Soft-Switched High Step-Up Quasi Z-Source Converter With Low Switch Voltage Stress

In this article, a fully soft-switched high step-up quasi-Z-source (qZs) converter with low switch voltage stress is proposed. In this converter, switched capacitor and coupled inductor techniques are combined with the basic qZs structure to attain high voltage gain and low switch voltage stress. Also, soft switching under zero voltage zero current switching (ZVZCS) condition at turn-on and zero voltage switching (ZVS) at turn-off for the main switch independent of the load range is performed by a ZVT auxiliary circuit. Besides, this circuit improves the voltage gain and switch voltage stress which facilitates using switches with low on-resistance and cost. Also, all diodes turn-off at zero current switching (ZCS) which alleviates the reverse recovery problem. Fully soft switching operation, low elements voltage stress, and proper number of components have contributed to the converter efficiency. Also, common ground and continuous input current have enhanced the converter applicability. The converter is fully analyzed, and the design considerations are provided. To verify the converter operation and theoretical analysis, a converter prototype is implemented at 300 W resulting in 96.5% efficiency.