POWER TRANSFER SYSTEM

• US 20130300210A1
• Filed: 07/18/2013
• Published: 11/14/2013
• Est. Priority Date: 01/26/2011
• Status: Active Grant

• Current Assignee: Murata Manufacturing Co Limited
• Original Assignee: Murata Manufacturing Co Limited
• Inventors: HOSOTANI, Tatsuya
• Granted Patent: US 9,378,888 B2
• Time in Patent Office: Days
• US Class Current: 307/104
• CPC Class Codes: H01F 38/14 Inductive couplings for wireless supply or distribution of electric power using inductive coupling H02J50/10
• CPC Class Codes: H02J 50/12 of the resonant type
• CPC Class Codes: H02J 50/80 involving the exchange of data, concerning supply or distribution of electric power, between transmitting devices and receiving devices
• CPC Class Codes: H02J 7/00034 Charger exchanging data with an electronic device, i.e. telephone, whose internal battery is under charge
• CPC Class Codes: H02M 1/0058 by employing soft switching techniques, i.e. commutation of transistors when applied voltage is zero or when current flow is zero using an auxiliary actively switched resonant commutation circuit connected to an intermediate DC voltage or between two push-pull branches of an inverter bridge H02M7/4811; in resonant inverters H02M7/4815; in inverters operating from a resonant DC source H02M7/4826
• CPC Class Codes: H02M 3/3376 with automatic control of output voltage or current
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Abstract

A power-transmission-unit-side resonant circuit includes a resonant capacitor connected in series with a power transmission coil and a power-reception-unit-side resonant circuit including a resonant capacitor connected in series with a power reception coil resonate with each other to cause sympathetic vibration. This allows power to be transferred using two kinds of coupling via the magnetic field and the electric field between the power transmission coil and the power reception coil. Also, operation is performed at a switching frequency that is higher than a specific resonant frequency of the entire multi-resonant circuit, such that a ZVS operation is performed. As a result, a switching loss is reduced by a large amount and a highly efficient operation is performed thus enabling a power transfer system with a reduced size and an increased power conversion efficiency to be provided.

Claims

1. (canceled)

2. A power transfer system comprising:

a power transmission unit including a power transmission coil; and

a power reception unit including a power reception coil;

wherein

the power transmission unit includes;

a power-transmission-unit-side resonant capacitor that constitutes a power-transmission-unit-side resonant circuit together with the power transmission coil; and

a power-transmission-unit-side alternating-current voltage generation circuit that is connected to the power transmission coil, that includes a switching circuit, and that generates an alternating-current voltage from a direct-current voltage input thereto, the switching circuit being a parallel circuit in which a switching element, a diode, and a capacitor are connected in parallel with each other;

the power reception unit includes;

a power-reception-unit-side resonant capacitor that constitutes a power-reception-unit-side resonant circuit together with the power reception coil; and

a power-reception-unit-side rectifier circuit that is connected to the power reception coil and that rectifies an alternating-current voltage produced in the power reception coil into a direct-current voltage;

wherein

mutual inductance and mutual capacitance that are equivalently generated between the power transmission coil and the power reception coil constitute an electromagnetic coupling circuit, the power-transmission-unit-side resonant circuit and the power-reception-unit-side resonant circuit resonate with each other, and power is transferred from the power transmission unit to the power reception unit;

energy of power that has not been transmitted from the power transmission unit is retained in the power-transmission-unit-side resonant circuit as resonance energy; and

energy that has not been supplied to an output among energy of power received by the power reception unit is retained in the power-reception-unit-side resonant circuit as resonance energy.

5. The power transfer system according to claim 2, wherein the power reception unit includes an information transmission circuit that detects output information about an output from the power-reception-unit-side rectifier circuit and transmits the output information to the power transmission unit;

and

the power transmission unit includes an output information reception circuit that receives the output information, and a to-be-transferred power control circuit that controls the power-transmission-unit-side alternating-current voltage generation circuit in accordance with the output information so as to control to-be-transferred power.

6. The power transfer system according to claim 5, wherein the information transmission circuit is a circuit that transmits the output information via wireless communication;

and

the output information reception circuit is a circuit that receives the output information via wireless communication.

7. The power transfer system according to claim 5, wherein the information transmission circuit is a circuit that converts an electric signal into an optical signal and transmits the output information as an optical signal;

and

the output information reception circuit is a circuit that converts an optical signal into an electric signal and receives the output information as an electric signal.

8. The power transfer system according to claim 2, wherein the switching circuit includes a high-side switching circuit and a low-side switching circuit;

and

the power-transmission-unit-side alternating-current voltage generation circuit controls to-be-transferred power by performing Pulse Frequency Modulation in which a switching frequency at which the high-side switching circuit and the low-side switching circuit are alternately turned on/off is changed.

9. The power transfer system according to claim 2, wherein the switching circuit includes a high-side switching circuit and a low-side switching circuit;

and

the power-transmission-unit-side alternating-current voltage generation circuit controls to-be-transferred power by performing On-periods Ratio Modulation in which a ratio between conduction periods of a first switching circuit and a second switching circuit is modulated, while alternately turning the high-side switching circuit and the low-side switching circuit on/off at a fixed switching frequency.

10. The power transfer system according to claim 2, wherein the power-reception-unit-side rectifier circuit is a synchronous rectifier circuit including switching elements.

11. The power transfer system according to claim 10, wherein the power reception unit includes an operating frequency control circuit that controls an operating frequency of the synchronous rectifier circuit, and controls to-be-received power by using the operating frequency.

12. The power transfer system according to claim 2, wherein the power reception unit includes a control circuit that controls a circuit included in the power reception unit, and the control circuit is operated using power received by the power reception unit.

13. The power transfer system according to claim 2, wherein the power transfer system performs bidirectional power transfer, and

when power is transferred from an output of the power-reception-unit-side rectifier circuit, the power-reception-unit-side rectifier circuit functions as the power-transmission-unit-side alternating-current voltage generation circuit and the power-transmission-unit-side alternating-current voltage generation circuit functions as the power-reception-unit-side rectifier circuit.

14. The power transfer system according to claim 2, wherein the power transfer system includes a plurality of the power reception units, the power-reception-unit-side resonant circuits of the plurality of power reception units have different resonant frequencies, and the power-transmission-unit-side alternating-current voltage generation circuit switches the switching circuit on/off at a switching frequency corresponding to a destination to which power is to be transferred.

15. The power transfer system according to claim 8, wherein the switching frequency is set to be higher than a resonant frequency at which the power-transmission-unit-side resonant circuit and the power-reception-unit-side resonant circuit resonate with each other so that a phase of a waveform of a current that flows through the power transmission coil lags behind that of a waveform of the alternating-current voltage, and a dead time during which both the high-side switching element and the low-side switching element are in an off state is set so that a zero voltage switching operation is performed during the dead time.

16. The power transfer system according to claim 2, wherein a parallel resonant capacitor is provided in parallel with the power transmission coil or the power reception coil.

17. The power transfer system according to claim 16, wherein the parallel resonant capacitor is constituted by stray capacitance that serves as equivalent capacitance resulting from electrical coupling generated between the power transmission coil and the power reception coil.

18. The power transfer system according to claim 16, wherein the parallel resonant capacitor is constituted by stray capacitance that is generated between ends of the power transmission coil or the power reception coil.

19. The power transfer system according to claim 2, wherein the power transmission coil and the power reception coil are air-core inductors.

20. The power transfer system according to claim 2, the mutual inductance is an equivalent magnetizing inductance resulting from magnetic coupling generated between the power transmission coil and the power reception coil.

21. The power transfer system according to claim 2, wherein leakage inductance that is not involved in coupling, among an inductance component of the power transmission coil or the power reception coil, is used as an inductor that constitutes the power-transmission-unit-side resonant circuit or the power-reception-unit-side resonant circuit.

3. A power transfer system comprising:

a power transmission unit including a power transmission coil; and

a power reception unit including a power reception coil;

wherein

the power transmission unit includes;

a power-transmission-unit-side resonant capacitor that constitutes a power-transmission-unit-side resonant circuit together with the power transmission coil; and

a power-transmission-unit-side alternating-current voltage generation circuit that is connected to the power transmission coil, that includes a switching circuit, and that generates an alternating-current voltage from a direct-current voltage input thereto, the switching circuit being a parallel circuit in which a switching element, a diode, and a capacitor are connected in parallel with each other;

the power reception unit includes;

a power-reception-unit-side resonant capacitor that constitutes a power-reception-unit-side resonant circuit together with the power reception coil; and

a power-reception-unit-side rectifier circuit that is connected to the power reception coil and that rectifies an alternating-current voltage produced in the power reception coil into a direct-current voltage;

wherein

mutual inductance that is equivalently generated between the power transmission coil and the power reception coil constitutes an electromagnetic coupling circuit, the power-transmission-unit-side resonant circuit and the power-reception-unit-side resonant circuit resonate with each other, and power is transferred from the power transmission unit to the power reception unit;

energy of power that has not been transmitted from the power transmission unit is retained in the power-transmission-unit-side resonant circuit as resonance energy; and

energy that has not been supplied to an output among energy of power received by the power reception unit is retained in the power-reception-unit-side resonant circuit as resonance energy.

4. A power transfer system comprising:

a power transmission unit including a power transmission coil; and

a power reception unit including a power reception coil;

wherein

the power transmission unit includes;

a power-transmission-unit-side resonant inductor that constitutes a power-transmission-unit-side resonant circuit together with a power transmission capacitor; and

a power-transmission-unit-side alternating-current voltage generation circuit that is connected to the power transmission coil, that includes a switching circuit, and that generates an alternating-current voltage from a direct-current voltage input thereto, the switching circuit being a parallel circuit in which a switching element, a diode, and a capacitor are connected in parallel with each other;

the power reception unit includes;

a power-reception-unit-side resonant inductor that constitutes a power-reception-unit-side resonant circuit together with a power reception capacitor; and

a power-reception-unit-side rectifier circuit that is connected to the power reception coil and that rectifies an alternating-current voltage produced in the power reception coil into a direct-current voltage;

wherein

mutual capacitance that is equivalently generated between the power transmission coil and the power reception coil constitutes an electrical coupling circuit, the power-transmission-unit-side resonant circuit and the power-reception-unit-side resonant circuit resonate with each other, and power is transferred from the power transmission unit to the power reception unit;

energy of power that has not been transmitted from the power transmission unit is retained in the power-transmission-unit-side resonant circuit as resonance energy; and

energy that has not been supplied to an output among energy of power received by the power reception unit is retained in the power-reception-unit-side resonant circuit as resonance energy.