1, LED light emitting structure and principle
It has been about 50 years ago, the semiconductor material can produce light of the basic knowledge, the first commercial diode produced in 1959. LED is the English light emitting diode (LED) acronym, and its basic structure is a piece of electroluminescent semiconductor materials, designed into a wire rack, after that sealed with epoxy resin around, protect the internal core wire effect, so LED's seismic performance.
The core part for 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 was a transition between, known because 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 onto electrical energy. PN junction reverse voltage, minority carrier injection is difficult, involved with not light. This utilization of principle of injection electroluminescence diodes called LEDs produced, known as LED. Due to is in working condition when the positive (that ends with a positive voltage), current flows off of the cathode LED anode, the semiconductor crystal on problem from the ultraviolet to infrared light of different colors of light intensity and current.
2, LED light source characteristics
1. Voltage: LED using low-voltage power supply, power supply voltage between 6-24V, vary according to product, so around the globe more secure than using high voltage power supply, especially for public places.
2. Effectiveness: utilization of energy efficient than incandescent light with 80% reduction
3. Applicability: small, small piece every single LED unit is 3-5mm square, it will possibly be fabricated into various shapes of this devices, and volatile environment for
4. Stability: 100,000 hours, the light fades to 50% of the initial
5. Response time: the incandescent millisecond response time, LED lights nanosecond response time
6. Through the environmental pollution: no harmful metal mercury
7. Color: you can alter the current color, light-emitting diodes by chemical modification methods merely adjust expand into all the band structure and band gap, accomplish multi-color light orange red Huanglv Lan. Such considering that small current when the red LED, with the present increase, alter into orange, yellow, not only that to green
8. Price: LED's are expensive, compared to incandescent lamps, a few LED's price on the price with an incandescent lamp rather, each signal usually require to the previous 300 to 500 diodes.
3, monochromatic LED types and history
The first application of principles of semiconductor PN junction light-emitting LED light source made of 60 came in the early 20th hundred years. The material will then be used GaAsP, hair red ( p = 650nm), the drive current of 20 mA, the luminous flux of only a few lumens per thousand, the related luminous efficiency of about 0.1 lumens / watt.
Mid-70s, the roll-out of elements of In and N, create green LED ( p = 555nm), yellow ( p = 590nm) and orange ( p = 610nm), optical efficiency additionally increased to 1 lumen / watt.
To the very first 80s, appeared in the LED source of light GaAlAs do the red LED light efficiency of 10 lumens / watt.
The early 90s, hair, red and yellow of GaAlInP and hair green, blue GaInN developed two new mats to make LED light effect was greatly improved. In 2000, the previous is made from LED in red and orange zone ( p = 615nm) light efficiency to 100 lm / W, which made the green LED each morning region ( p = 530nm) light efficiency can reach 50 lm / watts.
Fourth, software of monochromatic LED
Initially used as instruments of instruction LED light source, then all regarding light-colored LED in traffic lights and big screens the particular widely used and produced good economic and social benefits. To 12-inch red traffic lights, for example, could have been used associated with United States long life, low-light 140-watt incandescent effective as light source, it makes 2000 Lumens of light. The red filter, the optical loss of 90%, only 200 lumens of red light. In light of brand new design, Lumileds has used a red LED light source 18, including circuit losses, including earnings power of 14 watts of light can produce the same effect.
Automotive Led lights are also important areas of sunshine application. In 1987, China began in order to high car brake lights, LED response as fast (nanosecond), can be as early as possible so that the trailing vehicle drivers understandthat driving performance and reducing rear-end difficulty.
In addition, LED lights at the outdoor red, green, blue full-color display, mini flashlight key chain have been the regions of application.
Fifth, growth of white LED
For general lighting, the white light that young people need. 1998 white light LED developed. This really is the GaN LED chip and yttrium aluminum garnet (YAG) made package together. GaN chip of blue ( p = 465nm, Wd = 30nm), made of high-temperature sintering of YAG phosphor containing Ce3 + excited this particular blue light after the yellow emission peak 550nm. Blue LED substrate installed in the reflective cavity bowl, cover along with a mixture of YAG thin layer of resin, about 200-500nm. Issued blue LED substrate partially phosphor absorbed, and some blue mixed with yellow phosphor issued, could be too vivid white. Now, for the InGaN / YAG white LED, YAG phosphor your car the chemical composition and adjust the thickness of the phosphor layer, available colors and color temperature 3500-10000K white.
I am a professional editor from International Trade Community,
and my work is actually promote a free online trade platform.
http://www.xpshou.com/ possess a great deal of understanding of
ribbon collars for dogs , live koi fish
welcome to go to!