Design and Analysis of an Interleaved Flyback-Forward Boost Converter With the Current Autobalance Characteristic

An interleaved flyback-forward boost converter is proposed in this paper. The switched capacitors are used to realize the controllable voltage source function and balance the currents of the interleaved two phases without an additional current-sharing module. Voltage lift function of the switched capacitor also reduces the turns ratio of the transformers and alleviates the voltage stresses of the output diodes. As the transformers operate in flyback and forward modes alternately, part of the output energy is stored in the switched capacitors; therefore, the size of magnetic components can be reduced. Since the current falling rates of the clamping and output diodes, when they turn off, are controlled by the leakage inductance, the diode reverse-recovery problem is alleviated. Active clamp circuits are applied for the interleaved two phases to recycle the leakage energy and absorb the voltage spikes caused by the leakage inductance. The experimental results based on a 1kW 48 to 380 V dc/dc prototype verify the effectiveness of the theoretical analysis.