Phase-shifted PWM bridge with switchable inductors to maintain zero-voltage switching at light load

摘要

A dc-to-dc pulse-width-modulated phase-shifted full bridge defines two taps, and the bridge switches are operated to produce alternating voltage between the taps. A switchable inductor is connected between each tap and a reference potential. The inductors are switched into circuit during low-load conditions to provide additional energy storage for zero-volt switching (ZVS) of the bridge switches. The switching of the inductors may be by mechanical, solid-state, optical, or magnetic switches. The magnetic switch may be a transformer winding. The switched inductor may be transformer-coupled.