LED backlight for LCD TV panels. What is LED backlighting? Backlight types

Today we will talk about LED backlights in LED TVs. Let's discuss the reasons for their failure and where to buy LEDs.

Preface

The backlighting of the first LCD TVs was made using fluorescent ( CCFL) lamps This backlight has proven itself to be the best, however, it is in many ways inferior to LEDs in terms of brightness, backlight dynamics and energy consumption.

If a powerful inverter is needed to ignite CCFL lamps, then for LEDs a small driver is needed, the main function of which will be to control the current and voltage to power the LEDs.

The main causes of failures of LED TV backlights.

While they have many advantages, LEDs are not without their disadvantages. Increasingly, TVs from well-known brands such as LG or Samsung are being sent for repairs because the LED backlight burns out. Sometimes, the fault of the backlight failure is not the LEDs themselves, but also the improper operation of the TVs. For myself, I identify three reasons for the failure of LEDs.

First reason- this is a miscalculation of the manufacturers themselves. When repairing LED backlights, very often you encounter a situation where, when measuring the current flowing through the LEDs, it turns out that it is too high. For example, in backlight strips, where the maximum current should be about 250 mA, in fact we get about 400-450 mA. Naturally, with such a current, the TV produces a bright picture, but the LEDs quickly burn out. After replacing the LEDs with new ones, you have to reduce the current, thereby saving the TV from repeated repairs, and the owner of the equipment from repeated costs.

Second reason- defective LED. As with any spare parts, from time to time you can get a defective part. In my practice, I came across cases when only one LED burned out, and the rest were in perfect order. Looking through all the LEDs under a microscope for cracks and measuring the current consumption, I did not find any faults. Everything turned out to be normal. Having replaced just one LED, the TV was sent to the owner, after which it continued to serve him faithfully.

Third reason- Constantly watching TV at maximum brightness. This operating mode also affects the durability of the backlight. I recommend always watching TV at a backlight level of no more than 70-75%, as this significantly increases the service life of TVs.

Where is the best place to buy LEDs for repairs?

I used to buy LEDs at the radio market, but recently they have become prohibitively expensive there. After that, on the advice of knowledgeable craftsmen, I buy only from trusted sellers on Aliexpress. Replacing the LED backlights of TV matrices is not very difficult, you can see how I do it in.

Replacing LEDs using a stove table is described

I attach a list of LEDs that I bought below.

Photo	Name	Purchase link
	LEDs 2 W 6 volts on LG size 3535 (large anode pad (+))
	LEDs 6 volts on LG 1 W size 7030
	LEDs 3 volts on LG 0.5 W size 7020
	LEDs 3 volts on LG size 3528 (large anode pad (+))
	LEDs 3 volts on Samsung 1 W size 3537
	3 volt LEDs for Samsung size 7032
	LEDs 3 volts on Samsung 0.5 W size 5630
	LEDs 3535 2 watts 6 volts on LG (large platform cathode (-))

Hi all!

Sometimes, during renovation LCD backlight , difficulties arise in acquiring the necessary luminescent (CCFL ) lamps . In such cases, you can convert the lamp backlight to LED. Such a conversion is not so difficult, and there are no special problems with spare parts.

In this article I offer you the principle of such a reconstruction in the form of some instructions.

Replacement steps LCD backlight to LED:

Disassemble the monitor or TV. After removing the plastic case, carefully disconnect the wires from the board, remove the metal frame from the LCD module and remove the matrix. You need to be especially careful with the matrix so as not to damage the fragile connecting cables. If everything is done correctly, then full access to the electronic board, power inverter and backlight elements will be open.

2. Disconnect the pencil cases from lamps from the matrix or the lamps themselves, if they are installed without canisters.

3. Disconnect old lamps and recycle them. With elements CCFL You also need to be extremely careful, because they contain mercury.

4. We proceed to the replacement stage. First you need to purchase an LED strip, preferably with a reserve so that it is enough to replace all the lamps (measure the length of the lamp and multiply by their number). It should be as narrow as possible and with at least 120 LEDs per meter. To make the backlight more pleasing to the eye, it is better to take LEDs with a white glow.

5. The strip with LEDs must be glued with double-sided tape to where the lamps were. Next, wires from old lamps are soldered onto the contact terminals of the strips and insulated with hot-melt adhesive. You can immediately check the functionality of this design by connecting the wires to an external power source.

6. Now you need to connect the backlight to the power board of the monitor or TV. To do this, you need to find jumpers marked “12 V” and solder the backlight wires there, observing the polarity accordingly. Reassemble the monitor in reverse order and enjoy your invention.

Backlight in this case it will work when the device is connected to the network.

To control the backlight and bring it into normal mode, you will have to work hard. The wires leading to the LEDs must be powered in such a way that it is possible to turn on the backlight when you press the on/off buttons and adjust its brightness. There are 2 options for this:

1.We independently create a power supply circuit and adjust the backlight brightness:

On the power supply chip of a monitor or TV, we look for a plastic box (connector) with wires coming out of it, where each socket is labeled on the board.

Here we are interested in the “DIM” output. It will be responsible for sending a signal to turn on/off and adjust the brightness by changing the duty cycle in the PWM controller. The duty cycle indicator of the pulses changes until the desired brightness level is established, and the limit values will correspond to switching on and off.
Now we need any N-channel field-effect transistor (field transistor). Wires from the LED strip with a minus are soldered to its drain (Drain), the common wire from the backlight is also connected to the source (source), and the gate (gate) is connected through a 100-200 Ohm resistor and any wire is connected to the “DIM” terminal.

We still have wires from the backlight with a plus, we bring them to the +12V power supply on the microcircuit and solder them.

Now we install the backlight in its rightful place and assemble the monitor in reverse order. Don’t forget to be careful and careful when handling the matrix and filters so that dust does not get in and the cables are not damaged. That's it, you can use it.

The second way, more expensive but convenient, is to buy a ready-made LED backlight with your own inverter :

Again, pay attention to the plastic connector and the DIM pin (brightness) and the on/of pin (it’s better to use the pinout).

Using a multimeter, we determine the places on the control unit of old lamps from which the signal for brightness and on/of comes.
Now solder the wires to the found places inverter new LED backlight .

Also, it is better to unsolder the jumpers from the inverter power supply of the old lamps so that the backlight can be regulated by the new inverter.
Without such backlighting, no LCD TV can operate normally, regardless of its brand. We will tell you how you can repair your TV's LED backlight at home using an Lg device as an example, and what you will need for this.

How can you tell if the backlight is broken? Let's assume that the problem with the LCD TV is as follows: it turns on from the remote control, but the screen does not light up (if your TV does not turn on even from the remote control, read about). When pointed at the display flashlight light(i.e. forced illumination is applied), then the image appears. Verdict - the ice driver or similar backlight does not work, perhaps due to the fact that the special lines with soldered LEDs have burned out. You need to disassemble the TV and visually inspect the parts to find a fault.

Attention! You can only open the case of an LCD TV if you have the skills to work with complex devices and a little experience, otherwise it’s better not to risk it.

Remove the back cover For any LG TV, this is not a difficult task, you just need to do everything carefully and without haste: disconnect the legs of the stand and unscrew the mount around the entire perimeter of the product. If the cover does not come off, it means there is a blocking bolt, you should not make any effort, you need to find it and unscrew it.

After removing the back cover, check the output voltage.

If it is normal, we check it voltage ice backlight the screen itself. Its value is only 100V, which indicates that the backlight of the LCD TV is faulty.

These TVs use a special LED set with lenses that are installed across the entire screen area to provide clear illumination. To get to them and repair the LG TV backlight, you must first remove the matrix.

Disassembling the product

The TV has three main boards - main, T-con and power supply, all of which are clearly visible in the photo.

Removing and disassembling the matrix do it yourself - the work is very painstaking, one careless movement, and you can buy a new TV, so without experience it is better not to undertake repairs. Experts highlight the following main points when disassembling the matrix:
- it is necessary to prepare a work area and two tables on which to lay matrices and scattering films;
- Before starting this work, you should thoroughly wash your hands so as not to accidentally leave traces of dirty fingers on the filters and the matrix itself - this can harm the image quality later;
- Special attention should be paid to decoders - one inaccurate movement can lead to a break in the cable.
Subsequent dismantling is carried out in several stages.

Troubleshooting

Now the actual repair of the LED backlight of the TV begins: to do this, you need to carefully unclip all the latches along the contour, remove the plastic frame and remove the diffusing films to expose the LEDs.

Different models of LG TVs will have their own set of LED backlights: for LG 32LN541U there are three rows of 7 LEDs, and for LG 32LB582V there are three rows of 6 LEDs.

In all TVs that use such backlighting, the LEDs are connected in series, so if one of them burns out, the entire system stops working. If the LED driver is faulty, then no voltage is supplied to the entire system, and when one of the LEDs burns out, then the voltage flows, but all the efforts of the device to illuminate the system are in vain: even if you supply 200 volts, the circuit is open.

As we can see from the photograph, the backlight consists of 18 LEDs; during measurements, the voltage without load was 140 V, that is, each one accounted for 7.8 V. When we take into account the voltage drop on each strip and the total load, the conclusion will be as follows: this model uses 6V LEDs.

Finding a burnt-out LED is not easy: if there is no burnout at the mounting location, then you need to check each element separately.

Replacing LEDs

Replacing the Lg TV backlight can be a bit of a hassle. Let's say that the test results revealed several faulty LEDs. It is quite difficult to buy a replacement bar - these parts are not supplied to service centers, you can order them on the manufacturer's website, but this is time-consuming and very expensive. So there is only one way - replace individual diodes, although it will not be easy to find them on the radio market. Experts assure that you can buy already soldered ones, but in good working order; after a long search, these are exactly what we purchased.

Users should be aware that all planks are glued using double sided tape, so you need to warm them up with a special soldering hair dryer so that the adhesive tape comes off. To do this, the bar is fixed in the holder and heated from below with a hairdryer, the tin is melted, and the faulty part is removed. Soldering should be done using exactly the same method to avoid damaging the LED.

Important! All lenses are secured with a compound at the factory, so when removing them you must act very carefully, and each one must then be installed in its original place so as not to disturb the original focusing.

One more nuance: you may come across LEDs whose negative pad is slightly larger than the positive one, so you need to trim the contact point in order to solder the diode. This is what a soldered LED looks like:

The fact that the paint is a little damaged is not a problem. We solder the rest of the LEDs in the same way, and Glue the lenses with superglue. And this is a repaired view of the backlight panel assembled and ready for further use:

As we see in practice, there are many specific nuances in repairing the LED backlight of an LG TV matrix, and without knowing them, it is impossible to achieve a positive result.

Final works

When the LG TV system has been completely repaired, before final assembly, we connect the voltage to the strips and check the glow of all LEDs. If everything is fine, then we assemble the TV, performing all operations sequentially and with caution, as during dismantling.

After finishing, it is better not to turn the backlight brightness to maximum, but to limit it to 75% - in this mode, the LEDs operate in normal mode and, according to experts, will last much longer.

We install the TV in its original place, turn it on and enjoy the quality: if there are no extraneous spots of light or dark color anywhere on the screen, it means that the repair was carried out correctly, in compliance with all recommendations. And you can get the most out of your TV by learning how to properly

The most reliable LG TVs of 2018

TV LG 22LH450V

TV LG 49UJ651V

TV LG OLED55C8

TV LG 55LJ622V

TV LG 55UK6100
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 CCFL and HCFL fluorescent lamps, which were inferior to plasma TVs in 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 a high-quality image 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. In terms of light characteristics, edge lighting occupies an average position and strongly depends on the build quality and the element base used. 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 involves using RGB LEDs instead of white ones. With their help, it is possible to adjust not only the brightness, but also set any color from the entire visible spectrum. Due to the high switching speed, the 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. It will not be possible to replace a burnt-out element with a similar one on your own, since it is almost impossible to find an exact copy with the same lens. 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 lies in 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. But users of PCs and laptops with LED backlight are 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 hand, long-term work with documents at reduced brightness 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 will continue to advertise so-called LED TV. 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.

Read also

Unlike the earliest models LCD TVs , in which CCFL was used backlight (cold cathode lamps) in modern television receivers special LEDs .
Important! In this case, the screen backlight is organized in such a way that LED products take up very little space and provide the effect required to obtain a high-quality image.
Besides, LED -elements are more reliable and do not overheat like light bulbs due to prolonged glow.
Parameters of LED elements
For screen backlights Standard LED elements are used, designed for the appropriate voltages and currents. In addition, it is important to pay attention to the power of the installed element, which for different types of TVs and monitors can vary within significant limits. From this parameter The luminous flux generated by a specific model of LED element and the operating efficiency of the entire backlight system depend.
When studying the parameters, special attention is paid to the dimensions of the mounting area for the housing of a particular LED, which characterizes its geometric parameters (standard size).
Please note: Of some interest is the cost of the LED product, which is a determining factor for a number of users when assessing the possibility of independently repairing a monitor or TV.
In addition to the above differences, LED elements for arranging lighting for LCD displays can be classified according to the following characteristics:
- Screen glow color (solid white or RGB).
- Uniformity of luminescence.
- Location within the matrix (lateral or central).
Correctly designed color backlight expands the possibilities for fine-tuning the entire spectrum of screen light, and also allows you to enhance the contrast and depth of black in the television image (picture).
Let's consider all these parameters using the example of specific samples of LEDs used for LED backlighting.
Product specific characteristics
Among the most common types of LED products, the samples below are most often used for illumination purposes.
For LG monitor or TV models:
6-volt LEDs with standard sizes 7030 and a power of one watt in various colors;
- everything is the same, but only the power of the LEDs is 2 Watts, and the standard size is 3535;
Additional information: These elements are available in two versions of different polarities (either the anode or the cathode are located on the larger diameter area).
— 3-volt products 0.5 Watt with a standard size of 7020 and a different set of colors;
- the same, but standard size 3528 and a plus on a larger diameter pad (with the same set of colors).
The choice of one or another type of LED product depends on the specific model of the television receiver or monitor in need of repair.

For models of monitors and television receivers of the Samsung brand, as a rule, the following types of LED products with a different set of color shades are used:
-3-volt LEDs per watt with standard size 3537;
- the same thing, but with a characteristic size of 7032;
- and, finally, half-watt products with standard size 5630.

LED backlight for LCD TV panels. What is LED backlighting? Backlight types

Preface

The main causes of failures of LED TV backlights.

Where is the best place to buy LEDs for repairs?

Hi all!

Sometimes, during renovation LCD backlight , difficulties arise in acquiring the necessary luminescent (CCFL ) lamps . In such cases, you can convert the lamp backlight to LED. Such a conversion is not so difficult, and there are no special problems with spare parts.

In this article I offer you the principle of such a reconstruction in the form of some instructions.

Replacement steps LCD backlight to LED:

2. Disconnect the pencil cases from lamps from the matrix or the lamps themselves, if they are installed without canisters.

3. Disconnect old lamps and recycle them. With elements CCFL You also need to be extremely careful, because they contain mercury.

6. Now you need to connect the backlight to the power board of the monitor or TV. To do this, you need to find jumpers marked “12 V” and solder the backlight wires there, observing the polarity accordingly. Reassemble the monitor in reverse order and enjoy your invention.

Backlight in this case it will work when the device is connected to the network.

To control the backlight and bring it into normal mode, you will have to work hard. The wires leading to the LEDs must be powered in such a way that it is possible to turn on the backlight when you press the on/off buttons and adjust its brightness. There are 2 options for this:

1.We independently create a power supply circuit and adjust the backlight brightness:

On the power supply chip of a monitor or TV, we look for a plastic box (connector) with wires coming out of it, where each socket is labeled on the board.

We still have wires from the backlight with a plus, we bring them to the +12V power supply on the microcircuit and solder them.

Now we install the backlight in its rightful place and assemble the monitor in reverse order. Don’t forget to be careful and careful when handling the matrix and filters so that dust does not get in and the cables are not damaged. That's it, you can use it.

The second way, more expensive but convenient, is to buy a ready-made LED backlight with your own inverter :

Again, pay attention to the plastic connector and the DIM pin (brightness) and the on/of pin (it’s better to use the pinout).

Using a multimeter, we determine the places on the control unit of old lamps from which the signal for brightness and on/of comes.

Now solder the wires to the found places inverter new LED backlight .

Also, it is better to unsolder the jumpers from the inverter power supply of the old lamps so that the backlight can be regulated by the new inverter.

Disassembling the product

Troubleshooting

Replacing LEDs

Final works

The most reliable LG TVs of 2018

A little theory

LED Backlight Types

Edge

Direct

About health disadvantages

Unlike the earliest models LCD TVs , in which CCFL was used backlight (cold cathode lamps) in modern television receivers special LEDs .

Important! In this case, the screen backlight is organized in such a way that LED products take up very little space and provide the effect required to obtain a high-quality image.

Besides, LED -elements are more reliable and do not overheat like light bulbs due to prolonged glow.

Parameters of LED elements

When studying the parameters, special attention is paid to the dimensions of the mounting area for the housing of a particular LED, which characterizes its geometric parameters (standard size).

Please note: Of some interest is the cost of the LED product, which is a determining factor for a number of users when assessing the possibility of independently repairing a monitor or TV.

In addition to the above differences, LED elements for arranging lighting for LCD displays can be classified according to the following characteristics:

Screen glow color (solid white or RGB).

Uniformity of luminescence.

Location within the matrix (lateral or central).

Correctly designed color backlight expands the possibilities for fine-tuning the entire spectrum of screen light, and also allows you to enhance the contrast and depth of black in the television image (picture).

Let's consider all these parameters using the example of specific samples of LEDs used for LED backlighting.

Product specific characteristics

Among the most common types of LED products, the samples below are most often used for illumination purposes.

For LG monitor or TV models:

6-volt LEDs with standard sizes 7030 and a power of one watt in various colors;

- everything is the same, but only the power of the LEDs is 2 Watts, and the standard size is 3535;

Additional information: These elements are available in two versions of different polarities (either the anode or the cathode are located on the larger diameter area).

— 3-volt products 0.5 Watt with a standard size of 7020 and a different set of colors;

- the same, but standard size 3528 and a plus on a larger diameter pad (with the same set of colors).

The choice of one or another type of LED product depends on the specific model of the television receiver or monitor in need of repair.

For models of monitors and television receivers of the Samsung brand, as a rule, the following types of LED products with a different set of color shades are used:

-3-volt LEDs per watt with standard size 3537;

- the same thing, but with a characteristic size of 7032;

- and, finally, half-watt products with standard size 5630.