LED lighting lamps and lanterns related knowledge, which god to teach, gray thanks!

LED products and related knowledge

Composition

LED (Light Emitting Diode), light-emitting diode, is a solid-state semiconductor device, which can be directly converted from electrical energy to light energy. The heart of LED enterprise-Legendary Optoelectronics LED is a semiconductor wafer, one end of the wafer is attached to a bracket, is the negative pole, the other end is connected to the positive pole of the power supply, the whole wafer is encapsulated by epoxy resin. Semiconductor wafer consists of two parts, one part is a P-type semiconductor, in which holes dominate, the other end is a N-type semiconductor, on this side is mainly electronic. However, when these two semiconductors are connected, a "P-N junction" is formed between them. When the current through the wire on the wafer, the electrons will be pushed to the P region, in the P region of the electron and hole complex, and then will be issued in the form of photons of energy, which is the principle of LED light-emitting. The wavelength of light (the color of light) is determined by the formation of P-N junction material.

LED (Light-Emitting-Diode Chinese meaning light-emitting diode) is a semiconductor capable of converting electrical energy into light energy, it changed the incandescent tungsten light and energy-saving lamps three-color powder light-emitting principle, and the use of electric field light-emitting. According to the analysis, the characteristics of the LED is very clear

LED bulbs as well as lamps and lanterns pictures (19) obvious, long life, high luminous efficacy, no radiation and low power consumption. White LED spectrum is almost entirely concentrated in the visible light band, its luminous efficiency can exceed 150lm / W (2010). LED and ordinary incandescent lamps, spiral energy-saving lamps and T5 three-color fluorescent lamps for comparison, the results show that: ordinary incandescent lamps for 12lm / W, life less than 2,000 hours, spiral energy-saving lamps for 60lm / W, life less than 8,000 hours, T5 fluorescent lamps for 96lm / W, life of about 10,000 hours, and the diameter of the 5 mm white light LED Theoretically, the luminous efficacy can be more than 150lm / W, life expectancy can be greater than 100000 hours. Some people also predict that the future of the LED life ceiling will be infinite. However, the working principle of the LED lamp makes the heat dissipation problem in the high-power LED lighting industry has become very prominent, many LED lighting programs do not pay enough attention to heat dissipation, or the technical level is limited, so the current mass production of high-power LED lamps generally exist in the actual service life is far less than the theoretical value, cost-effective than the traditional lamps and lanterns of the embarrassing situation. In order to improve the service life of LED lamps and lanterns, really suitable for commercial mass production, LED lighting industry is independent or professional thermal conductive material suppliers to step up the development of new thermal conductive materials, such as thermal conductive plastic and so on.

High-power LED, generally refers to greater than 0.65W, which is different within the company will have different standards, because at present in the field of high-power LED has not yet formed a unanimously recognized industry standards. Light intensity and lumens than small power, but the same heat dissipation is also very large, now most of the high power is a single application, coupled with a large effective heat dissipation area of the heatsink, also appeared integrated in the LED light matrix, but the heat dissipation effect is not very good. Small power is generally about 0.06W. Now the LED flashlight is generally used with low-power use, light dispersion, depending on the LED light-emitting angle, there is a large angle of small angle, small angle is not dispersed, large angle is dispersed. The flashlight on the market is generally made of straw hat head. The effect is very good. Now it is worried that some manufacturers do not value the quality, take the substandard LED to do flashlights, not long to have a dead light.

The brightness of the LED is with the LED light-emitting angle is necessarily related to the angle of the LED, the smaller the angle of the LED the higher the brightness, there is no super-bright not super-bright, that is a lie to the children, if it is a good quality of the LED regardless of which LED manufacturers are produced by the brightness of everyone is almost the same, just the production process is not the same, the service life of a slightly different, because everyone is used in that a few foreign countries. LED chip. If the 5MM LED 180-degree angle of the brightness of the white light is only a few hundred MCD, if it is 15-degree angle of the brightness to go to more than 10,000 to 20,000 MCD of the brightness of the difference between the brightness of dozens of times, if it is used for lighting, outdoors the best is to use high-power LEDs, the brightness of the higher, a single power 1W, 3W, 5W, but also with a number of high-power combination of a High-power LED, the power to go to several hundred have.

Color temperature and brightness does not matter, and brightness and lumen value related

Look at a few related concepts:

Luminous flux

(lm)

Because of the human eye on different wavelengths of electromagnetic waves with different sensitivities, we can not directly with the radiant power of the light source or the radiant flux to measure the energy of the light, we must use the amount of the human eye's sensory perception of the light It must be measured in units of ---- luminous flux based on the amount of light perceived by the human eye. Luminous flux is represented by the symbol Φ and the unit is lumen (lm).

Luminous intensity

(cd)

Luminous flux is the total amount of light energy emitted by a light source into the surrounding space. The distribution of luminous flux in space is different for different light sources. Luminous intensity in candelas, the symbol for cd, which indicates that the light source in a unit of spherical degree of stereo angle (the object surface of the angle formed by the point light source) emitted in the luminous flux. 1 cd = 1 lm / 1 sr (sr: the stereo angle of the sphere of the degree of the unit).

Brightness

(cd/m2)

Brightness is the intensity of light emitted by an object as seen by the eye from a given direction. The unit is candela/m2 [cd/m2], the symbol is L, indicating that the luminous flux of the luminous body in a particular direction per unit of stereo angle per unit of area, which is equal to the luminous intensity of 1 candela emitted from 1 square meter of surface.

Color Temperature

( Color Temperature )

When the color of the light emitted by the light source and the black body at a certain temperature in the same color of radiation, the temperature of the black body is known as the color temperature of the light source, the color temperature of the absolute temperature of the K (Kelvin, Kelvin = degrees Celsius + 273.15) said.

Color rendering property

In principle, artificial light should be the same as natural light, so that the human eye can correctly identify the color of things, of course, depending on the location and purpose of lighting.

The degree of color rendering of the light source for the object is called color rendering. It is often called the "color rendering index" (Ra). Color rendering refers to the relationship between the true color of the thing (its own color) and the color displayed under a standard light source.Ra value is determined by the DIN6169 standard definition of the eight test colors in the standard light source and the test light source to do a comparison, the smaller the color difference is that the color of the light source under test color rendering is better.

The light source with Ra value of 100 indicates that the color of things displayed under its light is the same as under the standard light source.

Basic Information

LED (Light Emitting Diode), light-emitting diode, is a solid-state semiconductor device, which can be directly converted into light energy. the heart of the LED is a semiconductor wafer, the wafer is attached to one end of the LED lamps on a bracket, is the negative pole, the other end of the power supply is connected to the positive pole, the entire wafer is encapsulated in epoxy resin. Epoxy resin encapsulation. Semiconductor chip consists of two parts, one part is a P-type semiconductor, in which holes dominate, the other end is a N-type semiconductor, this side of the main electron. However, when these two semiconductors are connected, a "P-N junction" is formed between them. When the current through the wire on the chip, the electrons will be pushed to the P region, in the P region of the electron and hole complex, and then will be in the form of photons of energy, which is the principle of LED light-emitting. And the wavelength of light to determine the color of light, is determined by the formation of P-N junction material. SMD LED

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LED applications

Given the LED's own advantages, the current main applications in the following areas:

(1) display, traffic signals show the application of the light source LED lamps with shock resistance, shock resistance, fast light response speed, power saving and long life and other characteristics, are widely used in a variety of indoor and outdoor displays. Divided into full-color, dual-color and monochrome display, the country **** more than 100 units in the development and production. Traffic signals mainly with ultra-high brightness red, green, yellow LED, because the use of LED signals both energy-saving, high reliability, so in the country, traffic signals are being gradually updated, and the promotion of fast, the market demand is very large, is a very good market opportunity.

(2) Applications in the automotive industry Automotive lamps include automotive interior instrument panels, audio indicators, switch backlighting, reading lamps and external brake lights, taillights, sidelights and headlamps. Automotive incandescent lamps are not resistant to vibration and impact, easy to damage, short life, and need to be replaced frequently. 1987, China began to install high level brake lights in cars. Due to the fast response speed of LED, can remind the driver to brake early, reduce rear-end accidents, in developed countries, the use of LED manufacturing central rear high brake lights have become the standard parts of the car, the United States HP in 1996, the introduction of semiconductor lighting LED automotive taillight module can be combined at will into a variety of automotive taillights. In addition, in the automobile instrument panel and a variety of other lighting part of the light source, can be used to bear the ultra-high brightness light-emitting lamps, so they are gradually used in the LED display. China's automobile industry is in a period of great development, is the promotion of ultra-high brightness LED excellent time. In recent years, it will form an annual output value of 1 billion yuan, and within 5 years, it will form an annual output value of 3 billion yuan.

(3) LED backlighting to efficient side light-emitting backlighting is the most striking, LED as the LCD backlighting applications, with a long life, high luminous efficiency, non-interference and cost-effective features, has been widely used in electronic watches, cell phones, BP machines, electronic calculators and card machines, with the increasing miniaturization of portable electronics, LED backlighting is more advantageous, and thus the backlighting LED is the key device of cell phone, an ordinary cell phone or SmarTone needs to use about 10 LED devices, while a color screen and cell phone with camera function needs to use about 20 LED devices. At this stage, the amount of cell phone backlighting is very large, 3.5 billion LED chips a year. At present, China's cell phone production is very large, and most of the LED backlight or imported, for domestic LED products, this is an excellent market opportunity.

(4) LED lighting light source early products with low luminous efficiency, light intensity generally can only reach a few to dozens of mcd, suitable for indoor occasions, in home appliances, instruments, communication equipment, microcomputers and toys and other applications. Currently the direct goal is to LED light source to replace incandescent and fluorescent lamps, this substitution trend has begun to develop from the local application areas. Japan in order to save energy, is planning to replace incandescent light-emitting diode project (called "Light up Japan"), the first five years of the budget of 5 billion yen, if the LED replacement of half of the incandescent and fluorescent lamps, the annual savings equivalent to 6 billion liters of crude oil energy, the equivalent of five 1.35 × 106kW nuclear power plant's power generation, and can reduce carbon dioxide and other greenhouse gases, improve the environment in which people live. It can also reduce the production of carbon dioxide and other greenhouse gases, and improve the environment in which people live. China also invested 5 billion in 2004 to vigorously develop energy-saving and environmentally friendly semiconductor lighting program.

(5) other applications such as a children's welcome flash shoes, walking built-in LED will flash light, only Wenzhou area a year to use 500 million light-emitting diodes; the use of light-emitting diodes as an electric toothbrush power indicator, according to the domestic production of the manufacturer, the

LED lamps and lanterns (5) The company has a small number of health care toothbrushes on the market, it is expected that when mass production requires 300 million per year. Mass production is expected to require 300 million light-emitting lights per year; LED Christmas lights are in vogue, due to novelty, colorful, unbreakable and low-voltage use of security, recently in Hong Kong and other Southeast Asian regions, sales are strong, by the people generally welcome, is threatening and replacing the existing electric bulbs in the Christmas market.

(6) household indoor lighting LED products are increasingly popular, LED downlights, LED ceiling lights, LED fluorescent lamps, LED fiber-optic lamps have quietly into the family!

LED lighting colors

LED (LightingEmittingDiode) lighting that is light-emitting diode lighting, is a semiconductor solid light-emitting device. It is the use of solid semiconductor chips as light-emitting materials, in the semiconductor through the carriers occurring composite release of excess energy and cause photon emission, directly emit red, yellow, blue, green, cyan, orange, purple, white light.LED lighting products is the use of LED as a light source to create the lighting apparatus.

Lighting principle

LED is made of Ⅲ-IV compounds, such as GaAs (Gallium Arsenide), GaP (Gallium Phosphide), GaAsP (Gallium Phosphide Arsenide) and other semiconductors, the core of which is the PN junction. Therefore it has a general P-N junction I-N characteristics, that is, forward conduction, reverse cutoff, breakdown characteristics. In addition, under certain conditions, it also has light-emitting properties. Under forward voltage, electrons are injected into the P region from the N region, and holes are injected into the N region from the P region. Into each other region of the minority carriers (oligon) part of the majority of carriers (polyon) with the complex and light-emitting.

LED Advantages

The intrinsic characteristics of the LED determine that it has many advantages, such as:

One, small size

The LED is basically a very small wafer encapsulated in an epoxy resin, so it is very small and very light.

Two, low power consumption

LED power consumption is quite low, DC drive, ultra-low power consumption (single tube 0.03-0.06 watts), electro-optical power conversion close to 30%. Generally speaking, the working voltage of LED is 2-3.6V, and the working current is 0.02-0.03A; that is to say, it consumes no more than 0.1W of electricity, and the same lighting effect saves nearly 80% energy compared with traditional light sources.

Three, long service life

Some people call the LED light source for long life lamp. It is a solid cold light source, epoxy resin encapsulation, there is no loose part of the lamp body, there is no filament luminescence easy to burn, heat deposition, light decay and other shortcomings, in the appropriate current and voltage, the service life of up to 60,000 to 100,000 hours, more than 10 times the life of traditional light sources.

Four, high brightness, low heat

LED using cold light-emitting technology, heat is much lower than ordinary lighting.

Fifth, environmental protection

LED is made of non-toxic materials, unlike fluorescent lamps containing mercury will cause pollution, while LED can also be recycled. There is no ultraviolet and infrared in the spectrum, neither heat nor radiation, small glare, cold light source, safe to touch, belonging to the typical green lighting source

Sixth, strong and durable

LEDs are completely encapsulated in epoxy resin inside, more than the bulb and fluorescent tubes are sturdy. There are no loose parts in the body of the lamp, making the LED not easy to damage. LED lights

Seven, multi-variable

LED light source can use red, green, blue three-color principle, under the control of computer technology so that the three colors have 256 levels of gray scale and arbitrary mixing, you can produce 256 × 256 × 256 = 16777216 kinds of colors, the formation of different combinations of light color changeable, to achieve colorful and dynamic changes in the effect of the various images.

Eight, advanced technology

Compared with the monotonous luminous effect of the traditional light source, LED light source is a low-voltage microelectronic products. It successfully integrated computer technology, network communication technology, image processing technology, embedded control technology, so it is also a digital information technology products, semiconductor optoelectronic devices, "high-tech" technology, with on-line programming, unlimited upgrades, flexible and versatile features.

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LED Disadvantages

The first point LED light-emitting diode has been globally recognized as the most efficient artificial lighting technology. Although there are still many people in the country under the misleading business that LED is used to replace the LCD liquid crystal display technology, but in fact this energy-efficient lighting technology from the 1960s and 1970s has begun to be applied, and now from a variety of indicators, street lamps, holiday lights and then to notebooks, TV backlighting are widely used in LED lighting. Because of its high energy efficiency, it is widely recognized that replacing traditional light bulbs and fluorescent lamps with LED lights is a very environmentally friendly practice.

However, a recent survey conducted by the University of California, Irvine, shows that the environmental benefits of using LEDs are likely to be offset by the toxic substances they contain. In the study, conducted by the university's Department of Social Ecology and the Public ****Health Program***, they analyzed red, yellow, green and blue LEDs in common Christmas tree light sets on the market, which included both high-brightness LEDs and low-brightness products.

The results showed that these LED lights contained antimony, arsenic, chromium, lead and a variety of other metallic elements. Among them, the toxic element content of some LED lights has exceeded the standards set by the regulatory authorities. For example, in the low-brightness red LED lights, the researchers found that their lead content exceeded the standard by up to eight times, and nickel content also exceeded the standard by 2.5 times.

In fact, in California law, the vast majority of LED lights have been clearly defined as toxic waste, which can contaminate soil and groundwater if disposed of in landfills. And if the LED lights are broken, they may also cause damage to human health in direct contact. But so far, neither governments nor the public know much about the environmental and health dangers of LED lights.

The report said that arsenic, lead, nickel and copper elements in LEDs have the most serious impact on humans and the environment, and that more detailed and in-depth investigations should be carried out in the future to promote the government's development of specifications for the safe use and recycling of LED products. In short, it should be clear to everyone that while LEDs are very energy efficient, they are by no means a completely environmentally friendly option, and simply contain different potential dangers than other lighting technologies.

The second point LEDs need to be narrower due to the individual light-emitting surfaces, and are usually massively integrated into circuit boards to form a relatively large light source, which can result in a large amount of heat buildup, and sometimes breakdown of the circuit board. So the heat dissipation of LED lights must be good.

Third point, the human eye is the most unacceptable is blue light and UV light (i.e., ultraviolet light), blue light kills the ability of human eye active cells is 10 times the green light, and UV light kills the ability of human eye active cells and blue light 10 times, long-term exposure to a large number of low wavelengths of blue light can be a large number of kill the active cells of the human eye, and ultimately cancerous formation of plaques. LED white light formation is mainly by 450-455NM wavelength blue light excitation phosphor, which the lower the wavelength the stronger the ability to strike, usually the wavelength of the LED factory control within 500NM, i.e., 450-455NM, or 455-460NM, belongs to the strongest damage to the band, if the wavelength becomes bigger, then the ability to excitation of the phosphor decreases, the efficiency is reduced. People in pursuit of brightness, usually more will strengthen the blue light intensity of the LED, the longer the lighting time, the faster the phosphor attenuation, which in turn leads to the human eye exposure to the blue light band of light the more intense, thus causing damage to the human eye.

So LED lamps and lanterns in road traffic LED navigation instructions, LED street lamps, LED desk lamps on the use of a certain disadvantage, easy to make people in the use of the process of dizziness, uncomfortable feeling, and even long-term use will turn into eye injuries, so that the chances of suffering from eye diseases will be increased.

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LED design concept

The emergence of LED breaks the traditional light source design methods and ideas, there are two latest design concepts.

1. Scenario Lighting: It is the scenario lighting proposed by Philips in 2008 to design lamps and lanterns with the needs of the environment. Scenario lighting to the place as a starting point, aims to create a beautiful, gorgeous light environment, to go to the scene to accentuate the effect of the scene, so that people feel the atmosphere of the scene.

2. Mood Lighting: It is the mood lighting proposed by Cassio in 2009 to design lamps and lanterns with the needs of people. Mood lighting is a human emotion as a starting point, from the human point of view to create a moody light environment. Mood lighting and scenario lighting is different, mood lighting is dynamic, can meet the spiritual needs of people's lighting, so that people feel the mood; and scenario lighting is static, it can only emphasize the scene of the need for light, and can not express the human emotions, in a sense, mood lighting covers scenario lighting. Mood lighting contains four aspects: one is environmental protection and energy saving, two is healthy, three is intelligent, four is humanized.

The general manager of CASIO, Mr. Wu Yulin, has written a book "Mood Lighting Book", which is China's first book to lead the trend of LED lighting design and breaks the monopoly of design theories by foreign giants for a long time, and makes the application of LEDs more easily for the market needs. Will be the latest mood lighting design concepts contributed to share with you, through this hope that more experts, scholars and designers to participate in the discussion and put forward Jianyi.

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LED light-emitting principle

LED flashlight Light-emitting diode is made of Ⅲ-IV compounds, such as GaAs (Gallium Arsenide), GaP (Gallium Phosphide), GaAsP (Gallium Phosphide Arsenide) and other semiconductors, the core of which is the PN junction. Therefore it has a general P-N junction I-N characteristics, that is, forward conduction, reverse cutoff, breakdown characteristics. In addition, under certain conditions, it also has light-emitting properties. Under forward voltage, electrons are injected into the P region from the N region, and holes are injected into the N region from the P region. A part of the minority carriers (oligons) entering each other's region compound with the majority carriers (multiplets) and emit light.

Assuming that luminescence occurs in the P region, then the injected electrons and valence band holes are directly compounded and luminescence, or first captured by the luminescence center, and then compounded with the holes luminescence. In addition to this luminescence composite, there are also some electrons are non-luminescent center (the center of the conduction band, mesoband near the middle) capture, and then composite with the hole, each time the energy released is not large, can not form visible light. Luminescent composite amount relative to the non-luminescent composite amount of the larger the ratio, the higher the light quantum efficiency. Since the composite is luminescent in the oligon diffusion region, the light is generated only within a few μm near the PN junction surface.

Theory and practice have shown that the peak wavelength of light λ and the light-emitting region of the semiconductor material forbidden bandwidth Eg related to the

λ ≈ 1240/Eg (nm)

Equation of the unit of Eg for the electron volt (eV). If you can produce visible light (wavelength in 380nm violet ~ 780nm red light), semiconductor materials, Eg should be between 3.26 ~ 1.63eV. Light longer than the wavelength of red light is infrared light. Now there are infrared, red, yellow, green and blue light-emitting diodes, but the cost and price of blue light diodes are very high, and their use is not common.

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White LED for lighting

The relationship between the visible light spectrum and LED white light. As we all know, the visible light spectrum of the wavelength range of 380nm ~ 760nm, is the human eye can feel the seven colors of light - red, orange, yellow, green, green, blue, blue, violet, but each of these seven colors of light is a monochromatic light. For example, the peak wavelength of the LED red light 565nm. In the visible spectrum is no white light, because white light is not monochromatic light, but by a variety of monochromatic light synthesis of composite light, just as the sun is synthesized by seven kinds of monochromatic light white light, and color television white light is also synthesized by the three primary colors of red, green and blue. It can be seen that, to make the LED emit white light, its spectral properties should include the entire visible spectral range. However, to manufacture LEDs with such properties is not possible under the current process conditions. According to people's research on visible light, the white light visible to the human eye, at least two kinds of light need to be mixed, that is, two wavelengths of light-emitting (blue light + yellow light) or three wavelengths of light-emitting (blue light + green light + red light) mode. The above two modes of white light, all need blue light, so ingesting blue light has become the key technology for manufacturing white light, that is, the current major LED manufacturing companies chasing the "blue light technology". At present, the international mastery of "blue light technology" manufacturers only a few, so the promotion and application of white LED, especially the promotion of high brightness white LED in our country there is a process.

White LED process structure and white light source. For general lighting, in the process structure, white LED is usually formed using two methods, the first is the use of "blue light technology" and phosphor with the formation of white light; the second is a variety of monochromatic light mixing methods. Both methods have been able to successfully produce white light devices. White LED lighting new light source application prospects. In order to illustrate the characteristics of white LED, first look at the current situation of the lighting lamp light source used. Incandescent lamps and tungsten halogen lamps, the luminous efficacy of 12 to 24 lumens / watt; fluorescent lamps and HID lamps with a luminous efficacy of 50 to 120 lumens / watt. For white LED: in 1998, white LED luminous efficiency is only 5 lumens / watt, to 1999 has reached 15 lumens / watt, this indicator and general household incandescent similar, and in 2000, white LED luminous efficiency has reached 25 lumens / watt, this indicator and tungsten halogen lamps are similar. A company predicted that by 2005, the luminous efficacy of LED up to 50 lumens / watt, by 2015, the luminous efficacy of LED can be expected to reach 150 ~ 200 lumens / watt. At that time, the white LED operating current will be up to ampere level. This shows the development of white LED lighting source for home use, will become a possible reality.

Ordinary lighting incandescent lamps and tungsten halogen lamps, although cheap, but low light efficiency (the thermal effect of the lamp white power consumption), short life, maintenance workload, but if the white LED for lighting, not only the high light efficiency, but also a long life (more than 10,000 hours of continuous working time), almost no need for maintenance. At present, the German Hella company used white LED development of aircraft reading lights; Australia's capital city of Canberra, a street has used the white LED for street lighting; China's urban traffic management lights are also using white LED to replace the early traffic order indicator. It can be predicted that in the near future, white LED will enter the family to replace the existing lighting.

LED light source with the use of low-voltage power supply, less energy consumption, applicability, high stability, short response time, no pollution of the environment, multi-color light-emitting, etc., although the price is more expensive than the existing lighting equipment, is still considered to be that it will inevitably existing lighting devices.

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LED dimming control

Traditionally, the dimming of the LED is the use of a DC signal or filter PWM to regulate the forward current in the LED to complete. Decreasing the LED current will serve to regulate the intensity of the LED light output, however, changes in forward current will also change the color of the LED as the LED chromaticity will change with the current. Many applications (e.g. automotive and LCD TV backlighting) cannot allow any color drift of the LEDs. In these applications, wide range dimming is necessary due to the varying light variations in the surroundings and the sensitivity of the human eye to even small changes in light intensity. The practice of controlling LED brightness by applying a PWM signal allows dimming of the LEDs to be accomplished without changing the color.

What is often referred to as True Color PWM dimming uses a PWM signal to adjust the brightness of the LEDs.

There are three common ways to adjust the brightness of LEDs:

(1) Using SET resistors, connecting different conversion resistors in parallel at both ends of the LED driver control IC pin RSET, and using a DC voltage to set the current of the LED driver control IC pin RSET to change the LED's forward operating current, to regulate the luminous brightness of ALEDs.

(2) Adopting PWM technology, using PWM control signals to adjust the luminous brightness of ALEDs by controlling the duty cycle of the LED's forward operating current.

(3) Linear regulation, the easiest way is to use an external SET resistor in the LED driver control C to realize the dimming control of the LED. Although, this dimming control method is effective, it lacks flexibility and does not allow the user to change the light intensity. Linear regulation, on the other hand, reduces efficiency and causes a color shift of the white LED toward the yellow spectrum. The shift may be slight, but can be detected in sensitive applications.

The use of digital or called PWM LED dimming control method to greater than 100HZ switching operating frequency, pulse-width modulation method to change the pulse duty cycle of the LED drive current to actualize the LED dimming control, the choice of greater than 100HZ switching dimming control frequency is mainly to avoid the human eye to feel the phenomenon of dimming flicker. Luminous brightness is proportional to the PWM pulse duty cycle, in this dimming control method, can be in a high degree of dimming ratio range to keep the LED light-emitting color unchanged, the use of PWM LED dimming control of dimming ratio range up to 3000:1.

Linear LED dimming control method is to use the analog dimming control method, in the simulation of dimming control, through the adjustment of the LED's forward The linear LED dimming control method is to use the analog dimming control method, under the analog dimming control, by adjusting the LED forward current to achieve the LED dimming control, dimming control range of up to 10:1.

If you want to further reduce the LED forward current will produce changes in the LED light color and can not accurately regulate the control of the LED forward current problem.