Stability Analysis of Two-Stage PFC Power Supplies

Power-factor-correction (PFC) power supplies are required to provide high input power factor and tight output voltage regulation. The usual configuration takes a two-stage cascade structure, consisting of a PFC preregulator and a dc/dc converter. Previous studies of the dynamical behaviour mainly focused on the boost PFC preregulator, assuming that it is being terminated by a resistive load. However, in practice, as the PFC preregulator is terminated by a dc/dc converter whose characteristics differ from resistive load´s, the assumption of resistive load termination gives rather inaccurate information about the stability of the system. In this paper we study the complete two-stage PFC power supply and show that the interaction between the PFC stage and the dc/dc converter stage plays an important role in determining the stability of the system