An Adaptive Dead Time Prediction Method for Primary-Side Regulation Active-Clamp Flyback Converter

Active-clamp flyback converter is widely used in small power applications as soft-switching technique could be realized with higher frequency and lower volume. Too long or too short dead time between the control signals of the two switches will reduce the stability and improve the switching loss. To improve the performance of the soft-switching technique and eliminate the opto-coupler, an adaptive dead time prediction method is proposed for primary-side regulation active-clamp (PSRAC) flyback converter. The ideal dead time is predicted based on the voltage of the clamp capacitor and part rising time of the drain-to-source voltage. The voltage of the clamp capacitor is predicted based on the control parameters and primary parameters. Part rising time is predicted based on the comparison between the auxiliary winding voltage and zero voltage. The proposed control was verified in a digital controlled PSRAC flyback converter. Proper and adaptive dead time control was realized.