GANDHINAGAR INSTITUTE OF TECHNOLOGY Active Learning Assignment Sub:- Audio Video Systems Topic:- LED TV (Light Emitting Diode Television) Branch :- Electronics & Communication

Group Members:- Faculty-In-charge Prof. Gunjan Jani Arshiya Maniar 130120111014 Zulin Patel 130120111021 Riya Simon 130120111024 Faculty-In-charge Prof. Gunjan Jani

Contents:- History of LED TV Need for LED TV’s What are LED TV’s Working of LED TV Types of LED TV’s LED V/s LCD LED V/s Plasma Advantages of LED TV Future aspects for LED TV

LED TV (Light Emitting Diode Television) The television has gone through many changes since its introduction in 1925. New televisions with improved technologies have evolved, and one of those evolutions was the LED TV. A light emitting diode (LED) television offers advantages over other high definition televisions (HDTVs) that make it worth considering for many reasons. To begin considering buying an LED TV, a person really needs to know all the ins and outs of the television and the technology involved that makes it a good choice as compared to other options on the market. This guide will help the buyer understand the LED television by looking at the history of television and how it produced the LED technology available in TVs today.

History of LED TV In 1970s the first active-matrix crystal display panel was made and the first real LED flat panel television screen was created. The world’s largest LED TV of over 1500 feet long and 90 feet high was displayed in 1995, and in 1996 the first public digital high definition television signal was broadcast in the U.S. In 2008, and the following year the world’s largest LED high definition TV was created and measured 160 feet wide by 72 feet tall. Later, in 2010 Samsung released the world’s first 3D LED HDTV. Liquid crystal display (LCD) TVs come to life when light from behind the screen is shone through a matrix of tiny, coloured liquid crystal cells. Signals control each cell, letting varying amounts of color through to build up the picture.

Need for LED TV’s CCFL-style LCD televisions and Plasma televisions use more energy than LED lights. For this reason, LEDs are offered as the “Eco-conscious” alternative to Plasma and traditional LCD. LEDs are almost free of harmful chemicals like mercury. Slimmer, more power efficient and having a greater optical range than the fluorescents. LED TVs produce deeper blacks and more saturated color. Sony was the first to sell an LED TV in 2005. What’s wrong with existing LCD TVs? Up until now, LCDs used fluorescent tubes to light the screen. As a result, LCDs have trouble creating deep blacks. That’s because fluorescent tubes are always on, and some light leaks through to the front of the display even when a part of the image is supposed to be black. A lack of deep blacks reduces the perceived sharpness of the set’s image. Also, fluorescents lack a wide range of colors; hence, color saturation is limited. CCFL-style LCD televisions and Plasma televisions use more energy than LED lights, which are extremely energy efficient producers of extraordinarily bright light. While LCDs are far thinner and lighter than massive rear-projection sets, they still use cold cathode fluorescent tubes to project a white light onto the pixels that make up the screen. Those add weight and thickness to the television set. LEDs solve both problems. A neon bulb is the simplest gas discharge display. Two electrodes are scaled in a glass bulb filled with a mixture of neon and argon gas. When high enough voltage is applied (typically 100 to 200 V), an electrical discharge begins in the gas. Free electrons acquire high kinetic energies from the electric field. When they collide with gas atoms they transfer this energy to the atoms, thereby exciting them into energy levels above the ground state. The atoms may then lose energy radiatively and return to the ground state. Then the gas emits orange-red light. The ionised gas is called plasma and gas displays are therefore often called plasma displays.

What are LED TV’s?? LED TV is a type of LCD television that uses light-emitting diodes (LEDs) to backlight the display instead of the cold cathode fluorescent lights (CCFLs) used in standard LCD televisions. LED TVs are more formally known as LED-backlight LCD television. They are large screens made up of thousands of extremely bright LED lights. Usually LED displays radiate red, green and blue light. They have a wide operating temperature range, are inexpensive, easily interfaced to digital logic, easily multiplexed, do not require high voltages and have fast response time. The viewing angle is good because it can be viewed from any of the directions like front, side and rear. LED is an acronym for Light Emitting Diode Instead of a filament they use a semiconductor diode which emits narrow-spectrum light. Depending on the composition & condition of the semiconducting material used (Silicone, germanium), they come in either Infrared for sensing heat, Visible for every day use, or Near-Ultraviolet for spotting stains at a crime-scene. An LED consists of a chip of semiconducting material that has been “doped” with impurities in order to create a p-n junction. A p-n junction is basically a junction between an anode and a cathode. Current flows easily from the p-side to the n-side, but never in the reverse order. The wavelength and color of the LED depends on the band-gap energy of the materials forming the p-n junction.

How LED TV works?? To create colors, small filters in red, green, and blue are placed over the top pane glass. Each grouping of the three colors is called a pixel. It is the pixels that when combined create images on the screen. LCDs cannot create light on their own. They need a light source to shine through the back of the glass, and in some cases along the edges of the screen. Older LCDs were lit using fluorescent lamps. Now, many LCD televisions are lit by LEDs. An LED also lasts much longer than most other lighting technologies. LCDs are usually transparent, but when current is applied, the light is bent and only some light will pass through the top layer of glass. In some instances, no light passes through. This is how different shade of color are produced on a screen. To create colors, small filters in red, green, and blue are placed over the top pane glass. Each grouping of the three colors is called a pixel. It is the pixels that when combined create images on the screen. LCDs cannot create light on their own. They need a light source to shine through the back of the glass, and in some cases along the edges of the screen. Older LCDs were lit using fluorescent lamps. Now, many LCD televisions are lit by LEDs. Faceplate picture elements (pixels) are formed by depositing and patterning a black matrix, standard red, green, and blue TV phosphors and a thin aluminum layer to reflect colored light forward to the viewer.

LED LED

Types of LED TV There are two main configurations of LED technologies. Edge-lit LED:- In which white LEDs are situated around all the four edges of the screen and a diffusion panel employed to illuminate the display evenly. Edge-lit LED displays can be very thin. Local dimming backlighting:- LEDs light are positioned behind the panel and these banks can be controlled to lower the amount of back lighting in dark areas of the screen and raise it in bright areas for higher contrast and better blacks. Local dimming backlighting or full array backlighting displays are thicker TV panels. Edge lighting Edge lighting is pretty much as described. In this method, a series of LED backlights are positioned along the outside edges of the screen. From there, the light is dispersed across the screen, which means the LED/LCD TV can be made very thin. And while the results may be better than CCFL screens, the black levels in edge lighting are not as deep and, if you look closely, the edge area of the screen tends to be brighter than the middle viewing area. Full-array backlighting To take full advantage of LED lighting, some manufacturers use full-array LED backlighting, where many rows of LEDs are placed behind the entire surface of the screen. Although this makes for a thicker TV panel, the LEDs provide more even, brighter colors and greater contrast. A measurable benefit of full-array lighting can be seen when "local dimming" is utilized, meaning that each LED (or more common, a selected "zone" of LEDs) can be turned on and off independently within the screen, thus providing greater control of the brightness and darkness for each of those areas. Greater contrast levels are achieved by diminishing the effects of light from brightly lit neighboring areas seeping into blackened areas of the screen, which is one of the downsides of LCD screens.

LED V/s LCD LED LCD LED TV’s use an array of smaller, more efficient light emitting diodes (LED’s) to illuminate the screen, which gives them a few advantages. Ordinary LCD TV’s use cold cathode fluorescent lamps (CCFL’s) to provide backlighting. Local dimming LED back light dims the back light in areas where the screen should be dark. LCD panels create dark tones by blocking the backlight passing through the panel. RGB colored lights in LED TVs have more advantage in displaying realistic color. Color accuracy is good. LED’s are considerably smaller than CCFL tubes, which means LED TV’s are much thinner. They are thicker than LED TV. LED’s also consume less power in LED TV about 101 watts. Due to CCFL, LCD TV requires more power about 111 watts. LED TVs Produce Vivid Pictures With brighter lighting than a fluorescent lamp, LED lit televisions will give a brighter picture compared to LCD TVs. Even in bright rooms with a lot of daylight, the image will stand out much better. Some LED TVs also have a non-reflective screen which, together with a brighter image, can make for a good choice when choosing a television for rooms where daylight causes glare on the screen. 5. LED TVs Have Great Picture Quality Though brightness and vivid pictures are a must, picture quality is also good in LED TVs. With a higher contrast ratio, LED TVs offer better contrast and color accuracy. An LED TV is backlit with a local dimming and can have improved picture quality when compared with standard LCD televisions or other older models. The LED TV gives the picture quality, picture color, and a sleek look that is similar to that of the plasma screen. Yet it is more energy efficient, saving the consumer money in the long run, thus making the LED TV definitely worth considering.

LED V/s LCD (picture quality) LED TVs provide a better picture for two basic reasons. First, LED TVs work with a color wheel or distinct RGB-colored lights (red, green, blue) to produce more realistic and sharper colors. Second, light emitting diodes can be dimmed. The dimming capability on the back lighting in an LED TV allows the picture to display with a truer black by darkening the lights and blocking more light from passing through the panel. This capability is not present on edge-lit LED TVs; however, edge-lit LED TVs can display a truer white than the fluorescent LED TVs. LED TV LCD TV

Better brighter colors and even greater contrast ratios. A feature called local dimming in LED TV – a selective lighting technique that allows for deeper blacks and better overall picture. CCFL backlighting is that fluorescent tubes must light the entire screen evenly, so designers have no way to vary the backlighting intensity in different parts of the screen.   Better brighter colors and even greater contrast ratios. They deliver good brightness, and average contrast ratios. LED backlighting doesn't change the picture effects viewed from any of this sides. In LCD TV, picture degrades if you're sitting off to the side or the TV is placed too high or low, based on your eye level. Refresh rate is too high and pixel response time is low. Refresh rate is average and response time is not good as LED TV. Cost is higher because of improved features in LED TV. LED’s also consume less power than their CCFL counterparts, but the most important difference between the two is a feature called local dimming – a selective lighting technique that allows for deeper blacks and better overall picture.  The problem with CCFL backlighting is that fluorescent tubes must light the entire screen evenly, so designers have no way to vary the backlighting intensity in different parts of the screen. Even if you want to show a single white pixel on an all-black screen, the light in the back needs to be blazing away at full brightness. LED TV’s offer a solution to this with local dimming. The idea behind this technique is to control the output of the LEDs so that, rather than be on at full brightness all the time, they can be dimmed or turned off entirely. Much like the old picture flip books that make drawings look like they are moving, videos are made of "frames." Many frames are displayed on the TV screen each second which is referred to as refresh. A refresh rate is faster than a frame rate which means a person can watch the same frame multiple times in one second. The higher the refresh rate or the faster a frame refreshes, the clearer the picture will be. The pixel rate response time is the number of milliseconds that it takes each pixel to respond to a refreshed image. Refresh rate deals with the hardware of the TV, and pixel response time refers to how quickly pixels change color from white to red or green or black. The lower the time, the better the picture quality will be.

LED V/s Plasma LED Plasma Weight Lighter compared to plasma TV. Heavier compared to LED-lit LCD TV. Brightness and color Brighter than plasma or OLED. Not as bright as LED-lit LCD. Thickness LED edge backlit LCD TVs are thinner than CCFL LCD TVs. Often less than 1 inch. Minimum 1.2 inches Power consumption LED-lit LCD TVs consume less power around 70%  compared to plasma. Consumes slightly more power than an LCD TV. Modern plasma displays receive high Energy Star (US) ratings. Life span Around 100,000 hours Around 20, 000 – 60,000 hours Cost $100 (small size and very low end) - $25,000. Cheaper than LED TVs.

Manufacturers All TV manufacturing companies. Panasonic, LG, Samsung Running Temperature Dynamically lit LCD TVs dissipate less heat compared to plasma TVs. LED-lit LCD TVs dissipate less heat than even other LCD TVs. Plasma TVs generally dissipate more heat than LCD TVs. Screen glare Anti-reflectively coated (matte finished) LCD TVs have less glare than glossy LCD TVs. Plasma TVs have more glare than LCD TVs in brightly lit environments due to their thick front glass's internal reflections. Energy Use Less for dynamically backlit LCD TVs, about as much for statically backlit ones. Generally more. Viewing angle The brightness and color on LCD TVs shift noticeably over the screen and depending on viewing angle. Plasma TVs look the same from almost any angle.

Advantages of LED TV’s Sharper picture More energy efficient Uses about 40% less electricity than a standard LCD TVs. LED backlighting system has no delay or warm up time. Much thinner than the traditional LCD or plasma TVs. Easier to mount on walls or hang from ceilings. LED TVs show contrast similar to a plasma TV. Are brighter than an LCD TV. Longer life The LED lighting of the picture results in a sharper picture, more energy efficient using about 40% less electricity than a standard LCD TV, the LED backlighting system has no delay or warm up time, and the LED lit TVs are much thinner than the traditional LCD or plasma TVs. For example one of the Sony LED  TV’s is only 9.9mm thick. Advocates of the LED technology say the LED TVs combine the best of plasma and LCD TVs. LED TVs show contrast similar to a plasma TV and are brighter than an LCD TV. Disadvantages… Cost of LED TV increasing day-by-day. Off-angle viewing is not very good. Are not manufactured in as wide a size range as traditional CCFL LCD TVs.

Future aspects for LED TV OLED TV (Organic Light Emitting Diode) displays make use of a thin organic film deposited on its surface with a simple printing process. They don't require a backlight to function, which allows for much thinner and power-saving displays. OLED TVs almost much thinner than LED TVs. The problems they encounter is where do you stuff all the things like speakers, tuners, storage drives, etc in around 15mm of space. Current OLEDs has limited lifespan compared to other technologies - blue OLEDs, which have a typical working life of roughly 5000 hours. Then there's Laser TV & 3-D TVs in the market from next year. Further more in future we'll also have holographic TV. Current OLEDs has limited lifespan compared to other technologies - particularly the blue OLEDs, which have a typical working life of roughly 5000 hours while, in general, LCD and plasma technologies log in around 60,000 hours, depending on the model.

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