A backlight inverter includes a transformer boosting an input voltage at a ratio of a primary winding to a secondary winding of the transformer and outputting a first voltage and a second voltage; a protection level signal generator causing a phase delay between the first voltage and the second voltage, and generating a protection level signal, the protection level signal being a sum of the phase reversed first voltage and the second voltage; and an arc state detector comparing the protection level signal with a reference voltage and generating a detection signal; and a diving controller maintaining or stopping a supplying of an input voltage to the transformer in response to the detection signal, wherein in addition to the phase delay, another phase delay is caused by an open circuit in the transformer, so that a maximum value of the protection level signal is larger than the reference voltage and the input voltage is stopped.