The discontinuous conduction mode Sepic and Cuk power factor preregulators: analysis and design

Sepic and Cuk power converters working as power factor preregulators (PFP) in the discontinuous conduction mode (DCM) present the following desirable characteristics for a PFP: (1) the power converter works as a voltage follower (no current loop is needed); (2) the theoretical power factor is unity; and (3) the input current ripple is defined at the design stage. Besides, input-output galvanic isolation is easily obtained. This paper analyzes the operation of both power converters as DCM-PFP. Design equations are derived, as well as a small-signal model to aid the control loop design. Both simulation and experimental results are presented that are in agreement with the theoretical analysis and complement the work.