Analysis and optimized design of a new DC-DC converter with asymmetrical voltage distribution for stepping down 1500 V to 48 V

A proposed converter for a particular class of high-voltage applications features an asymmetrical voltage distribution between the primary-side switch pairs, allowing for improved utilization of switching devices and extended soft-switching load range. A hybrid zero-voltage-switching and zero-current-switching (ZVS-ZCS) scheme gives soft-commutations of the two switch pairs from very light load to full load conditions. The properties of the voltage distributions on switch pairs and dc conversion ratio of the converter are explored. The trade-off conditions of soft-switching range, duty-cycle gain with ZCS, current stresses on switching devices, energy circulation and duty-cycle loss due to ZVS are investigated to allow for an optimum design. The theory is verified by a 2 kW, 1500/48 V experimental prototype.