In this study, a single-stage half-bridge flyback converter using a synchronous rectifier (SR) is proposed to achieve unity power factor and higher efficiency. The proposed power factor correction can achieve almost a unity power factor and low input ripple current. The asymmetrical pulse-width modulation (APWM) half-bridge flyback converter operates under zero-voltage switching to reduce switching losses. The conduction loss of the system can be reduced by replacing the diode rectifier with an SR using a low on-resistance metal oxide semiconductor field effect transistor and the SR switch operates under zero-current switching. Detailed analysis is presented on the proposed converter. Experimental results for a 24 V/200 W converter at a constant switching frequency of 100 kHz were obtained to prove the analysis.