Predicting ZVS Behavior of Resonant Converters Using a Fast and Effective Calculation

Abstract:
Due to their beneficial soft-switching ability, the class of resonant converters is very attractive for application scenarios requiring high power density and/or superior efficiency. However, by pushing the switching frequency to higher levels, their almost lossless switching instants become critical. Although circuit designers are aware of this fact, serious ZVS investigations including the nonlinear output capacitances of the input MOSFETs are usually left unconsidered during the design phase of resonant converters. This paper proposes two calculation methods allowing fast, but accurate ZVS predictions in the time domain based on a simplified modeling approach.