Power receiving 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 feeding system for a vehicle, 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 supplies DC power to a load device by rectifying AC power received by a resonance circuit including a power receiving coil. In the rectifier circuit of Patent Document 1, the switch short-circuits the output section of the resonance circuit, which is also the input section of the rectifier circuit. The received power is not supplied to the load device. That is, the technology of Patent Document 1 can control the power supplied to the load device by means of the switch in 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 section of the resonance circuit is connected between the diode and the switch in the rectifier circuit. The rectifier circuit of Patent Document 1 short-circuits the output section of the resonance circuit by turning on the switch while the diode is conducting. [Prior Art Document] [Patent Document]

[0004] [Patent Document 1] Japanese Patent No. 6240503 [Summary of Invention] [Problem to be Solved by Invention]

[0005] However, the above technology has the following problems. While the diode is conducting, voltage is applied to the switch in the off state. When the switch is turned on, the switch transitions from a voltage-applied state to the on state. That is, switching loss occurs in the switch due to hard switching.

[0006] Furthermore, when current flows through the switch, the forward current of the diode drops sharply. This makes it easier for the recovery current, which causes losses during switching, to become large.

[0007] In other words, when controlling the power supplied to a load device by switching a rectifier circuit, a major problem was that significant losses occurred during switching. [Means for solving the problem]

[0008] This disclosure can be implemented in the following forms:

[0009] According to the first embodiment of this disclosure, a power receiving device (100, 100a, 100b, 100c) is provided that receives AC power in a non-contact manner using a magnetic field. The power receiving device comprises a resonant circuit (110) having a predetermined resonant frequency, including a power receiving coil (111) for receiving AC power, and a plurality of leg circuits (121, 121c, 122, 122c), a synchronous rectifier circuit (120) for rectifying the AC power to DC power, a load device (130) for consuming the DC power, and a control circuit (150, 150a, 150b, 150c) for controlling the power receiving device, each of the plurality of leg circuits being composed of a series connection of a rectifier diode (Di) or a first switch (SwH) and a second switch (SwL), the first switch and the second switch each comprising a parallel diode (Di) connected in parallel, and the leg circuit having the anode of the rectifier diode or the parallel diode in the first switch as The cathode of the parallel diode of the second switch is connected, and the output section (110o) of the resonant circuit is connected in the leg circuit between the rectifier diode or the first switch and the second switch. The control circuit performs a power supply mode (M1) in which the DC power is output from the synchronous rectifier circuit during half a cycle of the AC power, and a short-circuit mode (M2) in which the high-potential side second switch (SwLH), which is one of the multiple second switches in the multiple leg circuits to which a voltage is applied in the reverse direction of the parallel diode, is turned on. In the short-circuit mode, the low-potential side second switch (SwLL), which is one of the multiple second switches to which current flows through the parallel diode, is turned on for a first period that is shorter than one cycle of the AC power and longer than half a cycle.

[0010] In this configuration, the low-potential second switch, through which current flows to the parallel diode, remains in the ON state, and current flows to the switch as the AC power current reverses. In other words, the short-circuit mode is executed in conjunction with the reversal of the AC power current. Therefore, in the low-potential second switch, switching losses are reduced by zero-voltage switching when it turns ON. Furthermore, the short-circuit mode is executed when the rectifier diode or the parallel diode of the first switch is not energized. As a result, recovery current is less likely to occur in the rectifier diode or the parallel diode of the first switch when the short-circuit mode is executed. Therefore, the power receiving device of this disclosure can prevent large losses from occurring during switching when controlling the power supplied to the load device by the short-circuit mode. [Brief explanation of the drawing]

[0011] [Figure 1] An explanatory diagram showing the configuration of the contactless power supply system of the first embodiment. [Figure 2] Switch timing chart. [Figure 3] A diagram illustrating the operation of a synchronous rectifier circuit in Mode A. [Figure 4] A diagram illustrating the operation of a synchronous rectifier circuit in Mode B. [Figure 5] A diagram illustrating the operation of a synchronous rectifier circuit in Mode C. [Figure 6] A diagram illustrating the operation of a synchronous rectifier circuit in Mode D. [Figure 7] A diagram illustrating the operation of a synchronous rectifier circuit in mode DE. [Figure 8] A diagram illustrating the operation of a synchronous rectifier circuit in Mode E. [Figure 9] A diagram illustrating the operation of a synchronous rectifier circuit in mode F. [Figure 10] A diagram illustrating the operation of a synchronous rectifier circuit in mode G. [Figure 11] A diagram illustrating the operation of a synchronous rectifier circuit in mode H. [Figure 12]Explanatory diagram illustrating the operation of a synchronous rectifier circuit in mode HA. [Figure 13] Explanatory diagram illustrating the configuration of a wireless power transfer system according to a second embodiment. [Figure 14] Explanatory diagram illustrating the configuration of a wireless power transfer system according to a third embodiment. [Figure 15] Explanatory diagram illustrating the configuration of a wireless power transfer system according to a fourth embodiment. [Figure 16] Explanatory diagram illustrating a resonance method according to a modified example. [Figure 17] Explanatory diagram illustrating a resonance method according to a modified example. [Figure 18] Explanatory diagram illustrating a resonance method according to a modified example. [Figure 19] Explanatory diagram illustrating a resonance method according to a modified example. [Figure 20] Explanatory diagram illustrating the configuration of a filter circuit. [Figure 21] Explanatory diagram illustrating the configuration of a filter circuit. DETAILED DESCRIPTION OF THE INVENTION

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

[0013] The power transmission device 200 supplies AC power to the power receiving device 100 in a contactless manner via 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 unit 210 supplies AC power at a predetermined operating frequency to the power transmission resonant circuit 220. The AC power supply unit 210 comprises a power supply circuit and a power transmission circuit. The power supply circuit is, for example, an AC / DC converter circuit, which converts AC power supplied from the grid 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 at the operating frequency. The operating frequency is, for example, 85 kHz, and is set using a predetermined power transmission frequency as defined by the Radio Law, etc. The resonant frequencies of the power transmission 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 unit 210.

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

[0016] The power transmission resonant capacitor 221 causes the power transmission resonant circuit 220 to resonate with the AC power at the operating frequency of the AC power supply unit 210 when the power transmission coil 222 and the power receiving coil 111 are magnetically coupled. In other words, the capacitance of the power transmission resonant capacitor 221 is set so that the operating frequency and the resonant frequency of the power transmission resonant circuit 220 are approximately the same when the power transmission coil 222 and the power receiving coil 111 are magnetically coupled.

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

[0018] The power transmission coil 222 is used, for example, by being laid on the ground. More specifically, the power transmission coil 222 is laid on the ground in a direction 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 non-contact 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 and receives power from a power transmitting coil 222 laid on the ground.

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

[0021] The receiving coil 111 is magnetically coupled to the transmitting coil 222 by receiving the magnetic field emitted by the transmitting coil 222. The receiving coil 111 is used in a position facing the transmitting coil 222, thereby receiving the magnetic field emitted by the transmitting coil 222. As a result, the receiving coil 111 magnetically couples with the transmitting coil 222, and receives AC power at the operating frequency of the AC power supply unit 210 in a non-contact manner.

[0022] The receiving resonant capacitor 112 resonates with the AC power at the operating frequency of the AC power supply 210 when the receiving coil 111 and the transmitting coil 222 are magnetically coupled. In other words, the capacitance of the receiving resonant capacitor 112 is set so that the operating frequency of the AC power supply 210 and the resonant frequency of the receiving resonant circuit 110 approximately coincide when the transmitting coil 222 and the receiving coil 111 are magnetically coupled. For this reason, the receiving resonant circuit 110 has a predetermined resonant frequency according to the operating frequency of the AC power supply 210.

[0023] In this embodiment, the power-receiving resonant capacitor 112 is located on the positive line Lacp of the power-receiving resonant circuit 110. The "power-receiving resonant capacitor" is also 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 rectifying elements. The synchronous rectifier circuit 120 has two leg circuits: a first leg circuit 121 and a second leg circuit 122. Note that the "synchronous rectifier circuit" is also simply called a "rectifier circuit".

[0025] The leg circuit consists of two switches Sw connected in series. Furthermore, the leg circuit connects the positive line Ldcp and the 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 space between the two switches Sw of the leg circuit is the position of the input terminal in the synchronous rectifier circuit 120. 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 terminal P1 is the first leg circuit 121. The leg circuit having terminal P2 is the second leg circuit 122. Current from the received AC power is input to the synchronous rectifier circuit 120 via terminals P1 and P2.

[0026] Each of the two leg circuits is composed of a series connection of a first switch SwH, which acts as a rectifier element on the positive line Ldcp, and a second switch SwL, which acts as a rectifier element on the negative line Ldcn. In other words, the switch Sw constitutes all of the rectifier elements in the synchronous rectifier circuit 120.

[0027] The first switch SwH is equipped with 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 located on the positive electrode line Ldcp side, and the source of the first switch SwH is located 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. 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 accordance with the command of the control circuit 150.

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

[0029] In other words, in the REG 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 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." 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 explained in detail later.

[0032] The smoothing capacitor 140 is connected in parallel to the output section of the synchronous rectifier circuit 120 and the load device 130. The smoothing capacitor 140 smooths 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 a device that includes, for example, a battery and a battery protection circuit. That is, if the load device 130 includes a battery, the load device 130 charges 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 on which the power receiving device 100 is installed.

[0034] The control circuit 150 controls the power receiving device 100. The control circuit 150 comprises 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 necessary to drive the switch Sw in response to a command from the control unit 151. The drive circuit 152 is connected to the gate of each of the switches Sw in the synchronous rectifier circuit 120. The drive circuit 152 drives the switch Sw by applying the gate voltage necessary for the on and off operation of the switch Sw to the gate of the switch Sw. Note that in Figure 1, the connection between the drive circuit 152 and the gate is omitted for the sake of easier understanding of the technology.

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

[0037] The control unit 151 performs two modes during half a cycle of the received AC power: 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 DC power is not output from the synchronous rectifier circuit 120. The control method of the power receiving device 100 by the control unit 151 is described below.

[0038] A-2. Control method for the power receiving device: The upper part of Figure 2 shows the sine wave of the input current of the synchronous rectifier circuit 120.

[0039] In Figure 2, below the sine wave of the input current of the synchronous rectifier circuit 120, timing charts of the gate-source voltages for 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 gate-source voltage timing chart, "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 gate-source voltage timing chart, the waveforms of the drain-source voltages for 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 to facilitate understanding of the technology, but they are waveforms acquired by the first sensor 160 of the second embodiment.

[0040] The control unit 151 controls the power receiving device 100 to multiple modes using a switch Sw during one cycle of the input current of the synchronous rectifier circuit 120. The multiple modes of the power receiving device 100 will be described in order from the start of the negative half-cycle of the input current of the synchronous rectifier circuit 120. In addition, in order to facilitate understanding of the technical aspects, some components such as the power transmission device 200 and the control circuit 150 are omitted from Figures 3 to 12 used to describe the modes of the power receiving device 100. The duration of each mode of the multiple modes of the power receiving device 100 will be described later.

[0041] In mode A of Figure 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, during the period of mode A, the input current of the synchronous rectifier circuit 120 returns to the power receiving coil 111 via the two low-side switches SwL, as indicated by arrow Aia in Figure 3. In other words, since no DC power is output from the synchronous rectifier circuit 120, no power is supplied to the load device 130.

[0042] In Mode B of Figure 2, the control unit 151 controls the low-side switch SwL of the second leg circuit 122 to the OFF state. The control unit 151 maintains the switches Sw of the second leg circuit 122 other than the low-side switch SwL in the same state as in Mode A. As a result, during the period of Mode B, the input current of the synchronous rectifier circuit 120 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 Figure 4. In other words, DC power is output from the synchronous rectifier circuit 120, and power is supplied to the load device 130.

[0043] In mode C of Figure 2, the control unit 151 controls the high-side switch SwH of the second leg circuit 122 to 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, during the period of mode C, the input current of the synchronous rectifier circuit 120 flows to the load device 130 via the high-side switch SwH of the second leg circuit 122 and the low-side switch SwL of the first leg circuit 121, as indicated by the arrow Aic in Figure 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 Figure 2, current flows through the parallel diode Di of the high-side switch SwH in the second leg circuit 122, so 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 the ON state, the high-side switch SwH of the second leg circuit 122 switches with the drain-source voltage at 0V. Thus, switching losses are reduced. In other words, the high-side switch SwH of the second leg circuit 122 performs soft switching. This type of switching method is generally called "zero voltage switching" or "ZVS (Zero Voltage Switching)".

[0045] In mode D in Figure 2, the control unit 151 controls the high-side switch SwH of the second leg circuit 122 to 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, during the period of mode D, the input current of the synchronous rectifier circuit 120 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 Figure 6. In other words, DC power is output from the synchronous rectifier circuit 120, and power is supplied to the load device 130.

[0046] In mode D of Figure 2, the current flowing through the high-side switch SwH in the second leg circuit 122 flows between the drain and source via 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 source is 0V during the transition from mode C to mode D. Therefore, switching losses are reduced because the high-side switch SwH of the second leg circuit 122 is switched to the off state by zero-voltage switching.

[0047] In Figure 2, mode DE occurs as a transition from mode D due to the reversal of the input current of the synchronous rectifier circuit 120 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 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, 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 sinusoidally to 0A. 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 energized. In other words, losses due to recovery current are less likely to occur in the parallel diode Di of the high-side switch SwH of the second leg circuit 122.

[0048] In mode E of Figure 2, the control unit 151 controls the low-side switch SwL of the second leg circuit 122 to the ON state. The control unit 151 maintains the switches Sw of the second leg circuit 122, other than the low-side switch SwL, in the same state as in mode D. As a result, during the period of mode E, the input current of the synchronous rectifier circuit 120 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 Figure 8. In other words, 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 Figure 2, current flows through the parallel diode Di of the low-side switch SwL in the second leg circuit 122, so the drain-source voltage 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 switches with the drain-source voltage at 0V. In other words, the switching loss is reduced because the low-side switch SwL of the second leg circuit 122 switches to the ON state by zero-voltage switching.

[0050] In mode F of Figure 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 of the first leg circuit 121 other than the low-side switch SwL in the same state as in mode E. As a result, during the period of mode F, the input current of the synchronous rectifier circuit 120 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 Figure 9. In other words, DC power is output from the synchronous rectifier circuit 120, and power is supplied to the load device 130.

[0051] In mode G of Figure 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, during the period of mode G, the input current of the synchronous rectifier circuit 120 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 the arrow Aig in Figure 10. In other words, DC power is output from the synchronous rectifier circuit 120, and power is supplied to the load device 130.

[0052] In mode F of Figure 2, current flows through the parallel diode Di of the high-side switch SwH in the first leg circuit 121, so the drain-source voltage is 0V. 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 switches while the drain-source voltage is 0V. In other words, the switching loss is reduced because the high-side switch SwH of the second leg circuit 122 switches to the ON state by zero-voltage switching.

[0053] In mode H in Figure 2, the control unit 151 controls the high-side switch SwH of the second leg circuit 122 to 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, during the period of mode H, the input current of the synchronous rectifier circuit 120 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 the arrow Aih in Figure 11. In other words, DC power is output from the synchronous rectifier circuit 120, and power is supplied to the load device 130.

[0054] In mode H in Figure 2, the current flowing through the high-side switch SwH in the first leg circuit 121 flows between the drain and source via the parallel diode Di. That is, the high-side switch SwH of the first leg circuit 121 is controlled to be in the off state when the voltage between the drain and source is 0V during the transition from mode G to mode H. Therefore, switching losses are reduced because the high-side switch SwH of the first leg circuit 121 is switched to the off state by zero-voltage switching.

[0055] In Figure 2, mode HA is generated by a transition from mode H as 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. As a result, the negatively reversed input current of the synchronous rectifier circuit 120 begins to flow toward the 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 Figure 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 sinusoidally to 0A. 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 energized. In other words, losses due to recovery current are less likely to occur in the parallel diode Di of the high-side switch SwH in the first leg circuit 121.

[0056] In mode HA shown in Figure 2, current flows through the parallel diode Di of the low-side switch SwL in the first leg circuit 121, so the drain-source voltage is 0V. 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 the ON state, the low-side switch SwL of the first leg circuit 121 switches while the drain-source voltage is 0V. In other words, switching losses are reduced because the low-side switch SwL of the first leg circuit 121 switches to the ON state by zero-voltage switching.

[0057] As shown in the upper part of Figure 2, the short-circuit mode M2 ​​corresponds to modes A, DE, E, and HA. The other modes correspond to the power supply mode M1. In short-circuit mode M2, as shown in Figures 3 and 8, the control unit 151 controls the high-potential side low-side switch SwLH, which is one of the multiple low-side switches SwL in the multiple leg circuits, to the ON state, and is the 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. The high-potential side refers to the leg circuit of the synchronous rectifier circuit 120 that has the input terminal with the 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 that has the input terminal with the 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 called 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 short-circuit mode M2 ​​to 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 to mode C in half a cycle, and the ratio of mode E to mode G in half a cycle. Therefore, the duration of 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 predetermined before the power receiving device 100 is started up, based on the rated power of the load device 130.

[0059] The times for modes B, D, F, and H are predetermined before the power receiving device 100 is started, as the dead time for the high-side switch SwH and low-side switch SwL in the same leg circuit.

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

[0061] In other words, the first period T1 shown in Figure 2 begins at the point T1s when the low-potential side switch SwLL, which is in the off state, is controlled to the ON state. The length of the first period T1 is less than one cycle and longer than half a cycle of the operating frequency of the AC power supply unit 210, and is predetermined before the power receiving unit 100 is started up, based on the power supplied to the load unit 130 as described above.

[0062] In power supply mode M1, as shown in Figures 3, 4, 8, and 9, the control unit 151 controls the high-potential side low-side switch SwLH, which is ON in the short-circuit mode M2, to be OFF, and at the same time controls the high-side switch SwH in the leg circuit equipped with the ON-state high-potential side low-side switch SwLH to be OFF. Furthermore, after controlling the ON-state high-potential side low-side switch SwLH to be OFF, the control unit 151 controls the OFF-state high-side switch SwH to be ON for the duration of the second period T2, as shown in Figures 5 and 10. That is, when transitioning from short-circuit mode M2 ​​to power supply mode M1, the control unit 151 turns off the high-side switch SwH and rectifies via the parallel diode Di. Therefore, in the synchronous rectifier circuit 120, when the high-side switch SwH is controlled to be ON, switching losses are reduced by zero-voltage switching.

[0063] In Figure 2, the second period T2 ends at time T2e, which is longer than the first period T1 and shorter than one cycle of the operating frequency of the AC power supply unit 210, starting from the beginning T1s of the first period T1. The length of the second period T2 is predetermined before the power receiving device 100 is started, based on the first period T1 and the dead time of the mode from the end T1e of the first period T1 to the beginning T2s of the second period T2.

[0064] In this configuration, the low-potential second switch SwLL, through which current flows to the parallel diode Di, remains in the ON state, and current flows to the switch Sw in conjunction with the reversal of the AC power current. That is, the short-circuit mode M2 ​​is executed in conjunction with the reversal of the AC power current. Therefore, when the low-potential second switch SwLL turns ON, switching losses are reduced by zero-voltage switching. Furthermore, the short-circuit mode M2 ​​is executed when the parallel diode Di of the first switch SwH is not energized. As a result, recovery current is less likely 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 this disclosure can prevent large losses from occurring during switching when controlling the power supplied to the load device 130 by the short-circuit mode M2.

[0065] Furthermore, in this configuration, current flows through the first switch SwH when the high-potential low-side switch SwLH is turned off. Since 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 turns on, switching losses are reduced by zero-voltage switching. Therefore, the power receiving device 100 of this disclosure can reduce switching losses in the power supply mode M1 compared to a configuration in which the first switch SwH turns on by hard switching.

[0066] Furthermore, with this configuration, the short-circuit mode M2 ​​is executed at a period corresponding to the resonant frequency without detecting the period of the AC power. Therefore, the power receiving device 100 of this disclosure can be made less expensive than a configuration that includes a sensor for detecting the period of the AC power. Moreover, with this configuration, the first switch SwH is controlled to be in the off state after the second period when 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, switching losses can be reduced by zero-voltage switching.

[0067] B. Second Embodiment: As shown in Figure 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 rectifier element in the synchronous rectifier circuit 120. In other words, the first sensor 160 is a voltage sensor. The first sensor 160 is connected to both the drain and source terminals of the low-side switch SwL. The first sensor 160 detects the falling edge Vf of the voltage across the low-side switch SwL for the voltages of the two leg circuits. The falling edge Vf of the voltage is illustrated in Figure 2. The first sensor 160 transmits the acquired information to the control unit 151a.

[0069] Other configurations of the non-contact power supply system 10a in the second embodiment are the same as those of the non-contact power supply system 10 in the first embodiment. Note that for the configuration of the non-contact power supply system 10a in the second embodiment, configurations that differ from those of the non-contact power supply system 10 in the first embodiment are denoted by the letter "a" at the end of their reference numerals.

[0070] In the second embodiment, the control unit 151a executes short-circuit mode M2 ​​based on the detection of a voltage fall Vf by the first sensor 160. For example, as shown in the lower part of Figure 2, the control unit 151a in the second embodiment detects the voltage fall Vf at the low-side switch SwL of the second leg circuit 122. After confirming that short-circuit mode M2 ​​is being executed correctly, the control unit 151a in the second embodiment controls the low-side switch SwL of the second leg circuit 122 to the ON state for the first period T1. The control unit 151a in the second embodiment controls the low-side switch SwL of the first leg circuit 121 in the same manner.

[0071] By adopting this configuration, the power receiving device 100a of the second embodiment can control the synchronous rectifier circuit 140 more stably than the configuration without the first sensor 160. Furthermore, voltage sensors are generally less expensive than current sensors. Therefore, the power receiving device 100a of this disclosure can be made less expensive than if the first sensor 160 were a current sensor.

[0072] Furthermore, in this configuration, the high-side switch SwH is switched on and off at intervals shorter than one cycle. For example, if the high-side switch SwH is simply driven by a signal inverted from the low-side switch SwL, and the voltage rise and fall waveforms are not detected properly, the high-side switch SwH may remain in the ON state. As a result, the next voltage rise and fall may not occur, and the short-circuit mode or power supply mode may not be executed. However, in the power receiving device 100a of this disclosure, since the high-side switch SwH is switched off at intervals shorter than one cycle, such concerns do not arise, and the device can operate stably.

[0073] C. Third Embodiment: As shown in Figure 14, the power receiving device 100b of the third embodiment includes a second sensor 170 for acquiring the actual period of the AC power current, in addition to the configuration of the first embodiment. The second sensor 170 is provided in the power receiving resonant circuit 110 and 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 called the "actual period". In the first embodiment, the first period T1 and the second period T2 are predetermined 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 those of the contactless power supply system 10 of the first embodiment. Note that for the configuration of the contactless power supply system 10b of the third embodiment, configurations that differ from those of the contactless power supply system 10 of the first embodiment are denoted by the letter "b" at the end of their reference numerals.

[0075] By adopting this configuration, the short-circuit mode M2 ​​and the power supply mode M1 are executed based on the actual period. By controlling based on the period of the AC power actually acquired, the power receiving device 100 of this disclosure can execute the short-circuit mode M2 ​​and the power supply mode M1 more stably than a configuration that performs control without detecting the period of the AC power.

[0076] D. Fourth Embodiment: In the above embodiment, the synchronous rectifier circuit 120 is configured with all rectifier elements by switches Sw. However, as shown in the synchronous rectifier circuit 120c of the fourth embodiment in Figure 15, only the low-side rectifier elements may be configured by switches Sw. That is, in the synchronous rectifier circuit 120c of the fourth embodiment, the high-side rectifier elements are configured by rectifier diodes Di. In the synchronous rectifier circuit 120c of the fourth embodiment, the short-circuit mode M2 ​​is executed by the low-side switch SwL, so the short-circuit mode M2 ​​can be executed if only the low-side rectifier elements are configured by 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 those of the contactless power supply system 10 of the first embodiment. Note that for the configuration of the contactless power supply system 10c of the fourth embodiment, configurations that differ from those of the contactless power supply system 10 of the first embodiment are denoted by the letter "c" at the end of their reference numerals.

[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 by short-circuit mode M2. Furthermore, the rectifier diode Di is less likely to generate recovery current when short-circuit mode M2 ​​is executed. Moreover, 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 smaller compared to a configuration in which all rectifier elements are composed of switches Sw.

[0079] E. Variation 1: In the above embodiment, as shown in Figure 1, an example is shown in which a resonance method using a series resonant circuit power transmission resonant circuit 220 and a series resonant circuit power reception resonant circuit 110 is applied. In contrast, the following resonance methods can also be applied. However, in order to facilitate understanding of the technology, only the configurations corresponding to the power transmission resonant circuit 220 and power reception resonant circuit 110 in the first embodiment are illustrated in Figures 16 to 19.

[0080] As shown in Figure 16, the power transmission resonant circuit 220c may be a parallel resonant circuit in which the power transmission resonant capacitor 221c is connected in parallel with the power transmission coil 222, and the power receiving resonant circuit 110 may be a series resonant circuit, the same as in the first embodiment. Also, as shown in Figure 17, the power transmission resonant circuit 220d may be a circuit in which the power transmission resonant capacitor 221d is connected in series with the power transmission coil 222, and another power transmission resonant capacitor 221 is connected in parallel with the power transmission coil 222. In this case, the power receiving resonant circuit 110 is a series resonant circuit, the same as in the first embodiment. Furthermore, as shown in Figure 18, the power transmission device 200e may also be provided with a tertiary resonant circuit 310, which is a circuit independent of the power transmission resonant circuit 220e, in which a tertiary coil 311 and a tertiary resonant capacitor 312 are connected in series. The tertiary resonant circuit 310 is arranged such that the tertiary coil 311 is magnetically coupled to the power transmission coil 222 and the power receiving coil 111, respectively. Furthermore, as shown in Figure 19, the power transmission device 220f may also have a tertiary resonant circuit 310f, in which the tertiary coil 311e and the tertiary resonant capacitor 312f are connected in parallel, connected in series to the power transmission coil 222f. The tertiary resonant circuit 310f is arranged such that the tertiary coil 311f is magnetically coupled to the power transmission coil 222f and the power receiving coil 111, respectively. In the 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. Variation 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, as shown in the filter circuit FL1 in Figure 20 and the filter circuit FL2 in Figure 21. In addition to the immittance filter, the power receiving device 100 may also include a bandpass filter. Note that some parts, such as the smoothing capacitor 140 and the power receiving resonant circuit 110, are omitted from the illustration in Figures 20 and 21.

[0082] G. Variation 3: (1) In the above embodiment, the first sensor 160 is a voltage sensor. However, the first sensor 160 may also 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 duration of the short-circuit mode M2 ​​based on the power supplied to the load device 130, for example, using the first sensor 160. (2) In the above embodiment, the first sensor 160 detects the falling edge Vf of the voltage. The control unit 151 executes short-circuit mode M2 ​​based on the detection of the falling edge Vf of the voltage by the first sensor 160. However, the first sensor 160 may be provided between the drain and source of the high-side switch SwH to detect the rising edge of the voltage across the high-side switch SwH. That is, the control unit 151 may execute short-circuit mode M2 ​​based on the detection of the rising edge of the voltage by the first sensor 160. (3) In the first embodiment, the power receiving resonant capacitor 111RC comprises only the positive resonant capacitor 111RCp located on the positive line Lacp of the power receiving resonant circuit 110. However, the power receiving resonant capacitor 111RC may also comprise the negative resonant capacitor located on the negative 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 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 rectifier circuit 120 is composed of two leg circuits. However, the synchronous rectifier circuit 120 may be composed of two or more leg circuits. For example, the synchronous rectifier circuit 120 may be composed of three leg circuits and be a circuit that rectifies three-phase AC power. (6) In the above embodiment, the power supplied to the load device 130 is predetermined before the power receiving device 100 is started 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 current value obtained, for example, by having a current sensor that obtains the current flowing through the load device 130 in the power receiving device 100. More specifically, the control unit 151 determines the power supplied to the load device 130 based on the obtained current value and adjusts the first period T1 according to the rated power of the load device 130. As a result, the power receiving device 100 can efficiently supply power to the load device 130 even when the AC power received fluctuates.

[0083] This disclosure is not limited to the embodiments and modifications described above, and can be implemented in various configurations without departing from its spirit. For example, the technical features in the embodiments and modifications corresponding to the technical features in each form described in the Summary of the Disclosure section can be replaced or combined as appropriate to solve some or all of the above problems, or to achieve some or all of the above effects. Furthermore, if the technical features are not described as essential in this specification, they can be deleted as appropriate. (Form 1) A power receiving device (100, 100a, 100b, 100c) that receives AC power non-contactually using a magnetic field, A resonant circuit (110) having a predetermined resonant frequency, the resonant circuit including a receiving coil (111) that receives the AC power, It is composed of multiple leg circuits (121, 121c, 122, 122c), and a synchronous rectifier circuit (120) that rectifies the AC power into DC power, The aforementioned load device (130) that consumes DC power, The system includes a control circuit (150, 150a, 150b, 150c) for controlling the power receiving device, Each of the aforementioned multiple leg circuits is composed of a series connection of a rectifier diode (Di) or a first switch (SwH) and a second switch (SwL). The first switch and the second switch each include parallel diodes (Di) connected in parallel, The REG circuit is configured 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. The output section (110o) of the resonant circuit is connected in the leg circuit between the rectifier diode or the first switch and the second switch. The control circuit, in half a cycle of the AC power, A power supply mode (M1) in which the DC power is output from the synchronous rectifier circuit, A short-circuit mode (M2) is performed which controls the high-potential side second switch (SwLH), which is one of the multiple second switches in the multiple leg circuits to which a voltage is applied in the reverse direction of the parallel diode, to be in the ON state. The short-circuit mode is a power receiving device that controls a low-potential side second switch (SwLL), which is one of the plurality of second switches through which current flows in the parallel diode, to be in the ON state for a first period that is shorter than one cycle of the AC power and longer than half a cycle. (Form 2) The power receiving device according to Embodiment 1, further, The aforementioned leg circuit is configured by connecting the first switch and the second switch in series. The aforementioned power supply mode is, When controlling the ON-state high-potential-side second switch among the plurality of second switches to an OFF state, the first switch in the leg circuit equipped with the ON-state high-potential-side second switch is controlled to be in an OFF state. A power receiving device that controls the high-potential second switch, which is in the ON state, to be in the OFF state, and then controls the first switch, which is in the OFF state, to be in the ON state for a second period of time. (Form 3) The power receiving device according to Embodiment 2, further, The circuit includes a first sensor (160) for detecting the voltage of the synchronous rectifier circuit, The first sensor detects the rising edge of the voltage across the first switch or the falling edge of the voltage across the second switch for the voltages of the plurality of leg circuits. The control circuit is a power receiving device that executes the short-circuit mode on the condition that the first sensor detects the rising or falling of the voltage. (Form 4) A power receiving device according to Embodiment 2, The system includes a second sensor (170) that acquires 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 time that is longer than the first period but shorter than one cycle of the actual period, starting from the point at which the off state of the low-potential side second switch is turned on, which is the start of the first period. (Form 5) A power receiving device according to Embodiment 3, The control circuit controls the end of the second period to be a time that is longer than the first period but shorter than one cycle, starting from the point at which the off state of the low-potential side second switch is turned on, which is the start of the first period. [Explanation of symbols]

[0084] 10, 10a, 10b, 10c… Contactless power supply system, 100, 100a, 100b, 100c… Power receiving device, 110… Power receiving resonant 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-contactually using a magnetic field, A resonant circuit (110) having a predetermined resonant frequency, the resonant circuit including a power receiving coil (111) that receives the AC power, It is composed of multiple leg circuits (121, 121c, 122, 122c), and a synchronous rectifier circuit (120) that rectifies the AC power into DC power, The aforementioned load device (130) that consumes DC power, The system includes a control circuit (150, 150a, 150b, 150c) for controlling the power receiving device, Each of the aforementioned multiple leg circuits is composed of a rectifier diode (Di) or a first switch (SwH) and a second switch (SwL) connected in series. The first switch and the second switch each include parallel diodes (Di) connected in parallel, The REG circuit is configured 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. The output section (110o) of the resonant circuit is connected in the leg circuit between the rectifier diode or the first switch and the second switch. The control circuit, in half a cycle of the AC power, A power supply mode (M1) in which the DC power is output from the synchronous rectifier circuit, A short-circuit mode (M2) is performed which controls the high-potential side second switch (SwLH), which is one of the multiple second switches in the multiple leg circuits to which a voltage is applied in the reverse direction of the parallel diode, to be in the ON state. A power receiving device that controls the low-potential side second switch (SwLL), which is one of the plurality of second switches in the short-circuit mode and through which current flows to the parallel diode, to be in the ON state for a first period that is shorter than one cycle of the AC power and longer than half a cycle.

2. The power receiving device according to claim 1, further, The aforementioned leg circuit is configured by connecting the first switch and the second switch in series. The aforementioned power supply mode is, When controlling the ON state high-potential side second switch among the plurality of second switches to the OFF state, the first switch in the leg circuit equipped with the ON state high-potential side second switch is controlled to be in the OFF state. A power receiving device that controls the high-potential second switch, which is in the ON state, to be in the OFF state, and then controls the first switch, which is in the OFF state, to be in the ON state for a second period of time.

3. The power receiving device according to claim 2, further, The circuit includes a first sensor (160) for detecting the voltage of the synchronous rectifier circuit, The first sensor detects the rising edge of the voltage across the first switch or the falling edge of the voltage across the second switch for the voltages of the plurality of leg circuits. The control circuit is a power receiving device that executes the short-circuit mode on the condition that the first sensor detects the rising or falling of the voltage.

4. A power receiving device according to claim 2, The system includes 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 time that is longer than the first period but shorter than one cycle of the actual period, starting from the point at which the off state of the low-potential side second switch is turned on, which is the start of the first period.

5. A power receiving device according to claim 3, The control circuit controls the end of the second period to be a time that is longer than the first period but shorter than one cycle, starting from the point at which the off state of the low-potential side second switch is turned on, which is the start of the first period.

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