Patent ID: 8294375

Claim:
A multi channel LED driver, comprising: a plurality of LED strings, each associated with a separate channel; a voltage regulator for generating on output voltage to the plurality of LED strings responsive to an input voltage and a PWM control signal; a first control logic for generating the PWM control signal responsive to a voltage at a bottom of each of the plurality of LED strings; a plurality of dimming circuitries each connected to one of the bottoms of the plurality of LED strings for controlling a light intensity in each of the plurality of LED strings responsive to dimming control signals, wherein the plurality of dimming circuitries further comprise: a switching transistor connected to a bottom of one of the plurality of LED strings; a switch for selectively connecting a reference voltage to a gate of the switching transistor responsive to the dimming control signals; and a second control logic for generating the dimming control signals responsive to forward currents monitored through each of the plurality of LED strings and dimming data, wherein the second control logic further comprises: a third control logic connected to the switching transistor for sensing the forward currents through each of the plurality of LED strings and generating a current ratio for each of the plurality of LED strings responsive to the sensed forward currents; and a fourth control logic for determining a gamma curve for each of the plurality of LED strings responsive to the generated current ratios and for generating the dimming control signals responsive to the determined gamma curves and the dimming data.