Patent ID: 8310163

Claim:
A lighting control system using with a microcontroller, comprising: a lighting load; a semi-conductor switching device coupled to the lighting load and an AC power, wherein the semi-conductor switching device controls a time period for the AC power transmitting an electric power to the lighting load; a zero-crossing-point detection circuit coupled to the AC power, wherein the zero-crossing-point detection circuit converts AC voltage sine-waves into symmetric square-waves, and an edge of the symmetric square-wave corresponds to a zero-crossing point of the AC voltage sine-wave; and a microcontroller coupled to the semi-conductor switching device and the zero-crossing-point detection circuit, wherein the microcontroller receives the symmetric square-wave and sends out a zero-crossing-point time-delay pulse to the semi-conductor switching device, and the zero-crossing-point time-delay pulse lags with a time difference behind the edge of the symmetric square-wave, wherein the said time difference ranges from (t o ) to (1/(2f)−t o ), wherein t o =(1/2πf)sin −1 (V t /V m ), f is frequency of the AC power, V m is voltage amplitude of the AC and V t is threshold voltage for the electric current flowing in the lighting load.