Energy based closed form solution of ZCS multiresonant series-parallel converters for optimum design

Under-resonant operation of an ideal multiresonant series-parallel power converter (MRSPC) with a capacitive output filter is modeled. This operation allows zero current switching (ZCS), which is convenient for bipolar devices. The capacitive output filtering reduces the recovery effect of the rectifier diodes and is suitable for high output voltage applications. A closed form solution is found for this converter, based on state space analysis using energy concepts. This approach simplifies the mathematical operations, and gives better physical insight into the system variables. Based on the model, the steady-state characteristics of this converter are derived by a simulation program. They are discussed and compared with those of the series resonant half-bridge power converter (SRHC). The optimum converter parameters are found for given design requirements using computerized optimization routines. Several design examples are presented and compared with SRHC. The validity of the model is verified by SPICE simulations