How does the LED: the principle of operation, device and features
Many consumers want to learn more about the device LEDs, the principle of operation of these electrical devices, as well as their technological features. This is due to the popularization of LED-lighting in general. Such elements are semiconductor products with an electron-hole transition, which allows the formation of optical radiation.
How did the specific lighting technology appear?
Before considering the principle of operation of LEDs, it is proposed to examine information about how they were created. The very first message about the possibility of emission of light through a solid-state diode belongs to one British experimenter. He made it back in 1907, when he described the process of electroluminescence.
The experiments were repeated in the Russian laboratory, but then they did not attach much importance.In 1961, the first LED technology was patented by employees of an American company. Since then, development processes have been improved. And after some time, it was possible to release an element of high brightness for use in the telecommunications sector.
About basic physical properties
To understand the principle of the LED, it is necessary to understand that each element is a semiconductor diode that converts electricity directly into light radiation. When a direct current passes through it, electrons are transferred to a specific area. In the process of moving, a transition to another energy level occurs with the release of a large amount of light radiation.
To obtain different color effects, activating substances are introduced into the semiconductor material. Monochromatic radiation is most commonly used. With this option, a specific wavelength is used for each diode. The color scheme of the glow can be controlled.
The most important features
Considering the detailed device and the principle of operation of the LED, it is necessary to note some features.Instrument radiation is directly dependent on the angle of radiation, which depends on the design. A certain influence on the intensity of radiation have:
- material used directly to protect the crystal;
- mounted lens.
A semiconductor device is capable of emitting not only narrowly directed, but also diffused light. The temperature of the environment can influence the properties of LEDs. Their brightness depends on it. When the temperature rises, the glow becomes dimmer, and when it falls, it becomes brighter. In this regard, the scope of operation is of particular importance.
High demands are placed on products intended for outdoor use. It should function properly with significant fluctuations in temperature. The brightness of the light during operation should not change significantly. Modern solutions allow for a normal glow, regardless of the ambient temperature.
The principle of operation of the LED is based on high speed action. Radiation appears within a few seconds after direct exposure of the electric current directly to the semiconductor.Manufactured devices may have technological differences, from which will depend on the scope of application.
DIP type LEDs
Semiconductor elements of this category belong to low-current products, so they are mainly used for additional illumination. Usually they are set as indicators or main sources in the garlands. With the advent of more advanced technologies, their production has been significantly reduced.
The principle of operation of a low power LED is relatively simple. The body is cylindrical in shape. It is made of epoxy resin. In the interior there are special leads inserted into the printed circuit board. The rounded cylinder allows you to create a directional luminous flux.
A radiating element in the form of a crystal is placed on the cathode, which resembles a small flag. It is connected to the anode with the help of an ultrafine wire. There are products with two or three crystals that have different colors. If necessary, a control chip is introduced into the housing, which is necessary for controlling the glow.
To increase the level of luminous flux in these LEDs, they began to make four outputs instead of two. However, in this case, the heating of the crystal increased significantly, which led to the limitation of the possible scope of application.
SMD type LEDs
Such elements have a wider purpose, which is associated with the main characteristics. The principle of operation of LEDs of this type allows you to organize the lighting of various formats. Semiconductor devices with a fixed printed circuit board have compact dimensions, so that they can be used even in the smallest lamps.
The base part of the case, on which the crystal is fixed, has a high thermal conductivity, therefore, heat removal is efficient. Usually between the lens and the main element fits the phosphor layer, which provides the ability to neutralize UV light, as well as to set a specific color temperature. In products with diffuse radiation lens is not installed. The element itself is shaped like a parallelepiped.
COB type LEDs
Similar elements began to be used for light bulbs and lamps with a powerful LED.The principle of operation of the products remains the same, but in this case dozens of crystals are attached to the aluminum base using a dielectric adhesive. The resulting matrix is processed by a single layer of phosphor, resulting in a light source with a uniform distribution of the main stream.
One of the varieties of technology is the variant with the distribution of a large number of crystals on the glass surface. According to this scheme, filament lamps are produced, in which the central core of glass, coated with small LEDs and treated with phosphor, acts as a base source.
The principle of the RGB-LED is based on the optical effect, which allows to obtain a variety of color shades as a result of mixing the three main components of the palette. Three crystals are installed on the same matrix at once. To adapt to different conditions, there are several modifications of products. They are made with a common cathode or anode, and sometimes without such (with six main conclusions).
Most often, the light technology is used for the design of billboards, decorating buildings, framing bridges, architectural monuments and other structures.The principle of operation of a multi-color LED is identical. However, design features increase the final cost of products and complicate the circuit connection to the electrical network.
Main technical specifications
There are several parameters that characterize the LEDs.
- Brightness is expressed in units of luminous intensity. It is proportional to the amount of electric current passing through the semiconductor element. As the voltage increases, the brightness level rises.
- The current can be pulsating or constant. It can vary widely. Indicator devices can have a current of only 20 mA, and single watt counterparts - 300-400 mA.
- Wavelength affects the color gamut. Its measurements are made in nanometers. The wave boundaries are mapped to the base components of the palette as needed.
The color spectrum of the emitted radiation changes with the introduction of chemically active substances into the semiconductor material.
The principle of the driver for LEDs
To obtain a stabilized current, a special device is used, which is selected taking into account the following parameters:
- a certain power;
- voltage directly at the output;
- rated current.
Installed drivers can be linear or pulsed. The first of them are designed to provide a smooth stabilization of the electric current at a variable input voltage. Pulse devices form high-frequency pushes in the output channel. They have a high efficiency.
There are also dimmable drivers that provide the ability to adjust the brightness of the LEDs. During the daytime, the radiation intensity can be somewhat reduced, due to which it will be possible to save the resource of semiconductor products and electrical energy.
Questions you are interested in
Now the principle of operation of LEDs has become clear, however many users ask various questions on this topic.
- What parameters affect the service life of a semiconductor device? There is a statement that the LEDs are durable, but this is not entirely true. With a high current strength during operation, the temperature increases, so more powerful devices fail faster.
- Does the color transmission of LEDs deteriorate over time? With prolonged usedevices there is a definite change in shade, but at present there are no standards that allow quantifying this.
- Are the devices harmful to the human eye? Any information about the negative effects of semiconductor elements at this time is missing.
- Why is it necessary to stabilize the electric current passing through the LED device? Even small changes in voltage can lead to fluctuations in brightness.
- How can you get white light? There are three main options. The first one involves mixing the components of a palette using RGB technology. The second option involves applying three phosphors directly to the surface of a semiconductor device, emitting a stream of light in the ultraviolet range. In the third method, the phosphor is applied to the blue element.
As a conclusion
As part of the article, it was possible to consider in detail the principle of operation of the LED. For the "dummies" (people who do not understand the modern technology of LED), it will probably be a valuable tool.It contains the most complete information concerning the structure and functioning of modern lighting systems, which enjoy high popularity.