A power output circuit includes a charge pump, a voltage regulator, a clock generator and a voltage detector. The charge pump is used for receiving a clock signal having an operating frequency and outputting an output voltage. The voltage regulator, coupled to the charge pump, is used for outputting a control voltage to the charge pump, to control the output voltage. The clock generator, coupled to the charge pump, is used for outputting the clock signal to the charge pump. The voltage detector, coupled to the clock generator and the voltage regulator, is used for detecting the control voltage and controlling the clock generator to adjust the operating frequency of the clock signal according to a magnitude of the control voltage.