An alternating current load detection circuit comprises a first resistor connected in parallel to a load circuit, a diode full bridge circuit connected in series to the load circuit and the first resistor, a filter capacitor connected in parallel to the diode full bridge circuit, a second resistor, and a photoelectric coupler connected in parallel to the diode full bridge circuit. The photoelectric coupler and the diode full bridge circuit are connected in series and in parallel to the second resistor, respectively. The diode full bridge circuit includes a first diode, a second diode having a positive electrode electrically connected to a negative electrode of the first diode, a third diode having a negative electrode electrically connected to a positive electrode of the first diode, and a fourth diode having a positive electrode electrically connected to a negative electrode of the second diode and a negative electrode electrically connected to a positive electrode of the third diode.