A Novel Single-Stage AC/DC Converter With Integrated Low-Voltage-Stress Active Decoupling Circuit and Reduced Buffer Capacitance

The escalating power demands mandated by the USB PD standard present challenges for existing ac–dc adapters in terms of size, efficiency, and cost. The conventional two-stage solutions cannot meet the requirements due to the necessity of bulky buffer capacitor and high-voltage-stress components. This article proposed a novel single-stage flyback power factor correction (PFC) converter integrated a low-voltage-stress active decoupling cell with reduced buffer capacitance. And a passive and lossless clamp structure is adopted to suppress the voltage spikes in the power switches along with recovering the leakage energy to enhance the efficiency. A novel active power decoupling control algorithm based on volt–second balance is also proposed to achieve precise output regulation and PFC simultaneously under both DCM and CCM operations. A 100-W experimental prototype is built, which achieves a peak efficiency of 93.6%, and reduces 72% volume of the buffer capacitor and reduces 61.5% voltage rating of two active switches compared to the conventional two-stage solution. Experimental evaluations demonstrate the performance of the proposed solution in terms of low cost, high conversion efficiency and power density.