Analysis and design of a parallel resonant converter including the effect of a high-frequency transformer

A high-frequency (HF)-link DC-DC parallel resonant converter (PRC) operating above resonance is analyzed using the state-space approach. The analysis includes the effect of the leakage and magnetizing inductances of the high-frequency transformer. Steady-state solutions are derived and used to obtain the design curves. A method of obtaining an optimum operating point under certain constraints is developed and used as the basis of a simple design procedure. The analysis shows that including an HF transformer introduces a new mode of operation in between the two general steady-state modes. Experimental results obtained with a MOSFET-based PRC for three different transformer turns ratios are presented to support the theory. Efficiencies of about 89% were obtained for 985 W, 115 V, and 230 V output converters, whereas an efficiency of about 86% was obtained for a 15 V, 63 A converter. It was observed that the introduction of the transformer considerably affected the performance, especially in the case of low output voltage and large load current converters