Design and Simulation of New High Step-Up Full Bridge Converter With Extended ZVS Range for High-Voltage Applications

A new four-switch converter has been presented in this paper which contains a full-bridge and an extra half-bridge structure. Two voltage multiplier cells are applied to the secondary sides of transformers in order to increase voltage gain, so the converter is suitable for boosting applications. Two transformers are used in this structure, so it is able to transfer high power and voltage gain is increased by serial connection of the output voltage multiplier cells. ZVS is achieved for all switches from approximately no load to full load. ZCS of secondary side diodes of the LLC circuit can be achieved by adjusting the resonant frequency. Furthermore, current stress of the output diodes of full bridge part is decreased with respect to linear operation, so the converter is able to be used for high-voltage applications such as electron beam welding (EBW). In high-voltage applications, the transformer suffers from insulation problems and higher turns ratio is restricted because of increase in leakage inductor of the transformer that leads to decrease in voltage gain. Since the output of voltage multiplier cells are connected in series, so for a specific output voltage, turns ratio of the transformers would be smaller than a single transformer in conventional PSFB converter, so voltage of the secondary side of transformers is reduced that leads to lower insulation problems and higher output voltage is achieved easier.

Keywords:

phase shifted full bridge , voltage multiplier cell , electron beam welding , quasi resonant converter , high stepup