LED (Light-emitting diode), also known as light-emitting diodes, which use semiconductor chips as a solid light-emitting materials, when the two ends together with the forward voltage, the semiconductor carrier in the composite occurred, release excess energy and have a visible light photon emission caused.
(A) LED's development history
Application of semiconductor junction P • N principle into LED light source made available in the 20th century, early 60s, first appeared in 1964 in red light-emitting diode, followed by a yellow LED. Until 1994, blue, green LED was developed. Japan in 1996 by Nichia Corporation (Nichia) successfully developed a white LED.
Its inherent characteristics of LED, such as energy saving, long life, vibration-resistant, fast response, characterized by cold light source is widely used in light, signal light, display, landscape lighting field, and in our daily life can be seen everywhere , household appliances, telephone, dashboard lighting, automotive anti-fog lamps, traffic lights and so on. However, due to its poor brightness, which is very expensive, such as constraints, can not be applied as a general source.
In recent years, with the semiconductor light-emitting materials for the deepening of the study, LED manufacturing technology advances and new materials (crystal and nitride phosphors) the development and application of a variety of colors made of ultra-high brightness LED breakthrough progress, and its light-emitting efficiency by approximately 1,000 times, color has been achieved in all colors of visible light, the most important of which is the ultra-high brightness white LED enable applications across the LED light source of highly efficient market. It has been pointed out that the high-brightness LED will be the following human after Edison invented incandescent bulbs, one of the greatest inventions.
(B) LED light-emitting principle
Light-emitting diode chip by the PN junction, the electrode and optical system. Its luminous body - the area of the chip 10.12mil (1mil = 0.0254 square mm), the current major international chip LED, the chip area of 40mil.
Its light-emitting process includes three parts: under the forward bias carrier injection, radiation and energy transfer complex. Tiny semiconductor chip is packaged in clean resin material, when the electronic after the chip, the negatively charged electron to move to the positively charged region of the hole and with the compound, the disappearance of electrons and holes at the same time have a photon . Between the electron and hole energy (band gap) the greater the energy generated by the higher photon. Photon energy in turn corresponds with the color of light, visible light range of the spectrum, blue light, purple light energy to carry the largest, orange light, red light energy to carry at least. Because different materials have different band gap, which can be different colors of light.
LED lighting will be the mainstream of high-brightness white LED. At present, the commercialization of white LED are second wavelength, that is, Blu-ray single-chip mixed with YAG phosphors produce white light yellow. Was optimistic about the future than the three-wavelength white-light LED, that is inorganic UV chip plus red, blue and green produce white light mixed color phosphors, which will replace the fluorescent lamps, compact fluorescent light bulbs and energy-saving LED backlight and other markets.
(C) LED light source of the basic characteristics of
1. high efficiency light-emitting
LED After decades of technological improvements, the luminous efficiency have been greatly improved. Incandescent, halogen light effect for the 12-24 lm / watt, fluorescent light 50 to 70 lm / W, sodium 90 ~ 140 lm / W, most of the power loss into heat. LED luminous efficiency will be improved to achieve up to 50 ~ 200 lm / W, and the monochromatic light is good, narrow spectrum without the issue of color filters can be directly visible. At present, all countries in the world are stepping up to improve efficiency LED light research, in the near future, its luminous efficiency improvement will be greater.
2. less power consumption
LED single-tube-power 0.03 ~ 0.06 watts, the use of DC-driven, single-tube drive voltage of 1.5 ~ 3.5 V, current 15 to 18 milliamperes, the reaction speed, available at high-frequency operation. The same lighting effects, the power consumption is one-eighth of incandescent bulbs, fluorescent tubes half, the Japanese estimates, such as fluorescent light efficiency is even higher than twice the LED half of those in Japan to replace incandescent and fluorescent lamps in. Equivalent to annual savings of 6000 million liters of crude oil. Lights were on the bridge parapet, also an effect of more than 40-watt fluorescent lamp, and the power of each LED using only 8 watts, and can change color.
3. long service life
Use of electronic radiation emitting light field, light-emitting filament burnability, heat deposition, the shortcomings of optical attenuation. The use of LED lights are small, light weight, epoxy package and can withstand high-intensity mechanical shock and vibration, not broken. The average life expectancy of up to 100,000 hours. LED lamp life of up to 5 ~ 10 years, the lamp can be significantly reduced maintenance costs, avoid the regular lights for them.
4. strong security and reliability
Low heat, non-thermal radiation, cold light source, can be safely arrived in touch: can accurately control the angle of light pattern and light-emitting, light color and soft, non-glare; not mercury, sodium and other elements of the material may be hazardous to health. Built-in micro-processing system can control the luminous intensity, adjusting the light-emitting means to achieve light and art.
5. is beneficial to the environment
For all solid-state LED emitters, earthquake resistance, impact resistance is not easy broken, recyclable waste and no pollution. Small light source, can mix and easy to develop into a short small thin portable lighting products, but also easy to install and maintain.
