LED flashlight
Light-emitting diodes are made of III-IV compounds, such as semiconductors such as GaAs (gallium arsenide) and GAAP (gallium phosphide), and their core is a PN junction. Therefore, it has the I-N characteristics of general pn junction, that is, forward conduction, reverse cutoff and breakdown characteristics. In addition, under certain conditions, it also has luminous characteristics. Under DC voltage, electrons are injected from N region to P region, and holes are injected from P region to N region. Part of minority carriers (minority carriers) entering the opposite area and majority carriers (multi-carriers) compound to emit light, as shown in figure 1. Assuming that luminescence occurs in the p region, the injected electrons directly combine with valence band holes to emit light, or are first captured by the luminescence center and then combined with holes to emit light. In addition to this luminescence recombination, some electrons are captured by the non-luminescence center (this center is near the middle of the conduction band and the dielectric band) and then recombine with holes, and the energy released each time is not large enough to form visible light. The greater the ratio of luminous recombination to non-luminous recombination, the higher the quantum efficiency of light. Because recombination emits light in the minority carrier diffusion region, light is generated only within a few microns near the surface of the PN junction. It is proved by theory and practice that the peak wavelength λ of light is related to the band gap width Eg of semiconductor materials in the light-emitting region, that is, the unit of Eg in λ≈ 1240/Eg(mm) is electron volts (eV). If visible light (purple light with a wavelength of 380nm to red light with a wavelength of ~780nm) can be generated, the Eg of the semiconductor material should be between 3.26 ~ 1.63 EV. Light with a longer wavelength than red light is infrared light. At present, there are four kinds of light emitting diodes: infrared, red, yellow, green and blue, but the blue light emitting diode is expensive and not widely used.
Edit the LED dimming control in this section.
Traditionally, the dimming of LED is realized by adjusting the forward current in LED with DC signal or filtered PWM. Reducing LED current will adjust the light output intensity of LED, however, the change of forward current will also change the color of LED, because the chromaticity of LED will change with the change of current. Many applications (such as automobile and LCD TV backlight lighting) do not allow any color drift of LED. In these applications, a wide range of dimming is necessary, because there are different light changes in the surrounding environment, and human eyes are sensitive to small changes in light intensity. Controlling the brightness of the LED by applying PWM signal allows the dimming of the LED to be completed without changing the color. People often say that PWM dimming is to use a PWM signal to adjust the brightness of LED. There are three commonly used methods to adjust LED brightness: (1) Using setting resistors, connecting different conversion resistors in parallel at both ends of LED drive control IC pin RSET, and using a DC voltage to set the current of LED drive control IC pin RSET, so as to change the forward working current of LED and achieve the purpose of adjusting LED brightness. (2) Using PWM technology and PWM control signal, the luminous brightness of LED is adjusted by controlling the duty ratio of LED forward working current. (3) The simplest method of linear adjustment is to use external setting resistor in LED drive control C to realize LED dimming control. Although this dimming control method is effective, it lacks flexibility and cannot allow users to change the light intensity. Linear adjustment will reduce the efficiency and lead to the color shift of white LED to yellow spectrum. This may be a slight deviation, but it can be detected in sensitive applications. Using digital or PWM LED dimming control method, the pulse duty ratio of LED driving current is changed by pulse width modulation, and the switching frequency is greater than 100HZ. Switching dimming control frequency greater than 100HZ is mainly used to avoid human eyes from feeling dimming flicker. Under the PWM dimming control of LED, the luminous brightness of LED is directly proportional to the pulse duty ratio of PWM. Under this dimming control mode, the luminous color of LED can remain unchanged in the range of high brightness ratio, and the dimming ratio range of LED dimming control with PWM can reach 3000: 1. The dimming control method of linear LED adopts analog dimming control method. Under the analog dimming control, the LED dimming control is realized by adjusting the LED forward working current, and the dimming control range can reach 10: 1. If we want to further reduce the forward working current of LED, it will cause some problems, such as the color of LED will change, and the forward working current of LED cannot be accurately regulated.
Edit the operation parameters and efficiency of this part.
Generally speaking, the most common LED operating power is set below 30 to 60 milliwatts. 1999 introduced commercial-grade LED, which can be used continuously under the power input of1w. These LEDs use oversized semiconductor chips to deal with the problem of high power input, and the semiconductor chips are fixed on metal iron sheets to help dissipate heat. In 2002, 5-watt LED began to appear on the market, and its efficiency was about 18 to 22 lumens per watt. In September 2003, Cree, Inc. demonstrated its new blue LED, which achieved 35% lighting efficiency at 20 mA. They also made a white LED product with 65 lumens per watt, which was the brightest white LED on the market at that time. In 2005, they demonstrated the prototype of white LED, which achieved a recording efficiency of 70 lumens per watt in a working environment of 350 mA. Nowadays, the working efficiency of organic light-emitting diodes is much lower than that of ordinary LEDs, and the highest is only about 10%. However, the production cost of organic light emitting diodes is much lower. For example, a large array of organic light-emitting diodes can be placed on the screen by a simple printing method to make a color display screen.
Edit the LED pull-up resistor in this section.
Generally, when an LED works, adding 10mA is enough to make it work normally, so the resistance value is Vo/ 10mA, and Vo is the value of external resistance. For example, a resistance of 500 ohms can be used at a voltage of +5V.
Led display control system
Simply put, it is divided into: synchronous control system (synchronous with computer output); Asynchronous off-line control system (control card stores content and runs off-line) With the rapid development of LED display screen in recent two years, the market of LED control system has also become broader, especially the newly built Vida USB flash drive LED control card in 2009 is currently used the most. Vida USB flash drive LED control card can be connected to a computer through a serial port, and can also be used to transmit information, saving computers, avoiding wiring, supporting analog clocks and flowing borders. Vida USB flash drive LED control card is suitable for all kinds of indoor and outdoor display screens, and has been popular all over the country since its listing. LED control card
The development of LED display screen has gradually entered the civilian use, such as the door head screen used in various stores, various square screens indoors and outdoors, and other various strip screens. At present, computers must be connected to the display screen to update content, which makes it difficult for a large number of users, especially advertisers, to update programs. The USB flash drive LED control card solves this problem. Using USB flash drive, the most common and cheapest information transmission medium, users can update the displayed content by editing the content with the help of Internet cafes, home or friends' computers. The USB flash drive doesn't need to be plugged into the display screen or its extension cord all the time. After plugging in, the information will be stored in the screen for a few seconds, and the USB flash drive can be pulled out. The USB flash drive LED control card has a common serial communication function, and users can directly connect with the computer if they want to communicate directly. U disk is used to transmit the contents of LED display screen, and has been gradually applied to LED display screens all over the country. LED display control card, also known as LED asynchronous controller, is the core component of LED graphic display. Responsible for receiving picture display information from computer serial port, putting it into frame memory, and generating serial display data and scanning control sequence required by LED display screen according to partition driving mode. The LED display screen mainly displays various characters, symbols and graphics. Screen display information is edited by computer, preloaded into the frame memory of LED display screen through RS232/485 serial port, and then displayed and played screen by screen, in a cycle. The display mode is rich and colorful, and the display screen works offline. LED display screen is widely used in various industries because of its flexible control, convenient operation and low cost.
Edit the classification of this paragraph.
1. According to the luminous color of LED, it can be divided into red, orange, green (subdivided into yellow-green, standard green and pure green) and blue light. In addition, some LEDs contain chips of two or three colors. According to whether light-emitting diodes are doped with scatterers, colored or colorless, light-emitting diodes of the above colors can be divided into four types: colored transparent, colorless transparent, colored scattering and colorless scattering. Scattering LEDs and LEDs are used as indicator lights. 2. According to the light-emitting surface characteristics of LED, it can be divided into round lamp, square lamp, rectangle, surface LED, side tube, micro tube for surface mounting, etc. The diameter of circular lamp is divided into φ2mm, φ4.4mm, φ5mm, φ8mm, φ 10mm and φ20mm. In foreign countries, light-emitting diodes with a diameter of 3 mm are usually marked as T-1; φ5mm is marked as t-1(3/4); Write φ4.4mm as T- 1( 1/4). The angular distribution of circular light intensity can be estimated by half-value angle. From the angle distribution diagram of luminous intensity, there are three types: (1) high directivity. Generally, it is a pointed epoxy package or a package with a metal reflective cavity, and no scattering agent is added. The half-value angle is 5 ~ 20 or less, which has high directivity and can be used as a local lighting source or combined with a photodetector to form an automatic detection system. (2) standard type. Usually used as an indicator light, its half-value angle is 20 ~ 45. (3) Scattering type. This is an indicator lamp with a large viewing angle, with a half-value angle above 45 ~ 90, and a large number of scattering agents. 3. According to the structure of LED, there are full epoxy package, metal-based epoxy package, ceramic-based epoxy package and glass package. 4. According to the luminous intensity and working current, there are LEDs with ordinary brightness (luminous intensity100 MCD); Luminous intensity between 10 and 100 MCD is called high brightness led. Generally, the working current of LED is in the range of ten milliamps to tens of milliamps, while the working current of low-current LED is below 2mA (the brightness is the same as that of ordinary LED). In addition to the above classification methods, there are also methods of classification by chip material and classification by function.
The application of LED in street lamp editing has inherent advantages and disadvantages.
1. Advantages: 1. As a point light source, if the design is reasonable, LED can directly solve the problems of secondary light emission and light loss that traditional spherical light sources must rely on light; Secondly, the uniformity of the light irradiation surface can be controlled, and theoretically it can be completely uniform in the target area, which can also avoid the light waste of the phenomenon of "light under the lamp" in traditional light sources; Thirdly, color temperature can be selected, which is also an important way to improve efficiency and reduce cost in different applications; Fourth, there is still a lot of room for technological progress. Second, the disadvantages (factors affecting the popularization and application of street lamps) are: the current price is still too high and the luminous flux is low. At present, the price of LED light source with the same illumination design is about four times that of traditional light source (but in street lamp products, the light source part accounts for a small proportion in the total cost, so the cost increase ratio in engineering installation will not be too high, and the application space is still relatively large), which is unbearable for civil use. At present, the design and manufacturing standards are chaotic and the damage rate is high, which affects the life advantage of LED.
Edit the related products of LED application in this section.
1.LED landscape: LED hard strip, LED soft strip, LED digital tube, LED meteor shower, LED projection lamp, LED wall washing lamp, LED point light source, LED ceiling lamp, LED underground lamp and LED underwater lamp; 2.LED indoor: LED fluorescent lamp, LED spotlight, LED bulb lamp, LED street lamp, LED ceiling lamp and LED counter lamp; 3.LED flow; LED bulb
4.LED car lighting; 5.LED advertisement/description; 6.LED display screen, LED and others.
Three reasons why the LED products in this paragraph are "expensive"
1. Domestic enterprises have no core technology.
Most of the core patents in the upstream of LED industry are mastered by foreign manufacturers. At present, we have no core technology. Although the manufacturing capacity of our LED application products accounts for 50% and 50% of the world, the profit is the lowest. With the increase of technology and quantity, the manufacturing process of larger size wafers of LED chips will continue to reduce costs. In recent years, the speed has been decreasing by 20% every year. Among the price factors of LED chips, the improvement of light efficiency should also be included in the price reduction, and better products have been bought at the same price. The cost of LED lighting mainly lies in LED chips. As long as the chip price drops, the lumen unit price of LED at this stage can be reduced to be equivalent to that of energy-saving lamps, and indoor lighting will naturally blossom everywhere. There is still a lot of room for price reduction for LED chips.
2.LED application products are difficult to dissipate heat.
Structural design accounts for about 20% of lamps. The industrious people in China have always kept the price low, and 20% of the cost is reasonable. The biggest problem is how to make more innovative's design more reasonable. The cooling cost should be maintained at 5%. The actual heat dissipation design is very simple, and there are two directions: First, the shorter the path between the LED chip and the external heat dissipation device, the better your heat dissipation design; Second, heat dissipation resistance means that there must be enough heat dissipation paths and enough' heat dissipation paths'. This part of the cost is mainly in the structure, and the cost for heat dissipation is not much.
3.LED application power management
Power supply is the weakest link of LED lamps, which lags behind the development of LED lamps seriously, and its quality needs to be improved. At present, the design accounts for about 20% of the cost of lamps, which is somewhat high. With the development of technology, the most reasonable power supply is probably 5- 10%. The cost of LED is very high. In fact, compared with other current light sources, the LED industry, which invented blue LED in 1990s, LED to the realization of white LED, and the current cost is actually not high. In particular, LED is environmentally friendly, energy-saving and mercury-free, and the price of LED lamps is declining every quarter. I believe that it can reach an acceptable level in a short time.
Edit the nine performance characteristics of LED driving power supply in this paragraph.
According to the power consumption law of power grid and the characteristics of LED driving power supply, the following nine performance characteristics should be considered when selecting and designing LED driving power supply: 1. The reliability is high, especially the driving power supply of LED street lamps is installed at high altitude, which is inconvenient to maintain and high in cost. 2. High-efficiency LED is an energy-saving product, and the efficiency of driving power supply should be high. This is especially important for the structure in which the power supply is installed in the lamp. Because the luminous efficiency of LED will decrease with the increase of LED temperature, the heat dissipation of LED is very important. The power supply has high efficiency, low power consumption, low heat generation in the lamp, and also reduces the temperature rise of the lamp. It is beneficial to delay the light decay of LED. 3. High power factor Power factor is the requirement of power grid for load. There is generally no mandatory index for electrical appliances below 70 watts. Although the low power factor of a single electrical appliance has little influence on the power grid, if everyone lights up at night and the similar load is too concentrated, it will cause serious pollution to the power grid. For 30-40W LED driving power supply, it is said that in the near future, the power factor may have certain index requirements. 4. There are two driving modes: one is that a constant voltage source is used for multiple constant current sources, and each constant current source supplies power to each LED respectively. This combination is flexible, and the failure of one LED will not affect the work of other LEDs, but the cost will be slightly higher. The other is direct constant current power supply, and LED runs in series or parallel. Its advantage is low cost, but poor flexibility. It is also necessary to solve the problem that one LED failure does not affect the work of other LEDs. These two forms coexisted for some time. Multi-channel constant current output power supply mode, the cost performance will be better. Maybe it is the mainstream direction in the future. 5. The ability of surge protection LED to resist surge is relatively poor, especially the ability to resist reverse voltage. It is also important to strengthen protection in this respect. Some led lights are installed outdoors, such as LED street lamps. Due to the on-off of power grid load and the induction of lightning strike, various surges will invade from the power grid system, and some surges will lead to the damage of LED. Therefore, LED driving power supply should have the ability to restrain surge intrusion and protect LED from damage. 6. Protection function In addition to the conventional protection function, it is best to add LED temperature negative feedback to the constant current output to prevent the LED temperature from being too high. 7. In terms of protection, the lamps are externally mounted, the power supply structure should be waterproof and moisture-proof, and the shell should be sun-resistant. 8. The life of the driving power supply should be compatible with the life of the LED. 9. Meet the requirements of safety regulations and electromagnetic compatibility. With the increasing application of LED, the performance of LED driving power supply will be more and more suitable for the requirements of LED.
Edit this paragraph LED packaging technology introduction.
1. The crystal expands, which makes the densely arranged wafers slightly separate from the solid crystal. 2. Fixing the mold: coat conductive/non-conductive adhesive on the bottom of the bracket (whether conductive or not depends on whether the wafer is upper and lower PN junction or left and right PN junction) and then put the wafer into the bracket. 3. Bake for a short time, so that the wafer does not move when the glue cures the bonding wire. 4. Bonding, that is, connecting the wafer and the bracket with gold wire. 5. Pre-test, the first test can be bright. 6. Pouring glue, and wrapping the chip and the bracket with glue. 7. Bake for a long time and let the glue cure. 8. Post-test, test whether it can be lit and whether the electrical parameters are up to standard. 9。 Spectrum and color separation, separating products with roughly the same color and voltage. 10, packaging.
Edit the application of this LED in various fields.
(1) display screen, traffic signal, advertising multimedia and urban lighting display light source LED lamps have the characteristics of earthquake resistance and impact resistance, fast light response, power saving and long service life, and are widely used in various indoor and outdoor display screens, which are divided into full color, tri-color and monochrome displays. There are more than 100 sets in China under development and production. Traffic lights mainly use ultra-high brightness red, green and yellow LEDs. Because of the energy-saving and high reliability of LED lights, traffic lights are being upgraded step by step all over the country, which is a good market opportunity with fast promotion speed and great market demand. (2) Application in automobile industry Automobile lamps include dashboard, audio indicator, switch backlight, reading lamp, external brake lamp, taillight, side lamp, headlight, etc. Incandescent lamps for automobiles are not resistant to impact and impact, easy to be damaged, short in life and need to be replaced frequently. 1987, China began to install high-position brake lights on cars. Due to the fast response speed of LED, drivers can be reminded to brake as soon as possible to reduce rear-end collision accidents. In developed countries, the central rear high-position brake light made of LED has become the standard of automobiles. The LED taillight module introduced by Hewlett-Packard Company in the United States in 1996 can be combined into various taillights at will. In addition, the light source in lighting components such as automobile dashboard can be used as ultra-high brightness light, so LED display screen is gradually adopted. China automobile industry is in a period of great development, which is an excellent opportunity to promote ultra-high brightness LED. In recent years, the annual output value 1 100 million yuan will be 3 billion yuan after five years. (3) The LED backlight with high efficiency side emission is the most eye-catching. As the backlight of LCD, LED has the characteristics of long life, high luminous efficiency, no interference and high cost performance, and has been widely used in electronic watches, mobile phones, BP machines, electronic calculators, credit card machines and so on. With the miniaturization of portable electronic products, LED backlight has more advantages, so the backlight manufacturing technology will develop towards thinner, lower power consumption and uniformity. LED is the key device of mobile phone. An ordinary mobile phone or PHS needs about 10 LED devices, while a color screen and a mobile phone with camera function need about 20 LED devices. At present, the backlight of mobile phones is very large, and 3.5 billion LED chips are used every year. At present, the output of mobile phones in China is very large, and most of the LED backlights are imported, which is an excellent market opportunity for domestic LED products. (4) (4) The early products of LED lighting source have low luminous efficiency, and the light intensity can only reach several tens of MCD, which is suitable for indoor occasions, household appliances, instruments and meters, communication equipment, microcomputers, toys, etc. At present, the direct goal is to replace incandescent lamps and fluorescent lamps with LED light sources, and this substitution trend has begun to develop from local application fields. In order to save energy, Japan is planning a light-emitting diode project (called "Lighting Japan") to replace incandescent lamps. The budget for the first five years is 5 billion yen. If LED is used to replace half of incandescent lamps and fluorescent lamps, the energy equivalent to 6 billion liters of crude oil can be saved every year, which is equivalent to the power generation of five 1.35 × 106kW nuclear power plants, and the generation of greenhouse gases such as carbon dioxide can be reduced, thus improving people's living environment. China also invested 5 billion yuan in 2004 to develop energy-saving and environmental-friendly semiconductor lighting plan [4]. (5) For other applications, such as a kind of flashing shoes popular with children, the built-in LED will flash when walking, and 500 million LEDs are used in Wenzhou alone; Using light-emitting diodes as the power index of electric toothbrushes, according to domestic manufacturers who are putting into production, the company has listed a small number of healthy toothbrushes, and it is estimated that 300 million light-emitting lamps will be needed every year for mass production; The popular LED Christmas lights are novel in shape, colorful, unbreakable and safe to use at low voltage. Recently, they have sold strongly in Southeast Asia, such as Hong Kong, and are widely welcomed by people, threatening and replacing the existing light bulb Christmas market.
Edit some problems faced by this paragraph of LED industry.
Guided by the strategic task of promoting the optimization and upgrading of industrial structure and cultivating new industrial growth points, LED has become the development focus of local governments. Dongguan, Huizhou, Foshan, Shenzhen, Dalian, Nanchang, Xiamen and other local governments have made strategic plans for industrial development, which set off an LED investment boom in China. Guangdong, which accounts for nearly half of the total domestic LED output value, listed the semiconductor lighting (LED) industry as one of the three strategic emerging industries in Guangdong in May. Guangdong's LED industry has formed a situation in which a hundred schools of thought contend. Shenzhen, Dongguan and Foshan have listed the LED industry as a pillar industry. The LED industry is in full bloom. Domestic LED enterprises have risen rapidly and expanded their production capacity rapidly in order to compete for the LED market. From Sanan Optoelectronic, a leading enterprise in the domestic LED industry, to Sloan to expand production capacity, and then to Dehao Runda, who became a monk halfway, the LED industry boom has almost swept the whole industry. Because the overall level of domestic LED product technology is not high, domestic enterprises are generally small in scale, weak in technical strength and low in product grade. The competition in the LED market is fierce, and related manufacturers are competing for price wars. At the same time, disorderly investment and vicious competition have also appeared in the LED industry. Judging from the current domestic market dynamics and LED industrial structure distribution, there has been a serious problem of repeated investment. In addition, some local governments intend to open the local market to local enterprises or lock in the local market through investment market when developing their economies, and local protectionism has risen. If this local administrative barrier is not broken, it will inevitably lead to the convergence of industrial projects between regions, directly increase the industrial bubble and hinder the development process of regional integration. Different regions should highlight different characteristics and avoid simply repeating construction for short-term benefits, which will lead to vicious competition in the future. In addition, there are a series of other problems in LED lighting in China. For example, there is no national standard for LED lights in China, only some local standards; The innovative design ability of local LED lamps in China is obviously insufficient. Only by solving these problems can the LED industry develop more healthily and LED products meet the needs of the public. Market dominance is the basis for the long-term healthy development of LED lighting industry. The government should guide and support the LED lighting industry from policies and regulations, R&D investment, application demonstration and standards. Only with a game of chess and overall planning can the LED lighting industry develop continuously and healthily.
Edit this paragraph LED and LED visible light communication technology.
As high-power LED is about to become the main force of the next generation of solid-state lighting (SSL), there are more bold new ideas in the electronics industry. That is to say, we abandon the crowded RF bandwidth and adopt led switch mode to transmit data, which is called LED visible light communication (VLC). With the support of advanced technology, each new LED lamp can be connected to the backbone network by wire, thus realizing ubiquitous wireless communication between different devices without increasing the burden of existing RF bandwidth. This kind of LED visible light communication transmission technology mostly adopts white LED, because white LED is characterized by fast response speed and can be used as the basis of visible light communication technology. LED visible light transmission technology uses indoor lighting equipment, such as fluorescent lamps or white LEDs, to send out high-speed bright and dark flashing signals that can't be detected by naked eyes and transmit data wirelessly. Visible light is used because of its wide wavelength range, and visible light signals can be transmitted through different wavelengths by design. R&D staff will also test different light wavelengths and use different colors that make up white light to develop coded content for multiple data streams. The advantage of LED visible light communication technology lies in that it can avoid the interference of electromagnetic waves emitted by general WLAN or high-frequency wireless transmission to human body and peripheral electronic devices, can replace wireless base stations, and has the characteristics of high security. At present, many industries, standards organizations, or government-funded projects have begun to develop LED visible light communication, and the prospects are very promising. After all, the scale of the traditional lighting market alone has reached several trillion dollars, and there will be considerable business opportunities for the transition to the solid-state lighting market in the future.
Edit the important parameters of this LED to solve the puzzle.
1. Forward working current If: refers to the forward current value of the LED when it normally emits light. In fact, IF necessary, if should be lower than 0.6 IFm. 2. Forward working voltage VF: The working voltage given in the parameter table is obtained under a given forward current. Generally measured at IF=20mA. The forward working voltage VF of LED is1.4 ~ 3v.. When the external temperature increases, VF will decrease. 3.V-I characteristics: the relationship between voltage and current of LED. When the DC voltage is just below a certain value (called threshold), the current is very small and no light is emitted. When the voltage exceeds a certain value, the forward current increases rapidly with the voltage and emits light. 4. Luminous intensity IV: The luminous intensity of LED usually refers to the luminous intensity in the normal direction (for cylindrical LED, its axis). If the radiation intensity in this direction is (1/683)W/sr, 1 Candeira (symbol cd) is emitted. Because the luminous intensity of general LED is relatively small, Candeira (mcd) is usually used to measure the luminous intensity. 5.LED luminous angle:-90-+90 6. Spectral half-width Δ λ: indicates the spectral purity of LED. 7. Half-value angle θ 1/2 and viewing angle θ 1/2 refer to the angle between the direction where the luminous intensity value is half of the axial intensity value and the optical axis (normal direction). 8. Full shape: the angle converted from the solid angle of LED lamp, also called plane angle. 9. Viewing angle: refers to the maximum angle of LED light. Different viewing angles have different applications, also called light intensity angle. 10. Hemisphere: the included angle between normal 0 and maximum luminous intensity value /2. Strictly speaking, it is the angle between the maximum luminous intensity value and the maximum luminous intensity value /2. The packaging technology of LED leads to that the maximum luminous angle is not the light intensity value of normal 0, and a deviation angle is introduced, which refers to the included angle between the angle corresponding to the maximum luminous intensity and normal 0. 1 1. Maximum forward DC current IFm: maximum allowable forward DC current. Exceeding this value will damage the diode. 12. Maximum reverse voltage VRm: maximum allowable reverse voltage. If this value is exceeded, the LED may be damaged due to breakdown. 13. Working environment TOPM: the ambient temperature range where LED can work normally. Below or above this temperature range, LED will not work normally, and the efficiency will be greatly reduced. [1][2] 14. allowable power consumption pm: the maximum value of the product of the allowable forward DC voltage across the LED and the current flowing through it. If this value is exceeded, the LED will heat up and be damaged.
This section edits the technical requirements and operational precautions for LED welding.
1. Wear antistatic gloves, wrist and soldering iron during production. It is forbidden to touch the two pins of the white LED by hand. Because the antistatic property of white LED is 100V, when the humidity on the workbench is 60%-90%, the static electricity of human body will destroy the crystal layer of LED, and after working for a period of time (such as 10 hour), the LED will fail (not bright), and in severe cases, it will immediately fail. 2. The welding temperature is 260℃ for 3 seconds. If the temperature is too high and the time is too long, the chip will burn out. In order to better protect the LED, the distance between the LED colloid and the PC board should be greater than 2mm, so as to dissipate the welding heat in the pins. 3. The normal working current of 3.LED is 20mA, and a small fluctuation of voltage (such as 0. 1V) will cause a large fluctuation of current (10%- 15%). Therefore, in the circuit design, different current limiting resistors should be matched according to the voltage drop of the LED to ensure that the LED is in the best working state. If the current is too large, the life of LED will be shortened, and if the current is too small, the required light intensity cannot be achieved. Generally, when the led is supplied in batches, it will be split into colors, that is, the light intensity, voltage and color of the led in the same package are correct, and it will be indicated on the split color table.
Technology of filling silica gel into LED lens
3. 1 The surface of the substrate should be clean and dry. The moisture on the surface of the substrate can be removed by heating; Naphtha, methyl ethyl ketoxime (MEK) or other suitable solvents can be used to clean the surface of the substrate. Solvents that dissolve or corrode the substrate and residual solvents should not be used. 3.2 According to the recommended mixing ratio of -A: B = 1: 1 (weight ratio), accurately weigh it, put it in a clean glass container, and mix it thoroughly and evenly. When mixing with high-speed mixing equipment, the heat generated by high-speed mixing may increase the temperature of glue, thus shortening the use time. 3.3 Remove bubbles under the vacuum of 10mmHg. Generally, air bubbles are removed before the packaging material is dispensed. If necessary, a degassing process can be added after distribution. 3.4 In order to ensure the operability of the compound, please use it up within 60 minutes after mixing A and B. 3.5 The best curing condition is curing at 25℃ for 3-4 hours and curing completely after 24 hours; It can also be cured by heating at 50℃ for 60 minutes. When the curing temperature is lower than 25℃, properly prolonging the curing time or increasing the curing temperature is helpful for the complete curing of the product.