LED current control system for LED drive system with multiple dimming inputs

摘要

A LED current control system for use with an LED drive system which includes LED strings connected in series with respective current sink circuits, each of which causes a current to be conducted by the LED string to which it is connected. The drive system includes 3 or more ‘dimming’ inputs with which the LED string currents can be adjusted. The LED current control system comprises at least one minimum circuit which receives two or more dimming inputs and produces an output which is proportional to the lesser of the inputs, a multiplier circuit which receives the outputs of the minimum circuits and at least one other dimming input and produces an output ILED which is proportional to the product of the received signals, and a sink control circuit which receives ILED and controls the current sink circuits such that the string currents vary with ILED.

主权项

1. 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.