An Investigation on Zero-Voltage-Switching Condition in Synchronous-Conduction-Mode Buck Converter

A buck converter operated in synchronous - conduction-mode (SCM) can obtain zero-voltage-switching (ZVS) of both switches without any auxiliary components, which is beneficial for high-switching frequency operation. To obtain ZVS of high-side switch, buck converter requires adequate dead-time duration and reverse inductor current. Through the law of conservation of energy, minimum reverse inductor current required for ZVS can be calculated accurately by a modified method. On top of the modified method, a ZVS model based on resonance is proposed in this paper. The proposed method also leads to accurate ZVS condition but with more information within the transition. The principle and application of the proposed resonant model are interpreted by a comparative example. Moreover, simulation waveforms and hardware testing results of a 1 MHz/30 W SCM buck converter prototype are presented for verification.