Impact of current controlled dimming on spectral characteristics of high power LEDs

摘要

Conventional light sources are reproducible with consistency in light output and colour points, whereas LEDs do not provide output level stability. The lumen output changes with temperature and age. The process of reducing the light output of LED is called dimming. LED can be dimmed by two different ways one by changing the forward current called linear dimming and secondly by modifying the pulse width called PWM technique. Typically the current through LED is controlled by a variable resistor. This paper reports the effect of variation of forward current on spectral characteristics of one watt red, green, blue and warm white LEDs. Red LED shows red shift while blue and green LED shows blue shift for increase in forward current. Warm white LED shows blue shift for lower as well as higher peak wavelengths.