A power control circuit provides a supply voltage, and includes a voltage regulating circuit and a signal selecting circuit. The voltage regulating circuit is coupled to a power supply voltage and the output end of the power control circuit, and receives a first control signal for outputting the supply voltage. The signal selecting circuit has a first input end, a second input end and a third input end. The first input end of the signal selecting circuit receives a first input signal, the second input end of the signal selecting circuit receives a second input signal, and the third input end of the signal selecting circuit receives a second control signal. The first input signal is related to the power supply voltage. One of the first input signal and the second input signal is chosen and outputted as the first control signal according to the second control signal.