Research on Temperature Property of Illuminantion White LED

Optical and color parameters are luminous flux, color coordinate, color temperature, color rendering index and light efficiency for white LED illumination light source. They depend mainly on materials of semiconductor and phosphor. Operation current and temperature also affect on them. The relation between operation current, temperature and optical and color parameters were researched in sphere and constant driving current source. Property of white LED by phosphor is better than that of tri-color white LED in light efficiency. It consists of part blue light and yellow or red green light produced by the phosphor under blue LED's excitation. With the increase of LED operation current, the temperature of LED also increases, wavelength of blue light moves to long wavelength. It does not match on exciting wavelength of phosphor. The luminous energy of yellow or red green light decreases in phosphor. The increase of temperature produced decrease of energy directly, simultaneity. Light efficiency of LED decreases. The LED color changes from white to blue. Color rendering index is bad. When operation current of LED is constant and the operation temperature increases from 20°C to 130°C, the results are similar to that of above. In order to improve light efficiency of LED, current of 20mA and operation temperature less than 50°C are better. 40-50mA current is also used in order to decrease number of LED and cost. Rendering index of white LED is about 80 because its red energy is less than sunlight. It can be improved to 93 by increasing the red light. The best approach is to improve red emission of the phosphor.