Sepic andĆuk converters working as power factor preregulators (PFP) in discontinuous conduction mode (DCM) present the following desirable characteristics for a PFP: 1) the converter works as a voltage follower (no current loop is needed); 2) 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 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.
Index Terms-AC-DC power conversion, filtering, power supplies.
NOMENCLATUREFreewheeling current. and currents. Conduction parameter; critical conduction parameter. Output-to-peak-input ratio; transformer turn ratio. ON time of the output diode ( ); ON time of the switch ( ). OFF time of both switch and output diode. Switching period. Input voltage and current; rectified input voltage and current. Ouput voltage and current.
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