Dynamic Modelling of The Series Resonant Converter Operating in Discontinous Conduction Mode And its Application in Space

Abstract

The Series Resonant Full Bridge operating in Discontinuous Conduction Mode (DCM) at fixed frequency, SRFB-DCM, is an interesting topology to provide isolation in the interface to main buses while having high efficiency thanks to Zero Voltage Switching (ZVS) and Zero Current Switching (ZCS). As this converter cannot be regulated, usually, it is more interesting for regulated buses or in case there is post-regulation. This converter finds application in Power Processing Units for Electrical Propulsion and in any secondary high power front-end converter. Despite its simple design without regulation, in general, the dynamic behaviour of resonant converters is difficult to predict. A model is necessary to predict compatibility with input and output interfaces (stability, output impedance, start-up in-rush,…), avoiding late discovery of oscillations, for example. This paper presents a method to obtain the theoretical dynamic model of the SRFB-DCM with fixed frequency and duty cycle which seems easier to understand but surprisingly not treated in literature. Results are contrasted with simulations.