Fast-scale bifurcation in single-stage PFC power supplies operating with DCM boost stage and CCM forward stage

This paper describes the fast-scale bifurcation phenomena of a single-stage single-switch power-factor-correction (PFC) regulator comprising a boost stage operating in discontinuous conduction mode (DCM) and a forward stage operating in continuous conduction mode (CCM). The two stages combine into a single stage by sharing one main switch and one control loop. Using 'exact' cycle-by-cycle computer simulations, the effects of various circuit parameters on fast-scale instabilities are studied. The results are qualitatively verified by experimental measurements. This work provides a clear picture of how the variation of certain practical parameters can render such a circuit fast-scale unstable.