Patent ID: 7663599

Claim:
A driving circuit for a light emitting diode (LED) backlight system, the driving circuit comprising: an input voltage; an input resistor; an operational amplifier having a positive input terminal coupled to the input voltage through the input resistor, a negative input terminal, and an output terminal coupled to the negative input terminal through a feedback network; a first transistor, having a first terminal coupled to the positive input terminal of the operational amplifier, a second terminal coupled to a reference voltage through a reference resistor, and a third terminal coupled to the output terminal of the operational amplifier, for draining a reference current to control an output voltage of the operational amplifier according to the input voltage and the input resistor; and a current calculation unit, coupled to the output terminal of the operational amplifier and the reference voltage, for generating a plurality of working currents proportional to the reference current to drive a plurality of LED strings according to the output voltage of the operational amplifier.