A display device includes a display panel having a pixel array and built-in touch sensors, with a shared common electrode, driven between display and touch sensing periods; a display drive circuit outputting image data to the display panel during the display period; a common voltage regulator outputting common voltage data to indicate a common voltage to be applied to the common electrode during the touch sensing period; and a touch sensing circuit decoding the common voltage data during the touch sensing period to vary the common voltage and applying the varied common voltage to the common electrode. The common voltage regulator determines an average value of image data for each line of the pixel array and outputs a first common voltage data to decrease the voltage level of the common voltage when the average value is at or above a preset threshold and corresponds to positive image data.