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 can not meet the requirements due to the necessity of bulky buffer capacitor and high-voltage-stress components. This article proposed a novel single-stage flyback 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 power factor correction (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.