Incandescent start mass production in 1910, Since then, fluorescent lamps and other new sources appear. But over the past 20 years, the lighting industry feel the need to develop new century lighting. COST Europe had developed a five-year action plan, which proposed new light source to meet three criteria: efficiency, energy saving; do not use environmentally harmful materials; simulation of natural light, its color index close to 100. U.S. experts, the semiconductor area has been completed in the electronics revolution, the second revolution in the lighting field, around the year 2020, solid light-emitting efficiency will reach 200lm / w, can be found on the COST program proposed the requirements of the new light source, so set off in the international wave of LED lighting.
Development of white light LED global progress:
Single-chip white LED points, two-chip and three chips, the following will be introduced this classification:
Single-chip
InGaN (Blue) / YAG phosphor
This is a now a more mature product, in which the 1W and 5W Lumileds has bulk product. These products are flip-chip structure, improve the luminous efficiency and heat dissipation. Improved phosphor coating process can be increased by 10 times the color uniformity. Experiments show that the increase in the current and temperature LED spectral blue shift and red shift some, but did not affect fluorescence spectroscopy. Life test results are good, Φ5 white LED 12,000 hours of work, the light output down 80%, and this power LED 12,000 hours of work, only the 10% decline in the estimated 5 million hours of work decreased by 30% after . This is called Luxeon high power LED efficiency 44.3lm / w, the maximum luminous flux is 187lm, industrial products, up to 120lm, Ra is 75-80.
InGaN (blue) / red + green phosphor phosphor
Lumileds, accompanied by 460nmLED SrGa2S4: Eu2 + (green) and SrS: Eu2 + (red) phosphor, 3000K-6000K color temperature can reach a better result, Ra to 82-87, representing these products increased. InGaN (UV) / (red + green + blue) phosphor
Cree, Nichia, Toyota and other companies are making great efforts to develop UV-LED. Cree has produced 50mW, 385nm-405nm UV LED; Toyota has produced such a white LED, the Ra is greater than or equal to 90, but the luminous efficiency is not ideal; Japan Asia recently obtained 365nm, 1mm2, 4.6V, 500mA high-power UV LED, such as made of white LED, will have better results.
ZnSe and white OLED device also made progress, but still far away from industrial production.
Two-chip
By the blue LED + yellow LED, blue LED + yellow LED and the blue-green LED + yellow LED is made of relatively cheap cost of such devices, but as the formation of two colors white LED, color is poor, only in color less demanding occasions.
Three-chip (blue + green + red) LED
Philips, with 470nm, 540nm and 610nm of the LED chip, a device made of Ra greater than 80, color temperature up to 3500K. Such as the use of 470nm, 525nm and 635nm of the LED chip, the lack of yellow color, Ra can only reach 20 or 30.
Luminous flux with wavelength compensation and feedback of the methods for moving down to an acceptable level of color. U.S. adoption of Luxeon RGB TIR device made of a system for landscape lighting products, made by Lumileds LCD TV screen (22 inches), product performance are good.
Fourth chips (blue + green + red + yellow) LED
With 465nm, 535nm, 590nm and 625nm LED chips can be made of Ra greater than 90 white LED.
In addition, Norlux company with 90 tri-color chips (R, G, B) made of 10W white LED, luminous flux of each device 130lm, color temperature of 5500K.
White LED lighting specifications
LED lighting is different from the traditional white LED products, technical performance, there are some special requirements:
A Φ5 LED luminous flux luminous flux only 1lm, while the white power LED for lighting hope to achieve 1Klm. Of course, the luminous flux for the power LED 0.1Klm and 0.01Klm can meet the required low lighting needs. 15W incandescent lamps less efficient as only 8lm / w, so a 15W incandescent lamp of luminous flux, and 25lm / w white power LED5W devices are.
Luminous efficiency of the current industry products from 15lm / w up to 25lm / w, of the level of 32lm / w, the highest level reached 44.3lm / w.
Between the 2500K-6000K color temperature, preferably between 2500K-3500K.
The best color rendering index Ra is 100.
Stability of the wavelength and flux are required to maintain stability, but the extent of its stability in accordance with the demand for the next occasion.
Life of 50,000 to 100,000 hours.
White LED Applications Outlook:
White LED brightness and every increase in power, has further expanded its range of applications. Since 2000, power type LED lighting has been used for special applications. In 2002, Mitsubishi Electric to use it as a mobile phone camera flash, the Lumileds LCD TV screen as the backlight, enhanced color fidelity; Koito Manufacturing production car with a white LED headlights. In addition, white LED landscape lighting, garden lights, has a large number of applications. I estimate that, if the white LED to 1lm / units, based on down to 1 yuan per unit will go into the general family of outdoor lighting; when reduced to 0.5 yuan is expected to enter the room lighting, corridor lighting and other markets; when the time down to 0.25 yuan will begin to replace fluorescent lamps. From the luminous efficiency of view, once entered the 60lm / w, equivalent to 20W fluorescent lamp, white LED will rapidly spread. The next 5 years to 6 years, if the luminous efficiency breakthrough 80lm / W, together with price continues to fall, then 2008-2010, white LED lighting will be gradually extended to a variety of general household lighting, the official act of the 21st century new lighting source.
Currently, there are three white LED technology:
The first principle of the use of three primary colors red, green, and blue super bright white LED mixed;
Second, with the InGaN blue LED die add a small amount of yttrium aluminum garnet based phosphor;
The third is excited by UV LED phosphor powder or other phosphor to produce white light by mixing multi-colored light.
Three techniques have been achieved industry, developed rapidly after the two technologies. Which produce semiconductor light compact, reliable, long life, low voltage, energy saving, no pollution, called the green light is lighting the way for a revolution. White LED and incandescent lamps can save 80% compared to 90% of the electricity, and the life expectancy of more than 10 million hours. The key issue is the high cost of the chip, but cost-effective development of the Rule of electronic products, semiconductor light into the average family is not far away. Currently, high-performance LED is widely used in some special places such as military installations, mining, diving, exploration and other industries. Can say for sure, high-performance LED is becoming a very competitive new light source, it will bring the business of a revolution in lighting technology.
White LED lighting-benefit analysis:
U.S. Department of Energy predicts that by 2010, the United States will have 55% of incandescent and fluorescent lamps were replaced semiconductor, saving only a year to up to 350 billion U.S. dollars. Japan plans, by 2007, the country will have 30% of the incandescent lights were replaced with the semiconductor.
China is the second largest after the U.S. power generation in 2002, China's total power generation capacity was 1.65 trillion kwh, of which 1.34 trillion kwh (80%) of thermal power, a lot of coal and oil combustion, resulting in a large number of dust and SO, Co2 and other gases, environmental pollution is serious. Lighting electricity consumption has more than 150 billion kwh, the total generating capacity of 10% to 12% (developed countries accounted for about 20%), significantly more than the Three Gorges hydropower station on the total generating capacity of 84 billion kwh. The semiconductor lighting energy consumption is one-eighth of incandescent, fluorescent one half of its life span is about 20 times of incandescent lamp to 30 times, 10 times the fluorescent lamp, energy saving and environmental protection is a "bonanza." Therefore, the development of efficient, environmentally friendly and energy-saving white LED light source is necessary.
We the common rack and a large thermal resistance of chip LED as light attenuation, a single device flux is small, but can not do the task instead of the traditional light sources. LED High Power White LED light source device is the only way to enter the field of general lighting. Therefore, the high-power white LED device market are huge.
In addition, the white LED lighting industry with technology-intensive and labor-intensive characteristics of both. Therefore, the development of white LED lighting industry in China, not only the formation of new industrial and export growth, but also save energy and reduce environmental pollution and give full play to China's labor resources, in line with "Shi-Liou," proposed to take a new road to industrialization guiding ideology.
White LED market overview:
The maximum potential LED general lighting applications. As technology advances, high-brightness white LED is a step by step into the huge potential of lighting market. According to Frost & Sullivan's statistics, the current global lighting market, the average annual growth rate of about 5.5%, in 2000 only incandescent, fluorescent size of the market reached 4.5 billion. The industry is generally believed that white LED lighting market in 2010 may be about to mature. The next 7 years, high-brightness LED lighting industry on the global impact will be enormous.
It is predicted that the white LED up to 151.5 percent growth rate, average annual growth rate of the next few years will be as high as 250%. Reed Electronic Re-search statistics show that in 1998 white light LED global market for 7,000 million U.S. dollars, estimated to increase to 2.7 billion last year.
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