Phase-shifted PWM full-bridge dc-dc converters for automotive applications: Reduction of ringing voltages

This paper analyzes two solutions for ringing voltage problems occurring in the output voltage of a Zero-Voltage and Zero-Current Switching Phase-Shifted PulseWidth Modulation Full-Bridge de-de converter intended for automotive applications. An RCD snubber and an active snubber (thereafter called "modifled flyback converter" since it includes a flyback converter to provide an additional power supply) are designed to reduce the ringing voltage caused by mainly the interaction among the transformer leakage inductance and circuit parasitic capacitances. This converter with the RCD snubber and the modified flyback converter has efficiencies of 91% and 92%, respectively, at 42-V 1-kW full load. The converter without any snubber has a lower efficiency of 88.7%. Experimental and simulation results are shown to complement the theoretical analysis.