Variable capacitor for resonant power transfer systems

• US 10,383,990 B2
• Filed: 07/27/2013
• Issued: 08/20/2019
• Est. Priority Date: 07/27/2012
• Status: Active Grant

• Current Assignee: TC1 LLC (Abbott Laboratories Incorporated)
• Original Assignee: TC1 LLC (Abbott Laboratories Incorporated)
• Inventors: Petersen, Ethan
• Primary Examiner(s): Barnie, Rexford N
• Assistant Examiner(s): Willoughby, Terrence R
• Application Number:
  US14/414,820
• Publication Number:
  US 20150207330A1
• Time in Patent Office: 2,215 Days
• CPC Class Codes: H02J 5/00 Circuit arrangements for transfer of electric power between ac networks and dc networks H02J3/36 takes precedence
• CPC Class Codes: H02J 50/10 using inductive coupling
• CPC Class Codes: H02J 50/12 of the resonant type
• CPC Class Codes: H02J 50/40 using two or more transmitting or receiving devices H02J50/50 takes precedence

Abstract

Systems and designs for tuning a wireless power transfer system are provided, which may include any number of features. In one embodiment, a wireless power transfer system can include first and second switched capacitor circuits electrically connected to opposite poles of the inductor of a resonator in the wireless power system. The first and second switched capacitor circuits can be switched on and off with MOSFETS to change a capacitance of the circuits, and thus an effective capacitance of the resonator. Methods of use are also provided.

Claims

1. A resonator of a wireless power transfer system, comprising:

an inductor adapted to receive or transmit wireless power and comprising a first pole and an opposite second pole;

first and second switched capacitor circuits electrically connected to the inductor, each of the first and second switched capacitor circuits comprising a first capacitor in series with a MOSFET and a second capacitor in parallel with the first capacitor, wherein the first and second capacitors of the first switched capacitor circuit are each directly electrically connected to the inductor first pole, and wherein the first and second capacitors of the second switched capacitor circuit are each directly electrically connected to the inductor second pole; and

a controller electrically connected to the first and second switched capacitor circuits, wherein the controller switches on the MOSFET of the first switched capacitor circuit at the same time that the MOSFET of the second switched capacitor circuit is switched off, and wherein the controller switches off the MOSFET of the first switched capacitor circuit at the same time that the MOSFET of the second switched capacitor circuit is switched on, causing the first and second switched capacitor circuits to be switched in and out on opposite half cycles relative to one another, and causing the resonator to achieve a balanced waveform.

2. The resonator of claim 1, wherein the controller is configured to operate the MOSFETS at a 50% duty cycle to achieve a minimum effective capacitance of the wireless power transfer system.

3. The resonator of claim 1, wherein the controller is configured to operate the MOSFETS at a 100% duty cycle to achieve a maximum effective capacitance of the wireless power transfer system.

4. The resonator of claim 1 wherein the controller is configured to control the effective capacitance of the wireless power transfer system to optimize a power transfer efficiency of the wireless power transfer system.

5. The resonator of claim 1 wherein the controller is configured to control the effective capacitance of the wireless power transfer system to optimize a coupling coefficient of the wireless power transfer system.

6. The resonator of claim 1 wherein the controller is configured to monitor a system parameter in response to the adjusted effective capacitance, and to iteratively adjust effective capacitance to improve performance of the system parameter.

7. The resonator of claim 6 wherein the system parameter comprises a coupling coefficient of the wireless power transfer system.

8. The resonator of claim 6 wherein the system parameter comprises a power transfer efficiency of the wireless power transfer system.

9. The resonator of claim 1, wherein the resonator comprises a receiver resonator adapted to be implanted within a patient.

10. The resonator of claim 9 wherein the inductor is configured to receive wireless power from an external transmitter resonator disposed outside the patient.

11. A method of controlling a wireless power transfer system, comprising the steps of:

transmitting or receiving wireless power with an inductor of a resonator, the inductor including a first pole and an opposite second pole, the resonator further including first and second switched capacitor circuits, each of the first and second switch capacitor circuits including a first capacitor in series with a MOSFET and a second capacitor in parallel with the first capacitor, the first switched capacitor circuit directly electrically connected to the first pole of the inductor, and the second switched capacitor circuit directly electrically connected to the second pole of the inductor; and

adjusting with a controller an effective capacitance of the resonator by changing a capacitance of the first and second switched capacitor circuits connected to the inductor; and

switching, with the controller, the first and second switched capacitor circuits in and out on opposite half cycles relative to one another to achieve a balanced waveform on the resonator by;

switching on the MOSFET of the first switched capacitor circuit at the same time that the MOSFET of the second switched capacitor circuit is switched off; and

switching off the MOSFET of the first switched capacitor circuit at the same time that the MOSFET of the second switched capacitor circuit is switched on.

12. The method of claim 11 further comprising monitoring a system parameter in response to adjusting the effective capacitance, and iteratively adjusting the effective capacitance to improve performance of the system parameter.

13. The method of claim 12 wherein the system parameter comprises a coupling coefficient of the wireless power transfer system.

14. The method of claim 12 wherein the system parameter comprises a power transfer efficiency of the wireless power transfer system.

15. The method of claim 11, wherein adjusting an effective capacitance comprises adjusting the effective capacitance through a continuous range of values by controlling times when the MOSFETS are switched on and off.