Coupled-inductor boost integrated flyback converter with high-voltage gain and ripple-free input current

DC-DC converters with high-voltage gain and low-input current ripple have attracted much attention in photovoltaic, fuel cells and other renewable energy system applications. Conventional boost-flyback converter can achieve high-voltage set-up ratio; however, its input current is pulsing and the voltage stress across output diode of flyback-cell is high. In this study, by incorporating coupled-inductor into the boost-cell of boost-flyback converter, the voltage stress across the output diode is effectively reduced. Passive snubber circuit is utilised to suppress the voltage spike across power switch, low-voltage-rated metal-oxide semiconductor field effect transistor (MOSFET) with low R_{ds_on} can thus be used to reduce the conduction loss of power MOSFET. In addition, ripple-free input current can be achieved, which makes the design of electromagnetic interference filter easy. Steady-state characteristics of the proposed converter are analysed, and experimental results are given to verify the analysis results.