Isolated bi-directional full-bridge soft-switching dc-dc converter with active and passive snubbers

An isolated bi-directional full-bridge soft-switching dc-dc converter with high conversion ratio, high output power, soft start-up and soft-switching capability for battery charging/discharging is proposed in this paper. The use of an active flyback and two passive capacitor-diode snubbers can alleviate the voltage spike caused by the current difference between the leakage inductance of the transformer and the current-fed inductor, can reduce the current spike due to diode reverse recovery, and can reduce current and voltage stresses, while achieving near ZVS and ZCS soft-switching features for the switches on the both sides. It can improve system reliability for high power applications. In the paper, operational principle of the proposed converter will be first described, and analysis and design of the proposed converter is then presented. A 1.5 kW prototype with low-side voltage of 48 V and high-side voltage of 360 V has been implemented, from which experimental results have verified its feasibility.