At present, There are mainly three methods to achieve white LED:
1. By trichromatic: red, green and blue combine together with multi-chip, and emit the white color light.
Advantages: high efficiency, color temperature controlable, color rendering index (CRI) is good.
Disadvantages: The light attenuation of three colors are different, result temperature instability, the control of circuitry are complex, cost are high.
2. Blue chip excites yellow phosphor and result white color, this is combined by the blue LED light and the yellow-green color of phosphor, it can also add in a small amount of red phosphor or both plus green and red phosphors to improve the CRI.
Advantages: high efficiency, easy production, stable temperature and good CRI.
Disadvantages: Consistency is poor, color temperature change with the angle.
3. UV color led chip excite phosphors to issue trichromatic, and then combine the white color.
Advantages: the CRI is good and easy production.
Disadvantages: At present, the efficient of LED chip is low, and there are ultraviolet light leak problem, also the phosphor temperature is not stable.
