Analysis and design of DCM SEPIC PFC with adjustable output voltage

In this paper, a non-isolated hard switching DCM SEPIC PFC with adjustable output voltage is analyzed and designed. With PWM switching averaged model, DC-DC and PFC operation are discussed first. Then with coupled inductor model, a winding scheme is proposed to control the coupling coefficient of coupled inductors in SEPIC. With carefully designed coupling coefficient, the equivalent input inductance can be implemented with much smaller number of winding turns. For the voltage follower control scheme of DCM PFC, controller and notch filter design are discussed. With the notch filter or the PR controller in another word, THD of the input current can be greatly reduce. The analysis and design are verified by experimental results from a 1kW prototype.