A switching mode power supply includes an EMI filter unit, a PFC unit, a DC/DC unit, a PFC controller including a feedback stage to which a link voltage at an output side of the PFC unit is fed back and an overvoltage protection stage, a DC/DC controller generating a burst mode operation signal in a light-load or no-load condition, an error signal generation unit for sensing an output voltage of the power supply to generate an error signal, and a control unit for enabling the PFC unit to operate in a burst mode by connecting the overvoltage protection stage and the feedback stage. When the error signal is smaller than a predetermined value, the DC/DC controller generates the burst mode operation signal. When the link voltage fed back to the feedback stage exceeds a threshold voltage of the overvoltage protection stage, the PFC controller deactivates the PFC unit.