Analysis of a quasi-resonant circuit for soft-switched inverters

This paper presents an analysis of a quasi-resonant circuit for soft-switched inverters. The quasi-resonant circuit provides zero-voltage instants for zero-voltage inverter switching by pulling down the DC link voltage momentarily to zero without increasing the peak value of the nominal DC link voltage. Switches in the quasi-resonant circuit can also be turned off at zero current/voltage condition. The operating principle of this circuit is explained, and the analysis of each operating mode presented. Design criteria for achieving zero voltage switching are derived from the general mathematical analysis. Operation of the circuit has been verified by a PSPICE simulation.<>