LED (Light Emitting Diode) is a solid-state semiconductor device that can directly convert electricity into light. The heart of the LED is a semiconductor chip. One end of the chip is attached to a bracket, one end is the negative electrode, and the other end is connected to the positive electrode of the power supply, so that the entire chip is encapsulated in epoxy resin. The semiconductor wafer is composed of two parts. One part is a P-type semiconductor, in which holes dominate, and the other end is an N-type semiconductor, where electrons are mainly present. But when these two semiconductors are connected, a "P-N junction" is formed between them. When an electric current acts on this chip through a wire, electrons will be pushed to the P region, where they will recombine with holes, and then energy will be emitted in the form of photons. This is the principle of LED luminescence. The wavelength of light determines the color of light, which is determined by the material forming the P-N junction.
Edit this paragraph LED applications
In view of the advantages of LED, it is currently mainly used in the following areas: (1) Application of display screens and traffic signal display light sources. LED lamps are earthquake-resistant. It has the characteristics of impact resistance, fast light response, power saving and long life. It is widely used in various indoor and outdoor displays, divided into full-color, three-color and monochrome displays. There are more than 100 units nationwide. Development and production. Traffic lights mainly use ultra-high-brightness red, green, and yellow LEDs. Because LED signal lights are energy-saving and highly reliable, traffic lights are being gradually updated nationwide, and they are promoted quickly and have a huge market demand. It's a good market opportunity. (2) Applications in the automotive industry Automotive lights include interior instrument panels, audio indicators, switch backlights, reading lights, and exterior brake lights, tail lights, side lights, and headlights, etc. Incandescent lamps used in automobiles are not resistant to vibration and impact, are easily damaged, and have a short lifespan, so they need to be replaced frequently. In 1987, my country began to install high-mounted brake lights on cars. Due to the fast response speed of LED, it can remind the driver to brake early and reduce rear-end collision accidents. In developed countries, the central rear high-mounted brake light made of LED has become a standard part of automobiles. In 1996, HP Company of the United States introduced Semiconductor Lighting
The launched LED car taillight modules can be combined into various car taillights at will. In addition, ultra-high-brightness luminescent lamps can be used as the light source in automobile dashboards and other various lighting parts, so LED displays are gradually being adopted. my country's automobile industry is in a period of great development, which is an excellent opportunity to promote ultra-high brightness LEDs. In the next few years, the annual output value will be 1 billion yuan, and within 5 years, the annual output value will be 3 billion yuan. (3) The most eye-catching LED backlight is the high-efficiency side-emitting backlight. As an LCD backlight, LED has the characteristics of long life, high luminous efficiency, no interference and high cost performance. It has been widely used in electronic watches, mobile phones, BP As portable electronic products become increasingly miniaturized in computers, electronic calculators and credit card machines, LED backlights have more advantages. Therefore, backlight production technology will develop towards thinner, lower power consumption and uniformity. LED is a key component of mobile phones. An ordinary mobile phone or PHS uses about 10 LED devices, while a mobile phone with color screen and camera function requires about 20 LED devices. At present, mobile phone backlight sources are very large, using 3.5 billion LED chips a year. At present, my country has a large production volume of mobile phones, and most of the LED backlight sources are imported. This is an excellent market opportunity for domestic LED products. (4) Early products of LED lighting sources have low luminous efficiency, and the light intensity can generally only reach a few to dozens of mcd. They are suitable for indoor occasions and are used in home appliances, instruments, communication equipment, microcomputers and toys. The current direct goal is to replace incandescent and fluorescent lamps with LED light sources. This substitution trend has begun to develop in local applications.
In order to save energy, Japan is planning a light-emitting diode project to replace incandescent lamps (called "Lighting Up Japan"). The budget for the first five years is 5 billion yen. If LEDs replace half of incandescent lamps and fluorescent lamps, annual savings of equivalent to The energy of 6 billion liters of crude oil is equivalent to the power generation of five 1.35 × 106kW nuclear power plants. It can also reduce the generation of carbon dioxide and other greenhouse gases and improve people's living environment. my country also invested 5 billion in 2004 to vigorously develop energy-saving and environmentally friendly semiconductor lighting plans [4]. (5) Other applications include a kind of flashing shoes that are popular with children. The built-in LED will flash and light up when walking. Wenzhou area alone uses 500 million light-emitting diodes a year; using light-emitting diodes as battery indicator lights for electric toothbrushes, according to domestic According to the manufacturer that is in production, the company has already launched a small number of health care toothbrushes, and it is estimated that 300 million luminous lights will be needed per year during mass production; the LED Christmas lights that are currently popular are novel in shape, rich in color, not easy to break, and safe when used at low voltage. Sex, recent sales have been strong in Hong Kong and other Southeast Asian regions, and they are generally welcomed by people. They are threatening and replacing the Christmas market of existing electric bulbs. (6) LED products for household indoor lighting are becoming more and more popular. LED downlights, LED ceiling lights, LED fluorescent lights, and LED fiber optic lights have quietly entered the home!
6. Sturdy and durable
LEDs are completely encapsulated in epoxy resin and are stronger than light bulbs and fluorescent tubes. There are no loose parts inside the lamp body, making the LED less likely to be damaged. LED light
7. Multiple changes
LED light source can use the three primary color principles of red, green and blue to make the three colors have 256 levels of gray and mix them arbitrarily under the control of computer technology. , can produce 256×256×256=16777216 colors, forming a variety of combinations of different light colors, achieving rich and colorful dynamic changing effects and various images.
8. Advanced technology
Compared with the monotonous luminous effect of traditional light sources, LED light sources are low-voltage microelectronic products. It successfully integrates computer technology, network communication technology, image processing technology, embedded control technology, etc., so it is also a digital information product and a "high-tech" technology for semiconductor optoelectronic devices, with online programming, unlimited upgrades, and flexibility. Features.
Edit lighting terms in this paragraph
Wavelength: The intensity of the color of light can be described by data. This data is called wavelength. The wavelength of visible light ranges from 380 to 780nm. Unit: nanometer (nm) Brightness: Brightness refers to the degree of lightness and darkness of an object, and is defined as the luminous intensity per unit area. Unit: nit (nit) Light intensity: refers to the brightness of the light source. That is, a physical quantity that represents the intensity of visible light radiation emitted by a light source in a certain direction and range. Unit: Candlelight (cd) Luminous flux: The sum of the energy emitted by the light source and received by the human eye is the luminous flux (Φ). Unit: Lumens (Lm) Light efficiency: The luminous flux emitted by the light source divided by the power of the light source. It is an important indicator to measure the energy saving of light sources. Unit: Lumens per Watt (Lm/w). Color rendering: The degree to which an object is presented by a light source, that is, how realistic the color is. Usually called "color rendering index". Unit: Ra. Color temperature: When the color of light emitted by a light source is the same as the color of light radiated by a black body at a certain temperature, the temperature of the black body is called the color temperature of the light source. Unit: Kelvin (k). Glare: The visual discomfort caused by extremely bright objects or strong brightness contrast within the field of view is called glare. Glare is an important factor affecting lighting quality. Synchronicity: Two or more LED lights can operate normally in a synchronized manner set by the program within an unspecified period of time. Synchronicity is the basic requirement for LED lights to achieve coordinated changes.
Protection level: IP protection level is a classification of lamps according to their dust-proof and moisture-proof characteristics. It consists of two numbers. The first number represents the dust-proof and foreign object intrusion level of the lamp (divided into 0-6 levels). ), the second number represents the degree of sealing of the lamp against moisture and water intrusion (divided into levels 0-8). The larger the number, the higher the protection level.
Edit this paragraph LED development
The development of LED display screens can be divided into the following stages: The first stage is from 1990 to 1995, mainly single color and 16-level two-color Picture and text screen. Used to display text and simple pictures, mainly used in public places such as stations, financial securities, banks, post offices, etc., as a public information display tool. The second stage was from 1995 to 1999, when dual-primary color video screens with 64 levels and 256 levels of gray appeared. The application of video control technology, image processing technology, optical fiber communication technology, etc. has elevated LED display screens to a new level. Special large-scale integrated circuit chips for LED display control were also developed and applied by domestic companies at this time. The third stage began in 1999. Red, pure green, and pure blue LED tubes poured into China in large numbers. At the same time, domestic companies conducted in-depth research and development work. Full-color displays produced using red, green, and blue primary color LEDs were widely used. A large number of large screens have entered public places such as stadiums, convention and exhibition centers, and squares, thus bringing domestic large screens into the full-color era. With the rapid development of the LED raw material market, surface mount devices have been available since 2001. They are mainly used in indoor full-color screens. With their high brightness, bright colors, low temperature, and freely adjustable point spacing, they are used in different price ranges. Accepted by readers, in just over two years, product sales have exceeded 300 million yuan, and the surface mount full-color LED display application market has entered the new century. In order to adapt to the "slimming" plan of the 2008 Olympic Games, Leyard developed surface-mounted dual-color displays, which are widely used in training halls and competition timing and scoring systems. In terms of full-color screens in Olympic venues, in order to reduce investment, most of the full-color screens are detachable. They can be used as live broadcast tools during the Olympics and can be rented after the event and used as application tools in public occasions such as performances and national policy releases. This way costs can be recouped as quickly as possible. As far as the market is concerned, China's accession to the WTO and Beijing's successful bid for the Olympic Games have become new opportunities for the development of the LED display industry. The domestic LED display market continues to grow. Currently, the market share of domestic LED displays in the domestic market is nearly 95%. The international market capacity of LED display screens is expected to grow at a rate of 30% per year. The main manufacturers of LED displays are concentrated in Japan, North America and other places, and the export share of my country's LED manufacturers is negligible. According to incomplete statistics, there are currently at least 150 manufacturers producing full-color screens in the world, with a complete range of products, and about 30 larger companies. At present, through the Chinese government’s active promotion of LED industrialization, domestic LED display production technology is basically in sync with the world. Well-known domestic brands include: Yuanliang International Lighting, TopVision, Yuanheng Optoelectronics (Yaham), Shanmu Display (skymax-display), Lightking, Unilumin, Retop, aled, liantronics, cfled, Mingerjie (MejLed), Decai Optoelectronics (dicolor), Liansen (lenson), Lianghui Optoelectronics (lhgd), Tongpu (TOP), Yaqiguang (Art), Jinlixiang, Absen (absen), Esway (aswei), ledsun, Leyard, SBC, Sansi, etc.
Edit the light-emitting principle of LED in this paragraph
LED flashlight
Light-emitting diodes are composed of III-IV compounds, such as GaAs (gallium arsenide), GaP ( It is made of semiconductors such as gallium phosphide (gallium phosphide) and GaAsP (gallium arsenic phosphate). Its core is a PN junction.
Therefore, it has the I-N characteristics of a general P-N junction, that is, forward conduction, reverse cut-off, and breakdown characteristics. In addition, under certain conditions, it also has luminescent properties. Under forward voltage, electrons are injected from the N region into the P region, and holes are injected from the P region into the N region. Part of the minority carriers (minor carriers) that enter the opponent's area recombine with the majority carriers (majority carriers) and emit light, as shown in Figure 1. Assuming that luminescence occurs in the P region, the injected electrons directly recombine with the valence band holes and emit light, or they are first captured by the luminescent center and then recombine with the holes to emit light. In addition to this luminescent recombination, some electrons are captured by the non-luminescent center (this center is between the conduction band and the medium band), and then recombine with holes. The energy released each time is not large, and visible light cannot be formed. The greater the ratio of the luminescent recombination amount to the non-luminescent recombination amount, the higher the photon quantum efficiency. Since recombination emits light in the minority carrier diffusion region, light is only generated within a few μm of the PN junction. Theory and practice have proven that the peak wavelength λ of light is related to the bandgap width Eg of the semiconductor material in the light-emitting region, that is, λ≈1240/Eg (mm) where the unit of Eg is electron volt (eV). If visible light (wavelength between 380nm purple light and 780nm red light) can be produced, the Eg of the semiconductor material should be between 3.26 and 1.63eV. Light with a longer wavelength than red light is infrared light. There are now infrared, red, yellow, green and blue light-emitting diodes, but the cost and price of blue light-emitting diodes are very high and are not commonly used.
Edit this section LED dimming control
Traditionally, LED dimming is accomplished by using a DC signal or filtrate PWM to adjust the forward current in the LED. Reducing the LED current will have the effect of adjusting the intensity of the LED light output. However, changes in forward current will also change the color of the LED because the chromaticity of the LED will change as the current changes. Many applications, such as automotive and LCD TV backlighting, cannot tolerate any color drift in LEDs. In these applications, wide-range dimming is necessary because there are different light changes in the surrounding environment and the human eye is sensitive to small changes in light intensity. Controlling LED brightness by applying a PWM signal allows LED dimming to be accomplished without changing the color. What people often call True Color PWM dimming is to use a PWM signal to adjust the brightness of the LED. There are three common methods to adjust LED brightness: (1) Use a SET resistor, connect different conversion resistors in parallel to both ends of the LED driver control IC pin RSET, and use a DC voltage to set the current of the LED driver control IC pin RSET, thereby changing the LED's Forward working current achieves the purpose of adjusting the brightness of ALED. (2) Using PWM technology, the PWM control signal is used to adjust the luminous brightness of the ALED by controlling the duty cycle of the forward working current of the LED. (3) Linear adjustment The simplest method is to use an external SET resistor in the LED driver control C to achieve LED dimming control. Although this method of dimming control is effective, it lacks the flexibility to allow users to change the light intensity. Linear adjustment reduces efficiency and causes a color shift of white LEDs toward the yellow spectrum. May be a slight offset, but detectable in sensitive applications. Use a digital or PWM LED dimming control method with a switching operating frequency greater than 100HZ, and use pulse width modulation to change the pulse duty cycle of the LED drive current to implement LED dimming control. Choose a switch dimming control greater than 100HZ. The frequency is mainly to avoid the human eye feeling the dimming flicker phenomenon. Under the PWM dimming control of the LED, the luminous brightness of the LED is proportional to the pulse duty cycle of the PWM. Under this dimming control method, the light can be dimmed at a high The luminous color of the LED remains unchanged within the ratio range. The dimming ratio range of LED dimming control using PWM can reach 3000:1.
The linear LED dimming control method uses analog dimming control. Under analog dimming control, LED dimming control is achieved by adjusting the forward working current of the LED. The dimming control range can reach 10:1. If the forward working current of the LED is to be further reduced, problems such as the LED light color changing and the inability to accurately adjust and control the forward working current of the LED will occur.
Edit the operating parameters and efficiency of this section
Generally, the most common LED operating power is set below 30 to 60 milliwatts of electricity. In 1999, commercial-grade LEDs that could be used continuously with a power input of 1 watt were introduced. These LEDs use extra large semiconductor chips to handle the problem of high power input, and the semiconductor chips are fixed on metal iron sheets to help dissipate heat. In 2002, 5-watt LEDs began to appear on the market, and their efficiency was approximately 18 to 22 lumens per watt. In September 2003, Cree, Inc. demonstrated its new blue LED, achieving a lighting efficiency of 35 at 20 mA. They also produced a white LED product with 65 lumens per watt, which was the brightest white LED on the market at the time. In 2005 they demonstrated a white LED prototype that achieved a record efficiency of 70 lumens per watt at 350 mA. Today, the working efficiency of OLED is much lower than that of ordinary LEDs, with the highest efficiency only being around 10. But the production cost of OLED is much lower. For example, a simple printing method can be used to place an extra large OLED array on the screen to create a color display.
Edit this paragraph LED pull-up resistor
Generally, when the LED is working, adding 10mA is enough to make it work normally, so the resistance value is Vo/10mA, and Vo is the value of the external resistor. For example, a 500-ohm resistor can be used at a voltage of 5V
LED display control system
Briefly speaking, it is divided into: synchronous control system (synchronized with computer output content); asynchronous offline control System (store content in the control card and run offline) With the rapid development of LED displays in the past two years, the market for LED control systems has also become broader, especially the newly launched Vinda U disk LED in 2009 Control cards are currently the most used. Vinda USB flash drive LED control card can be connected to a computer via a serial port, or a USB flash drive can be used to transmit information. It saves computers, requires no wiring, and supports analog clocks and water frames. Vinda USB flash drive LED control cards are suitable for various indoor applications. The external display screen has been loved by LED display manufacturers all over the country since its launch. LED control card
The development of LED display screens has gradually entered civilian use, such as door screens for various stores, various square screens indoors and outdoors, and various other strip screens. Currently, a display screen must be connected to a computer to update content, which makes it difficult for a large number of users, especially advertising users, to update programs. The USB flash drive LED control card solves this problem. Using the USB flash drive, the most common and cheap information transmission media tool, even if the user does not have a computer, he can use the Internet cafe, home or friend's computer to edit the content to update the display screen content. The disk does not need to be plugged into the display screen or its extension cable all the time. After plugging in, the information will be stored in the screen within a few seconds, and the USB disk can be removed. The USB flash drive LED control card has common serial port communication functions. Users who want to communicate directly with a computer can directly connect and use it. U disk is used to transfer LED display content, and has been gradually used in LED displays across the country. LED display control card, also known as LED asynchronous controller, is the core component of LED graphic and text display. Responsible for receiving the screen display information from the computer serial port, placing it into the frame memory, and generating the serial display data and scan control timing required for the LED display according to the partition driving method. LED displays mainly display various texts, symbols and graphics. The screen display information is edited by the computer, and is pre-installed into the frame memory of the LED display through the RS232/485 serial port, and then displayed and played screen by screen, repeating the cycle. The display modes are rich and colorful, and the display screen works offline.
LED display screens are widely used in various industries in society because of their flexible control, easy operation and low cost.
Edit this paragraph LED classification
1. According to the light-emitting color of the light-emitting tube, it can be divided into red, orange and green (also subdivided into yellow-green and standard green). and pure green), blue light, etc. In addition, some light-emitting diodes contain chips of two or three colors. According to whether the light emitting diode is doped with a scattering agent or not, and whether it is colored or colorless, the above-mentioned light-emitting diodes of various colors can also be divided into four types: colored and transparent, colorless and transparent, colored scattering and colorless scattering. Scattered light-emitting diodes are used as indicator lights. 2. According to the characteristics of the light-emitting surface of the luminous tube, it can be divided into round lamps, square lamps, rectangular lamps, surface luminous tubes, lateral tubes, micro-tubes for surface mounting, etc. Round lights are divided into φ2mm, φ4.4mm, φ5mm, φ8mm, φ10mm and φ20mm according to diameter. Abroad, the φ3mm light-emitting diode is usually recorded as T-1; the φ5mm one is marked as T-1 (3/4); the φ4.4mm one is marked as T-1 (1/4). The circular luminous intensity angular distribution can be estimated from the half-value angle. There are three categories according to the luminous intensity angular distribution diagram: (1) High directivity. Generally, it is a pointed epoxy package or a metal reflective cavity package without adding scattering agent. The half-value angle is 5° to 20° or less. It has high directivity and can be used as a local lighting source or used in conjunction with a light detector 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 light with a large viewing angle, a half-value angle of 45° to 90° or more, and a large amount of scattering agent. 3. According to the structure of the light-emitting diode, the structure of the light-emitting diode is divided into full epoxy encapsulation, metal base epoxy encapsulation, ceramic base epoxy encapsulation and glass encapsulation. 4. According to luminous intensity and working current, there are ordinary brightness LEDs (luminous intensity 100mcd) according to luminous intensity and working current; those with luminous intensity between 10 and 100mcd are called high-brightness light-emitting diodes. Generally, the operating current of LEDs is between tens of mA and tens of mA, while the operating current of low-current LEDs is below 2mA (the brightness is the same as that of ordinary light-emitting tubes). In addition to the above classification methods, there are also methods of classification by chip material and classification by function.
Edit this paragraph LED has inherent advantages and disadvantages when used in street lights
1. The advantages are: First, LED as a point light source can be directly solved to a large extent if the design is reasonable. Traditional spherical light sources must rely on light emission to solve the secondary light extraction and light loss problems; secondly, the uniformity of the light irradiation surface is controllable, and theoretically it can be completely uniform in the target area, which can also avoid traditional light sources. The waste of light in the phenomenon of "lighting up under the lamp"; Third, the color temperature is optional, which is also an important way to improve efficiency and reduce costs in applications in different situations; Fourth, there is still a lot of room for technological progress. 2. Disadvantages (factors affecting the promotion and application of street lights) are: The current price is still too high and the luminous flux is low. The current price of LED light sources with the same illumination design is about four times that of traditional light sources (however, in street light products, the light source part accounts for the total cost It is not high, so the cost increase in engineering installation will not be too high, and the application space is still relatively large), which is unaffordable for civilian use.
The current design and manufacturing standards are relatively confusing, and the damage ratio is high, which affects the lifespan advantage of LEDs
Edit related products for LED applications in this section
1. LED landscape 2. LED indoor 3. LED transportation 4. LED automotive lighting 5. LED advertising/indication 6. LED display screen LED others
Edit this paragraph: Three major reasons why LED products are “expensive”
1. Domestic enterprises No core technology
Most of the core patents in the upstream of the LED industry are in the hands of foreigners. We do not have core technology, even though our LED application product manufacturing capabilities account for 50% of the global share. , but profit is the lowest part. As the technology and quantity of LED chips increase, the production process of larger wafers will be adopted, which will continue to reduce costs. In recent years, the cost has been reduced by 20% every year. In the LED chip price factor, the improvement of light efficiency must also be included in the price reduction. Bought a better product for the same price. The cost of LED lighting fixtures mainly lies in the LED chip. As long as the chip price drops and the unit price of LED lumens can be reduced to the same level as the current energy-saving lamps, indoor lighting will naturally bloom everywhere. There is still plenty of room for price reductions in LED chips.
2. It is difficult to dissipate heat in LED application products
Structural design accounts for about 20% of the lamps. The hard-working people in China have always set prices very low. The cost of 20% is considered very reasonable. The biggest problem is How to be more innovative and design more reasonable. The heat dissipation cost must be maintained at 5. The actual heat dissipation design is very simple. Focus on two directions: first, the shorter the path between the LED chip and the external heat dissipation device, the better. The shorter the path, the better your heat dissipation design; second, the heat dissipation resistance. That is to say, there must be enough heat dissipation paths and sufficient "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 seriously lags behind the development of LED lamps, and the quality needs to be improved. Design now accounts for about 20% of the cost of lamps, which is a bit high. With the development of technology, the most reasonable power supply is probably 5-10. The high cost of LED is actually due to the fact that compared to other current light sources, as the LED industry that only invented blue LED in the 1990s, which led to the realization of LED white light, 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 falling every quarter. I believe it will reach a level that people can accept in a short period of time.
Edit this section of the nine performance characteristics requirements of LED drive power supplies
According to the power consumption rules of the power grid and the characteristic requirements of LED drive power supplies, factors must be taken into consideration when selecting and designing LED drive power supplies. The following nine performance characteristics are required: 1. High reliability, especially the driving power supply of LED street lights, which is installed at high altitude, making maintenance inconvenient and expensive. 2. High-efficiency LEDs are energy-saving products, and the efficiency of the driving power supply must be high. This is especially important for structures where the power supply is installed inside the lamp. Because the luminous efficiency of LEDs decreases as the temperature of the LED increases, the heat dissipation of the LED is very important. The efficiency of the power supply is high, its power consumption is small, and the heat generated in the lamp is small, which 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 the grid for the load. Generally, there are no mandatory indicators for electrical appliances below 70 watts. Although the power factors of individual electrical appliances with low power will have little impact on the power grid, if everyone lights up lights at night and the same type of load is too concentrated, it will cause serious pollution to the power grid. For 30- to 40-watt LED driving power supplies, it is said that there may be certain index requirements for power factors in the near future. 4. There are currently two driving methods: one is a constant voltage source that supplies multiple constant current sources, and each constant current source supplies power to each LED independently. In this way, the combination is flexible. If one LED fails, it will not affect the work of other LEDs, but the cost will be slightly higher. The other is direct constant current power supply, with LEDs running in series or parallel.
Its advantage is that the cost is lower, but the flexibility is poor. It also needs to solve the problem of a certain LED failure without affecting the operation of other LEDs. These two forms coexisted for some time. The multi-channel constant current output power supply method will be better in terms of cost and performance. Maybe it will be the mainstream direction in the future. 5. Surge protection LED's ability to withstand surges is relatively poor, especially its ability to withstand reverse voltage. Strengthening protection in this area is also important. Some LED lights are installed outdoors, such as LED street lights. Due to the switching of the power grid load and the induction of lightning strikes, various surges will invade from the power grid system, and some surges will cause damage to the LED. Therefore, the LED driving power supply must have the ability to suppress surge intrusion and protect the LED from damage. 6． Protection function In addition to the conventional protection functions of the power supply, 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, if the lamp is externally installed, the power supply structure must be waterproof and moisture-proof, and the outer casing must be light-resistant. 8． The life of the driving power supply must match the life of the LED. 9. Must comply with safety regulations and electromagnetic compatibility requirements. As the application of LED becomes more and more widespread, the performance of LED driving power supply will become more and more suitable for the requirements of LED.
Edit this paragraph to introduce the LED packaging technology
1. Expand the crystal, and open up the densely arranged wafers a little to facilitate the solidification of the wafers. 2. To fix the crystal, put some conductive/non-conductive glue on the bottom of the bracket (whether the chip is conductive or not depends on whether the chip is an up-and-down PN junction or a left-right PN junction) and then put the chip into the bracket. 3. Bake short so that the chip does not move while the glue solidifies and the wire is bonded. 4. Wire bonding, use gold wire to connect the chip and the bracket. 5. Pre-test, preliminary test to see if it can light up. 6. Fill in glue and wrap the chip and bracket with glue. 7. Bake for a long time to allow the glue to solidify. 8. Post-test, test whether it can light up and whether the electrical parameters meet the standards. 9. Spectroscopic color separation is used to separate products with roughly the same color and voltage. 10. Packaging.