Patent ID: 7835164

Claim:
An apparatus for supplying AC power to a high voltage device comprising: a first input port adapted to be coupled to a high frequency switching signal; a second input port adapted to be coupled to a low frequency pulse width modulation signal; a combining circuit, which is operative to combine, said high frequency switching signal with said low frequency pulse width modulation signal, to produce a composite signal; a first switching circuit coupled to a first portion of a primary winding of a transformer, said transformer having a secondary winding coupled to said high voltage device, said first switching circuit being operative to controllably switch a first current through said primary winding in accordance with first transitions in said composite signal; a second switching circuit coupled to a second portion of said primary winding of said transformer, said second switching circuit being operative to controllably switch a second current through said primary winding in accordance with second transitions in said composite signal; and wherein said first switching circuit is operative to controllably interrupt said first current, in accordance with a prescribed relationship between a first voltage, representative of said first current, and a second voltage representative of a difference between a third voltage representative of current through said secondary winding and a fourth voltage representative of a DC component of said low frequency pulse width modulation signal.