Patent ID: 8907573

Claim:
A LED current control system for an LED drive system which includes one or more LED strings connected in series with respective current sink circuits, each of said current sink circuits arranged to cause a current to be conducted by the LED string to which it is connected, said LED drive system including 3 or more dimming inputs configured to receive signals to adjust said LED string currents, said LED current control system comprising: at least one minimum circuit arranged to receive the signals applied to two or more of said dimming inputs at respective inputs and to produce an output which is proportional to the lesser of the signals applied to said two or more dimming inputs; at least one multiplier circuit arranged to receive outputs of said at least one minimum circuit and the signals applied to at least one other of said dimming inputs at respective inputs and to produce an output ILED which is proportional to the product of the signals applied to inputs of said multiplier circuit; and a sink control circuit arranged to receive said output ILED of the at least one multiplier circuit and to control said current sink circuits such that said LED string currents vary with ILED.