Non-isolated high-step-up soft switching DC/DC converter with low-voltage stress

A non-isolated high-step-up soft switching DC/DC converter with low-voltage stress is developed for large conversion ratio applications, which combines a synchronous boost converter and a flyback converter with voltage multiplier in this study. The circuit structure is simplified by integrating the boost inductor and flyback transformer into a coupled inductor and sharing the switch. The voltage stresses of all the power devices are low, thus low-voltage-rated power devices can be adopted to reduce conduction losses. All of the switches operate under zero-voltage turn-on condition, thus the switching losses are reduced. Moreover, the reverse-recovery problem of the diodes is alleviated because the decreasing rate of the diode current is limited by the leakage inductance of the coupled inductor. Additionally, the utilisation rate of the coupled inductor is improved because the coupled inductor transfers energy during the whole switching period. Finally, a 250 W prototype is built and the experimental results are provided to verify the accuracy of the theoretical analysis, and the highest measured efficiency is about 96.6%.