Analysis of a 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, like 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 dissipative snubber circuits, allows to reduce the circulating current during the active clamp operation, thanks to the resonance involving the transformer leakage inductances and the diode parasitic capacitances. Experimental results taken from a 300W rated prototype are reported, showing a good agreement with the theoretical expectations.