Photoelectric conversion defrost control system

The utility model discloses a system for achieving defrost control to an air source heat pump unit, a heat pump type room air conditioner and the like by utilizing a photoelectric conversion principle. The utility model adopts the technical scheme that photoelectric sensors which respectively comprises a transmitter and a receive are arranged on two sides of the surface of a heat exchanger for a refrigerating device for defrost; a current source is connected with the transmitter and used for inputting current for the transmitter; the receiver is used for receiving an optical signal transmitted by the transmitter and converting the optical signal into a voltage signal; a voltage signal acquisition instrument is connected with a receiver and used for receiving a voltage signal converted by the voltage signal acquisition instrument; and a defrost controller is used for starting or stopping defrost operation according to the voltage signal obtained by the voltage signal acquisition instrument. The defrost operati