A Fixed-frequency Series-parallel Resonant Converter with Capacitive Output Filter: Analysis, Design, Simulation, and Experimental Results

In this article, a fixed-frequency phase-shift-controlled full-bridge series-parallel (or LCC-type) resonant converter that uses a capacitive output filter is proposed. Steady-state analysis of this converter is performed by using a complex AC circuit analysis approach. Based on the analysis, a simple design procedure is given and exemplified with a design example of a 200- to 220-V DC input, 300-W, 100-V output converter. The relationship between the design parameters, switch stresses, and converter size is illustrated. Both computer simulation and experimental results on a lab prototype converter are presented to verify the performance of the designed converter for varying input voltage and load conditions. It is shown that this converter requires a narrow variation in pulse width for a wide variation in the load, while the peak current through the switches decreases with the load current. One typical application of this converter is for use as a second stage for AC-to-DC converters.