Patent ID: 7928670

Claim:
A light-emitting diode (LED) driver system for driving a first LED string of one or more LEDs connected in series to each other, the LED driver system comprising: a switching power converter receiving an input DC (direct current) voltage and generating an output DC voltage applied to the first LED string, the switching power converter being switched by a first switch; a second switch connected in series to the first LED string; a first feedback control loop sensing current through the first LED string and controlling on-times or off-times of the second switch at least in part based on the sensed current through the first LED string and a first current reference, the first current reference being a predetermined signal corresponding to a desired brightness of the first LED string; and a second feedback control loop controlling on-times or off-times of the first switch at least in part based on a duty cycle reference and a duty cycle of the on-times and the off-times of the second switch, the duty cycle determined based on the sensed current through the first LED string and the first current reference corresponding to the desired brightness of the first LED string.