A New Interleaved Active-Clamp Forward Converter with Parallel Input and Series-Parallel Output

A new interleaved active-clamp forward converter with parallel input and series-parallel output is proposed in this paper. With the proposed topology the secondary windings of the transformers work in series when the input voltage is low but in parallel when the input voltage is high. Therefore, the duty cycle is not limited within 0.5 and the steady state conversion gain of the converter can be improved. Accordingly, the current stress and the conduction loss of the primary side are reduced. Interleaved operation can reduce the current ripple in the output capacitor. A prototype with 36-72 input and 12 V/20 A output is built up to verify the theoretical analysis.