Design of a Two-Stage AC/DC Converter with Standby Power Losses Less than 1 W

The objective of this paper is to design and implement an AC/DC converter which meets the green power specification under standby condition. The design of PFC-OFF control and auxiliary circuit which will significantly reduce the standby power to meet the energy code under standby condition will be presented. Moreover, it will be shown that these circuits don't need any current sensor and hysteresis circuit to detect the load condition, which can reduce the cost and avoid false activation caused by current noise. The specifications of converter are as follows: universal input voltage: AC 90-265 V, 50-60 Hz; output voltage: 19V/DC; output power: 250W; standby power: input power < 1 W @ 265 V/AC input. Experimental results have demonstrated that the input power factor is greater than 98% in the whole voltage range and full load condition. The power consumption under standby condition is less than 1 W confirming the design and implementation.