High Frequency Dc-dc Converter Design Using Zero Voltage Switching

Resonant mode conversion techniques are used nowadays to improve pulse width modulated dcdc converters. Moreover the quest for ever smaller 50 to 500 watts dc-dc switching supplies has led to the development of circuits that operates in 500 KHz -1 MHz range and above. Since the parasitic elements that normally present in a power circuit can be very significant at this frequency, most of the work is focused on resonant topologies. The topology enables to advantageously employ transformer leakage inductance, MOSFET output capacitance and the MOSFET body diode, to easily move their designs upwards in frequency. The topology offers additional advantages like zero voltage switching at a constant switching frequency, which substantially reduces switching losses. The ability to move upwards in frequency will ultimately reduce the overall size of the power supply. A resonant transition converter is selected for developing a compact 30W power supply for power requirements of an advanced electronic power conditioner. The switching frequency considered is 500kHz for achieving the required power conversion density. At this switching frequency it is possible to take advantage of lead inductances and parasitic capacitance of switching MOSFETs to either eliminate or substantially reduce the resonant tank elements required for achieving a resonant transition conversion to improve efficiency.