Method for operating PDP

Details Method for operating PDP Method for operating PDP

2002-05-09

2003-09-16

Vu, David (Department: 2821)

Electric lamp and discharge devices: systems

Plural power supplies

Plural cathode and/or anode load device

C315S169400, C345S060000, C345S063000

Reexamination Certificate

active

06621230

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a plasma display panel, and more particularly, to a method for operating a plasma display panel (PDP), in which a pulse applied to an electrode in the PDP is controlled according to a gray scale of a picture to be displayed.
2. Background of the Related Art
Of the different flat board type display devices, the PDP is paid attention as a large sized panel because the PDP has many advantages suitable for fabricating a large sized display device.
Most typically, the PDP is provided with 3 electrodes and is driven by an AC voltage, called as an AC surface discharge type PDP.
FIG. 1
illustrates a perspective view of a discharge cell of a related art AC PDP of surface discharge type having 3-electrodes.
Referring to
FIG. 1
, the discharge cell is provided with a scan electrode
12
Y and a common sustain electrode
12
Z formed on a front substrate
10
, and an address electrode
20
X formed on a back substrate
18
.
There are a front dielectric
14
and a protective layer
16
stacked on the front substrate
10
having the scan electrode
12
Y and the common sustain electrode
12
Z formed in parallel. The front dielectric
14
is provided for accumulation of wall charge generated in plasma discharge.
The protective layer is provided for protecting the front dielectric
14
from damage caused by sputtering of the plasma discharge, and enhancing a secondary electron emission efficiency. In general, the protective layer
16
is formed of magnesium oxide MgO.
There are a back dielectric
22
and a barrier rib
24
on the back substrate
18
having the address electrode
20
X formed thereon. There is a phosphors
26
coated on surfaces of the back dielectric
22
and the barrier rib
24
. The address electrode
20
X is formed in a direction perpendicular both to the scan electrode
12
Y and the common sustain electrode
12
Z. The phosphors
26
are excited by UV ray emitted in the plasma discharge, to emit one of red, green, and blue visible light. There is an inert gas injected into a discharge space between the two substrates and the barrier rib.
Referring to
FIG. 2
, there are a matrix of the discharge cells arranged in the PDP.
Referring to
FIG. 2
, the discharge cell
1
has a scan electrode line Y
1
, - - - , or Ym and a sustain electrode line Z
1
, - - - , or Zm running in parallel, and the discharge cell is provided in every part the two electrode lines Y
1
, - - - , and Ym and Z
1
, - - - , and Zm cross the address electrode lines X
1
, - - - , and Xn.
The scan electrode lines Y
1
, - - - , and Ym are operative in a sequence, and the common sustain electrode line Z
1
, - - - , and Zm are operative in common. The address electrode lines X
1
, - - - , Xn are operative with odd numbered lines and even numbered lines divided.
In the related art AC PDP of surface discharge type having 3-electrodes, an operation time period for displaying a particular grey scale of a frame is divided into sub-fields. In each of sub-field duration, a number of times of light emissions proportional to a weight value of a video data is progressed to display a grey scale.
As an example, referring to
FIG. 3
, when a picture of 8 bit data is displayed in 256 grey scales, one frame display duration (for an example, {fraction (1/60)} seconds=approx. 16.7 msec) of each discharge cell
1
is divided into 8 sub-fields (SF
1
-SF
8
).
Each of the sub-fields (SF
1
-SF
8
) is again divided into a reset duration, an addressing duration, and a sustain duration, and each sustain duration of the sub-fields (SF
1
-SF
8
) has a time weight variably given in a ratio of 2
N
(where N=
0, 1, 2, 3, - - - , 7
). That is, time weights in a ratio of 1:2:4:8:16:32:64:128 are given to the sub-fields SF
1
-SF
8
starting from a first sub field SF
1
to an eighth sub-field SF
8
.
FIG. 4
illustrates operation waveforms applied to respective electrodes in each sub field in FIG.
3
.
Referring to
FIG. 4
, each of the sub fields in the related art PDP is operated, with the sub field divided into a reset duration, addressing duration, a sustain duration, and an erasure duration.
The reset duration is a duration for initializing the discharge cell. The address duration is a duration for making a selective address discharge according to a logical value of the video data. The sustain duration is a duration for sustaining an address discharge in a discharge cell. The erasure duration is a duration for erasing all discharges sustained in all the discharge cells.
In the erasure duration, a erasure pulse E is applied to the common sustain electrode Z, to erase the sustain discharge.
In the reset duration, a reset pulse RP is applied to the scan electrode Y to cause reset discharge at all discharge cells. Once, the reset discharge is occurred at all discharge cells, all the discharge cells are initialized.
In the addressing duration, a scan pulse SP is applied to the scan electrodes Y in succession, and a data pulse DP synchronous to the scan pulse SP is applied to the address electrodes X. In this instance, in the discharge cells having the scan pulse SP and the data pulse DP applied thereto, address discharges are occurred.
In the sustain duration, a sustain pulse SUSP
1
or SUSP
2
is applied to the scan electrodes Y and the common sustain electrodes Z, alternately. Upon application of the sustain pulse SUSP
1
or SUSP
2
alternately, sustain discharge is occurred at the discharge cells the address discharge is occurred therein for a preset duration.
The sustain pulse SUSP
1
, or SUSP
2
has a pulse width in a range of approx. 2-3 &mgr;s. The sustain pulse S applied to the scan electrode Y at first has a pulse width in a range of 5 &mgr;s so as to cause the sustain discharge easily.
A number of the sustain pulses SUSP
1
, or SUSP
2
is increased for each sub field separately for displaying a picture in preset grey scales. For an example, the first sub field has two sustain pulses SUSP
1
or SUSP
2
, and the second sub field has four sustain pulses SUSP
1
or SUSP
2
. The third sub field has eight sustain pulses SUSP
1
or SUSP
2
. Thus, the related art PDP controls the number of sustain pulses SUSP
1
SUSP
2
, for meeting required grey scales.
In the meantime, referring to
FIG. 5
, for obtaining a stead distribution of optical waveforms, it is required that at least 5 sustain pulses SUSP
1
, or SUSP
2
are applied to the scan electrode Y and the common electrodes Z.
In more detail, an initial sustain pulse SUSP
1
or SUSP
2
causes a weak sustain discharge. Then, after an adequate wall charge is formed by several times of following sustain discharges, steady sustain discharges are occurred. Thus, the initial sustain discharge can not provide an adequate luminance.
Due to such discharge characteristics, sub fields that are required to display pictures in low grey scales can not obtain luminances consistent to the grey scales. In other words, the instable sustain discharge causes an erratic discharge in displaying a picture of a low grey scale.
Particularly, when an entire screen is displayed in low grey scales, the erratic discharge causes blinking of the screen, that deteriorates a picture quality. This blinking becomes the worse, as the addressing duration is the shorter, i.e., when the wall charge is not formed adequately during the addressing.
In the meantime, a high voltage may be applied in the addressing duration for prevention of the picture quality deterioration. That is, a voltage high in proportion to a reduction of the addressing duration may be applied for forming an adequate wall charge at the discharge cell. However, the application of the high voltage in the addressing duration requires a high voltage data drive IC (Integrated Circuit). Moreover, the high voltage data drive IC, not only consumes much power, but also high installation cost. In conclusion, what is required is a method for displaying a picture of lower grey scales while the voltage in the related art is kept.
SUMMARY OF THE INVENTION
Accordingly, the prese

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