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1David Phantana-angkool Chris Rodgers Plasma Display PanelDavid Phantana-angkoolChris Rodgers
2QuestionsFor what size televisions, are plasma display panels generally regarded as superior?What is the efficiency of xenon excitation in RF PDP?
3Definitions CNT-Carbon Nanotubes FPD - Flat Panel Display LCD - Liquid Crystal DisplayRF - Radio FrequencyVHF - Very High FrequencyLuminance - intensity of light per unit areaLuminous efficiency - the ratio of the total luminous flux to the total radiant flux of an emitting source
4Television Marketplace Currently still dominated by cathode ray tubeBeginning to be replaced by flat screen applications for home theater, sales presentations, and staging, rental, and digital signsAdvantages are thin, lightweight design, wide viewing angles and high resolution
5PDP vs. LCD PDPs suffer from burn-in unlike LCDs Research continues into prevention of burn-in by whiting out all potential sources of burn-in before damage occursThis burn-in can be reversed but reduces life of screenPDPs deployed in high ambient light environments, allowing visual impact to be maintained through demanding circumstancesApplications for LCDs typically include images, text, and short video segments which could cause the plasma display to exhibity burn-in rather quickly.For best picture, pdps should be run in full brightness mode, however, running full brightness will reduce the average lifespan to 10,000 hours, meaning that a person who leaves the unit on 24 hours a day will experience problems in 14 months.The AccuShield Phosphor Protection is a new technology that solves the problem of image burn. Like traditional CRT monitors the phosphors can burn into the screen. AccuShield Phospor Protection kicks in "after-hours" to reverse the process. For example, let us say you are in the airline business and need to show flight times, newsfeeds, and sponsors. Fixed objects like logos, and some graphics would eventually leave an image. During the off hours the plasma's timer will activate the AccuShield and reverse the color image and turn down the brightness of your plasma. This results in reversing the image burn on the screen! This works like the screen saver on your PC and dramatically expands the life of your Plasma Display.New technology: whiting out, Sony tiny tubes rather than pixels
8PDP Life Span 4) Screen Life Consumers investing thousands of dollars in a display device face confusing and conflictinginformation about how long a plasma display panel lasts and about the possibility of potentialdamage to the display, compared to other devices. PDPs, like familiar phosphor-based TV sets,gently lose some brightness over the years.In real life, six-hour-a-day use, Plasmavision sets will be half as bright after about 14 years.They’ll lose a bit more brightness in the 14 years after that. When presented with thisinformation, few consumers have any additional concern.Another concern among consumers is pixel life. While a pixel or two on a plasma monitor mightnot light at the time of installation, additional pixel failure after installation is virtually unheard of.The reason is the inert nature of the plasma pixel. There are no switches, gates or circuitsassociated with individual PDP pixels. All of the electronic operations take place in the videoboards, display drivers and other components – not within the plasma display panel itself. Theseelectronics are all either at the edges of the panel or behind the sealed glass. Qualified serviceexperts can replace these components if they fail.LCD pixels, by contrast, are prone to failure over the lifespan of the screen. Dot electrodes,located at each of the one-million-plus sub-pixels, control them. Any of these is prone to failure.
11PDPs vs. LCDs Larger Screen Sizes Available in Mass Production Plasma cannot be produced in screen sizes smaller than 32 inches and plasmas are not generally marketed above 42” because of manufacturing difficulties. Larger LCDs have an extremely poor viewing angle.Home theater experts agree that a theater-like experience is only achieved when the screensize is large enough with respect to the viewing distance from the screen – generally, whenthe screen size takes up 30 degrees of viewing angle. For example, a 42-inch plasmamonitor seems theater-like in size when seen from seven feet away – a comfortable viewingdistance. Larger displays offer even more flexibility for home theater applications.On the other hand, LCD screens have not yet reached these large sizes. At comfortableviewing distances, they look small and do not accurately reproduce a home theaterenvironment.But the real news is the prospect of competition from LCDs of similar size. Until recently, the manufacturing facilities that produce the panels used in LCD displays simply weren't geared for such large-format products, and today the largest LCD TV screens are about 30 inches (measured diagonally).However, new and upcoming generations of LCD plants will be able to efficiently produce 42- and, eventually, 50-inch panels. By the second half of the decade, the cost differential between same-size LCDs and plasma displays probably won't exceed 10 percent, ISuppli/Stanford Resources senior vice president David Mentley told conference attendees.
12World’s Largest PDP Created by Samsung 1920x1080 Resolution 160 Degree Viewing AnglesNow being shownNot likely to be commercially available in the near future
13PDP StructurePlasma display has two parallel sheets of glass enclosing a gas mixture of neon, xenon, and sometimes helium. Electricity is sent through the array of electrodes, excites the gas, and results in a discharge of ultraviolet light. Each pixel contains subpixels of red, green and blue, and when the light strikes a phosphor coating, emitting red, green, and blue visible light.An LCD works entirely differently. An active matrix LCD’s light source is generated by smallfluorescent bulbs. The white light from these bulbs is diffused to create a uniform light source byshining it through a polarizer located in the back of the display, which allows light to go throughin only one direction. Individual LCD cells in the panel are then turned “on” and “off” by applyinga small electric charge to the thin film transistors (TFT), located in each sub-pixel. This chargecauses the liquid crystals to twist, allowing white light to be passed through red, green and bluecolor filters and a front polarizer in front of the LCD cells. The image is formed according towhich crystals twist to let light through or block it.
14PDPs vs. LCDs PDPs glow red, green, and blue LCD sub-pixels approximate colors by subtracting wavelengths from white backgroundAn LCD actually works much differently. The light source is generated by small flourescent bulbs and the white light from these bulbs is diffused to create a uniform light source by shining it through a polarizer on the back of the display. This polarizer allows light to penetrate in only one direction. Individual LCD cells are turned on and off by applying small electric charges to thin film transistors located in each subpixel. This charge causes liquid crystals to move, allowing white light to be passed through red, green, and blue color filters and a front polarizer. An image is formed based on which crystals move and allow light through or remain in place and block light.LCD sub-pixels, on the other hand, use filters to subtract wavelengths from a whitebacklight (white light contains all colors), a process that can only approximate true red,green or blue. As a result, the LCD color process is not as precise or as wide-ranging asthe PDP color process. Also, because of the nature of the polarized filters used in theprocess, the resulting black levels and color range are further limited to a narrow viewingangle. Significant black level and color degradation occurs at a viewing angle only 20degrees off-axis.In the “real world” of home theater, this means flesh tones on Plasmavision monitorslook vibrant and healthy – not robotic, jaundiced or anemic. Golf greens look lush andverdant, and oceans their deepest blue. Viewers can appreciate the superior colorrendition of PDP technology from every angle in their home theater, rather than justhead-on.
15Why LCD? Low power requirements Color performance comparable to CRT, flexibility in selection of the primary colorsLowest cost compared to other FPDsThin and light-weightNo Screen “burn in”Double the life of Plasma Display Panel (50,000 to 75,000 hours compared to 25,000 to 30,000 hours)Altitude does not affect the performance. PDP performance deteriorates above 6,500 feet1. use of CMOS electronic drivers and separation of luminous power from image signal through usage of independent backlight,
16Advancements in PDPsEarly PDPs have luminous efficiency of 0.75 lm/W, 0.4 lm/W, and 0.15 lm/W for green, red, and blue phosphors,Current PDPs have luminance and luminous efficiency of 350 cd/m^2 and 1.2 lm/W and operates at 600WPDP needs to operate at luminous efficiency of 2 to 3 lm/W, a peak luminance of 500 cd/m^2 and a power consumption of 200W to gain market share
17Current Problems with AC PDP Low luminous efficiency 1.5 lm/WPhosphor conversion = 25%Low efficiency for conversion of electrical energy to excitation energyPhosphor conversion = 25%---(ration of visible photon energy to UV photon energy)Boeuf, J.P., et al. "Calculated characteristics of radio-frequency plasma display panel cells including the influence of xenon metastables ." Journal of Applied Physics 92(2002):
18Typical Alternating Current Plasma Display Panel 2% of power is used to produce vacuum ultra violet (VUV)90% of the VUV energy is lost when visible light is emitted from the phosphors58% of electrical energy is lost in heating27% energy loss due to electron ionization and excitation of neonBoeuf, J.P., et al. "Calculated characteristics of radio-frequency plasma display panel cells including the influence of xenon metastables ." Journal of Applied Physics 92(2002):
19Improving PDP Improving Luminance, Luminous, and Power Efficiency Use high frequency excitation ( MHz compare to AC PDP 100kHz)Improving the Image QualitySelf-Erasing DischargeBefore we discussed the improving PDP efficiency using the radio-frequency excitation. I would like to review a quick fact about xenon in Plasma Display Panel.
20Xenon in PDP Only 15% of energy is used to excite xenon 70% of the energy deposit in the Xenon system results in generation of UV photons.Boeuf, J.P., et al. "Calculated characteristics of radio-frequency plasma display panel cells including the influence of xenon metastables ." Journal of Applied Physics 92(2002):
21Why is RF-PDP better?Efficiency for converting RF power into xenon excitation exceeds 80%.Typical ac-PDP conversion ratio is 15%Ion heating in the sheaths is reducedLess of the electrical energy input is dissipated by ions in the sheathMore power is deposited in excitation of the xenon.Low electric fields excitation of xenon is more efficient to neonLuminous efficiency reported to be 5 lm/WLuminance greater than 2000cd/m^2Boeuf, J.P., et al. "Calculated characteristics of radio-frequency plasma display panel cells including the influence of xenon metastables ." Journal of Applied Physics 92 (2002):
22Advantages of RF-PDP Operates at lower voltage Improve Luminance and Luminous efficiencyRF PDP are 3 times more effective at plasma excitation than AC PDPThis results in lower power consumptionThe principle of the PDP canbe summarized as visible light emission from phosphors stimulatedby theUVlight originating from plasma discharge. In mostof the PDP’s developed so far, the plasma discharge in panelpixels originates from low-frequency AC biases between twoelectrodes. Recently, it has been shown that plasma excitationcan occur at a much lower electric field when the electrodes arebiased by a radio-frequency (RF) signal with a frequency rangeof several tens of MHz . Such lower electric field conditionis important since it leads directly to higher power efficiency(approximately three times more power effective than the ACcase ).Boeuf, J.P., et al. "Calculated characteristics of radio-frequency plasma display panel cells including the influence of xenon metastables ." Journal of Applied Physics 92 (2002):
23Ion Sheaths in RF PDPVHF excitation produce high density plasmas with low energy ionsEdge or Skin effects will lead to a maximum ion heating. A maximum heating on the edge is clearly seen when power (and so plasma density) increases.We present an experimental study of a large area capacitive discharge operating at very highfrequency ( from 13 to 100 MHz). VHF excitation is known to produce high density plasmaswith low energy ions, but electromagnetic effects (like standing wave and/or skin effects) cancause non uniformities. The resulting ion flux non-uniformities were examined experimentally.At MHz, the ion flux is uniform whereas the standing wave effect is observed at 60 MHz.When the plasma density increases, we observe an ion flux maximum near the edge that may bedue to the skin effect.An edge effect leading to a maximum in heating at theedge of the discharge always exists in capacitivedischarges due to the proximity of the (generallygrounded) side walls to the RF powered electrode.Fig. 2 shows two different ion flux profiles measuredat 60 MHz and 150 mTorr for an increasing RFpower. At 90 W RF power, we only observed thestanding wave effect, whereas the model alreadypredicts an significant skin effect, showing that themodel tends to overestimate the inductive heating.When power increases, a maximum in density at theedge is observed. This edge heating can be either dueto inductive heating or to edge effects.Electromagnetic (B-Dot) measurements will beperformed to distinguish between these two effects.large area capacitive discharge, proving that thesenon-uniformities exist, and are serious issues forindustrial processes. The next step will be to study theinfluence of frequency on the ion energy uniformityacross the discharge.
24RF PDP Minimum Sustaining Voltage Sustained at lower discharge voltage than voltage needed for breakdownHigh frequency, electrons are confined in the interelectrode gap by the oscillating field.Boeuf, J.P., et al. "Calculated characteristics of radio-frequency plasma display panel cells including the influence of xenon metastables ." Journal of Applied Physics 92 (2002):
25Minimum Applied and Sustain Voltage and Pressure Typical AC PDP350 V Applied Voltage135V Minimum Sustain Voltage400 Torr pressureRF PDP110 V Applied VoltageAs low as 30 V Sustained Voltage300 TorrFig. 1Fig. 2 Cho, Hyoung J., and Kyung Cheol Choi. "Improved Luminance and Luminous Efficiency of AC Plasma Display Panel." IEEE Transaction on Consumer Electronics 49 (2003): Boeuf, J.P., et al. "Calculated characteristics of radio-frequency plasma display panel cells including the influence of xenon metastables ." Journal of Applied Physics 92 (2002):
26RF PDP Pixel Structure RF Pixel Size of pixel = 1.26x1.26x1 mm^3 Fig. 2(a) and (b) show the schematics of the RGB panel pixelstructure. The size of the pixel is [mm ]. Theplasma discharge is caused by the RF power delivered betweenthe RF sustain electrode and the scan electrode embedded inthe dielectrics. The RGB data signals are sent through threedata lines beneath the scan electrode. These data lines are perpendicularto the scan electrode so that it is possible to addresseach pixel by lines. Initially, pulses are appliedon the selected data lines and these pulses generate chargeson the dielectric surface. Then the RF signal on the sustainelectrodes and the residual charges on the selected pixels generatethe plasma discharge. In the RF regime, coupling betweenneighboring pixels is important. Therefore, the coupling componentsbetween the RF electrodes of neighboring pixels haveto be included in the equivalent circuit of the test panel. Eventhough the coupling effects can be accurately accounted for by3-D parameter extraction of the whole array of pixels,it is practically impossible. Instead we have diced the wholearray into 196 blocks of pixels and performed the parameterextraction of the pixels. This is equivalent to theKim,Ki Hyuk Park H.I., “Software-Based Analysis of Radio Frequency Plasma Display Panel for Efficient Design and Impedance Matching” IEEE Transactions On Components And Packaging Technologies, Vol. 24, No. 2, June 2001
27Self-Erasing Discharge Improves luminance and color purity by minimizing neon emission while strengthening VUVSelf-erasing discharge produced through ramped-square sustain pulseTraditional PulsesRamped pulse prevents rapid reduction of electric field which can be an affect of wall charges accumulating. Therefore, the ramped pulse allows a longer sustaining discharge for infrared emission.Ramped Sustain PulseH. Tae, B. Cho, K. Cho, S. Chien, “New Color-Enhancing Discharge Mode Using Self-Erasing Discharge in AC Plasma Display Panel,” IEEE Plasma Science, vol. 31, no. 2, pp , April 2003.
28Traditional Sustain and Discharge Waveforms based on 4 inch test panel for conventional square sustain waveform.Run at 62 kHz, duty ratio of 40% and sustain voltage of 190VIn Fig2b, temporal behavior of wall charge produced within cell. Upper two electrodes are sustain electrodes while lower one is the address electrode.Wall charges are accumulated on the dielectric layer below the two sustain electrodes during the address period prior to applying the sustain pulseii) When the electric field intensity generated within the cell by the sustain voltage plus the accumulating wall charges satisfies discharge condition, discharge current also begins to flow, indicating the production of plasma and emission of IR light seen in 2a-3i.iii) At this time, the space charges produced during the plasma discharge are accumulated on the sustain electrodes with an opposite polarity to the space charges due to the electric field caused by the sustain voltage.2a-2,3: as soon as the discharge current flows, light is emitted and then disappears abruptly because the accumulation of wall charges from the space charges during the plasma discharge causes a reduction in electric field intensityiii) Energetic space charges and metastable atoms still remain after the abrupt extinction of discharge for a very short time then disappear (iv)v) Energetic space charges and metastable atoms must be utilized to improve luminous efficiency…displacement current starts to flow again at falling edge of sustain pulsevi) Cells exhibit same condition as previous stateviii) When another sustain pulse is applied, plasma is again produced within the cellThis process is repeated throughout the sustain period.H. Tae, K. Cho, S. Jang, K. Choi, “Improvement in the Luminous Efficiency Using Ramped-Square Sustain Waveform in an AC Surface-Discharge Plasma Display Panel,” IEEE Trans. Electron Devices, Vol. 48, No. 7, July 2001, pp
29Longer Sustain and Self-Erasing Discharge SED produced by wall charges much like an electrostatic discharge. It allows postitive and negative charges to neutralize while emitting additional photons without using any additional power.4 inch test panel in case of ramped-square sustain waveform with same driving conditions as beforeWall charges are accumulated below the 2 sustain electrodes due to write pulse during address period. As ramped-square sustain pulse is applied to the sustain electrode, displacement current begins to flow.Discharge current begins to flow and IR and visible light are emitted, indicating production of plasmaspace charges produced during plasma discharge are accumulated on the sutain electrodes with opposite polarity due to the electric field, creating a reduced electric field strength and weak discharge. At this time, the ramped-sustain waveform with increased voltage slope is able to prevent the abrupt extinction of the electric field caused by the accumulation of wall charges, resulting in a longer-sustained discharge due to the remaining space charges or metastable atoms. Because this additional sdischarge is due to metastable atoms, it only requires a very small amount of current, enabling the proposed waveform to improve luminous efficiency.At falling edge of (1), another discharge is produced without any additional discharge current consumption and the corresponding light is emitted, whereas at the folling edge of 1 in traditional 2a, there is only a displacement current with no light emission.iv) With the new waveform, electric field intensity in discharge cell after discharge-off at rising edge remains almost constant such that additional wall charges are accumulated from the space charges.vi)This causes the self-erasing discharge due to the excessively accumulated wall charges at the falling edge of the ramped-square pulse, with the two sustain electrodes grounded. Since the self-erasing discharge is produced only by those wall charges accumulated within the ecell, the light emission is generated without any additional discharge current consumption.vii) self-erasing discharge also produces the space charges which are necessary for the next sustain dischargeviii) Since next sustain pulse is applied within .8 microseconds after self-erasing discharge, the next sustain discharge is produced using only space chargesH. Tae, K. Cho, S. Jang, K. Choi, “Improvement in the Luminous Efficiency Using Ramped-Square Sustain Waveform in an AC Surface-Discharge Plasma Display Panel,” IEEE Trans. Electron Devices, Vol. 48, No. 7, July 2001, pp
30Improvements Due to Self-Erasing Discharge This shows the changes in luminance, discharge current consumption, and luminous measured from the 4-in AC-PDP test panel with ramped-square sustain pulses, showing increasing voltage from 0 to Consumption power decreased from 3.17 W to 1.47 W, luminance decreased from 792 cd m to 619 cd m. Luminous efficiency increased from 1.03 lm/W to 1.7 lm/W, which represents a 65% improvement. employing the newThis occurred even at a low frequency of 62 kHzH. Tae, K. Cho, S. Jang, K. Choi, “Improvement in the Luminous Efficiency Using Ramped-Square Sustain Waveform in an AC Surface-Discharge Plasma Display Panel,” IEEE Trans. Electron Devices, Vol. 48, No. 7, July 2001, pp
31Nanotubes In FPD Nano Emissive Display Use CNT Based on the phenomenon of field emission.Consumes 50-70W compares to 700W AC PDPSame Performance as PDPStimulates the phosphors directly with electrons and eliminates the 3 steps process of PDP.Requires a gas to be ionizedwhich in turn emits ultraviolet light thatstimulates a phosphor to produce visible light.Manufacturers involving R&D: Motorola, Samsung, SonyThe working principles of FEDs are comparable to the CRT. Electrons escaping from a cathode are accelerated toward a screen, where their energy is transformed into light. In FEDs electrons are generated by a voltage difference between the cathode tips and closely positioned gates according to the Fowler-Nordheim tunneling equation for field emission. In real devices, efficient electron emission is obtained from a few thousand microtips per pixel formed from Mo or Si (Spindt-type, with tip radii below 1 mm for high field strength), or by replacing the microtip with planar diamond-like carbon films, which are also suitable for electron emission. Principal structure of field emission displays The gate voltage in Spindt-type devices is about 50 V and the dielectric thickness separating gate and cathode is about 1 µm. The anode-cathode distance is 200 µm. A spacer technique is used to avoid glass bending due to atmospheric pressure. The biggest issue in FEDs is that the voltage for the acceleration of electrons is only a few hundred volts. Up to now, no RGB phosphors have been available that could provide enough brightness at these acceleration voltages. Higher accelerating voltages can be used only at the expense of a sophisticated vacuum construction and measures to suppress arcing and sputtering effects.
32SummaryPlasma display panels continue their market battle with LCDs. Each has its advantages and currently dominates particular size marketsImprovements including RF and self-erasing discharge will continue to improve quality and drive down costs and power consumption
33Questions and AnswersFor what size televisions, are plasma display panels generally regarded as superior?42 inches and aboveWhat is the efficiency of xenon excitation in RF PDP?Above 80%