A display device includes pixel circuits with light emitting devices coupled to a first voltage and a second voltage; a signal controller configured to: generate output image data by gamma converting and by decreasing input image data of a frame according to a gamma curve; and generate a control signal to display an image on the panel according to the generated output image data; a voltage difference setting unit configured to detect a maximum value in the output image data, and configured to calculate a difference value between the first voltage and the second voltage so that a driving current corresponding to the maximum value is generated; and a power supply unit configured to generate and apply the first and second voltages to the panel, the generated first and second voltages corresponding to the calculated difference value, wherein the gamma curve comprises one or more inflection points.