Designing for zero-voltage switching in phase-modulated series resonant converters

Abstract

Achieving soft switching in switched-n1ode power supplies is an important design criterion today. Converters like theseries-loaded resonant topologies are preferred because they easily enable soft switching. However, the soft switchingrange is limited and depends on a number of panuneters that are not directly under the designer's control. Special designrules are used to arrive at the optin1u1n operating points and thus maintain soft switching over at least a 1najorportion of the operating range. This paper deals \Vith the design issues relevant to achieve zero-voltage switching(ZVS) for the phase-rnodulated series resonant converter. The ZVS mechanisn1 and the modes of operation for whichthe converter inherently offers ZVS are explained. A circuit modification to extend the ZVS range beyond the naturalrange of the converter is introduced. Further, the design procedure for achieving ZVS is discussed through a designexample. A phase-n1odulated series resonant converter for high-voltage DC applications is designed and experimentallyshown to have ZVS over its entire specified operating range