Wireless power feeder, wireless power receiver, and wireless power transmission system

• US 8,729,735 B2
• Filed: 11/11/2010
• Issued: 05/20/2014
• Est. Priority Date: 11/30/2009
• Status: Active Grant

• Current Assignee: TDK Corporation
• Original Assignee: TDK Corporation
• Inventors: Urano, Takashi
• Primary Examiner(s): KAPLAN, HAL IRA
• Application Number:
  US12/944,566
• Publication Number:
  US 20110127846A1
• Time in Patent Office: 1,286 Days
• Field of Search: 307/104
• US Class Current: 307/104
• CPC Class Codes: G01R 25/00 Arrangements for measuring phase angle between a voltage and a current or between voltages or currents
• CPC Class Codes: G05F 1/46 wherein the variable actually regulated by the final control device is dc G05F1/625 takes precedence
• 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

Abstract

Power is fed from a feeding coil L2 to a receiving coil L3 by magnetic resonance. A VCO 202 alternately turns ON/OFF switching transistors Q1 and Q2 at a drive frequency fo, whereby AC power is fed to the feeding coil L2, and then the AC power is fed from the feeding coil L2 to the receiving coil L3. A phase detection circuit 114 detects a phase difference between the current phase and voltage phase, and the VCO 202 adjusts the drive frequency fo such that the phase difference becomes zero. When load voltage is changed, the detected current phase value is adjusted with the result that the drive frequency fo is adjusted.

Claims

1. A wireless power feeder for feeding power from a feeding coil to a receiving coil, comprising:

a power transmission control circuit that feeds AC power to the feeding coil at a drive frequency;

a feeding coil circuit that includes the feeding coil and a capacitor and resonates at a resonance frequency of the receiving coil;

a phase detection circuit that detects a phase difference between the voltage phase and current phase of the AC power; and

a signal receiving circuit that receives an output signal indicating the magnitude of an output from a power receiving side of the AC power, wherein the power transmission control circuit adjusts the drive frequency so as to reduce the phase difference to make the drive frequency track the resonance frequency, and the phase detection circuit performs ex-post adjustment of the detected value of one or both of the voltage and current phases according to the output signal.

2. The wireless power feeder according to claim 1, wherein the phase detection circuit converts one or both of voltage and current components of the AC power into a signal having a saw-tooth waveform for detection of the phase difference.

3. The wireless power feeder according to claim 1, wherein the signal receiving circuit receives the output signal as a light signal.

4. The wireless power feeder according to claim 1, wherein the phase detection circuit compares a first phase value indicating a timing at which the voltage level of the AC power becomes a first reference value and a second phase value indicating a timing at which the current level of the AC power becomes a second reference value to detect the phase difference and changes one or both of the first and second reference values based on the output signal to perform ex-post adjustment of one or both of the first and second phase values.

5. The wireless power feeder according to claim 1, wherein the output signal is an AC signal indicating the magnitude of the output by the magnitude of signal frequency.

6. The wireless power feeder according to claim 1, further comprising an exciting coil that is magnetically coupled to the feeding coil and feeds AC power fed from the power transmission control circuit to the feeding coil, wherein the power transmission control circuit includes first and second current paths and makes first and second switches connected in series respectively to the first and second current paths alternately conductive at the drive frequency to feed the AC power to the exciting coil.

7. The wireless power feeder according to claim 1, further comprising a detection coil that generates inductive current using a magnetic field generated by the AC power, wherein the phase detection circuit measures the phase of the inductive current flowing in the detection coil to achieve measurement of the current phase of the AC power.

8. A wireless power receiver that receives AC power fed from the wireless power feeder as claimed in claim 1 at a receiving coil, the receiver comprising:

a receiving coil circuit that includes the receiving coil and a capacitor and resonates at the resonance frequency of the feeding coil;

a loading circuit that includes a loading coil that is magnetically coupled to the receiving coil to receive the AC power from the receiving coil and a load that receives power from the loading coil; and

a signal transmission circuit that transmits, to the wireless power feeder, an output signal indicating the magnitude of output voltage to be applied to a part of the loading circuit.

9. The wireless power receiver according to claim 8, wherein the signal transmission circuit transmits the output signal as a signal indicating a difference value between the output voltage and a reference voltage.

10. The wireless power receiver according to claim 9, wherein the value of the reference voltage is adjustable.

11. The wireless power receiver according to claim 8, wherein the output signal is an AC signal indicating the magnitude of the output voltage by the magnitude of signal frequency.

12. The wireless power receiver according to claim 8, wherein the loading circuit includes a rectification circuit, and the output voltage is generated by the rectification circuit as a DC current.

13. A wireless power transmission system for feeding power from a feeding coil to a receiving coil, comprising:

a power transmission control circuit that feeds AC power to the feeding coil at a drive frequency;

a feeding coil circuit that includes the feeding coil and a first capacitor;

a receiving coil circuit that includes the receiving coil and a second capacitor;

a loading circuit that includes a loading coil that is magnetically coupled to the receiving coil to receive the AC power from the receiving coil and a load that receives power from the loading coil; and

a phase detection circuit that detects a phase difference between the voltage phase and current phase of the AC power, wherein the power transmission control circuit adjusts the drive frequency so as to reduce the phase difference, and the phase detection circuit performs ex-post adjustment of the detected value of one or both of the voltage and current phases according to the magnitude of an output voltage to be applied to a part of the loading circuit.