Power reception device

Abstract

To prevent a great loss generated during switching when power supplied to a loading device by a switch of a rectification circuit is controlled.SOLUTION: This power reception device that receives AC power in a non-contact manner by a magnetic field comprises: a resonance circuit; a synchronous rectification circuit; a loading device; and a control circuit. The control circuit executes a power supply mode M1 for outputting power by the synchronous rectification circuit in a half period of the AC power and a short-circuit mode M2 for controlling, in an on state, a second switch of a high-potential side which has a voltage applied in the reverse direction of a parallel diode among a plurality of second switches in a plurality of leg circuits, and controls, in an on state, a second switch of a low-potential side which has current flowing through the parallel diode among the second switches in the short-circuit mode for a first period shorter than one period of the AC power and longer than the half period.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to a power receiving device.

Background Art

[0002] In a power receiving device used in a non-contact power supply system for a vehicle, there is a technique of using a switch in a rectifier circuit as in Patent Document 1. The rectifier circuit of Patent Document 1 supplies DC power to a load device by rectifying the AC power received by a resonance circuit including a power receiving coil. The rectifier circuit of Patent Document 1 shorts the output part of the resonance circuit, which is also the input part of the rectifier circuit, by a switch. The received power is not supplied to the load device. That is, the technique of Patent Document 1 can control the power supplied to the load device by the switch of the rectifier circuit.

[0003] The rectifier circuit of Patent Document 1 is configured by a circuit in which a switch is connected in series to the anode side of a diode. Further, the output part of the resonance circuit is connected between the diode and the switch in the rectifier circuit. The rectifier circuit of Patent Document 1 shorts the output part of the resonance circuit by turning on the switch during the energization of the diode.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, the above technique has the following problems. During the energization of the diode, a voltage is applied to the switch in the off state. When the switch becomes on, the switch changes from the state where a voltage is applied to the on state. That is, the switch causes switching loss due to hard switching.

[0006] Furthermore, when current flows through the switch, the forward current of the diode rapidly decreases. As a result, the recovery current that causes losses during switching is likely to increase.

[0007] That is, when controlling the power supplied to the load device by the switch of the rectifier circuit, a problem has been that large losses occur during switching.

Means for Solving the Problem

[0008] The present disclosure can be realized in the following forms.

[0009] According to a first aspect of the present disclosure, there is provided a power receiving device (100, 100a, 100b, 100c) that receives AC power non - contactlessly by a magnetic field. The power receiving device includes a resonance circuit (110) having a predetermined resonance frequency, the resonance circuit including a power receiving coil (111) that receives the AC power; a synchronous rectification circuit (120) configured by a plurality of leg circuits (121, 121c, 122, 122c) that rectify the AC power into 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. Each of the plurality of leg circuits is configured by 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 portion (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 executes a power supply mode (M1) in which the 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 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, is controlled to be in an on state. Among the plurality of second switches in the short - circuit mode, a low - potential - side second switch (SwLL), which is a second switch through which a current flows in the parallel diode, is controlled to be in an on state for a first period that is shorter than one cycle of the AC power and longer than the half - cycle.

[0010] By adopting such a configuration, the low-potential side second switch through which current flows in the parallel diode has current flowing through the switch as the current of the AC power reverses while remaining in the on state. That is, the short-circuit mode is executed as the current of the AC power reverses. Therefore, in the low-potential side second switch, when it is turned on, the switching loss is reduced by zero-voltage switching. Further, the short-circuit mode is executed in a state where the rectifying diode or the parallel diode of the first switch is not energized. As a result, in the rectifying diode or the parallel diode of the first switch, a recovery current is less likely to occur when the short-circuit mode is executed. Thus, the power receiving device of the present disclosure can prevent large losses from occurring during switching when controlling the power supplied to the load device in the short-circuit mode.

Brief Description of the Drawings

[0011]

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Mode for Carrying Out the Invention

[0012] A. First Embodiment: A-1. Configuration of the Device: The contactless power supply system 10 shown in FIG. 1 supplies power to the load device 130 non-contact by a magnetic field. As shown in FIG. 1, the contactless power supply system 10 includes a power transmission device 200 and a power reception device 100. The contactless power supply system 10 supplies power non-contact from the power transmission device 200 to the power reception device 100. The contactless power supply system 10 supplies power non-contact to, for example, the power reception device 100 mounted on a vehicle.

[0013] The power transmission device 200 supplies AC power to the power reception device 100 non-contact by a magnetic field. The power transmission device 200 includes an AC power supply device 210 and a power transmission resonance circuit 220.

[0014] The AC power supply device 210 supplies AC power with a predetermined operating frequency to the power transmission resonance circuit 220. The AC power supply device 210 includes a power supply circuit and a power transmission circuit. The power supply circuit is, for example, an AC / DC converter circuit that converts AC power supplied from the utility power supply into DC power. The power transmission circuit is an inverter that converts the DC power supplied from the power supply circuit into AC power with the operating frequency. The operating frequency is, for example, 85 kHz and is set using a predetermined power transmission frequency defined by the Radio Law or the like. Note that the resonance frequencies of the power transmission resonance circuit 220 and the power reception resonance 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 transmission resonance circuit 220 magnetically couples with the power reception coil 111 of the power reception device 100 and resonates. The power transmission resonance circuit 220 includes a power transmission coil 222 and a power transmission resonance capacitor 221 connected in series to the power transmission coil 222. The "power transmission resonance circuit" is also referred to as the "primary resonance circuit".

[0016] The power transmission resonance capacitor 221 resonates the power transmission resonance circuit 220 with the AC power of the operating frequency of the AC power supply device 210 in a state where the power transmission coil 222 and the power reception coil 111 are magnetically coupled. That is, the capacitance of the power transmission resonance capacitor 221 is set such that the operating frequency and the resonance frequency of the power transmission resonance circuit 220 substantially coincide in a state where the power transmission coil 222 and the power reception coil 111 are magnetically coupled.

[0017] The power transmission coil 222 generates a magnetic field corresponding to the operating frequency of the AC power supply device 210. Further, the power transmission coil 222 transmits AC power to the power reception coil 111 by magnetically coupling with the power reception coil 111. That is, the power transmission coil 222 transmits power non - contactly by utilizing the electromagnetic induction phenomenon.

[0018] The power transmission coil 222 is, for example, laid on the ground and used. More specifically, the power transmission coil 222 is laid on the ground in a direction facing the power reception coil 111 mounted on the vehicle.

[0019] The power receiving device 100 receives AC power from the power transmitting device 200 in a non-contact manner by means of a magnetic field. The power receiving device 100 includes a power receiving resonance circuit 110, a synchronous rectification circuit 120, a load device 130, a control circuit 150, and a smoothing capacitor 140. The power receiving device 100 is mounted on, for example, a vehicle and receives power from a power transmitting coil 222 laid on the ground.

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

[0021] The power receiving coil 111 magnetically couples with the power transmitting coil 222 by receiving the magnetic field generated by the power transmitting coil 222. The power receiving coil 111 receives the magnetic field generated by the power transmitting coil 222 when used in a state facing the power transmitting coil 222. Thereby, the power receiving coil 111 receives AC power of the operating frequency of the AC power supply device 210 in a non-contact manner by magnetically coupling with the power transmitting coil 222.

[0022] The power receiving resonance capacitor 112 resonates the power receiving resonance circuit 110 with AC power of the operating frequency of the AC power supply device 210 in a state where the power receiving coil 111 and the power transmitting coil 222 are magnetically coupled. That is, the capacitance of the power receiving resonance capacitor 112 is set such that the operating frequency of the AC power supply device 210 and the resonance frequency of the power receiving resonance circuit 110 substantially coincide in a state where the power transmitting coil 222 and the power receiving coil 111 are magnetically coupled. For this reason, the power receiving resonance circuit 110 has a predetermined resonance frequency according to the operating frequency of the AC power supply device 210.

[0023] In the present embodiment, the power receiving resonance capacitor 112 is arranged on the positive line Lacp of the power receiving resonance circuit 110. The "power receiving resonance capacitor" is also simply referred to as a "resonance capacitor".

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

[0025] In a leg circuit, two switches Sw are connected in series. Further, the leg circuit connects the positive electrode line Ldcp and the negative electrode line Ldcn of the DC power. One of the output terminals of the power receiving resonance circuit 110 is connected between the two switches Sw of the leg circuit. Therefore, the position between the two switches Sw of the leg circuit is the input terminal position in the synchronous rectification circuit 120. That is, the output part 110o of the power receiving resonance circuit 110 is connected between the first switch SwH and the second switch SwL in the leg circuit. Note that for the input terminal of the synchronous rectification 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. Through the terminal P1 and the terminal P2, the current due to the received AC power is input to the synchronous rectification circuit 120.

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

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

[0028] The second switch SwL includes a parallel diode Di connected in parallel. The second switch SwL and the parallel diode Di of the second switch SwL are configured in the same manner as the first switch SwH and the parallel diode Di of 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 of the first switch SwH.

[0030] In this specification, the "positive electrode line side" is also referred to as the "high side", and the "negative electrode line side" is also referred to as the "low side". For this reason, 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 during power conversion by the synchronous rectification circuit 120 will be described in detail later.

[0032] The smoothing capacitor 140 is connected in parallel to the output section of the synchronous rectification 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 or the like. That is, when the load device 130 includes a battery, the load device 130 charges the 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 mounted.

[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 the power required for driving the switch Sw in accordance with a command from the control unit 151. The drive circuit 152 is connected to the gates of all the switches Sw of the synchronous rectifier circuit 120. The drive circuit 152 drives the switch Sw by applying a gate voltage required for the on and off operations of the switch Sw to the gate of the switch Sw. In FIG. 1, for ease of understanding of the technology, the connection between the drive circuit 152 and the gate is omitted.

[0036] The control unit 151 generates a signal for controlling the on and off operations 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 and a short - circuit mode M2 in which no DC power is output from the synchronous rectifier circuit 120 in a half - cycle of the received AC power. Hereinafter, a method for controlling the power receiving device 100 by the control unit 151 will be described.

[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] In FIG. 2, below the sine wave of the input current of the synchronous rectification circuit 120, timing charts of the voltages between the gates and sources 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 illustrated. The timing chart of the voltage between the gate and source indicates the voltage value necessary to turn on the switch Sw with "H" and the voltage value necessary to turn off the switch Sw with "L". Below the timing chart of the voltage between the gate and source, waveforms of the voltages between the drains and sources 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 illustrated. Note that the waveforms of the voltages between the drains and sources are illustrated to facilitate understanding of the technology, but they are the waveforms acquired by the first sensor 160 of the second embodiment.

[0040] During one period of the input current of the synchronous rectification circuit 120, the control unit 151 controls the power receiving device 100 in a plurality of modes by the switch Sw. The plurality of modes of the power receiving device 100 will be described in order from the start of the negative half cycle in the input current of the synchronous rectification circuit 120. In FIGS. 3 to 12 used for the description of the modes of the power receiving device 100, illustrations of some configurations such as the power transmission device 200 and the control circuit 150 are omitted to facilitate understanding of the technology. Note that the periods of the respective modes of the plurality of modes of the power receiving device 100 will be described later.

[0041] In mode A of FIG. 2, the control unit 151 controls the low-side switches SwL of the first leg circuit 121 and the second leg circuit 122 to be in the on state. Further, the control unit 151 controls the high-side switches SwH of the first leg circuit 121 and the second leg circuit 122 to be in the off state. Thereby, the input current of the synchronous rectification 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. That is, since no DC power is output from the synchronous rectification circuit 120, no power is supplied to the load device 130.

[0042] In mode B of FIG. 2, the control unit 151 controls the low-side switch SwL of the second leg circuit 122 to be in the 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 the period of mode B flows through 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. That is, since DC power is output from the synchronous rectifier circuit 120, power is supplied to the load device 130.

[0043] In mode C of FIG. 2, the control unit 151 controls the high-side switch SwH of the second leg circuit 122 to be in the 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 the period of mode C flows through 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. That is, since DC power is output from the synchronous rectifier circuit 120, power is supplied to the load device 130.

[0044] In mode B of FIG. 2, since current flows through the parallel diode Di of the high-side switch SwH in the second leg circuit 122, the drain-source voltage is 0V. Therefore, when switching from mode B to C, that is, when the high-side switch SwH of the second leg circuit 122 is controlled to be in the on state, the high-side switch SwH of the second leg circuit 122 performs switching with the drain-source voltage being 0V. Thus, the switching loss is reduced. That is, the high-side switch SwH of the second leg circuit 122 performs soft switching. Such a switching method is generally also called "zero voltage switching" or "ZVS (Zero Voltage Switching)".

[0045] In mode D of FIG. 2, the control unit 151 controls the high-side switch SwH of the second leg circuit 122 to be in the 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 the period of mode D flows to the load device 130 through 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. That is, since DC power is output from the synchronous rectifier circuit 120, power is supplied to the load device 130.

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

[0047] In Figure 2, mode DE occurs by transitioning from mode D 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 positively reversed input current of the synchronous rectifier circuit 120 begins to flow toward the power receiving coil 111 through 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 Figure 7. At this time, the current flowing through the parallel diode Di of the high-side switch SwH of the second leg circuit 122 in mode D gradually decreases to 0 A in a sine wave shape. Therefore, the 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 energized. That is, in the parallel diode Di of the high-side switch SwH of the second leg circuit 122, losses due to the recovery current are less likely to occur.

[0048] In mode E of Figure 2, the control unit 151 controls the low-side switch SwL of the second leg circuit 122 to be in the 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 the period of mode E returns to the power receiving coil 111 through the low-side switch SwL of the first leg circuit 121 and the low-side switch SwL in the second leg circuit 122, as indicated by arrow Aie in Figure 8. That is, since no DC power is output from the synchronous rectifier circuit 120, no power is supplied to the load device 130.

[0049] In mode DE of FIG. 2, since current is flowing through the parallel diode Di of the low-side switch SwL in the second leg circuit 122, the voltage between the drain and source is 0V. 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 the on state, the low-side switch SwL of the second leg circuit 122 performs switching with the voltage between the drain and source being 0V. That is, by switching the low-side switch SwL of the second leg circuit 122 to the on state by zero voltage switching, the switching loss is reduced.

[0050] In mode F of FIG. 2, the control unit 151 controls the low-side switch SwL of the first leg circuit 121 to the 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 the period of 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. That is, since DC power is output from the synchronous rectifier circuit 120, power is supplied to the load device 130.

[0051] In mode G of FIG. 2, the control unit 151 controls the high-side switch SwH of the first leg circuit 121 to the 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 the period of 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. That is, since DC power is output from the synchronous rectifier circuit 120, power is supplied to the load device 130.

[0052] In mode F of FIG. 2, since current is flowing through the parallel diode Di of the high-side switch SwH in the first leg circuit 121, the voltage between the drain and the source is 0V. Therefore, when switching from mode F to G, that is, when the high-side switch SwH of the second leg circuit 121 is controlled to be in the on state, the high-side switch SwH of the second leg circuit 122 performs switching with the voltage between the drain and the source being 0V. That is, by switching the high-side switch SwH of the second leg circuit 122 to the on state by zero-voltage switching, the switching loss is reduced.

[0053] In mode H of FIG. 2, the control unit 151 controls the high-side switch SwH of the second leg circuit 122 to be in the 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 the period of mode H flows through the high-side switch SwH of the first leg circuit 121 and the low-side switch SwL in the second leg circuit 122 to the load device 130 as indicated by the arrow Aih in FIG. 11. That is, since DC power is output from the synchronous rectifier circuit 120, power is supplied to the load device 130.

[0054] In mode H of FIG. 2, the current flowing through the high-side switch SwH in the first leg circuit 121 flows between the drain and the source through the parallel diode Di. That is, when the high-side switch SwH of the first leg circuit 121 transitions from mode G to mode H, it is controlled to be in the off state with the voltage between the drain and the source being 0V. Therefore, by switching the high-side switch SwH of the first leg circuit 121 to the off state by zero-voltage switching, the switching loss is reduced.

[0055] In FIG. 2, mode HA is generated by the transition from mode H when the input current of the synchronous rectifier circuit 120 reverses 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. Thus, the input current of the synchronous rectifier circuit 120 that has reversed negatively starts to flow toward the power receiving coil 111 through 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 the arrow Aiha in FIG. 12. At this time, the current flowing through the parallel diode Di of the high-side switch SwH in the first leg circuit 121 in mode H gradually decreases to 0 A in a sine wave shape. Therefore, the 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 energized. That is, in the parallel diode Di of the high-side switch SwH in the first leg circuit 121, losses due to the recovery current are less likely to occur.

[0056] In mode HA in FIG. 2, since a current is flowing through the parallel diode Di of the low-side switch SwL in the first leg circuit 121, 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 with the drain-source voltage being 0 V. That is, by switching the low-side switch SwL of the first leg circuit 121 to the on state by zero-voltage switching, the switching loss is reduced.

[0057] Regarding the above, as shown in the upper part of FIG. 2, the short - circuit mode M2 corresponds to mode A, mode DE, mode E, and mode HA. The other modes correspond to the power - supply mode M1. In the short - circuit mode M2, as shown in FIGS. 3 and 8, the control unit 151 controls the high - potential - side low - side switch SwLH, which is a low - side switch SwL in which a voltage is applied in the reverse direction of the parallel diode Di of the low - side switches SwL in a plurality of leg circuits, to be in the on state. Here, the high - potential side means the leg circuit having the input terminal of the synchronous rectifier circuit 120 with a higher potential among the two leg circuits. The high - potential - side low - side switch SwLH is the low - side switch SwL in the leg circuit having the input terminal with a higher potential among the two input terminals P1 and P2 of the synchronous rectifier circuit 120. The "high - potential - side low - side switch" is also referred to as the "high - potential - 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 and 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 mode A and mode C in a half - cycle, and the ratio of mode E and mode G in a half - cycle. Therefore, the length of the time 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 starts up, based on the rated power of the load device 130.

[0059] Note that the time of each of mode B, mode D, mode F, and mode H is determined in advance before the power - receiving device 100 starts 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, in the short-circuit mode M2, the low-potential-side low-side switch SwLL, which is a low-side switch SwL through which current is flowing in the parallel diode Di among a plurality of low-side switches SwL in the short-circuit mode M2, to be in an on state during a first period T1 that is shorter than one cycle of the received AC power and longer than a half cycle. Note that the low potential side means the leg circuit having the input terminal of the synchronous rectification circuit 120 with a lower potential among the two leg circuits. The low-potential-side low-side switch SwLL is a low-side switch SwL in the leg circuit having the input terminal with a lower potential among the two input terminals P1 and P2 of the synchronous rectification circuit 120. The "low-potential-side low-side switch" is also referred to as the "low-potential-side second switch". That is, the control unit 151 controls the low-potential-side low-side switch SwLL to be in an on state for a period longer than a half cycle in the short-circuit mode M2, so that the on state continues until the next short-circuit mode M2. As a result, the low-potential-side low-side switch SwLL that is controlled to be in an on state in the short-circuit mode M2 continues to be in an on state until the current reverses. Therefore, the low-potential-side low-side switch SwLL functions as a high-potential-side low-side switch SwLH in response to the reversal of the current, and starts the short-circuit mode M2 by zero-voltage switching.

[0061] That is, as shown in FIG. 2, the start period T1s of the first period T1 is the time point when the off-state low-potential-side low-side switch SwLL is controlled to be in an on state. The length of the first period T1 is shorter than one cycle of the operating frequency of the AC power supply device 210 and longer than a half cycle, and is predetermined before the startup of the power receiving device 100 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-potential-side low-side switch SwLH in the on state among the plurality of low-side switches SwL in the short-circuit mode M2 to the off state, it controls the high-side switch SwH in the leg circuit including the high-potential-side low-side switch SwLH in the on state to be in the off state. Further, after the control unit 151 controls the high-potential-side low-side switch SwLH in the on state to the off state, as shown in FIGS. 5 and 10, it performs control to turn on the high-side switch SwH in the off state during the second period T2. That is, when transitioning from the short-circuit mode M2 to the power supply mode M1, the control unit 151 turns off the high-side switch SwH and rectifies it through the antiparallel diode Di. Therefore, in the synchronous rectification circuit 120, when the high-side switch SwH is controlled to be in the on state, the switching loss is reduced by zero-voltage switching.

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

[0064] By adopting such a configuration, the low-potential side second switch SwLL through which current flows in the parallel diode Di remains in the on state, and current flows through the switch Sw as the current of the AC power reverses. That is, the short-circuit mode M2 is executed as the current of the AC power reverses. Therefore, in the low-potential side second switch SwLL, when it is in the on state, the switching loss is reduced by zero-voltage switching. Further, in the state where the parallel diode Di of the first switch SwH is not energized, the short-circuit mode M2 is executed. As a result, in the parallel diode Di of the first switch SwH, a recovery current is less likely to occur when the short-circuit mode M2 is executed. Thus, when the power supply device 100 of the present disclosure controls the power supplied to the load device 130 by the short-circuit mode M2, it is possible to prevent a large loss from occurring during switching.

[0065] Furthermore, by adopting such a configuration, current flows through the first switch SwH due to the turn-off of the high-potential side low-side switch SwLH. Since the first switch SwH is in the off state, the current flows through the parallel diode Di. As a result, in the first switch SwH, when it is in the on state, the switching loss is reduced by zero-voltage switching. Thus, in the power supply mode M1, the power supply device 100 of the present disclosure can reduce the loss during switching compared to the configuration in which the first switch SwH is turned on by hard switching.

[0066] In addition, by adopting such a configuration, the short-circuit mode M2 is executed according to a period corresponding to the resonance frequency without detecting the period of the AC power. Thus, the power supply device 100 of the present disclosure can reduce the cost required for the power supply device 100 compared to the configuration including a sensor for detecting the period of the AC power. Further, by adopting such a configuration, the first switch SwH is controlled to be in the off state after the second period in the state where a forward voltage is applied to the first parallel diode. As a result, when the first switch SwH is controlled to be in the off state, the switching loss can be reduced by zero-voltage switching.

[0067] B. Second Embodiment: As shown in FIG. 13, the 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. That is, the first sensor 160 is a voltage sensor. The first sensor 160 is connected across the drain-source of the low-side switch SwL. The first sensor 160 detects the voltage drop Vf at both ends of the low-side switch SwL for the voltages of the two leg circuits. The voltage drop Vf is illustrated in FIG. 2. The first sensor 160 transmits the acquired information to the control unit 151a.

[0069] The other configurations of the non-contact power supply system 10a of the second embodiment are the same as those of the non-contact power supply system 10 of the first embodiment. For the configurations of the non-contact power supply system 10a of the second embodiment that are different from those of the non-contact power supply system 10 of the first embodiment, "a" is appended to the end of the reference numerals.

[0070] The control unit 151a of the second embodiment executes the short-circuit mode M2 on the condition that the voltage drop Vf is detected by the first sensor 160. For example, as shown in the lower part of FIG. 2, the control unit 151a of the second embodiment detects the voltage drop Vf at the low-side switch SwL of the second leg circuit 122. After confirming that the short-circuit mode M2 is being normally executed, the control unit 151a of the second embodiment controls the low-side switch SwL of the second leg circuit 122 to be in the on state during the first period T1. The control unit 151a of the second embodiment controls the low-side switch SwL of the first leg circuit 121 in the same manner.

[0071] With such a configuration, the power receiving device 100a of the second embodiment can control the synchronous rectifier circuit 140 more stably than in a configuration without the first sensor 160. Furthermore, generally, a voltage sensor is less expensive than a current sensor. Therefore, the power receiving device 100a of the present disclosure can reduce the cost of the device compared to configuring the first sensor 160 as a current sensor.

[0072] Furthermore, in such a configuration, the high-side switch SwH is turned on and off in a period shorter than one cycle. For example, when the high-side switch SwH is simply driven by a signal inverted from the low-side switch SwL, if the voltage rise and fall waveforms cannot be detected properly, the high-side switch SwH may continue to be in the on state. As a result, the subsequent voltage rises and falls may not occur, and there is a possibility that the short-circuit mode or the power supply mode cannot be executed. However, in the power receiving device 100a of the present disclosure, since the high-side switch SwH is turned off in a period shorter than one cycle, such a concern does not arise and it can operate stably.

[0073] C. Third Embodiment: As shown in FIG. 14, the 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 the AC power. The second sensor 170 is provided in the power receiving resonance circuit 110, acquires the actual period of the current flowing through the power receiving resonance circuit 110, and transmits it to the control unit 151b. The "period taken 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 cycle 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 non-contact power supply system 10b of the third embodiment are the same as those of the non-contact power supply system 10 of the first embodiment. For the configurations of the non-contact power supply system 10b of the third embodiment that are different from those of the non-contact power supply system 10 of the first embodiment, "b" is added to the end of the reference numeral.

[0075] With such a configuration, the short-circuit mode M2 and the power supply mode M1 are executed based on the actual period. By the control based on the actually acquired period of the AC power, the power receiving device 100 of the present disclosure can execute the short-circuit mode M2 and the power supply mode M1 stably as compared with the mode of performing control without detecting the period of the AC power.

[0076] D. Fourth Embodiment: In the above embodiment, all the rectifying elements of the synchronous rectification circuit 120 are constituted by the switch Sw. However, as in the synchronous rectification circuit 120c of the fourth embodiment in FIG. 15, only the low-side rectifying element may be constituted by the switch Sw. That is, in the synchronous rectification circuit 120c of the fourth embodiment, the high-side rectifying element is constituted by the rectifying diode Di. Since the short-circuit mode M2 is executed by the low-side switch SwL in the synchronous rectification circuit 120c of the fourth embodiment, the short-circuit mode M2 can be executed as long as only the low-side rectifying element is constituted by the switch Sw. That is, the control circuit 150c of the fourth embodiment controls only the low-side switch SwL.

[0077] Other configurations of the non-contact power supply system 10c of the fourth embodiment are the same as those of the non-contact power supply system 10 of the first embodiment. For the configurations of the non-contact power supply system 10c of the fourth embodiment that are different from those of the non-contact power supply system 10 of the first embodiment, "c" is added to the end of the reference numeral.

[0078] Therefore, even in such a form, when the power receiving device 100c of the present disclosure controls the power supplied to the load device 130 in the short-circuit mode M2, it is possible to prevent large losses from occurring during switching. Furthermore, in the rectifying diode Di, a recovery current is less likely to occur when the short-circuit mode M2 is executed. In addition, since the power required for controlling the switch Sw is reduced, the rated power of the control circuit 150 can be made smaller. That is, the power receiving device 100c of the present disclosure can reduce the size of the device as compared with the form in which all the rectifying elements are constituted by the switch Sw.

[0079] E. Modification Example 1: In the above embodiment, as shown in FIG. 1, an example in which a resonance method using the power transmission resonance circuit 220 of the series resonance circuit and the power reception resonance circuit 110 of the series resonance circuit is applied was shown. In contrast, the following resonance methods can also be applied. However, for ease of understanding of the technology, in FIGS. 16 to 19, only the configurations corresponding to the power transmission resonance circuit 220 and the power reception resonance circuit 110 in the first embodiment are shown.

[0080] As shown in FIG. 16, the power transmission resonance circuit 220c may be a parallel resonance circuit in which the power transmission resonance capacitor 221c is connected in parallel to the power transmission coil 222, and the power reception resonance circuit 110 may be the same series resonance circuit as in the first embodiment. Further, as shown in FIG. 17, the power transmission resonance circuit 220d may be a circuit in which the power transmission resonance capacitor 221d is connected in series to the power transmission coil 222, and another power transmission resonance capacitor 221 is connected in series, and the power transmission resonance capacitor 221 and the power transmission coil 222 are connected in parallel. At this time, the power reception resonance circuit 110 is the same series resonance circuit as in the first embodiment. Further, as shown in FIG. 18, the power transmission device 200e may be further provided with a tertiary resonance circuit 310 in which a tertiary coil 311 and a tertiary resonance capacitor 312 are connected in series, which is a circuit independent of the power transmission resonance circuit 220e. The tertiary resonance circuit 310 is arranged such that the tertiary coil 311 is magnetically coupled to each of the power transmission coil 222 and the power reception coil 111. Further, as shown in FIG. 19, in the power transmission device 220f, a tertiary resonance circuit 310f in which a tertiary coil 311e and a tertiary resonance capacitor 312f are connected in parallel may be connected in series to the power transmission coil 222f. The tertiary resonance circuit 310f is arranged such that the tertiary coil 311f is magnetically coupled to each of the power transmission coil 222f and the power reception coil 111. In the form in which the tertiary resonance circuit 310f is provided, the power reception resonance circuit 110 is the same series resonance circuit as in the first embodiment.

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

[0082] G. Modification Example 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 rectification circuit 120. The current sensor is connected in series to the synchronous rectification circuit 120 and the load device 130. The current sensor transmits information on the output current of the synchronous rectification circuit 120 to the control unit 151. The control unit 151 adjusts the period of the short-circuit mode M2 by the first sensor 160 based on, for example, the power supplied to the predetermined load device 130. (2) In the above embodiment, the first sensor 160 detects the voltage fall Vf. The control unit 151 executes the short-circuit mode M2 on the condition that the first sensor 160 detects the voltage fall Vf. However, the first sensor 160 may be provided between the drain and source of the high-side switch SwH to detect the voltage rise at 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 the voltage rise. (3) In the first embodiment, the power receiving resonance capacitor 111RC includes only the positive-side resonance capacitor 111RCp arranged on the positive-side line Lacp of the power receiving resonance circuit 110. However, the power receiving resonance capacitor 111RC may include a negative-side resonance capacitor arranged on the negative-side line Lacn of the power receiving resonance circuit 110. Thereby, common-mode noise is suppressed. (4) In the above embodiment, the switch Sw of the synchronous rectification circuit 120 is a MOSFET. However, the switch Sw of the synchronous rectification circuit 120 may be other switching elements. 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 rectification circuit 120 is composed of two leg circuits. However, the synchronous rectification circuit 120 may be composed of two or more leg circuits. For example, the synchronous rectification circuit 120 may be a circuit composed of three leg circuits and rectifying 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 starts 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 a current sensor for the power receiving device 100 to acquire the current flowing through the load device 130. More specifically, the control unit 151 determines the power 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. Thereby, even when the AC power received by the power receiving device 100 fluctuates, the power receiving device 100 can efficiently supply power to the load device 130.

[0083] The present disclosure is not limited to the above embodiments and modifications, and can be realized in various configurations without departing from the gist thereof. For example, the embodiments and modifications corresponding to the technical features in each form described in the summary of the disclosure can be appropriately replaced or combined in order to solve part or all of the above problems or to achieve part or all of the above effects. Also, if the technical feature is not described as essential in this specification, it can be appropriately deleted. (Form 1) A power receiving device (100, 100a, 100b, 100c) that receives AC power non - contactlessly by a magnetic field, A resonant circuit (110) having a predetermined resonant frequency, the resonant circuit including a power receiving coil (111) for receiving the AC power, A synchronous rectifier circuit (120) configured by 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) for controlling the power receiving device, Each of the plurality of leg circuits is configured by 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 resonant 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, A power supply mode (M1) for outputting the DC power from the synchronous rectifier circuit, A short - circuit mode (M2) for controlling, among the plurality of second switches in the plurality of leg circuits, a high - potential - side second switch (SwLH) which is a second switch to which a voltage is applied in the reverse direction of the parallel diode, to an on state, The short - circuit mode controls, among the plurality of second switches, a low - potential - side second switch (SwLL) which is a second switch through which a current is flowing in the parallel diode, to an on state for a first period that is longer than a half cycle and shorter than one cycle of the AC power. A power receiving device. (Embodiment 2) The power receiving device according to Embodiment 1, further, The leg circuit is configured 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, it is controlled so that the first switch in the leg circuit including the high-potential-side second switch in the on state is in the off state. A power receiving device that, after controlling the high-potential-side second switch in the on state to the off state, controls the first switch in the off state to be in the on state for a second period. (Embodiment 3) The power receiving device according to Embodiment 2, further comprising A first sensor (160) for detecting the voltage of the synchronous rectification circuit, The first sensor detects the rising of the voltage across the first switch or the falling of the voltage across the second switch with respect to the voltages of the plurality of leg circuits. The control circuit executes the short-circuit mode on the condition that the first sensor detects the rising or falling of the voltage. (Embodiment 4) The power receiving device according to Embodiment 2, 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 the low-potential-side second switch in the off state is controlled to be in the on state as the start of the first period. (Embodiment 5) The power receiving device according to Embodiment 3, 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 the low-potential-side second switch in the off state is controlled to be in the on state as the start of the first period.

Description of Reference Numerals

[0084] 10, 10a, 10b, 10c... Non-contact power supply system, 100, 100a, 100b, 100c... Power receiving device, 110... Power receiving resonance circuit, 111... Power receiving coil, 110o... Output section, 120, 120c... Synchronous rectification circuit, 121, 121c... First leg circuit, 122, 122c... Second leg circuit, 130... Load device, 140... Smoothing capacitor, 150, 150a, 150b, 150c... Control circuit, Di... Parallel diode, M1... Power supply mode, M2... Short-circuit mode, Sw... Switch, SwH... First switch, SwL... Second switch, SwLH... High-potential side second switch, SwLL... Low-potential side second switch

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) for controlling the power receiving device, comprising: 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, The 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, A power supply mode (M1) for outputting the DC power from the synchronous rectification circuit, 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, A power receiving device that 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 longer than the half - cycle and shorter than one cycle of the AC power.

2. The power receiving device according to claim 1, further comprising: The leg circuit is composed of a series connection of the first switch and the second switch, The power supply mode is: When controlling to turn off a high - potential - side second switch in the on - state among the plurality of second switches, control is performed such that the first switch in the leg circuit including the high - potential - side second switch in the on - state is in the off - state. A power receiving device that controls the high-potential-side second switch in the on state to the off state and then controls the first switch in the off state to be in the on state during a second period.

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 rising of the voltage across both ends of the first switch or the falling of the voltage across both ends of the second switch with respect to the voltages of the plurality of leg circuits. The control circuit executes the short-circuit mode on the condition that the first sensor detects the rising or the falling of the voltage.

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 that is longer than the first period and shorter than one period of the actual period from the point in time when the low-potential-side second switch in the off state is controlled to be in the on state as the start of the first period.

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

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