Single-stage Bridgeless Buck-boost PFC Converter with DC Split for Low Power LED applications

Abstract

Single-stage power factor correction (PFC) solutions for low power LED applications are facing challenges of how to achieve lower cost, higher efficiency and longer lifetime. Mainly focusing on efficiency improvement, this paper proposes a single-stage bridgeless buck-boost converter with DC split configuration to minimize conduction losses. Secondly, two inductors in the proposed topology are alternately working in discontinuous conduction mode (DCM) when connecting to AC side, and working in continuous conduction mode (CCM) when connecting to DC side. The inductor in CCM helps filter switching frequency ripple, while the inductor in DCM allows the converter to utilize simple single loop control scheme in order to achieve output current regulation and near unity power factor (PF). Thirdly, harmonic injection is applied to further reduce output current ripple. A tradeoff between PF and lower output current ripple is given. Experimental validations are presented with 12.5 W prototypes to verify the theoretical analyses.