Patent ID: 7498754

Claim:
A circuit for driving an array of Light Emitting Diodes (LED) at a constant current comprising: a plurality of LEDs; a plurality of LED drivers, wherein a single LED driver is coupled to each of the plurality of LEDs, each of the plurality of LED drivers has a Pulse width Modulated (PWM) controller; a voltage reference generator for sending a voltage reference signal to each PWM controller, wherein the voltage reference generator is external to each PWM controller; an input line voltage coupled to the voltage reference generator; a clock generator for sending to a clock signal to each of the PWM controllers, wherein the clock generator is external to each PWM controller; and a low-frequency PWM dimming input signal coupled to each PWM controller to allows dimming of the LEDs; wherein each of the plurality of PWM controllers comprises: a comparator having an input coupled to the voltage reference generator and an input coupled to a current sense input; and a switching device having an input coupled to the clock generator, an input coupled to an output of the comparator, an input coupled to the low-frequency PWM dimming input signal, and output of the switching device coupled to an individual LED.