Analysis and Design of High Step-Up Push-Pull Series-Resonant Converter with ZVS Operation

A push-pull series-resonant converter is studied for high step-up dc-dc voltage conversion, which reduces the inductor current stress by applying the resonant tank to the high-voltage side. However, the push-pull converter suffers from hard-switching and dramatic turn-off voltage spike due to the sudden change of current in leakage inductance. To prevent spike voltage and obtain zero-voltage switching, the excitation inductance and the quality factor are analyzed. A design method is proposed for soft-switching operation, which enables the converter to operate at a fixed frequency with a duty cycle smaller than 0.5. Finally, a 100 kHz 2 k W push-pull series-resonant converter prototype with 27 V dc input and 380 Vdc output is built with 98.3% peak efficiency. The experimental waveforms verify the feasibility of the zero-voltage switching.