Patent ID: 8836235

Claim:
An apparatus for automatically controlling illuminance, comprising: a dimming control electronic switch for, if manipulation of a switch by a user is sensed during supply of Alternating Current (AC) power to a Light-Emitting Diode (LED) lamp, interrupting supply of the AC power during a preset period of time based on zero-crossing of the AC power; and an LED lamp control device for measuring duration of zero potential by detecting supply and interruption of the AC power, individually comparing duration of zero potential with a dimming decision time and a power OFF decision time, and if the duration of the zero potential is shorter than the dimming decision time, maintaining the current illuminance of the LED lamp, and if the duration of the zero potential is longer than the dimming decision time and is shorter than the power off decision time, controlling illuminance of the LED lamp, and if the duration of the zero potential is longer than the power off decision time, turning off the LED lamp.