lcd panel backlight free sample

With all the advantages and disadvantages, lcdds are essentially a good choice for those who see the TV starting from 4k smartphone. Nowadays, in addition to the wholesale models, lcdds are essentially a good option for those that don ’ t have the capacity of a device.

We manufacture and stock backlight assemblies for many CMO Chi Mei LCD panels. We produce premium quality replacements to extend the life of your flat panel screen devices.  If you do not see your panel model listed here, please contact us to learn about our cost effective design and manufacturing process.  Simply mail us a sample of the backlight you are looking to replace, and we can recreate and supply you with what you need to meet you needs.

LCD displays don’t emit light by themselves. They need a light source, and LED backlights are now dominating the market. In this article, Orient Display’s Bill Cheung provides a complete overview of LED backlight technology, discussing different types, driver technologies, color deviation, brightness options and more.

LCD (liquid crystal display) has long been the dominant technology in the display world. Certainly, there are some emerging competing display technologies—such as OLED (Organic Light Emitting Diode) [1] and micro-LED—that have the potential to threaten LCD’s position in the market. But both are currently only used for niche and high-end markets.

An LCD display can’t emit light by itself. In order to have an LCD display [2] used in a dim environment, a backlight has to be used as the light source. There are a few different technologies that are able to produce backlight ranging from EL (electroluminescent), CCFL (cold cathode fluorescent lamps) and LED (light emitting diode). However, a breakthrough in blue LED technology by Shuji Nakamura [3] led to LED backlights dominating the market.

One of the greatest benefits of LED backlighting is its long lifetime. Normally, LED lifetime can be measured with half-life when the original brightness decreases by 50%. With different LED chip manufacturing materials, technologies and environment used, the LED life can vary from 20,000 hours to well over 100,000 hours.

LED backlights have low power consumption and produce much less heat than other backlight technologies, which extends the durability and performance of the other display components. Furthermore, this reduces the risk of fire and explosion. LED backlights are also driven with DC (direct current) and low voltage (can be as low as 1.5V), which are good for battery drive and emit no interference to the circuitry. With the development of LED technology, the LED chips become small. So, it is possible to produce very thin backlight (0.5mm thick or thinner).

Although white LED is the most popular color, LED backlight can be made into different single colors, bi-colors and tri-colors [4] (Figure 1) (Figure 2). With RGB LED backlight color mixing, normal 8 color LED backlight can be produced (Figure 3).

LED backlight can be classified as bottom (array) lit and side (edge) lit backlights, and each have their plusses and minuses. The advantages of the bottom lit (array) backlight are that it is uniform and bright. Its disadvantage is high current draw, thickness, heat dissipation and cost. Meanwhile, the advantages of the side lit backlight are its thinness, flexibility in design, low current and lower cost. The main disadvantage of the side lit backlight is its non-uniformity—hot spots can be seen from most of the side lit backlight from certain angle. Figure 4 compares the bottom lit and side (edge) lit backlight LCD types.

Now let’s look at LED backlight structures. An LED backlight can be simplified into layers starting with a LED chip, light guide, diffusor and reflector (Figure 5). This is the lowest cost structure. Except for some very low current efficiency LCD displays—such as utility meters, battery-powered clock, watch, GPS and so on—most LCD displays need backlights to be visible in the dim lighting. Most often the backlight is actually at the back of the LCD. In rare cases, this light can be done as front light. The traditional LCD structure with LED backlight shown in Figure 6.

Direct current driving: This is the simple and low-cost way to drive a LED backlight, however, be mindful of the current limit otherwise the LED life can deteriorate quickly. The solution is simply to add a current limiting resistor in the circuit. Current limitation resistors value calculation formula: R = (V0– Vf)/If.Also be mindful of reverse drive, otherwise, the LED chip can break down easily.

There are a variety of ways to connect a backlight and LCD module electrically. It can be done with wires that are soldered on the LCD or LCD module. It can be connected using pins, which can be soldered onto the LCD or LCD module. A third way is to use a FPC (flexible printed circuit), which can be soldered or plugged in a ZIF (zero insertion force) connector. And finally, there is the connector method. With this method you use connectors which can be plugged into mating connectors.

As the LED is manufactured via the semiconductor process, there are some color deviations that can be a quality control issue. One way to solve the issue is through a process of selection and sorting after manufacturing the LEDs. The LEDs are sorted into different categories or bins. How this sorting is done and what each bin actually contains is defined differently by each LED manufacturer. The backlight manufacturer can choose from which bin they take the LEDs for backlight color hue.

In actual LED backlight production, most customers will accept the LED color for two big categories: white with yellowish (warm) and white with bluish (cold). Of course, the LED brightness will also need to be defined. For general application, most customers will accept a brightness tolerance of 70 percent.

It is extremely hard to estimate the LED backlight lifetime or MTBF (mean time between failures) because there are so many variable factors. However, the most important is the temperature on the LED chip. The factors that can affect the LED chip temperature include: surrounding temperature, humidity, driving current, voltage, backlight design (how many LED chips to be used, how close to each other, heatsink design), backlight manufacturing process (type and thickness of adhesive), quality of the LED chip and so forth.

To test the LED life is also very time consuming, requiring at least 1,000 hours. That’s the reason why no LED manufacturers can guarantee LED backlight life and most backlight manufacturers also are reluctant to provide lifespan data. As for LCD manufacturers, they need to discuss it with the customer to understand the applications and provide suggestions. It is normal that the LCD datasheet lists the typical life time and avoids providing a minimum lifetime. From Figure 10, we can see that over room temperature, the current needs to decrease as the temperature increases. At over 85°C, the LED is not usable.

To estimate LED backlight lifetime, you can use ballpark estimation or theoretical calculation. Let’s first examine the ballpark method. To take white LED as example, the nominal biasing current is 20mA. If we use a safe lifetime estimation, we can estimate using Table 1.

Now let’s use the theoretical calculation approach. As we previously mentioned, LED life is affected by a lot of factors: surrounding temperature, humidity, driving current, voltage, backlight design (how many LED chips to be used, how close to each other, heatsink designed), backlight manufacturing process (type and thickness of adhesive), quality of the LED chip and so on. LED chip manufacturers are not willing to give absolute values of LED chip lifetimes, but there is a theoretical calculation that we can use.

Finally, let’s look at ways to increase LED backlight brightness. There are many ways to increase LED backlight brightness, but all these measures are balanced with performance and cost. Here are some of the methods:

For the LCD module side, using better aperture opening ratio, anti-reflection coating on surface, optical bonding. This results in higher cost. Actually, this measure is not to increase LED backlight brightness directly but to increase to the visibility to users.

Bill Cheung is an engineering lead and marketing manager at Orient Display, an LCD and display technology provider with over two decades of industry experience in delivering cutting edge display solutions. You can browse Orient Display"s knowledge base [7] to learn more about LCDs.

LED LCD backlights are small light strips, or light sources, contained inside a display, TV, or monitor to provide lighting for the screen. All LED TVs are LCD panels with LED backlighting. A common misconception is that LED displays are different from LCD when fundamentally they are the same. LED is better described as a sub-set of LCD devices.

LCD is an acronym for Liquid Crystal Display, which is a type of monitor or screen—and flat-panel technology—that relies on thousands or millions of pixels, arranged in a rectangular grid. When an LCD is turned on, each pixel takes on a red, green, or blue sub-pixel (RGB) that is either enabled or disabled. When the pixels are off, the individual section appears black, and when all of the sub-pixels are on, it appears white. Collectively, the arranged pixels provide the sharp image on the display by being in either an on or off configuration.

The LED backlight illuminates the pixels, from behind, making them appear richer and brighter. Not all LCDs have a backlight, and for those that do, not all of them utilize LED backlighting. Some displays also use CCFL lighting or Cold-Cathode Fluorescent Lamps. Although, it should be noted that CCFL displays are being phased out in favor of LED-backlit panels.

The liquid crystals inside an LCD panel don’t have any illumination on their own and require the light to come from a separate component, which, in this case, is provided by the LED backlighting.

Older display types, such as cathode ray tubes (CRT) produce illumination already and so they do not need an additional light source like LCD devices.

While it can be confusing at first, LED-backlit panels are different from a full LED. LED-backlit panels have LED strips lining the edges of the screen whereas full HD illuminates the entirety of the display often with higher brightness and color accuracy. Full LED panels achieve this thanks to an evenly distributed light source across the rear of the set.

Full LEDs, on the other hand, can achieve true blacks, with even brightness levels because the light spreads across the entire panel accurately. That also means the lights in the full-LED panel can be disabled or turned off individually to create a darker image.

Because both types are fundamentally LCD panels, both LED and LED-backlit displays produce bright and vivid pictures. However, scenes may appear brighter or slightly washed out, depending on how the light source is distributed, such as from edge backlighting versus evenly distributed lighting. If you prefer a more accurate picture, full LED panels are the way to go, but they are more expensive.

Similar to TVs and other displays, an LED-backlit LCD monitor is an LCD panel with LED backlights. What often sets a monitor or computer monitor apart from standard displays is they don’t include a built-in tuner, which is needed to access cable. They often include different video or display ports, such as HDMI, DisplayPort, VGA, and so on. They"re designed to be used as a primary or secondary display for desktop computers, laptops, and beyond.

Monitors are generally full LED panels with a fully distributed light source. This allows them to provide a brighter and sharper image overall, which is ideal for computer-related activities and media.

While all LED TVs are LCD TVs, not all LCD TVs are LED TVs. If a TV is marketed as LCD with no mention of LED, then it probably uses a different type of backlighting such as CCFL.

An LED-backlit LCD is a liquid-crystal display that uses LEDs for backlighting instead of traditional cold cathode fluorescent (CCFL) backlighting.TFT LCD (thin-film-transistor liquid-crystal display) technologies as CCFL-backlit LCDs, but offer a variety of advantages over them.

While not an LED display, a television using such a combination of an LED backlight with an LCD panel is advertised as an LED TV by some manufacturers and suppliers.

The local dimming method of backlighting allows to dynamically control the level of light intensity of specific areas of darkness on the screen, resulting in much higher dynamic-contrast ratios, though at the cost of less detail in small, bright objects on a dark background, such as star fields or shadow details.

A 2016 study by the University of California (Berkeley) suggests that the subjectively perceived visual enhancement with common contrast source material levels off at about 60 LCD local dimming zones.

LED-backlit LCDs are not self-illuminating (unlike pure-LED systems). There are several methods of backlighting an LCD panel using LEDs, including the use of either white or RGB (Red, Green, and Blue) LED arrays behind the panel and edge-LED lighting (which uses white LEDs around the inside frame of the TV and a light-diffusion panel to spread the light evenly behind the LCD panel). Variations in LED backlighting offer different benefits. The first commercial full-array LED-backlit LCD TV was the Sony Qualia 005 (introduced in 2004), which used RGB LED arrays to produce a color gamut about twice that of a conventional CCFL LCD television. This was possible because red, green and blue LEDs have sharp spectral peaks which (combined with the LCD panel filters) result in significantly less bleed-through to adjacent color channels. Unwanted bleed-through channels do not "whiten" the desired color as much, resulting in a larger gamut. RGB LED technology continues to be used on Sony BRAVIA LCD models. LED backlighting using white LEDs produces a broader spectrum source feeding the individual LCD panel filters (similar to CCFL sources), resulting in a more limited display gamut than RGB LEDs at lower cost.

The evolution of energy standards and the increasing public expectations regarding power consumption made it necessary for backlight systems to manage their power. As for other consumer electronics products (e.g., fridges or light bulbs), energy consumption categories are enforced for television sets.

A first dynamic "local dimming" LED backlight was public demonstrated by BrightSide Technologies in 2003,Sony in September 2008 on the 40-inch (1,000 mm) BRAVIA KLV-40ZX1M (known as the ZX1 in Europe). Edge-LED lighting for LCDs allows thinner housing; the Sony BRAVIA KLV-40ZX1M is 1 cm thick, and others are also extremely thin.

LED-backlit LCDs have longer life and better energy efficiency than plasma and CCFL LCD TVs.mercury, an environmental pollutant, in their manufacture. However, other elements (such as gallium and arsenic) are used in the manufacture of the LED emitters; there is debate over whether they are a better long-term solution to the problem of screen disposal.

Quantum dots are photoluminescent; they are useful in displays because they emit light in specific, narrow normal distributions of wavelengths. To generate white light best suited as an LCD backlight, parts of the light of a blue-emitting LED are transformed by quantum dots into small-bandwidth green and red light such that the combined white light allows a nearly ideal color gamut to be generated by the RGB color filters of the LCD panel. In addition, efficiency is improved, as intermediate colors are no longer present and do not have to be filtered out by the color filters of the LCD screen. This can result in a display that more accurately renders colors in the visible spectrum. Companies developing quantum dot solutions for displays include Nanosys, 3M as a licensee of Nanosys, QD Vision of Lexington, Massachusetts, US and Avantama of Switzerland.Consumer Electronics Show 2015.quantum dot displays at CES 2017 and later formed the "QLED Alliance" with Hisense and TCL to market the technology.

Mini LED displays are LED-backlit LCDs with mini-LED–based backlighting supporting over a thousand full array local dimming (FALD) zones, providing deeper blacks and a higher contrast ratio.

LED backlights are often dimmed by applying pulse-width modulation to the supply current, switching the backlight off and on more quickly than the eye can perceive. If the dimming-pulse frequency is too low or the user is sensitive to flicker, this may cause discomfort and eyestrain similar to the flicker of CRT displays at lower refresh rates.

Novitsky, Tom; Abbott, Bill (12 November 2007). "Driving LEDs versus CCFLs for LCD backlighting". EE Times. Archived from the original on 28 November 2010. Retrieved 21 November 2020.

Controlling Power Consumption for Displays With Backlight Dimming; Claire Mantel et al; Journal of Display Technology; Volume: 9, Issue: 12, Dec. 2013; https://ieeexplore.ieee.org/document/6520956

LCD Television Power Draw Trends from 2003 to 2015; B. Urban and K. Roth; Fraunhofer USA Center for Sustainable Energy Systems; Final Report to the Consumer Technology Association; May 2017; http://www.cta.tech/cta/media/policyImages/policyPDFs/Fraunhofer-LCD-TV-Power-Draw-Trends-FINAL.pdf Archived 1 August 2017 at the Wayback Machine

LCD (Liquid Crystal Displays) have two options or display modes.Positive mode (dark characters on a light colored background) and negative mode (lighter colored characters on a darker background).

Positive mode displays have the advantage of their lighter background and no backlights are needed. They normally use transflective or reflective polarizers and have lower power consumption. They can be seen with ambient light.

But under bright ambient light or even under direct sunlight, the displays will be easily washed out. In order to be seen under the bright surrounding light, the backlight brightness has to be increased to over 800 nits. The sunlight readable displays consume much power.

Of course, we can always use LED backlight in the LCD module with fewer LED chips and turn off LED backlight when not use to save power. When can also add transflective polarizer to some negative LCDs to make it sunlight readable, but the contrast will be compromised.

Positive and negative mode concept is not only limited to monochrome LCD displays (LCD panels, character LCDs, graphic LCDs etc.), it also uses for color displays, or even other display technologies.  We will categorize the displays as below,

Character LCD modules (Alphanumeric LCD display modules) with character sets: 8×1 LCD display, 8×2 LCD display, 16×1 LCD display, 16×2 LCD display, 16×4 LCD display, 20×2 LCD display, 20×4 LCD display, 24×2 LCD display, 40×2 LCD display, 40×4 LCD display. COB (Chip on Board) bonded, 4 or 8 bits parallel, SPI, I2C interface

Graphic LCD modules with dot matrix sets 122×32, graphic LCD display, 128×64 graphic LCD display, 192×48 graphic LCD display,192×64 graphic LCD display,240×64 graphic LCD display,240×128 graphic LCD display,240×160 graphic LCD display with different color LED backlights, with COB and COG (Chip on Glass) assembling technologies

Full Color TN and IPS displays with panel sizes: 1.3”IPS display, 1.44” TN display, 1.5” IPS display, 1.77”TN and IPS displays, 2.0” TN and IPS displays, 2.2” IPS display, 2.35” IPS display, 2.4” TN and IPS displays, 2.8” TN and IPS displays, 3.5” TN and IPS displays, 4.3” TN display, 5.0” TN and IPS display, 7.0” TN and IPS display, 10.1” IPS display with medium and high brightness (sunlight readable), with parallel, SPI, RGB, LVDS, MIPI interfaces.

Traditional LCDs use CCFLs, or cold-cathode florescent lamps, as their backlight. While cheap, they"re not as energy efficient as LEDs. More importantly, all contain mercury, and aren"t able to do some of the fancy area-lighting of which some LED backlit models are capable. Because of these issues and the falling prices of LEDs, CCFL backlit LCD TVs will disappear entirely very soon. In 2013

Most LED LCDs on the market today are edge-lit, which means the LEDs are in the sides of the TV, facing in toward the screen. In the image at the top, the LED strips are above and to the side of this exploded-view of an LCD panel. There"s a close-up view here (full article with more images

There are a few models that are have their LEDs arrayed on the back of the TV, facing you. These are less common, though are making a comeback in the form of cheaper, but thicker, mostly low-end LED LCDs. There are a handful of high-end TVs that use full-array LED backlighting in a slightly different way, which we"ll discuss later.

Because the light is brightest nearest the LEDs, it"s common for edge-lit LED LCDs to have poor uniformity. This is especially noticeable on dark scenes, where areas of the screen will appear brighter than others. Corners or edges can have what looks like tiny flashlights shining on the screen. Check out

Each manufacturer has a preferred method for edge-lighting, but some models may feature one type, while other models feature another type. Generally speaking, the fewer LEDs the cheaper the TV is to produce. Fewer LEDs also mean better energy efficiency, but LED LCDs are already so efficient that this is a tiny improvement. Unfortunately, specific details about where a TV"s LEDs are located (beyond "direct" or "edge"), the number of LEDs, and other useful information about the backlighting, are rarely listed on a TV"s spec sheet.

All Sides used to be the most common edge-lighting method. But as the light guides improved, and costs had to come down (to make cheaper LED LCDs), this method became fairly rare.

Nearly all "backlit" LED LCDs use this method. The LEDs are arrayed on the back of the TV, facing you, but there is no processing to dim them individually. They work instead as a uniform backlight, like most CCFL LCDs. The least expensive LED LCDs use this method, as do most of Sharp"s

This is the ultimate LED LCD, offering performance that rivals the better plasmas. Like the "direct-lit" TVs, these have their LEDs behind the screen (the image above for direct-lit works as a visual aid for this type as well). The full local-dimming aspect means the TV is able to dim zones behind the dark areas of the screen in fairly specific areas to make the image really pop, drastically increasing the apparent contrast ratio.

However, they basically don"t exist. The LG LM9600 wasn"t great last year, and LG has yet to announce any full-array local-dimming TVs for 2013. The only other local-dimming LED LCD was the Sony HX950, which was excellent, and is still current. In his review David Katzmaier called

As I mentioned at the top, there"s no easy way to tell, just by looking at a spec sheet, what kind of backlight a TV has. By extension, there"s no way to tell how good its local dimming will be. Bad local dimming can, at worst, just be marketing hyperbole. At best, it does little to improve the picture. Good local dimming, however, can make a punchy image, with lots of apparent depth and realism. Or to put it differently, the best LCDs on the market have the best local dimming, allowing them to rival plasmas on the picture quality front. The better TV reviews, like ahem those here on CNET, will talk about all this, so you"re not duped into paying for a "feature" that"s little more than a check mark on a spec sheet.