Bus Converter Using Isolation Capacitance for ZVS and Invariant Operation

Many power distribution architectures, including the now-popular “isolated bus” architecture, call for a small and efficient unregulated dc transformer stage. Typical isolated converters can be both small and efficient through high-frequency operation and soft switching, but timing and control can be challenging as switching frequencies increase. We present an isolated bus converter that achieves zero-voltage switching (ZVS) for both inverter and rectifier switches with equal and constant dead times regardless of load, greatly simplifying control. It accomplishes this by using additional capacitors to aid the magnetizing current in commutating switch voltages during the dead time. The converter's operation and advantages are verified with a 1.4-MHz prototype. The converter operates from 36 to 12 V _dcout at up to 36-W rating and achieves > 94.5% peak efficiency with 300-W/in ³ power density.