Forward-flyback resonant converter for high-efficient medium-power photovoltaic applications

In this paper, a quasi-resonant forward-flyback converter is proposed for photovoltaic power system. Since the output of forward-flyback converter is connected in series, the proposed circuit offers high-step up conversion. The quasi-resonant forward circuit that consists of a transformer leakage inductance and a resonant capacitor generates almost sinusoidal currents during the switch on-time so the primary switching stress has been significantly reduced. The flyback circuit transfers the energy stored in the magnetizing inductance to the load during the switch off-time. Design guidelines of the circuit parameters are presented. To verify the proposed circuit design, a 400-W experimental prototype has been designed, fabricated, and tested. Simulation and experimental results verify the effectiveness of the proposed circuit design.