Fully Soft-Switched Ultra-High Step-Up Converter With Very Low Switch Voltage Stress

In this article, a fully soft-switched ultra-high-voltage gain converter with very low switch voltage stress is presented. To achieve ultra-high-voltage gain and very low switch voltage stress, two phases of a high step-up boost converter based on coupled inductors and switched capacitors are combined. In this converter, the main and auxiliary switches operate at zero-voltage switching (ZVS) and all diodes turn-off at zero-current switching (ZCS). Thus, the reverse recovery problem of the diodes and the switching loss for all the semiconductor devices are mitigated. In addition, given that the voltage stress across the switches is remarkably low, mosfets with low drain-source resistance (RDS-on) can be utilized to substantially lower the conduction loss. Hence, all the mentioned advantages have contributed to the converter efficiency improvement. Also, the existence of the common ground between the input and the output expands the converter applicability and reduces the control circuit complexity. Finally, a 300 W laboratory prototype is implemented to verify the theoretical analysis and a comprehensive comparison with counterpart structures is presented to illustrate the advantages and disadvantages of the presented converter.