Discharge device driving method

Details Discharge device driving method Discharge device driving method

1999-08-03

2002-09-24

Chauhan, Ulka J. (Department: 2674)

Computer graphics processing and selective visual display system

Plural physical display element control system

Display elements arranged in matrix

C345S067000, C345S068000

Reexamination Certificate

active

06456265

ABSTRACT:

TECHNICAL FIELD
The present invention relates to a discharge device driving method, and more particularly, to a method for improving the discharge process in a discharge device such as a plasma display panel.
BACKGROUND ART
A discharge device, which is driven by a pulse voltage, has at least one pair of electrodes and performs a discharge by applying the pulse voltage to at least one electrode. Examples of such discharge devices are a fluorescent lamp, a gas laser generator, a sulfur dioxide-removing O
3
generator, and a plasma display panel. Here we will focus on the discharge device of the plasm display panel.
There are generally two types of display—AC and DC. The DC plasma display panel uses electrodes exposed to a discharge space so that charges move directly between electrodes facing each other. On the other hand, in the AC plasma display panel, at least one of electrodes that face each other is surrounded by a dielectric, thereby preventing direct movement of charges between the electrodes. That is, as shown in
FIG. 1A
, the DC plasma display panel has a scanning electrode
2
formed on a frontal glass substrate
1
and an address electrode
5
formed on a rear glass substrate
6
, which are directly exposed to a discharge space
4
so that a charge can move directly between the electrodes. The AC plasma display panel, as shown in
FIG. 1B
, has a scanning electrode
2
and a common electrode
3
which are covered by a dielectric layer
7
, thus preventing direct charge movement between pairs of facing electrodes, that is, between the scanning electrode
2
and the address electrode
5
or between the scanning electrode
2
and the common electrode
3
.
There are two methods for driving the plasma display panels as constituted above, that is, DC and AC driving methods whose classification depends on whether the polarity of a voltage applied for discharge sustainment varies with time or not. Both DC and AC driving methods can be applied to the DC plasma display panel, while only the AC driving method is available for the AC plasma display panel.
FIG. 1A
illustrates a DC plasma display panel adopting a facing discharge structure, and
FIG. 1B
illustrates an AC plasma display panel adopting a surface discharge structure. As shown, the discharge space
4
is formed between the facing surfaces of the frontal glass substrate
1
and the rear glass substrate
6
. In the DC plasma display panel, the flow of electrons supplied from the address electrode
5
(i.e., cathode) is the main energy source for sustaining discharge since the scanning electrode
2
(i.e., anode) and the address electrode
5
are directly exposed to the discharge space
4
. In the AC plasma display panel, the scanning electrode
2
and the common electrode
3
are situated within the dielectric layer
7
, thus being electrically isolated from the discharge space. In this case, discharge is sustained by the well-known wall charge effects. An example of the AC plasma display panel adopting the surface discharge structure is disclosed in the U.S. Pat. No. 4,833,463 by AT&T.
Depending on the constitution of electrodes for discharge, the plasma display panels are grouped into a facing discharge structure or a surface discharge structure. These structures, in turn, are divided into a two-electrode structure, a three-electrode structure, and so on to facilitate discharge.
FIG. 2A
illustrates a facing discharge structure, and
FIG. 2B
illustrates a surface discharge structure. In the facing discharge structure, address discharge for selecting a pixel and a sustainment discharge for sustaining discharge in a discharge space formed by blockheads
8
occur between the scanning electrode
2
and the address electrode
5
. In the surface discharge structure, address discharge for selecting a pixel occurs between the address electrode
5
and the scanning electrode
2
which are orthogonal and face each other in the discharge space formed by the blockheads
8
, and the sustainment discharge for sustaining discharge occurs between the scanning electrode
2
and the common electrode
3
. The blockheads
8
act to form the discharge space and prevent crosstalk to adjacent pixels by blocking light generated during discharge.
For reliable operation of the plasma display panel as a color picture display, gray-scaling should be performed. Currently, a single field is divided into a plurality of sub-fields for time-share driving.
FIG. 3
is a diagram for explaining a gray-scaling method for an AC plasma display panel applied to products, which is well-known to those skilled in the art. In the gray scale displaying method for the AC plasma display panel, a single field is divided into four sub-fields for time-share driving. Here, each sub-field has an address period
9
and a discharge sustaining period
10
, and 2
4
(=16) gray scales can be displayed with these four sub-fields. That is, since the ratio of the discharge sustaining periods in a first through a fourth field is 1:2:4:8, sixteen gray scales can be attained by constituting the discharge sustaining periods as 0, 1(1T), 2(2T), 3(1T+2T), 4(4T), 5(1T+4T), 6(2T+4T), 7(1T+2T+4T), 8(8T), 9(1T+8T), 10(2T+8T), 11(3T+8T), 12(4T+8T), 13(1T+4T+8T), 14(2T+4T+8T), or 15(1T+2T+4T+8T). For example, to display a gray scale of 6 at an arbitrary pixel, only the second sub-field (2T) and the third sub-field (4T) are addressed, and to display a gray scale of 5, the first and fourth sub-fields should be addressed.
FIG. 4
shows the waveforms of signals applied to a generally used AC plasma display panel driving method, showing the timings of signals applied to an address electrode
11
, a scanning electrode
12
, and a common electrode
13
, respectively. In an erase period
14
, to -accurately display a gray scale, the operation of the next sub-field is activated by generating a weak discharge and thus a wall charge caused by the previous discharge is erased. During an address period
15
, discharge occurs only in a selected area, i.e., a pixel of the whole screen in the plasma display panel by selective discharge by means of a write pulse
17
between the address electrode
5
and the scanning electrode
2
which are orthogonal to each other. That is, image information converted into an electrical signal triggers each discharge of the addressed pixels. In a discharge sustaining period
16
, the image information is realized by sustaining the triggered discharge on a pixel, which is addressed on a real screen, by means of successive discharge sustaining pulses
18
.
In the plasma display panel driven by the above signals, it is well-known and empirically proven that luminescent efficiency increases using shorter pulses as the discharge sustaining voltage during a discharge sustaining period when driving the plasma display panel. This is because if a narrow pulse is used as the voltage applied during the discharge sustaining period, thermal and electrical loss is reduced and thus luminescent efficiency is increased.
FIG. 5
is a diagram explaining the discharge principle of an AC plasma display panel. Here, when the discharge sustaining pulse
18
having the discharge starting voltage
20
is applied, the wall charge
24
increases and thus the discharge voltage
25
drops. In the case of a normal discharge, discharge continues until a discharge extinguishing voltage
21
is reached, thus functioning to generate sufficient wall charge and controlling the distributions of wall and space charge densities to be favorable for the next discharge. However, as the discharge sustaining pulse
18
becomes narrower, a wall charge forming period
22
becomes very short. Thus; it is difficult to generate sufficient wall charge, and worse, a space charge controlling period
23
is absent; resulting in a complete loss of control of the wall and space charges after discharge is extinguished. In this case, to continue the discharge, the discharge starting voltage
20
should be very high, which makes adjacent

Affiliated with

Also associated with

Rating

Discharge device driving method does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Discharge device driving method, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Discharge device driving method will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2896118