Zero-voltage-switching buck converter with low-voltage stress using coupled inductor

This study presents a new zero-voltage-switching (ZVS) buck converter. The proposed converter utilises a coupled inductor to implement the output filter inductor as well as the auxiliary inductor which is commonly employed to realise ZVS for switches. Additional magnetic core for the auxiliary inductor in traditional ZVS converters is eliminated and hence reduced cost is achieved. Moreover, thanks to the series connection between the input and output, the switch voltage stress in the steady state is reduced and thus the ZVS operation can be easier achieved. Then the leakage inductor current circulating in the auxiliary switch is decreased, contributing to reduced conduction losses. In particular, low-voltage rating devices with low on-state resistance can be adopted to further improve efficiency in applications with non-zero output voltage all the time, such as the battery charger. Furthermore, the reverse-recovery problem of the diode is significantly alleviated by the leakage inductor of coupled inductor. In the study, operation principle and steady-state analysis of the proposed converter are presented in detail. Meanwhile, design considerations are given to obtain circuit parameters. Finally, simulations and experiments on a 200 W prototype circuit validate the advantages and effectiveness of the proposed converter.