DESIGN AND DEVELOPMENT OF HIGH FREQUENCY RESONANT TRANSITION CONVERTER

Abstract

The demand for higher switching frequencies in order to achieve higher power conversion densities and efficiencies has made resonant mode conversion [1] techniques to be used nowadays to improve pulse width modulated dc- dc converters which can operate at higher switching frequencies upto 1 MHz. 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 [2] 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 use higher switching frequency will ultimately reduce the overall size of the power supply. A resonant transition converter is selected for developing a compact 30W power supply. The switching frequency considered is 500 kHz 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.