AC plasma display device

Details AC plasma display device AC plasma display device

1999-07-28

2003-11-11

Bella, Matthew C. (Department: 2671)

Computer graphics processing and selective visual display system

Plural physical display element control system

Display elements arranged in matrix

C345S055000, C345S067000

Reexamination Certificate

active

06646624

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to an AC plasma display device and, in particular, to an electric circuit for use with the AC plasma display device.
BACKGROUND OF THE INVENTION
FIG. 9
shows a conventional drive circuit for use with an AC plasma display panel of an AC plasma display device. The AC plasma display panel (hereinafter referred to as “panel” as necessary), generally indicated by reference numeral 1, includes M data electrodes D
1-m
extending vertically and 2N pairs of sustain and scan electrodes, SUS
1-2N
and SCN
1-2N
, extending horizontally. The vertically extended data electrodes D
1-m
face to the horizontally extended sustain and scan electrodes, SUS
1-2N
and SCN
1-2N
, leaving a small space gap therebetween. The sustain and scan electrodes, SUS
1-2N
and SCN
1-2N
, are divided into two groups or blocks; the first group or block
2
including sustain and scan electrodes, SUS
1-N
and SCN
1-N
, and the second group or block
3
including sustain and scan electrodes, SUS
(N+1)-2N
and SCN
(N+1)-2N
.
The data electrodes D
1-M
are electrically connected with a data driver
4
having a pulse generator not shown for applying a drive signal or pulse voltage to each of the data electrodes D
1-M
. The sustain and scan electrodes, SUS
1-N
and SCN
1-N
, in the first group
2
are connected to sustain and scan drivers,
5
and
6
, respectively. On the other hand, the sustain and scan electrodes, SUS
(N+1)-2N
and SCN
(N+1)-2N
, in the second group
3
are connected to sustain and scan drivers,
7
and
8
, respectively.
The sustain drivers
5
and
7
include sustain/erase (S/E) pulse generators
9
and
10
, respectively. Also, the S/E pulse generator
9
is electrically connected at its output through an output line
11
with each of the sustain electrodes SUS
1-N
so that the pulse generator
9
applies a certain signal or pulse voltage to each of the sustain electrodes SUS
1-N
. Likewise, the S/E pulse generator
10
is electrically connected at its output through an output line
12
with each of the sustain electrodes SUS
(N+1)-2N
so that the pulse generator
10
applies a certain signal or pulse voltage to each of the sustain electrodes SUS
(N+1)-2N
.
The scan driver
6
includes a scan/sustain (S/S) pulse generator
13
and switching circuit
14
, and the scan driver
8
includes a S/S pulse generator
15
and switching circuit
16
. The S/S pulse generator
13
is electrically connected at its output through an output line
17
with the switching circuit
14
, which in turn connected with each of the scan electrodes SCN
1-N
. This allows the pulse generator
13
to apply a certain signal or pulse voltage to each of the scan electrodes SCN
1-N
. Likewise, the S/S pulse generator
15
is electrically connected at its output through an output line
18
with the switching circuit
16
, which in turn connected with each of the scan electrodes SCN
(N+1)-2N
. This allows the pulse generator
15
to apply a certain signal or pulse voltage to each of the scan electrodes SCN
(N+1)-2N
.
In operation of the AC plasma display panel so constructed, the data, sustain and scan electrodes are applied with respective pulses. A process for displaying an instant image in the panel includes three steps or periods; writing, sustaining and erasing periods. In the first writing period or step, the predetermined writing pulse or signal is sequentially applied to each of the scan electrodes SCN
1-2N
, during which another predetermined pulse voltage or signal is applied to selected one or more of the data electrodes D
1-M
, according to the image to be displayed. This induces an electric discharge at discharge cells or pixel cells formed adjacent to intersections of the scan and data electrodes and corresponding to the selected data electrodes.
In the next sustaining period, the sustain electrodes SUS
1-2N
are applied with the predetermined sustain pulse voltage or signal, thereby sustaining the discharge at each of the selected discharge cells or image pixels according to the display data.
Finally, in the last erasing period, the predetermined erase pulse voltage or signal is applied to the sustain electrodes SUS
1-2N
to erase the residual electric discharge.
In the writing period, the switching circuits
14
and
16
switch the pulse voltages transmitted from the S/S pulse generators
13
and
15
, respectively, so that the scan electrodes SCN
1-N
and SCN
(N+1)-2N
are applied with the predetermined pulse voltage in sequential order. Likewise, in the sustaining period, the predetermined pulse voltage transmitted from the S/S pulse generators
13
and
15
are applied to respective scan electrodes SCN
1-N
and SCN
(N+1)-2N
.
In the meantime, as best shown in
FIG. 10
, the conventional S/E pulse generators
9
and
10
, S/S pulse generators
13
and
15
, and the switching circuits
14
and
16
are mainly constructed with push-pull circuit of Field-Effect Transistors (FETs), for example. It should be noted that, for example, where a push-pull circuit is made of two FETs, X
1
and X
2
, it is indicated as “push-pull circuit X
1
/X
2
” hereinafter.
With the arrangement shown in
FIG. 10
, in the sustaining period, when FET(Q
2
) is kept off, the push-pull circuit Q
1
/Q
3
switches FET(Q
1
) and FET(Q
3
) alternately. Also, when the FET(Sa
1-N
) are turned on, FET(Sb
1-N
) off, and FET(T
3
) off, the push-pull circuit T
1
/T
2
switches FET(T
1
) and FET(T
2
) alternately, with a certain phase opposite to that of the push-pull circuit Q
1
/Q
3
. This allows a pulse voltage of −Vm volts to be applied to the sustain electrodes SCN
1-N
and scan electrodes SCN
1-N
alternately. Also, the sustain pulse voltage is applied to the sustain electrodes SUS
(N+1)-2N
in the same timing as the sustain electrodes SUS
1-N
, and to the scan electrodes SCN
(N+1)-2N
in the same timing as the SCN
1-N
.
In
FIG. 9
, suppose that a load for sustaining the discharge in a first region corresponding to the group
2
(upper half) is equal to that for sustaining the discharge in a second region corresponding to the group
3
(lower half). In other words, assume that an image is displayed in the whole area of the panel with a constant brightness. In this instance, an electric current flowing from the sustain electrodes SUS
1-N
to the S/E pulse generator
9
is equal to another electric current flowing from the sustain electrodes SUS
(N+1)-2N
to the S/E pulse generator
10
(i.e., Iua=Iub), and an electric current flowing from the scan electrodes SCN
1-N
to the S/S pulse generator
13
is equal to another electric current flowing from the scan electrodes SCN
(N+1)-2N
to the S/S pulse generator
15
(i.e., Ica=Icb).
It should be noted that the actual driver circuit includes resistance of lines and electric elements such as FETs. Therefor, the driver circuit is designed so that resistance from the power supply of −Vm volts for the S/E pulse generator
9
to the sustain electrodes SUS
1-N
is equal to that from the power supply for the S/E pulse generator
10
to the sustain electrodes SUS and a resistance from the power supply of −Vm volts for the S/S pulse generator
13
to the scan electrodes SCN
1-N
is equal to that from the power supply for the S/S pulse generator
15
to the scan electrodes SCN
(N+1)-2N
.
However, when displaying an image having its major part positioned in the first region (upper half) and its minor part positioned in the second region (lower half) with a constant brightness in its entire image area as shown in
FIG. 11
, in the sustaining period, the load for sustaining the discharge in the first region becomes greater than that in the second region. Therefore, the discharge current Iua flowing from the sustain electrodes SUS
1-N
to the S/E pulse generator
9
and the discharge current Ica flowing from the SCN
1-N
to the S/S pulse generator
13
become greater than the discharge current Iub from the sustain electrodes SUS
(N+1)-2N
to the S/E pu

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