A three-phase ZVS PWM DC/DC converter with asymmetrical duty cycle for high power applications

This paper proposes the application of the asymmetrical duty cycle to the three-phase dc/dc PWM isolated converter. Thus soft commutation is achieved for a wide load range using the leakage inductance of the transformer and the intrinsic capacitance of the switches, as no additional semiconductor devices are needed. The resulting topology is characterized by an increase in the input current and output current frequency, by a factor of three compared to the Full Bridge converter, which reduces the filters size. In addition, the rms current through the power components is lower, implying an improved thermal distribution of the losses. Besides, the three-phase transformer allows the reduction of the core size. In this paper, a mathematical analysis, the main waveforms, a design procedure as well as simulation and experimental results obtained in a prototype of 6kW are presented.