Analysis of reactive power in resonant converters

Abstract

A number of resonant power converters are analyzed to derive the reactive power and RMS current circulating through the transformer. The results of the analysis are used to define design guidelines that minimize the circulating energy in the converters and maximize their efficiencies and power densities. The analyzed converter topologies include the half-bridge zero current switching quasi-resonant converter (HB ZCS-QRC), the half-bridge zero-voltage-switched multiresonant converter (HB ZVS-MRC), the constant-frequency half-bridge zero-voltage-switched multiresonant converter (CF HB ZVS-MRC), the HB ZVS that uses the magnetizing inductance as a resonant element (HB ZVS-MRC (L/sub M/)), and the full-bridge series-parallel-resonant converter (FB SPRC). The results of the analysis show that the HB ZCS-QRC and the soft-switched HB ZVS-MRC (L/sub M/) circulate relatively small amounts of power. However, the circulating power in the HB ZVS-MRC, CF HB ZVS-MRC, and SPRC is found to be considerably larger. The analysis is used to generate sets of characteristics for each converter that can be used in their design optimization based on the minimization of the circulating power.<>