US Patent 7495875 Power abnormal protection circuit

A power abnormal protection circuit includes a power detection unit, a voltage drop correction unit, a drop out detection unit, a delay unit and a delay masking unit. By detecting an input power average value of a power supply occurring of a brown out condition can be determined. The power supply includes a power factor correction unit which has an output capacitor. By detecting the voltage of the output capacitor a drop out condition can be determined. When a power abnormal condition occurs all units of the power supply can be set off sequentially according to a delay time to protect circuit elements and a connecting computer.