What is LED:
LED is the English Light Emitting Diode, the light-emitting diode, is a solid light-emitting semiconductor devices, it is as light-emitting semiconductor chip using solid materials, when coupled with a positive voltage across the semiconductor carrier in place complex induced photon emission and produce light. LED can be directly given red, yellow, blue, green, blue, orange, purple, white light. LED lights is the use of LED as a light source created by the high-tech products.
The core part of the light-emitting diode is a P-type semiconductor and N type semiconductor wafer formed in the P-type semiconductors and N-type semiconductor between a transition layer, called the PN junction. In certain semiconductor materials, PN junction, the injection of minority carrier and majority carrier recombination, when will the excess energy released in the form of light to convert light energy directly into electrical energy. PN junction reverse voltage, minority-carrier injection is difficult, it is not light. The use of injection principle of the production of electroluminescent diodes called LEDs, referred to as LED. When it is in working condition when a positive (that ends with a positive voltage), current from the LED anode to the cathode, the semiconductor crystals to the making of different colors from the ultraviolet to infrared light, light intensity and current.
LED light source is known as fourth generation or green light, with energy saving, environmental protection, long life, small size and other characteristics, can be widely applied in various directions, display, decoration, backlight, general lighting, and urban landscape and other fields. In recent years, countries around the world, research and application of LED in a fierce technological competition. Since 2000, U.S. $ 500,000,000 investment in the implementation of the "National Semiconductor Lighting Plan", also in July 2000 the EU announced the launch of similar programs. China's "863" program support, in June 2003 proposed the development of the first semiconductor lighting program.
LED light energy principle:
Monochromatic light of high brightness LED has made progress in the market. Although they are more expensive than traditional bulbs, but they can be offset by the advantages of its high price, that it has a higher price. First, a red LED light intensity required to achieve a certain amount of energy is 15 watts, while the traditional light bulb to achieve the same measure will have up to 150 watts of energy consumption; addition, according to the scientists determined, LED power light, there are 10 % of the energy can be converted into light, and incandescent bulbs, only 7-8% conversion efficiency, we can see, to achieve the same lighting effect, LED lights are clear than the incandescent lamp.
LED advantages:
* Light (energy conversion) efficiency - that is more energy, higher than conventional bulbs.
* Response (switching) time soon - can achieve high flicker frequency.
* Long service life - up to 35,000 ~ 50,000 hours, relative fluorescent 10,000 to 15,000 hours, 1,000 to 2,000 hours of incandescent light.
* Resistant to shocks and other mechanical impact - because it is solid state devices, the relative fluorescent, incandescent and so can withstand a greater shock.
* Small size - can make their own very small size (less than 2mm).
* Easy to focus on - because light is small and easy and the lens to achieve the required distribution levels, etc., by changing the package shape, direction and even from the large-angle focus on the small angle scattering can be achieved.
* A variety of colors - can not add filter to provide a variety of different colors, and strong color.
* Rich color gamut - LED cover wide color gamut than other light sources.
LED Disadvantages:
* Thermal issues will be substantially reduced if the life of poor heat dissipation.
* LED light power of low-end or lower than the energy saving lamps (cold cathode tubes, CCFL).
* The initial purchase cost is higher.
* Energy Saving LED light source direction due to strong LED lighting design need to consider the special optical properties.
LED History:
The first application of the principle of semiconductor PN junction light-emitting LED light source made of 60 came in the early 20th century. Use at the time of the material is GaAsP, fat red (λp = 650nm), the drive current of 20 mA, the luminous flux is only a few lumens per thousand, and the corresponding luminous efficiency of about 0.1 lumens / watt.
The mid-70s, the introduction of elements of In and N, the LED produces green (λp = 555nm), yellow (λp = 590nm) and orange (λp = 610nm), luminous efficiency is also increased to 1 lumen / watt.
To the early 80s, there's GaAlAs LED light source, so red LED light efficiency of 10 lumens / watt.
Early 90s, red light, yellow light GaAlInP and hair green and blue GaInN successful development of two new materials to make LED light effect has been greatly improved. In 2000, the former is made of LED in red, orange area (λp = 615nm) of the luminous efficiency of 100 lm / W, which made the green zone LED (λp = 530nm) of the luminous efficiency can reach 50 lm / watts.
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