A multiple-phase power circuit includes multiple voltage conversion units, a pulse-width modulation (PWM) signal generator and a surge detection circuit. Each voltage conversion unit converts an input voltage to a driving voltage of a pre-set phase. The pulse-width modulation (PWM) signal generator is coupled to the voltage conversion units to output PWM signals of different phases to the voltage conversion units. The surge detection circuit samples the input voltage and compares the input voltage with a reference voltage. Then the surge detection circuit outputs multiple first control signals. The PWM signal generator further stops outputting the PWM signals of different phases when the PWM signal generator receives the multiple first control signals.