Dual Interleaved Active-Clamp Forward With Automatic Charge Balance Regulation for High Input Voltage Application

This paper proposes a new dual interleaved active-clamp forward topology suitable for high input voltage and high-density application. Two interleaved forward circuits are connected in series on the primary side and in parallel on the secondary side. Therefore, only two high-voltage MOSFETs are needed for the primary switches. Also, the two interleaved parts utilize auxiliary windings to share one capacitor to fulfill active-clamp. Charge balance of the two channels is, thus, regulated by the shared clamping capacitor without demand for extra control schemes. Through the resonance between the magnetizing inductors and the equivalent capacitors of the switches during the transition time, switching loss of the primary switches can be reduced. Interleaved operation reduces the size of the output filter inductor. Based on detailed analysis, a prototype with 220-400-V input and 5-V/30-A output is built. Experimental results verify the performance of the new topology.