LED Overview

LED is short for the English Light Emitting Diode is a semiconductor with two electrodes emitting devices, allowed a small amount of current will flow through the issue of visible light, produced the first commercial diode in 1960. Its basic structure is an electroluminescent semiconductor materials, placed on a wire rack, and then sealed with epoxy resin around, play a role in protecting the internal core wire, so LED's seismic performance.

The composition of LED
 LED because of its different colors, and its chemical composition different:
 such as red: Aluminum - indium - gallium - phosphide
 green and blue: indium - gallium - nitride
 white and other colors are RGB three primary colors used by the appropriate mixture ratio.
LED semiconductor manufacturing process is similar, but not as good as the semiconductor processing precision, the current cost is still high.

LED working principle and structure diagram
The core part of the light-emitting diode is a p-type semiconductor and n-type semiconductor chip formed in the p-type semiconductor and n-type semiconductor there is a transition layer between, known as the pn junction. In some semiconductor materials, PN junction, the injection of minority carrier and majority carrier recombination extra time to time to the form of light energy released, which convert light energy directly into electrical energy. This use of principle of injection electroluminescence diodes called LEDs produced, known as LED. When it is in working condition when the positive (that ends with a positive voltage), current flows from the LED anode cathode, the semiconductor crystal on the issue of different colors from the ultraviolet to infrared light, light intensity and current.


LED advantages:
 10 万 hours long life;
 can be composed of a variety of colors (such as RGB, etc.)
 drive is relatively simple (no trigger voltage)
 energy conservation, efficiency, higher than the white light, and has further potential to improve.
 small and flexible lighting design.
 short response time;
 environmental protection: No harmful metal mercury.
 low pressure, high safety
LED's shortcomings
 lumens per watt high cost.
 light efficiency fluorescent or HID not high.
 need to drive, drive (not as a simple white light)

LED lighting industry is currently the main application

* Building exterior lighting
* Entertainment and stage lighting
* Interior display lighting
* Roads, landscape lighting
* Identify and indicative lighting
* Traffic lights, video screens

LED lights have been used for several decades,
Why now LED re interested in?

 in recent years to improve the brightness of the LED, it may be light source, not just light.
 LED technology is still in its initial phase, expected in the next 5-10 years, in improving the optical efficiency, reduce cost of the considerable progress.
 LED light source in the future will be the traditional lighting of the other competitors

Several major LED manufacturers  LumiLeds
 Osram
 Cree
. Nichia
 Toshiba

The current common LED lamp
Currently, LED lamps are commonly available in the market are as follows:
LED underground light, LED underwater lights, LED lawn lamp, LED contour light, LED rainbow tube, LED lamp cup, LED Floodlight, LED spotlights, LED brick lights, LED wall lamp, LED bulb and so on.
With the LED light effect of the increase, and the key technology continues to improve and optimize, and several companies introduced a combined solar energy and solar power semiconductor LED lights.


LED color
LED is usually given only one color (single narrow spectrum), have higher color saturation.

LED Colour of  issued as a single LED is a narrow spectrum, so its color is very low.
 Although, in theory, RGB tri-color LED's color rendering index of 85. But only about 60.
 order to improve the CRI above 90, need to join the fourth between red and green the color of amber.
 phosphide coated blue or UV LED plus a CRI range between 75-80.

The role of LED drive
 basic role is to drive a constant current to the LED. In the selection of key considerations need to drive the drive acceptable power loss.