Variable Saturation Inductor-Based Full Bridge Converter With Wide ZVS Range and Reduced Duty Cycle Loss

A Phase-shifted full-bridge (PSFB) converter is widely used in various applications due to its soft-switching characteristics. However, one of the recognized shortcomings of the PSFB converter is that it cannot simultaneously have a wide soft switching range and a small secondary-side duty cycle loss. The shortcoming hinders the high frequency and high efficiency of the converter. In this paper, the change of the energy demand of the converter on the external series inductor with input voltage and load is analyzed. On this basis, a variable saturation inductor with controllable energy is proposed to meet the energy demand and solve the problem of core heating. The controllable change characteristics of the inductor energy are studied directly instead of the controllable change of the inductance value. By adjusting the inductor energy, the PSFB can not only achieve soft switching under light loads, but also reduce duty cycle loss under heavy loads. Theoretical analysis and experimental verification are carried out on the soft switching and duty cycle loss of the converter. Since the transformer ratio can be increased due to the smaller duty cycle loss. The efficiency of the converter can be further improved.