Patent ID: 6898089

Claim:
A converter for producing an alternating voltage output waveform from a high input voltage, the apparatus comprising: a) a bridge circuit having switching assemblies so connected as to define at least two input nodes and two output nodes, the input nodes being operative for receiving the high input voltage across the input nodes, the output nodes being operative for providing a take-off point for the output waveform, each switching assembly comprising at least two high power semiconductor switching devices connected in series between a respective input node and a respective output node to define a respective arm of the bridge circuit, and a capacitor connected in parallel with each of the switching devices in each arm of the bridge circuit; b) a resonant circuit having a resonant frequency and connected across the output nodes; and c) a control circuit for supplying a control waveform to each switching device in the bridge circuit, the control circuit being operative for generating control signals to switch the switching devices of the switching assemblies in each arm between on and off states in a pattern having a period substantially equal to the resonant frequency of the resonant circuit to provide the output waveform across the output nodes with a frequency which is substantially at the resonant frequency, the control circuit being operative for switching each device in the respective arm of the bridge circuit from the on state to the off state for one half cycle of a current in the resonant circuit, and from the off state to the on state for a remaining one half cycle, the switching being performed substantially at the resonant frequency of the resonant circuit.