Fully Soft-switched Non-isolated High Step-down DC/DC Converter with Minimum Component Count

A fully soft-switched high step-down converter with minimum number of passive and active components is presented in this paper, which is suitable for non-isolated DC/DC applications. High voltage conversion ratio is achieved by a pair of coupled inductors while zero voltage switching condition for the main switch along with zero current switching condition for the main diode at turn-off are provided by adding only an auxiliary active switch and a coupled inductor to the basic buck converter. Thus, the converter is optimum in terms of component count among the soft-switched high step-down converters. The mentioned converter advantages have contributed to the realization of high efficiency. To confirm the theoretical operation and analysis of the converter, a laboratory prototype circuit is implemented for 155-to-24V at 100W and 100kHz.