A new isolated bridgeless PFC converter based on active-clamped SEPIC is proposed. Compared to conventional active-clamped SEPIC PFC converter, the proposed converter reduces conduction loss by removing two diodes in the line current path, while preserving the advantages of the active-clamped SEPIC such as zero-voltage switching (ZVS) and active voltage clamp for all the high frequency switches, soft turn-off of the output diodes and well damped control-to-input-current response. Inaddition, the peak voltage stress on the output diode is inherently clamped by the center-tapped transformer configuration. Exper imental results from a 3.3 kW prototype verified the operation of the converter and demonstrated peak efficiency of 97.26% with 140 kHz switching frequency. The power density of the single-phase PFC module is 101 W/in³.