plasma display panels: problems and their analysis via computer simulations

Plasma display panels: Plasma display panels: problems and their analysis via problems and their analysis via

computer simulationscomputer simulations

V.P. NagornyV.P. Nagorny, V.N. Khudik, P.J. Drallos, V.N. Khudik, P.J. DrallosPlasma Dynamics Corporation, USAPlasma Dynamics Corporation, USA

A. ShvydkyA. ShvydkyUniversity of Toledo, USAUniversity of Toledo, USA

Plasma Dynamics Corporation IPlasma Dynamics Corporation IMID'05MID'05

IntroductionIntroduction Could anybody imagined 5 years ago the question: PDP or LCD Could anybody imagined 5 years ago the question: PDP or LCD

for large displays?for large displays?

Competition from LCD becomes really strongCompetition from LCD becomes really strong Rapid falling prices ( reaching $1/ sq in at retail )Rapid falling prices ( reaching $1/ sq in at retail ) Response time (is approaching 3ms (<10ms))Response time (is approaching 3ms (<10ms)) Color gamut (better than NTSC)Color gamut (better than NTSC) High Contrast (> 500:1 High Contrast (> 500:1 1000:1) 1000:1) Large Pixel counts (~ 10M )Large Pixel counts (~ 10M ) The viewing angle is improvingThe viewing angle is improving Color filter may disappear - going to LED illuminationColor filter may disappear - going to LED illumination

PDP – improved power consumption, image burning problem, …, PDP – improved power consumption, image burning problem, …, but the main problems that we had 10 years ago are still there: but the main problems that we had 10 years ago are still there:

Efficiency, and BrightnessEfficiency, and Brightness Addressing speed Addressing speed

We better do something about these problems and quick.We better do something about these problems and quick.


How we are doing with researchHow we are doing with research Matrix PDP – quasi 1DMatrix PDP – quasi 1D

More Xe - higher efficiency, but also higher voltage More Xe - higher efficiency, but also higher voltage (from 1D).(from 1D). Larger Secondary Emission – Good for efficiency Larger Secondary Emission – Good for efficiency (from 1D).(from 1D). Larger GapLarger Gap – Good for efficiency – Good for efficiency (from 1D).(from 1D).

Coplanar PDP is very complicated (many new elements – essential multi-D, barrier ribs, Coplanar PDP is very complicated (many new elements – essential multi-D, barrier ribs, complex electric field configuration, cathode wave, striations, …) complex electric field configuration, cathode wave, striations, …)

Qualitative results – good (2D, 3D, observations) :Qualitative results – good (2D, 3D, observations) :• Discharge structure and dynamicsDischarge structure and dynamics• Cathode and anode waves, striationsCathode and anode waves, striations• New modes of the discharge New modes of the discharge • New types ofNew types of instabilities instabilities • … …

Quantitative results – messy (lack of “tools”, difficulty due to a size):Quantitative results – messy (lack of “tools”, difficulty due to a size):• Efficiency – results can’t be trusted. Codes have built-in error ~XX%. Efficiency – results can’t be trusted. Codes have built-in error ~XX%. • Cathode wave – numerical diffusion is faster than the real waveCathode wave – numerical diffusion is faster than the real wave• Striations – no quantitative results Striations – no quantitative results • Observations – sketchy. No comparison/control of ALL the factors. Observations – sketchy. No comparison/control of ALL the factors. • Some data are STILL ASSUMED (Some data are STILL ASSUMED (Xe,NeXe,Ne, , PhosPhos, other ), other )


Can we do better?Can we do better?

Yes – new powerful tools (kinetic codes), allowing Yes – new powerful tools (kinetic codes), allowing quantitative investigations are developed or being quantitative investigations are developed or being developed. We can now investigate properties of all developed. We can now investigate properties of all kinds of PDP discharges, including addressing speed, kinds of PDP discharges, including addressing speed, jitter, even efficiency... and make numerical jitter, even efficiency... and make numerical experiments, that impossible or expensive to do in a experiments, that impossible or expensive to do in a real physical system.real physical system.

One still needs measurements of certain basic One still needs measurements of certain basic parameters, that affect the regime of operation of a parameters, that affect the regime of operation of a pdp cell, so that investigation will be more focused. pdp cell, so that investigation will be more focused. One also needs more detailed analysis of physical One also needs more detailed analysis of physical experiments, especially those made on the panel.experiments, especially those made on the panel.


New tools in actionNew tools in action Experimenting with Kinetic Codes Experimenting with Kinetic Codes

Ramp discharge – dual nature, stabilityRamp discharge – dual nature, stability

Sustain dischargeSustain discharge StriationsStriations Cathode wave – speedCathode wave – speed

Loading effects - Small vs. Large panelLoading effects - Small vs. Large panel


Ramp DischargeRamp Discharge L. F. Weber (1995-1998)L. F. Weber (1995-1998) II00=CdV/dt=CdV/dt


Ramp DischargeRamp Discharge

Ideal for the test of 3D PIC/MC - Known solution (fluid Ideal for the test of 3D PIC/MC - Known solution (fluid

theory –analytical and numerical).theory –analytical and numerical). Faster than 3D fluid Faster than 3D fluid

codecode <N<Nii>=>=i i (I(I0 0 /2e)=(/2e)=(i i /2e)CdV/dt ~ (1-6)10/2e)CdV/dt ~ (1-6)1044

Stable if:Stable if: Good primingGood priming dV/dt < RdV/dt < Rmaxmax (L,(L, ))

0

2 104

4 104

6 104

8 104

1 105

0 10 20 30 40 50Time, us


Ramp DischargeRamp Discharge 3D cell, 3D PIC/MC simulation vs. 3D Fluid3D cell, 3D PIC/MC simulation vs. 3D Fluid

0

1 105

2 105

3 105

0 10 20 30 40 50Time, us

Mix: 86%Ne+14%XeGammaNe=0.64GammaXe=0.001Ramp Rate 3V/us


Ramp DischargeRamp Discharge 1D cell, Ramp Rate = 1V/us, < N1D cell, Ramp Rate = 1V/us, < Ni i > ~ 3300 (3D PIC/MC)> ~ 3300 (3D PIC/MC)

1

10

100

1000

104

0 2 4 6 8 10 12 14Time, us

Mixture 93%Ne+7%XeGamma(Ne)=0.64Gamma(Xe)=0.01Ramp Rate 1V/us



1D cell, < Ni > ~15000 (3D PIC/MC)1D cell, < Ni > ~15000 (3D PIC/MC)

0

2 104

4 104

6 104

8 104

1 105

0 20 40 60 80 100Time, us

Mixture 93%Ne+7%XeGamma(Ne)=0.64Gamma(Xe)=0.01

----- C=0.064pF, 1V/us

----- C=0.016pF, 4V/us



1D cell, < Ni > ~15000 (3D PIC/MC)1D cell, < Ni > ~15000 (3D PIC/MC)

1

10

100

1000

104

105

0 20 40 60 80 100Time, us

Mixture 93%Ne+7%XeGamma(Ne)=0.64Gamma(Xe)=0.01

----- C=0.064pF, 1V/us----- C=0.016pF, 4V/us



Fluctuations in equilibrium Fluctuations in equilibrium N ~ NN ~ N1/21/2

NN

For For < N< Ni i > ~ 10000, > ~ 10000, NNi i ~100 (1%)~100 (1%) - fluid - fluid

approximation seems good (99.7% less approximation seems good (99.7% less than 3than 3))



In the Townsend discharge In the Townsend discharge NNii is the result of a balance, is the result of a balance,

rather than equilibrium (rather than equilibrium (N ~ NN ~ N1/21/2 ): ): NNii N Ne e = = NNii N Ni i = (= (NNi i ) exp() exp(L) = NL) = Nii

• NNe e = = NNii + + ((NNii ) )1/2 1/2 NNi i + + ( N( Ni i //))1/21/2 (sec. emis.) (sec. emis.)

• NNee==NNii N Ni i + + NNii (avalanche), (avalanche), NNi i ~ ( N~ ( Ni i //))1/21/2

NNii ~ ~ ( N( Ni i //))1/2 1/2 >>>> ( N( Ni i ))1/21/2

For the Ramp discharge PDP cell is statistically small.For the Ramp discharge PDP cell is statistically small.



Ramp discharge may be statistically unstable.Ramp discharge may be statistically unstable.

VVcellcell ~10 ~10 -5 -5 cm cm33

n > nn > nminmin ~10 ~1055cmcm-3-3

< < maxmax

----------------------------------------------------------------------

Fluctuations lead to Fluctuations lead to diffusion between “fluid diffusion between “fluid trajectories”. Oscillations trajectories”. Oscillations increase or decrease increase or decrease until large oscillation until large oscillation occurs.occurs.

max



1D cell, 3D PIC/MC : 1D cell, 3D PIC/MC : XeXe- dependence- dependence

Statistical Instability is powerful – it works even when Statistical Instability is powerful – it works even when <N<Ni i >> and and

are large. One needs are large. One needs external sourceexternal source to restart discharge. to restart discharge.

1

10

100

1000

104

105

0 20 40 60 80 100Time, us

1D Cell: C=0.02pFdV/dt=3V/usMix: 93%Ne+7%Xe

------- GammaXe = 0.1------- GammaXe = 0.001


Ramp DischargeRamp Discharge Exoemission (1D test cell – Exoemission (1D test cell – initially emptyinitially empty, 3D PIC/MC, , 3D PIC/MC,

<N<Ni i >=15000,>=15000, XeXe= 0.001, 7% mix= 0.001, 7% mix ) )

0

2 104

4 104

6 104

8 104

1 105

0 10 20 30 40 50Time, us

-------- 5e/us

-------- 100e/us



Exoemission - 3D cell Exoemission - 3D cell initially emptyinitially empty, 3D PIC/MC, , 3D PIC/MC, < N< Nii > ~ 60000 > ~ 60000

0

1 105

2 105

3 105

4 105

5 105

6 105

7 105

0 10 20 30 40 50Time, us

-------- 5 e/us-------- 100 e/us-------- 250e/us

Mix: 86%Ne+14%XeGammaNe=0.64GammaXe=0.001Ramp Rate 3V/us


Ramp Discharge SummaryRamp Discharge Summary

Ramp discharge (RD) exhibits Ramp discharge (RD) exhibits dualdual nature – fluid and nature – fluid and statisticalstatistical..

For the Ramp discharge PDP cell is statistically small.For the Ramp discharge PDP cell is statistically small. RD is statistically unstable RD is statistically unstable unless external source of electrons is present. Average of simulations of unless external source of electrons is present. Average of simulations of 100 cells with different 100 cells with different random seedrandom seed numbers (no exoemission) showed numbers (no exoemission) showed much more fluid-like behavior, with much smaller fluctuations much more fluid-like behavior, with much smaller fluctuations ramp ramp measurements based on LINE current or/and light integration, can miss the measurements based on LINE current or/and light integration, can miss the statistical part of the ramp discharge behavior. Experiments on macrocell statistical part of the ramp discharge behavior. Experiments on macrocell also miss statistical effects (very large N).also miss statistical effects (very large N).

In low-In low-XeXe mixtures some stabilization may be from metastables, but in hi- mixtures some stabilization may be from metastables, but in hi-XeXe mixtures only exoemission can stabilize the ramp.mixtures only exoemission can stabilize the ramp.

With larger With larger XeXe, the required level of exoemission may be smaller., the required level of exoemission may be smaller.

StillStill no reliable data on no reliable data on XeXe and exoemission rate, as well as and exoemission rate, as well as Xe,NeXe,Ne in the in the presence of exoemissionpresence of exoemission – data critical for stability, efficiency, addressing, – data critical for stability, efficiency, addressing, lifetime !!!!lifetime !!!!


Sustain Discharge – ExperimentsSustain Discharge – Experiments Current physical observations do not distinguish between different Current physical observations do not distinguish between different

mechanisms of the processes. Special experiments would be very mechanisms of the processes. Special experiments would be very expensive to make, but 2D/3D PIC/MC simulations can do the job. expensive to make, but 2D/3D PIC/MC simulations can do the job.

Mesh: Mesh: 135x60x22135x60x22


Sustain Discharge – StriationsSustain Discharge – Striations GuessGuess: Anode striations caused by the ion-sound waves, : Anode striations caused by the ion-sound waves,

or/and modulation of the surface charge on the cathode.or/and modulation of the surface charge on the cathode. Freeze ions above the part of the anode - Striation are even Freeze ions above the part of the anode - Striation are even

more pronounced, and stay.more pronounced, and stay. They are not a result of ion They are not a result of ion motion, have nothing to do with ion sound.motion, have nothing to do with ion sound.

Used uniform charge distribution, or no charge on the cathode Used uniform charge distribution, or no charge on the cathode


Sustain Discharge – StriationsSustain Discharge – Striations GuessGuess : Anode striations – is a plasma ionization wave; the : Anode striations – is a plasma ionization wave; the

cathode wave – is the surface charging wavecathode wave – is the surface charging wave (there is no way (there is no way to distinguish between these mechanisms just from to distinguish between these mechanisms just from observation).observation). RealityReality – Almost opposite: – Almost opposite:

1. experiment with 1. experiment with dd//=10=10 -4-4 (metal).(metal).


Sustain Discharge – StriationsSustain Discharge – Striations 2. “2. “No CathodeNo Cathode” experiment, “frozen” ions. Results:” experiment, “frozen” ions. Results:

a) a) S ~ QS ~ Qeed/(d/(E), vE), vf f ~ I~ Iee(t) (t)

b) b) No significant difference between narrow (0-1eV), and wide (0-8eV) No significant difference between narrow (0-1eV), and wide (0-8eV) EDF of the source S.EDF of the source S.

Ion density (top) Charge Deposition Rate

Ion density (side) Potential (side)


Sustain Discharge – StriationsSustain Discharge – Striations

GuessGuess: There is about : There is about 12V12V ( ( IIXeXe) between striations ) between striations

voltage across PC is about voltage across PC is about 12V x N12V x Nstr str . .

RealityReality – the voltage between striations decreases with – the voltage between striations decreases with timetime. Typically it starts with 12-13V, but by the time the . Typically it starts with 12-13V, but by the time the last striation appears, the voltage between first ones may last striation appears, the voltage between first ones may be just be just 2-3 V2-3 V. Voltage across PC continue to decrease . Voltage across PC continue to decrease

after the anode is completely covered by electrons.after the anode is completely covered by electrons.



GuessGuess: Striations of PDP sustain discharge similar to : Striations of PDP sustain discharge similar to those that occur in DC positive column.those that occur in DC positive column.

RealityReality: PDP striations appear in the process of charging : PDP striations appear in the process of charging dielectric, ion motion is not important for their formations, dielectric, ion motion is not important for their formations, and they and they disappear due to an ion motiondisappear due to an ion motion. In the DC . In the DC positive column stationary striations require ion motion. positive column stationary striations require ion motion.



The formation of the striations follow the charging of the anode The formation of the striations follow the charging of the anode dielectric and formation of the conducting channel near the dielectric and formation of the conducting channel near the surface. The process of charging the surface limits the speed of surface. The process of charging the surface limits the speed of the appearing of the striations. the appearing of the striations.

Ions inside the channel do not actively participate in the creation Ions inside the channel do not actively participate in the creation of dense areas – they may be considered immobilized. It is of dense areas – they may be considered immobilized. It is ionization by electrons, and the consequent decreasing of the ionization by electrons, and the consequent decreasing of the electric field in the area makes a striation.electric field in the area makes a striation.

Speed increases with thicker dielectric Speed increases with thicker dielectric d/d/ (same current), larger (same current), larger current, lower normal electric field above the anode.current, lower normal electric field above the anode.



Striations near the address electrode


Sustain Discharge – Cathode WaveSustain Discharge – Cathode Wave

Cathode wave speed investigation Cathode wave speed investigation There is not enough experimental data that would allow There is not enough experimental data that would allow

distinguish one mechanism of the wave propagation from distinguish one mechanism of the wave propagation from another. Speed changes during propagation, hard to say why.another. Speed changes during propagation, hard to say why.

Fluid codes as well as kinetic Boltzmann codes suffer from Fluid codes as well as kinetic Boltzmann codes suffer from numerical diffusion, rising from convective term numerical diffusion, rising from convective term or or

. Numerical diffusion of ions, is especially important, . Numerical diffusion of ions, is especially important, since it is responsible for artificial spread of ions ahead of the since it is responsible for artificial spread of ions ahead of the realreal cathode wave. cathode wave.

Our previous 3D simulations have shown that the wave speed is Our previous 3D simulations have shown that the wave speed is of the order of the ion velocity in the cathode area, but we didn’t of the order of the ion velocity in the cathode area, but we didn’t obtain self-similar behavior, since discharge dynamics affected obtain self-similar behavior, since discharge dynamics affected the speed.the speed.

( )v f


Sustain Discharge –Cathode WaveSustain Discharge –Cathode Wave

““Experimental” setup for the CW speed investigation, using 3D/2D Experimental” setup for the CW speed investigation, using 3D/2D PIC/MC codes. PIC/MC codes.

Cathode, Cathode, V = 0V = 0

Dielectric,

plasma

An

ode

, A

nod

e, V

=V

V=

Vaa

dielectric: d,



self-similar behavior.self-similar behavior.

Dielectric thickness Dielectric thickness

d/d/=10=10, ,

VVaa= 500V,= 500V,

= 0.5 (pure Ne); = 0.5 (pure Ne);

Resolution 600x320 (field).Resolution 600x320 (field).

S, / C

ni

ne

0.01 0.02 0.03 0.04 0.05 0.06

100

200

300

400

500

• CW speed investigation (Fully-Conservative 2D PIC/MC)CW speed investigation (Fully-Conservative 2D PIC/MC)

t = 90.5nsV=2.2km/s



self-similar behavior.self-similar behavior.

Dielectric thickness Dielectric thickness

d/d/=10=10, ,

VVaa=500V,=500V,

=0.5 (pure Ne); =0.5 (pure Ne);

Resolution 600x320 (field).Resolution 600x320 (field).

S, / C

ni

ne

• CW speed investigation (Fully-Conservative 2D PIC/MC)CW speed investigation (Fully-Conservative 2D PIC/MC)

t = 183 nsv=2.2km/s

0.01 0.02 0.03 0.04 0.05 0.06

100

200

300

400

500


Sustain Discharge –Cathode WaveSustain Discharge –Cathode Wave

180m A B 240m20m

50m

270 A B 31020

40

Effect of diffusion on the cathode wave structure

De=Di=0 De, Di ≠ 0



Speed of the CW, Speed of the CW, vvCFCF (when it propagates) is about the (when it propagates) is about the

ion speed near the surface in front of the CW, ion speed near the surface in front of the CW, vvCF CF ~ v~ vii . . Diffusion and the angle at which electric field enters the Diffusion and the angle at which electric field enters the dielectric is very important for the propagation of the dielectric is very important for the propagation of the

Cathode Wave.Cathode Wave. It is ironic that in the conditions of a pdp It is ironic that in the conditions of a pdp ((d d //~ ~ a few microns) the cathode wave charges a few microns) the cathode wave charges dielectric capacitor almost completely, so it may seem dielectric capacitor almost completely, so it may seem that it is a charging wave. that it is a charging wave.

vvCFCF increases with increases with Thinner dielectric: Thinner dielectric: d d // Larger electric field near the tip.Larger electric field near the tip.


Single Cell vs. Row of CellsSingle Cell vs. Row of Cells Display line has ~ 3000-6000 cells; Number of lines ~500-1000.Display line has ~ 3000-6000 cells; Number of lines ~500-1000.

Wires have resistance, inductance, capacitance (Wires have resistance, inductance, capacitance (R, L, CR, L, C) – which ) – which may be important, when many cells work together. These may be important, when many cells work together. These parameters (parameters (R, L, CR, L, C) change when one moves from 42 to 60in panel ) change when one moves from 42 to 60in panel or from 840 to 1920 pixels/line even if pixels or wires stay the same.or from 840 to 1920 pixels/line even if pixels or wires stay the same.

Interaction between cells may strongly affect the work of individual Interaction between cells may strongly affect the work of individual cell. Voltage applied to a cell may differ from the desirable. This may cell. Voltage applied to a cell may differ from the desirable. This may change the “rules of the game” - a cell design or driving waveform change the “rules of the game” - a cell design or driving waveform may work good in one panel and not so good in the other one, or in may work good in one panel and not so good in the other one, or in the same panel when many pixels are turned ON. the same panel when many pixels are turned ON.

Current measurements do not show the voltage and the current Current measurements do not show the voltage and the current through an individual cell. What can we do about it?through an individual cell. What can we do about it?


Single Cell vs. Row of CellsSingle Cell vs. Row of Cells

Simplification: All lines work together, all lines Simplification: All lines work together, all lines are identical.are identical.

Single charge between Single charge between metal plates - difficultmetal plates - difficult

Many charges - simpleMany charges - simple

Q



Single row – difficult:Single row – difficult:One has to consider One has to consider interaction with many rowsinteraction with many rows

Many rows – simpler: Many rows – simpler: one may consider one row with one may consider one row with correct boundary conditionscorrect boundary conditions



From original 18 matrix elements in a cellFrom original 18 matrix elements in a cell C C11 11 - C- C3333, L, L11 11 - L- L3333 , , only 6 or 7 only 6 or 7

are independentare independent (due to a symmetry of a cell), which(due to a symmetry of a cell), which for sustain for sustain dischargedischarge can be organized in just five combinations: can be organized in just five combinations: CC11 - C - C3 3 ,, LLA A , L, LBB ..

Transformers Transformers AA and and BB : : VVAA=L=LA A d/dt(Id/dt(I1 1 - I- I2 2 ), ), VVBB=L=LB B d/dt(Id/dt(I11+I+I2 2 - I- I3 3 ))

( I Positive direction )



Single cellSingle cell


Single Cell vs. Row of CellsSingle Cell vs. Row of Cells Many cells, medium load (probably most important)Many cells, medium load (probably most important)


Single Cell vs. Row of CellsSingle Cell vs. Row of Cells Many cells, large loadMany cells, large load


SummarySummary Once again, what it’s gonna be: LCD or PDP? Once again, what it’s gonna be: LCD or PDP?

– My answer: It depends. It depends on the – My answer: It depends. It depends on the future progress of PDPs.future progress of PDPs.

The next generation of PDPs will be simpler, much more The next generation of PDPs will be simpler, much more efficient, but we need to accelerate our progress NOW. efficient, but we need to accelerate our progress NOW. We need a breakthroughWe need a breakthrough, especially on efficiency and , especially on efficiency and addressing speed. Using kinetic codes for making addressing speed. Using kinetic codes for making numerical experiments where it’s difficult to make or numerical experiments where it’s difficult to make or analyze a real ones, is essential. Today’s computer analyze a real ones, is essential. Today’s computer codes and computer power are good enough for this codes and computer power are good enough for this task.task.

plasma display panels: problems and their analysis via computer simulations

Documents

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coplanar pdp

qualitative results