The invention relates to a backlight unit and driving method. The backlight unit includes: an array unit, wherein the array unit comprises an input terminal, a first output terminal and an array coupled to the input terminal and coupled to the first output terminal, the array including a plurality of light emitting diodes; a switching unit coupled to the input terminal and coupled to the array; and a comparison unit coupled to the first output terminal and coupled to a control unit and operable to compare a reference current with an output current of the first output terminal; wherein the control unit controls the switching unit.