Synchronous switching power supply

1. A method in a power supply comprising:

transferring energy from a power source to an inductor by selectably closing a primary switch between the power source and the inductor, the transferring energy from the power source to the inductor comprising transferring energy to a first winding of the inductor;

transferring energy from the inductor to an energy storage element and to a load coupled to the inductor by selectably closing one or more additional switches to selectively connect the load across the inductor, wherein the primary switch and the one or more additional switches are synchronously controlled and wherein transferring energy from the inductor to the energy storage element comprises connecting a second winding of the inductor to the energy storage element to charge the energy storage element; and

transferring energy from the energy storage element to the load by:

connecting the charged energy storage element in reverse polarity to the second winding of the inductor to re-energize the inductor; and

connecting the load to the second winding of the re-energized inductor.

2. A method according to claim 1 wherein the first winding of the inductor receives a varying input voltage from the power source through the primary switch, and wherein transferring energy from the inductor to the energy storage element and to the load comprises:

monitoring one or more load parameters to determine load conditions; and,

when the load conditions meet a load requirement, disconnecting the load from the second winding of the inductor and directing any remaining energy in the inductor to the energy storage element.

3. A method according to claim 2 wherein the varying input voltage comprises a rectified AC voltage having a first frequency, the method comprising controlling the primary switch at a second frequency substantially higher than the first frequency.

4. A method according to claim 3 wherein the second frequency exceeds 1 MHz.

5. A method according to claim 2 wherein transferring energy from the inductor to the energy storage element comprises providing a storage circuit connected to the second winding.

6. A method according to claim 5 wherein the storage circuit comprises a polarity control block for selectively connecting the energy storage element across the second winding in one of two opposite polarities.

7. A method according to claim 6 wherein the storage circuit comprises a reverse polarity protector connected between the polarity control block and the second winding.

8. A method according to claim 7 wherein the reverse polarity protector comprises a diode.

9. A method according to claim 1 wherein controlling the primary switch and the one or more additional switches comprises closing the one or more additional switches at substantially the same time as opening the primary switch.

10. A method according to claim 1 wherein transferring energy from the inductor to the load comprises connecting the second winding of the inductor to the load.