A soft-switching post-regulator for multi-outputs dual forward DC/DC converter with tight output voltage regulation

An improved soft-switching post-regulator topology for multi-outputs dual forward DC/DC converter is presented. A delay-trailing modulation method is proposed. ZVSZCS on/zero-current-switching off conditions can be realised on both the primary MOSFETs and the secondary rectifying diodes. Excellent decoupling among different outputs and tight output voltage regulation are achieved. The efficiency is improved due to single power-conversion stage and share in the primary components. The operating principle and main feature of this improved topology are analysed. Key design issue including zero-voltage-switching operation, maximum duty ratio of the primary side MOSFETs and parameter determination for the primary magnetising inductor and the secondary additional redistribution capacitor are discussed. Finally, an experimental prototype with two outputs (300-400 V input, 48 V, 6.5 A and 24 V, 11 A outputs) is built to verify the theoretical analysis. The measured efficiency at normal operation input voltage (400 V) is improved by about 0.5-2%, and the measured efficiency under light loads is improved by more than 2%.