A backlight unit includes: a light source configured to emit light based on a driving current; and a backlight controller receiving a digital dimming signal that defines a length of an output period of the driving current from a pulse width modulator and configured to, when a duty ratio of the driving current is less than a reference duty ratio, modulates the duty ratio of the driving current so that the duty ratio of the driving current is equal to or greater than the reference duty ratio and decrease a duty ratio of the digital dimming signal.