IEEE TRANSACTIONS ON ELECTRON DEVICES, VOL. 57, NO. 1, JANUARY 2010 215

Study on Pulse Waveforms for Improving VoltageMargin and Luminous Efficacy in an AC Plasma

Display Panel Having Auxiliary ElectrodesSung-Min Lee, Chung Sock Choi, Cheol Jang, and Kyung Cheol Choi, Member, IEEE

Abstract—New pulse waveforms applied to an alternating-current plasma display panel (ac PDP) with an auxiliary electrodeare investigated for the purpose of improving the panel’s operat-ing voltage margin and luminous efficacy. In the proposed pulsewaveforms with reciprocal sustain pulses, a pair of positive andnegative sustain pulses is applied to the sustain electrodes simul-taneously and alternately. A positive auxiliary pulse is applied tothe auxiliary electrode immediately after reciprocal sustain pulses.The voltage margin becomes wider, and the luminous efficacy isimproved because of the suppression of the discharge toward theaddress electrode. In the another proposed pulse waveforms withreciprocal sustain and auxiliary pulses, a negative pulse, whichis the same as the negative pulse of reciprocal sustain pulses, isadditionally applied to the auxiliary electrode when reciprocal sus-tain pulses are applied. This negative auxiliary pulse can maintaina high level of luminous efficacy because it supports the effectof the auxiliary pulses. The measurement results show that theoperating voltage margin is about twice wider than that of thetypical pulse waveforms for an ac PDP with an auxiliary electrode;furthermore, the maximum luminous efficacy is able to reach3.14 lm/W in terms of the measurement of the discharge in a 50-inXGA resolution (0.27 mm × 0.81 mm) panel with a white cell anda gas mixture of Ne+20%Xe.

Index Terms—Alternating-current plasma display panel (acPDP), auxiliary electrode, auxiliary pulse, reciprocal pulses.

I. INTRODUCTION

THE ALTERNATING-CURRENT plasma display panel(ac PDP) is a preeminent flat panel display device. AC

PDPs have been widely used for large TV devices on accountof their simple structure, inexpensive fabrication, and easyoperation. If ac PDPs are to become more competitive, twomajor issues need to be resolved: their low luminous efficacyand the address time lag [1], and [2]. In particular, the lowluminous efficacy is regarded as the main drawback of acPDPs. Many studies have endeavored to improve the dischargeefficiency. Some of the successful approaches to improving

Manuscript received June 24, 2009; revised September 21, 2009. Firstpublished November 24, 2009; current version published December 23, 2009.This work was supported in part by the Korean government (MEST) underKorea Research Foundation Grant R11-2007-045-02001-0 and in part by theInformation Display R&D Center, one of the Knowledge Economy FrontierR&D Programs funded by the Ministry of Knowledge Economy of the Koreangovernment, under Grant F0004072-2009-32. The review of this paper wasarranged by Editor H.-S. Tae.

The authors are with the Department of Electrical Engineering, KAIST,Daejeon 305 701, Korea (e-mail: kyungcc@ee.kaist.ac.kr).

Color versions of one or more of the figures in this paper are available onlineat http://ieeexplore.ieee.org.

Digital Object Identifier 10.1109/TED.2009.2034074

the luminous efficacy include the following factors: a high Xecontent [3], and [4], a long discharge electrode gap [5], and[6], a high operating voltage [7], and a protective layer witha narrow bandgap [8]–[10]. Although those approaches havehelped improve the discharge efficiency, they sometimes causeside effects, such as an increase of driving cost induced by thehigh operating voltage, an address time lag delay, and a narrowoperating voltage margin. Thus, further studies are also neededto diminish the side effects.

In our previous works, we proposed a highly efficient ac PDPwith an auxiliary electrode; it was called a FEEL PDP (whereFEEL stands for the fourth electrode for enhancing excitationrate in a long coplanar gap). There are two main reasons thatthe luminous efficacy is improved in a FEEL PDP [11]–[15].First, a long-coplanar-gap discharge between sustain electrodesimproves the luminous efficacy. Although an auxiliary elec-trode centrally located between the sustain electrodes acts asan additional cathode, the main discharge is generated betweensustain electrodes with a gap of 200 μm. Second, an auxiliarypulse is applied to the auxiliary electrode immediately afterthe sustain pulse increases the Xe excitation efficiency. Theauxiliary pulse reduces the wall charges that accumulate on theelectrodes and simultaneously generates the priming particles,thereby decreasing the power consumption and increasing theluminous efficacy. Aside from the improved luminous efficacy,the FEEL PDP has the benefit of a decreased address time lag[16]. If adequate pulses are applied to the auxiliary electrodeduring the reset and address period, the addressing is stabilized,and the address time lag is decreased. However, the FEEL PDPalso has the drawback of a decreased operating voltage margin.This decrease is partly attributed to the decrease in the wallcharges by the auxiliary pulse [17]; it is also attributed to thefact that the discharge is generated toward the address electrodebecause the gap between the sustain electrodes is longer thanthat between the sustain and address electrodes. Therefore,further research on improving the operating voltage margin isnecessary for the successful operation of the FEEL PDP.

In this paper, new pulse waveforms, which were mentionedbriefly in a previous report [18], are investigated in terms ofthe luminance, power consumption, luminous efficacy, voltagedistribution model, and voltage margin. In Section II, the ex-perimental panel is described, and the typical pulse waveformsapplied to the FEEL PDP are discussed. In Section III, thepulse waveforms with various reciprocal sustain pulses arestudied. Although these waveforms can suppress the discharge

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216 IEEE TRANSACTIONS ON ELECTRON DEVICES, VOL. 57, NO. 1, JANUARY 2010

Fig. 1. Schematic diagram of the experimental FEEL PDP test panel.

generated toward the address electrode, they tend to limit themaximum luminous efficacy. Accordingly, in Section IV, waysof optimizing the waveforms are suggested, particularly byapplying appropriate auxiliary pulses with reciprocal sustainpulses, so the waveforms can simultaneously increase the volt-age margin and maximize the luminous efficacy.

II. EXPERIMENTAL PANEL AND TYPICAL PULSE

WAVEFORMS IN SUSTAIN PERIOD

Fig. 1 shows the schematic diagram of a FEEL PDP testpanel. The scan and common electrodes are located on the frontplate as in a conventional ac PDP; an auxiliary electrode iscentrally located between them. The electrodes are made ofindium–tin–oxide (ITO) and silver paste. The gap is 200 μmbetween the sustain electrodes and 50 μm between auxiliaryand sustain electrodes. Note that the coplanar gap betweenthe sustain electrodes is much longer than the correspondinggap in a conventional ac PDP. The sustain ITO electrodes are200 μm wide, and auxiliary ITO electrodes are 100 μm wide.The sustain silver paste electrodes are 60 μm wide, and the aux-iliary silver paste electrodes are 30 μm wide. The electrodes arecovered with a 28-μm-thick layer of a transparent dielectric anda 0.5-μm-thick layer of magnesium oxide (MgO). The addresselectrodes, which are made of silver paste, are formed on therear plate. They have a width of 80 μm and are covered with a20-μm-thick opaque dielectric layer. Red, green, and blue phos-phors are formed within rectangular closed barrier ribs. Thebarrier ribs are 150 μm high, which means that the gap betweenthe sustain and address electrodes is shorter than the gap be-tween the sustain electrodes. The test panel was designed for a50-in XGA resolution panel with a subpixel size of 0.27 mm ×0.81 mm. The Ne+20%Xe gas mixture was used under a totalgas pressure of 450 torr. The size of the test panel was 7 in.

Fig. 2 shows the typical pulse waveforms that are applied tothe FEEL PDP in the sustain period. Previous findings indicatethat the luminous efficacy is greater when the auxiliary pulse isapplied to the afterglow region instead of the glow region [11].Accordingly, the auxiliary pulse is applied immediately afterthe sustain pulse in the typical pulse waveforms for the FEELPDP. The FEEL PDP with high barrier ribs reported in a previ-ous study [15] is well driven by these typical pulse waveforms.However, as with our experimental test panel, the FEEL PDPwith low barrier ribs is often not driven by the typical pulse

Fig. 2. Typical pulse waveforms applied to the FEEL PDP in the sustainperiod.

Fig. 3. Pulse waveforms with various reciprocal sustain pulses applied to theFEEL PDP in the sustain period.

waveforms because the voltage margin is rapidly decreased bythe discharge generated toward the address electrode. In thetypical pulse waveforms, the sustain pulses have a frequencyof 50 kHz and a width of 4 μs, while the auxiliary pulses havea frequency of 100 kHz and a width of 2 μs.

III. PULSE WAVEFORMS WITH RECIPROCAL

SUSTAIN PULSES

The discharge toward the address electrode can be controlledby reciprocal sustain pulses. Fig. 3 shows pulse waveformswith various reciprocal sustain pulses applied to the FEEL PDPin the sustain period. Positive and negative pulses are appliedto each sustain electrode simultaneously and alternately. Apositive auxiliary pulse is applied to the auxiliary electrodeimmediately after the reciprocal sustain pulses, as in the caseof typical pulse waveforms. The address electrode is alwaysgrounded in the sustain period. The sum of the magnitudesof the positive and negative sustain pulses corresponds to thevoltage of the sustain pulse in typical pulse waveforms. Thisvoltage is denoted as VS . To investigate how the reciprocalsustain pulses influence the discharge, we varied the relativemagnitude of the negative sustain pulse; the magnitude ratioof a negative sustain pulse against VS is denoted as rN . Thefrequency and width of each pulse correspond to the frequencyand width of typical pulse waveforms.

As shown in Fig. 4, the luminance and luminous efficacywere measured in accordance with various rN values underconditions of floating and grounded address electrodes at a fixedVS value. These measurements can explain the effect of theaddress electrode in the long-coplanar-gap discharge. Here, thepower consumption was measured by subtracting the consumed

LEE et al.: STUDY ON PULSE WAVEFORMS FOR IMPROVING VOLTAGE MARGIN AND LUMINOUS EFFICACY 217

Fig. 4. Luminance and luminous efficacy with floating auxiliary and addresselectrodes and with a floating auxiliary electrode and a grounded addresselectrode in accordance with various rN values for the sustain pulse voltageof 270 V.

Fig. 5. Voltage margin in accordance with various rN values.

power in the OFF-state panel from that in the ON-state panel.The luminous efficacy was calculated by dividing the lumi-nance multiplied by solid angle π by the power consumptionper a unit discharge area. The auxiliary electrodes were floatedto exclude their influences. For the floating address electrode,the luminance and luminous efficacy do not appear to changesignificantly in accordance with the rN values. However, forthe grounded address electrode, the luminance and luminousefficacy decrease when the rN value decreases, even if theoperation of the test panel fails to fall below an rN value of12%. These decreases of the luminance and luminous efficacyare attributed to the fact that the voltage difference between thesustain electrode of the anode and the address electrode of thecathode decreases if the rN value increases when reciprocalsustain pulses are applied. On the other hand, the voltage differ-ence between the sustain electrodes remains constant. Thus, it isdeduced that the discharge toward the address electrode can besuppressed by reciprocal sustain pulses. In a previous study, anac PDP with long sustain electrode gap was successfully drivenby similar sustain pulses to reciprocal sustain pulses with an rN

value of 50% [19].Fig. 5 shows the voltage margin in accordance with various

rN values. The margins of the sustain and auxiliary pulsevoltages increase when the rN value increases (there is no

margin if the rN value is less than 12%, as mentioned above).The reason why the sustain voltage margin increases with anincrease of the rN value is that the self-erasing dischargegenerated by the positive wall charges that accumulate on theaddress electrode after the sustain discharge is suppressed bya decrease of the voltage difference between the sustain andaddress electrodes during the sustain discharge. In addition, thevoltage difference between the sustain and auxiliary electrodesdecreases when the rN value increases, resulting in a decreaseof the positive wall charges that accumulate on the auxiliaryelectrode after the sustain discharge. This decrease of positivewall charges renders the effect of the auxiliary pulse weakenedand leads to an increase of the auxiliary voltage margin.

Although reciprocal pulses with a high rN value help in-crease the voltage margin, they fail to enhance the luminousefficacy greatly. Fig. 6 shows the luminance, power consump-tion, and luminous efficacy as a function of the auxiliary pulsevoltage in accordance with rN values. For a low rN valueof 12% or 20%, when the auxiliary pulse voltage increases,the luminance increases steadily and the power consumptiondecreases steadily. For an rN value of more than 30%, theluminance decreases gradually until a certain auxiliary pulsevoltage and thereafter increases rapidly. The power consump-tion increases gradually until that auxiliary voltage and there-after decreases slightly. These tendencies can be explained bythe fact that the effect of the auxiliary electrode depends onthe rN value. Fig. 7 shows the voltage difference between thesustain, auxiliary, and address electrodes when the reciprocalsustain pulses are applied; the positive sustain pulse of thereciprocal sustain pulses is applied to the scan electrode. Fora low rN value, the auxiliary electrode acts as an additionalcathode because the voltage difference between the scan andauxiliary electrodes is high and the voltage difference betweenthe auxiliary and common electrodes is low. When the auxiliaryelectrode acts as an additional cathode, a large amount ofpositive wall charges accumulates on the auxiliary electrodeafter the sustain discharge. In this case, the low voltage of theauxiliary pulse can decrease the wall charges and produce prim-ing particles by generating an auxiliary discharge. Accordingto the findings of a previous study, the luminous efficacy canbe improved due to a decrease of power consumption and anincrease of luminance when the wall charges are reduced andthe priming particles are generated by the auxiliary pulse [11],and [14]. The measurement results for a low rN value corre-spond with the previous findings, i.e., the luminous efficacyincreases steadily when the auxiliary pulse voltage increases asa result of a decrease of power consumption and an increaseof luminance. On the other hand, for a high rN value, theauxiliary electrode cannot act as an additional cathode; it actsas a neutral electrode rather than a cathode. A small amountof positive wall charges accumulates on the auxiliary electrodeafter the sustain discharge. In this case, the auxiliary pulsecan reduce the wall charges that accumulate on the sustainelectrodes, but it cannot produce sufficient priming particles;hence, the luminance decreases slightly until the auxiliary pulsevoltage reaches a certain level. In addition, this auxiliary pulseraises the power consumption slightly due to the auxiliarypulse power. The luminous efficacy consequently decreases

218 IEEE TRANSACTIONS ON ELECTRON DEVICES, VOL. 57, NO. 1, JANUARY 2010

Fig. 6. (a) Luminance, (b) power consumption, and (c) luminous efficacy with an increase of the auxiliary pulse voltage in accordance with various rN values.

Fig. 7. Voltage differences between the sustain, auxiliary, and address elec-trodes when reciprocal sustain pulses are applied under the condition of anarbitrary rN value (the positive sustain pulse of the reciprocal sustain pulses isapplied to the scan electrode).

slightly until the auxiliary pulse voltage reaches a certain level.When the auxiliary pulse voltage exceeds this level, an auxiliarydischarge is generated, and the luminance increases rapidlybecause a sufficient number of priming particles are generated.This rapid increase of luminance (rather than the decreaseof power consumption) leads to a rapid increase in luminousefficacy.

Fig. 8 shows the maximum luminous efficacies, with andwithout the auxiliary pulses; it also shows the increased ratio ofthe maximum luminous efficacy caused by the auxiliary pulses.The maximum luminous efficacy without the auxiliary pulses(with the floating auxiliary electrode) increases when the rN

value increases as a result of the suppression of the dischargetoward the address electrode. On the other hand, the luminousefficacy with the auxiliary pulses and the increased ratio areboth maximized when the rN value is 30%. For a high rN

Fig. 8. Maximum luminous efficacy with and without the auxiliary pulses, andthe increased ratio of the maximum luminous efficacy caused by the auxiliarypulses.

value, the luminous efficacy cannot be greatly improved by theauxiliary pulses because only a small amount of positive wallcharges accumulates on the auxiliary electrode after the sustaindischarge. There is also no great improvement in the luminousefficacy for a low rN value because the auxiliary pulse volt-age margin decreases rapidly due to the discharge toward theaddress electrode. Thus, the luminous efficacy reaches a peakwhen the rN value is 30%.

As shown in Figs. 5 and 8, the pulse waveforms with thereciprocal sustain pulses can improve the voltage margin andthe luminous efficacy by suppressing the discharge towardthe address electrode. However, the improvement in luminous

LEE et al.: STUDY ON PULSE WAVEFORMS FOR IMPROVING VOLTAGE MARGIN AND LUMINOUS EFFICACY 219

Fig. 9. RESAP waveforms applied to the FEEL PDP in the sustain period.

efficacy is limited because these pulse waveforms reduce thebeneficial influence of the auxiliary pulses on the luminousefficacy. In addition, the auxiliary pulse voltage needed toimprove the luminous efficacy has a narrow range. The pulsewaveforms therefore need to be modified so that the effect ofthe auxiliary pulses and the suppression of the discharge towardthe address electrode can be maintained.

IV. PULSE WAVEFORMS WITH RESAP

Fig. 9 shows the pulse waveforms with reciprocal sustain andauxiliary pulses (RESAP) in the sustain period. Because themagnitudes of two of the reciprocal sustain pulses are equiv-alent to each other, the sustain discharge toward the addresselectrode can be suppressed. A negative pulse, which is thesame as the negative sustain pulse of reciprocal sustain pulses,is additionally applied to the auxiliary electrode when thereciprocal sustain pulses are applied. This negative pulse makesthe auxiliary electrode act as an additional cathode during thesustain discharge. Therefore, pulse waveforms with RESAPhave two functions: They suppress the discharge toward theaddress electrode, and they support the effect of the auxiliarypulses. These waveforms are called RESAP waveforms.

Fig. 10(a) shows the luminance and power consumption asa function of the auxiliary pulse voltage when typical pulsewaveforms are applied to the FEEL PDP with floating addresselectrodes, and Fig. 10(b) shows the corresponding resultswhen RESAP waveforms are applied. In the case of typicalpulse waveforms with floating address electrodes (where theinfluence of the address electrode can be neglected), the lumi-nance increases and the power consumption decreases gradu-ally as the auxiliary pulse voltage increases. Likewise, in thecase of RESAP waveforms, the luminance increases and thepower consumption decreases as the auxiliary pulse voltageincreases. The RESAP waveforms can maintain the effect ofauxiliary pulses in a manner that is similar to the typical pulsewaveforms for FEEL PDP. Accordingly, the way the luminanceand power consumption vary in accordance with the auxiliarypulse voltage is similar to that of typical waveforms withfloating address electrodes.

Fig. 11 shows the luminous efficacies as a function of theauxiliary pulse voltage in accordance with various sustain pulsevoltages when RESAP waveforms are applied. The luminousefficacy increases steadily as the auxiliary pulse voltage in-creases. This behavior means that RESAP waveforms outper-form pulse waveforms with reciprocal sustain pulses because

Fig. 10. Luminance and power consumption as a function of the auxiliarypulse voltage when different pulse waveforms are applied. (a) Typical pulsewaveforms for the FEEL PDP with floating address electrodes. (b) RESAPwaveforms.

Fig. 11. Luminous efficacy as a function of the auxiliary pulse voltage inaccordance with various sustain pulse voltages when RESAP waveforms areapplied.

the auxiliary pulse voltage has more scope to improve theluminous efficacy. Furthermore, RESAP waveforms have ahigher maximum luminous efficacy of 3.14 lm/W than pulsewaveforms with reciprocal sustain pulses because the RESAPwaveforms help to maintain the effect of auxiliary pulses.

220 IEEE TRANSACTIONS ON ELECTRON DEVICES, VOL. 57, NO. 1, JANUARY 2010

Fig. 12. Operating voltage margin window in accordance with various auxil-iary pulse voltages when different waveforms are applied. (a) Typical drivingwaveforms for the FEEL PDP. (b) RESAP driving waveforms.

Fig. 12 shows the operating voltage margin windows inaccordance with various auxiliary pulse voltages. To comparethe operating margin windows of RESAP waveforms withthose of the typical pulse waveforms for FEEL PDP, we usedanother test panel that had stripe barrier ribs and contained aNe+5%Xe gas mixture. This method enabled us to measurethe operating voltage margin windows even when the typicalpulse waveforms were applied. There is no major differencebetween the address voltage margins of typical driving wave-forms and RESAP driving waveforms. However, the sustainvoltage margin of RESAP driving waveforms is much widerthan that of typical driving waveforms. The auxiliary pulsevoltage margin is also wider. These results are attributed to thefact that the reciprocal sustain pulses suppress the dischargetoward the address electrode.

V. CONCLUSION

New pulse waveforms applied to the FEEL PDP, which is anac PDP with an auxiliary electrode located between the sustainelectrodes, have been studied for the purpose of improving theoperating voltage margin. We investigated the pulse waveforms

with reciprocal sustain pulses. Positive and negative sustainpulses are applied to the sustain electrodes simultaneously andalternately. A positive auxiliary pulse is applied to the auxiliaryelectrode immediately after the reciprocal sustain pulses, andno pulse is applied to the address electrode in the sustainperiod. Reciprocal sustain pulses can suppress the dischargetoward the address electrode. The voltage margin consequentlybecomes wider, and the luminous efficacy without the auxiliarypulses slightly increases when the magnitude ratio of a negativesustain pulse against the total magnitude of reciprocal sustainpulses (rN ) increases. However, because the effect of theauxiliary pulse is reduced due to the neutralized auxiliary elec-trode during the sustain discharge, the luminous efficacy cannotbe maximized for a high rN value; the maximum luminousefficacy is attained when the rN value is 30%. In addition,the auxiliary pulse voltage has a narrow scope for improvingthe luminous efficacy. We therefore propose modified pulsewaveforms called RESAP waveforms. In RESAP waveforms,the discharge toward the address electrode is greatly suppressedbecause the magnitudes of the reciprocal sustain pulses areequivalent to each other. On the other hand, the effect of theauxiliary pulse is not reduced because a pulse, which is thesame as the negative pulse of the reciprocal sustain pulses, isapplied to the auxiliary electrode during the sustain discharge.Therefore, when the FEEL PDP is driven by RESAP wave-forms, the operating voltage margin is better than that of typicalpulse waveforms, and the luminous efficacy is maximized inspite of the use of the pulse waveforms with reciprocal sustainpulses.

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Sung-Min Lee received the B.S. degree in electricalengineering from Seoul National University, Seoul,Korea, in 2006 and the M.S. degree in electricalengineering from KAIST, Daejeon, Korea, in 2008,where he is currently working toward the Ph.D.degree in electrical engineering.

His research interests include new physical de-vices and microplasma applications.

Chung Sock Choi received the B.S. degree in elec-trical and electronics engineering from Chung-AngUniversity, Seoul, Korea, in 2007. He is currentlyworking toward the Ph.D. degree in electrical engi-neering at KAIST, Daejeon, Korea.

His research interests include plasma display pan-els and microplasma applications.

Cheol Jang received the B.S. and M.S. degrees inelectrical engineering from KAIST, Daejeon, Korea,in 2006 and 2008, respectively, where he is cur-rently working toward the Ph.D. degree in electricalengineering.

His research interests include microplasma appli-cations and flexible displays.

Kyung Cheol Choi (M’04) received the B.S. de-gree from the Department of Electrical Engineering,Seoul National University, Seoul, Korea, in 1986 andthe M.S. and Ph.D. degrees in plasma engineeringfrom Seoul National University, in 1988 and 1993,respectively.

From 1993 to 1995, he was with the Institutefor Advanced Engineering, Seoul, where his workfocused on the design of display devices. From 1995to 1996, he was a Research Scientist with SpectronCorporation of America, Summit, NJ. From 1996

to 1998, he was a Senior Research Scientist with Hyundai Plasma Display,Hawthorne, NY. From 1998 to 1999, he was a Senior Research Scientistwith the Advanced Display R&D Center, Hyundai Electronics Industries,Gyounggi-do, Korea, where he was involved in the development of a 40-in acPDP. From 2000 to 2004, he was an Associate Professor with the Departmentof Electronics Engineering, Sejong University, Seoul. He was also in charge ofthe Information Display Research Center supported by the Korean Ministry ofInformation and Communication. Since 2005, he has been with the Departmentof Electrical Engineering, KAIST, Daejeon, Korea, where he was first anAssociate Professor and is currently a Professor. Since September 2007, hehas been in charge of the Center for Advanced Flexible Display Convergencesupported by the Korean Ministry of Education, Science, and Technology.His research interests include flexible displays, plasma display panels, organiclight-emitting diodes, and surface plasmon applications for displays.

Dr. Choi is a member of the Society for Information Display and the KoreanInformation Display Society. He is an Associate Editor of the IEEE/OSAJournal of Display Technology.