Wireless power supply system and wireless power-receiving device

Abstract

In the present invention, a power-receiving device (10) is provided with a power-receiving resonant circuit (11), and also provided with a power-receiving rectifier circuit (12), a smoothing capacitor (13), and a control circuit (16). The power-receiving rectifier circuit (12) is electrically connected to the power-receiving resonant circuit (11), and rectifies alternating-current power received at a power-receiving coil (111) constituting the power-receiving resonant circuit (11). The smoothing capacitor (13) is electrically connected to the power-receiving rectifier circuit (12), and smooths, to a power-receiving direct-current voltage, the power rectified by the power-receiving rectifier circuit (12). The control circuit (16) is electrically connected to the power-receiving resonant circuit (11), and causes a state of electromagnetic resonance coupling to be changed by the rectification operation of the power-receiving rectifier circuit (12). The control circuit (16) controls execution and stopping of the rectification operation of the power-receiving rectifier circuit (12) so that a power-receiving voltage will reach a predetermined value on the basis of a control value that was set with respect to the power-receiving direct-current voltage. The control circuit (16) controls execution and stopping of the rectification operation of the power-receiving rectifier circuit (12) and causes the state of electromagnetic resonance coupling to be changed by adjusting the control value, and emits information from the power-receiving device (10) and executes information transmission to a power-transmitting device (91).

Description

Wireless power supply system and wireless power receiving device

[0001] The present invention relates to a wireless power receiving device and a wireless power supply system including the wireless power receiving device.

[0002] Patent Document 1 describes a power receiving device with a power interruption function. The power receiving device in Patent Document 1 includes a voltage detection circuit. The power receiving device performs rated rectification operation when the voltage detected by the voltage detection circuit is equal to or lower than a first threshold.

[0003] When the voltage detected by the voltage detection circuit reaches the second threshold (> the first threshold), the power receiving device stops the rated rectification operation, thereby stopping the power receiving operation.

[0004] Patent Literature 2 describes a wireless power supply system that transmits information between a wireless power receiving device and a wireless power transmitting device. A load circuit is connected to the wireless power receiving device.

[0005] The wireless power feeding system of Patent Document 2 uses a resonance modulation circuit in a wireless power receiver to control the input impedance seen from the wireless power transmitter to the load circuit side, thereby changing the electromagnetic field coupling between the wireless power transmitter and the wireless power receiver, and the wireless power transmitter detects the electrical variable resulting from this change to transmit information.

[0006] Patent No. 6677306 International Publication No. 2017 / 213032

[0007] However, in the power receiving device of the conventional wireless power supply system shown in Patent Documents 1 and 2, if both the receiving voltage control function and the information transmission function are to be realized, the circuit configuration becomes complicated and large. Furthermore, power loss occurs in the circuit that controls the receiving voltage, and power efficiency decreases.

[0008] Therefore, an object of the present invention is to realize a circuit that simultaneously realizes a receiving voltage control function and an information transmission function with a simple configuration, and to realize a wireless power receiving device that is highly power efficient and highly reliable.

[0009] The wireless power supply system of this invention comprises a power transmitting device having a power transmitting resonant circuit including a power transmitting coil, and a power receiving device having a power receiving resonant circuit including a power receiving coil, and supplies power by electromagnetic field resonant coupling between the power receiving resonant circuit and the electromagnetic field created by the power transmitting resonant circuit.

[0010] The power transmitting device includes a power transmitting resonant circuit, a power transmitting power conversion circuit, a power transmitting control circuit, and a power transmitting detection circuit.

[0011] The transmission power conversion circuit is electrically connected to the input DC power supply, converts DC power supplied from the input DC power supply into AC power through switching operations of a switching element, and passes AC current through the electrically connected transmission coil. The transmission control circuit controls the switching operations of the transmission power conversion circuit. The transmission detection circuit detects an electric variable that changes in response to changes in the state of electromagnetic resonance coupling.

[0012] The power receiving device includes a power receiving resonant circuit, as well as a power receiving rectifier circuit, a smoothing circuit, and a rectification control circuit. The power receiving rectifier circuit is electrically connected to the power receiving resonant circuit and rectifies AC power received by a power receiving coil that constitutes the power receiving resonant circuit. The smoothing circuit is electrically connected to the power receiving rectifier circuit and smoothes the power rectified by the power receiving rectifier circuit into a received DC voltage. The rectification control circuit is electrically connected to the power receiving resonant circuit and changes the state of electromagnetic resonance coupling through the rectification operation of the power receiving rectifier circuit.

[0013] The rectification control circuit controls the execution and stop of the rectification operation of the power receiving rectifier circuit based on a control value set for the power receiving DC voltage so that the power receiving voltage becomes a predetermined value. The rectification control circuit controls the execution and stop of the rectification operation of the power receiving rectifier circuit based on a pattern for adjusting the control value, changes the state of the electromagnetic resonance coupling, and transmits information from the power receiving device to the power transmitting device.

[0014] In this configuration, the wireless power receiving device can set a plurality of control values, and by adjusting the control values, it becomes possible to control the receiving voltage and transmit information.

[0015] According to the present invention, the wireless power receiving device of the wireless power supply system realizes a circuit that simultaneously realizes a receiving voltage control function and an information transmission function with a simple configuration, thereby achieving high power efficiency and high reliability.

[0016] FIG. 1 is a diagram showing an example of the configuration of a power receiving device of a wireless power supply system according to a first embodiment of the present invention. FIG. 2 is a diagram showing an example of the configuration of a power transmitting device of a wireless power supply system according to the first embodiment of the present invention. FIGS. 3A and 3B are circuit diagrams of a control circuit according to the first embodiment. FIG. 4 is a table showing various states of power reception control and information transmission control. FIG. 5 is a diagram showing an example of data and waveforms used for information transmission. FIGS. 6A, 6B, 6C, and 6D are diagrams showing examples of various waveforms in voltage control and information transmission control according to the first embodiment. FIG. 7 is a diagram showing an example of the configuration of a power receiving device of a wireless power supply system according to a second embodiment of the present invention. FIGS. 8A and 8B are circuit diagrams of a control circuit according to the second embodiment. FIG. 9 is a diagram showing an example of the configuration of a power receiving device of a wireless power supply system according to a third embodiment of the present invention. FIGS. 10A and 10B are circuit diagrams of a control circuit according to the third embodiment. FIG. 11 is a diagram showing an example of the configuration of a power receiving device of a wireless power supply system according to a fourth embodiment of the present invention. Fig. 12 is a diagram showing an example of the configuration of a power receiving device in a wireless power feeding system according to a fifth embodiment of the present invention. Fig. 13 is a diagram showing another example of a power transmitting device.

[0017] [First Embodiment] A wireless power supply system according to a first embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a diagram showing an example of the configuration of a power receiving device of the wireless power supply system according to the first embodiment of the present invention. Fig. 2 is a diagram showing an example of the configuration of a power transmitting device of the wireless power supply system according to the first embodiment of the present invention.

[0018] 1, the power receiving device 10 includes a power receiving resonant circuit 11, a power receiving rectifier circuit 12, a smoothing capacitor 13, a voltage conversion circuit 14, a charging circuit 15, a control circuit 16, a battery BAT, a HI-side output terminal POH, and a LOW-side output terminal POL. The power receiving device 10 corresponds to a "wireless power receiving device," and the control circuit 16 corresponds to a "rectification control circuit."

[0019] The power receiving resonant circuit 11 includes a power receiving coil 111 and a resonant capacitor 112. The resonant capacitor 112 and the power receiving coil 111 are connected in parallel. As a result, the power receiving resonant circuit 11 forms a parallel resonant circuit of the power receiving coil 111 and the resonant capacitor 112. The resonant frequency of the power receiving resonant circuit 11 is approximately the same as the frequency of the external alternating magnetic field to which the power receiving coil 111 is coupled, and is also approximately the same as the drive frequency (switching frequency) of the power transmitting device 91.

[0020] The power receiving rectifier circuit 12 includes a diode D11, a diode D12, a diode D21, and a diode D22, and forms a full-wave rectifier circuit. The diodes D11 and D12 are connected in series, and the diode D12 is connected to a reference potential. The diodes D21 and D22 are connected in series, and the diode D22 is connected to the reference potential.

[0021] A node between the anode of the diode D11 and the cathode of the diode D12 is connected to one output terminal of the power receiving resonant circuit 11, and a node between the anode of the diode D21 and the cathode of the diode D22 is connected to the other output terminal of the power receiving resonant circuit 11. A node between the cathode of the diode D11 and the cathode of the diode D21 is connected to the HI side output terminal of the power receiving rectifier circuit 12. A node between the anode of the diode D12 and the anode of the diode D22 is connected to the LOW side output terminal of the power receiving rectifier circuit 12.

[0022] A switching element Q1 is connected in parallel to the diode D12. A switching element Q2 is connected in parallel to the diode D22. The switching elements Q1 and Q2 are switching elements using power semiconductors, and are configured by, for example, FETs. The switching elements Q1 and Q2 are power receiving rectification control elements.

[0023] A smoothing capacitor 13 is connected between the HI side output terminal and the LOW side output terminal of the power receiving rectifier circuit 12. The smoothing capacitor 13 corresponds to a "smoothing circuit."

[0024] The voltage across the smoothing capacitor 13 is the receiving voltage Vrec of the power receiving device 10. The receiving voltage Vrec, which will be described in detail later, is a substantially DC voltage that fluctuates within a predetermined voltage range and corresponds to a "receiving DC voltage."

[0025] The HI output terminal of the power receiving rectifier circuit 12 is connected to the input terminal of the voltage conversion circuit 14. The voltage conversion circuit 14 is connected to a reference potential. The voltage conversion circuit 14 is configured, for example, as a series regulator (linear regulator) or a DC-DC converter. The output terminal of the voltage conversion circuit 14 is connected to the input terminal of the charging circuit 15. The voltage conversion circuit 14 is configured as needed. In other words, the voltage conversion circuit 14 can be omitted. In this case, the HI output terminal of the power receiving rectifier circuit 12 is directly connected to the charging circuit 15.

[0026] A battery BAT is connected between the HI output terminal (terminal for charging voltage Vch) and the LOW output terminal (terminal connected to a reference potential) of the charging circuit 15. The battery BAT is a secondary battery that can be charged and discharged. The HI output terminal of the charging circuit 15 is connected to the HI output terminal POH of the power receiving device 10. The LOW output terminal of the charging circuit 15 is connected to the LOW output terminal POL of the power receiving device 10.

[0027] The control circuit 16 includes an MCU 61, a resistance element 621, a resistance element 622, a switch circuit 630, a reference voltage 631, a reference voltage 632, and a comparator 64. The reference voltages 631 and 632 are set as DC voltages.

[0028] The MCU 61 and the comparator 64 are connected to the node between the output terminal of the voltage conversion circuit 14 and the input terminal of the charging circuit 15, and are connected to the reference potential. As a result, a drive voltage is applied to the MCU 61 and the comparator 64.

[0029] A signal input terminal of the MCU 61 is connected to the charging circuit 15. A control signal output terminal of the MCU 61 is connected to the switch circuit 630.

[0030] The switch circuit 630 has a common terminal, a first selection terminal, and a second selection terminal. The switch circuit 630 selects either the first selection terminal or the second selection terminal and connects it to the common terminal in response to a control signal from the MCU 61. The common terminal of the switch circuit 630 is connected to the inverting input terminal of the comparator 64.

[0031] The reference voltage 631 is connected between the first selection terminal of the switch circuit 630 and the reference potential. In this case, the positive electrode of the reference voltage 631 is connected to the first selection terminal, and the negative electrode is connected to the reference potential.

[0032] The reference voltage 632 is connected between the second selection terminal of the switch circuit 630 and the reference potential. In this case, the positive electrode of the reference voltage 632 is connected to the second selection terminal, and the negative electrode is connected to the reference potential.

[0033] The resistor element 621 and the resistor element 622 are connected in series. The resistor element 621 is connected to the terminal on the HI potential side of the smoothing capacitor 13 (the input terminal of the voltage conversion circuit 14). The resistor element 622 is connected to the reference potential. The node between the resistor elements 621 and 622 is connected to the non-inverting input terminal of the comparator 64.

[0034] The output terminal of the comparator 64 is connected to the gate terminal of the switching element Q1 and the gate terminal of the switching element Q2.

[0035] 2, the power transmitting device 91 includes a DC power supply 911, an input capacitor 912, a power transmitting switching control circuit 913, a power transmitting power conversion circuit 914, a power transmitting resonant circuit 915, a resistive element 916, and a differential amplifier circuit 917. The resistive element 916 and the differential amplifier circuit 917 form a "power transmitting detection circuit."

[0036] The input capacitor 912 is connected in parallel to the DC power supply 911. A drain terminal of a switching element QH in the transmission power conversion circuit 914 is connected to the positive electrode of the DC power supply 911 and a node of the input capacitor 912 via a resistor element 916. A drain terminal of a switching element QL is connected to the source terminal of the switching element QH. A source terminal of the switching element QL is connected to the negative electrode of the DC power supply 911 and a node of the input capacitor 912. The node of the negative electrode of the DC power supply 911 and the input capacitor 912 is connected to a reference potential.

[0037] A terminal of the resistor element 916 on the DC power supply 911 side is connected to a non-inverting input terminal of a differential amplifier circuit 917. A terminal of the resistor element 916 on the transmission power conversion circuit 914 side is connected to an inverting input terminal of the differential amplifier circuit 917. An output terminal of the differential amplifier circuit 917 is connected to the power transmission switching control circuit 913.

[0038] The power transmission switching control circuit 913 is connected to the gate terminal of the switching element QH and the gate terminal of the switching element QL.

[0039] The power transmitting resonant circuit 915 includes a power transmitting coil 9151 and a resonant capacitor 9152. One end of the power transmitting resonant circuit 915 is connected to the node between the switching element QH and the switching element QL. The other end of the power transmitting resonant circuit 915 is connected to the source terminal of the switching element QL.

[0040] The resonance capacitor 9152 is connected in series to the power transmitting coil 9151. As a result, the power transmitting resonance circuit 915 forms a series resonance circuit of the power transmitting coil 9151 and the resonance capacitor 9152. The resonance frequency of the power transmitting resonance circuit 915 is approximately the same as the switching frequency of the power transmitting power conversion circuit 914.

[0041] (Power Supply Control) The power transmission switching control circuit 913 is connected to the DC power supply 911 and is driven by receiving power supply from the DC power supply 911. The power transmission switching control circuit 913 may receive power supply via an LDO or the like.

[0042] When the power transmission switching control circuit 913 determines that steady power supply is to be performed, it generates a switching drive signal of a predetermined frequency and outputs it to the switching elements QH and QL, thereby causing the power transmission switching control circuit 913 to perform switching control (on / off control) of the switching elements QH and QL at a predetermined frequency (switching frequency).

[0043] The transmission power conversion circuit 914 converts the DC power supplied from the DC power supply 911 into AC power of a frequency corresponding to the switching frequency by the switching operation (on / off switching operation) of the switching element QH and the switching element QL, and outputs the AC current to the transmission resonant circuit 915.

[0044] The power transmitting resonant circuit 915 resonates at the frequency of this AC current, and the power transmitting coil 9151 generates an alternating magnetic field due to this AC current.

[0045] When the power receiving device 10 is placed relative to the power transmitting device 91 for charging, the power receiving coil 111 is electromagnetically coupled to the power transmitting coil 9151. The power receiving coil 111 generates an AC current according to the degree of coupling with the alternating magnetic field and outputs it to the power receiving rectifier circuit 12.

[0046] In this case, the resonant frequency of the power receiving resonant circuit 11 is substantially the same as the frequency of the alternating magnetic field, i.e., the resonant frequency of the power transmitting resonant circuit 915, so that the power receiving resonant circuit 11 and the power transmitting resonant circuit 915 are electromagnetically resonantly coupled. This achieves low-loss wireless power feeding from the power transmitting device 91 to the power receiving device 10. Note that the frequency of the alternating magnetic field for this wireless power feeding is preferably in the 6.78 MHz band or the 13.56 MHz band.

[0047] The power receiving rectifier circuit 12 rectifies the input AC current and outputs the rectified current. That is, the power receiving rectifier circuit 12 rectifies the AC power received by the power receiving resonant circuit 11 and outputs the rectified current.

[0048] The smoothing capacitor 13 smoothes the rectified current and the rectified voltage, and outputs a DC receiving voltage Vrec to the voltage conversion circuit 14 .

[0049] The voltage conversion circuit 14, for example, steps down the DC receiving voltage Vrec. As a result, the voltage conversion circuit 14 converts the DC receiving voltage Vrec into a DC charging voltage Vch. The voltage conversion circuit 14 outputs the charging voltage Vch to the charging circuit 15. The charging voltage Vch is also supplied as a drive voltage for the MCU 61 and the comparator 64 of the control circuit 16.

[0050] The charging circuit 15 generates a charging current for the battery BAT from the input charging voltage Vch, and charges the battery BAT.

[0051] When an electronic load is connected to the HI-side output terminal POH and the LOW-side output terminal POL, the battery BAT supplies power through the HI-side output terminal POH and the LOW-side output terminal POL. If the power receiving device 10 is connected to the power transmitting device 91 and is supplying power, the output voltage and output current of the charging circuit 15 can be output to the electronic load through the HI-side output terminal POH and the LOW-side output terminal POL.

[0052] (Power receiving voltage control and information transmission) Figures 3(A) and 3(B) are circuit diagrams of a control circuit according to the first embodiment. Figures 3(A) and 3(B) differ in the selection state of multiple reference voltages. Figure 4 is a table showing various states of power receiving control and information transmission control. Figure 5 is a diagram showing an example of data and waveforms used for information transmission.

[0053] 6(A), 6(B), 6(C), and 6(D) are diagrams showing examples of various waveforms in voltage control and information transmission control according to the first embodiment. Fig. 6(A) shows the waveform of the receiving voltage Vrec, Fig. 6(B) shows the waveform of the reference voltage, Fig. 6(C) shows the waveform of the gate voltages of the switching elements Q1 and Q2 of the receiving rectifier circuit 12, and Fig. 6(D) shows the waveform of the transmitting current.

[0054] (Setting of Reference Voltages 631 and 632) The reference voltage 631 is a DC reference voltage capable of outputting a first DC reference voltage Vref1. The reference voltage 632 is a DC reference voltage capable of outputting a second DC reference voltage Vref2. The reference voltages 631 and 632 are configured by shunt regulators or the like. For example, the reference voltages 631 and 632 are generated by converting the receiving voltage Vrec. Note that the reference voltages 631 and 632 can also be generated from a primary battery or the like.

[0055] The first reference voltage Vref1 is set to a voltage value for controlling the receiving voltage Vrec in the above-described normal power supply control (power receiving control) to a substantially constant first receiving voltage Vrec1 (e.g., 5.5 V). In other words, the first reference voltage Vref1 is a voltage value for voltage control and voltage cut-off control in the normal power supply control (power receiving control).

[0056] The second reference voltage Vref2 is set to a voltage value higher than the first reference voltage Vref1. The second reference voltage Vref2 is set to a voltage value that enables information transmission while performing the above-described power supply control. The second reference voltage Vref2 is also used to control the receiving voltage Vrec to a substantially constant second receiving voltage Vrec2 (e.g., 6.0 V).

[0057] The first reference voltage Vref1 and the second reference voltage Vref2 correspond to the "control value."

[0058] (Outline of power receiving rectification control and power receiving cutoff control) A power receiving voltage Vrec is applied to a voltage dividing circuit formed by a series circuit of resistor elements 621 and 622 in the control circuit 16. The divided voltage of this voltage dividing circuit (the voltage at the node between resistor elements 621 and 622) is the detection voltage Vcp. The detection voltage Vcp is input to the non-inverting input terminal of the comparator 64.

[0059] The inverting input terminal of the comparator 64 selectively receives the first reference voltage Vref1 or the second reference voltage Vref2.

[0060] The comparator 64 compares the selected reference voltage from the first reference voltage Vref1 or the second reference voltage Vref2 with the detected voltage Vcp, generates a HIGH or LOW level rectification control signal, and outputs it to the switching elements Q1 and Q2 of the power receiving rectification circuit 12.

[0061] The switching elements Q1 and Q2 of the power receiving rectifier circuit 12 are controlled to an on state (short-circuited state) or an off state (open state) by a rectification control signal, which changes the circuit configuration of the power receiving rectifier circuit 12 and switches between power receiving rectification and power receiving cutoff.

[0062] Specifically, when the switching elements Q1 and Q2 are controlled to be in the off state, the power receiving rectifier circuit 12 forms a full-wave rectifier circuit using four diodes D11, D12, D21, and D22, thereby allowing the power receiving rectifier circuit 12 to perform power rectification.

[0063] On the other hand, when the switching elements Q1 and Q2 are controlled to be in the on state, the power receiving rectifier circuit 12 does not constitute a full-wave rectifier circuit, and as a result, the power receiving rectifier circuit 12 stops rectifying the power receiving and cuts off the power receiving.

[0064] The rectification of received power and the interruption of received power are performed both when the first reference voltage Vref1 is applied and when the second reference voltage Vref2 is applied.

[0065] (Control based on first reference voltage Vref1: Figures 3(A), upper table of Figure 4, Figures 6(A), 6(B), and 6(C)) When MCU 61 receives power but does not transmit information, or when MCU 61 transmits DATA[0] during information transmission, MCU 61 controls switch circuit 630 to electrically connect the inverting input terminal of comparator 64 to reference voltage 631. As a result, first reference voltage Vref1 is input to the inverting input terminal of comparator 64. Note that MCU 61 makes decisions such as not transmitting information or transmitting DATA[0] during information transmission based on, for example, the charging state detected by charging circuit 15.

[0066] The comparator 64 compares the detected voltage Vcp with the first reference voltage Vref1, generates a HIGH or LOW level rectification control signal, and outputs it to the switching elements Q1 and Q2 of the power receiving rectification circuit 12.

[0067] More specifically, if the detected voltage Vcp is lower than the first reference voltage Vref1 (ST1 in FIG. 4), the comparator 64 generates a LOW-level rectification control signal and outputs it to the switching elements Q1 and Q2 of the power receiving rectification circuit 12.

[0068] When a LOW-level rectification control signal is input, the switching elements Q1 and Q2 of the power receiving rectifier circuit 12 are controlled to the OFF state (open state), so that the power receiving rectifier circuit 12 forms a full-wave rectifier circuit using four diodes D11, D12, D21, and D22, and performs power receiving rectification based on the first reference voltage Vref1.

[0069] On the other hand, if the detected voltage Vcp is higher than the first reference voltage Vref1 (ST2 in FIG. 4), the comparator 64 generates a HI level rectification control signal and outputs it to the switching elements Q1 and Q2 of the power receiving rectification circuit 12.

[0070] When a high-level rectification control signal is input, the switching elements Q1 and Q2 of the power receiving rectifier circuit 12 are controlled to the on state (short-circuit state). As a result, the power receiving rectifier circuit 12 does not form a full-wave rectifier circuit with the four diodes D11, D12, D21, and D22. As a result, the power receiving rectifier circuit 12 stops receiving power rectification and cuts off the power receiving.

[0071] By repeating this power receiving rectification and power receiving cutoff, as shown in Figure 6 (A), the power receiving device 10 can continue receiving power at a substantially DC first power receiving voltage Vrec1 with a voltage fluctuation range ΔVcon. In this case, switching between power receiving rectification and power receiving cutoff can be achieved quickly by using an analog circuit with a voltage divider circuit using resistive elements and a comparator. Therefore, the voltage fluctuation range ΔVcon can be reduced, and the first power receiving voltage Vrec1 becomes a substantially stable DC voltage.

[0072] (Control based on second reference voltage Vref2: Figure 3(B), lower table of Figure 4, Figures 6(A), 6(B), and 6(C)) When transmitting DATA[1] during information transmission, the MCU 61 controls the switch circuit 630 to electrically connect the inverting input terminal of the comparator 64 to the reference voltage 632. As a result, the second reference voltage Vref2 is input to the inverting input terminal of the comparator 64. Note that the MCU 61 makes decisions such as transmitting DATA[1] during information transmission based on, for example, the state of charge detected by the charging circuit 15.

[0073] The comparator 64 compares the detected voltage Vcp with the second reference voltage Vref2, generates a HIGH or LOW level rectification control signal, and outputs it to the switching elements Q1 and Q2 of the power receiving rectification circuit 12.

[0074] More specifically, if the detected voltage Vcp is lower than the second reference voltage Vref2 (ST3 in FIG. 4), the comparator 64 generates a LOW-level rectification control signal and outputs it to the switching elements Q1 and Q2 of the power receiving rectification circuit 12.

[0075] When a LOW-level rectification control signal is input, the switching elements Q1 and Q2 of the power receiving rectifier circuit 12 are controlled to the OFF state (open state), so that the power receiving rectifier circuit 12 forms a full-wave rectifier circuit using four diodes D11, D12, D21, and D22, and performs power receiving rectification based on the second reference voltage Vref2.

[0076] On the other hand, if the detected voltage Vcp is higher than the second reference voltage Vref2 (ST4 in FIG. 4), the comparator 64 generates a HIGH level rectification control signal and outputs it to the switching elements Q1 and Q2 of the power receiving rectification circuit 12.

[0077] When a high-level rectification control signal is input, the switching elements Q1 and Q2 of the power receiving rectifier circuit 12 are controlled to the on state (short-circuit state). As a result, the power receiving rectifier circuit 12 does not form a full-wave rectifier circuit with the four diodes D11, D12, D21, and D22. As a result, the power receiving rectifier circuit 12 stops receiving power rectification and cuts off the power receiving.

[0078] By repeating this rectification and interruption of power reception, the power receiving device 10 can receive power at a substantially DC second power receiving voltage Vrec2 having a voltage fluctuation width ΔVcon, as shown in FIG. 6A.

[0079] In this case, switching between receiving rectification and receiving cutoff can be performed quickly by using a voltage divider circuit with resistive elements and an analog circuit with a comparator, so the voltage fluctuation range ΔVcon can be reduced and the second receiving voltage Vrec2 becomes a substantially stable DC voltage.

[0080] The above description shows a case where the receiving voltage does not change suddenly or significantly. However, the above-described power receiving cutoff is also performed when an undesired, sudden, large current (excessive current) is input to the power receiving resonant circuit 11. This allows the power receiving device 10 to maintain a stable DC voltage (first receiving voltage Vrec1 or second receiving voltage Vrec2) even when an undesired, sudden, large receiving current is input.

[0081] (Information Transmission to Power Transmission Device 91: FIGS. 5, 6B, 6C, and 6D) When the MCU 61 determines that it is necessary to transmit information DATA[1] to the power transmission device 91, it switches from the selection state of the first reference voltage Vref1 to the selection state of the second reference voltage Vref2. The MCU 61 maintains the second reference voltage Vref2 for a predetermined second reference voltage selection time Tit, and switches from the selection state of the second reference voltage Vref2 to the selection state of the first reference voltage Vref1.

[0082] In this case, as shown in Figures 5 and 6 (B), the second reference voltage selection time Tit is set to be shorter than the data detection period Tdet used for transmitting information from the power receiving device 10 to the power transmitting device 91 in a wireless power supply system including the power receiving device 10 and the power transmitting device 91.

[0083] Here, the second reference voltage Vref2 is set relative to the first reference voltage Vref1 so that the potential difference ΔVit between the first receiving voltage Vrec1 (voltage based on the first reference voltage Vref1) and the second receiving voltage Vrec2 (voltage based on the second reference voltage Vref2) is greater than the voltage fluctuation range ΔVcon of the first receiving voltage Vrec1 and the second receiving voltage Vrec2.

[0084] Therefore, when the first reference voltage Vref1 is switched to the second reference voltage Vref2, the detection voltage Vcp becomes lower than the second reference voltage Vref2 at this timing, so the comparator 64 outputs a LOW-level rectified power signal to the switching elements Q1 and Q2.

[0085] In this way, the control circuit 16 controls the level (voltage) of the rectified power signal output to the switching elements Q1 and Q2. The control circuit 16 sets a control pattern for the switching elements Q1 and Q2 by changing and adjusting the control value over time. Based on this control pattern, the control circuit 16 adjusts the level (control value) of the rectified power signal to control the on / off of the switching elements Q1 and Q2.

[0086] When a low-level power receiving control signal is input, the switching elements Q1 and Q2 function as switch elements that determine whether to perform or stop rectification at a switching frequency (the frequency of an alternating magnetic field). By performing or stopping the rectification, the impedance at the switching frequency (the frequency of an alternating magnetic field) when viewed from the power transmitting resonant circuit 915 of the power transmitting device 91 toward the power receiving resonant circuit 11 of the power receiving device 10 changes.

[0087] This changes the resonant state between the power transmitting resonant circuit 915 and the power receiving resonant circuit 11, and as shown in Figures 5 and 6 (D), the amplitude of the power transmitting current itx flowing through the power transmitting resonant circuit 915 and the power transmitting coil current itxL flowing through the power transmitting coil 9151 changes significantly. The amplitude may become smaller or larger depending on the constant settings of the resonance parameters.

[0088] When the amplitude of the transmission current itx changes significantly, the voltage across the resistor element 916 of the power transmission device 91 also changes significantly. This changing voltage across the resistor element 916 corresponds to an "electrical variable." The electrical variable is not limited to voltage, but may also be current. This causes a large change in the potential difference between the non-inverting input terminal and the inverting input terminal of the differential amplifier circuit 917, and the waveform (amplitude) of the output signal from the differential amplifier circuit 917 changes.

[0089] The power transmission switching control circuit 913 can detect DATA[1] from the power receiving device 10 by detecting a change in the waveform (amplitude) of the output signal of the differential amplifier circuit 917 .

[0090] In this way, with the above-described configuration, the wireless power supply system can realize the information transmission of DATA[1] from the power receiving device 10 to the power transmitting device 91.

[0091] Furthermore, as shown in Figures 5 and 6 (D), the wireless power supply system is able to realize information transmission of DATA[0] from the power receiving device 10 to the power transmitting device 91 by not being able to detect a change in the waveform (amplitude) of the output signal of the differential amplifier circuit 917 during the data detection period Tdet.

[0092] As described above, the wireless power supply system including the power transmitting device 91 and the power receiving device 10 can realize information transmission from the power receiving device 10 to the power transmitting device 91 .

[0093] The wireless power supply system can realize information transmission while performing the above-described power receiving voltage control and power receiving cutoff control.

[0094] Furthermore, in the above-described configuration, the second reference voltage Vref2 is set so that (potential difference ΔVit between the first power receiving voltage Vrec1 and the second power receiving voltage Vrec2)>(voltage fluctuation range ΔVcon) (for example, approximately two to three times in the case of FIG. 6 ). This allows the wireless power supply system to prevent the detection voltage Vcp due to power receiving control from becoming undesirably larger than the second reference voltage Vref2 when switching from the first reference voltage Vref1 to the second reference voltage Vref2. Similarly, the wireless power supply system can prevent the detection voltage Vcp due to power receiving control from becoming undesirably smaller than the first reference voltage Vref1 when switching from the second reference voltage Vref2 to the first reference voltage Vref1. This allows the wireless power supply system to prevent malfunctions in information transmission.

[0095] The voltage fluctuation width ΔVcon can be set (adjusted) by the capacitance of the smoothing capacitor 13 and the delay time from voltage detection by the control circuit 16 to switch control.

[0096] Furthermore, in the above-described configuration, the second reference voltage selection time Tit is set to be a predetermined multiple longer than the switching period Tc in the power receiving voltage control (for example, approximately 10 times longer in the case of FIG. 6 ). This allows the power receiving device 10 to maintain the time for changing the impedance for transmitting the information DATA[1] at a level that can be detected by the power transmitting device 91. Therefore, the wireless power supply system can more reliably transmit DATA[1] from the power receiving device 10 to the power transmitting device 91.

[0097] Furthermore, in the above-described configuration, the second reference voltage selection time Tit is shorter than the data detection cycle Tdet for information transmission by a predetermined amount (for example, approximately ⅓ in the case of FIG. 6 ). This allows the wireless power supply system to shorten the time during which the receiving voltage Vrec becomes unnecessarily high as much as possible while still allowing information transmission. Therefore, the wireless power supply system can achieve highly efficient power reception (power supply).

[0098] Furthermore, the above-described configuration uses the detection voltage Vcp, which is a divided voltage of the power receiving voltage Vrec. Here, for example, the resistance value of the resistor element 622 connected to the reference potential is set smaller than the resistance value of the resistor element 621. This allows the detection voltage Vcp to be lowered. Therefore, the first reference voltage Vref1 and the second reference voltage Vref2 can be lowered. This allows, for example, the reference voltages 631 and 632 to be smaller, and the power receiving device 10 to be smaller.

[0099] Furthermore, in the above-described configuration, the receiving voltage Vrec rises when the second reference voltage Vref2 is selected. This energy is stored in the smoothing capacitor 13, and when the voltage returns to the first reference voltage Vref1, it is supplied to the load (the circuit downstream of the smoothing capacitor 13). This allows the power receiving device 10 to reduce power loss due to information transmission and reduce heat generation.

[0100] Furthermore, in conventional configurations, the receiving voltage may drop due to load modulation during information transmission or temporary suspension of power reception, but the receiving device 10 having the above-described configuration does not drop (increases) the receiving voltage Vrec during information transmission, enabling more stable operation.

[0101] [Second Embodiment] A wireless power supply system according to a second embodiment of the present invention will be described with reference to the drawings. Fig. 7 is a diagram showing an example of the configuration of a power receiving device of the wireless power supply system according to the second embodiment of the present invention. Figs. 8(A) and 8(B) are circuit diagrams of a control circuit according to the second embodiment.

[0102] 7, 8A, and 8B, the wireless power supply system according to the second embodiment differs from the wireless power supply system according to the first embodiment in the configuration of the power receiving device 10A. Below, only the differences between the power receiving device 10A and the power receiving device 10 according to the first embodiment will be described, and descriptions of similar parts will be omitted.

[0103] The power receiving device 10A includes a control circuit 16A. Schematically, the control circuit 16A differs from the control circuit 10A in that it does not use a reference voltage for the control circuit 16A but uses a voltage dividing circuit using resistive elements.

[0104] The control circuit 16A includes an MCU 61 , a resistance element 621 , a resistance element 622 , a resistance element 651 , a resistance element 652 , a resistance element 653 , and a switch circuit 650 .

[0105] The MCU 61 and the comparator 64 are connected to the node between the output terminal of the voltage conversion circuit 14 and the input terminal of the charging circuit 15, and are connected to the reference potential.

[0106] The resistor element 621 and the resistor element 622 are connected in series. The resistor element 621 is connected to the terminal on the HI potential side of the smoothing capacitor 13 (the input terminal of the voltage conversion circuit 14). The resistor element 622 is connected to the reference potential. The node between the resistor elements 621 and 622 is connected to the non-inverting input terminal of the comparator 64.

[0107] Resistance element 651 and resistance element 652 are connected in series. Resistance element 651 is connected to a node between the output terminal of voltage conversion circuit 14 and the input terminal of charging circuit 15. Resistance element 652 is connected to a reference potential. The node between resistance elements 651 and 652 is connected to the inverting input terminal of comparator 64.

[0108] The resistor element 653 and the switch circuit 650 are connected in series. The series circuit of the resistor element 653 and the switch circuit 650 is connected in parallel to the resistor element 651.

[0109] When performing control using the first reference voltage Vref1A, the MCU 61 controls, for example, the switch circuit 650 to the off state (open state), so that the first reference voltage Vref1A becomes a divided voltage by the voltage divider circuit made up of the resistance elements 651 and 652.

[0110] When performing control using the second reference voltage Vref2A (>Vref1A), the MCU 61 controls, for example, the switch circuit 650 to the on state (short-circuit state), so that the second reference voltage Vref2A becomes a divided voltage obtained by a voltage divider circuit made up of the parallel circuit of the resistance elements 651 and 653 and the resistance element 652.

[0111] With this configuration, the control circuit 16A can adjust the input voltage of the inverting input terminal of the comparator 64 to two values. Therefore, the power receiving device 10A and the wireless power feeding system including the power receiving device 10A can achieve the same effects as the power receiving device 10 and the wireless power feeding system including the power receiving device 10.

[0112] Furthermore, the power receiving device 10A does not need to include the reference voltages 631 and 632, which simplifies the circuit configuration and allows for miniaturization.

[0113] [Third Embodiment] A wireless power supply system according to a third embodiment of the present invention will be described with reference to the drawings. Fig. 9 is a diagram showing an example of the configuration of a power receiving device of the wireless power supply system according to the third embodiment of the present invention. Figs. 10(A) and 10(B) are circuit diagrams of a control circuit according to the third embodiment.

[0114] 9, 10A, and 10B, the wireless power supply system according to the third embodiment differs from the wireless power supply system according to the first embodiment in the configuration of the power receiving device 10B. In the following, only the differences between the power receiving device 10B and the power receiving device 10 according to the first embodiment will be described, and a description of the similarities will be omitted.

[0115] The power receiving device 10B includes a control circuit 16B. Generally, the control circuit 16B differs from the control circuit 16 in that the control circuit 16B switches the voltage division ratio for the received voltage without changing the reference voltage in order to achieve information transmission.

[0116] The control circuit 16B includes an MCU 61 , a resistance element 621 , a resistance element 622 , a resistance element 623 , a switch circuit 620 , and a reference voltage 640 .

[0117] The MCU 61 and the comparator 64 are connected to the node between the output terminal of the voltage conversion circuit 14 and the input terminal of the charging circuit 15, and are connected to the reference potential.

[0118] The reference voltage 640 is connected between the inverting input terminal of the comparator 64 and a reference potential.

[0119] The resistor element 621 and the resistor element 622 are connected in series. The resistor element 621 is connected to the terminal on the HI potential side of the smoothing capacitor 13 (the input terminal of the voltage conversion circuit 14). The resistor element 622 is connected to the reference potential. The node between the resistor elements 621 and 622 is connected to the non-inverting input terminal of the comparator 64.

[0120] The resistor element 623 and the switch circuit 620 are connected in series. The series circuit of the resistor element 623 and the switch circuit 620 is connected in parallel to the resistor element 622.

[0121] When performing control using the first detection voltage Vcp1, the MCU 61 controls, for example, the switch circuit 620 to the off state (open state), so that the first detection voltage Vcp1 becomes a divided voltage by the voltage divider circuit made up of the resistance elements 622 and 621.

[0122] When performing control using the second detection voltage Vcp2 (>Vcp1), the MCU 61 controls, for example, the switch circuit 620 to the on state (short-circuit state), so that the second detection voltage Vcp2 becomes a divided voltage obtained by a voltage divider circuit made up of the parallel circuit of the resistance elements 622 and 623 and the resistance element 621.

[0123] By performing this control, even if the receiving voltage Vrec is the same, the first detection voltage Vcp1 becomes higher than the second detection voltage Vcp2. This causes a difference between the first detection voltage Vcp1 and the second detection voltage Vcp2 relative to the reference voltage Vref. Therefore, the control circuit 16B can perform the same control as the control circuit 16.

[0124] With this configuration, the control circuit 16B can adjust the input voltage to two values ​​at the inverting input terminal of the comparator 64. Therefore, the power receiving device 10B and the wireless power feeding system including the power receiving device 10B can achieve the same effects as the power receiving device 10 and the wireless power feeding system including the power receiving device 10.

[0125] [Fourth embodiment] A wireless power supply system according to a fourth embodiment of the present invention will be described with reference to the drawings. Fig. 11 is a diagram showing an example of the configuration of a power receiving device of the wireless power supply system according to the fourth embodiment of the present invention.

[0126] 11 , the wireless power supply system according to the fourth embodiment differs from the wireless power supply system according to the first embodiment in the configuration of a power receiving device 10C and in the inclusion of a load adjustment circuit 70. In the following, only the differences between the power receiving device 10C and the power receiving device 10 according to the first embodiment will be described, and descriptions of similar parts will be omitted.

[0127] The power receiving device 10C includes a control circuit 16C and a load adjusting circuit 70. The control circuit 16C differs from the control circuit 16 in that an MCU 61 controls the switching of a switch circuit 630 and also controls the switching of the load adjusting circuit 70.

[0128] The load adjustment circuit 70 includes a resistor element 71 and a switch circuit 72. The resistor element 71 and the switch circuit 72 are connected in series. The load adjustment circuit 70 (the series circuit of the resistor element 71 and the switch circuit 72) is connected in parallel to the smoothing capacitor 13. In other words, the load adjustment circuit 70 is connected between both output terminals of the power receiving rectifier circuit 12.

[0129] When only receiving power without transmitting DATA[1], the MCU 61 controls the switch circuit 72 to the off state (open state), thereby suppressing power loss due to the resistance element 71 when the power receiving device 10C receives power.

[0130] When transmitting DATA[1], the MCU 61 controls the switch circuit 72 to the ON state (short-circuit state). When the switch circuit 72 is controlled to the ON state (short-circuit state), the impedance seen from the power transmitting resonant circuit 915 toward the power receiving resonant circuit 11 changes even more significantly due to the addition of the component of the resistive element 71. This allows the amount of change in the transmission current itx when transmitting DATA[1] to be increased. Therefore, the power transmitting device 91 can more reliably detect DATA[1].

[0131] In this way, the power receiving device 10C can achieve the same effects as the power receiving device 10, and can also more reliably achieve information transmission.

[0132] [Fifth Embodiment] A wireless power supply system according to a fifth embodiment of the present invention will be described with reference to the drawings. Fig. 12 is a diagram showing an example of the configuration of a power receiving device of the wireless power supply system according to the fifth embodiment of the present invention.

[0133] 12 , the wireless power supply system according to the fifth embodiment differs from the wireless power supply system according to the fourth embodiment in that the load adjustment circuit 70 is replaced with a Zener diode ZD. Only the different points will be described below, and a description of the same points will be omitted.

[0134] The Zener diode ZD is connected in parallel to the smoothing capacitor 13. The Zener diode ZD has a cathode connected to the HI side and an anode connected to the LOW side.

[0135] The Zener voltage of the Zener diode ZD is set to be higher than the above-mentioned first power receiving voltage Vrec1 and lower than the second power receiving voltage Vrec2.

[0136] With this configuration, the power receiving device 10D can achieve the same effects as the power receiving device 10C.

[0137] Furthermore, in the power receiving device 10D, the current during the second reference voltage selection time Tit increases. This allows the power receiving device 10D to increase the amount of change in the transmission current itx during the transmission of DATA[1]. In this case, the receiving voltage Vrec during the second reference voltage selection time Tit is a voltage based on the Zener voltage, rather than the second receiving voltage Vrec2. However, when the received power is large, the receiving voltage Vrec is limited to the second receiving voltage Vrec2, rather than a voltage based on the Zener voltage.

[0138] (Another Aspect of Power Transmitting Device) Fig. 13 is a diagram showing another aspect of a power transmitting device. A power transmitting device 91B shown in Fig. 13 differs from the power transmitting device 91 shown in Fig. 2 described above in that information (data) from the power receiving device 10 is detected using a voltage applied to a power transmitting resonant circuit 915. Only the differences between the power transmitting device 91B and the power transmitting device 91 will be described below.

[0139] The power transmitting device 91B includes a DC power supply 911, an input capacitor 912, a power transmitting switching control circuit 913, a power transmitting power conversion circuit 914, a power transmitting resonant circuit 915, a rectifying element 9181, a capacitor 9182, a resistive element 9183, and a resistive element 9184. The rectifying element 9181, the capacitor 9182, the resistive element 9183, and the resistive element 9184 configure a "power transmitting detection circuit."

[0140] The rectifying element 9181 is a diode, and the anode terminal of the diode is connected to the node between the power transmitting coil 9151 and the resonance capacitor 9152. The cathode terminal of the diode is connected to the reference potential through the capacitor 9182.

[0141] The resistor element 9183 and the resistor element 9184 are connected in series. The series circuit of the resistor element 9183 and the resistor element 9184 is connected in parallel to the capacitor 9182. The node of the resistor element 9183 and the resistor element 9184 is connected to the power transmission switching control circuit 913.

[0142] In this configuration, when the transmission current itx changes, the voltage (transmission voltage) applied to the capacitor 9182 changes. The transmission voltage is divided by a voltage divider circuit made up of resistive elements 9183 and 9184, and input to the transmission switching control circuit 913. This enables the transmission switching control circuit 913 to detect changes in the transmission voltage and to detect information (data) from the power receiving device 10 based on these changes.

[0143] 10, 10A, 10B, 10C, 10D: power receiving device 11: power receiving resonance circuit 12: power receiving rectification circuit 13: smoothing capacitor 14: voltage conversion circuit 15: charging circuit 16, 16A, 16B, 16C: control circuit 61: MCU 64: comparator 70: load adjustment circuit 71: resistance element 72: switch circuit 91, 91B: power transmitting device 111: power receiving coil 112: resonance capacitor 620: switch circuit 621, 622, 623, 651, 652, 653: resistance element 630: switch circuit 631, 632, 640: reference voltage 650: switch circuit 911: DC power supply 912: input capacitor 913: power transmitting switching control circuit 914: power transmitting power conversion circuit 915: power transmitting resonance circuit 916, 9183, 9184: Resistor element 917: Differential amplifier circuit 9151: Power transmitting coil 9152: Resonant capacitor 9181: Rectifier element 9182: Capacitor BAT: Battery D11, D12, D21, D22: Diode itx: Power transmitting current POH: HI side output terminal POL: LOW side output terminal Q1, Q2, QH, QL: Switching element ZD: Zener diode Tc: Switching period Tdet: Detection period Tit: Second reference voltage selection time Vch: Charging voltage Vcp: Detection voltage Vcp1: First detection voltage Vcp2: Second detection voltage Vrec: Receiving voltage Vrec1: First receiving voltage Vrec2: Second receiving voltage Vref: Reference voltage Vref1, Vref1A: First reference voltage Vref2, Vref2A: second reference voltage

Claims

1. A wireless power supply system comprising a power transmitting device having a power transmitting resonant circuit including a power transmitting coil, and a power receiving device having a power receiving resonant circuit including a power receiving coil, and supplying power by electromagnetic field resonance coupling of the power receiving resonant circuit to an electromagnetic field generated by the power transmitting resonant circuit, wherein the power transmitting device comprises: a power transmitting power conversion circuit electrically connected to an input DC power source, converting DC power supplied from the input DC power source into AC power by switching operation of a switching element, and passing AC current to the electrically connected power transmitting coil; a power transmitting control circuit controlling the switching operation of the power transmitting power conversion circuit; and a power transmitting detection circuit detecting an electrical variable that changes in response to a change in the state of the electromagnetic field resonance coupling, wherein the power receiving device comprises: a power receiving rectifier circuit electrically connected to the power receiving resonant circuit, rectifying the AC power received by the power receiving coil constituting the power receiving resonant circuit; and a smoothing circuit electrically connected to the power receiving rectifier circuit, smoothing the power rectified by the power receiving rectifier circuit into a received DC voltage. a rectification control circuit electrically connected to the power receiving resonant circuit and changing a state of the electromagnetic resonance coupling by a rectification operation of the power receiving rectifier circuit, wherein the rectification control circuit controls execution and stop of the rectification operation of the power receiving rectifier circuit based on a control value set for the power receiving DC voltage so that the power receiving DC voltage becomes a predetermined value, and controls execution and stop of the rectification operation of the power receiving rectifier circuit based on a pattern for adjusting the control value, thereby changing the state of the electromagnetic resonance coupling, and transmitting information from the power receiving device to the power transmitting device.

2. The wireless power supply system according to claim 1, wherein the rectification control circuit stops the rectification operation and cuts off power reception when the receiving DC voltage exceeds a predetermined range.

3. The wireless power supply system according to claim 1 or 2, wherein the control value of the receiving voltage used for the information transmission is two-valued.

4. A wireless power supply system as described in any one of claims 1 to 3, wherein the rectification control circuit comprises: a comparator that compares a detection voltage based on the received voltage with a reference voltage; and a switching control circuit that switches the reference voltage to create a change in the state of the electromagnetic resonance coupling.

5. The wireless power supply system according to claim 3, wherein the reference voltage is configured using a resistive voltage divider circuit, and the switching control circuit switches the reference voltage using a semiconductor switch element.

6. A wireless power supply system as described in any one of claims 1 to 3, wherein the rectification control circuit comprises: a comparator that compares a detection voltage based on the received voltage with a reference voltage; and a switching control circuit that switches the detection voltage to create a change in the state of the electromagnetic resonance coupling, wherein the detection voltage is constructed using a resistive voltage divider circuit, and the switching control circuit switches the detection voltage by a semiconductor switch element.

7. The wireless power supply system of claim 1, wherein the power receiving device is provided with a load adjustment circuit capable of changing the impedance seen from the power transmitting device toward the power receiving rectifier circuit, and the rectifier control circuit uses the load adjustment circuit to change the load of the power receiving rectifier circuit and change the state of the electromagnetic resonance coupling.

8. A wireless power supply system according to any one of claims 1 to 6, wherein the power receiving device comprises a Zener diode connected in parallel to the smoothing circuit, and the rectification control circuit controls the execution and stop of the rectification operation of the power receiving rectifier circuit based on a Zener voltage.

9. A wireless power supply system according to any one of claims 1 to 8, wherein the frequency of the electromagnetic field resonance is in the 6.78 MHz band or the 13.56 MHz band.

10. A wireless power receiving device comprising: a power receiving resonant circuit including a power receiving coil and receiving power by electromagnetic resonance coupling with an electromagnetic field generated by a power transmitting device; a power receiving rectifier circuit electrically connected to the power receiving resonant circuit and rectifying the AC power received by the power receiving resonant circuit; a smoothing circuit electrically connected to the power receiving rectifier circuit and smoothing the power rectified by the power receiving rectifier circuit into a power receiving DC voltage; and a rectification control circuit electrically connected to the power receiving resonant circuit and changing a state of the electromagnetic resonance coupling by the rectification operation of the power receiving rectifier circuit, wherein the rectification control circuit controls execution and stop of the rectification operation of the power receiving rectifier circuit based on a control value set for the power receiving DC voltage so that the power receiving DC voltage becomes a predetermined value, and controls execution and stop of the rectification operation of the power receiving rectifier circuit based on a pattern for adjusting the control value to change the state of the electromagnetic resonance coupling, and transmits information from the power receiving device to the power transmitting device.

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