A Model for Stability Study of PFC Power Supplies

Typically a power-factor-correction power supply consists of two stages, one responsible for power factor correction and the other for voltage regulation. In this paper, we propose to use a constant power sink to represent the voltage regulating stage, resulting in an analytically tractable model that is able to predict the period-doubled oscillations at line frequency which are not detectable by other conventional models. Using a generalized averaging approach, we investigate the low- frequency dynamics and derive closed-form stability conditions which accurately locate the stability boundaries on selected parameter planes. The model can be conveniently used to evaluate the performance of power-factor-correction power supplies, such as harmonic distortion and power factor. Experimental results are presented to verify the model.