Nonisolated High Step-Down Converter With ZVS and Low Current Ripples

Abstract

In this paper, a nonisolated high step-down converter is proposed. Energy transfer capacitor and built-in transformer are employed to achieve a very high step-down conversion ratio. Due to the interleaved technique, small values of output inductance can be used, leading to a fast transient response. Furthermore, the use of a coupled inductor reduces inductor current ripples, which implies lower losses. Two main switches and two synchronous rectifiers are used in the converter and all can achieve zero-voltage-switching. As no floating switches are employed, grounded gate drivers and boost strap drivers can be used, avoiding the use of complex isolated gate drivers. In addition, if the switches are shorted, the high input voltage does not appear at the output; thus, the load is protected. A 48 V/1 V 30 A prototype was built, and experimental results are provided to verify the performance of the converter.