Patent ID: 8686937

Claim:
A backlight unit, comprising: 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 (LEDs); 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 comparison unit comprises a comparator, a pulse width modulation circuit, a first resistor and a capacitor, wherein the comparator includes an operational amplifier (OP-AMP), wherein the operational amplifier includes an inverting terminal receiving the output current, a non-inverting terminal receiving the reference current, and a second output terminal outputting the control signal by comparing the output current and the reference current, wherein the pulse width modulation circuit includes a PWM terminal receiving a PWM signal, a ground terminal, a second resistor coupled to the PWM terminal, a third resistor coupled to the ground terminal, and a node connecting to the second and third resistors, wherein the PWM terminal is directly connected to the second resistor, wherein the first resistor is coupled between the first output terminal of the array unit and the inverting terminal of the OP-AMP, wherein the capacitor is coupled between the inverting terminal of the OP-AMP and the second output terminal of the OP-AMP and is connected directly to each of the inverting terminal of the OP-AMP and the second output terminal of the OP-AMP, wherein the control unit controls the switching unit, wherein the node of the pulse width modulation circuit is directly connected to the non-inverting terminal of the operational amplifier, and wherein the reference current is generated by the pulse width modulation circuit and applied to the non-inverting terminal of the operational amplifier.