According to an exemplary embodiment, a display device includes a backlight unit and a display panel. The backlight unit comprises a single light emitting diode string with a plurality of light emitting diodes that are connected to each other in series and configured to emit light. The backlight unit also comprises a detector configured to generate a first voltage and a second voltage with respect to an output voltage for driving the single light emitting diode string, sample the first voltage at a predetermined time interval to generate a sample voltage, and compare a level of the sample voltage with a level of the second voltage to generate a compared result. The display panel is configured to receive light from the backlight unit to display an image. The compared result determines whether the output voltage is applied to the light emitting diode string.