Patent ID: 9491822
Filing Date: 2016-11-08
CPC Classification: H05B,Y02B

Claim Text:
1. A multi-channel LED driver, comprising: a plurality of linear current regulators, each linear current regulator connected to a bottom of a corresponding string of a plurality of strings of series connected LEDs of a multi-channel LED array, for controlling a bias current in the corresponding sting of the series connected LEDs responsive to an LED bias reference voltage; and a dynamic headroom regulation voltage control circuit monitoring a plurality of headroom regulation voltage at a plurality of bottoms of the plurality of strings of the series connected LEDs of the multi-channel LED and for generating a reference voltage controlling the plurality of headroom regulation voltages responsive to the LED bias reference voltage, the dynamic headroom regulation voltage control circuit comprising: first control logic configured to determine a minimum headroom regulation voltage from the monitored plurality of headroom regulation voltages; and second control logic including a first comparator, a second comparator, and an input offset current source coupled to at least one of the first comparator and the second comparator, wherein the second control logic is configured to compare the minimum headroom regulation voltage with a high load dependent threshold voltage and a low load dependent threshold voltage and vary the high load dependent threshold voltage and the low load dependent threshold voltage directly proportionally with the LED bias reference voltage, the first comparator is configured to generate a first control signal to increase the reference voltage responsive to the minimum headroom regulation voltage falling below the low load dependent threshold voltage and the second comparator is configured to generate a second control signal to decrease the reference voltage responsive to the minimum headroom regulation voltage exceeding the high load dependent threshold voltage.