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What are Light Emitting Diodes?
Light-emitting diode, referred to as LED, is a commonly used light-emitting device, which releases energy and emits light through the recombination of electrons and holes. It is widely used in lighting field.
Light-emitting diodes efficiently convert electrical energy into light energy. It has a wide range of uses in modern society, such as lighting, flat panel display, medical devices, etc.
This kind of electronic component appeared as early as 1962. In the early days, it could only emit red light with low luminosity. Later, other monochromatic versions were developed. At the beginning, it was used as indicator lights, display panels, etc.; with the continuous advancement of technology, light-emitting diodes have been widely used in displays and lighting.

Introduction to Light Emitting Diodes

Light-emitting diodes are referred to as LEDs for short. Made of compounds containing gallium (Ga), arsenic (As), phosphorus (P), nitrogen (N), etc.
Visible light can be radiated when electrons and holes recombine, so they can be used to make light-emitting diodes. It is used as an indicator light in circuits and instruments, or as a text or number display. Gallium arsenide diodes emit red light, gallium phosphide diodes emit green light, silicon carbide diodes emit yellow light, and gallium nitride diodes emit blue light. Due to chemical properties, it is divided into organic light-emitting diode OLED and inorganic light-emitting diode LED.
LEDs were initially used for indicative lighting of instruments and meters, and were later extended to traffic lights. Then to landscape lighting, vehicle lighting and mobile phone keyboard and backlight. Later, a new technology of micro light-emitting diode (micro-LED) was developed, which greatly reduces the size of the original light-emitting diode. The red, blue and green miniature light-emitting diodes that can emit light independently are arranged in an array to form a display array, which is used in the display technology field. Micro light-emitting diodes have self-luminous display characteristics, which are more efficient than self-luminous organic light-emitting diodes (OLEDs), have a longer life, and are relatively stable materials that are not easily affected by the environment.

LED Light Features

LED lights are light-emitting diodes, which use solid semiconductor chips as light-emitting materials. Compared with traditional lamps, LED lamps are energy-saving, environmentally friendly, and have better color rendering and response speed.
(1) Energy saving is the most prominent feature of LED lights
In terms of energy consumption, the energy consumption of LED lamps is one-tenth of that of incandescent lamps and one-fourth of that of energy-saving lamps. This is one of the biggest features of LED lights. Nowadays, people advocate energy saving and environmental protection. It is precisely because of this feature of energy saving that the application range of LED lights is very wide, making LED lights very popular.
(2) Can work in high-speed switching state
When we usually walk on the road, we will find that every screen or picture composed of LEDs is unpredictable. This shows that LED lights can perform high-speed switching. However, for the incandescent lamps we usually use, such a working state cannot be achieved. In normal life, if the number of switches is too many, it will directly cause the filament of the incandescent lamp to break. This is also an important reason for the popularity of LED lights.
(3) Environmental protection
LED lights do not contain any heavy metal materials such as mercury, but fluorescent lamps contain them, which reflects the environmental protection characteristics of LED lights. People nowadays attach great importance to environmental protection, so more people are willing to choose environmentally friendly LED lights.

(4) Fast response
Another outstanding feature of LED lights is that the response speed is relatively fast. As long as the power is turned on, the LED light will light up immediately. Compared with the energy-saving lamps we usually use, its response speed is faster. When a traditional light bulb is turned on, it often takes a long time to illuminate the room, and it can only be turned on after the bulb is completely heated.
(5) Compared with other light sources, LED lights are more "clean"
The so-called "clean" does not refer to the cleanliness of the surface and interior of the lamp, but that the lamp is a cold light source, which will not generate too much heat and will not attract those heat-loving insects. Especially in summer, there will be a lot of bugs in the countryside.
Incandescent lamps and energy-saving lamps will generate heat after being used for a period of time. This heat is just what bugs like, and it is easy to attract bugs. This will undoubtedly bring a lot of pollutants to the surface of the lamp, and the excrement of bugs will also make the room dirty. However, the LED light is a cold light source and will not attract insects, so that there will be no excrement of insects. Therefore, LED lights are more "clean".
Semiconductor light-emitting diodes have a wide range of applications, low power consumption, long service life, low carbon and environmental protection. The application of semiconductor light-emitting diodes in my country is very extensive, and many lighting equipment in residents' homes use semiconductor light-emitting diodes. Most street lamps also use semiconductor light-emitting diode street lamps as lighting sources, and some road lighting lamps are also combined with solar technology, which can save a lot of electricity. According to different materials, photodiodes can be divided into gallium aluminum arsenide photodiodes, aluminum arsenide phosphorous photodiodes, gallium phosphide photodiodes and aluminum arsenide photodiodes.

LED related parameters

Several important aspects of LED optical parameters are: luminous flux, luminous efficiency, luminous intensity, light intensity distribution, and wavelength.
Luminous efficiency and luminous flux
Luminous efficiency is the ratio of luminous flux to electric power, and the unit is generally lm/W. Luminous efficiency represents the energy-saving characteristics of the light source, which is an important index to measure the performance of modern light sources.
Luminous Intensity and Light Intensity Distribution
LED luminous intensity is to characterize its luminous intensity in a certain direction. Since the light intensity of LEDs varies a lot at different spatial angles, we have studied the light intensity distribution characteristics of LEDs. This parameter has great practical significance and directly affects the minimum viewing angle of the LED display device. For example, for large LED color displays in sports venues, if the distribution range of the selected LED single tube is very narrow, then the audience facing the display at a relatively large angle will see distorted images. And traffic sign lights also require a wider range of people to identify.

wavelength
For the spectral characteristics of LEDs, we mainly look at whether its monochromaticity is good, and we should also pay attention to whether the main colors of red, yellow, blue, green, and white LEDs are pure. Because in many occasions, such as traffic lights, the color requirements are relatively strict, but according to observations in some LED signal lights in my country, the green is blue, and the red is deep. Judging from this phenomenon, it is very necessary and meaningful for us to conduct special research on the spectral characteristics of LEDs.

The main classification of light emitting diodes

Light-emitting diodes can also be divided into: ordinary monochromatic light-emitting diodes, high-brightness light-emitting diodes, ultra-high-brightness light-emitting diodes, color-changing light-emitting diodes, flashing light-emitting diodes, voltage-controlled light-emitting diodes, infrared light-emitting diodes, and negative resistance light-emitting diodes.
There are two control modes of LED, constant current and constant voltage, and there are many dimming methods, such as analog dimming and PWM dimming. Most LEDs use constant current control, which can keep the LED current stable, not susceptible to VF changes, and prolong the service life of LED lamps.

Monochrome LED
Ordinary monochrome light emitting diode
Ordinary monochromatic light-emitting diodes have the advantages of small size, low working voltage, small working current, uniform and stable light emission, fast response speed, and long life. It can be driven by various DC, AC, pulse and other power sources. It is a current-controlled semiconductor device, and it needs to be connected in series with a suitable current-limiting resistor.
The luminous color of an ordinary monochromatic light-emitting diode is related to the wavelength of light, and the wavelength of light depends on the semiconductor material used to manufacture the light-emitting diode. The wavelength of red LEDs is generally 650-700nm; the wavelength of amber LEDs is generally 630-650nm; the wavelength of orange LEDs is generally about 610-630nm; the wavelength of yellow LEDs is generally about 585nm; Generally 555 ~ 570nm.

High Brightness Monochrome Light Emitting Diode
High-brightness monochromatic light-emitting diodes and ultra-high-brightness monochromatic light-emitting diodes use different semiconductor materials from ordinary monochromatic light-emitting diodes, so the intensity of light is also different. Usually, materials such as gallium aluminum arsenide (GaAlAs) are used for high-brightness monochromatic light-emitting diodes; Ultra-high brightness monochromatic light-emitting diodes use materials such as gallium indium arsenide phosphide (GaAsInP); Ordinary monochromatic light-emitting diodes use materials such as gallium phosphide (GaP) or gallium arsenide phosphide (GaAsP).