CONTENT Introduction

History

Working Operation

Block Diagaram

Types

Cold Cathode Fluorescent Backlights (CCFL)

LED

Specification

Application

Advantage & Disadvantage

References

INTRODUCTION

The LED TV is a more advanced version of the LCD

TV. While both types of TV on LCD technology and

have flat-panel designs.

"LED TVs are slimmer, brighter, and more detailed

than your traditional LCD TV." LED TVs function by

illuminating LCD panels with LED backlighting.

However, not all LED TVs utilize the same type of

LED backlighting.

HISTORY

From the early 1900s, scientists have been discovering ways to generate light from various materials. In 1907, Henry Joseph Round discovered that light could be generated from a sample of Silicon Carbide (SiC). For the next 50 years, scientists continued to discover the light emitting properties that exist with some compounds. In the 1950s, studies around the properties of Gallium Arsenide (GaAs) paved the way for the first official LED discoveries that soon followed.

WORKING PRINCIPLE

A semiconductor with extra holes is called P-type

material, since it effectively has extra positively-charged

particles. Electrons can jump from hole to hole, moving

from a negatively-charged area to a positively-charged

area. As a result, the holes themselves appear to move

from a positively-charged area to a negatively-charged

area.

A diode comprises a section of N-type material bonded

to a section of P-type material, with electrodes on each

end. This arrangement conducts electricity in only one

direction.

When no voltage is applied to the diode, electrons from the N-type material fill holes from the P-type material along the junction between the layers, forming a depletion zone. In a depletion zone, the semiconductor material is returned to its original insulating state -- all of the holes are filled, so there are no free electrons or empty spaces for electrons, and charge can't flow.

At the junction, free electrons from the N-type material fill holes from the P-type material. This creates an insulating layer in the middle of the diode called the depletion zone.

BLOCK DIAGRAM

TYPES

A LCD screen is composed of 2 parts, the actual liquid

crystal display and a light source at the back of the

screen (called backlight). A light diffuser is placed

between the backlight and the LCD screen to uniform the

source of light equally across the screen.

LCD stands for “liquid crystal display” and technically,

both LED and LCD TVs are liquid crystal displays.

The basic technology is the same in that both

television types have two layers of polarized

glass through which the liquid crystals both block

and pass light.

So really, LED TVs are a subset of LCD TVs.

There are 2 main types of backlights used in LCD

screens.

1. CCFL

2. LED

CCFL

CCFL

LCDs with CCFL backlight are on their way

out of the market. Manufacturers are now only

producing them for their lower end and

smaller models. They are getting replaced by

LED TVs. They have the same screen but have

LED lights instead of a CCFL tube for the

backlight

LED, which stands for “light emitting diodes,”

differs from general LCD TVs in that LCDs

use fluorescent lights while LEDs use those

light emitting diodes.

Also, the placement of the lights on an LED

TV can different.

The fluorescent lights in an LCD TV are

always behind the screen.

But, On an LED TV, the light emitting diodes

can be placed either behind the screen or

around its edges.

The difference in lights and in lighting placement

has generally meant that LED TVs can be thinner

than LCDs, although this is starting to change.

It has also meant that LED TVs run with greater

energy efficiency and can provide a clearer, better

picture than the general LCD TVs.

Because of difference in lights and lightning

placement there are two types

EDGE LIT

FULL ARRAY LIT

EDGE LIT

This is the most common method for LED

TVs.

EDGE LIT

In an edge lit LED screen, the LEDs are placed at

the peripheral of the screen.

Depending on the television, it can be all around

the screen or only on the sides or the bottom.

This allows the screen to be very thin. However,

it can cause some spots on the screen to be

brighter than others, like the edges.

FULL ARRAY

FULL ARRAY

This method is considered the best LED

backlight type, but can only be found on a very

limited number of models.

In a full array LED screen, the LEDs are

distributed evenly behind the entire screen.

This produces a more uniform backlight and it

provides a more effective use of local

dimming, where it can change the luminosity

of only a specific part of the screen.

SPECIFICTION

Cost : As per size of TV(almost 20k -70k)

Size : available in 32”,42”,…….

As per the market survey LG, SAMSUNG,

SONY,TOSHIBA,PANASONIC are making

LED TV.

APPLICATIONS

Smartphone

Tablet Pc

Ebook

Ultrabook/Notebook

Video Camera

Media Player

Portable Game

GPS

Automotive

LED TV

Lighting

Smart Metering

ADVANTAGES

Power Savings:

LED backlit TVs are more power efficient than traditional LCD TVs. Although regular LCDs are relatively efficient, LED cells simply produce more light per watt than fluorescents. This can result in a power savings of approximately 40 percent.

Better Contrast:

Some LED backlit TVs are capable of generating better contrast through the use of local dimming. Local dimming is when LEDs behind dark parts of the picture are either dimmed or left off. Doing this can increase the appearance of contrast in the image.

More Accurate Color:

LED backlit TVs can offer richer color than LED panels. This can be accomplished through slightly modifying the color of the white light emitted by the LEDs to compensate for the LCD's shortcomings. A more advanced solution comes in some Sony Bravia models, which use a multi-colored backlight to reinforce the image on screen.

Smaller Size:

Because LEDs are smaller than CCFL tubes, LED TVs can be thinner than traditional LCD TVs. In addition to this, TVs that are edge lit place their LED backlights on the side, making it possible for them to be even thinner than regular LCDs.

DISADVANTAGE

Water - Water can easily damage LEDs.

Cost - cost of its is very high.

INSTRUMENTATION & CONTROL

1ST SEM

CREATED BY:- ENROLLMENT NO.

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