A power supply switch apparatus includes a voltage decreasing circuit, a rectification circuit, a comparison circuit, and a control circuit. The voltage decreasing circuit receives a first alternating voltage output from a power supply and converts the first alternating voltage to a second alternating voltage. The rectification circuit receives the second alternating voltage and converts the second alternating voltage to a first direct voltage. The voltage regulating circuit receives the first direct voltage and converts the first direct voltage to a second direct voltage. The comparison circuit receives the second direct voltage, compares the second direct voltage with a reference voltage, and outputs a control signal. The control circuit receives the control signal and connects the power supply to different circuits according to the control signal.