Brightness Control of LED Lamps Using Fuzzy Logic Controllers

This paper presents the closed-loop control of high brightness LED lamps using microcontroller. Three types of controllers, proportional-integral (PI) controller, look-up table fuzzy logic controller and real-time calculation fuzzy logic controller are implemented for performance comparison. A photosensitive resistor senses the LED brightness and an 8-bit microcontroller converts brightness signal to numerical value and performs control algorithm. The algorithm is programmed in C language. Selected inputs for fuzzy control algorithm are the brightness error and the change of brightness error. Pulse width modulation (PWM) correction is the only output of the controller and PWM current source is used to drive the LED lamp. Experimental results show that the PI controller needs the least memory and run time, and the real-time calculation fuzzy logic controller requires the most memory and run time, among the designed controllers.