Computer graphics processing and selective visual display system – Display driving control circuitry – Controlling the condition of display elements
Reexamination Certificate
1998-09-11
2002-07-30
Shalwala, Bipin (Department: 2673)
Computer graphics processing and selective visual display system
Display driving control circuitry
Controlling the condition of display elements
C345S055000
Reexamination Certificate
active
06426744
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a display driving apparatus, and particularly to a display driving apparatus having a variable driving ability.
2. Related Art
FIG. 1
shows a general configuration of the conventional liquid crystal driving apparatus. As shown in
FIG. 1
, the conventional liquid crystal driving apparatus has a liquid crystal display
11
, a source driver
12
made up of several drive units
12
1
to
12
n,
each driving corresponding source electrodes in the liquid crystal display
11
, and a gate driver
13
made up of several drive units
13
1
to
13
n
, each driving units
13
1
to
13
n
driving gate electrodes in the liquid crystal display
11
.
When a drive current is applied to the liquid crystal display
11
from one of the drive units
12
1
to
12
n
, while also applying a drive voltage from one of the drive units
13
1
to
13
n
, a corresponding pixel on the intersection of the applied drive current and the applied drive voltage will be activated.
FIG. 2
shows an equivalent circuit to the liquid crystal display
11
, as an example. As shown in
FIG. 2
, the equivalent circuit is comprised of resistors R and capacitors C. Note that inductors (not shown) are also included in the liquid crystal display
11
in
FIG. 2. A
row of the liquid crystal display
11
is driven by a amplifier
14
prepared in the end of a source driver
12
.
However, in the structure described earlier there are the following problems: the larger the liquid crystal display
11
becomes, the heavier its load becomes. In addition, the load of the liquid crystal display
11
may be uneven due to an error in its manufacturing process. A ringing noise may occur on the line of the liquid crystal display due to the negative characteristic of the amplifier
14
(e.g., caused by the feed back loop in the amplifier's structure) and the structure of the equivalent circuit shown in FIG.
2
. This potential ringing noise cannot be prevented as long as the driving performance of the amplifier
14
is fixed and not flexibly changed in accordance with its error. Furthermore, when the liquid crystal display has a low amount of load to the drive performance of the amplifier
14
, overshoot and undershoot noises may appear on the line driven by the amplifier
14
. The ringing, overshoot, and undershoot noises cause an image degradation on the liquid crystal display.
SUMMARY OF THE INVENTION
Accordingly, an objection of the present invention is to provide a display driving apparatus and a display system which will effectively prevent the image degradation from occurring.
According to an aspect of the present invention, a display driving apparatus is provided, comprising: variable-resistor means through which a current is supplied for a data line of a display; and a selection means for selecting a resistance of the variable-resistor means. As an example, the variable-resistor means can be realized using analog switches S
1
and S
2
shown in
FIG. 3
, while the selection means can be realized by a selection circuit shown in the same.
According to another aspect of the present invention, the display driving apparatus further comprises current changing means for changing the aforementioned current. The current changing means can be realized with the combination of circuits
21
to
24
, and a bias circuit
3
shown in FIG.
3
.
According to yet another aspect of the present invention, a display system is provided, comprising: display means, comprised of a plurality of scanning lines and data lines, and a plurality of pixel cells(transistors) placed on the intersections of the plurality of scanning lines and the plurality of data lines, for displaying an image; data line driving means comprised of a plurality of source drivers, each driving each corresponding data line in the display means, wherein each source driver comprises variable-resistor means through which a current is supplied for each data line in the display means, and a selection means selecting a resistance of the variable-resistor means; and scanning line driving means for driving each scanning line in the display means. An exemplary structure of the display system is shown in FIG.
9
. In this exemplary structure the display means corresponds to a display panel
1100
; the data line driving means corresponds to the combination of a source driver
1200
and a port-A
1700
; and the scanning line driving means corresponds to the combination of a gate driver
1300
, an AND gate
1500
, and a port-B
1600
.
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Korean Office Action dated Sep. 27, 2000, with Japanese translation and partial English translation.
Abe Katsumi
Hashimoto Yoshiharu
Yamamoto Keiichi
McGinn & Gibb PLLC
NEC Corporation
Piziali Jeff
Shalwala Bipin
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