A backlight assembly device includes lamps, an inverter, a sensing unit, a normal lighting determiner and an inverter controller. The inverter applies a control signal to the lamps to control operation of the lamps. The sensing unit outputs sensing voltages in response to currents flowing in the lamps. The normal lighting determiner compares the sensing voltages to a reference voltage for determining an operating state of the lamps to output a determination signal and varies the reference voltage in response to a change in the operating state of the lamps. The inverter controller outputs the control signal in response to the determination signal.