Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
1999-07-02
2002-02-05
Jankus, Almis R. (Department: 2675)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
C345S067000, C345S068000, C315S169400
Reexamination Certificate
active
06344841
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a flat panel display device, and more particularly to a method of driving a plasma display panel(PDP) for displaying a picture and an apparatus thereof.
2. Description of the Related Art
Nowadays, there have been actively developed a flat panel display device such as a liquid crystal display(LCD) device, a field emission display device, a plasma display device and so on. The flat panel display device displaying a picture making use of a discharge has been highlighted due to its simple structure and the easiness in manufacturing it. Also, the plasma display device provides a high brightness, a high radiation efficiency, an improved memory ability and a wide view angle of more than 16°. Furthermore, the plasma display device has an advantage in that it can implement a large screen of more than 40 inches. Such a plasma display device is classified into a direct current(DC) system and an alternating current(AC) system depending on a discharge generation type. The alternating current system of plasma display device has been noticed because a consumption power is low and a lifetime is long compared with the direct current system.
Since the plasma display device has a characteristic in that its brightness becomes different in accordance with a discharge time of each cell, it must control a discharge time of each pixel in one field interval(e.g., 16.67 ms in the case of an image signal of NTSC system) of a single image signal so as to display a moving picture having a gray scale. The driving apparatus of AC system displaying a picture depending on the discharge interval includes a plasma display panel(PDP) driving apparatus as shown in FIG.
1
. The PDP driving apparatus of
FIG. 1
includes a scanning/sustaining electrode driver
2
, a common sustaining electrode driver
4
and first and second address electrode drivers
6
A and
6
B, which are connected to a PDP
8
. The PDP
8
is provided with scanning/sustaining electrodes Y
1
to Yn and common sustaining electrodes Z
1
to Zn which are alternately arranged in the vertical direction, and address electrodes X
1
to Xm arranged, in parallel, in the horizontal direction. In the PDP
8
, mxn pixels are formed in a matrix pattern in such a manner to be connected to the scanning/sustaining electrodes(Y), the common sustaining electrodes(Z) and the address electrodes (X). The scanning/sustaining electrode driver
2
allows pixels to be discharged to be sequentially selected in the line unit and a discharge in each of the mxn pixels to be sustained. To this end, as shown in
FIG. 2
, the scanning/sustaining electrode driver
2
performs a reset operation for make a uniformity of the cells by a writing and erasing operation on the entire cells, an addressing operation of allowing the pixels to selectively initiate a discharge, and a sustaining operation of allowing a discharge of the pixels to be sustained. The scanning/sustaining electrode driver
2
applies writing and erasing pulses to the scanning/sustaining electrodes Y
1
to Yn in a reset interval, applies a scanning pulse to the scanning/sustaining electrodes Y
1
to Yn sequentially in an addressing interval, and applies a sustaining pulse to the scanning/sustaining electrodes Y
1
to Yn in a sustaining interval. Also, the scanning/sustaining electrode driver
2
may additionally supplies a writing pulse to the scanning/sustaining electrodes Y
1
to Yn in the reset interval to form a wall charge at each of the mxn pixels. The common sustaining electrode driver
4
applies a predetermined level of voltage signal to all the common sustaining electrodes Z
1
to Zn. The first and second address electrode drivers
6
A and
6
B supply an image data to the address electrodes X
1
to Xm in the PDP
8
in such a manner that the image data is synchronized with the scanning pulse. The first address electrode driver
6
A supplies an image data to odd-numbered address electrodes X
1
, X
3
, . . . , Xm-
3
, Xm-
1
while the second address electrode driver
6
B supplies an image data to even-numbered address electrodes X
2
, X
4
, . . . , Xm-
2
, Xm.
Further, the plasma display device controls a light quantity depending on the discharge time to realize a gray level. In other words, in the plasma display device, the discharge time is controlled such that a contrast and a chromaticity of the picture become different. To this end, as the plasma display device of AC system is used a PDP driving technique of address display separated (ADS) system. In this PDP driving technique of ADS system, a single field is divided into a number of sub-fields in accordance with a gray level intended to be implemented, and each sub-field is divided into an addressing interval and a sustaining interval to drive the PDP
8
. For instance, when it is intended to realize
256
gray levels, a field interval corresponding to {fraction (1/60)} second is divided into
8
sub-fields SF
1
to SF
8
as shown in FIG.
3
. Also, each of the
8
sub-fields SF
1
to SF
8
is again divided into an addressing interval and a sustaining interval. Each of pixels selected in the addressing interval indicated by oblique lines in
FIG. 3
initiates a discharge. The discharge initiated at each of the selected pixels is sustained in a sustaining interval. The sustaining interval is lengthened by a interval corresponding to 2
n
depending on a weighting value of each sub-field. In other words, the sustaining interval involved in each of first to eighth sub-fields increases at a ratio of 2
0
, 2
1
, 2
3
, 2
4
, 2
5
, 2
6
and 2
7
. To this end, the number of sustaining pulses generated in the sustaining interval also increases into 2
0
, 2
1
, 2
3
, 2
4
, 2
5
, 2
6
and 2
7
in accordance with the sub-fields. A brightness and a chrominance in each pixel are determined in accordance with a combination of the sub-fields SF
1
to SF
8
.
In such PDP driving method of ADS system, a brightness of each pixel is determined by a sustaining interval. In other words, since the sustaining interval becomes more decreased as the address interval increases, a maximum value of the brightness displayed on the screen is lowered. For instance, it is assumed that one field interval of 16.67 ms is divided into 8 sub-fields(i.e., upon implementation of 256 gray scales) and a time of 3.6 &mgr;s is required to address a single pixel line. Also, assuming that 480 pixel lines has been formed in the PDP, when the scanning/sustaining electrodes Y
1
to Yn are driven with a single scanning/sustaining driver
2
to scan a screen, a time of “480×3 &mgr;s=1.44 &mgr;s” is required to scan the entire 480 lines sequentially for each sub-field, and an addressing interval of 1.44 &mgr;s×8=11.52 &mgr;s is required for each field interval. In other words, an addressing interval of 11.52 &mgr;s is required to scan 480 pixel lines during one field. Accordingly, only 5.15 ms equal to 30% of 16.67 ms which is a time assigned to one field, is assigned to the sustaining interval. Also, since a reset interval for allowing all the cells to be in the same state by eliminating an affect of previous discharge at the inner side of the cell every sub-field must be included, the sustaining interval is shortened into, for example, 20 to 25%. Furthermore, since the number of pixel lines becomes more increased as a resolution of the PDP is heightened, the sustaining interval is more shortened. Also, the sustaining interval is more and more shortened as the PDP has a larger scale screen. Due to this, the conventional PDP driving method fails to brighten a screen into more than the limit. In addition, the conventional PDP driving method can assure the brightness of screen sufficiently as a resolution of the PDP becomes high or a screen of the PDP becomes large.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a plasma display panel driving method and apparatus that can improve the brightness of screen into more than the limit.
In order to achieve these and
Awad Amr
Fleshner & Kim LLP
Jankus Almis R.
LG Electronics Inc.
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