Embodiments relate to a display device and a method of operating the display device. The display device includes a power supply circuit configured to generate a gate voltage at an output terminal of the power supply circuit based on an input voltage to supply the gate signal to the pixels of the panel. The display device generates a switching pulse signal for a predetermined time period after the input voltage dropping below the predetermined threshold voltage. The display device generates the gate voltage at a first voltage level responsive to the switching pulse signal, the gate voltage at the first voltage level higher than the gate voltage at a second voltage level absent the switching pulse signal. Charges stored in pixels are discharged by applying the gate voltage to the pixels through gate lines, responsive to the input voltage dropping below the predetermined threshold voltage.