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The structure and principle of LED light

Views: Date2012/3/16

1. the structure and principle of LED light
50 years ago, people already know semiconductor material can produce the basic knowledge of the light, the first commercial diode produced in 1960. LED light emitting diode is in English (light emitting diode) is the abbreviation of, its basic structure is a piece of electroluminescent semiconductor materials, in a lead shelves, and then around sealed with epoxy resin, rise to protect the internal polishing effects, so the aseismatic performance of LED. LED structure as below the core part of leds by p type semiconductor and n type of semiconductor chip, in p type semiconductor and n type semiconductor between one transition layer, called p-n ". In some semiconductor materials PN junction, injection of minority carriers and majority carrier composite, they'll put extra energy to light form released, and thus the energy directly convert light energy. PN junction and reverse voltage, minority carriers to infuse, it does not shine. This kind of make use of the basic principle of electroluminescent made diodes that light emitting diode, films LED. When it's in a positive working state (i.e. both ends and the forward voltage), current flow from LED anode cathode, semiconductor crystals from uv out different color of light to infrared light, and the strength of the current relevant.

2, LED light source characteristics
1). Voltage: LED use the low voltage power supply, the power supply voltage in between 6 to 24 V, according to the product vary, so it is a more security than using high voltage power supply of power supply, especially used in public places.
2). Effectiveness: energy consumption compared with efficacy of incandescent lamp reduced by 80%
3). Applicability: small, each unit LED small pieces is 3-5 mm square, so can preparation into various shapes of the device, and suitable for variable environment
4). Stability: 100000 hours, light failure for initial 50%
5). Response time: the incandescent light bulb response time for milliseconds level, the response time of the LED lights for ns level
6). On the environmental pollution: without harmful metal mercury
7). Color: change the current can change color, light emitting diode easily through the chemically modified method, adjust the material band structure and band gap, realize the red yellow green glow orange color more Syria. Such as small current red LED, with the increase of the current, can in turn into orange, yellow, and finally for the green 8. Price: LED price relatively expensive, than incandescent lamp, a few LED the price of an incandescent light bulb and the price is fairly, and usually each group to the signal by 300 ~ 500 only a diode.

3, monochromatic radiations kinds and LED the development history
The earliest application semiconductor P-N and the principle of light made LED light source came in the early '1960 s. When used materials is GaAsP, glowing red ( p = 650 nm), in the drive current to 20 ma, flux only to per several lumens, corresponding luminous efficiency about 0.1 lumens/watts. In the mid 70 s, the introduction of elements In and N, make LED produce green light ( p = 555 nm), yellow ( p = 590 nm) and orange light ( p = 610 nm), efficacy also improve to 1 lumens/watts. At the beginning of the 80's, there was GaAlAs LED light source, make the red LED efficiency up to 10 lumens/watts. 90 s, glowing red, yellow and green, the GaAlInP hair blue light GaInN of two kinds of the development of new materials success, and to make LED efficiency get the large scale enhancement. In 2000, the former in LED made of red, orange area ( p = 615 nm) efficiency reached 100 lumens/watts, while the latter LED in the green zone made ( p = 530 nm) efficiency can be up to 50 lumens/watts.

4, the application of monochromatic light, LED
Originally used as instruments instructions LED light source, then all kinds of light color LED in the traffic lights and large area in the display to a wide range of applications, produce a good economic benefit and social benefit. With 12 inches of a red traffic light, for example, in the United States was using the long life, low efficiency and 140 watts of incandescent lamp as the light source, it produces 2000 lumens of white light. The red filter, light loss 90%, only 200 lumens of the red light. And in the new design lamp, Lumileds company adopted 18 red LED light source, including circuit, loss, total power consumption and tile, can produce the same efficacy.
Car lights is also an important field application LED light source. In 1987, China began to installed in the car high the brake lights, because LED fast response (ns level), could help make the vehicle driver know followed driving condition, reduce car tracing cauda accidents.
In addition, LED lamp in outdoor red, green, blue full-color display, the key buckles type miniature areas such as the torch has been applied.

5, the white LED development
For general lighting speaking, people need more white light source. 1998 years of successful development LED to send the white light. This LED to GaN chip and is yttrium aluminum garnet (YAG) package together make it. GaN chip hair blu-ray ( p = 465 nm, Wd = 30 nm), high temperature sintering containing Ce3 + YAG phosphors inspired by this a yellow light blue light after launch, peak 550 nm. Blue LED substrate installed in bowl form reflex cavity, cover with mixed with a thin layer of YAG resin, about 200-500 nm. LED by a blu-ray part substrate phosphor absorption, the other part of blue and a yellow phosphor mixing, can get to white light. Now, for InGaN/YAG white LED by changing YAG phosphors and adjust the chemical composition of phosphor layer thickness, can get 3500-10000 K color temperature of all kinds of white light. At present, the first product commercialization has for blu-ray single crystal slice plus YAG yellow phosphor, its best luminous efficiency about 25 lumens/tile, YAG for Japan, and the company more than the import, the price is in 2000 yuan/kg; The second is Japan's sumitomo electric also developed for materials with ZnSe white LED, but the luminous efficiency is poorer. From the table can also see some types of white LED light source from four kinds of phosphor: namely three colors rare earth red, green, blue powder and garnet structure of the yellow powder, in the future more promising is three wavelength light, namely to inorganic ultraviolet light and R.G.B chip three color phosphor, for packaging LED the white light, three wavelength is expected to white LED the commercialization of machine this year have opportunity. But here three different schemes of particle size requirements are small, stability requirement is high, and the concrete application is still in the exploration.

6, industry profiles
LED industry in Chinese, Japanese and chemical is the first with the technology developed in different wavelengths of high brightness LED, and LanZiGuang semiconductor Laser (Laser Diode; LD), are the blue light heavyweight patent holds the LED industry. In the day and get blue LED production and chemical structure and many other basic patent electrode, insist on not provide authorization, only by production itself strategy, intention corner the market, make the high price of blue LED. But other already has the ability of production operator quite disagree, in part, LED investors believe that day and chemical strategy, will make the Japanese in the blue and white LED competition, Europe and America and other countries had gradually the LED industry with a head start, and will be to the whole Japan LED industry badly hurt. So many companies will leave no stone unturned to blu-ray LED of research and production. At present ChuRi and chemical and sumitomo electric outside, still have a Toyota synthesis, LuoMu, Toshiba and sharp, American businessmen Cree, global 3 big lighting factory singular, philips, osram and HP, Siemens, Research, EMCORE etc into the product of Research and production, to promote the industrialization of white LED products, market play a positive role in promoting.