Patent ID: 8253341

Claim:
A control circuit adapted for controlling an electric current to an LED of an LED lamp, comprising: a voltage regulator comprising an output terminal for coupling to an input end of the LED thereby providing the electric current to the LED and a feedback terminal; a feedback circuit comprising an amplifier, the amplifier comprising an in-phase input end, an out-phase input end and an output end, the in-phase input end being adapted for coupling to an output end of the LED, the output end of the amplifier being connected to the feedback terminal of the voltage regulator; and a photo-resistor being connected between the out-phase input end of the amplifier and ground; wherein the photo-resistor senses a change of a light intensity of the LED of the LED lamp and has a resistance increasing along with a decrease of the light intensity of the LED of the LED lamp, the increase of resistance of the photo-resistor being fed back to the voltage regulator via the amplifier, to thereby control the electric current to the LED to be increased so that the light intensity of the LED lamp is maintained within an acceptable range.