TUNABLE WIRELESS ENERGY TRANSFER SYSTEMS

• US 20110193416A1
• Filed: 01/06/2011
• Published: 08/11/2011
• Est. Priority Date: 09/27/2008
• Status: Active Grant

• Current Assignee: WiTricity Corporation
• Original Assignee: WiTricity Corporation
• Inventors: Lou, Herbert T., Kesler, Morris P., Karalis, Aristeidis, Fiorello, Ron, Hall, Katherine L., Campanella, Andrew J.
• Granted Patent: US 8,643,326 B2
• Time in Patent Office: Days
• US Class Current: 307/104
• CPC Class Codes: B60L 2200/26 Rail vehicles
• CPC Class Codes: H01F 38/14 Inductive couplings for wireless supply or distribution of electric power using inductive coupling H02J50/10
• CPC Class Codes: H01Q 7/00 Loop antennas with a substantially uniform current distribution around the loop and having a directional radiation pattern in a plane perpendicular to the plane of the loop
• CPC Class Codes: H02J 50/12 of the resonant type
• CPC Class Codes: H03H 7/40 Automatic matching of load impedance to source impedance

Abstract

Described herein are improved configurations for a wireless power transfer. A power source for driving a resonator includes a switching amplifier. The duty cycle of the switching amplifier may be adjusted as well as optionally inductors and/or capacitors of the circuit to improve the efficiency of power transfer from the power source to the resonators when the parameters of the resonant load change.

Claims

1. In a system adapted for wireless power transfer, a tunable resonant amplifier circuit for driving an inductive load having a varying impedance, the circuit comprising:

a switching amplifier with a variable duty cycle;

an inductive load;

a connection between the inductive load and the switching amplifier, the connection including at least one tunable component; and

a feedback loop for adjusting the at least one tunable component and the duty cycle of the amplifier;

wherein the feedback loop adjusts the duty cycle of the amplifier and the at least one tunable component to maintain substantially zero voltage switching and zero current switching at the output of the amplifier under different load conditions of the inductive load.

2. The circuit of claim 1, wherein the at least one tunable component includes a tunable capacitor.

3. The circuit of claim 2, wherein the tunable capacitor is in series with the inductive load.

4. The circuit of claim 2, wherein the tunable capacitor is in parallel with the inductive load.

5. The circuit of claim 1, wherein the connection between the inductive load and the switching amplifier includes more than one tunable component.

6. The circuit of claim 1, wherein the switching amplifier uses a variable switching frequency.

7. The circuit of claim 1, wherein a bus voltage of the switching amplifier is variable and is used to control an amount of power delivered to the inductive load.

8. The circuit of claim 1, wherein the feedback loop includes an impedance measuring facility.

9. The circuit of claim 8, wherein the feedback loop includes a processor, the processor configured to monitor an impedance at an output of the switching amplifier and to compute an adjustment to the variable duty cycle of the switching amplifier such that zero voltage switching is substantially maintained.

10. The circuit of claim 9, wherein the processor is configured to compute a second adjustment to at least one tunable component such that zero current switching is substantially maintained.

11. The circuit of claim 1, wherein the inductive load includes a high-Q magnetic resonator.

12. The circuit of claim 11, wherein the circuit is used as a source in a wireless power transmission system.

13. A method of tuning a resonant amplifier circuit in a wireless power transfer facility that includes a connection between a switching amplifier and an inductive load having a varying impedance, the method comprising the steps of:

measuring a number of parameters at an output of the switching amplifier;

adjusting a duty cycle of the switching amplifier; and

adjusting at least one tunable component in the connection between the switching amplifier and the inductive load;

wherein adjusting the duty cycle of the switching amplifier and adjusting at least one tunable component are controlled to maintain a substantially zero voltage switching and a substantially zero current switching at the output of the switching amplifier under different load conditions of the inductive load.

14. The method of claim 13, wherein the at least one tunable component includes a tunable capacitor.

15. The method of claim 13, wherein measuring a number of parameters includes measuring an impedance at the output of the switching amplifier.

16. The method of claim 15, further comprising the steps of computing necessary adjustments to the duty cycle of the switching amplifier and adjustments to the at least one tunable component, based on the impedance, to maintain substantially zero voltage and substantially zero current switching at the output of the switching amplifier.

17. The method of claim 13, wherein the inductive load and at least a part of the connection between the switching amplifier and the inductive load form a high-Q magnetic resonator.

18. The method of claim 17, wherein the circuit is used as a source in a wireless power transmission system.