Self-oscillating control of a DC-DC resonant converter using a hysteretic relay

Abstract

The paper presents a technique for analysing and controlling resonant DC-DC converters in a self-oscillating manner. Self-oscillating converters benefit from higher efficiency and higher power density than their non-self-oscillating counterparts since they can be operated closer to the tank resonant frequency. The analysis necessary to predict the behaviour of such converters, based on the construction of Hamel loci, is developed. The impact of parasitic circuit elements is also inherently accommodated. Operation is based on the behaviour of a relay with a negative hysteresis transition. The proposed self-oscillating mechanism is therefore simple and cost effective to implement. Results from a prototype converter are included in order to verify the underlying theoretical principles