Stability of Positive Resistance Discharges for AC PDPs

1. Stability of Positive Resistance Discharges for AC PDPs Vladimir P. Nagorny, Paul J. Drallos Plasma Dynamics Corporation Larry F. Weber Plasmaco, Inc., Subsidiary of Matsushita Electric Industrial Co., Ltd

2. 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 V.P.Nagorny, P.J.Drallos, L.F.Weber

3. 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 V.P.Nagorny, P.J.Drallos, L.F.Weber

4. Stability1. Steady state • Ideal Ramp and DC discharge • Ist and V belong to (I-V)DC curve V.P.Nagorny, P.J.Drallos, L.F.Weber

5. Stability2. Absolutely unstable ramp • Negative resistance or no DC state even exist - unstable • - Unstable V.P.Nagorny, P.J.Drallos, L.F.Weber

6. Stability3. Positive resistance region V.P.Nagorny, P.J.Drallos, L.F.Weber

7. 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 V.P.Nagorny, P.J.Drallos, L.F.Weber

8. Another example • Same initial conditions, but 7.5 higher ramp rate resulted in 300 time larger peak current V.P.Nagorny, P.J.Drallos, L.F.Weber

9. 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 asparticle ‘s momentum p • Energy: V.P.Nagorny, P.J.Drallos, L.F.Weber

10. 1D analysis (continue) • Periodic non-harmonic oscillations, with amplitude depending on the “energy” • Initial conditions: j/jDC , E-Ebr • dV/dt V.P.Nagorny, P.J.Drallos, L.F.Weber

11. 1D analysis (continue) • I(t), VGap(t) - (qualitative pictures) • Small amplitude: • Large amplitude: V.P.Nagorny, P.J.Drallos, L.F.Weber

12. Metastables • Metastables limit the minimum current • With every pulse, the number of metastables increases until equilibrium is reached V.P.Nagorny, P.J.Drallos, L.F.Weber

13. 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 DV V.P.Nagorny, P.J.Drallos, L.F.Weber

14. 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. V.P.Nagorny, P.J.Drallos, L.F.Weber