Patent ID: 8278830

Claim:
An LED driver controller, comprising: a voltage regulator for controlling an output voltage to a top of a plurality of LED strings responsive to at least a reference voltage; a first circuitry associated with a first node at a bottom of a first LED string of the plurality of LED strings for comparing a voltage at the bottom of the first LED string with a high reference voltage and a low reference voltage; a second circuitry associated with a second node at a bottom of a second LED string of the plurality of LED strings for comparing a voltage at the bottom of second LED string with a high reference voltage and a low reference voltage; control logic for generating a first control signal when the voltage of at least one node at the bottom of one of the plurality of LED strings falls below the low reference voltage and for generating a second control signal when the voltage at the bottom of each node of the plurality of LED strings exceeds the high reference voltage; second circuitry responsive to the first control signal and the second control signal for generating the reference voltage; and wherein the second circuitry controls the reference voltage to cause the voltage at the bottom of a lowest voltage node of the plurality of LED strings to remain between the high reference voltage and the low reference voltage.