The invention provides a conversion circuit for converting input voltage into output voltage, including: a full-bridge rectifier circuit including first and second bridge arms connected in parallel and electrically connected between first and second ends of the output voltage; a first switch branch electrically connected between the first end of the input voltage and the first end of the output voltage, and including first and second switches connected in series to form a first connection node; a first resonant unit electrically connected between the first connection point and midpoint of the first bridge arm; and a first transformer including a first primary winding connected in series with the first resonant unit; and a first secondary winding connected between midpoint of the first bridge arm and midpoint of the second bridge arm. The conversion circuit of the invention improves conversion efficiency while maintaining smaller voltage stress on switches.