First, the characteristics of LED lights:?
LED lamp bead is a kind of semiconductor, belonging to light emitting diode, which can convert electric energy into light energy. It changes the principle of incandescent tungsten filament luminescence and energy-saving lamp tricolor powder luminescence, and adopts electric field luminescence. The LED lamp can adopt DC-DC DC220V voltage without up-converter and ballast. Short start-up time, no flash frequency. ? The main features of LED lamps are:
① New green light source: LED adopts cold light source, with less glare, no radiation and no harmful substances in use. LED has low working voltage, DC drive, ultra-low power consumption (single tube 0.03~0.06W), and electro-optical power conversion is close to 100%, which saves more than 80% energy compared with traditional light sources under the same lighting effect. LED has better environmental benefits, no ultraviolet and infrared rays in the spectrum, recyclable waste, no pollution, no mercury, safe to touch, and it is a typical green lighting source.
② Long service life: LED is a solid cold light source, encapsulated by epoxy resin, which is vibration-resistant. There are no loose parts in the lamp body, and there are no shortcomings such as easy combustion, thermal deposition and light decay. The service life can reach 60,000 ~ 65,438+10,000 hours, which is more than 10 times of the traditional light source. LED has stable performance and can work normally in the environment of -30~+50oC.
③ Multi-transformation: LED light source can make use of the principle of three primary colors of red, green and blue, and under the control of computer technology, make the three colors have 256 gray levels and mix them at will, thus producing 256X256X256 colors (i.e. 167772 16) and forming different combinations of light colors. The light color of LED combination is changeable, which can realize colorful dynamic change effect and various images.
④ High-tech: Compared with the traditional light source, LED light source is a low-voltage microelectronic product, which successfully integrates computer technology, network communication technology, image processing technology and embedded control technology. The chip size used in traditional LED lamps is 0.25mmX0.25nm, while the size of lighting LED is generally above1.0mmx1.0mm. The desktop structure, inverted pyramid structure and flip chip design of LED die can improve its luminous efficiency, thus emitting more light. The innovations of LED packaging design include high conductivity metal block substrate, flip chip design and bare die-casting lead frame. These methods can be used to design devices with high power and low thermal resistance, and the illumination of these devices is higher than that of traditional LED products.
Second, the main parameters of LED lamp products:?
Luminous flux (in LM) and color rendering index (in Ra)? , color temperature (unit: K), power factor (unit: PF), heat dissipation capacity?
(1) luminous flux: mainly refers to the brightness of the product. Lamps emit light energy by consuming electric energy. The greater the luminous flux, the more light energy they emit. Therefore, it is an index to characterize the luminous ability of light source. When the power consumption of two lamps is the same, the greater the luminous flux, the better. General LED lights can reach 90- 1 10LM/W in time? Good lamps can even reach 120- 150 lm/w, (traditional incandescent lamps? 10- 15LM/W energy-saving lamps 30-65LM/W)?
② Color rendering index: Color rendering index refers to the ability to reproduce a color. The higher the color rendering index, the more positive the color. By comparing the appearance color of an object with a reference or reference light source (incandescent lamp or painting lamp) with the same color temperature. A light source with high color rendering index, close to 100, is needed to restore the true color of the object and correctly express the original color of the material, with the best color rendering. Incandescent lamp 97- 100LED lamp 85- 12
③ Color temperature: refers to the color emitted by light. The higher the color temperature, the bluer the light emitted and the lower the color temperature. The light is red. It is the reference standard of Ethernet sunlight. There are three general color temperatures. ? Warm light (yellow light) 2700-3500K symbol: RN. Neutral white? 4300-5000K？ Representative compliance: RZ? White light (cold white) 5800-6500K? Representative symbol: RR.
The specific color temperature chart is as follows:
④ Power factor: and power compensation of power conversion light source. The power factor depends on the power factor of the driving power supply. The greater the power factor, the better the conversion efficiency.
⑤ Heat dissipation capacity:? The heat dissipation capacity of LED products directly affects the service life and light decay rate of products. Products with higher power and longer lighting time have higher requirements for heat dissipation. Traditional LED products will use metal shell and built-in or external radiator to dissipate heat for lamps.
Third, the comparison of energy saving between LED products and traditional incandescent lamps
Suppose that the total brightness requirement of a place or a family to meet its lighting needs is: 900- 1200LM* 10.
2. Basic knowledge of 2.LED
First, the structure and luminous principle of LED 50 years ago, people knew the basic knowledge that semiconductor materials can produce light. The first commercial diode was produced in 1960. LED is the abbreviation of English light emitting diode. Its basic structure is an electroluminescent semiconductor material, which is placed on a shelf with leads and then sealed with epoxy resin. It plays a role in protecting the inner core wire, so the LED has good seismic performance. As shown in the following figure, the core part of LED is a wafer composed of P-type semiconductor and N-type semiconductor, and there is a transition layer between P-type semiconductor and N-type semiconductor, which is called pn junction. In the PN junction of some semiconductor materials, the injected minority carriers will release excess energy in the form of light when they recombine with the majority carriers. So as to directly convert electric energy into light energy. When reverse voltage is applied to PN junction, minority carriers are difficult to inject, so they do not emit light. This kind of diode made by injection electroluminescence principle is called light emitting diode, commonly known as led. When working in the forward direction (that is, DC voltage is applied at both ends), when the current flows from the anode of the LED to the cathode, the semiconductor crystal emits different colors of light from ultraviolet to infrared, and the intensity of light is related to the current. Features of LED light source: 1. Voltage: LED uses low-voltage power supply, the power supply voltage is between 6-24V, which varies according to different products, so it is safer than using high-voltage power supply, especially suitable for public places. 2. Efficiency: Compared with incandescent lamps with the same light efficiency, the energy consumption is reduced by 80%. 3. Applicability: Very small, each unit LED chip is a square of 3-5 mm, so it can be made into devices with various shapes, which is suitable for changing environments. 4. Stability: 654.38+ million hours, and the light attenuation is 50% of the initial value. 5. Response time: The response time of incandescent lamp is milliseconds, and that of LED lamp is nanoseconds. 6. Environmental pollution: no harmful metal mercury. 7. Color: Light-emitting diodes can change color by changing current, and light-emitting diodes can be easily modified by chemical methods. Adjust the energy band structure and band gap of the material to realize red, yellow, green, blue and orange multicolor luminescence. For example, with the increase of current, the red LED can turn orange, yellow and finally green. 8. Price: LEDs are more expensive. Compared with incandescent lamps, the price of several LEDs can be equivalent to the price of an incandescent lamp. Usually, each group of signal lamps needs to be composed of 300~500 diodes. Types and development history of monochromatic LEDs The earliest LED light source based on semiconductor P-N junction light-emitting principle appeared in the early 1960s. The material used at that time was GaAsP, which emitted red light (λp=650nm). When the driving current is 20 mA, the luminous flux is only a few thousandths of lumens, and the corresponding luminous efficiency is about 0. 1 lumen/watt. In the mid-1970s, in and n elements were introduced. LED can produce green light (λp=555nm), yellow light (λp=590nm) and orange light (λp=6 10nm), and the light efficiency is also improved to 1 lumen/watt. In the early 1980s, the LED light source of GaAlAs appeared, which made the light efficiency of red LED reach 10 lumen/watt. The successful development of two new materials GaInN for blue light has greatly improved the light efficiency of LED. In 2000, the light efficiency of the LED made of the former reached 100 lumens/watt in red and orange regions (λp=6 15nm), while the light efficiency of the LED made of the latter reached 100 lumens/watt in green regions (λp=530nm). Application of Monochrome LED Initially, LED was used as the indicating light source of instruments and meters. Later, various colors of light-emitting diodes were widely used in traffic lights and large-area display screens, which produced good economic and social benefits. Take 12 inch red traffic lights as an example. In the United States, the first light source used was 140W incandescent lamp with long life and low light efficiency. It produces 2000 lumens of white light. After passing through the red filter, the light is lost by 90%, leaving only 200 lumens of red light. In the newly designed lamps, Lumileds Company adopted 18 red LED light sources, including circuit loss, * * * consumption 14 watt, which can produce the same light effect. Car signal lamp is also an important field of LED light source application, and China began to install high-position brake lights on cars. Since the response speed of LED is fast (nanosecond level), the driver who follows the vehicle can know the driving situation as soon as possible, thus reducing the occurrence of rear-end collision accidents .56616.66666666665 In addition, LED lamps have been used in outdoor red, green and blue full-color display screens, push-button miniature flashlights and other fields. Fifth, the development of white LED: For general lighting, people need a white light source. 1998 has successfully developed a white LED. This kind of LED is made by packaging GaN chip and YAG. The GaN chip emits blue light (λp=465nm, Wd=30nm), and the high-temperature sintered YAG phosphor containing Ce3+ emits yellow light after being excited by this blue light. The peak value is 550 nm. The blue LED substrate is installed in the bowl-shaped reflection cavity and covered with a thin layer of YAG-mixed resin, about 200-500 nm. Part of the blue light emitted by the LED substrate is absorbed by the phosphor, and the other part is mixed with the yellow light emitted by the phosphor to obtain white light. Now for InGaN/YAG white led, by changing the chemical composition of YAG phosphor and adjusting the thickness of phosphor layer, various white lights with color temperature of 3500- 10000K can be obtained. Among LED manufacturers, Nichia Chemical took the lead in developing high-brightness LEDs with different wavelengths and blue-violet semiconductor lasers (laser diodes; LD), a heavyweight manufacturer with blue LED patents in the industry. After obtaining a number of basic patents such as blue LED production and electrode structure, Niya Chemical insists on not providing authorization to the outside world, and only adopts its own production strategy with the intention of monopolizing the market, which makes blue LED expensive. But other manufacturers with capacity are quite dissatisfied. Some Japanese LED manufacturers believe that Niya Chemical's strategy will enable Japan to compete in the field of blue LED and white LED. LED manufacturers in Europe, America and other countries will gradually seize the opportunity, causing serious damage to the overall LED industry in Japan. Therefore, many manufacturers will do everything possible to develop and produce blue LEDs. At present, in addition to Niya Chemical and Sumitomo Electric, there are Toyota Synthetic, Romu, Toshiba and Sharp, and American manufacturers Cree, Singular, Philips, Osram, HP, HP, Siemens, Research and EMCORE have all invested in the research and production of this product.
3. Who can tell me the basic knowledge of LED display?
LED (Light Emitting Diode) is a solid-state semiconductor device, which can directly convert electricity into light.
The heart of LED is a semiconductor chip, one end of which is attached to the bracket, one end is the negative electrode, and the other end is connected to the positive electrode of power supply, so that the whole chip is encapsulated by epoxy resin. The semiconductor wafer consists of two parts, one is a P-type semiconductor, in which holes are dominant, and the other is an N-type semiconductor, mainly electrons.
But when these two semiconductors are connected together, a "pn junction" is formed between them. When the current acts on the chip through the wire, the electrons will be pushed to the P region, where they will recombine with holes and then release energy in the form of photons, which is the principle of LED light emission.
The wavelength of light determines the color of light, and the color of light is determined by the material that constitutes the pn junction. LED is a semiconductor that can convert electric energy into light energy. It changes the principle of incandescent tungsten filament luminescence and energy-saving lamp tricolor powder luminescence, and adopts electric field luminescence.
According to the analysis, the characteristics of LED are very obvious, such as long life, high light efficiency, no radiation and low power consumption. The spectrum of LED is almost completely concentrated in the visible light band, and the luminous efficiency can exceed 150lm/W(20 10 years).
Comparing LED with ordinary incandescent lamp, spiral energy-saving lamp and T5 tricolor fluorescent lamp, the results show that the light efficiency of ordinary incandescent lamp is 1.2 lm/w, and its service life is less than 2000 hours. The power of spiral energy-saving lamp is 60lm/W, and its service life is less than 8000 hours. The power of T5 fluorescent lamp is 96lm/W, its life is about 1000 hours, and its diameter is 5 mm. It is also predicted that the upper limit of LED life will be infinite in the future.
However, the working principle of LED lamps makes the heat dissipation problem very prominent in the high-power LED lighting industry. Many LED lighting schemes do not pay enough attention to heat dissipation, or their technical level is limited. Therefore, the actual service life of high-power LED lamps in mass production is far less than the theoretical value, and the cost performance is higher than that of traditional lamps. In order to prolong the service life of LED lamps and truly make them suitable for commercial mass production, the LED lighting industry is stepping up its efforts to develop new heat-conducting materials such as heat-conducting plastics independently or in cooperation with professional heat-conducting material suppliers.
High power, generally above 0.65W, will have different standards within different companies, because there is no recognized industry standard in the field of high-power LED. The ratio of light intensity to lumen is small, but the heat dissipation is also large. At present, high power is mostly used in a single application, and the effective heat dissipation area is large, so the integrated LED lamp matrix appears, but the heat dissipation effect is not very good.
The low power is generally around 0.06W W W. At present, LED flashlights are generally used at low power, and the light does not diverge, which is divided into large angle and small angle depending on the light emitting angle of LED. Small angles don't spread, big angles only spread.
Flashlights on the market are generally made of straw hats. The effect is very good.
Now I'm worried that some manufacturers don't pay attention to quality and use inferior LEDs as flashlights. It won't be long before there are dead lights. The brightness of LED must be related to the light emitting angle of LED. The smaller the LED angle, the higher the brightness. Nothing is super bright, it's a lie to children. If it is a good quality LED, no matter which LED manufacturer produces it, everyone's brightness is similar, but the production process is different and the service life is slightly different. Because everyone uses those foreign LED chips. If it is a 5MM LED with an angle of 180 degrees, the brightness of white light is only a few hundred MCD. If it is an angle of 15 degrees, it will reach the brightness of 1 10,000 to 20,000 MCD, and the brightness difference is dozens of times. If it is used for lighting, it is best to use high-power LED outdoors, with higher brightness and single power of 65438+. 5W, and some are several high-power LED, and the power can reach several hundred. Color temperature has nothing to do with brightness, while brightness is related to lumen value. Let's look at several related concepts: luminous flux (lm) Because human eyes have different sensitivities to electromagnetic waves of different wavelengths, we can't directly measure light energy by the radiation power or radiation flux of light sources, but must use the unit based on human eyes' perception of light-luminous flux.
The luminous flux is indicated by the symbol φ, and the unit is lumen (lm). Luminous intensity (cd) luminous flux is the total light energy emitted by a light source to the surrounding space.
The spatial distribution of luminous flux emitted by different light sources is different. The unit of luminous intensity is Candeira, and the symbol is cd, which indicates the luminous flux emitted by the light source within the unit spherical solid angle (the angle formed by the surface of the object and the point light source).
1CD =1lm/1Sr (Sr: spherical unit of solid angle). Brightness (cd/m2) Brightness is the intensity of light emitted by an object seen by the eyes from a certain direction.
The unit is Candeira /m2 [cd/m2], and the symbol is L, which indicates the luminous flux of the luminous body in the unit area of the solid angle in a specific direction, which is equal to the luminous intensity emitted by 1 Candeira from the surface of 1 m2. Color temperature When the color of light emitted by a light source is the same as the color radiated by a blackbody at a certain temperature, the temperature of the blackbody is called the color temperature of the light source, which is expressed by the absolute temperature k (Kelvin = Celsius +273. 15).
Color rendering in principle, artificial light should be the same as natural light, so that people can correctly distinguish the color of things with the naked eye. Of course, it depends on the location and purpose of lighting. The degree to which a light source presents the color of an object is called color rendering.
Commonly referred to as "color rendering index" (Ra). Color rendering refers to the relationship between the true color of things (their own color) and the color displayed under a standard light source.
The determination of Ra value is to compare eight test colors defined in DIN6 169 standard with the measured light source. The smaller the color difference, the better the color rendering of the test light source color. A light source with Ra value of 100 indicates that the color displayed by things under its light is the same as that under the standard light source.
Edit the basic information of this paragraph.
4. Tips for using 4.LED lights.
Excerpted from Shandong Prius Lighting official website.
LED installation method
(1) Pay attention to the arrangement of external lines of various devices to prevent polarity installation errors. The equipment should not be too close to the heating element, and the working conditions should not exceed the specified limits.
(2) Never install the LED under the condition that the pin is deformed.
(3) When deciding to install in the hole, calculate the size and tolerance of the hole spacing between the surface and the circuit board to avoid excessive stress on the bracket.
(4) When installing the LED, Jane uses the guide sleeve for positioning.
(5) Before the welding temperature returns to normal, the LED must be protected from any vibration or external force.
What should I pay attention to when cleaning LED?
Special care must be taken when cleaning colloid with chemicals, because some chemicals will damage the surface of colloid and cause discoloration, such as trichloroethylene and acetone. Wipe with ethanol at room temperature and soak for no more than 3 minutes.
Proper working and storage temperature of LED:
(1)LED light-emitting diode Topr-25℃~85℃, Tstg-40℃~ 100℃
(2)LED display temperature Topr-20℃~70℃, Tstg-20℃~85℃
(3) outdoor LED lamp pixel tube Topr-20℃~60℃, Tstg-20℃~70℃
The common sense of LED product application and LED performance test is as follows:
(1) soldering iron: the tip temperature of soldering iron (maximum 30W) shall not exceed 300℃; The welding time shall not exceed 3 seconds; The welding position is at least 2mm away from the colloid.
(2) Immersion welding: the highest temperature of immersion welding is 260℃; Immersion welding time shall not exceed 5 seconds; The immersion welding position is at least 2mm away from the colloid.
Lead forming method:
(1) The bending bracket must be 2 mm away from the colloid.
(2) The forming of the bracket must be completed by a fixture or a professional.
(3) The forming of the bracket must be completed before welding.
(4) The forming of the bracket shall ensure that the pins and spacing are consistent with those on the circuit board.
5. What are the basic knowledge of 5.LED module?
LED module is a product made of LEDs (light emitting diodes) arranged together according to certain rules and then packaged, plus some waterproof treatment.
LED modules are widely used in LED products, and there are also great differences in structure and electronics. Simply put, it is an LED module with a circuit board and a shell, and it is complicated to add some controls, constant current sources and related heat dissipation treatments to make the LED life and luminous intensity better. Mainly used to show the night effect of advertising fonts (acrylic, plastic) and logos. Installed on the top or wall of a building, with words or signs as the media, it can not only show the daytime effect of signs, but also show another effect with led as the light source at night. Using LED lighting application control system, characters or signs can be dynamically controlled through video. In some places with strong entertainment atmosphere, LED light source module has become one of the most important choices for enterprises to show their self-image.
(1) color:
This is a basic parameter, and different colors are used in different occasions. According to the color category, it can be divided into three types: monochrome, seven-color and full-color single-point control. Monochrome is a single color and cannot be changed. Just plug it in and it will work. Colorful means that the whole string of modules can only have the same color, but not different colors for a single module. Simply put, all modules can only achieve the same color at the same time, and can change between seven colors at different times. Full color single point can control the color of each module, and when the number of modules reaches a certain level, the effect of displaying pictures and videos can be realized. Seven-color and full-color single point can only be realized by adding control system. We introduce the selection and application of control system in detail in the chapter of control system.
(2) Voltage:
This is a very important parameter. At present, 12V low-voltage module is more common. When connecting the power supply and the control system, it is necessary to check the correctness of the voltage value before powering on, otherwise the LED module will be damaged.
(3) Working temperature:
That is to say, the temperature at which the LED works normally. Usually the temperature is between -20℃ and +60℃, and special treatment is needed if the requirements are high.
(4) Luminous angle:
The light-emitting angle of lensless LED module is mainly determined by LEDs, and different LEDs have different light-emitting angles. The LED lighting angle provided by general manufacturers is the angle of LED module.
(5) brightness:
This parameter is a parameter that people pay more attention to. Brightness is a complex problem in LED. We usually refer to the brightness in LED module as luminous intensity and luminosity. At low power, it is often called luminous intensity (MCD), and at high power, it is often called luminosity (LM). The module luminosity we are talking about only adds up the luminosity of each LED. Although it is not very accurate, it can basically meet the requirements.
(6) Waterproof grade:
If the LED module is to be used outdoors, this parameter is very important, and it is an important indicator to ensure whether the LED module can work outdoors for a long time. Usually outdoors, the waterproof grade is preferably IP65.
(7) Size:
This is relatively simple, that is, the size of length, width and height.
(8) Maximum length of a single connection:
This parameter is often used in large-scale projects, indicating the number of LED modules connected in series. This is related to the size of the LED module connection line. It should also be customized according to the actual situation.
(9) Power:
An empirical formula of LED module power: LED module power = single LED power ⅹ number of LEDs ⅹ 1. 1.
6.LED industry knowledge
MOCVD Metal Organic Chemical Vapor Deposition (MOCVD), 1968, is a new technology for preparing compound semiconductor single-layer films proposed by Rockwell Company of the United States.
The equipment integrates many disciplines such as precision machinery, semiconductor materials, vacuum electronics, fluid mechanics, optics, chemistry and computer. It is a special equipment with high automation, high price and high technical integration. It is mainly used for epitaxial growth of gan-based semiconductor materials and the manufacture of blue, green or ultraviolet light-emitting diode chips. It is also one of the most promising special equipment in photoelectric industry. The basic principle of LED epitaxial wafer growth before LED chip production is that on the substrate (mainly sapphire, sic, Si) heated to a proper temperature, the gaseous substance InGaAlP is transported to the surface of the substrate in a controllable way to grow a specific single crystal film.
At present, the growth technology of LED epitaxial wafer mainly adopts organic metal chemical vapor deposition (MOCVD). The success of epitaxial wafer technology requires the following three conditions: 1. Accurate mastery of equipment.
Due to the high cost of MOVCD, maintenance cycle and adequate preparation of accessories are very important. 2. To master the principle of epitaxy, the growth of materials needs three basic skills: physics, materials science and analytical technology. If you can master these skills, you will have some ability to grow materials.
3. Adhere to the experimental spirit, and the epitaxial results need to wait persistently, because in addition to the basic analysis, the observation and recording of the results, and the analysis of the results of LED chips need patience and perseverance. The production process of LED chips is complicated: 1. After the epitaxial wafer is displayed, 9 points are randomly selected from each epitaxial wafer for testing.
Those that meet the requirements are good products, others are bad products (large voltage deviation, short wavelength, etc. ) .2. The epitaxial wafer of a good product should be used as the electrode (P-pole, N-pole).
Next, the epitaxial wafer is cut by laser, and then sorted by 100%, and the LED chip (square wafer) is formed by automatic sorting according to different voltages, wavelengths and brightness. 3. Finally, visually inspect and sort out the defective or worn electrodes, that is, the crystals scattered behind.
At this time, there are chips on the blue film that do not meet the shipping requirements, and these become edge films or rough films. Generally, the epitaxial wafers of defective products are directly used as electrodes (P and N poles) without sorting. These are LED round chips currently on the market.