Translated from English, the abbreviation LED literally means "a diode that emits light." This is a semiconductor device capable of transforming an electric current into light radiation. This is a simple fixture, the design of which is quite different from the usual products for lighting (incandescent, discharge, fluorescent lamps, etc.).
How the LED works, it will be interesting to everyone to know. This device does not have initially unreliable fragile structural elements and a glass bulb (unlike other lamps). The cost of the diodes is so small that it is not much different from the batteries that serve as their power source. The popularity of such products is explained by a number of factors, including their design.
History of occurrence
Considering the question of why LEDs work, you should study the history of their occurrence. The first such device was created in 1962 by the scientist N. Holonyak. It was a monochrome red diode . It had a number of shortcomings, but the technology itself was recognized as promising.
10 years after the creation of the red diode, green and yellow varieties appeared. They were used as indicators in many electronic devices. The intensity of the luminous flux of the diodes due to scientific developments has constantly increased. In the 90s, a lighter was created with a flow efficiency of 1 lumen.
In 1993, S. Nakamura created the first blue diode, which was characterized by high brightness. From this moment it became possible to create any color of the spectrum (including white). Technology has been relentlessly evolving.
When connecting the blue and ultraviolet type of diodes, a white phosphor illuminator is obtained. They began to gradually replace incandescent lamps. By 2005, diodes with a luminous flux of up to 100 lm and even higher were produced. They began to make white lighting devices with different shades (warm, cold).
LED device
To understand how a point LED works, you need to consider its device in detail. This lighting device, according to representatives of the Association for the Development of the Optoelectronic Industry and the Department of Energy, will soon become the most popular source of lighting in ordinary homes, offices, and institutions.
The LED is based on a semiconductor crystal. It passes electric current only in one direction. The crystal is located on a special substrate. She does not conduct current. The case protects the crystal from external influences. It has outputs in the form of contacts, as well as an optical system.
To increase the life of the device, the space between the plastic lens and the crystal itself was filled with a transparent silicone component. To remove excess heat, an aluminum base is used. This is a common device of a modern diode. During operation, it releases a relatively small amount of heat. This is also an advantage of the device.
Principle of operation
Considering how the LED works, you need to understand the basic principle of the operation of such devices. The device of this type has one electron-hole transition. This is due to the different conductivity principle of the illuminator components. One semiconductor has an excess of electrons, and the other has an excess of holes.
Through the alloying process, hole material is enriched with negative charge carriers. If a current is applied at the enrichment site of the semiconductors with opposite charges, a direct bias will result. Through the transition of these two materials, electricity will run.
In this case, fusion of charge carriers with different electrical status occurs in the diode case. When holes and electrons collide, a certain amount of energy is released. This is a quantum of luminous flux. It is called a photon.
LED color
When creating diodes, various semiconductor materials are used. This determines the color that the presented device emits during operation. Different materials can send waves of different lengths into space. This allows the human eye to see one or another color of the visible spectrum.
Studying how LEDs work, semiconductor materials should be considered. Previously, gallium phosphide, ternary compounds GaAsP, AlGaAs were used for such purposes. In this case, the device could send a red, yellow-green light stream into space .
The presented technology is now applied only to indicator devices. Today, indium gallium aluminum (AllnGaP) and gallium indium nitride (InGaN) are used for such products. They withstand a fairly high level of passing current, high rates of humidity and heating. A combination of different types of LEDs is possible.
Color mixing
Modern diode tapes can give out different shades of a light stream. One device can produce a monotonous color. When creating a multi-chip device, it is possible to get a huge number of different shades. Like a TV monitor or a computer, a diode can create any color using the RGB model (stands for red, green, blue).
This is a simple principle to understand how RGB LEDs work. Using this technology, you can create white lighting. To do this, all three colors are mixed in equal proportions.
However, in addition to the technology presented, it is possible to obtain a white glow when a short-wavelength diode (ultraviolet, blue) is connected together with a yellow phosphor type coating. A combination of yellow and blue photons results in a white glow.
Production
To understand how many volts LEDs work, it is necessary to consider the production of these devices. First of all, it should be noted that devices with an RGB matrix are more expensive than luminoforms. Moreover, the latter can achieve high quality lighting.
The disadvantage of phosphors is less light output, as well as different colors (temperature) of the stream. This device is aging faster than the LED. Therefore, lighting devices of both operating principles go on sale. To create indicators, diodes are produced with a consumption of 2-4 V DC voltage (at a current of 50 mA).
To create high-grade lighting, devices with the same voltage consumption, but a higher current level - up to 1 A are required. If you connect diodes in one module in series, the total voltage will reach 12 or 24 V.
Brightness enhancement
Considering the question of what voltage the LEDs work from, it should be said about increasing the brightness of the presented devices. The power of such devices reaches 60 mW. If such diodes are installed in a medium-sized case, 15-20 pieces of light elements will need to be installed.
Diodes with enhanced brightness can carry power up to 240 watts. To ensure normal illumination, such elements will require 4-8 pcs. On sale are devices that can fully illuminate rooms, outdoor advertising, shop windows, etc. Some tapes are created to perform illumination of medium or low intensity.
To connect the presented equipment, control units of the corresponding power are used. For colored ribbons, it is possible to use controllers that control not only the intensity of lighting, but also set the shades and modes of operation of the device.
Glow control
There are a huge number of options for the equipment presented. There are battery-powered LEDs (for example, in flashlights), powered by a fixed network. They are used both for internal and external work. Depending on the application conditions, an appropriate diode protection class is selected.
To adjust the brightness, the voltage is not reduced. To reduce the intensity of the glow applied pulse-width modulation (PWM). In this case, a control unit is purchased.
The presented method consists in applying a pulse-modulated current to the diode. The signal frequency in this case reaches thousands of hertz. The width of the pulses and intervals of pauses may vary. In this case, you can control the glow of the device. The diode in this case does not go out.
Durability
Diodes are considered durable devices. This is due to their design. However, if the LEDs on the lamp do not work, their life may have expired. This can be determined by the saturation of the glow and color change.
Also, experts note that the life of low-power devices is much longer. But even in the brightest tapes or lamps, diodes are guaranteed to work 20-50 thousand hours. Since they do not have brittle structural elements, mechanical stress is more likely to do no harm to such illuminators.
Having studied how the LED works, you can understand the principle of the device of this device, as well as its operational characteristics. This equipment is considered the lighting of the future generation.