Efficiency improvement of synchronous buck converter by new passive auxiliary circuit

This paper proposes a zero-voltage-transition (ZVT) pulse width modulated (PWM) synchronous buck converter, which is designed to operate at low voltage and high efficiency typically required for portable systems. A new passive auxiliary circuit that allows the main switch to operate with zero-voltage switching has been incorporated in the conventional PWM synchronous buck converter. The operation principles and a detailed steady-state analysis of the ZVT PWM synchronous converter implemented with the auxiliary circuit are presented. Besides the main switch and all of the semiconductor devices operate under soft switching conditions. Thus, the auxiliary circuit provides a larger overall efficiency. The feasibility of the auxiliary circuit is confirmed by simulation and experimental results.