Novel circuit design for two-stage AC/DC converter to meet standby power regulations

The objective of this study is to design and implement an AC/DC converter in order to meet the standby power specification. The design of auxiliary circuit (including start-up circuit) and power factor correction (PFC)-OFF control which significantly reduces the standby power to meet the energy code under standby condition will be presented. Moreover, it will be shown that these circuits do not 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 the converter are as follows: universal input voltage: 90-265 V_AC, 50-60 Hz; output voltage: 19 V_DC; output power: 250 W; standby power: input power 1 W at 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 the specified value, 1 W, confirming the design and implementation.