Flyback Versus Forward Switching Power Supply Topologies For Unipolar Pulsed-Power Applications

We discuss and compare modified flyback and forward switching power converter topologies in applications needing repetitive high-voltage (HV) low duty-cycle rectangular unipolar pulses. The output filters of these two converter topologies are removed, and the needed low duty-cycle operation is used advantageously to generate several kilovolts of pulses using only low-voltage seriesless semiconductors. The two circuits proposed are based on step-up transformers with a constant flux reset clamp that uses the low duty cycle required to reduce the voltage stress on all semiconductor switches. Prototypes were assembled using < 1-kV semiconductor switches to obtain -5-kV output pulses with 5-mus pulsewidth and 10-kHz pulse frequency. Experimental results are presented and discussed. The forward topology was found to be a better choice to deliver HV low duty-cycle unipolar rectangular pulses, and it was tested in a plasma load.