Features of LED TVs with Edge and Direct backlighting. What is this ice TV

LED lighting in modern TVs with liquid crystal screens today has several technological solutions. In an effort to increase the color gamut to better display colors, TV display manufacturers have developed new backlighting methods that differ from conventional LEDs.

RGB LED

To obtain a wide spectrum of white light, they began to use triads of LEDs consisting of blue, green and red colors in the backlight.

It was an alternative to WLED with a white LED and a smaller color gamut. The lighting system with three different LEDs is called RGB LED. The color gamut of screens with RGB backlighting was greater than those using only white LEDs or using fluorescent CCFL lamps. But there were also disadvantages: price, size, weight, different times aging of LEDs of different colors, which over time led to image color detuning. Therefore, we abandoned RGB LED backlighting in favor of WLED.

RGB LED

WLED

Given the shortcomings of RGB backlighting, TV manufacturers have settled on using “white” LEDs. They are located either on the sides of the case or in one array behind the LCD matrix. With the help of special diffusers, the light from the diodes is evenly distributed across the entire screen.

Although we call these LEDs “white,” they actually emit blue light, which passes through a yellow filter and is converted to white. Therefore, the use of white LEDs in screens back in 2010 gave a bluish tint to the image.

Over time, manufacturers have improved the components, and the WLED backlight has become quite functional, but as far as the light spectrum is concerned, some imbalances in the display of colors are noticeable.

This peak in blue is due to the blue LED. Using a filter you can get white light. And this filtered light hits the red, blue and green subpixels to form the entire spectrum of the limited color gamut. Passing through filters, part of the spectrum is lost, and the flux intensity at the frequency corresponding to blue will be greater than at red and green. Using screen calibration you can get correct colors, but these reasons allow the WLED-backlit screen to display colors in only sRGB space.

If a display with WLED displays colors in the picture close to blue (shades of blue), then the advantage in the spectrum is precisely blue may put pressure on other colors that will be mixed to create the shade. Therefore, shades close to blue may not be displayed correctly.

This problem also occurred when using a CCFL lamp, but there the problem was with green. It was in green that the peak intensity was visible.

Increased color gamut

To expand color scheme Changes have been made to the WLED backlight beyond sRGB and onto the next color standard.

And after the changes they began to use the name GB-R LED or GB-r LED. Now, instead of a white LED, a combined blue and green LED coated with a red phosphor is used.

This technology allows you to get peaks in the spectrum in red, green and blue.

This technology is used today in LG on AH-IPS matrices and in Samsung on PLS. Using GB-r LED technology, you can achieve 99% Adobe RGB coverage.

Some manufacturers use a different method to increase the color gamut in their screens. They take a mixture of blue and red LEDs and use a green phosphor for the filter. This technology is called RB-LED or RB-G LED.

Television manufacturers regularly introduce users to new technologies that improve image quality. Approaches to combining TV screens and LED elements have long been mastered by major companies. Recently, a source of bright and soft glow also goes to displays mobile devices. Users of traditional LED-based lighting can also appreciate the advantages of this solution, but, of course, the backlight of LED screens on TVs looks most attractive. Moreover, it is complemented by other high-tech inclusions used by the developers of this technology.

Backlight device

When creating modules to implement backlighting, LED arrays are used, which can consist of white elements LED glow or multi-colored, such as RGB. The design of the board for equipping the matrix is ​​specially designed for the purpose of integrating a specific media model into the device. As a rule, on the left side of the board there are contact connectors, one of which provides power to the LED backlight, and the others are designed to control its operating settings. A special driver is also used, the function of which is interfaced with the controller.

In its finished form, it is a row of miniature lamps that are connected in groups of 3 pieces. Of course, manufacturers do not recommend interfering with the design of such tapes, but if desired, you can physically shorten or, conversely, make the device longer. Also, the standard backlight of the LED screen provides the ability to adjust the brightness, supports soft start and is equipped with voltage protection.

Classification of lighting by installation type

There are two integration methods LED backlight- straight and end. The first configuration assumes that the array will be located behind the LCD panel. The second option allows you to create very thin screen panels and is called Edge-LED. In this case, tapes are placed around the perimeter inside display. In this case, the uniform distribution of LEDs is carried out using a separate panel, which is located behind the liquid crystal display - usually this type of LED screen backlight is used when developing mobile devices. Adherents of direct illumination point to the high-quality result of the glow, which is achieved thanks to more LEDs, as well as local dimming to reduce color casts.

Application of LED backlight

The average consumer can find this technology in models Sony TVs, LG and Samsung, as well as in Kodak and Nokia products. Of course, LEDs have become more widespread, but it is in the models of these manufacturers that qualitative shifts towards improving consumer qualities are observed this decision. One of the main tasks that faced the designers was to support the performance of the screen with optimal characteristics under conditions of direct influence sun rays. Also recently it has improved in terms of increasing contrast. In terms of advances in screen design, there are noticeable reductions in panel thickness, as well as compatibility with large diagonal. But there are also unsolved problems. LEDs are not able to fully reveal their capabilities in the process of displaying information. However, this did not prevent LED technology from displacing CCFL lamps and successfully competing with the new generation of plasma screens.

Stereoscopic effects

LED-based modules have many capabilities to provide various effects. On at this stage In the development of technology, manufacturers are actively using two stereoscopic solutions. The first provides for angular deflection of radiation fluxes with support for the diffraction effect. The user can perceive this effect while viewing with or without glasses, that is, in holography mode. The second effect involves a shift luminous flux, which is highlighted by the backlight of the LED screen in the direction of a given trajectory in the liquid crystal layers. This technology can be used in combination with 2D and 3D formats after appropriate conversion or recoding. However, regarding the possibilities of combination with 3D images Not everything is going smoothly with LED backlights.

3D Compatible

This is not to say that LED-backlit screens have serious problems interacting with the 3D format, but for optimal perception of such a “picture” by the viewer, special glasses are required. One of the most promising areas of this development is stereo glasses. For example, several years ago nVidia engineers released shutter 3D glasses with liquid crystal glass. To deflect light flows, the LED backlight of the LCD screen involves the use of polarization filters. In this case, glasses are made without a special frame, in the form of a ribbon. The built-in lens consists of a wide array of translucent ones that perceive information from the control device.

Benefits of backlighting

Compared to other backlighting options, LEDs significantly improve the consumer quality of television screens. First of all, the immediate characteristics of the image are improved - this is expressed in increased contrast and color rendition. Top quality processing color spectrum provides an RGB matrix. In addition, the backlight of the LED screen has reduced power consumption. Moreover, in some cases, a reduction in electricity consumption of up to 40% is achieved. It is also worth noting the possibility of producing ultra-thin screens that are lightweight.

Flaws

Users of TVs with LED backlighting criticize them for harmful effects blue-violet radiation to the eyes. Also, bluish tint is observed in the “picture” itself, which distorts the natural color rendition. True, in latest versions TVs with high resolution LED-backlit screens have virtually no such defects. But there are problems with brightness control, which involves pulse width modulation. During such adjustments, you may notice screen flickering.

Conclusion

Today, the segment of TV models with LED technology is in its infancy. The consumer is still assessing the capabilities and advantages that an innovative solution can provide. It should be noted that the operational disadvantages that LED backlight, do not confuse users as much as the high cost. Many experts consider this factor to be the main barrier to the widespread popularization of the technology. However, the prospects for LEDs still remain promising, since their costs will decrease as demand increases. At the same time, other lighting qualities are also being improved, which further increases the attractiveness of this proposal.

We make bright and economical LED lighting from broken LED matrices (how to make the matrix backlight work without a laptop)

• Closet *

Hi all. I decided to write another post in the sandbox (possibly the last one, it’s starting to seem to me that such topics are not welcome here) and again on the DIY topic in which I want to submit interesting idea, well, decide for yourself how to use it. Nowadays, the vast majority of monitors and laptops are equipped with ice-backlit screens (I think few people were surprised when I said this). Often the matrices are broken, and after such repairs I usually end up with a chipped matrix that cannot be restored. We will talk about how to use LEDs and a matrix board to power them.

Of course, you can leave it as a donor, but time has shown that matrices with diode backlighting die extremely rarely (for me, they usually wear broken ones). And the idea occurred to me to use a line of diodes with a standard feeder for my own purposes.

Pros - a fairly bright light source, in theory quite economical (due to the converter), stable brightness, durability, wide supply voltage range (usually from 8 to 19 volts), cons - large electronics board (can be overcome in part, more on that below), Perhaps someone needs to solder. What is a backlight module? This is a line with diodes on which several chains of LEDs connected in series are placed.

And the converter chip itself, located on the matrix board, to which the supply voltage and two control signals are supplied - one to turn on the backlight, the second to control its brightness. To turn on the backlight, we will supply power (10-19 volts) and connect the pins for turning on the backlight and brightness control together and apply 3.3 volts to them. The pinout of the connector is given below. The authorship of this picture belongs to the person from the site rom.by (by the way, all other images are mine and made specifically for this article, but I decided to take the finished one and not redraw it).

We take the common wire from the GND contact, supply power to the LEDVDD and connect inwt_pwm and dispoff# together and supply three volts to them.
We also need a stabilizer to obtain 3.3 volts. In the simplest case, it can be the diagram below. To calculate the resistor, the formula is R = (Usupply-Uzener diode)/Izener diode. We take the average current and the average expected supply voltage. That is, for example, we take an average power supply of 15 volts, a zener diode of 3.3 volts with a stabilization current of 10 mA and we get 1.1 k.
I believe that computer scientists not related to electronics may have problems finding a zener diode - it can be replaced with a TL431 + any low-power silicon diode (in the example 1N4148). Both can be torn out of a dead ATX power supply from a PC. Both circuits are given below. The capacitor, in principle, is almost any 1-10 microfarads. for the second option with tl431, you can not count but take a resistor in the region of 2-3k, and everything works stably. I think that it is even easier to assemble using the second circuit. The circuits are presented below. inwt_pwm and dispoff# on the circuits correspond to PWM and LED_EN, respectively.

The backlight has been launched and you can come up with a use.

But as many will probably rightly note, we have a very inconvenient large board of which we can only use a small part. Unfortunately, I can only give general advice here - call the contacts from the connector to the elements next to the backlight chip, solder the wires to them, make sure that everything works and cut off most of the board, hoping for your luck. By the way, I’ll add that the LEDVDD power usually comes to the fuse located next to the converter and the connector for connecting the LEDs, it is usually designated F1 / F2. But control signals can be output to contact pads nearby and labeled as desired, or even present only on the legs of the elements.

And finally, a photo of what I got. Photos turned off and on were taken at the same time, I took the photo automatically, it shines very brightly and therefore the photo turned on turned out to be dark background.

And a close-up photo of the redesign of another board. Here I filmed it with my phone - it turned out better.

I will say that I have already tried about 15 boards. One flatly refused to start (it’s possible, of course, that it’s faulty, but I’m mentioning it just in case). The rest started up, two suffered from the fact that I cut the board too short (apparently there were some critical circuits in the inner layers that got into the cut area) and after cutting off the “extra” part they stopped working. For the sake of experiment, I also tried to supply full power to the matrix instead of 3 volts to the control pins in order to reduce labor costs. We took 5 test subjects - two boards failed immediately, two more after a day and a half, one works. Therefore, I abandoned this idea and in all subsequent ones I feed the control conclusions as described above. The article does not discuss controlling the brightness of the backlight - there was no such need yet, so I left it for later.

Application is limited only by imagination - you can make a backlight in the workplace, use it for modding in a system unit, as a backlight in a car and a lot of other things. Well, if anyone has any questions, I will try to advise.

Tags: D.I.Y, LEDs, led, lighting, matrix

LED backlighting is another characteristic of TVs and monitors, which has recently complicated the buyer’s choice, requiring him to think twice and make a responsible decision... The fact is that there are more and more LCD TVs, and their types are increasing time multiply.

Indeed, when purchasing a TV, you want not to make a mistake, not to buy something that represents yesterday or the day before yesterday, which you will soon no longer be able to use...

Fortunately, there are no big difficulties in this issue; its importance is greatly exaggerated - more on this below on the page...

Eat good rule: When buying a TV, it is recommended to pay less attention to the names of the technologies used, and be more guided by your impressions of its appearance and image quality.

At the same time, of course, a more modern (and expensive) TV will in most cases be of better quality.

Best results In terms of image quality today, perhaps, the backlight type is Direct (Full) LED. Moreover, it is being improved all the time - now this technology can be used very large number LEDs, which, naturally, has a very positive effect.

Edge LED or its derivatives are also showing increasingly best characteristics, also allowing you to make TVs very thin.

In both cases in best models TVs also use the “Local Dimming” method - Local Dimming. In LG TVs, the backlight using it is called LED plus.

The LCD elements that make up LCD TV panels will not produce images on their own unless they are backlit. Therefore, one or another type of backlighting is necessarily present in modern TVs. It should be borne in mind that technologies are constantly improving, and the type of illumination with the same or similar name next year may be very different in execution from last year. For example, Full screens LEDs now come in nearly as thin as Edge LEDs.

Among the types of TV backlights used or used by SONY are the following:

CCFL (Cold Cathode Fluorescent Lamp).

WCG-CCFL (Wide Color Gamut Cold Cathode Fluorescent Lighting).

RGB LED, or dynamic rgb led (Provides color illumination of individual fragments of the monitor or TV screen. Potentially a very promising technology, since in theory it makes it possible to illuminate the desired area of ​​the screen a certain color. In practice, its theoretical advantages over other types cannot always be realized. See details below on the page).

Full LED. Another name is Direct LED (backlit diodes are located behind the screen evenly over its entire area. This simplifies control and improves quality. But it negatively affects the thickness of the screen.) - Edge LED (The liquid crystal screen is illuminated by white LEDs installed at the top and bottom or on the sides . Allows the production of very thin Slim TVs).

Dynamic Edge LED (In addition, Local Dimming technology is used, which controls the amount of illumination of individual groups of LEDs depending on the displayed image).

Intelligent Dynamic LED. Another name is Full LED or Direct LED (Compared to previous technologies, many more white illuminating LEDs are used, located directly behind the TV screen evenly across its entire area and illuminating the image. By controlling the glow of individual blocks of LEDs, the system can illuminate specific areas of the image, leaving others dark. This technology simplifies operation and improves quality, but has a negative impact on screen thickness.)

Other TV manufacturers, Samsung, Sharp, LG or Toshiba use different technologies to varying degrees. Accordingly, the TV backlight options may also have a different name (you can get a lot of information about technologies on the Internet, but from the point of view of choosing an option for purchase, this information will not give much. It is more important, as we have already said, to evaluate the TV picture visually).

By the way, Full LED (Intelligent Dynamic LED) from Sony is not the same as full LED backlighting in the original sense at the beginning of technology development, when the fluorescent lamp backlight of the LCD matrix of TVs was simply replaced by thousands of individual light-emitting diodes (LEDs).

Compared to previously used technologies, LED LCD backlight(LCD) TVs have quite a few advantages, but there are also disadvantages (inherent to the technology itself):

Disadvantages of LED technology

Initially, this type of backlight does not improve the viewing angles of the LCD (LCD) display
- Thinner models with edge LED backlighting may suffer from uneven screen illumination
- LED backlighting can lead to local unwanted darkening of the image.

Of course, these shortcomings in most cases are successfully overcome in specific models TVs and monitors, since the technology itself is improving all the time. In addition, not only the backlight affects the quality of the picture on the screen.

Advantages of LED TVs

All LED types backlights are more economical
- Technologies such as Edge LED allow you to create TVs with very thin screens
- LED light emitting diodes does not contain mercury (although their manufacturing technology uses gallium and arsenic)

Of course, miracles do not happen. As a rule, a more expensive model will have a higher quality image and is considered the most promising at the moment time type of screen backlight. But the image will be good not only and not necessarily because of the backlight. All other TV devices, including the video processor, can be very good quality. The TV can be very well tuned (what used to be called "calibrated"). In the end, adjustments can be made correctly and appropriately for the given lighting...

From all this, in our opinion, we can conclude:

When choosing a TV, you should not pay much attention to the type of backlight. It will be better if you personally compare the image quality of several models and choose the one whose picture seems nicer.

And choosing which type of backlight is better is the task of manufacturers. While they themselves cannot come to an established opinion (which is natural, because technology is moving forward very quickly).

Take for example RGB LED backlight It is believed to provide a much richer color gamut, extremely sharp and contrasting images on the screen, but it has not become widespread over time. On the contrary, it seems that manufacturers are abandoning it. Firstly, it is much more expensive than other types. It also has technical limitations: the number of backlight elements is limited, since controlling every part of the monitor is too difficult and expensive. As a result, some of the scene illumination that should be bright may be reduced.

Addition:

Lately There is information about successful improvements to this technology by Mitsubishi. Moreover, they are developing completely new type RGB Backlit lighting using a three-color laser. Perhaps soon they will start talking about RGB lighting again in full voice.

Sergey Filinov

LED backlighting of displays is one of the many ways to use LEDs. It began to be used on an industrial scale since 2008. Today, LEDs are installed in the vast majority of liquid crystal (LCD) screens: TVs, monitors, and mobile devices.

Since 2008, LED backlighting has been actively improved and improved. In this article we’ll talk about what LED backlighting is, what it comes in, and how justified its implementation in electronics is.

A little theory

Just 10 years ago, the main light source in LCD screens were fluorescent lamps such as CCFL, HCFL, which played plasma TVs in terms of image quality. The advent of white SMD light-emitting diodes with high luminous efficiency, low power consumption and dimensions has radically changed the situation, thanks to which a new generation of monitors has appeared.

Stores began to actively offer LED TV, without explaining that only LED backlighting was used, and the screen still remained liquid crystal. Large-scale advertising campaigns and beautiful stories from consultants about the advantages of the LED option have contributed to a sharp increase in sales of LED TVs and monitors, thanks to which today they have complete superiority over other types of backlighting.

LED Backlight Types

With the invention of compact ultra-bright LEDs, manufacturers were faced with the question: “How to place them in order to simultaneously obtain an image high quality and save money? In search of an answer, several types of LED backlight have appeared, among which there are two main ones:

• end (Edge), also called side or edge;
• matrix (Direct), assembled on wled or rgb led.

According to the method of controlling the glow, there are also two types of backlight: static and dynamic. In the first case, the brightness of all LEDs changes equally regardless of the image. In the second case, each LED or group individually interacts with the corresponding section of the LCD matrix.

Edge

LEDs in the side lighting are arranged in one of the following ways:

• on the sides;
• above and below;
• along the perimeter.

The choice of one or another placement method depends on the screen size and production technology. This type of backlight uses only white LEDs. The light flux emitted by them passes through the diffuser and the system of light guides, thus illuminating the entire screen.

This method has three important advantages that made it popular. Low cost achieved due to the minimum number of LEDs used and the simplicity of the control system. The ability to create ultra-thin monitor models with a remote power supply, which, due to advertising, have become very popular among buyers. Low energy consumption, which is impossible to achieve in other variations. According to light characteristics edge backlight occupies an average position and strongly depends on the build quality and the used element base. But in general, color rendition is comparable to CCFL technology. Edge-lit TV models cannot achieve high contrast images for two reasons. All LEDs shine with the same brightness, equally illuminating dark and light areas of the screen. Light guides, despite their well-thought-out design, are not able to ensure uniform distribution of light over the entire working surface.

Direct

The back (matrix) illumination is a matrix assembled from several lines with LEDs distributed over the entire area. This method ensures uniform illumination of the entire LCD panel, and most importantly allows for dynamic control. As a result, the developers managed to achieve high image contrast and rich black color.

Direct backlighting is implemented in two ways. The first, most common, is assembled using white LEDs or WLEDs, which are basically the same thing. It can be either static or dynamic, depending on the TV model.

The second suggests using instead of white - RGB LEDs. With their help, it is possible to adjust not only the brightness, but also set any color from the entire visible spectrum. Due to high speed switching LEDs perfectly process the supplied signal and keep up with the rapidly changing picture on the screen. RGB lighting is built only according to the dynamic principle.

Matrix-backlit displays feature excellent contrast and color rendition across the entire screen area. This is their main advantage, which is covered by several disadvantages, namely:

• high cost;
• high power consumption comparable to CCFL technology;
• The case thickness is more than one inch.

If one of the LEDs fails, the entire line goes out. This phenomenon will be reflected on the screen as a darkening of a certain area. You won’t be able to replace a burnt-out element with a similar one yourself, since you can’t find exact copy with the same lens it is almost impossible. As a result, the entire line must be replaced.

About health disadvantages

LED backlight itself, regardless of its implementation method, has several significant drawbacks that affect not the image quality, but the vision. First of all, this is a pulse-width modulation function. With its help, the user adjusts the brightness and, thereby, worsens his health. The essence of the problem is the flickering of LEDs with a frequency above 80 Hz, which manifests itself when the brightness is reduced. Such flickering is not visually detected by the human eye, but it continuously irritates the nerve endings, causing headaches and fatigue in the eyes.

While watching television this disadvantage does not cause much discomfort due to the large distance between the viewer and the screen, as well as low concentration of attention. But users of PCs and laptops with LED backlighting find themselves in a dead end situation. On the one hand, when the monitor brightness is 100%, the pulse width modulation (PWM) function is disabled, but the retina of the eye suffers greatly. On the other side, long work with documents at reduced brightness it is more comfortable for the eyes, but now PWM adds negativity.

In addition, there are other shortcomings that impair vision, the manifestation of which to one degree or another depends on the display production technology. For example, increased radiation of LEDs in the region close to the ultraviolet spectrum.

Those who value their eyesight should opt for a professional series of monitors with CCFL lamps, which are still produced for working with images. They have a high color rendering index and cost less than RGB LED products.

Despite the presence of shortcomings, manufacturers of electronic equipment will not stop using LED backlighting in their devices, and large companies So-called LED TV will continue to be advertised. Because marketing goals still have a high priority. We can only hope that in the near future mass production of monitors will be equipped with higher quality backlighting, operating at a frequency that is safe for the eyes.

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