Implementation method and advantages and disadvantages of white LED

- Aug 07, 2019-

At present, there are three main methods for LEDs to achieve white light:


1. Synthesize white light through LED tri-color multi-chipset with red, green and blue.


Advantages: high efficiency, controllable color temperature and good color rendering.


Disadvantages: Different color decay of the three primary colors leads to unstable color temperature, complicated control circuit and high cost.


2. The blue LED chip excites the yellow phosphor, and the white light is emitted by the blue light of the LED and the yellow-green light emitted by the phosphor. In order to improve the color rendering performance, a small amount of red phosphor or a suitable amount of green and red phosphor may be added thereto.


Advantages: high efficiency, simple preparation, good temperature stability and good color rendering.


Disadvantages: poor consistency, color temperature changes with angle.


3. The ultraviolet light LED chip excites the phosphor to emit three primary colors to synthesize white light.


Advantages: good color rendering and simple preparation.


Disadvantages: At present, the efficiency of LED chips is low, there is a problem of ultraviolet light leakage, and the problem of temperature stability of phosphors needs to be solved.


UV LED + RGB three-color fluorescence scheme features


Advantages:


1) The white coordinate point is determined only by the phosphor itself, independent of the excitation wafer (the dispersion of the LED wafer can be tolerated).


2) A very high color reduction index RI can be achieved.


3) In theory, it is the simplest manufacturing solution.


4) The stability of the color light depends only on the phosphor and can be very stable.


Disadvantages:


1) Leaked UV light can damage the LED sealant, resulting in device life issues.


2) The light conversion efficiency is not high, self absorption, light transmittance, and the like.


Challenges:


1) No trials have been successful so far.


2) There are currently no phosphors that can excite blue light.


3) The color will change as the angle of observation changes.


4) The sealant must be resistant to UV damage.


5) The stability of RGB phosphors has yet to be further improved.


LED (Blue) + Phosphor (Yellow) program features


Advantages:


1) Only a single phosphor is relatively simple to manufacture.


2) The phosphor with single blue light is mature and the supply is abundant.


3) The color of the white light is moderately reduced (RI? 75%).


4) The stability of the phosphor can already meet the requirements of color reduction.


Disadvantages:


1) Light conversion efficiency is not high, self absorption, light transmittance, and the like.


2) The degree of color reduction is not high enough.


3) The stability of color is greatly affected by temperature and drive current.


4) The color will change as the viewing angle changes.


Characteristics of RGB three primary color LED color mixing scheme


Advantages:


1) The highest photoelectric efficiency. From the perspective of long-term development, such a plan would be a mainstream solution.


2) Random color adjustment can be achieved.


3) Excellent color rendering ability (RI).


4) Very wide color gamut range.


Disadvantages:


1) Complex color-light feedback control is required to compensate for the characteristics of LED material properties as a function of temperature, and the light-damping characteristics of LEDs.


2) The color adjustment is very different and varied.