Development of Dynamic Light Controller for Variable CCT White LED Light Source

摘要

In this article, a simple dynamic light controller (DLC) is proposed, designed, and fabricated for practical realization of variable correlated color temperature (CCT) but constant light output white light emitting diode (WLED) light source. This WLED light source consists of alternate strings of warm white (WW) and cool white (CW) LEDs. Light control logic of developed DLC is based on Grassman's color mixing law and hence the range of CCT variation of the test light source lies within the CCT values of the WW and the CW LEDs. A pulse width modulation (PWM) technique is applied to implement the light control logic and embedded in a PIC 18F4550 microcontroller to control the light outputs of two WLED arrays through enhanced PWM mode with dual PWM output. The developed controller is connected with the test light source and controllable by infrared (IR) remote within a distance of 4 m. Thus, the developed DLC is an integrated module consisting of an IR receiver, IR decoder, control signal (PWM) generator, amplifier, and switching device. Performance of the developed DLC is experimentally validated for a set of desired CCT points (2840-5750 K) and constant illuminance (300 lx) measured at a fixed distance. Measured CCT values show maximum deviation of 160 and 194 K for warm white and cool white regions, respectively, compared to desired CCT points. On the other hand, the deviation of measured illuminance values lies within -9.7% to +8.3% with respect to set illuminance value of 300 lx. Variations of measured CCT lie within the acceptable range. Experimental results establish the satisfactory performance of the developed DLC.