Soft-switching dual forward DC/DC converters employing secondary side control

A soft-switching dual forward DC/DC converter is presented in the paper. A ZVS mechanism on the primary side of transformer is proposed. Namely, primary MOSFETs operate with constant duty ratio and a MOSFET is placed on the secondary side, operating in delay-trailing edge modulation. ZVSZCS is achieved for the primary MOSFETs and ZCS for secondary rectifying diode, independent of load current and input voltage; the total switching losses is reduced and the power conversion efficiency is improved; besides, the proposed converter is very attractive in multi-output applications for post regulation and decoupled outputs without cross-regulation and interaction. First, the operational principle of the proposed converter is analyzed in detail. Then its performance and advantages are evaluated and discussed. Finally, an experimental prototype of 300 V-400 V input, 48 V-6.5 A output was built to verify the theoretical analysis whose maximum efficiency is above 93%.