Patent ID: 7518320

Claim:
An LED control circuit comprising: an observation circuit to detect a condition of a working environment for generating a voltage signal accordingly; a sampling circuit to receive the voltage signal and generate a digital control signal according to the voltage signal; a controller comprising two outputs to selectively output four binary numbers according to the digital control signal received from the sampling circuit; an LED driving circuit comprising a load resistor; and a regulating circuit comprising four current dividing circuits and a selection switch, wherein each current dividing circuit comprises a resistor and an electric switch element being connected in series, the selection switch comprises two inputs connected to the two outputs of the controller for receiving the binary numbers, and four outputs to respectively output four logical signals to control one or more of the electric switch elements on or of accordingly to thereby adjust the resistance of an effective load of the LED driving circuit between two opposite terminals of the load resistor such that a working current of the LED driving circuit is regulated according to the condition of the working environment.