Performance evaluations of three-phase current-fed soft switching PWM converter with switched capacitor-type quasi-resonant snubber

A novel prototype topology of a three-phase current-fed PWM converter with a switched capacitor type quasi-resonant snubber is proposed in the paper, which can operate under the principle of zero current switching (ZCS) commutation. However, soft switching performance is affected by output DC current in the proposed quasi-resonant snubber. In particular, PWM current is decreased in the small current region with DC current on the output side, because the charging and discharging period of a switched capacitor increases as the output DC current decreases. The operating performance in the small current region with DC current on the output side, for which performance is problematic in this converter, is investigated in the paper. Further, converter performances from the relationship between soft switching performance and the charging and discharging periods of the switched capacitor are estimated on the basis of the experimental results by a laboratory prototype of this converter.