectifier circuit 120 with a higher potential, among the two leg circuits. The high-side low-side switch SwLH is the low-side switch SwL in the leg circuit having an input terminal with a higher potential, among the two input terminals P1 and P2 of the synchronous rectifier circuit 120. The “high-side low-side switch” is also referred to as a “high-side second switch.”

[0058] The control unit 151 adjusts the power supplied to the load device 130 by changing the ratio of the short circuit mode M2 ​​to the power supply mode M1 in one cycle. More specifically, the control unit 151 adjusts the power supplied to the load device 130 by changing the ratio of the mode A to the mode C in one half cycle and the ratio of the mode E to the mode G in one half cycle. Thus, the length of the short circuit mode M2 ​​is determined based on the power supplied to the load device 130. For example, the power supplied to the load device 130 is determined in advance before the power receiving device 100 is started up, based on the rated power of the load device 130.

[0059] The times of Mode B, Mode D, Mode F, and Mode H are each determined in advance before the power receiving device 100 is started up as the dead time of the high-side switch SwH and the low-side switch SwL in the same leg circuit.

[0060] Furthermore, as shown in FIGS. 7 and 12 , the control unit 151 controls the low-side low-side switch SwLL, which is one of the multiple low-side switches SwL in the short-circuit mode M2 ​​and through which a current flows in the parallel diode Di, to be in the on state for a first period T1 that is shorter than one cycle and longer than half the cycle of the received AC power. The low-side refers to the leg circuit having the input terminal of the synchronous rectifier circuit 120 with the lower potential, out of the two leg circuits, the input terminal P1 and the input terminal P2 of the synchronous rectifier circuit 120. The low-side low-side switch SwLL is the low-side switch SwL in the leg circuit having the input terminal with the lower potential, out of the two input terminals P1 and P2 of the synchronous rectifier circuit 120. The “low-side low-side switch” is also referred to as the “low-side second switch.” That is, the control unit 151 controls the low-side low-side switch SwLL to be in the on state for a period longer than half the cycle in the short-circuit mode M2, thereby maintaining the on state until the next short-circuit mode M2. As a result, the low-side switch SwLL, which is controlled to be in the on state in the short-circuit mode M2, continues to be in the on state until the current reverses. Therefore, in response to the current reversal, the low-side switch SwLL functions as the high-side switch SwLH and starts the short-circuit mode M2 ​​by zero-voltage switching.

[0061] 2, the start time T1s of the first period T1 is the time point at which the low-side switch SwLL, which is in the OFF state, is controlled to be in the ON state. The length of the first period T1 is shorter than one cycle and longer than half the cycle of the operating frequency of the AC power supply device 210, and is determined in advance before the power receiving device 100 is started up based on the power supplied to the load device 130 as described above.

[0062] In the power supply mode M1, as shown in FIGS. 3 , 4 , 8 , and 9 , when the control unit 151 controls the high-side switch SwLH in the leg circuit including the high-side low-side switch SwLH in the ON state to the OFF state among the multiple low-side switches SwL in the short-circuit mode M2, the control unit 151 controls the high-side switch SwH in the leg circuit including the high-side low-side switch SwLH in the ON state to be in the OFF state. Furthermore, after controlling the high-side low-side switch SwLH in the ON state to the OFF state, the control unit 151 controls the high-side switch SwH in the OFF state to be in the ON state for the second period T2, as shown in FIGS. 5 and 10 . That is, when transitioning from the short-circuit mode M2 ​​to the power supply mode M1, the control unit 151 turns the high-side switch SwH in the OFF state and rectifies the current via the parallel diode Di. Therefore, in the synchronous rectifier circuit 120, when the high-side switch SwH is controlled to the ON state, zero voltage switching is performed, thereby reducing switching loss.

[0063] 2 has an end T2e that is a time period from the start T1s of the first period T1 that is longer than the first period T1 and shorter than one cycle of the operating frequency of the AC power supply device 210. The length of the second period T2 is determined in advance before the power receiving device 100 is started up, based on the first period T1 and the mode dead time from the end T1e of the first period T1 to the start T2s of the second period T2.

[0064] With this configuration, the low-side second switch SwLL, through which current flows in the parallel diode Di, remains in the on state, and current flows in the switch Sw as the current of the AC power reverses. That is, the short-circuit mode M2 ​​is executed in response to the reversal of the current of the AC power. Therefore, when the low-side second switch SwLL is turned on, zero-voltage switching is performed, reducing switching loss. Furthermore, the short-circuit mode M2 ​​is executed when the parallel diode Di of the first switch SwH is not conducting. As a result, a recovery current is unlikely to occur in the parallel diode Di of the first switch SwH when the short-circuit mode M2 ​​is executed. Therefore, the power receiving device 100 of the present disclosure can prevent large losses during switching when controlling the power supplied to the load device 130 in the short-circuit mode M2.

[0065] Furthermore, with this configuration, a current flows through the first switch SwH when the high-side low-side switch SwLH is turned off. Because the first switch SwH is in the off state, the current flows through the parallel diode Di. As a result, when the first switch SwH is turned on, zero-voltage switching is performed, reducing switching loss. Therefore, the power receiving device 100 of the present disclosure can reduce switching loss in the power supply mode M1 compared to a configuration in which the first switch SwH is turned on by hard switching.

[0066] Furthermore, with this configuration, the short-circuit mode M2 ​​is executed based on a period corresponding to the resonant frequency without detecting the period of the AC power. Therefore, the power receiving device 100 of the present disclosure can reduce the cost required for the power receiving device 100 compared to a configuration including a sensor that detects the period of the AC power. Furthermore, with this configuration, the first switch SwH is controlled to the off state after the second period in a state in which a forward voltage is applied to the first parallel diode. As a result, when the first switch SwH is controlled to the off state, zero-voltage switching can be performed, thereby reducing switching loss.

[0067] B. Second Embodiment As shown in FIG. 13, a power receiving device 100a of the second embodiment includes a first sensor 160 in addition to the configuration of the first embodiment.

[0068] The first sensor 160 detects the voltage of the rectifying element of the synchronous rectifier circuit 120. In other words, the first sensor 160 is a voltage sensor. The first sensor 160 is connected to both ends of the drain and source of the low-side switch SwL. The first sensor 160 detects the falling edge Vf of the voltage across both ends of the low-side switch SwL, with respect to the voltages of the two leg circuits. The falling edge Vf of the voltage is illustrated in FIG. 2. The first sensor 160 transmits the acquired information to the control unit 151a.

[0069] Other configurations of the contactless power supply system 10a of the second embodiment are the same as those of the contactless power supply system 10 of the first embodiment. Note that, in the configuration of the contactless power supply system 10a of the second embodiment, configurations that are different from the configuration of the contactless power supply system 10 of the first embodiment are designated by the reference numerals suffixed with "a."

[0070] The control unit 151a of the second embodiment executes the short-circuit mode M2 ​​on the condition that the first sensor 160 detects a voltage falling edge Vf. For example, as shown in the lower part of FIG. 2 , the control unit 151a of the second embodiment detects a voltage falling edge Vf in the low-side switch SwL of the second leg circuit 122. After confirming that the short-circuit mode M2 ​​is being properly implemented, the control unit 151a of the second embodiment controls the low-side switch SwL of the second leg circuit 122 to the on state during the first period T1. The control unit 151a of the second embodiment similarly controls the low-side switch SwL of the first leg circuit 121.

[0071] By adopting such a configuration, the power receiving device 100a of the second embodiment can control the synchronous rectifier circuit 140 more stably than a configuration that does not include the first sensor 160. Furthermore, voltage sensors are generally cheaper than current sensors. Therefore, the power receiving device 100a of the present disclosure can reduce the cost of the device compared to a configuration in which the first sensor 160 is configured as a current sensor.

[0072] Furthermore, in this configuration, the high-side switch SwH is turned on and off in a period shorter than one cycle. For example, if the high-side switch SwH is simply driven by a signal that is the inverse of that of the low-side switch SwL, and the high-side switch SwH is unable to properly detect the voltage rising and falling waveforms, the high-side switch SwH will remain in the on state. This may result in the next voltage rising and falling being prevented, making it impossible to execute the short-circuit mode or the power supply mode. However, in the power receiving device 100a of the present disclosure, the high-side switch SwH is turned off in a period shorter than one cycle, so such concerns do not arise and the device can operate stably.

[0073] C. Third Embodiment: As shown in FIG. 14 , a power receiving device 100b of the third embodiment includes, in addition to the configuration of the first embodiment, a second sensor 170 that acquires the actual period of the current of AC power. The second sensor 170 is provided in the power receiving resonant circuit 110, acquires the actual period of the current flowing through the power receiving resonant circuit 110, and transmits it to the control unit 151b. The "period acquired by the second sensor 170" is referred to as the "actual period." In the first embodiment, the first period T1 and the second period T2 are determined in advance based on one period of the operating frequency of the AC power supply device 210. However, in the third embodiment, the first period T1 and the second period T2 are determined based on the actual period.

[0074] Other configurations of the contactless power supply system 10b of the third embodiment are the same as the configurations of the contactless power supply system 10 of the first embodiment. Note that, in the configuration of the contactless power supply system 10b of the third embodiment, configurations that are different from the configuration of the contactless power supply system 10 of the first embodiment are designated by the reference numerals suffixed with "b."

[0075] By adopting this configuration, the short circuit mode M2 ​​and the power supply mode M1 are executed based on the actual cycle. By performing control based on the cycle of the actually acquired AC power, the power receiving device 100 of the present disclosure can stably execute the short circuit mode M2 ​​and the power supply mode M1 compared to a configuration in which control is performed without detecting the cycle of the AC power.

[0076] D. Fourth Embodiment In the above embodiments, all rectifying elements in the synchronous rectifier circuit 120 are configured as switches Sw. However, as in the synchronous rectifier circuit 120c of the fourth embodiment shown in FIG. 15 , only the low-side rectifying elements may be configured as switches Sw. That is, in the synchronous rectifier circuit 120c of the fourth embodiment, the high-side rectifying elements are configured as rectifying diodes Di. In the synchronous rectifier circuit 120c of the fourth embodiment, the short-circuit mode M2 ​​is implemented by the low-side switch SwL, and therefore the short-circuit mode M2 ​​can be implemented as long as only the low-side rectifying elements are configured as switches Sw. That is, the control circuit 150c of the fourth embodiment controls only the low-side switch SwL.

[0077] Other configurations of the contactless power supply system 10c of the fourth embodiment are the same as the configurations of the contactless power supply system 10 of the first embodiment. Note that, in the configuration of the contactless power supply system 10c of the fourth embodiment, configurations that are different from the configuration of the contactless power supply system 10 of the first embodiment are designated by the reference numerals having the suffix "c".

[0078] Therefore, even in this configuration, the power receiving device 100c of the present disclosure can prevent large losses from occurring during switching when controlling the power supplied to the load device 130 in the short-circuit mode M2. Furthermore, the rectifier diode Di is less likely to generate a recovery current when the short-circuit mode M2 ​​is executed. Furthermore, since the power required to control the switch Sw is reduced, the rated power of the control circuit 150 can be reduced. In other words, the power receiving device 100c of the present disclosure can be made more compact than a configuration in which all rectifying elements are configured using the switch Sw.

[0079] E. Modification 1: In the above embodiment, an example was shown in which a resonance method using the power transmitting resonant circuit 220, which is a series resonant circuit, and the power receiving resonant circuit 110, which is also a series resonant circuit, was applied, as shown in Fig. 1. In contrast to this, the following resonance method can also be applied. However, to facilitate understanding of the technology, Figs. 16 to 19 only show configurations corresponding to the power transmitting resonant circuit 220 and the power receiving resonant circuit 110 in the first embodiment.

[0080] As shown in Fig. 16 , the power transmitting resonant circuit 220c may be a parallel resonant circuit in which a power transmitting resonant capacitor 221c is connected in parallel to the power transmitting coil 222, and the power receiving resonant circuit 110 may be the same series resonant circuit as in the first embodiment. Also, as shown in Fig. 17 , the power transmitting resonant circuit 220d may be a circuit in which a power transmitting resonant capacitor 221d is connected in series to the power transmitting coil 222 and another power transmitting resonant capacitor 221 is connected in parallel to the series-connected power transmitting resonant capacitor 221 and the power transmitting coil 222. In this case, the power receiving resonant circuit 110 is the same series resonant circuit as in the first embodiment. Also, as shown in Fig. 18 , the power transmitting device 200e may further be provided with a tertiary resonant circuit 310 that is independent of the power transmitting resonant circuit 220e and in which a tertiary coil 311 and a tertiary resonant capacitor 312 are connected in series. The tertiary resonant circuit 310 is arranged so that the tertiary coil 311 is magnetically coupled to both the power transmitting coil 222 and the power receiving coil 111. Also, as shown in FIG. 19 , a power transmitting device 220f may have a tertiary resonant circuit 310f in which a tertiary coil 311e and a tertiary resonant capacitor 312f are connected in parallel and connected in series to the power transmitting coil 222f. The tertiary resonant circuit 310f is arranged so that the tertiary coil 311f is magnetically coupled to both the power transmitting coil 222f and the power receiving coil 111. In a configuration in which the tertiary resonant circuit 310f is provided, the power receiving resonant circuit 110 is the same series resonant circuit as in the first embodiment.

[0081] F. Modification 2: In the above embodiment, the power receiving device 100 may include a filter circuit between the power receiving resonant circuit 110 and the synchronous rectifier circuit 120. More specifically, the power receiving device 100 may include an immittance filter, such as the filter circuit FL1 in FIG. 20 or the filter circuit FL2 in FIG. 21. The power receiving device 100 may include a band-pass filter in addition to the immittance filter. Note that some components, such as the smoothing capacitor 140 and the power receiving resonant circuit 110, are omitted from the illustration in FIGS. 20 and 21.

[0082] G. Modification 3: (1) In the above embodiment, the first sensor 160 is a voltage sensor. However, the first sensor 160 may be a current sensor that detects the output current of the synchronous rectifier circuit 120. The current sensor is connected in series with the synchronous rectifier circuit 120 and the load device 130. The current sensor transmits information about the output current of the synchronous rectifier circuit 120 to the control unit 151. The control unit 151 adjusts the period of the short-circuit mode M2 ​​using the first sensor 160 based on, for example, a predetermined amount of power supplied to the load device 130. (2) In the above embodiment, the first sensor 160 detects a voltage falling edge Vf. The control unit 151 executes the short-circuit mode M2 ​​on the condition that the first sensor 160 detects the voltage falling edge Vf. However, the first sensor 160 may be provided between the drain and source of the high-side switch SwH to detect a rising edge of the voltage across both ends of the high-side switch SwH. That is, the control unit 151 may execute the short-circuit mode M2 ​​on the condition that the first sensor 160 detects a rise in voltage. (3) In the first embodiment, the power receiving resonant capacitor 111RC includes only a positive-side resonant capacitor 111RCp arranged on the positive-side line Lacp of the power receiving resonant circuit 110. However, the power receiving resonant capacitor 111RC may also include a negative-side resonant capacitor arranged on the negative-side line Lacn of the power receiving resonant circuit 110. This suppresses common-mode noise. (4) In the above embodiment, the switch Sw of the synchronous rectifier circuit 120 is a MOSFET. However, the switch Sw of the synchronous rectifier circuit 120 may be another switching element. The switch Sw may be, for example, a BJT (bipolar junction transistor) or an IGBT (insulated gate bipolar transistor). (5) In the above embodiment, the synchronous rectifier circuit 120 is configured with two leg circuits. However, the synchronous rectifier circuit 120 may be configured with two or more leg circuits. For example, the synchronous rectifier circuit 120 may be configured with three leg circuits and may be a circuit that rectifies three-phase AC power. (6) In the above embodiment, the power supplied to the load device 130 is determined in advance before the power receiving device 100 is started up, based on the rated power of the load device 130.However, the power supplied to the load device 130 may be changed according to the acquired current value, for example, by providing the power receiving device 100 with a current sensor that acquires the current flowing through the load device 130. More specifically, the control unit 151 determines the power to be supplied to the load device 130 based on the acquired current value, and adjusts the first period T1 according to the rated power of the load device 130. This allows the power receiving device 100 to efficiently supply power to the load device 130 even when the received AC power fluctuates.

[0083] The present disclosure is not limited to the above-described embodiments and modifications, and can be realized in various configurations without departing from the spirit thereof. For example, the technical features in the embodiments and modifications corresponding to the technical features in each aspect described in the Summary of the Disclosure section can be appropriately replaced or combined to solve some or all of the above problems or achieve some or all of the above effects. Furthermore, if a technical feature is not described as essential in this specification, it can be deleted as appropriate.(Mode 1) A power receiving device (100, 100a, 100b, 100c) that receives AC power contactlessly by a magnetic field, comprising: a resonant circuit (110) having a predetermined resonant frequency, the resonant circuit including a power receiving coil (111) that receives the AC power; a synchronous rectifier circuit (120) that is configured with a plurality of leg circuits (121, 121c, 122, 122c) and rectifies the AC power to DC power; a load device (130) that consumes the DC power; and a control circuit (150, 150a, 150b, 150c) that controls the power receiving device, wherein each leg circuit of the plurality of leg circuits is configured by a series connection of a rectifier diode (Di) or a first switch (SwH) and a second switch (SwL), and the first switch and the second switch each comprise a parallel diode (Di) connected in parallel, the leg circuit is connected such that the cathode of the parallel diode of the second switch is connected to the anode of the rectifier diode or the parallel diode of the first switch, and the output unit (110o) of the resonant circuit is connected in the leg circuit between the rectifier diode or the first switch and the second switch, and the control circuit executes, in a half cycle of the AC power, a power supply mode (M1) in which the DC power is output from the synchronous rectifier circuit, and a short-circuit mode (M2) in which a high-potential side second switch (SwLH) is controlled to an on state, the high-potential side second switch (SwLH) being a second switch to which a voltage is applied in the reverse direction of the parallel diode, among the plurality of second switches in the plurality of leg circuits, and the short-circuit mode controls a low-potential side second switch (SwLL) being a second switch through which a current flows in the parallel diode, among the plurality of second switches, to an on state, for a first period that is shorter than one cycle of the AC power and longer than the half cycle.(Mode 2) The power receiving device according to Mode 1, further comprising: the leg circuit is configured by a series connection of the first switch and the second switch; and in the power supply mode, when a high-potential side second switch of the plurality of second switches that is in an on state is controlled to an off state, the first switch in the leg circuit including the high-potential side second switch in the on state is controlled to be in an off state; and after controlling the high-potential side second switch in the on state to be in an off state, the first switch in the off state is controlled to be in an on state for a second period. (Mode 3) The power receiving device according to Mode 2, further comprising: a first sensor (160) that detects a voltage of the synchronous rectifier circuit, the first sensor detects, with respect to the voltages of the plurality of leg circuits, a rise in voltage across both ends of the first switch or a fall in voltage across both ends of the second switch; and the control circuit executes the short-circuit mode on the condition that the first sensor detects the rise in voltage or the fall in voltage. (Mode 4) The power receiving device according to Mode 2, further comprising a second sensor (170) that acquires an actual period of the current or voltage of the AC power, wherein the control circuit performs control to set the end of the second period to a time point when a time longer than the first period but shorter than one cycle of the actual period has elapsed from a time point when the low potential side second switch in an off state is controlled to an on state, which is defined as the start of the first period. (Mode 5) The power receiving device according to Mode 3, wherein the control circuit performs control to set the end of the second period to a time point when a time longer than the first period but shorter than one cycle has elapsed from a time point when the low potential side second switch in an off state is controlled to an on state, which is defined as the start of the first period.

Claims

1. A power receiving device (100, 100a, 100b, 100c) that receives AC power non - contactlessly by a magnetic field, - A resonance circuit (110) having a predetermined resonance frequency, the resonance circuit including a power receiving coil (111) for receiving the AC power; - A synchronous rectification circuit (120) composed of a plurality of leg circuits (121, 121c, 122, 122c) for rectifying the AC power into DC power; - A load device (130) that consumes the DC power; - A control circuit (150, 150a, 150b, 150c) that controls the power receiving device, - Each of the plurality of leg circuits is composed of a series connection of a rectifying diode (Di) or a first switch (SwH) and a second switch (SwL), - The first switch and the second switch each include a parallel diode (Di) connected in parallel, - In the leg circuit, the cathode of the parallel diode of the second switch is connected to the anode of the rectifying diode or the parallel diode in the first switch, - An output part (110o) of the resonance circuit is connected between the rectifying diode or the first switch and the second switch in the leg circuit, - The control circuit, in a half - cycle of the AC power, - Executes a power - feeding mode (M1) for outputting the DC power from the synchronous rectification circuit, - Executes a short - circuit mode (M2) for controlling to turn on a high - potential - side second switch (SwLH) which is a second switch among the plurality of second switches in the plurality of leg circuits and to which a voltage is applied in the reverse direction of the parallel diode, - Controls to turn on a low - potential - side second switch (SwLL) which is a second switch among the plurality of second switches in the short - circuit mode and through which a current flows in the parallel diode, for a first period that is shorter than one cycle of the AC power and longer than the half - cycle.

2. The power receiving device according to claim 1, further comprising: the leg circuit is constituted by a series connection of the first switch and the second switch; the power supply mode is: when controlling the high-potential-side second switch in the on state among the plurality of second switches to the off state, controlling the first switch in the leg circuit including the high-potential-side second switch in the on state to be in the off state; after controlling the high-potential-side second switch in the on state to the off state, performing control to turn on the first switch in the off state for a second period. A power receiving device.

3. The power receiving device according to claim 2, further comprising: a first sensor (160) for detecting the voltage of the synchronous rectification circuit; the first sensor detects the rise of the voltage across the first switch or the fall of the voltage across the second switch for the voltages of the plurality of leg circuits; the control circuit executes the short-circuit mode on the condition of the detection of the rise or fall of the voltage by the first sensor. A power receiving device.

4. The power receiving device according to claim 2, comprising: a second sensor (170) for acquiring the actual period of the current or voltage of the AC power; the control circuit controls the end of the second period to be a point in time when a time longer than the first period and shorter than one period of the actual period has elapsed from the point in time when controlling the low-potential-side second switch in the off state to the on state as the start of the first period. A power receiving device.

5. The power receiving device according to claim 3, wherein the control circuit controls the end of the second period to be a point in time when a time longer than the first period and shorter than one period has elapsed from the point in time when controlling the low-potential-side second switch in the off state to the on state as the start of the first period. A power receiving device.

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