plasma display report 2

8/8/2019 Plasma Display Report 2

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CHAPTER 1

INTRODUCTION

1.1 Introduction

A Plasma Display Panel (PDP) is a type of flat panel display common to large TV displays.

They are called "plasma" displays because the pixels rely on plasma cells. PDPs are an emissive

display which means that the panel itself is the light source. Plasma display is also called as “gas

discharge display” because it uses tiny cells lined with phosphor that are full of inert ionized gas

(typically a mix of xenon and neon). Plasma displays were initially monochrome, typically

orange, but color displays have become very popular and are used for home theater and computer

monitors as well as digital signs.

1.2 Display Devices

A display device is an output device for visual presentation of information. There are 3 types of

display devices. They are:

1. Analog display devices

Example: Oscilloscope tubes, TV CRTs

2. Digital display devices

Example: LED (including OLED) displays, VF (vacuum fluorescent) displays, LCD

(liquid crystal) displays, PDPs (plasma display panels)

3. Others

Example: Electronic paper, Laser TV

1.3 History

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The science behind plasma display has been around since 1960, and the first plasma prototype

appeared back in 1964. The very first prototype for a plasma display monitor was invented in

July 1964 at the University of Illinois by professors Donald Bitzer and Gene Slottow, and then

graduate student Robert Willson. By July of 1964, the team had built the first plasma display

panel with one single cell. Today's plasma televisions use millions of cells. First commercially

available color displays appeared in the late 1990’s. Mass production of these displays started in

1996.

1.4 Basics of Plasma

In plasma display, the "plasma" is basically a substance similar to gas in which a certain portion

of the particles are ionized. We can explain about plasma has a gas containing a large number of

electrically charged particles, both negatively-charged electrons and positively-charged atoms,

called ions Plasma is called as hot ionized gas. It is also called as fourth state of matter.

In plasma with an electrical current running through it, negatively charged particles are

rushing towards the positively charged area of the plasma, and positively charged particles are

rushing towards the negatively charged area. In this rush, particles are constantly bumping into

each other. These collisions excite the gas atoms in the plasma, causing

release photons of energy. The Fig 1.1 explains how the plasma releases the photons.

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Fig. 1.1: Plasma Principle [1]

The common forms of plasma are

i. Artificially produced plasma,

ii. Terrestrial plasmaiii. Space and Astrophysical plasma.

The plasma used in display panel is artificially produced.

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CHAPTER 2

WORKING OF PDP

2.1 Basic Principle of PDP

Fig 2.1: Basic diagram of plasma display working [2]

The basic idea behind the operation of plasma displays is fairly simple. A rare gas (argon) is

sealed inside a tube. At each end of the tube are electrodes to which high-voltage electricity is

applied. The rare gas is electrically neutral, but the excitation by the current transforms it into

plasma, a gas made up of both free electrons and positive ions. Due to the difference in potential

of several hundred volts, the electrons flow toward the positive electrode, while the positive ionsare attracted to the tube's negative terminal. These movements produce impacts between atoms.

When each atom is impacted, it gains energy and its electrons move to a higher-energy orbit.

When they return to their initial orbit, they give off a photon: a "quantum" of light

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The light that's given off is the result of the movement of the plasma under the effect of a

strong electrical field. But applying a continuous difference of potential to the tube's terminals is

not enough. The plasma must be kept in continual movement in order for it to emit light, and so

an alternating current is applied to the terminals. This voltage causes the gas ions to migrate from

one terminal to the other, back and forth. But the light emitted by the plasma isn't visible,

it's ultraviolet, and UV is invisible to humans, so it has to be changed into visible form. To do

this, the walls of the tube are coated with a UV-sensitive powder that emits white light. This

powder, often called phosphor, is a scintillator: a material that converts one form of radiation to

another. . The fig 2.1 shows the UV rays emission and also the scintillator that that converts UV

to visible light

2.2 Composition of PDP

The xenon and neon gas in a plasma television is contained in thousands of tiny cell positioned

between two plates of glass. Long electrodes are also sandwiched between the glass plates, on

both sides of the cells. The address electrodes sit behind the cells, along the rear glass plate. The

transparent display electrodes, which are surrounded by an insulating dielectric material and

covered by a magnesium oxide protective layer, are mounted above the cell, along the front glass

plate.

Both sets of electrodes extend across the entire screen. The display electrodes are

arranged in horizontal rows along the screen and the address electrodes are arranged in vertical

columns. The vertical and horizontal electrodes form a grid. Fig 2.2 shows the inner composition

of PDP.

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Fig 2.2: Composition of PDP [3]

The phosphors in a plasma display gives off colored light when they are excited.

Every pixel is made up of three separate subpixel cells, each with different colored phosphors.

One subpixel has a red light phosphor, one subpixel has a green light phosphor and one subpixel

has a blue light phosphor. These colors blend together to create the overall color of the pixel.

By varying the pulses of current flowing through the different cells, the control systemcan increase or decrease the intensity of each subpixel color to create hundreds of different

combinations of red, green and blue.

2.3 Working of PDP

A PDP creates light emission by selective application of high voltage pulses to electrodes

enclosed in the panel. The electrodes in the face plate are made of transparent material and

consist of scan and sustain electrodes. These electrodes determine which specific pixels or

groups of pixels to “turn on” and for what duration they are to be illuminated. Metal electrodes

on the back plate are known as data electrodes. In this way the source signal determines the

parameters of the image that is to be “drawn” on the screen.

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There are five steps in the process by which PDP produces an image.

1. Initial status

2. Data write discharge

3. Data written status

4. Data sustain discharge

5. Data erase discharge

1. Initial status: In this step, all cells are unlit and initially the screen is black. The Fig

2.3(a) shows the initial setup of the panel.

Fig 2.3(a): Initial status [4]

2. Data write status: When the high voltage is applied between scan electrode and data

electrode a discharge occurs. The discharge occurs only in the cell selected by scan and

data electrode. The Fig 2.3(b) shows the discharge created by high voltage pulse.

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Fig 2.3(b): Data write status [4]

3. Data written status: After the discharge the charges remain on the dielectric layer in the

selected cells chosen by the scan and data electrode. The Fig 2.3(c) shows that the after

the discharge the cells are on the dielectric layer.

Fig 2.3(c): Data written status [4]

4. Data sustain discharge - By applying the sustaining high voltage between sustain

electrode and scan electrode an electric field is created. The electric field created by this

sustain high voltage does not exceed the threshold required to create a gas discharge but

the additional electric field made by the wall charge causes gas to discharge. By this

method only selected cells are lit. After the discharge is finished reverse polarity wall

charge will remain only on the dielectric layer of the selected cells. Fig 2.3(d) shows the

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discharge created by wall charges. When reverse polarity high sustain voltage is applied

continuously for selected cells, these cells continue to discharge and excite the phosphor

and emit light.

Fig 2.3(d): Data sustain discharge [4]

5. Data erase discharge – When voltage lower than the sustain high voltage is applied

between the sustain electrode and the data electrode small discharges are created in the

selected cells. These small discharges absorb the wall charge into the cell and the wall

charge is erased. Fig 2.3 (e) shows the wall charges absorbed by small discharges.

Fig 2.3(e): Data erase discharge [4]

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By repeating steps 2 through 6 the color PDP can create an image according to the input

signals which are led to the driver circuits and these driver circuits instruct the sustain, scan and

data electrodes .

CHAPTER 3

PDP CHARACTERISTICS

3.1 Types of PDP

Plasma Display Panel is divided into two types

They are

i. DC type

ii. AC type

3.1.1 DC Type PDP

In the DC type PDP, electrodes are exposed directly to the discharge gas so that a current

directly flows between electrodes in order to form the plasma. Therefo

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advantageous that the structure is relatively simple. The disadvantage is that the external

resistor has to be placed to limit the current .

3.1.2 AC Type PDP

In the AC type PDP, the electrodes are covered with the dielectric substances so that the

electrodes are not exposed directly to the discharge gas in order to flow a displacement

current. In the AC type PDP, the high voltage has to be applied continuously and

alternately between the sustain electrodes (X electrode and Y electrode) in the discharge

cell during the operation of the PDP. Therefore, the dielectric substances are spread over

the sustain electrodes so that a panel capacitor exists between X electrode and Y

electrode.

The AC type PDP has longer life span, compared with the DC type PDP, because

the electrodes of the AC type PDP can be protected from an ion impact by covering the

electrodes with the dielectric substances to limit the current naturally.

3.2 Characteristics of PDP

• Very strong nonlinear characteristic

Despite voltage supply between electrodes, gas discharge does not occur if voltage

supplied is below the discharge starting voltage, which is a very strong nonlinear

characteristic. Thus, in addressing a large size panel of over 1000 pixels per a line, line

addressing method can have optional discharge and so in addressing a panel of

1000*1000 discharge cell it does not require 100 million lines but only 2000 addressing

circuits.

• Memory Function

PDP determines the next state by the previous conditions, which is called Memory

function of PDP. In case of AC type, by a wall electric charge formed on a dielectric,

memory addressing is possible. In case of DC type, memory addressing is possible by

pulse memory method. Memory function is imperative in addressing large size display. In

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such case of addressing by this kind of memory method, super large panel enable to

express the image of best quality without decrease of brightness.

• Long life span

AC type prolongs life span, using preventive layer such as MgO of preferable sputtering

characteristic whereas DC type gets long life span by employing current control

resistance, seals a little amount of Hg or increase gas pressure, which leads to ion shock,

and, it reduces sputtering damage of electrode substance. In the perspective of life span,

AC type lasts longer. Currently, products of AC type insures to last 20,000 hours. In

principle, it is possible to last over 10,000 hours.

• Optical Viewing Angle

PDP has a wide viewing angle as self emissive display. Both AC type and DC type has

over 160° wide viewing angle in every direction, which is the same level of CRT.

• Easier Full Colorizing

Color realization of PDP exploits the photoluminescence mechanism that ultraviolet rays

generated from discharge stimulate phosphor layer and radiates visible rays. Thus, very

excellent full color realization can be possible through betterment of brightness and

achievement of high contrast by advancement of technology afterward.

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CHAPTER 4

COMPARISION WITH OTHER DISPLAY

Comparison between PDP and other displays for a 40 inch display is shown in Table 4.1.

Large

Size

Space

Factor

View

Angle

Full

Color

Resolution Brightness Contrast Power

PDP 1 1 1 1 2 2 2 3

CRT 3 4 1 1 2 1 1 3

LCD 4 1 2 1 1 2 2 1

PROJECTOR 1 4 3 1 2 3 3 3

Table No.4.1: Comparison between PDP and other displays for a 40 inch display

(1: Excellent 2: Good 3: Acceptable 4: Poor)

When we compare PDP with other displays, for larger size PDP is the suited.

For less Space requirement also PDP and also LCD can be used.

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View Angle is best for PDP and CRT also.

Only the power consumption of PDP is bit high when compared with LCD.

Overall when we analyze for larger size displays PDP is the best display.

CHAPTER 5

ADVANTAGES AND DISADVANTAGES OF PDP

5.1 Advantages of PDP

1. Slim and Space saving design

Plasma displays are very thin, averaging between 3” and 6” thick.

2. Wide Viewing Angle

Viewing angle is almost a full 180° with virtually no loss of readability due to the

emissive nature of the plasma panel. In other words, the panel itself is the light source .

3. Higher resolution

Plasma display devices have higher resolution than conventional TV sets, and are capable

of displaying full HDTV and DTV signals as well as XGA, SVGA and VGA signals

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4. Perfectly flat screen

Plasma display monitors have screens that are perfectly flat.

5. Uniform screen brightness

Plasma displays illuminate all pixels evenly across the screen.

6. Immunity from magnetic fields

Because plasma displays do not use electron beams, as conventional CRT displays do,

they are immune to the effects of magnetic fields.

5.2 Disadvantages of PDP1. Plasma pixels are prone to burn-in, a phenomenon also found in CRT screens. Burn-in

occurs when the same image is projected too long and becomes permanently imprinted

on the phosphor this problem arises in some business application screens.

2. Plasma televisions are restricted in size to at least 32-inches diagonal in order to achieve

competitive resolutions.

3.Since a plasma pixel needs an electrical discharge to emit light, a pixel is either lit or unlit, but has no intermediate state, so controlling brightness is a problem.

4. The flickering can be a problem if viewed from too close to the panel. So, the image on a

plasma display is bigger, but you have to be that much farther away from it.

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CONCLUSION

Plasma Display Panels are gaining more and more importance in the HDTV area. Research is

being done in improving the life span and efficiency of PDP. In the future, PDP's strengths such

as unique high contrast black expressive, high-speed response capability of animation are going

improve. The areas in which future work should be done are high luminance efficiency, low cost

materials and manufacturing processes. If these areas are improved then the PDPs can have a

great future.

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REFERENCES

[1] http://en.wikipedia.org/wiki/Plasma_display#How_plasma_displays_work

[2] http://www.tomshardware.com/reviews/lcd-plasma,992-4.html

[3] http://gadgetophilia.com/lcd-tv-and-plasma-tv/

[4]NEC Technologies Visual Systems Division, “Technology White Paper Pla

Displays”, 1998

[5] http://www.plasmacoalition.org/plasma_writeups/plasma-display-panels

[6] http://electronics.howstuffworks.com/plasma-display1.htm

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REVIEW

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