A switch mode power supply (SMPS) is capable of reducing standby power consumption, and includes a power factor capacitor (PFC) bulk capacitor which supplies power in a standby mode to constant loads by repeatedly charging and discharging a voltage, a PFC controller which controls the voltage to be charged in the PFC bulk capacitor, a first resistor and a second resistor which divide the voltage of the PFC bulk capacitor and output a reference voltage, and a control unit which controls the charging and discharging of the voltage of the PFC bulk capacitor in accordance with the reference voltage.