Stability of Positive Resistance Discharges for AC PDPs

Vladimir P. Nagorny, Paul J. DrallosPlasma Dynamics Corporation

Larry F. WeberPlasmaco, Inc., Subsidiary of Matsushita Electric Industrial Co., Ltd

SID 2000 V.P.Nagorny, P.J.Drallos, L.F.Weber

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ADS Addressing

Reliable addressing: Ionization level Wall charge conditions

Setup period: Bulk Write-Erase

sequence Pros: reliable addressing Cons: uniformity requirements,

high setup & address voltages, low contrast

Setup Periods

SF1 SF2 SF3 SF4 SF5 SF6 SF7 SF8

SID 2000 V.P.Nagorny, P.J.Drallos, L.F.Weber

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Weber’s setup - Ramp (1994 -1998)

Ramp-up+Ramp-down

Pros: very tolerant to large cell

differences low current low light

Cons: (?)Stability of the wall

voltage

SID 2000 V.P.Nagorny, P.J.Drallos, L.F.Weber

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Stability1. Steady state

Ideal Ramp and DC discharge

Ist and V belong to (I-V)DC curve

I C dV dt Ist diel DC /

j j constRamp DC ,

n x t n x n x t n xi i DC e e DC( , ) ( ), ( , ) ( ), ,

V Vgap b

SID 2000 V.P.Nagorny, P.J.Drallos, L.F.Weber

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Stability2. Absolutely unstable ramp

Negative resistance or no DC state even exist - unstable

- Unstable

I I V Vcrit b ,

CdV dt Icrit/

SID 2000 V.P.Nagorny, P.J.Drallos, L.F.Weber

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Stability3. Positive resistance region

C dV dt Icrit/

n x t n xi iDC( , ) ( ), 0

n x t n xe eDC( , ) ( ) 0

V V I VDC b ( )

SID 2000 V.P.Nagorny, P.J.Drallos, L.F.Weber

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Example-computer simulations

Discharge can’t be turned on instantaneously - this causes oscillations

If deviations are large, and the ramp-rate is high, it is unstable

SID 2000 V.P.Nagorny, P.J.Drallos, L.F.Weber

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Another example

Same initial conditions, but 7.5 higher ramp rate resulted in 300 time larger peak current

SID 2000 V.P.Nagorny, P.J.Drallos, L.F.Weber

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1D analysis

Small deviations from DC parameters can be analyzed analytically

Equations for ln(j/jDC), and E-Ebr or V-Vb are similar to equations for 1D motion of a particle in the potential U=U(j).

dx/dt=p/m*, dp/dt=- dU/dx

ln(j/jDC) - serves as coordinate x

E-Ebr - serves as particle ‘s momentum p

Energy: E ( ) / ( )*E E m U j constbr2 2

SID 2000 V.P.Nagorny, P.J.Drallos, L.F.Weber

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1D analysis (continue)

Periodic non-harmonic oscillations, with amplitude depending on the “energy”

Initial conditions: j/jDC , E-Ebr

dV/dt

U j dV dt j j j jDC DC( ) ( / ) ( / ) ln( / )

E ( ) / ( )*E E m U jbr2 2

min ( ) @ /U j j j CdV dtDC

SID 2000 V.P.Nagorny, P.J.Drallos, L.F.Weber

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1D analysis (continue)

I(t), VGap(t) - (qualitative pictures)

Small amplitude:

Large amplitude:

Gap Voltage

Current

max ~ DCj j

max DCj j

0 ~ ( / ) /br

iVV L

/appldV dt

max 0~ 5 /large DCj j

SID 2000 V.P.Nagorny, P.J.Drallos, L.F.Weber

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Metastables

Metastables limit the minimum current

With every pulse, the number of metastables increases until equilibrium is reached

SID 2000 V.P.Nagorny, P.J.Drallos, L.F.Weber

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Ramp Strategy

Start with Vramp=Vb

Ramp up to more than Vsust+Vb+δVrelax

Change voltage by -2Vb , and ramp down to -Vb

Raise voltage by V

-200

-100

0

100

200

300

400

0 50 100 150 200 250Time, mks

V Vb 150V Vb 135V Vb 165

-200

-100

0

100

200

300

400

0 50 100 150 200 250Time, mks

Vw1

Vw2

V

VS V Vb 2

SID 2000 V.P.Nagorny, P.J.Drallos, L.F.Weber

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Summary

Weber’s setup provides very precise conditions in every cell prior to addressing, independently on their parameters

The stability depends very much on the initial priming conditions

Our analysis enables one to optimize the ramp strategy and parameters to obtain the stable setup with low light output

The positive resistance discharge (ramp) is being used in the Panasonic 37”-42” products and Plasmaco’s 60” diagonal prototype color AC-PDPs.