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LED light source lighting technology and lighting applications
- May 12, 2017 -

LED light source in the field of lighting applications, semiconductor light-emitting technology is the rapid development of technology and "green lighting" concept gradually deeply rooted in the product. "Green lighting" is the field of foreign lighting in the late 80s put forward a new concept, China's "green lighting project" began in 1996. An important step in achieving this plan is to develop and promote efficient, energy-efficient lighting fixtures, save lighting electricity, reduce environmental and light pollution, and build a lighting system that is cost-effective, economical and safe, safe and reliable and environmentally friendly.

First, LED lighting concept

LED (Lighy Emitting Diode), also known as light-emitting diodes, they use solid semiconductor chip as a luminescent material, when the two ends with forward voltage, the carrier in the semiconductor compound, the release of excess energy caused by photon emission generated visible light.

(A) LED development history

Application of semiconductor P N light source principle made LED produced in the early 1960s, 1964 first appeared red light-emitting diodes, followed by yellow LED. Until 1994 blue, green LED was developed successfully. 1996 by the Japanese company Nichia (Japan) successfully developed a white LED. LED is characterized by its inherent characteristics, such as power saving, long life, vibration resistance, fast response, cold light source and other characteristics, widely used in light, lights, displays, landscape lighting and other fields, in our daily life everywhere , Household appliances, telephones, dashboard lighting, car fog lights, traffic lights and so on. But because of its poor brightness, expensive and other conditions, can not be used as a general purpose light source.

In recent years, with the continuous development of semiconductor luminescent materials, LED manufacturing process of continuous progress and new materials (nitride crystals and phosphor) development and application of various colors of ultra-high brightness LED has made a breakthrough Progress, its luminous efficiency increased by nearly 1000 times, the color has been achieved in the visible light band of all colors, the most important of which is the emergence of ultra-high brightness white LED, LED applications across the field to high efficiency lighting market become possible. It has been pointed out that high brightness LED will be one of the greatest inventions of mankind after Edison invented incandescent bulbs.

(B) LED light principle

The light-emitting diode is mainly composed of PN junction chip, electrode and optical system. Its luminous body - wafer area of 10.12mil (1mil = 0.0254 square millimeters), the current international large-chip LED, the chip area of 40mil.

The light-emitting process consists of three parts: forward bias under the carrier injection, composite radiation and light energy transmission. The tiny semiconductor wafer is encapsulated in a clean epoxy resin, and when the electron passes through the wafer, the negatively charged electron moves to the positively charged hole region and recombines with the electrons and holes disappearing to produce photons. The greater the energy (bandgap) between electrons and holes, the higher the energy of the generated photons. The energy of the photon in turn corresponds to the color of the light, the spectrum of visible light, the blue light, the purple light carrying the most energy, orange light, red light carrying the least energy. Since different materials have different band gaps, it is possible to emit light of different colors.

The mainstream of LED lighting will be high brightness white LED. At present, the commercialized white LED is more than two wavelengths, that is, blue single-chip plus YAG yellow phosphor mixed to produce white light. The future is more optimistic about the three wavelengths of white LED, that is, inorganic UV chip with red, blue, green three-color phosphor mixed with white light, it will replace the fluorescent lamps, compact energy-saving fluorescent bulbs and LED backlight market.

(C) the basic characteristics of LED light source

1, luminous efficiency is high

LED after several decades of technical improvements, its luminous efficiency has been greatly improved. Incandescent lamp, halogen light effect of 12-24 lumens / watt, fluorescent lamp 50 ~ 70 lumens / watt, sodium lamp 90 ~ 140 lumens / watt, most of the power consumption into heat loss. LED light effect will be improved to reach 50 to 200 lumens / watt, and its light monochromatic, narrow spectrum, without filtering can be issued directly colored visible light. At present, countries around the world are stepping up efforts to improve LED light efficiency, in the near future its luminous efficiency will be greater improvement.

2, less power consumption

LED single tube power 0.03 ~ 0.06 watts, using DC drive, single tube drive voltage 1.5 ~ 3.5 volts, current 15 ~ 18 mA, the reaction speed, can be operated at high frequencies. The same lighting effect of the case, the power consumption is one-eighth of incandescent bulbs, fluorescent tubes one-half, Japan estimates that, such as the use of light efficiency than fluorescent lamps to double the LED instead of half of Japan's incandescent and Fluorescent light. Saving about 6 billion liters of crude oil per year. On the bridge guardrail light case, the same effect of a fluorescent lamp 40 watts, and the use of LED power each only 8 watts, and can change colorful.

3, long service life

The use of electronic light field radiation light, filament light burning, heat deposition, light attenuation and other shortcomings. The use of LED lights small size, light weight, epoxy resin package, can withstand high-strength mechanical shock and vibration, not broken. The average life expectancy of 100,000 hours. LED lamp life of up to 5 to 10 years, can greatly reduce the maintenance costs of lamps and lanterns to avoid the pain.

4, safety and reliability

Low heat, no heat radiation, cold light source, you can safely touch: to accurately control the light and light angle, light color soft, no glare; no mercury, sodium and other substances may be harmful to health. Built-in micro-processing system can control the luminous intensity, adjust the light way to achieve the combination of light and art.

5, is conducive to environmental protection

LED for the solid solid body, shock, impact resistance is not broken, waste can be recycled, no pollution. Light source is small, can be arbitrarily combined, easy to develop into light and thin small lighting products, but also easy to install and maintain.