An apparatus for driving a light emitting diode - hereafter abbreviated LED - array to provide a backlight for a liquid crystal display - hereafter abbreviated LCD - device, the apparatus comprising: a current amount setter , wherein a resistance across the current amount setter is variable according to a selection signal from an external system so as to vary a voltage at a node or a current in the node of the current amount setter ; and a controller coupled to the current amount setter and the LED array , the controller comprising: a power supplier connected to the node of the current amount setter and configured to either: detect the voltage at the node and adjust a level of current provided to the LED array based on an input voltage (VIN) received from the external system and the voltage at the node ; or detect the current in the node and adjust a level of current provided to the LED array based on the the current in the node of the current amount setter , a plurality of switching transistors coupled to the LED array to turn on or off LEDs in the LED array , and a DC signal supplier configured to send direct current - hereafter abbreviated DC - signals remaining unchanged during a frame cycle of the LCD device to the plurality of switching transistors , wherein the plurality of switching transistors are configured to receive the DC signals from the DC signal supplier at their respective control terminals and be turned on in response to the DC signals to turn on the LEDs . a current amount setter , wherein a resistance across the current amount setter is variable according to a selection signal from an external system so as to vary a voltage at a node or a current in the node of the current amount setter ; and a controller coupled to the current amount setter and the LED array , the controller comprising: a power supplier connected to the node of the current amount setter and configured to either: detect the voltage at the node and adjust a level of current provided to the LED array based on an input voltage (VIN) received from the external system and the voltage at the node ; or detect the current in the node and adjust a level of current provided to the LED array based on the the current in the node of the current amount setter , a plurality of switching transistors coupled to the LED array to turn on or off LEDs in the LED array , and a DC signal supplier configured to send direct current - hereafter abbreviated DC - signals remaining unchanged during a frame cycle of the LCD device to the plurality of switching transistors , wherein the plurality of switching transistors are configured to receive the DC signals from the DC signal supplier at their respective control terminals and be turned on in response to the DC signals to turn on the LEDs . a power supplier connected to the node of the current amount setter and configured to either: detect the voltage at the node and adjust a level of current provided to the LED array based on an input voltage (VIN) received from the external system and the voltage at the node ; or detect the current in the node and adjust a level of current provided to the LED array based on the the current in the node of the current amount setter , a plurality of switching transistors coupled to the LED array to turn on or off LEDs in the LED array , and a DC signal supplier configured to send direct current - hereafter abbreviated DC - signals remaining unchanged during a frame cycle of the LCD device to the plurality of switching transistors , wherein the plurality of switching transistors are configured to receive the DC signals from the DC signal supplier at their respective control terminals and be turned on in response to the DC signals to turn on the LEDs . <EOS>