Zero-voltage switching in high frequency power converters using pulse width modulation

A zero-voltage switching technique is described that utilizes a resonant transition during a short but finite switching interval. This zero-voltage resonant-transition (ZVRT) switching technique can be applied to conventional buck, boost, and buck-boost power converter topologies that operate with a constant switching frequency and use pulsewidth modulation for output control. Since frequency-dependent losses are greatly reduced in the power transistors, efficient operation at higher switching frequencies (>1 MHz) is allowed. However, conduction losses are increased because ripple currents are increased and synchronous rectification is required. Experimental results are presented for an interleaved flyback converter that operates with ZVRT switching at 1 MHz