A DC-DC Full-Bridge Hybrid Series Resonant Converter enabling constant switching frequency across wide load range

Abstract

This paper describes a DC-DC Full-Bridge Hybrid Series Resonant Converter (FB-HSRC) that enables constant switching frequency across a wide load range. Compared to most resonant converters, this converter has the advantage of constant frequency operation while maintaining ZVS on and off. Power is controlled with pulse width instead of frequency modulation. This enables filters to be optimised at the constant switching frequency instead of at the worst-case frequency hence reducing the sizes of the passive components in the converter. The FB-HSRC is topologically similar to the Partial Series Resonant Converter (PSRC) [6] but with two additional switches connected in parallel to each of its resonant capacitors in its switchless phase arm. At minimum load, the converter behaves like the PSRC with its resonant capacitors and series inductor contributing to power transfer. As load increases, these resonant capacitors also concurrently serve as ZVS turn off commutation capacitors for the switches during the resonant phase. Voltage and current waveforms are simulated with steady-state models of the operation modes. The converter efficiencies at various loads are calculated with the loss model obtained. Finally, a converter prototype is built for an output load range of 13 W to 100 W operating at a frequency of 100 kHz. Experimental results are obtained and are then compared against the simulations results and efficiency calculations.