Tuning methods and apparatus for inductively coupled power transfer (ICPT) systems

• US 8,183,938 B2
• Filed: 04/28/2006
• Issued: 05/22/2012
• Est. Priority Date: 04/29/2005
• Status: Expired due to Fees

• Current Assignee: Auckland UniServices Limited (Auckland University)
• Original Assignee: Auckland UniServices Limited (Auckland University)
• Inventors: Boys, John Talbot, Covic, Grant Anthony
• Primary Examiner(s): Goodley, James E
• Application Number:
  US11/912,920
• Publication Number:
  US 20090302933A1
• Time in Patent Office: 2,216 Days
• Field of Search: 331/25, 331/36.C, 331/36.L, 323/356, 323/362
• US Class Current: 331/36.L
• CPC Class Codes: H01F 29/14 with variable magnetic bias amplitude modulation by means of variable impedance element H03C1/08 ; magnetic amplifiers H03F; circuits for automatic telephonic communication H04M3/00
• 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: H03J 5/246 using electronic means H03J5/244 takes precedence

Abstract

A method is provided for controlling a resonant circuit (1) of an ICPT system. The resonant circuit has a controlled variable reactance (2), and a predetermined perturbation is introduced in the magnitude of variable reactance. The change in a property of the resonant circuit in response to the perturbation is sensed, and the variable reactance is varied to alter the resonant frequency of the circuit in response to the sensed change.

Claims

1. A method for controlling a resonant circuit of an ICPT system;

the method comprising;

generating a cyclical signal;

using the cyclical signal to cause a cyclical perturbation in a magnitude of a variable reactance in the resonant circuit to thereby produce a cyclical perturbation in the resonant voltage or current of the resonant circuit;

sensing the perturbation in the resonant voltage or current of the resonant circuit;

correlating the sensed perturbation in the resonant voltage or current with the cyclical signal to provide a control signal; and

using the control signal to vary the variable reactance to alter the resonant frequency of the circuit.

2. A method as claimed in claim 1 wherein correlation of the sensed perturbation with the cyclical signal is used to determine whether the frequency of operation of the circuit is above or below the resonant frequency of the circuit.

3. A method as claimed in claim 1 wherein the step of varying the variable reactance comprises varying the reactance to bring the resonant frequency of the circuit toward a required frequency of operation.

4. A method as claimed in claim 1 wherein the step of varying the variable reactance comprises providing a desired output of the circuit and varying the reactance to change the resonant frequency of the circuit to bring an output of the resonant circuit toward a desired output.

5. A method as claimed in claim 1 further comprising integrating the sensed perturbation to provide the control signal for varying the variable reactance.

6. A method as claimed in claim 1 wherein the cyclical signal comprises an alternating control signal of predetermined magnitude.

7. A method as claimed in claim 1 wherein the perturbation varies the variable reactance in such a way as to alter the frequency of the resonant circuit over a range of approximately 1%.

8. A method as claimed in claim 1 wherein the perturbation results in the frequency of the resonant circuit being changed in a cyclical fashion at a rate of approximately 20 Hz.

9. A method as claimed in claim 1 wherein the step of varying the variable reactance comprises varying a current applied to a saturable inductor.

10. An ICPT system comprising:

a resonant circuit having a variable reactance and a controller adapted to;

generate a cyclical signal;

use the cyclical signal to cause a cyclical perturbation in a magnitude of a variable reactance in the resonant circuit thereby producing a cyclical perturbation in the resonant voltage or current of the resonant circuit;

sense the perturbation in the resonant voltage or current of the resonant circuit; and

correlate the sensed perturbation in the resonant voltage or current with the cyclical signal to provide a control signal, and use the control signal to vary the variable reactance to alter the resonant frequency of the circuit.

11. An ICPT system as claimed in claim 10 wherein the controller controls the perturbation to be cyclical.

12. An ICPT system as claimed in claim 10 wherein the controller includes an integrator to integrate the sensed change to provide a control signal for varying the variable reactance.

13. An ICPT system as claimed in claim 10 wherein the variable reactance comprises a variable capacitance.

14. An ICPT system as claimed in claim 10 wherein the variable reactance comprises a variable inductance.

15. An ICPT system as claimed in claim 14 wherein the variable reactance comprises a saturable inductor.

16. An ICPT system pick-up including a resonant circuit having a variable reactance, and a controller adapted to:

generate a cyclical signal;

use the cyclical signal to cause a cyclical perturbation in a magnitude of a variable reactance in the resonant circuit thereby producing a cyclical perturbation in the resonant voltage or current of the resonant circuit;

sense the perturbation in the resonant voltage or current of the resonant circuit; and

correlate the sensed perturbation in the resonant voltage or current with the cyclical signal to provide a control signal, and use the control signal to vary the variable reactance to alter the resonant frequency of the circuit.

17. An ICPT system power supply including a resonant circuit having a variable reactance, and a controller adapted to:

generate a cyclical signal;

use the cyclical signal to cause a cyclical perturbation in a magnitude of a variable reactance in the resonant circuit thereby producing a cyclical perturbation in the resonant voltage or current of the resonant circuit;

sense the perturbation in the resonant voltage or current of the resonant circuit; and

correlate the sensed perturbation in the resonant voltage or current with the cyclical signal to provide a control signal, and use the control signal to vary the variable reactance to alter the resonant frequency of the circuit.