High Step-Up Ratio Flyback Converter With Active Clamp and Voltage Multiplier

In this paper, an isolated high step-up ratio dc-dc converter aimed to be used in interface systems between low-voltage renewable energy sources, such as photovoltaic panels and fuel cells and the utility grid, is presented. The converter is based on the active clamp flyback topology with a voltage multiplier at the transformer secondary side. Such configuration, while naturally clamping the rectifier diode voltages thus avoiding the use of dis-sipative snubber circuits, allows the reduction of the circulating current during the active clamp operation due to the resonance involving the transformer leakage inductances and the diode parasitic capacitances. Experimental results taken from a 300-W-rated prototype are reported, showing the absence of parasitic oscillations after diodes and switch transitions and high efficiency, in agreement with the theoretical expectations.