A display device includes a memory, a signal controller, and a voltage generator. A plurality of data is stored in the memory. The signal controller detects a frame rate of an externally applied image data signal, selects data corresponding to the detected frame rate among the plurality of data, and outputs a control signal corresponding to the selected data. The voltage generator includes a DC-DC converter for determining an output voltage in correspondence to the control signal and a feedback circuit for determining a current flowing inside and a frequency of an outputted signal in correspondence to the control signal.