Patent ID: 7733034

Claim:
A light emitting diode (LED) circuit, comprising: a plurality of LED strings connected in parallel with each other, each LED string including a plurality of component LEDs connected in series; a minimum voltage selector circuit configured to select the LED string with the largest voltage drop across its terminals, and output a minimum voltage associated with said selected LED string with said largest voltage drop; a voltage control loop configured to receive said minimum voltage from said minimum voltage selector, said voltage control loop configured to generate a linearly-variable output voltage varied by said minimum voltage and sufficient to drive said plurality of LED strings; and a plurality of current regulation loops, each current regulation loop configured to determine a regulated current for a corresponding one of said plurality of LED strings, wherein each current regulation loop comprises a field effect transistor (FET) having a drain coupled to a corresponding LED string of said plurality of LED strings, and a source coupled to ground through a resistor, said FET controlling a current through said corresponding LED string, and therefore the brightness of said corresponding LED string; and an operational amplifier having a first input coupled to a respective dedicated reference voltage supply configured to be independently adjustable, a second input coupled to said source of said FET, and an output coupled to a gate of said FET.