Single-switch high step-up dc-dc converter with a resonant voltage doubler and low duty ratio

High voltage gain can be easily achieved by utilizing a coupled inductor, but high voltage stresses of switching devices can result from its leakage inductance. Hence, snubber circuits are required to alleviate voltage stresses but these can generally lead to power losses. In this paper, a single-switch high step-up DC-DC converter with a coupled inductor and low duty ratio is proposed. A resonant voltage doubler is integrated to obtain higher voltage gain. Zero-current-switching (ZCS) for the diodes in the voltage doubler is achieved by exploiting resonance of the leakage inductance. Additionally, there is no surge voltage in any of the switching device and this makes dissipative snubber circuits unnecessary. Furthermore, maximum voltage stresses of switching devices are much lower than the output voltage and high voltage gain with low duty ratio can be obtained due to the modified cascade boost structure. All this helps to improve overall power efficiency. The operational principle and characteristics of the proposed converter is provided in detail. Experimental investigation using an output 400V-140W prototype at an input 24V-48V is conducted to verify its functionality.