Patent ID: 7957160

Claim:
A method of shaping a current waveform for supply to a transformer primary winding, the method comprising: constructing a current waveform that comprises a sequence of current signals of alternating polarity, the constructed waveform having a period corresponding to a fundamental frequency, wherein each current signal is formed within one-half of one period by performing steps comprising: (i) turning on a switch corresponding to a polarity of the current signal being constructed; (ii) increasing a current supplied from an output node from substantially zero to a first current level by discharging a capacitance until the voltage on the capacitance substantially matches a voltage of a first voltage source; (iii) increasing the current from the first current level to a second current level by connecting the output node substantially directly to the voltage source; (iv) turning off the switch once; and, (v) decreasing the current to substantially zero by directing the current that continues to flow after the switch turns off to recharge the capacitance; and, supplying the constructed waveform to a first winding of a transformer.