A Novel Robust Control Method for the Series-Parallel Resonant Converter

A novel robust control method for the series-parallel resonant converter (SPRC), which moves the inverter switching point to switch in advance or with lag w.r.t. the rectifier commutation point (RCP), thereby varying the converter gain around the load-independent point, is presented. The converter gain is derived using a novel analytical tool that combines state-plane analysis and superposition with added RCP constraint. Unlike traditional fundamental harmonic analysis [1], the exact gain and frequency expressions for the SPRC at the load-independent point and its neighborhood are obtained with this method. The proposed gain adjustment technique is combined with feedback to form a simple resonant converter controller. This control method is shown to be highly robust to resonant tank parameter uncertainty and circuit/switching delay. It also significantly simplifies the resonant converter controller's design.