A backlight unit includes a DC-DC converter that converts a first voltage to a second voltage in response to a driving pulse signal and a driving controller that outputs the driving pulse signal in response to an over-current control signal to control a reference voltage and a level of the second voltage. The driving controller controls the reference voltage in response to the over-current control signal such that the reference voltage increases prior to the second voltage by a predetermined time when the second voltage needs to be increased. In addition, the driving controller controls the reference voltage in response to the over-current control signal when the second voltage needs to be decreased such that the reference voltage decreases later than the second voltage by the predetermined time.