A New Zero-Voltage Zero-Current Switching Converter with Minimum Duty Cycle Loss

Zero-voltage zero-current switching (ZVZCS) phase-shifted full-bridge (PSFB) converters have been widely used in high-power applications because of their high efficiency, low price, and easy control. Currently, the biggest problem with PSFB converters in operation is their high duty cycle loss. With the increase in current, duty cycle loss grows and degrades their performance. Focusing on this problem, a new ZVZCS PSFB converter is proposed in this paper. This topology adds an auxiliary circuit to minimize duty cycle loss. Moreover, the lagging-leg switches can obtain zero-current switching (ZCS) easily with the help of the circuit. The auxiliary circuit is built of four metal-oxide-semiconductor field-effect transistors (MOSFETs) and an auxiliary transformer, and extra voltage can be added to the primary coils when the direct-current (DC) voltage is small. This paper discusses its operation principles and characteristics, and an experiment of a 2 kW prototype was conducted, the results of which demonstrate the advantages of the presented circuits.