A High-Efficiency AC-to-DC Adaptor with a Low Standby Power Consumption

A two-stage burst mode control scheme for a high-efficiency AC-to-DC adaptor is proposed in this paper. The boost power factor corrector (PFC) is operated at the discontinuous conduction mode (DCM). The half-bridge series-parallel resonant converter (HB-SPRC) is adopted as the DC/DC topology. An upper limit for the output voltage is set to turn off both two control IC´s at either a light load or no load. One lower limit for the output voltage and a delay signal in turn enable the burst modes of the HB-SPRC and the DCM PFC. At light loads, the HB-SPRC provides higher voltage gains to store more energy and to shorten the burst mode period. Thus the no-load or standby power consumption may be reduced. An average active-mode efficiency of 90 % and a 50 mW no-load power loss are observed on a 80 W/12 V prototype adaptor