In the world of mass consumption, such a device as a TV takes a special place of honor. Thanks to the “blue screens”, a person knows everything about the latest news on the planet, views favorite films and TV shows, listens to celebrity discussions on popular talk shows. If we talk about the principles of the TV, it should be clarified that at the moment we can talk only about three relevant technologies, including CRT, LCD (LCD) and plasma.
Cathode ray tube
They are considered the first of their kind available to the mass consumer on store shelves. At the heart of the device is a kinescope. For this reason, the TV had impressive dimensions and considerable weight up to 40 kg, depending on the diagonal. Previously, they had no technological alternatives, and therefore quickly occupied the entire market, today they are more likely archaism. The screen size ranged from 12 to 38 inches with a depth of 50 cm. The TV consumed from 60 to 150 W / h, had a viewing angle of 160 to 180 degrees and served without interruption for about 20 years.
The principle of operation of a CRT-based television was to form an image by electron beams shooting from a tube. They hit the walls of the phosphor, or rather, its layers of a certain color, including red, blue and green. In this way, a pixel lights up on the display for 1 ms. Image speed was 25 frames per second. The imperfection of technology and the complexity of rendering a geometrically correct picture led to the fact that TV on picture tubes practically ceased to exist as a species.
LCD TVs
They are by far the most popular among others. The diagonal screens of such TVs start with the same modest 12 inches, but for the largest models this parameter can reach values greater than 100 inches. Weight with stand reaches 5-10 kg for small representatives and up to 20 kg for large ones. Moreover, the thickness of the products is only 3-5 cm. As a rule, the service life reaches about 15-20 years. Energy consumption has been reduced to 25–40 W / h.
The principle of operation of an LCD TV is based on the so-called cyanophenyl or a special viscous liquid from strictly ordered molecules. By means of an electric field, current is supplied to them. Under this influence, the molecules begin to simultaneously move and polarize the transmitted light. That is why cyanophenyl was called liquid crystals, because solids in nature have a similar property.
The pixels themselves on the LCD never go out during operation, but are only waiting for the next signal to be sent. Then the molecules begin a quick ordered movement, and the picture instantly changes. Also, the principle of operation of the TV with such crystals dictates one of its main characteristics - response time. It depends on the voltage that is supplied to the panel: the higher its value, the faster the molecules rotate.
LED TVs
In this case, it is not the next technology that is considered, but only a way to improve liquid crystal TV. Often, marketers mistakenly distinguish them in a separate form and call them LED, but the device and the principle of operation of TVs are completely similar to LCD models with one single exception. For TV data, the brightness is adjusted due to the presence of backlight. LEDs consume up to 40% less energy than conventional LCD TVs. The viewing angle is on average 170 degrees.
We can say that by eliminating the flickering effect and increasing the level of dynamic contrast, LED-TVs are the best-selling version of LCD-based models. The backlight itself has undergone many improvements and changes and has received various variations, varying in price and quality. The only thing that is common is that white and RGB LEDs are used. The principle of operation of the TV in terms of the location of the backlight is either carpeted across the entire display panel, or only along the edges of the screen. The first option is the most acceptable, as it provides both sufficient brightness and uniformity of the image.
Plasma panels
According to analytical data, such TVs were quite high in popularity in order to become the second number after the LED-TV described above. Of the technical parameters, large diagonals from 40 to 100+ inches can be noted. Making smaller models is simply unprofitable due to the general high cost of production. They are characterized by light weight of not more than 6-8 kg, wide viewing angles of up to 180 degrees and a very long service life of up to 15-17 years. However, power consumption leaves much to be desired - from 70 to 160 W / h.
Recently, such panels have been found to be uncompetitive compared to well-selling LCD TVs. The difficulties were the impossibility of outputting an image above FullHD, high cost and severe overheating during operation. The principle of operation of a plasma TV is based on the formation of a picture through a panel of glass capsules with a mixture of inert gases of neon and xenon inside. On the back wall of such a cell is a color RGB layer of the phosphor. Each pixel holds three capsules. The electrodes supply an electrical discharge, and ionized gas or plasma begins to emit one of three colors that form the image.
Digital DVB-T2
Studying the functioning technologies of modern TVs, one cannot fail to mention the principles of the operation of a digital television as a broadcast broadcaster, cable or satellite television. These standards are abbreviated as DVB-T, DVB-C and DVB-S, respectively. The model device should include a so-called decoder or tuner. Each of the standards needs its own type of this TV component.
If the model does not provide for any of the options, then an external receiver or decoder is purchased. Today's TVs in the vast majority are able to receive not only analog, but also digital signals. Therefore, in most cases, you do not need to buy additional equipment.
4K TVs
Analyst Alan Crisp believes that these models are the future, but in the present they are not so much in demand because of the relatively high cost and lack of content. All models with 4K resolution (3840 pixels horizontally and 2160 vertically) do not change the general principles of operation of modern televisions made using liquid crystal technology and having LED backlighting.
The number of points is increased four times in comparison with FullHD, however, in order to notice the difference, it is necessary to observe a number of conditions when viewing. For example, the diagonal of the device should be relatively large - at least 40-50 inches, and it is recommended to sit down from the panel within 1.5-2 meters. Otherwise, it will be difficult to detect higher detail on the screen.
Smart TV on TVs
In current realities, the software content of a TV is no less important than its hardware device. Smart TV or smart television is a technology inherent in the purely modern types of televisions. On these models, any operating system with an existing application store is installed. Almost every TV is also equipped with a Wi-Fi module and a network interface for connecting the device to the Internet and other smart devices such as mobile phones and computers.
Software usually includes a pre-installed browser, audio and video player, useful utilities like weather forecast and currency rates, a screen mirroring application and a number of proprietary utilities. Thanks to this technological leap, even TV remotes have undergone a change to some extent. Convenient navigation joysticks were added for them, and they tried to minimize their size if possible.
3D technology in TVs
When appearing in mass devices, manufacturers immediately divided into two camps. Some presented models with the active method, in which the glasses on special glasses were alternately closed at a speed of 20 ms, due to which a person observed a stereoscopic image. Others claimed that headaches appeared from this method, and the passive version of the technology was best used, where the picture was divided into two half-frames, but suffered greatly in detail, because the horizontal or vertical resolution was cut in half.
The principle of operation of modern TVs with 3D-image has not undergone any changes since then. It is worth noting that the technology did not find success with the mass audience and was quickly forgotten. On TVs of recent years, in the upper and middle price segment, the ability to view three-dimensional content is usually absent.
Features of TV power supplies
This node is included in any device. As a rule, modern TV power supplies are pulsed. Moreover, it is often very difficult to find a schematic diagram of such a node. It is believed that this element is often the cause of the failure of the entire TV. This is especially true for blocks assembled on four transistors.
If we consider the features of functioning, then they are quite simple and known to any repairman. The principle of operation of the TV power supply in this case is based on the implementation of secondary power through the use of additional devices that provide energy to the circuit. The PSUs themselves convert the voltage to the required TV level board.