Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
1999-09-24
2002-10-15
Saras, Steven (Department: 2675)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
C345S063000
Reexamination Certificate
active
06466186
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method and an apparatus for driving a plasma display panel, and more particularly to a method and an apparatus for driving a plasma display panel for realizing a high contrast information display terminal, flat television or the like by using a plasma display panel with high definition and large display capacity.
2. Description of the Related Art
Generally, a plasma display panel (referred to as PDP hereinafter) has a thin structure, is free from flickering and has a high display contrast ratio. Moreover, it has many features such as, that it can be made into a relatively large screen, a high response speed, is self-luminous and can be made multi-color luminous by the use of phosphors. Because of this, it has been used widely in recent years in the field of computer related display devices, in the field of color image display devices or the like.
According to the mode of operation, PDPs can be classified into two groups, namely, those of AC discharge type in which the electrodes are covered with a dielectric and is operated under the condition of indirect AC discharge, and those of DC discharge type in which the electrodes are exposed to the discharge space and is operated under the condition of DC discharge. The AC discharge type is further classified according to the driving method into memory operation type which utilizes the memory function of discharge cells and refresh operation type which does not utilize the function. The luminance of a PDP is proportional to the frequency of discharges, that is, the number of repetitions of the pulse voltage. In the refresh operation, type PDP, the luminance-falls off with the increase in the display capacity so that it is used mainly as a PDP of small display capacity.
FIG. 1
is a sectional view showing the configuration of one display cell of a PDP of the AC discharge memory operation type. The display cell is provided with a back face and a front face insulating substrates
1
and
2
made of glass, trace electrodes
5
and
6
which are arranged so as to overlap with a transparent scanning electrode
3
and a transparent sustaining electrode
4
formed on the insulating substrate
2
. A data electrode
7
formed on the insulating substrate
1
so as to intersect perpendicularly the scanning electrode
3
and the sustaining electrode
4
, a discharge gas space
8
formed between the insulating substrates
1
and
2
filled with a discharge gas such as He, Ne, or Xe or their mixture, barriers
9
for securing the discharge gas space
8
as well as for sectioning a display cell, a phosphor
11
for converting ultraviolet rays generated by the discharge gas into visible rays
10
, a dielectric film
12
covering the scanning electrode
3
and the sustaining electrode
4
, a protective film
13
made of magnesium oxide or the like for protecting the dielectric film
12
from the discharge, and a dielectric film
14
covering the data electrode
7
.
Next, referring to
FIG. 1
, the discharge operation of a selected display cell will be described. When discharge is initiated by applying a pulse voltage exceeding a discharge threshold between the scanning electrode
3
and the data electrode
7
, positive and negative charges are attracted to, and accumulated on, the surfaces of the dielectric films
12
and
14
on both sides, corresponding to the polarity of the pulse voltage. Since the equivalent internal voltage, namely, the wall voltage due to the accumulated charge has the polarity opposite to that of the pulse voltage, the effective voltage within the cell falls with the growth of the discharge. Accordingly, even if the pulse voltage is held at a constant level, it is unable to sustain the discharge, and eventually the discharge is ceased. After this happened, if a sustaining voltage which is a pulse voltage having the same polarity as that of the wall voltage is applied between adjacent scanning electrode
3
and the sustaining electrode
4
, the wall voltage component is superposed as an effective voltage to it, so it is possible to sustain discharge beyond the discharge threshold even when the voltage amplitude of the sustaining pulse is small. Consequently, it is possible to sustain the discharge by the continuous application of the sustaining pulse between the scanning electrode
3
and the sustaining electrode
4
. This is the memory function referred to in the above. The sustained discharge can be stopped by applying a broad low voltage pulse or a narrow erasing pulse, being a pulse comparable to the sustaining pulse voltage, capable of neutralizing the wall voltage between the scanning electrode
3
and the sustaining electrode
4
.
Next, referring to a block diagram in
FIG. 2
showing an example of the drive unit of the conventional PDP, the configuration of the PDP will be described. In the PDP, a sustaining electrode group
42
and a scanning electrode group
53
are provided mutually parallel on one surface, and a data electrode group
32
is provided in the direction perpendicular to these electrodes on the opposing surface. Display cells
22
are formed at the intersections of these arrays. The sustaining electrodes X are provided corresponding to respective scanning electrodes Y
1
, Y
2
, Y
3
, . . . , and Yn (n is an arbitrary positive integer) adjacent to them, and their respective one ends are connected in common.
Next, the configurations of plural kinds of driver circuit for driving the display cells
22
and a control circuit for controlling the driver circuits will be described. The drive unit is provided with a data driver
31
which drives one line portion of data of the data electrode group for the purpose of addressing discharge of the display cells
22
, sustaining driver circuit
40
which performs common sustaining discharge for the purpose of sustaining discharge of the display cells
22
, and a scanning driver circuit
50
which performs common sustaining discharge for the scanning electrode group
53
. The sustaining driver circuit
40
and the scanning driver circuit
50
are composed of lowimpedance circuits and high impedance circuits as illustrated in FIG.
3
. In addition, for the purpose of performing selective writing discharge during the addressing period, there is provided a scanning driver
55
which performs sequential scanning to the scanning electrodes Y
1
to Yn of the scanning electrode group. The scanning driver
55
performs sustaining discharge by applying a sustaining pulse to its own power supply by means of the scanning driver circuit
50
. A control circuit
61
controls all of the operations of the data driver
31
, sustaining driver circuit
40
, scanning driver circuit
50
, scanning driver
55
, and PDP
21
. The main part of the control circuit
61
comprises a display data control part
62
and a drive timing control part
63
. The display data control part
62
possesses a function of rearranging display data input from the outside to data for driving the PDP
21
, stores temporarily the rearranged display data stream, and transfers them to the data driver
31
as display data DATA in synchronism with the sequential scanning of the scanning driver
55
during addressing discharge. The drive timing control part
63
converts various kinds of signal such as dot clock signal input from the outside into internal control signals for driving the PDP
21
, and controls respective drivers and driver circuits.
Next, the drive sequence will be described.
FIG. 4
is a diagram showing the state of formation of a plurality of sub-fields in the conventional drive unit of the PDP. In this example, a field having a period of 16.7 ms is divided into 8 sub-fields (abbreviated as SFs). It is arranged so as to be able to display 256 gradations by regulating the drive sequence through the combination of these sub-fields. Each sub-field is divided into a scanning period for writing display data corresponding to the weight of the sub-field, and a sustaining discharge period for displaying display data de
Shimizu Masahiro
Wakabayashi Toshiro
Anyaso Uchendu O.
Saras Steven
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