This wake-on-load AC-DC power adapter is a wall mount power supply that converts 100-240 Vac to 5 Vdc at 500 mA for a USB port. The typical application for this type of AC-DC adapter is a cell phone charger. The unique feature of this power adapter is extremely low power consumption when the output is not loaded. The power adapter uses TI’s LM5021 pulse-width modulation controller and has a load detection and shutdown circuit which turns off the PWM integrated circuit at a no load situation. It won’t restart until the output is loaded (wake on load), or the output capacitor is discharged to a certain level. TI designed the start-up circuit to consume less than 40 μA current at high line input during the shutdown period. By doing so, the no-load power consumption of this adapter can be greatly reduced.