High Power Factor Single-Stage Flyback AC-DC Converter with Primary-Side Controlled Adapted to DCM and CCM

In order to achieve the low cost and more compact size, primary side-regulation technology is widely used in low power applications, output voltage can be estimated by an auxiliary winding without secondary-side feedback circuit. For single-stage flyback converter, no algorithm is suitable for both DCM and CCM. In this paper, a novel digital controlled sampling algorithm is proposed for single-stage flyback converter. This scheme uses a midpoint sampling method to estimate auxiliary voltage and current of switch in both discontinuous conduction mode (DCM) and continuous conduction mode (CCM), the control algorithm is implemented with the digital controller to achieve high power factor at 90-264 V rms universal input voltage and output power of 96 W. Experimental results show that the power factor is higher than 0.98 and the output voltage control accuracy and output current accuracy are within 3.5% and 7.5%, the system efficiency is up to 86.7%.