In the world of mass consumption, such a device as a TV occupies a special place of honor. Thanks to the “blue screens”, a person knows everything about the latest news of the planet, watches his favorite films and series, listens to discussions of celebrities on popular talk shows. If we talk about the principles of TV operation, it should be clarified that at the moment we can only talk about three relevant technologies, including CRT, LCD (LCD) and plasma.
CRT TV
Considered the first of its 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 did not have technological alternatives, and therefore quickly occupied the entire market, but today they are rather archaic. The screen size ranged from 12 to 38 inches with a depth of up to 50 cm. TV consumed from 60 to 150 W / h, hadviewing angle from 160 to 180 degrees and served without interruption for about 20 years.
The principle of operation of a CRT-based TV was to form an image due to electron beams firing from a kinescope. They hit the walls of the phosphor, or rather, its layers of a certain color, including red, blue and green. On the display, a pixel lights up for 1 ms. The image speed was 25 frames per second. The imperfection of technology and the difficulty of drawing a geometrically correct picture led to the fact that TV on kinescopes practically ceased to exist as a species.
LCD TVs
Are by far the most sought after among others. The diagonals of the screens of such TVs start from the same modest 12 inches, but for the largest models this parameter can reach values of more than 100 inches. Weight with a stand reaches 5-10 kg for small representatives and up to 20 kg for large ones. At the same time, 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 Wh.
At the heart of the principle of operation of the LCD TV is the so-called cyanophenyl or a special viscous liquid of strictly ordered molecules. Through the electric field, a current is supplied to them. Under such 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 similarproperty.
The pixels themselves on the LCD display never go out during operation, but only wait until the next signal is given. Then the molecules begin a fast ordered movement, and the picture instantly changes. Also, the principle of operation of a TV with such crystals dictates one of its main characteristics - the response time. It depends on the voltage that is applied to the panel: the higher its value, the faster the molecules turn.
LED TVs
In this case, not another technology is considered, but only a way to improve liquid crystal TV. Often, marketers mistakenly single them out as separate types 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 these TVs, the brightness is regulated by the presence of a backlight. LEDs consume 40% less energy than conventional LCD TVs. The viewing angle averages 170 degrees.
It can be said 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 that vary in price and quality. The only common thing 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 carpeting over the entire display panel, or only around the edges of the screen. The first option is the most acceptable, as it provides both sufficient brightness and image uniformity.
Plasma panels
According to the analysis, these TVs had a high enough popularity to become the second number after the LED TVs described above. Of the technical parameters, large diagonals from 40 to 100+ inches can be noted. It is simply unprofitable to make smaller models due to the general high cost of production. They are distinguished by light weight no more than 6-8 kg, wide viewing angles up to 180 degrees and a very long service life up to 15-17 years. However, power consumption leaves much to be desired - from 70 to 160 W / h.
Recently, these panels have been found to be uncompetitive compared to well-selling LCD TVs. The difficulties were the impossibility of outputting an image higher than FullHD, high cost and severe overheating during operation. The principle of operation of a plasma TV is based on the formation of a picture by means of 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 colored RGB layer of the phosphor. Each pixel holds three capsules. The electrodes deliver an electrical discharge, and the ionized gas or plasma begins to emit one of the three colors that form the image.
DVB-T2 Digital
Exploring the technology of functioning of modern TV, it is impossiblenot to mention also the principles of operation of digital TV as a broadcaster of terrestrial, cable or satellite television. These standards are abbreviated as DVB-T, DVB-C and DVB-S, respectively. The device of the model must 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 the presence of any of the options, then an external receiver or decoder is purchased in addition. 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 due to 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 modern TVs made using liquid crystal technology and having LED backlighting.
The number of dots is four times higher than FullHD, however, in order to notice the difference, a number of viewing conditions must be met. 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 in TVs
In the current realities, the softwareTV filling is no less important than its hardware device. Smart TV or smart TV is a technology inherent in purely modern types of TVs. On such models, any operating system with an existing application store is installed. At the same time, 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 exchange rates, a screen mirroring application, and a number of branded utilities. Thanks to this technological leap, even TV remotes have undergone a change to some extent. Convenient navigation joysticks have been added for them, and their size has been minimized if possible.
3D technology in TVs
When it appeared in mass devices, manufacturers immediately divided into two camps. Some presented models with an active method, in which the glasses on special glasses were alternately closed at a speed of 20 ms, due to which the person observed a stereoscopic image. Others stated that this method causes headaches, and it is best to use the passive version of the technology, 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 withThe 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. TVs of recent years in the upper and middle price segments usually lack the ability to view three-dimensional content.
Features of TV power supplies
This node is included in any device. As a rule, modern TV power supplies are pulsed. At the same time, it is most 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, 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 level required by the TV board.
