LED light-emitting diode with LED street lighting

LED light-emitting diode is a solid-state semiconductor devices, which can be converted directly into electricity to light. Heart of the LED street lighting is a semiconductor wafer , the wafer is attached to one end of a stent, is the negative side , the other end connected to the positive power supply , so that the whole chip is epoxy encapsulated. Semiconductor chip consists of two parts, part of the P -type semiconductor , the hole in it dominates the other side is an N-type semiconductor, here is mainly electronic . But the two semiconductor connected , when between them to form a PN junction . When the current through the wire on the chip when the electron will be pushed to the P region , in the P zone electron hole recombination , and then will be issued in the form of photon energy , which is the principle of LED light . Is the wavelength of the light color of the light , is formed by the PN junction to the materials . 50 years ago, people have to understand the semiconductor material can produce light of the basic knowledge, the first commercial diode produced in 1960 . LED is the English lightemittingdiode ( Light Emitting Diode ) acronym , and its basic structure is an electroluminescent semiconductor materials, placed on a wire rack, then sealed with epoxy resin around , protect the internal core lines of action , so the LED 's seismic performance.The core part of the light emitting diodeA p -type semiconductor and n-type semiconductor chip formed in the p -type semiconductor and an n -type semiconductor between a transition layer , called the pn junction . In some semiconductor materials, PN junction, the injection of minority carrier and majority carrier recombination, when will the excess energy released in the form of light , which converts electrical energy directly into light energy . PN junction reverse voltage , minority carrier injection is difficult , it is not light . This use of injection electroluminescent diodes called the principle of making light-emitting diodes, commonly known as LED. When it is in working condition ( ie, ends with a positive voltage ) , current from the LED anode to the cathode , the semiconductor crystals from the ultraviolet to the infrared light of different colors , light intensity and current .Initially LED as light source instrumentation instructions , and later in a variety of light color of the LED traffic lights and a large area of ​​the display has been widely used to produce good economic and social benefits. A 12 -inch red traffic lights, for example , could have been used in the United States long-life , low -efficiency 140- watt incandescent lamp as a light source , which produces 2000 lumens of white light. The red filter , 90% light loss , only 200 lumens of red light . In the new design of the lamp , Lumileds company adopted 18 red LED light sources , including circuit losses, including a total power of 14 watts to produce the same light effect. Car lights are also important areas of the LED light source applications .For general lighting purposes, people need a white light source . 1998 glowing LED developed. This is the GaN LED chip and yttrium aluminum garnet (YAG) packaged together to make . GaN chip emits blue light (λp = 465nm, Wd = 30nm), high-temperature sintering of Ce3 + -containing YAG phosphor excited by this blue light yellow light emission , peak 550nm. Blue LED substrate mounted on the reflective cavity bowl , covered with a thin layer of resin mixed with YAG , about 200-500nm. LED substrate portion of the blue light emitted by the phosphor absorbed, and some blue and yellow light emitted phosphor mixture can be too white . Now, for InGaNYAG white LED, a YAG phosphor by changing the chemical composition and adjust the thickness of the phosphor layer can be obtained color temperature 3500-10000K in colored white . The blue LED to get through the white way , simple structure , low cost , mature technology and high , so use the most.60s of last century , scientists and the use of semiconductor PN junction light-emitting principle , research into LED light-emitting diode. With the development of of the LED, the materials are GaASP, its luminous color is red. After nearly 30 years of development, now we are very familiar with the LED, has been able to emit red , orange, yellow, green, blue and other colored light . However, white light LED lighting required only in the developed only in recent years , here introduces the reader to the relevant lighting white LED.1 . LED white light visible spectrum and the relationshipAll week , the visible spectrum wavelength range 380nm ~ 760nm, the human eye can sense light seven colors - red, orange, yellow, green , cyan, blue, purple, but all seven colors of light are each one kind of monochromatic light . Such as the red LED is the peak wavelength of 565nm. In the visible spectrum is no white light , because white light is not monochromatic , but by a variety of synthetic complex monochromatic light , monochromatic light as the sun light consists of seven synthetic white light , and the color television white light is composed of three primary colors yellow , green , blue synthesis. Thus , to make the LED emits white light , its spectral characteristics should include the entire visible spectral range. But to manufacture this performance of the LED, the current process conditions is impossible. According to one study of visible light , the human eye can see is white, at least two kinds of light mixed , ie two -wavelength LED ( light blue + yellow light ) or three -wavelength LED ( blue light + green light + red light ) mode . The two modes of white light, blue light is required , so the intake of white light blue light has become a key manufacturing technology, namely the current major LED manufacturing company chase "Blu-ray technology ." Current international master "Blu-ray technology," only a handful of vendors , so white LED application, especially in high- brightness white LED in our country there is a process to promote .2 . White LED light source technology structure and whiteFor general lighting , in the process structure, the white LED is usually formed in two ways , the first is the use of "Blu-ray technology," and with the formation of white phosphor ; second is a variety of monochromatic light hybrid approach . Both methods have been successfully produced white device . The first method to produce white light system shown in Figure 1 , the figure LEDGaM chip emits blue light (λp = 465nm), it YAG ( yttrium aluminum garnet ) phosphor package together , when the phosphor excited by the blue light yellow light as a result, formed by mixing blue and yellow white ( constituting the LED shown in Figure 2 ) . The second method uses a different shade of the chip package together through color mixing to produce white light .3 . New light white LED lighting application prospectsTo illustrate the characteristics of white LED , first look at the current illumination light source used in the situation . Incandescent and halogen lamps , the luminous efficiency of 12 to 24 lumens / watt ; fluorescent and HID lamps light efficiency of 50 to 120 lumens / watt. For white LED: In 1998 , the white  LED street lighting effect only 5 lm / W by 1999 had reached 15 lm / W, this indicator with general household incandescent lamps , and in 2000 , the white LED light effect reached 25 lm / W, this indicator with halogen similar. There are forecasts that by 2005 , LED light efficiency up to 50 lm / W, 2015 , LED light efficiency is expected to reach 150 ~ 200 lumens / watt. Then the white LED current can Daan Pei level . Thus developing writers with white LED light source, will become possible reality .Ordinary incandescent and halogen lighting , although cheap, but low light efficiency ( thermal effect of light in vain consumption ) , short life, maintenance workload , but if a white LED for lighting, not only high luminous efficiency and lifetime long ( more than 10,000 hours continuous working time ) , almost no maintenance. Currently, the German company Hella has developed the aircraft using the white LED reading light ; Australian capital, Canberra, has spent a street white LED for street lighting ; China's urban traffic control lights are being replaced with white LED light traffic order early . Can be expected in the near future , white LED will enter the home to replace the existing lighting.

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