Patent ID: 8314574

Claim:
A control circuit adapted for controlling an electric current through 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 out-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 at least a photo-resistor being connected between the in-phase input end of the amplifier and ground; wherein the at least a photo-resistor senses a change of a brightness level of an environment surrounding the LED lamp and has a resistance thereof increasing along with a decrease of the brightness level of the environment surrounding the LED lamp, the increase of resistance of the at least a 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 an intensity of light output of the LED is increased.