A novel resonant snubber based soft-switching inverter

A new soft-switching inverter has been developed to overcome overvoltage and overcurrent problems in the existing resonant link inverters. This inverter employs a single auxiliary switch and a resonant inductor per phase to produce a zero voltage across the main switch so that the main switch can turn on at a lossless condition. Both the auxiliary switch and the resonant inductor are operating at a fractional duty, and thus are small in size compared to the main inverter circuit components. Although the resonance can be obtained with the use of the stray capacitance across the main switch, typical implementations require a small capacitor paralleling with the main switch to obtain nearly lossless turn-off. This paper describes both three-phase and single-phase circuit configurations. Operation modes in a complete zero-voltage switching cycle for the single-phase soft-switching inverter are described in detail with graphical explanation. Because the zero voltage condition is predictable by the selected circuit components, the implementation of this inverter does not require any voltage or current sensors. The circuit operation was first verified by a computer simulation and then further tested with a 1 kW power MOSFET based single-phase inverter. Both simulation and experimental results are presented to show the superiority of the proposed soft-switching inverter