Isolated ZVT boost converter with switched capacitors and coupled inductors

An interleaved and isolated boost converter with switched capacitors is proposed in this paper. The switched capacitors are used to realize the inherent voltage-lift function which increases the voltage gain and reduces the turns ratio of the transformers greatly. Because the transformers can operate in flyback and forward modes which make part of the output energy stored in the switched capacitors, the size of magnetic components can be reduced. Moreover, the load current can be auto-shared by each phase according to capacitor charge balance. 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. Both the main and the clamp switches are ZVT performances during the whole switching transition which reduce the switching losses. 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. The experimental results based on a 1 kW 48 V-to-380 V DC/DC prototype verify the effectiveness of the theoretical analysis.