Nowadays White LEDs are popular in lighting. In the beginning, LEDs can not be used to application like displays, indicators etc due to their limits. However with the appearance of White LEDs, they can be used from indoor to road lighting. Although LEDs cannot emit white light by natural, but use of some technologies can make to emit white light.
Color Mixing or RBG Method
Multiple color LEDs are fitted within a lamp, basic primary colors of LEDs red, blue and green with proportional intensity of each LEDs is tempered to obtain white light. This method require minimum two LEDs in conjunction, usually blue and yellow color light whose intensities are to be varied so as to get white light. Color Mixing technique can be done by using four LEDs. During conversion method, there is no loss of energy therefore phosphors are not utilized in color mixing.
The Phosphor Method
The Phosphor white technique produces white light by combination of short wavelength LED like blue and a yellow phosphor coating in single LED.
In this single LED, blue light generated travels through the phosphor layer without any alter, or in the phosphor layer they are converted into yellow photon. The combination of both photons blue and yellow give white light.
Usually Phosphor white offers far better color rendering and more efficient that RGB white. Due to this advantages, they are popular used method of producing white light in LEDs.