Electric lamp and discharge devices: systems – Plural power supplies – Plural cathode and/or anode load device
Reexamination Certificate
2002-11-27
2004-02-17
Vu, David Hung (Department: 2821)
Electric lamp and discharge devices: systems
Plural power supplies
Plural cathode and/or anode load device
C345S067000, C345S068000
Reexamination Certificate
active
06693389
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to plasma display panels (PDPs), and more particularly, to an electronic waveform technique that minimizes vertical crosstalk in a PDP.
2. Background of the Art
Color PDPs are well known.
FIG. 1
illustrates a prior art embodiment of a color alternating current (AC) PDP, as disclosed in U.S. Pat. No. 6,118,214 to Marcotte (hereinafter “the Marcotte '214 patent”), which is incorporated herein by reference. Transparent electrodes
11
are employed on a front panel. A front plate (not shown) includes horizontal plural pairs of sustain electrodes
10
that connect transparent electrodes
11
to a sustain bus
12
. A plurality of pairs of scan electrodes
14
are juxtaposed to paired sustain electrodes
10
, and both electrode sets are covered by a dielectric layer (not shown) and a magnesium oxide (MgO) layer (not shown). A back plate (not shown) supports vertical barrier ribs
16
and plural vertical column electrodes
18
(shown in phantom). Individual column electrodes
18
are covered with red, green, or blue (RGB) phosphors, as the case may be, to enable a full color display to be achieved. The front and rear plates are sealed together and a space therebetween is filled with a dischargeable gas.
An electrode pair is defined as (a) a sustain electrode
10
(and its adjacent transparent electrode
11
) juxtaposed with (b) a scan electrode
14
(and its adjacent transparent electrode
11
). A pixel
20
is defined as an area that includes intersections of (i) an electrode pair of sustain electrode
10
and scan electrode
14
on the front panel, and (ii) three column electrodes
18
for red, green, and blue, respectively, on the back panel. A subpixel corresponds to an intersection of a red, green or blue column electrode with an electrode pair of a sustain electrode and a scan electrode. For example, subpixel
19
corresponds to an intersection of a red column electrode
18
with an electrode pair of sustain electrode
10
and scan electrode
14
.
Operating voltage and power of the PDP are controlled by a discharge gap
13
and a width of transparent electrode
11
. The operating voltage of the PDP is controlled by the distance across the discharge gap
13
, as the distance controls the breakdown voltage for a given gas mixture. Furthermore, sufficient voltage must be applied so that the ensuing gas discharge plasma is able to fully engulf the scan and sustain electrode pair. The power consumed by the discharge is affected by the surface capacitance of the electrode pair, which is proportional to electrode area and inversely proportional to the dielectric thickness.
A width of sustain electrode
10
and a width of scan electrode
14
are chosen to produce a narrow discharge gap
13
and a wide inter-pixel gap
15
. When sufficient voltage is applied across discharge gap
13
, the gas will break down forming a discharge plasma. For a given applied voltage, the positively charged electrode is the anode and the negatively charged electrode is the cathode. The discharge plasma has two distinct regions, the positive column and the negative glow. The positive column consists predominantly of fast moving electrons seeking the positive charge on the surface of the anode electrode. Conversely, the negative glow contains slow moving ions drifting toward and across the negatively charged cathode electrode. The duration of the discharge is limited by the amount of charge on the dielectric surfaces. Once the charge has been neutralized the discharge self-extinguishes. Within a sustain time period, this process is repeated by alternating the voltage polarity after each discharge completes. Inter-pixel gap
15
must be made sufficiently large to prevent the energetic positive column of the plasma discharge from bridging the inter-pixel gap and corrupting an ON or OFF state of an adjacent pixel. The width of the transparent electrode
11
and the thickness of a dielectric glass (not shown) over the electrode determine the pixel's discharge capacitance, which controls the discharge power and therefore brightness. For a given discharge power/brightness, a number of discharges is chosen within sustain time periods to provide gray scales which sum to meet the overall brightness requirement for the panel.
FIG. 2
shows a typical prior art block diagram of a PDP system
200
. An analog video signal is input into logic
230
where the signal is digitized, processed, and temporarily stored. Once a frame's worth of data is stored, logic
230
begins a process of displaying data through a series of subfields, typically 8 to 12, as disclosed in U.S. Pat. No. 5,724,054 to Shinoda.
FIG. 3
is a graph showing a division of a frame time into 8 subfields (i.e., SF1-SF8). During each addressing period lines Y
1
through Y
480
are scanned sequentially by row drivers
210
, while video input is applied through column drivers
225
to set each sub-pixel in the ON state as required by the video input. Each subsequent sustain period is weighted with sustain pulses to achieve weighted light intensities for each subfield.
FIG. 4
shows a typical division of a subfield. Each subfield has a setup period, an addressing period, and a sustain period. The setup period turns off any ON pixels, primes the MgO layer, and sets up all the pixels for addressing. Referring to both FIG.
2
and
FIG. 4
, during the addressing period, a scan generator
205
, in conjunction with row drivers
210
, sequentially drives each row low for addressing. Once a given row is enabled, logic
230
loads column drivers
225
with image data corresponding to individual RGB sub-pixels requiring illumination based upon received image data. Column drivers
225
apply voltage Vx to selected column electrodes. The coincidence of a selected row and an applied column voltage initiates a weak discharge that cascades into a discharge between the selected scan electrode and its neighboring sustain electrode. Once completed, the discharge has placed the addressed sub-pixel in the ON state. Any column not driven will remain in the OFF state. While the addressing discharge does produce visible light, it is not of sufficient brightness to represent the image properly. Consequently, a sustain period follows the addressing period after the last row has been addressed. During the sustain period, scan generator
205
and a sustain generator
220
supply alternating sustain pulses so that a momentary ac-plasma discharge occurs on an application of each pulse. Each sustain discharge produces ultra violet light the excites surrounding phosphor to produce visible light. Each subfield within a frame contains a sufficient number of sustain pulses and in-turn discharges to achieve a desired brightness for each subfield. Since each sub-pixel can be addressed independently in each subfield, a large color palate is obtainable.
FIG. 5
a
shows a prior art composite waveform between the scan and sustain electrodes. Due to a capacitive relationship of the scan and sustain electrodes, the composite waveform is simply an output of scan generator
205
(
FIG. 4
Scan waveform), minus an output of sustain generator
220
(
FIG. 4
Sustain waveform). Note that applied data pulses are not included in
FIG. 5
a.
FIGS. 5
b
-
5
e
show wall voltage waveforms for each pixel addressing sequence. A wall voltage is an AC coupled voltage present on a gas side of a dielectric layer. The wall voltage is limited, positive and negative, by a breakdown voltage of the gas, Vbr and −Vbr.
When the breakdown voltage is exceeded in either direction, two types of discharges can occur, a well-known negative resistance discharge and a more recently discovered positive resistance discharge. According to U.S. Pat. No. 5,745,086 to Weber, and referring to
FIG. 4
, if an applied waveform rises or falls slowly, as in rising and falling ramps of the setup period t
12
and t
15
, the gas will discharge having a positive resistance characteristic, behaving much like a zener diode limiting the voltage ac
Isobe Norifusa
Marcotte Robert G.
Matsushita Electric - Industrial Co., Ltd.
Ohlandt Greeley Ruggiero & Perle LLP
Vu David Hung
LandOfFree
Suppression of vertical crosstalk in a plasma display panel does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Suppression of vertical crosstalk in a plasma display panel, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Suppression of vertical crosstalk in a plasma display panel will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3301004