Power reception device

Abstract

Provided is a power reception device (100) that receives AC power in a contactless manner, the power reception device (100) comprising: a resonance circuit (110) that receives AC power; a rectification circuit (120); a load device (130); an adjustment circuit (140) provided with a switch (Sw) that short-circuits between input terminals of the rectification circuit, the adjustment circuit adjusting supply power (Pa); a power reception sensor (160); and a control circuit (150). The control circuit is provided with a short-circuit mode and a power feeding mode. The control circuit performs control so that a power feeding ratio (D), which is the ratio of power feeding periods, becomes less than a minimum target ratio (Dm), which is the minimum value of a target ratio (Dt) corresponding to a state of resonance or coupling in which the supply power can reach a predetermined target power (Pt), until AC power starts to be received according to the power reception sensor, and also performs control so that the power feeding ratio is increased to the target ratio or lower after power reception has been detected by the power reception sensor.

Description

Powered Device CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based on and claims the benefit of priority from patent application serial number 2023-216380, filed December 22, 2023, the entire contents of which are incorporated herein by reference.

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

[0003] In a power receiving device of a contactless power transfer system, as in Patent Document 1, for example, a switching element may be used in a rectifier circuit that rectifies received AC power. In the following description, the switching element is referred to as a switch. In Patent Document 1, a resonant circuit that receives AC power is connected to a load via a rectifier circuit. The technology of Patent Document 1 controls the rectifier circuit with a switch to control the period during which DC power is supplied to the load and the period during which AC power is circulated between the resonant circuit and the rectifier circuit. In other words, the power receiving device in Patent Document 1 controls the DC power supplied to the load.

[0004] Patent No. 6240503

[0005] When the load is a battery, the DC power supplied to the load is controlled to prevent overcharging, for example. More specifically, when the received power is excessive, the DC power supplied to the load is controlled by suppressing the received power so that only the power necessary to charge the battery is supplied.

[0006] In a contactless power transfer system, the received power depends on the resonance or coupling state of a resonant circuit, which is related to the relative positions of the power receiving device and the power transmitting device. In other words, it is difficult for the power receiving device to predict the received power in advance. Therefore, the power receiving device must check the received power before starting to control the DC power supplied to the load. When the load is a battery, a power receiving device within the power transmitting device's power transmission distance starts receiving power only if the remaining battery charge is insufficient. However, checking the received power delays the control of the DC power supplied to the load. As a result, the DC power supplied to the load temporarily becomes excessive as inrush power, exceeding the power required to charge the battery. Inrush power may, for example, cause deterioration of the battery serving as the load or deterioration of electromagnetic compatibility (EMC). Therefore, a technology for preventing inrush power in a power receiving device of a contactless power transfer system has been desired.

[0007] The present disclosure can be realized in the following forms. According to one form of the present disclosure, there is provided a power receiving device that receives AC power contactlessly using a magnetic field. The power receiving device includes: a resonant circuit including a power receiving coil that receives the AC power, the resonant circuit varying the magnitude of the AC power depending on a state of resonance or coupling; a rectifier circuit that converts the AC power into DC power; a load device that consumes the DC power; an adjustment circuit having a switch that shorts between input terminals of the rectifier circuit, the adjustment circuit adjusting supply power of the AC power to be supplied to the load device between the power receiving coil and the load device; a power receiving sensor that detects reception of the AC power or the DC power; and a control circuit that controls the power receiving device. and a power supply mode in which the terminals are opened during a power supply period of the half cycle excluding the short circuit period, and the power receiving sensor controls the power supply rate, which is the rate of the power supply period in the half cycle, to be smaller than a minimum target rate, which is the minimum value of the target rate according to the state of the resonance or the coupling that can make the supplied power a predetermined target power, before the start of reception of the AC power, and after detecting the reception of the AC power, the power receiving sensor controls the power supply rate to be equal to or less than the target rate.

[0008] In this configuration, the power receiving device of the present disclosure receives different power depending on the resonance state or magnetic coupling state of the resonant circuit. Therefore, the power feeding rate at which the supplied power reaches the target power also varies depending on the resonance or coupling state. Furthermore, in this configuration, the power receiving device of the present disclosure may receive power while the load device starts consuming DC power. Therefore, the power receiving device of the present disclosure starts receiving power after reducing the power feeding rate below the minimum target rate, thereby preventing inrush power exceeding the target power even when the load device starts consuming DC power. Furthermore, the power receiving device of the present disclosure increases the power feeding rate after DC power consumption starts, thereby efficiently supplying power to the load device while suppressing inrush power.

[0009] The above and other objects, features, and advantages of the present disclosure will become more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which Fig. 1 is an explanatory diagram showing the configuration of a contactless power transfer system according to a first embodiment, Fig. 2 is an explanatory diagram showing a power transfer mode, Fig. 3 is an explanatory diagram showing a short-circuit mode, Fig. 4 is an explanatory diagram showing a power transfer mode, Fig. 5 is an explanatory diagram showing a short-circuit mode, Fig. 6 is an explanatory diagram showing received power, Fig. 7 is an explanatory diagram showing supplied power at the start of power reception, Fig. 8 is a flowchart showing control processing by a control circuit, Fig. 9 is a block diagram showing the configuration of a control system according to a second embodiment, Fig. 10 is an explanatory diagram showing a power receiving device according to a fourth embodiment, Fig. 11 is an explanatory diagram showing a filter circuit according to a modified example, Fig. 12 is an explanatory diagram showing a filter circuit according to a modified example, and Fig. 13 is an explanatory diagram showing received power according to a modified example.

[0010] A. First Embodiment: A-1. Device Configuration: A contactless power transfer system 10 shown in Fig. 1 supplies power to a load device 130 in a contactless manner using a magnetic field. As shown in Fig. 1, the contactless power transfer system 10 includes a power transmission device 200 and a power receiving device 100. The contactless power transfer system 10 supplies power from the power transmission device 200 to the power receiving device 100 in a contactless manner. The contactless power transfer system 10 supplies power in a contactless manner to the power receiving device 100 mounted on a vehicle, for example.

[0011] The power transmitting device 200 uses a magnetic field to contactlessly supply AC power to the power receiving device 100. The power transmitting device 200 includes an AC power supply device 210 and a power transmitting resonant circuit 220.

[0012] The AC power supply device 210 supplies AC power of a predetermined operating frequency to the power transmission resonant 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, and converts AC power supplied from a power grid into DC power. The power transmission circuit is an inverter that converts DC power supplied from the power supply circuit into AC power of the operating frequency. The operating frequency is set according to a resonant frequency, which will be described later. In this embodiment, the operating frequency of the AC power supply device 210 is, for example, 85 kHz, and is set using a predetermined power transmission frequency stipulated by the Radio Law or the like.

[0013] The power transmitting resonant circuit 220 is magnetically coupled to and resonates with the power receiving coil 111. The power transmitting resonant circuit 220 includes a power transmitting coil 222 and a power transmitting resonant capacitor 221 connected in parallel to the power transmitting coil 222. In other words, the power transmitting resonant circuit 220 is a parallel resonant circuit.

[0014] The power transmitting resonant capacitor 221 resonates the power transmitting resonant circuit 220 with AC power at the operating frequency when the power transmitting coil 222 and the power receiving coil 111 are magnetically coupled. That is, the capacitance of the power transmitting resonant capacitor 221 is set so that the operating frequency and the resonant frequency of the power transmitting resonant circuit 220 approximately match when the power transmitting coil 222 and the power receiving coil 111 are magnetically coupled.

[0015] The power transmitting coil 222 generates a magnetic field corresponding to the operating frequency of the AC power supply device 210. Furthermore, the power transmitting coil 222 transmits AC power to the power receiving coil 111 by magnetically coupling with the power receiving coil 111. In other words, the power transmitting coil 222 transmits power contactlessly by utilizing the electromagnetic induction phenomenon.

[0016] The power transmitting coil 222 is used by being laid on the ground. More specifically, the power transmitting coil 222 is laid on the ground in an orientation that allows it to face the power receiving coil 111 mounted on the vehicle. The positional relationship between the power transmitting coil 222 and the power receiving coil 111 will be described in detail later.

[0017] The power receiving device 100 receives AC power from the power transmitting device 200 in a contactless manner using a magnetic field. The power receiving device 100 includes a power receiving resonant circuit 110, a synchronous rectifier circuit 120, a load device 130, an adjustment circuit 140, a power receiving sensor 160, a control circuit 150, and a smoothing capacitor 170. The power receiving device 100 is mounted on a vehicle.

[0018] The power receiving resonant circuit 110 is magnetically coupled to and resonates with the power transmitting coil 222. It includes a power receiving coil 111 and a power receiving resonant capacitor 112 connected in series to the power receiving coil 111. In other words, the power receiving resonant circuit 110 is a series resonant circuit.

[0019] The power receiving coil 111 is magnetically coupled to the power transmitting coil 222 by receiving the magnetic field emitted by the power transmitting coil 222. The power receiving coil 111 is mounted on the vehicle facing the ground. The power receiving coil 111 faces the power transmitting coil 222 laid on the ground, and receives the magnetic field emitted by the power transmitting coil 222. In this specification, the power receiving coil 111 receives AC power from the power receiving device 100 in a wireless manner. In this specification, the AC power received by the power receiving coil 111 is referred to as received power Pr.

[0020] The power receiving resonant capacitor 112 resonates the power receiving resonant circuit 110 with AC power at the operating frequency when the power receiving coil 111 and the power transmitting coil 222 are magnetically coupled. That is, the capacitance of the power receiving resonant capacitor 112 is set so that the operating frequency and the resonant frequency of the power receiving resonant circuit 110 approximately match when the power transmitting coil 222 and the power receiving coil 111 are magnetically coupled.

[0021] The received power Pr varies depending on the state in which the receiving coil 111 and the transmitting coil 222 are magnetically coupled and the state of resonance of the receiving resonant circuit 110. That is, the received power Pr also varies depending on the relationship between the operating frequency and the resonant frequency. However, to facilitate understanding of the technology, the description in this specification will be given assuming that the operating frequency and the resonant frequency match. The relationship between the state in which the receiving coil 111 and the transmitting coil 222 are magnetically coupled and the received power Pr will be described later.

[0022] In this embodiment, the power receiving resonant capacitor 112 includes a first capacitor 112P on the positive side and a second capacitor 112N on the negative side. By providing resonant capacitors on both the positive and negative sides, common mode noise can be suppressed. In this specification, the power receiving resonant circuit 110 is also simply referred to as a resonant circuit.

[0023] The synchronous rectifier circuit 120 converts the received AC power into DC power. In this embodiment, the synchronous rectifier circuit 120 is a single-phase rectifier circuit that uses four MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors) as rectifier elements. The synchronous rectifier circuit 120 includes two leg circuits: a first leg circuit 121 and a second leg circuit 122. The synchronous rectifier circuit 120 is also simply referred to as the rectifier circuit 120.

[0024] The leg circuit has two switches Sw connected in series. Furthermore, the leg circuit connects the positive line Lp and negative line Ln 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. In other words, the position of the input terminal of the synchronous rectifier circuit 120 is between the two switches Sw of the leg circuit. Note that with regard to the input terminal 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.

[0025] The two switches Sw in the leg circuit are configured by a first switch SwH as a rectifying element on the positive line Lp side and a second switch SwL as a rectifying element on the negative line Ln side. That is, the switches Sw configure all of the rectifying elements in the synchronous rectifier circuit 120.

[0026] The switch Sw of the leg circuit includes a parallel diode Di connected in parallel in a reverse direction relative to the forward direction of the switch Sw. The parallel diode Di is, for example, a body diode of a MOSFET. That is, the drain of the switch Sw is disposed on the positive line Lp side, and the source of the switch Sw is disposed on the negative line Ln 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 switch Sw is connected to the control circuit 150. The switch Sw is driven by receiving a voltage at its gate in response to a command from the control circuit 150.

[0027] In this specification, the positive line Lp side is also referred to as the high side, and the negative line Ln side is also referred to as the low side. Therefore, the first switch SwH is also referred to as the high-side switch SwH, and the second switch SwL is also referred to as the low-side switch SwL.

[0028] That is, the synchronous rectifier circuit 120 rectifies, by the switch Sw, the AC power input from the power receiving resonant circuit 110. The DC power rectified by the synchronous rectifier circuit 120 is output to the load device 130 via the positive line Lp and the negative line Ln.

[0029] The adjustment circuit 140 adjusts the supply power Pa to be supplied to the load device 130, out of the received power Pr, which is AC power, between the receiving coil 111 and the load device 130. The adjustment circuit 140 includes a switch Sw that shorts the input terminals of the synchronous rectifier circuit 120. The switch Sw of the adjustment circuit 140 also serves as the low-side switch SwL of the synchronous rectifier circuit 120.

[0030] The adjustment circuit 140 shorts the input terminals of the synchronous rectifier circuit 120 by turning on the two low-side switches SwL of the synchronous rectifier circuit 120. As a result, AC power is not rectified by the synchronous rectifier circuit 120. The adjustment circuit 140 opens the input terminals of the synchronous rectifier circuit 120 by turning off at least one of the two low-side switches SwL of the synchronous rectifier circuit 120. As a result, the AC power is rectified by the synchronous rectifier circuit 120 and output as DC power from the synchronous rectifier circuit 120. In this specification, a state in which the input terminals of the synchronous rectifier circuit 120 are short-circuited by the adjustment circuit 140 is referred to as a short-circuit mode. A state in which the input terminals of the synchronous rectifier circuit 120 are open by the adjustment circuit 140 is referred to as a power supply mode. Each mode will be described in detail later.

[0031] The smoothing capacitor 170 is connected in parallel between the output of the synchronous rectifier circuit 120 and the load device 130. The smoothing capacitor 170 smoothes the DC current and DC voltage supplied to the load device 130.

[0032] The power receiving sensor 160 detects the reception of DC power. More specifically, the power receiving sensor 160 detects the current flowing through the load device 130 due to the received power. In other words, the power receiving sensor 160 is a current sensor that measures the current value of the DC power. The power receiving sensor 160 is connected in series with the output of the synchronous rectifier circuit 120 and 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. The load device 130 is charged by receiving the supply power Pa output from the synchronous rectifier circuit 120. The power charged in the load device 130 is used, for example, in a vehicle in which the power receiving device 100 is installed.

[0034] The load device 130 starts consuming DC power based on a predetermined standard related to power. That is, the load device 130 does not always charge. For example, a load device 130 including a battery starts charging when the remaining charge falls below a certain standard value to prevent overcharging. In this way, the load device 130 may not consume DC power when the power receiving device 100 is receiving power. Furthermore, the load device 130 may start consuming DC power when the power receiving device 100 is receiving power. The consumption of DC power during power reception will be described in detail later.

[0035] The supply power Pa supplied to the load device 130 is power adjusted by the adjustment circuit 140 based on the target power Pt. For example, in the case of a load device 130 that includes a battery, the target power Pt is determined based on the rated current of the battery. When an overcurrent flows through the battery, the battery generates excessive heat. This can shorten the battery's lifespan. For this reason, the target power Pt is determined to be a power that satisfies a current value equal to or less than the rated current. Alternatively, the battery may have a protection circuit that cuts off the flow of current at a current lower than the rated current of the battery.

[0036] The control circuit 150 controls the power receiving device 100. The control circuit 150 includes a control unit 151 and a drive circuit 152.

[0037] The drive circuit 152 drives the switch Sw. More specifically, the drive circuit 152 outputs power required to drive the switch Sw in response to a command from the control unit 151. The drive circuit 152 is connected to the gates of all the switches Sw in the synchronous rectifier circuit 120. The drive circuit 152 drives the switch Sw by applying a gate voltage required for turning the switch Sw on and off to the gate of the switch Sw. Note that in FIG. 1 , the connection between the drive circuit 152 and the gate is omitted to facilitate understanding of the technology.

[0038] The control unit 151 generates a signal that controls the on / off operation of the switch Sw. The control unit 151 is mainly configured, for example, with a microcomputer, and includes a CPU, ROM, RAM, etc. (not shown). The control unit 151 includes an adjustment unit 151a as a functional unit. The function of the adjustment unit 151a will be described later. The control unit 151 is connected to the power receiving sensor 160. The control unit 151 executes the short-circuit mode and the power supply mode based on the current value acquired by the power receiving sensor 160.

[0039] A-2. Short-Circuit Mode and Power Supply Mode: The control circuit 150 has a short-circuit mode and a power supply mode as control modes. The control circuit 150 executes the short-circuit mode, shorting the input terminals of the synchronous rectifier circuit 120 during a predetermined short-circuit period for each half cycle of one cycle Ca of AC power. The control circuit 150 executes the power supply mode, opening the terminals during the power supply period of the half cycle Ca excluding the short-circuit period. The operation of the power receiving device 100 in the short-circuit mode and power supply mode during one cycle Ca of AC power will be described using FIGS. 2 to 5. In FIGS. 2 to 5, the waveform of the AC current during one cycle Ca is illustrated at the top, and a circuit diagram of the power transmitting device 200 is illustrated at the bottom. However, to facilitate understanding of the technology, some components, such as the power receiving resonant circuit 110, the smoothing capacitor 170, and the control circuit 150, are omitted from the illustration.

[0040] 2 , the direction of AC current flowing through the synchronous rectifier circuit 120 during period a of the power supply mode in the positive half cycle of the AC power is indicated by an arrow Aia. During period a, the control circuit 150 controls at least the low-side switch SwL of the first leg circuit 121, of the two switches Sw of the adjustment circuit 140, to an off state. As a result, AC current flows to the load device 130 via the high-side switch SwH of the first leg circuit 121. In other words, received power Pr is supplied to the load device 130.

[0041] 3 , the direction of AC current flowing through the synchronous rectifier circuit 120 during period b of the short-circuit mode in the positive half cycle of the AC power is indicated by an arrow Aib. During period b, the control circuit 150 controls at least the low-side switch SwL of the first leg circuit 121, of the two switches Sw of the adjustment circuit 140, to an on state. Since the terminals P1 and P2 of the input of the synchronous rectifier circuit 120 are short-circuited, AC current does not flow to the load device 130. In other words, received power Pr is not supplied to the load device 130.

[0042] 4 , the direction of AC current flowing through the synchronous rectifier circuit 120 during period c of the power supply mode in the negative half cycle of the AC power is indicated by an arrow Aic. During period c, the control circuit 150 controls at least the low-side switch SwL of the second leg circuit 122, of the two switches Sw of the adjustment circuit 140, to an off state. As a result, AC current flows to the load device 130 via the high-side switch SwH of the second leg circuit 122. In other words, received power Pr is supplied to the load device 130.

[0043] 5 , the direction of AC current flowing through the synchronous rectifier circuit 120 during period d of the short-circuit mode in the negative half cycle of the AC power is indicated by an arrow Aid. During period d, the control circuit 150 controls at least the low-side switch SwL of the second leg circuit 122, of the two switches Sw of the adjustment circuit 140, to an on state. Since the terminals P1 and P2 of the input of the synchronous rectifier circuit 120 are short-circuited, AC current does not flow to the load device 130. In other words, received power Pr is not supplied to the load device 130.

[0044] In this specification, periods b and d are periods in short circuit mode and are referred to as short circuit periods. Periods a and c are periods in power supply mode and are referred to as power supply periods. The control circuit 150 executes the short circuit mode during the short circuit period and the power supply mode during the power supply period for each half cycle of one cycle Ca of the AC power. The control circuit 150 adjusts the supply power Pa supplied to the load device 130 by executing the short circuit mode or the power supply mode to achieve a predetermined target power Pt.

[0045] A-3. Method of adjusting power supply: The upper part of Fig. 6 illustrates a state in which power receiving coil 111 and power transmitting coil 222 are directly opposite each other. Note that Fig. 6 also illustrates a state in which power receiving coil 111, which is mounted on a vehicle and therefore located away from the ground, and power transmitting coil 222, which is laid on the ground, are viewed from the side.

[0046] The received power Pr varies depending on the state of magnetic coupling between the receiving coil 111 and the transmitting coil 222. More specifically, the received power Pr depends on the relative position of the receiving coil 111 with respect to the transmitting coil 222. In the center of FIG. 6 , the relationship between the relative position of the receiving coil 111 with respect to the transmitting coil 222 and the magnitude of the received power Pr is shown by a solid line. In this embodiment, the directly facing state is a state in which the central axis CL1 of the receiving coil 111 and the central axis CL2 of the transmitting coil 222 coincide and face each other. As shown in FIG. 6 , the received power Pr is greatest in the directly facing state. The greatest power among the received powers Pr is referred to as maximum power Pm. The received power Pr decreases as the distance from the directly facing state increases.

[0047] The supply power Pa is adjusted by the adjustment circuit 140. More specifically, the supply power Pa is adjusted by the adjustment circuit 140 executing a power supply mode or a short-circuit mode in response to a command from the control circuit 150. The control circuit 150 adjusts the supply power Pa by changing the proportion of the power supply period in a half cycle of the AC power. The proportion of the power supply period in a half cycle is called a power supply proportion D or duty D.

[0048] The lower part of Fig. 6 illustrates the relationship between the relative position of the power receiving coil 111 with respect to the power transmitting coil 222 and the power supply rate D for adjusting the supplied power Pa to the target power Pt. At any power receiving position, the rate for adjusting the supplied power Pa to the target power Pt is called the target rate Dt. The solid line at the bottom of Fig. 6 indicates the target rate Dt.

[0049] In order to match the supply power Pa with the target power Pt, it is necessary to minimize the power supply rate D when the received power Pr is the maximum power Pm. In this specification, the power supply rate D is referred to as the minimum target rate Dm. That is, the minimum target rate Dm is determined based on the maximum power Pm and the target power Pt. However, to facilitate adjustment of the supply power Pa, it is preferable that the target power Pt be 80% or less of the maximum power Pm. In the lower part of FIG. 6, the minimum target rate Dm is set to 0.5 as an example.

[0050] Furthermore, in order to match the supply power Pa with the target power Pt, the power supply rate D needs to be increased as the received power Pr deviates from the maximum power Pm. However, the received power Pr may fall below the target power Pt depending on the relative position of the power receiving coil 111 with respect to the power transmitting coil 222. In this case, the control circuit 150 sets the power supply rate D to the maximum value. In other words, the control circuit 150 does not execute the short-circuit mode. Therefore, as shown by the solid line at the bottom of FIG. 6 , the target rate Dt becomes the maximum power supply rate D at a position where the received power Pr is below the target power Pt.

[0051] The upper part of FIG. 7 illustrates a state in which the central axis CL1 and the central axis CL2 are misaligned, and the power receiving coil 111 and the power transmitting coil 222 face each other. The center of FIG. 7 illustrates the received power Pr in the state of the power receiving coil 111 and the power transmitting coil 222 shown in the upper part of FIG. 7. The lower part of FIG. 7 illustrates the supplied power Pa from the start of power reception until a steady state is reached. As described above, the load device 130 may start consuming DC power while receiving power. In this case, the control circuit 150 detects the received power Pr using the power receiving sensor 160 and then starts adjusting the supplied power Pa using the adjustment circuit 140. In other words, the supplied power Pa is adjusted to match the target power Pt with a delay after the start of power reception. Therefore, as shown by the curve C1 in the lower part of FIG. 7, if control by the control circuit 150, described below, is not performed, the supplied power Pa exceeds the target power Pt and reaches the received power Pr immediately after the start of power reception. In this specification, the phenomenon in which the supplied power Pa exceeds the target power Pt immediately after the start of power reception, as shown by the curve C1, is called inrush power or power overshoot.

[0052] 7 shows the transition of the supplied power Pa when inrush power is being suppressed by the control circuit 150. The control by the control circuit 150 will be described below.

[0053] A-4. Control method of power receiving device: The processing performed by the control circuit 150 will be described with reference to Fig. 8. The control circuit 150 starts processing when the power receiving device 100 is started. The power receiving device 100 is started, for example, when the control circuit 150 receives a power supply from a vehicle in which the power receiving device 100 is mounted.

[0054] In step S100 of Fig. 8 , the control circuit 150 adjusts the power supply ratio D using the power receiving sensor 160 before the start of AC power reception. More specifically, the control circuit 150 controls the power supply ratio D to a ratio Ds that is smaller than the minimum target ratio Dm, which is the minimum value of the target ratio Dt according to the coupling state that can make the supplied power Pa equal to the predetermined target power Pt. As described above, the minimum target ratio Dm is determined based on the maximum power Pm and the target power Pt. For example, as shown in the lower part of Fig. 6 , the control circuit 150 sets the power supply ratio D to a ratio Ds that is smaller than the minimum target ratio Dm of 0.5.

[0055] 7, when supply power Pa is generated, the supply power Pa becomes lower than the target power Pt due to the power supply rate D being a rate Ds that is lower than the minimum target rate Dm. Therefore, in the power receiving device 100, even if the load device 130 starts consuming DC power while receiving power, the supply power Pa does not exceed the target power Pt. In other words, no inrush power occurs in the power receiving device 100.

[0056] 8, the control circuit 150 determines whether power is being received using the power receiving sensor 160. If the control circuit 150 detects that power is being received, the process proceeds to S300. If the control circuit 150 does not detect that power is being received, the process of step S200 is repeated.

[0057] 8 , the control circuit 150 determines whether the load device 130 has started consuming DC power. The control circuit 150 determines whether the load device 130 has started consuming DC power, for example, based on a current value acquired by the power receiving sensor 160. If the load device 130 has started consuming DC power, the control circuit 150 proceeds to step S400. If the load device 130 has not started consuming DC power, the control circuit 150 returns the process to step S200.

[0058] 8 , the control circuit 150 controls the power receiving sensor 160 to increase the power supply rate D to the target rate Dt after DC power consumption starts. That is, the control circuit 150 increases the power supply rate D, which is a rate Ds smaller than the minimum target rate Dm, based on the target rate Dt, thereby increasing the supply power Pa to the target power Pt. This allows the power receiving device 100 to supply the load device 130 with supply power Pa that satisfies the target power Pt while preventing inrush power.

[0059] The functional unit that performs step S100 in the control unit 151 is the adjustment unit 151a. The adjustment unit 151a determines the power supply ratio D based on the current value of the DC power. More specifically, the adjustment unit 151a determines the power supply ratio D by PI control based on the difference between the current value Ib flowing through the load device 130 and the current value It based on the target power Pt. The current value Ib flowing through the load device 130 is a current value acquired by the power receiving sensor 160. The current value It is determined by the control unit 151 based on the predetermined target power Pt.

[0060] 8 , the control circuit 150 determines whether the load device 130 should stop consuming DC power. The control circuit 150 determines whether the load device 130 should stop consuming DC power, for example, based on a current value acquired by the power receiving sensor 160. If the load device 130 is consuming DC power, the control circuit 150 repeats step S500. If the load device 130 is not consuming DC power, the control circuit 150 proceeds to step S600.

[0061] 8 , the control circuit 150 determines whether to stop the power receiving device 100. The control circuit 150 receives a command to stop the power receiving device 100 from, for example, a control device of a vehicle equipped with the power receiving device 100. If the control circuit 150 does not receive a command to stop the power receiving device 100, the control circuit 150 proceeds to step S700. If the control circuit 150 receives a command to stop the power receiving device 100, the control circuit 150 ends the process.

[0062] 8, the control circuit 150 returns the power supply rate D to the rate Ds set in step S100. That is, the control circuit 150 performs control to set the power supply rate D to a rate Ds that is smaller than the minimum target rate Dm among the target rates Dt according to the coupling state that can make the supply power Pa equal to the predetermined target power Pt. After processing step S700, the control circuit 150 returns the processing to step S200.

[0063] That is, in this configuration, the power received by the power receiving device 100 of the present disclosure varies depending on the resonance state or the magnetic coupling state of the resonant circuit. Therefore, the power supply rate D at which the supply power Pa becomes the target power Pt also varies depending on the resonance or coupling state. Furthermore, in this configuration, the power receiving device 100 of the present disclosure may receive power while the load device 130 starts consuming DC power. Therefore, the power receiving device 100 of the present disclosure starts receiving power after setting the power supply rate D to be lower than the minimum target rate Dm, thereby preventing inrush power exceeding the target power Pt even when the load device 130 starts consuming DC power. Furthermore, the power receiving device 100 of the present disclosure increases the power supply rate D after DC power consumption starts, thereby efficiently supplying power to the load device 130 while suppressing inrush power.

[0064] Furthermore, in this configuration, the rectifier circuit 120 can also function as the adjustment circuit 140. In other words, the power receiving device 100 of the present disclosure does not need to be configured with the adjustment circuit 140 and the rectifier circuit 120 separately, which allows for reduced costs and size of the device. Note that a configuration in which the adjustment circuit 140 and the rectifier circuit 120 are configured separately will be described later.

[0065] B. Second Embodiment The control circuit 150 of the first embodiment may further include a limiter 151b. The limiter 151b limits the power supply ratio D determined by the adjustment unit 151a. In addition, the limiter 151b relaxes the limit at a slower rate than the rate at which the adjustment unit 151a determines the power supply ratio D. As shown in FIG. 9 , the limiter 151b is disposed between the adjustment unit 151a and the adjustment circuit 140 in the control system of the power receiving device 100.

[0066] As described above, the adjustment unit 151a determines the power supply ratio D by PI control based on the difference between the current value Ib flowing through the load device 130 and the current value It based on the target power Pt. The limiter 151b receives a command from the adjustment unit 151a to control the adjustment circuit 140. The command from the adjustment unit 151a to control the adjustment circuit 140 is specifically a command to determine the power supply ratio D. This causes the adjustment circuit 140 to control the off-time of the switch Sw. The control speed of the limiter 151b is measured by comparing the changes in the signals of the adjustment unit 151a and the limiter 151b with an oscilloscope.

[0067] With this configuration, the power supply rate D corresponding to the fluctuating power is limited by the limiter 151b. Furthermore, the relaxation of the limit by the limiter 151b is slower than the determination of the power supply rate D. For example, when the received power fluctuates due to a disturbance, the power receiving device 100 according to the present disclosure does not fluctuate the power supply rate D according to the fluctuation in power. Therefore, the power receiving device 100 according to the present disclosure can stably control the suppression of inrush power.

[0068] C. Third Embodiment In the above embodiments, the control circuit 150 can also execute the short circuit mode and the power supply mode as follows. The control circuit 150 executes the short circuit mode and the power supply mode using the power receiving sensor 160, with the low-side switch SwL and the parallel diode Di connected in parallel to the high-side switch SwH, during a first time period that includes the start of power reception. That is, the control circuit 150 rectifies the received power Pr using the parallel diode Di by controlling the high-side switch SwH to an off state during the first time period that includes the start of power reception.

[0069] Furthermore, when the power receiving sensor 160 detects a predetermined reference current in a second time period after the first time period, the control circuit 150 controls the low-side switch SwL and the high-side switch SwH to execute the short-circuit mode and the power supply mode. That is, the control circuit 150 starts the on / off operation of the high-side switch SwH to rectify the AC power. The reference current is, for example, 20% of the current value at the target power Pt.

[0070] With this configuration, the power receiving device 100 of the present disclosure rectifies AC power using the first switch SwH on the positive line Lp side when a current greater than or equal to the reference current flows through the power receiving device 100. For example, a switch Sw such as a MOSFET may distort the voltage between its drain and source when a low current flows between the drain and source. In this case, if the MOSFET's on / off state is determined using the voltage between its drain and source, the distortion of the voltage between its drain and source may cause unstable control. The power receiving device 100 of the present disclosure performs rectification using the parallel diode Di of the first switch SwH at the start of power reception, when the current flowing through the switch is small, thereby achieving more stable rectification than a configuration in which rectification is performed using the first switch SwH.

[0071] D. Fourth Embodiment: In the first embodiment, the adjustment circuit 140 is configured by the switch Sw of the synchronous rectifier circuit 120. However, the adjustment circuit 140 may be configured separately from the synchronous rectifier circuit 120. FIG. 10 illustrates an adjustment circuit 140x that is separated from the rectifier circuit 120x and includes a switch Swx that shorts the input terminals of the rectifier circuit 120. More specifically, the switch Swx of the adjustment circuit 140x is connected in parallel to the power receiving resonant circuit 110 and the rectifier circuit 120x, between the power receiving resonant circuit 110 and the rectifier circuit 120x. A semiconductor relay is used for the switch Swx. Note that components different from the first embodiment are designated by the symbols of the first embodiment with an x ​​added.

[0072] When the adjustment circuit 140x is configured separately from the rectifier circuit 120x, the rectifier circuit 120x may be configured only with rectifier diodes. FIG. 10 illustrates a configuration in which the rectifier circuit 120x is configured only with rectifier diodes. In this case, the drive circuit 152 of the control circuit 150 of the fourth embodiment controls only the adjustment circuit 140x. When the power supply mode is executed by the adjustment circuit 140x of the fourth embodiment, as indicated by arrow D1 in FIG. 10 , the positive current of the AC power flows to the load device 130 via the rectifier diode on the positive line Lp side of the rectifier circuit 120x. When the short-circuit mode is executed by the adjustment circuit 140x of the fourth embodiment, as indicated by arrow D2 in FIG. 10 , the positive current of the AC power does not flow through the rectifier circuit 120x but returns to the power receiving resonant circuit 110 via the switch Swx of the adjustment circuit 140x. Similarly, the negative current of the AC power flows in both the power supply mode and the short-circuit mode.

[0073] By adopting such a configuration, the power receiving device 100x of the present disclosure can more easily achieve control for adjusting the supply power Pa than a configuration in which the adjustment circuit 140 is configured by the switch Sw of the rectifier circuit 120 including the switch Sw.

[0074] E. Modifications In the above-described embodiments, the power receiving device 100 may include a filter circuit between the power receiving resonant circuit 110 and the adjustment circuit 140. More specifically, the power receiving device 100 may include an immittance filter, such as the filter circuit FL1 in FIG. 11 or the filter circuit FL2 in FIG. 12. The power receiving device 100 may include a band-pass filter in addition to the immittance filter. Note that although FIGS. 11 and 12 illustrate the power receiving device 100 of the first embodiment, the power receiving device 100x of the fourth embodiment may include the filter circuit FL1 or the filter circuit FL2.

[0075] By adopting such a configuration, the power receiving device 100 can achieve constant current characteristics of AC power and a function of suppressing harmonics.

[0076] F. Modification: In the above embodiment, the received power Pr is greatest when the power transmitting coil 222 and the power receiving coil 111 are directly opposed to each other. Furthermore, the received power Pr decreases as the distance from the directly opposed state increases. However, depending on the resonance method used by the power transmitting resonant circuit 220 and the power receiving resonant circuit 110, as shown in FIG. 13 , the received power Pr may increase as the distance from the directly opposed state increases. Specifically, this is the case when the power transmitting resonant circuit 220 and the power receiving resonant circuit 110 are configured by the power transmitting resonant circuit 220 in which the power transmitting coil 222 and the power transmitting resonant capacitor 221 are connected in series, and the power receiving resonant circuit 110 in which the power receiving coil 111 and the power receiving resonant capacitor 112 are connected in series. That is, this is the case when the power transmitting resonant circuit 220 is a series resonant circuit and the power receiving resonant circuit 110 is a series resonant circuit. In this case, the received power Pr is smallest when the power transmitting coil 222 and the power receiving coil 111 are directly opposed to each other. Furthermore, the received power Pr increases as the distance from the directly opposed state increases. As a result, the minimum target ratio Dm becomes the target ratio Dt at the position where the power transmitting coil 222 and the power receiving coil 111 are most distant relative to each other when they are opposed to each other. In the case of Figure 13 , by controlling the power receiving device 100 in the same manner as in the above embodiment, the power receiving device 100 of the present disclosure can efficiently supply power to the load device 130 while suppressing inrush power.

[0077] G. Modifications: (1) In the above embodiment, the power receiving device 100 is mounted on a vehicle. However, the power receiving device 100 may be mounted on another moving body. For example, the power receiving device 100 may be mounted on an airplane. (2) In the above embodiment, the power transmitting circuit may further include a rectifier circuit, a filter circuit, and the like. (3) In the above embodiment, the switch Sw constitutes all of the rectifier elements constituting the synchronous rectifier circuit 120. However, the switch Sw may constitute at least some of the rectifier elements constituting the synchronous rectifier circuit 120. For example, the switch Sw may constitute only the rectifier elements on the negative line Ln side. In this case, the rectifier elements on the positive line Lp side are constituted by rectifier diodes. (4) In the first embodiment, the power receiving sensor 160 is a current sensor that measures the current value of DC power. The power receiving sensor 160 may be another sensor. For example, the power receiving sensor 160 may be a voltage sensor that measures the voltage of DC power. Furthermore, the power receiving sensor 160 may be composed of multiple sensors. For example, the power receiving sensor 160 may be composed of a sensor that detects power reception using AC power and a sensor that detects power consumption by the load device 130 using DC power. (5) In the above embodiment, a battery is exemplified as the load device 130. However, the load device 130 is not limited to a battery. The load device 130 may be, for example, a lighting device or a power plant. When the load device 130 is a lighting device or a power plant, the load device 130 starts consuming DC power when the device is started. (6) In the above embodiment, the target power Pt is determined in advance based on the specifications of the load device 130. However, the target power Pt is not limited to the specifications of the load device 130 and may be determined in advance. For example, the target power Pt may be determined based on the rated power of the circuit of the power receiving device 100 or the power demand from the system power supply that supplies power to the power transmitting device 200. (7) In the above embodiment, the minimum target ratio Dm is exemplified as 0.5. However, the minimum target ratio Dm is not limited to 0.5. The minimum target ratio Dm may be 0.2, 0.7, or the like. (8) In the above embodiment, the control circuit 150 determines whether to start or stop the consumption of DC power by the load device 130 based on the current value acquired by the power receiving sensor 160.However, the control circuit 150 may determine the start and stop of DC power consumption by the load device 130 using other methods. For example, the control circuit 150 may be connected to a control device of the load device 130 and determine the start and stop of DC power consumption by the load device 130 based on commands received from the control device of the load device 130. (9) In the above embodiment, the reference current is, for example, set to a current value that is 20% of the current value of the target power Pt. However, the reference current may be a current value that is 10% or 40% of the current value of the target power Pt, or may be a reference value based on another current. (10) In the above embodiment, the control unit 151 is mainly configured, for example, by a microcomputer. That is, the control unit 151 is configured as a digital circuit. However, the control unit 151 may be configured as an analog circuit. (11) In the above embodiment, the adjustment unit 151a determines the power supply ratio D based on the current value. However, as described above, when the power receiving sensor 160 is a voltage sensor, the adjustment unit 151a may determine the power supply ratio D based on the voltage value. (12) In the above embodiment, the control circuit 150 performs control to increase the power supply ratio D to the target ratio Dt after the power receiving sensor 160 starts consuming DC power. However, the control circuit 150 does not have to increase the power supply ratio D in accordance with the target ratio Dt. More specifically, the control circuit 150 only needs to increase the power supply ratio D between the ratio Ds and the target ratio Dt. (13) In the above embodiment, the switch Sw of the synchronous rectifier circuit 120 is a MOSFET. However, the switch Sw of the synchronous rectifier circuit 120 may be another switching element. The switch Sw may be, for example, a BJT (Bipolar Junction Transistor) or an IGBT (Insulated Gate Bipolar Transistor). (14) In the above embodiment, the periods b and d are the short circuit mode periods, and the periods a and c are the power supply mode periods. However, the periods b and d may be the power supply mode periods, and the periods a and c may be the short circuit mode periods.

[0078] The present disclosure is not limited to the above-described embodiments and modifications, and can be realized in various configurations without departing from the spirit thereof. For example, the technical features in the embodiments and modifications corresponding to the technical features in each aspect described in the Summary of the Invention section can be appropriately replaced or combined to solve some or all of the above problems or achieve some or all of the above effects. Furthermore, if a technical feature is not described as essential in this specification, it can be deleted as appropriate.

[0079] H. Other Aspects: Features of the present disclosure include: (Mode 1) A power receiving device (100, 100x) that receives AC power contactlessly using a magnetic field, comprising: a resonant circuit (110) including a power receiving coil (111) that receives the AC power, the resonant circuit varying the magnitude of the AC power depending on a state of resonance or coupling; a rectifier circuit (120, 120x) that converts the AC power into DC power; a load device (130) that starts consuming the DC power based on a predetermined standard related to power; an adjustment circuit (140, 140x) including a switch (Sw) that shorts between input terminals (P1, P2) of the rectifier circuit, the adjustment circuit adjusting supply power (Pa) of the AC power to be supplied to the load device between the power receiving coil and the load device; a power receiving sensor (160) that detects reception of power using the DC power; and a control circuit (150, 150x) that controls the power receiving device, wherein the control circuit a short-circuit mode in which the terminals are short-circuited for a predetermined short-circuit period in each half cycle of one cycle (Ca) of the AC power, and a power supply mode in which the terminals are open for a power supply period of the half cycle excluding the short-circuit period, wherein the power receiving sensor controls a power supply rate (D), which is a rate of the power supply period in the half cycle, to be smaller than a minimum target rate (Dm), which is the minimum value of the target rate (Dt) according to the state of resonance or the coupling that can make the supplied power a predetermined target power (Pt), before the start of reception of the AC power, and wherein the power receiving sensor controls an increase of the power supply rate to be equal to or less than the target rate after consumption of the DC power starts. (Mode 2) The power receiving device according to mode 1, further comprising: a current sensor (160) for measuring a current value of the DC power, wherein the control circuit further comprises: an adjustment unit (151 a) for determining the power supply rate based on the current value, and a limiter (151 b) for limiting the power supply rate determined by the adjustment unit, the limiter relaxing the limit at a slower rate than a rate at which the adjustment unit determines the power supply rate. (Mode 3) The power receiving device according to mode 2, wherein the switch constitutes at least a part of a rectifying element constituting the rectifying circuit.(Mode 4) The power receiving device according to Mode 3, further comprising: the switch constitutes the entire rectifying element; and further comprising a parallel diode (Di) connected in parallel in a reverse direction relative to a forward direction of the switch; the rectifying circuit is a leg circuit (121, 122) in which two of the switches are connected in series, and the leg circuit includes a leg circuit connecting a positive line (Lp) and a negative line (Ln) of the DC power; the two switches are composed of a first switch (SwH) on the positive line side and a second switch (SwL) on the negative line side; and the control circuit, using the power receiving sensor, executes the short-circuit mode and the power supply mode by the second switch and the parallel diode connected in parallel to the first switch during a first time period including a time when power reception starts; A power receiving device in which, when the power receiving sensor detects a predetermined reference current in a second time period after the first time period, the second switch and the first switch execute the short-circuit mode and the power supply mode.

Claims

1. A power receiving device (100, 100x) that receives AC power in a non-contact manner by a magnetic field, comprising: a resonant circuit (110) including a power receiving coil (111) that receives the AC power, the resonant circuit having a magnitude of the AC power that varies depending on a state of resonance or coupling; a rectifier circuit (120, 120x) that converts the AC power into DC power; a load device (130) that consumes the DC power; an adjustment circuit (140, 140x) including a switch (Sw) that shorts between input terminals (P1, P2) of the rectifier circuit, the adjustment circuit adjusting a supply power (Pa) of the AC power to be supplied to the load device between the power receiving coil and the load device; a power receiving sensor (160) that detects the reception of the AC power or the DC power; and a control circuit (150, 150x) that controls the power receiving device, the control circuit comprising: a short circuit mode in which the terminals are short-circuited for a predetermined short circuit period for each half cycle of one cycle (Ca) of the AC power, and a power supply mode in which the terminals are opened for a power supply period of the half cycle excluding the short circuit period, wherein the power receiving sensor performs control to set a power supply ratio (D), which is a ratio of the power supply period in the half cycle, to a ratio smaller than a minimum target ratio (Dm), which is the minimum value of a target ratio (Dt) according to the coupling state that can make the supplied power a predetermined target power (Pt), before start of reception of the AC power, and wherein the power receiving sensor performs control to increase the power supply ratio to less than or equal to the target ratio after detecting the reception of the AC power.

2. A power receiving device as claimed in claim 1, further comprising a current sensor (160) for measuring a current value of the DC power, and the control circuit further comprising: an adjustment unit (151a) for determining the power supply ratio based on the current value; and a limiter (151b) for limiting the power supply ratio determined by the adjustment unit, the limiter relaxing the restriction at a slower rate than the rate at which the adjustment unit determines the power supply ratio.

3. A power receiving device according to claim 2, wherein the switch constitutes at least a part of a rectifying element constituting the rectifying circuit.

4. A power receiving device according to claim 1, further comprising: the switch constitutes all of the rectifying elements constituting the rectifying circuit; and further comprising a parallel diode (Di) connected in parallel in a reverse direction relative to the forward direction of the switch; the rectifying circuit comprises a leg circuit (121, 122) in which two of the switches are connected in series, the leg circuit connecting a positive line (Lp) and a negative line (Ln) of the DC power; the two switches comprise a first switch (SwH) on the positive line side and a second switch (SwL) on the negative line side; and the control circuit executes the short-circuit mode and the power supply mode by the second switch and the parallel diode connected in parallel to the first switch during a first time period including the start of power reception using the power receiving sensor; A power receiving device in which, when the power receiving sensor detects a predetermined reference current in a second time period after the first time period, the second switch and the first switch execute the short-circuit mode and the power supply mode.

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