Novel alternating current power supply monitoring device

The invention discloses a novel alternating current power supply monitoring device, which can perform power down and phase failure monitoring of single-phase and three-phase alternating current input power supplies on single-phase and three-phase alternating current power supplies. The alternating current power supply monitoring device comprises a first current limiting part used for limiting the current of an input power supply, a rectifying part used for rectifying AC voltage, a second current limiting part used for limiting the current of the rectified input power supply again, a monitoring signal output part used for outputting AC through an optical coupler and a signal processing part for accomplishing optical coupler output signal monitoring through an MCU. Through one monitoring signal, the novel alternating current power supply monitoring device can achieve the function of monitoring power down and phase failure of single-phase and three-phase alternating current input power supplies with extremely low cost and high reliability.