LED can directly emit red, yellow, blue, green, cyan, orange, purple, and white light.
LED (Light Emitting Diode), a solid-state semiconductor device that converts electrical energy into visible light, converts electricity directly into light. The heart of the LED is a semiconductor wafer with one end attached to a holder, one end being the negative pole and the other end connected to the anode of the LED power supply, so that the entire wafer is encapsulated by epoxy.
The semiconductor wafer consists of two parts, one part is a P-type semiconductor, in which the hole dominates, and the other end is an N-type semiconductor, which is mainly electrons here. But when the two semiconductors are connected, they form a P-N junction. When a current is applied to the wafer through the wire, the electrons are pushed toward the P region. In the P region, the electrons recombine with the holes, and then the energy is emitted in the form of photons. This is the principle of LED light emission. The wavelength of light, which is the color of light, is determined by the material that forms the P-N junction.
LED can directly emit red, yellow, blue, green, cyan, orange, purple, and white light.
The LED was originally used as an indicator light source for instrumentation. Later, various light-colored LEDs were widely used in traffic lights and large-area displays, resulting in good economic and social benefits. Taking a 12-inch red traffic light as an example, in the United States, a 140-watt incandescent lamp with long-life, low-light performance was used as a light source, which produced 2000 lumens of white light. After passing the red filter, the light loss is 90%, leaving only 200 lumens of red light. In the newly designed lamp, Lumileds used 18 red LED light sources, including circuit losses, to consume 14 watts of electricity, which would produce the same light effect. Automotive signal lights are also an important area for LED light source applications.
For general lighting, people need a white light source. In 1998, white LEDs were successfully developed. This LED is made by encapsulating a GaN chip and yttrium aluminum garnet (YAG). The GaN chip emits blue light (λp=465nm, Wd=30nm), and the Ce3+-containing YAG phosphor prepared by high-temperature sintering is excited by the blue light to emit yellow light, and the peak value is 550n LED lamp m. The blue LED substrate is mounted in a bowl-shaped reflective cavity covered with a thin layer of resin mixed with YAG, about 200-500 nm. The blue portion of the LED substrate is absorbed by the phosphor, and the other portion of the blue light is mixed with the yellow light emitted by the phosphor to obtain white light.
For the InGaN/YAG white LED, by changing the chemical composition of the YAG phosphor and adjusting the thickness of the phosphor layer, white light of various colors having a color temperature of 3500 to 10000 K can be obtained. This method of obtaining white light by a blue LED has the advantages of simple structure, low cost, and high technical maturity, and thus is most used.
1.LED light bar origin
In the 1960s, scientists and technicians developed LED light-emitting diodes using the principle of semiconductor PN junction light. The LED used at that time was made of GaASP, and its luminescent color was red. After nearly 30 years of development, LEDs that are very familiar to everyone have been able to emit red, orange, yellow, green, blue and other colors. However, the white LEDs required for lighting were only developed after 2000. Here, readers will be introduced with white LEDs for lighting.
The earliest application of the LED light source made by the principle of semiconductor P-N junction light was introduced in the early 1960s. The material used at that time was GaAsP, which emits red light (λp = 650 nm). When the driving current is 20 mA, the luminous flux is only a few thousandths of lumens, and the corresponding optical performance is about 0.1 lm/W.
In the mid-1970s, the elements In and N were introduced to produce green light (λp=555 nm), yellow light (λp=590 nm) and orange light (λp=610 nm), and the optical performance was also improved to 1 lm/W.
By the early 1980s, the LED light source of GaAlAs appeared, making the red LED's optical performance up to 10 lumens per watt.
In the early 1990s, the development of two new materials, GaAlInP, which emits red light and yellow light, and GaInN, which emits green and blue light, have greatly improved the optical performance of LEDs.
In 2000, the former made LEDs in the red and orange regions (λp=615nm) with a luminous efficacy of 100 lumens per watt, while the latter made LEDs with a luminous efficacy of 50 lumens in the green region (λp=530nm). /watt.
- 1879 Edison invented the electric light;
- 1938 fluorescent lamps are available;
- 1959 halogen lamp is available;
- 1961 high pressure sodium lamp came out;
—1962 metal halide lamp;
—1969 The first LED light (red);
—1976 green LED light;
—1993 blue LED light;
—1999 white LED light;
—2000 LEDs are used in indoor lighting.
The development of LED is the second revolution in the 120 years since the development of white heat lighting.
- At the beginning of the 21st century, LEDs developed through the wonderful encounter between nature, humans and science will become the innovation of the light world, the green technology light revolution essential to mankind.
—LED will be a renewed light revolution since Edison invented the light bulb.
LED lighting is mainly based on high-power white LED single lamp. The world's top three LED lighting manufacturers are guaranteed for three years. Large particles are greater than or equal to 100 lumens per watt, and small particles are greater than or equal to 110 lumens per watt. Light decay large particles are less than 3% per year, and light decay small particles are less than 3% per year.
LED solar street lights, LED flood lights, LED ceiling lights, and LED fluorescent lamps are already in mass production. For example, a 10 watt LED fluorescent lamp can replace a 40 watt ordinary fluorescent lamp or an energy saving lamp.
More and more LED energy-saving lamps have entered the ordinary people's home, but they are not yet popular!
1. Energy saving: The energy consumption of white LEDs is only 1/10 of that of incandescent lamps and 1/4 of energy-saving lamps.
2, longevity: life expectancy of up to 100,000 hours or more, for ordinary home lighting can be described as "one time and for all."
3, can work in the high-speed state: If the energy-saving lamp is frequently turned on or off, the filament will be black and quickly broken, so it is safer.
4, solid state packaging, is a type of cold light source. So it is very easy to transport and install and can be installed in any miniature and enclosed equipment, not afraid of vibration.
5, led technology is advancing with each passing day, its luminous efficiency is making amazing breakthroughs, and prices are constantly decreasing. The era of a white LED entering the home is coming quickly.
6, environmental protection, no harmful substances of mercury. The assembled components of the LED bulbs can be easily disassembled and assembled, and can be recycled by others without recycling from the manufacturer.
7. Light distribution technology expands the LED point light source into a surface light source, increases the luminous surface, eliminates glare, sublimates the visual effect, and eliminates visual fatigue.
8. The lens and the lampshade are integrated. The lens also has the function of concentrating and protecting, avoiding the repeated waste of light and making the product more simple and beautiful.
9. High-power LED planar cluster package, and integrated design of heat sink and lamp holder. It fully guarantees the heat dissipation requirements and service life of the LED, and fundamentally satisfies the arbitrary design of the structure and shape of the LED lamp, and has the distinctive features of the LED lamp.
10. Energy saving is remarkable. Ultra-bright high-power LED light source, combined with high-efficiency power supply, saves more than 80% of electricity compared with traditional incandescent lamps, and the brightness is 10 times that of incandescent lamps under the same power.
11. The long life is more than 50,000 hours, which is more than 50 times that of traditional tungsten lamps. The LED uses a highly reliable and advanced packaging process - eutectic soldering to fully guarantee the long life of the LED.
12, no strobe. Pure DC operation eliminates visual fatigue caused by stroboscopic lighting.
13, green and environmental protection. It does not contain any pollution elements such as lead and mercury, and it does not pollute the environment.
14, impact resistance, strong anti-light, no ultraviolet (UV) and infrared (IR) radiation. No filament and glass casing, no traditional lamp tube fragmentation problem, no harm to the human body, no radiation.
15. Working under low thermal voltage is safe and reliable. Surface temperature ≤ 60 ° C (at ambient temperature Ta = 25 ° C).
16, wide voltage range, universal LED lights and power supplies. 85V ~ 264VAC full voltage range constant current, to ensure that life and brightness are not affected by voltage fluctuations.
17, using PWM constant current technology, high efficiency, low heat, high constant current accuracy.
18. Reduce line loss and no pollution to the power grid. Power factor ≥ 0.9, harmonic distortion ≤ 20%, EMI meets global indicators, reducing the power loss of the power supply line and avoiding high-frequency interference pollution to the power grid.
19, the universal standard lamp holder can directly replace the existing halogen lamp, incandescent lamp and fluorescent lamp.
20, luminous efficiency rate can be as high as 80lm / w, a variety of LED lights color temperature optional, high color rendering index, good color rendering.
Obviously, as long as the cost of LED lights decreases with the continuous improvement of LED technology. Energy-saving lamps and incandescent lamps are bound to be replaced by LED lamps.
The country is paying more and more attention to lighting energy conservation and environmental protection issues, and has been vigorously promoting the use of LED lamps.
Advantages and disadvantages
* Heat dissipation problem, if the heat dissipation is not good, the life will be greatly shortened.
* The low-end LED lamp is still less energy efficient than the energy-saving lamp (Cold Cathode Tube, CCFL).
* The initial purchase cost is higher.
* Due to the strong directionality of the LED light source, the luminaire design needs to consider the special optical characteristics of the LED.
The following is a comparison of neon lights and LED lights, adding the latest LED technology to compare, not the information that everyone saw in the network before.
1. Does the LED light source have a lifetime of 100,000 hours?
According to the light decay of 7%, the actual only about 50,000 hours. According to the light decay of 3%, the actual application can reach 80,000 hours.
2. Does the LED strip not heat up?
Yes, need to dissipate heat.
3. Can LEDs replace incandescent lamps?
Luminous flux, light efficiency and color rendering can be, but they are too expensive and will not decline in recent years. However, the cost of replacing incandescent lamps can be reduced by increasing the luminous flux of the product.
4. Can LEDs be used simply as ordinary light sources?
No, to drive the power, optical LED lights and heat conduction.
5. Comparison of performance and advantages of two light sources
The advantages of neon have been covered by LEDs, but the price of LEDs is too high.
6. Comparison of power sources for two light sources
LED low voltage is good, but the current is too large. Large particle 1 watt LED single lamp input current is 350mA.
7. Comparison of control techniques for two light sources
LEDs are easy to implement, but neon lights are ripe.
8. Comparison of the stability of the two light sources
The LEDs are inconsistent and the neon lights are quite stable. A few producers can be relatively stable, such as combining CREE with AOD chips to take advantage of their respective chips.
9. Comparison of the prices of the two light sources
LEDs are more expensive, but yellow and red are quite equal. The main expensive is LED white light.
10. Comparison of two kinds of light sources for outdoor use
LED lights can be completely waterproof and dustproof.
11. Comparison of two light source markets
The annual output value of global lighting products is 42 billion US dollars (China's 15 billion US dollars) LED light source is less than 1%.
1 New green environmental protection light source: LED uses cold light source, glare is small, no radiation, no harmful substances are produced during use. The LED has low operating voltage, adopts DC drive mode, ultra-low power consumption (single tube 0.03~0.06W), and the electro-optical power conversion is close to 100%, which is more than 80% energy saving than the traditional light source under the same lighting effect. LEDs have better environmental benefits, no ultraviolet and infrared rays in the spectrum, and waste can be recycled, no pollution, no mercury, and can be safely touched. It is a typical green lighting source.
2 long life: LED is a solid cold light source, epoxy resin package, anti-vibration, there is no loose part in the lamp body, there is no shortcomings such as filament light-emitting, heat deposition, light decay, etc. The service life can reach 60,000~100,000. Hours are more than 10 times the service life of traditional light sources. The LED performance is stable and can work normally in -30~+50°C environment.
3 multi-transformation: LED light source can use the three primary colors of red, green and blue. Under the control of computer technology, the three colors have 256 gray levels and can be mixed arbitrarily, which can produce 256X256X256 (ie 16777216) colors, forming different light colors. The combination. The color of the LED combination is varied, enabling a variety of dynamic changes and various images.
4 High-tech: Compared with the light-emitting effect of traditional light sources, LED light source is a low-voltage microelectronic product, which successfully combines computer technology, network communication technology, image processing technology and embedded control technology. The size of the chip used in the conventional LED lamp is 0.25 mm×0.25 nm, and the size of the LED for illumination is generally 1.0 mm×1.0 mm or more. The LED die-formed work-table structure, inverted pyramid structure, and flip-chip design can improve its luminous efficiency and emit more light. Innovations in LED package design include high-conductivity metal block substrates, flip-chip designs, and bare-plate cast leadframes. These methods can be used to design high-power, low-thermal resistance devices, and these devices have higher illumination than conventional LEDs. The illuminance of the product is greater.
A typical high-throughput LED device can generate lumens of several lumens to tens of lumens, and an updated design can integrate more LEDs in a single device or install multiple devices in a single assembly, resulting in equivalent lumens output. For small incandescent lamps. For example, a high-power 12-chip monochrome LED device can output 200 lm of light energy, which consumes between 10 and 15 W.
The application of LED light source is very flexible, and it can be made into light, short and short products of various forms such as point, line and surface. The control of LED is very good. As long as the current is adjusted, it can be dimmed at will; the combination of different light colors is multi-end, and the timing control circuit is utilized. , can achieve a variety of dynamic changes. LEDs have been widely used in a variety of lighting equipment, such as battery-powered flashlights, miniature voice-activated lights, safety lights, outdoor road and indoor stair lights, and buildings and marked continuous lights.