Fan loop disconnection monitoring circuit

The utility model discloses a fan loop disconnection monitoring circuit which comprises a loop signal input circuit, a comparison adjusting circuit, a logic judgment circuit and a disconnection alarmcircuit, and the loop signal input circuit is composed of a current transformer CT1, a voltage clamping diode D1, a voltage clamping diode D2 and an input optocoupler OP1; the comparison adjusting circuit is composed of a voltage comparator LM393, an adjustable potentiometer W1 and a filter capacitor E1. The logic judgment circuit is composed of an exclusive-OR gate circuit 74LS86; the disconnection alarm circuit is composed of a driving optocoupler OP2 and an alarm relay Relay 1. According to the fan loop broken line monitoring circuit, an operational amplifier, an AD sampling chip and a logic control device are omitted, the fan loop broken line monitoring circuit can be achieved only through simple devices such as a current transformer, a diode, a potentiometer and a voltage comparator,and meanwhile the fan loop