Inductive power transfer pick-up circuit with output current doubler

1. An inductive power transfer (IPT) pick-up circuit comprising:

a resonant circuit comprising an inductive pick-up coil and a parallel tuning capacitor;

a rectifier comprising at least two diodes coupled to the resonant circuit and adapted to rectify an AC current received therefrom; and

at least two inductors, wherein each of the at least two inductors is arranged to couple the rectifier to an output of the pick-up circuit and alternately store and release energy as current to the output.

2. The IPT pick-up circuit as claimed in claim 1 wherein the inductors are arranged whereby a first of the at least two inductors stores energy during a positive period of the AC current and releases energy to the output during a negative period, and a second of the at least two inductors stores energy during the negative period of the AC current and releases energy to the output during the positive period.

3. The IPT pick-up circuit as claimed in claim 1 wherein energy input to the inductors is pulsed, but energy output of the inductors is ordinarily substantially continuous.

4. The IPT pick-up circuit as claimed in claim 1 wherein the rectifier comprises a diode bridge rectifier, and wherein the inductors are each coupled in series between respective common-cathode diodes of the diode bridge rectifier and the output of the pick-up circuit.

5. The IPT pick-up circuit as claimed in claim 1 wherein the rectifier comprises at least two diodes, respective anodes of the at least two diodes are coupled with the output, and respective cathodes of the at least two diodes are coupled with both the resonant circuit and a respective one of the at least two inductors.

6. The IPT pick-up circuit as claimed in claim 1 wherein the pick-up circuit further comprises a mode switch selectively operable to reconfigure the circuit from a first mode to a second mode wherein the inductors are coupled in parallel between the rectifier and the output of the pick-up circuit.

7. The IPT pick-up circuit as claimed in claim 6 wherein the output current of the pick-up circuit in the first mode is greater than in the second mode.

8. The IPT pick-up circuit as claimed in claim 6 wherein in the second mode the at least two inductors both act as a choke to smooth the rectified AC current during both positive and negative periods of the AC current.

9. The IPT pick-up circuit as claimed in claim 1 wherein the resonant circuit further comprises an additional capacitor in series with the pick-up coil, and wherein the resonant circuit is partially series-tuned.

10. The IPT pick-up circuit as claimed in claim 1 wherein the pick-up circuit further comprises a power control switch operable to decouple the output from the rectifier and/or resonant circuit.

11. The IPT pick-up circuit as claimed in claim 1 wherein the pick-up circuit further comprises a decoupling switch in parallel with the resonant circuit for selectively decoupling the rectifier from the resonant circuit.

12. The IPT pick-up circuit as claimed in claim 1 wherein:

the at least two inductors each comprise a first terminal coupled with the rectifier and a second terminal coupled with an output of the pick-up; and

the pick-up circuit further comprises a mode switch operable to select a mode of operation of the circuit, wherein the first terminal of each of the at least two inductors in a first mode is coupled with a cathode of a respective one of the at least two diodes, and in a second mode is coupled with both cathodes.

13. The IPT pick-up circuit as claimed in claim 12 wherein an output current of the circuit is substantially doubled in the first mode with respect to the second mode.

14. The IPT pick-up circuit as claimed in claim 12 wherein the pickup circuit further comprises a controller associated with the mode switch, and the controller is operable to control the mode switch to control an output current of the pick-up.

15. An inductive power transfer pick-up circuit comprising:

a resonant circuit comprising a tuned inductive pick-up coil;

a rectifier coupled to the resonant circuit and adapted to rectify an AC current received therefrom; and

at least two inductors, wherein each of the at least two inductors is arranged to couple the rectifier to an output of the pick-up circuit and alternately store and release energy as current to the output.

16. The inductive power transfer pick-up circuit of claim 15 , wherein the pick-up circuit comprises at least one switch, and the pick-up circuit is configured to operate the switch to decouple the output of the pick-up circuit from the resonant circuit.

17. The inductive power transfer pick-up circuit of claim 15 , wherein the pick-up is configured to produce an output current that is greater than a short circuit current of the tuned inductive pick-up coil.

18. The inductive power transfer pick-up circuit of claim 17 , wherein the tuned inductive pick-up coil is at least partially tuned by a series tuning capacitor.

19. The inductive power transfer pick-up circuit of claim 15 , wherein the pick-up is configured to produce an output current that is substantially double a short circuit current of the tuned inductive pick-up coil.

20. The inductive power transfer pick-up circuit of claim 15 , wherein the rectifier is a diode bridge rectifier, and the at least two inductors are each coupled in series between respective common-cathode diodes of the diode bridge rectifier and the output of the pick-up circuit.