Implementation of a Parallel. ZVS Forward Converter with Less Power Switches

摘要

A parallel ZVS (Zero Voltage Switching) forward converter is proposed to achieve load current sharing, output ripple current cancellation and conversion efficiency improvement. Two forward converters are connected i n p a r a l l e l t o achieve interleaved PWM operation. Thus the ripple currents on the output side are partially cancelled each other so that the size of output chokes and capacitor is reduced. Only two switches are used in the proposed converter instead of four switches in the conventional parallel ZVS forward converter. Therefore, the proposed converter has less power switching devices. An a c t i v e s n u b b e r i s c o n n e c t e d between two power transformers to absorb the energy stored in the leakage and magnetizing inductances of transformers, to limit voltage stresses across switches, and to realize the ZVS turn-on of all switches. Thus the conversion efficiency is improved by the soft switching operation of switching devices. Finally, the performance of the proposed converter is evaluated on a 480W (24V/20A) laboratory prototype.