An Inductive Power Receiver

1 . An inductive power receiver for an inductive power transfer system comprising:

a power receiving coil;

a rectifier configured to convert a voltage from the power receiving coil into a substantially DC voltage for a load; and

a power regulation circuit configured to adjust a DC bias voltage across at least one capacitor to regulate the DC voltage.

2 . A receiver as claimed in claim 1 , wherein the rectifier is a bridge circuit configuration and the at least one capacitor is connected within the bridge rectifier.

3 . A receiver as claimed in claim 2 , wherein the rectifier is a synchronous bridge rectifier.

4 . A receiver as claimed in claim 1 , wherein the power regulation circuit comprises one or more switching devices configured to control the flow of current through the at least one capacitor.

5 . A receiver as claimed in claim 1 , wherein the DC bias voltage is determined based on a load regulation criteria.

6 . A receiver as claimed in claim 5 , wherein the load regulation criteria is based on a voltage and/or current from the power receiving coil.

7 . A receiver as claimed in claim 1 , wherein the bridge rectifier is formed of switching devices and the controller is configured to dynamically control the conduction timing of switching devices to operate as a bridge rectifier.

8 . A receiver as claimed in claim 7 , wherein the controller is configured to dynamically control the conduction timing of switching devices in the rectifier substantially in synchronism with the received AC power signal.

9 . A receiver as claimed in claim 1 , wherein the power regulation circuit comprises a first switching device and a second switching device, during a first half cycle the power regulation circuit is configured to:

charge the capacitor when the first switching device is nonconductive and the second switching device is nonconductive,

maintain a bias voltage in the capacitor when the first switching device is conductive and the second switching device is conductive, and

during a second half cycle:

maintain capacitor voltage when the first switching device is conductive and the second switching device is nonconductive, and

discharge the capacitor when the first switching device is nonconductive and the second switching device is conductive.

10 . A receiver as claimed in claim 1 , wherein one or more of the switching devices is an MOSFET device, and the controller adjusts a voltage applied to a gate of each MOSFET device to control the conduction thereof.

11 . A receiver as claimed in claim 1 , wherein the receiver is configured for integration into a cellular phone for charging from a charging mat using inductive power transfer.

12 . A method of controlling an inductive power receiver comprising:

generating a DC bias voltage across at least one capacitor in the receiver; and

regulating the load based on the DC bias voltage.