Alternating current power supply voltage abnormity detection device

The utility model discloses an AC power supply voltage abnormity detection device which comprises a current-limiting and voltage-dropping resistor, a single-phase rectifier bridge, a voltage-stabilizing diode, an optocoupler switch and a programmable controller. According to the utility model, a low-voltage calibration value of the alternating-current power supply corresponds to a threshold conduction voltage through setting the amplitude of the conduction threshold voltage of the input end of the optocoupler switch on the sine wave of the alternating current by the analog circuit, and once the low-voltage reduction time of the alternating-current power supply exceeds the standard value, the voltage of the alternating-current power supply is abnormally reduced. The analog quantity change of the alternating voltage is associated into the digital quantity change of cut-off and conduction of the optocoupler switch, so that the detection response speed is greatly improved, and the detected digital quantity can be