PS 1-98 : 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.