Improved integrated boost-flyback high step-up converter

High step-up ratio converters for low-voltage high-current energy sources are nowadays the focus of an intensive research activity by the power electronics community, thanks to the increasing interest for renewable energy sources like those based on photovoltaic modules and fuel-cells. One interesting topology presented in literature is based on the combination of a boost section and a flyback one, featuring the possibility to boost the output voltage while keeping the switch voltage stress at a reasonable level. However, the basic integrated boost-flyback (IBF) topology suffers of parasitic oscillations caused by the transformer leakage inductances and the diode parasitic capacitance. These oscillations require a suitable dissipative clamp circuit to reduce the diode voltage stress, thus adversely affecting the overall converter efficiency. In this paper, a clamping diode is added to the original IBF topology that naturally clamp these parasitic oscillations, and make the converter operation more similar to that of the IBF converter with voltage multiplier. It is also shown that a resonance occurs that helps to increase the converter's voltage gain. Experimental results taken from a 300W rated prototype are included, showing a good agreement with the theoretical expectations.