Modeling and analysis of fixed frequency phase-shift modulated tertiary-side parallel-tuned resonant DC-DC converter

The authors present a generalized model and analysis of the fixed frequency phase-shift modulated DC/DC resonant power converter with a tuned parallel resonant circuit on the tertiary winding of the high-frequency transformer. A harmonic equivalent circuit model and frequency-domain analysis, which incorporate the effect of the leakage inductance of the high-frequency transformer, are used to develop generalized equations. Steady-state characteristics curves are presented to describe the effect of the leakage inductance and resonant circuit parameters on the performance of the converter. It is shown that, with a tuned parallel resonant circuit on the tertiary winding, the converter can be operated at higher frequency with efficiency higher than 80%. This resonant convertor also provides greater flexibility in selecting the resonant capacitor and an opportunity to integrate the series and parallel inductors with the output transformer. The tuned parallel resonant branch also results in low total harmonic distortion and improved regulation of the converter output voltage