An Adaptive Energy Storage Technique for Efficiency Improvement of Single Stage Three-Level Resonant AC/DC Converters

This paper presents an efficiency improvement method for single-stage PFC converters operating with variable frequency asymmetrical pulse width modulation. A load adaptive energy storage technique is proposed to guarantee the converter operation near its maximum efficiency point for a wide range of loading. This leads to almost constant converter efficiency from full load to 40% load. The use of interleaved converters is also proposed to extend the constant efficiency range of operation to lighter loads. Analytical, simulation and experimental results are presented to verify the proposed methods.