Using repetitive control for light load THD and efficiency improvement for boost digital PFC converters

This paper addresses control techniques aimed at improving light load efficiency and reducing total harmonic distortion in digitally controlled boost PFC converters operating over wide load range. A new current sensing scheme is developed to detect the average current under fixed or variable switching frequency operation. An adaptive switching frequency control technique is developed to reduce switching losses and improve efficiency at light loads. A repetitive controller is designed to minimize periodic errors within the current loop bandwidth. A design procedure is given for synthesizing the current loop controller to achieve good current tracking under wide input voltage variation range. A single-phase boost PFC converter with single-chip DSP controller has been constructed for the verification of the proposed control scheme. Simulation and experimental results confirm the feasibility and superior performances of the proposed control scheme.