Principle of white light LED

White LEDs have several different working principles. Figure 1 shows three typical principles. The "blue LED + yellow phosphor" type in Figure 1a is the highest level of white LED development, and it is most likely to be used in the first-generation LED automotive headlamp system. The "ultraviolet LED + red, green and blue" three-color phosphor in Figure 1b has the most potential as a general lighting system due to its high color rendering index, but how to overcome it when it is used as a headlamp system The aging effect of ultraviolet light on plastics. The "red-green-blue three-chip" type in Figure 1c has the ability to change the color of light, but it still cannot be used in headlight systems, because it is difficult to overcome it Color change, this color change may come from the different temperature characteristics of the three chips, or it may come from the loss degradation speed of different LEDs.