Electric lamp and discharge devices: systems – Plural power supplies – Plural cathode and/or anode load device
Reexamination Certificate
2001-07-31
2003-09-16
Vu, David (Department: 2821)
Electric lamp and discharge devices: systems
Plural power supplies
Plural cathode and/or anode load device
C315S169400, C345S066000, C345S068000
Reexamination Certificate
active
06621229
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a plasma display panel and a driving method thereof.
2. Description of the Related Art
A plasma display panel includes two glass substrates having electrodes formed thereon, with a gap of about 100 microns therebetween that is filled with a discharge mixture gas containing Ne, Xe, or the like. A voltage that is equal to or greater than the break down voltage (of the discharge gas) is applied between the electrodes to cause a discharge giving a UV radiation, which excites and illuminates phosphors provided on the substrate, thereby displaying an image.
FIG. 7
is a diagram illustrating a general structure of a plasma display panel device.
On a display panel
10
, first electrodes (X electrodes)
11
and second electrodes (Y electrodes)
12
are formed so as to be disposed in parallel to each other. Third electrodes (address electrodes)
13
are formed so as to cross perpendicularly to the first and second electrodes. A first driving circuit
14
supplies a voltage pulse to the first electrodes
11
, a second driving circuit
15
supplies a voltage pulse to the second electrodes
12
, and a third driving circuit
16
supplies a voltage pulse to the third electrodes
13
. The first and second electrodes
11
and
12
, are provided to initiate a sustain discharge for display illumination. The sustain discharge occurs when the voltage pulse is applied repeatedly between the first and second electrodes
11
and
12
. In addition, one of the first and second electrodes
11
and
12
functions as a scan electrode (Y electrode) for writing display data. The third electrode
13
, on the other hand, is a electrode for selecting a display cell to be illuminated, and applies to a selected cell a voltage for initiating a writing discharge between the third electrode
13
and one of the first electrode
11
and second electrode
12
. The first, second and third driving circuits
14
,
15
and
16
are for generating voltage pulse relative to purposes of the first, second and third electrodes
11
,
12
and
13
.
FIG. 8
is a plan view illustrating a display panel portion of the device shown in FIG.
7
. The X electrode as the first electrode and the Y electrode as the second electrode are disposed parallel to each other. In this figure, electrodes for display lines L
1
to L
5
are shown. Moreover, the address electrode as the third electrode (A
1
to A
4
) and ribs
2
for dividing discharge cells are formed. The panel
10
has the X electrode and the Y electrode as display electrodes alternatively disposed at a constant interval so as to use all gaps between electrodes as display lines (L
1
, L
2
. . . ). Such method is called ALIS method (Alternate Lighting of Surfaces) and disclosed in Japanese Patent No. 2801893. Because all of the gaps between electrodes are used as the display line, a number of electrodes can be a half of that in a plasma display panel having a structure as shown in FIG.
14
. Therefore, it is an advantageous method in terms of cost reduction and higher definition.
FIG. 9
is a diagram illustrating a luminescence principle of a plasma display panel using the ALIS method. In the ALIS method, two display lines share one electrode, and thus, an upper line and a lower line sharing a common electrode cannot be illuminated at the same time. Therefore, similar to an interlaced display in a TV receiver, a display of odd-numbered lines (a first field) and a display of even-numbered lines (a second field) are done alternatively in a time-division manner.
FIG. 10
is a diagram illustrating a structure of sub-fields in a driving method of a plasma display panel using the ALIS method. As shown in the figure, one frame is composed of a first and a second fields dividing inside thereof. Moreover, each field is divided by a plurality of sub-fields. The plasma display panel is either discharged or not-discharged. Therefore, difference in brightness, i.e., gradation, is controlled by a number of discharges. For the above-mentioned reason, the frame includes a plurality of sub-fields each corresponding to a different number of discharges. Thus, by selectively discharging the sub-field to be illuminated according to the gradation, different brightness can be achieved. Generally, 8 to 12 sub-fields are provided.
Furthermore, each sub-field includes a reset period
21
, an address period
22
, and a sustain discharge period
23
(also called as a sustain period). The reset period
21
conducts an operation to reset all the cells in a uniform state, e.g., a state in which wall charge is eliminated, regardless of an illumination state of the previous sub-field. In order to decide ON/OFF state of the cell according to display data, the address period
22
selectively discharges (i.e., initiate an address discharge) to form the wall charge to put the cell in ON state. The sustain discharge period
23
emits predetermined light by repeating discharges in the cell in which the address discharge has occurred.
FIGS. 11A
to
11
E illustrate waveform diagrams of driving waveforms each being applied to each electrode in a plasma display panel employing the ALIS method.
FIG. 11A
shows a pulse supplied to the address electrode;
FIG. 11B
shows a pulse supplied to an X
1
electrode;
FIG. 11C
shows a pulse supplied to a Y
1
electrode;
FIG. 11D
shows a pulse supplied to an X
2
electrode; and
FIG. 11E
shows a pulse supplied to a Y
2
electrode. First, during the reset period, in order to eliminate an excessive wall charge of a cell that has been illuminated in the previous sub-field, a fine pulse −Vy of 1 &mgr;s and about −170V is applied to the Y electrode. With the pulse −Vy, excessive wall charges between the address electrode and the Y electrode are eliminated. Next, a pulse of about −120V (−Vwx) having a gentle gradient waveform is applied to the X electrode. With the pulse −Vwx, the wall charge is eliminated between the address electrode and the X electrode and between X and Y electrodes of the cell that has been illuminated in the previous sub-field and. Then, a writing pulse (Vw) of about 170V having a gentle gradient waveform is applied to the Y electrode. With the pulse Vw, a writing discharge occurs between the Y electrode and the address electrode, and between the Y electrode and the X electrode to form a certain degree of wall charge. In addition, while a voltage of about 90V (Vx) is applied to the X electrode, an elimination pulse (−Vey) of about −160V having a gentle gradient waveform is applied to the Y electrode. Thus, the wall charge formed the instant preceding thereof is eliminated, and some new wall charges having a reversed polarity are formed. Through all operations described above, all the cells become electrically uniform to be prepared for a next address period. The wall charge of the last phase of the reset period is such that a few positive charges are formed in the Y electrode and a few negative charges are formed in the X electrode. It should be understood that in the figure, Va represents an address pulse, −Vy represents a scan pulse, and Vs represents a sustain pulse.
According to the ALIS method, in odd-numbered fields, lines are illuminated between the X
1
-Y
1
electrodes, X
2
-Y
2
electrodes, X
3
-Y
3
electrodes and so on. In the even-numbered fields, lines are illuminated between Y
1
-X
2
electrodes, Y
2
-X
3
electrodes, Y
3
-X
4
electrodes and so on. Consequently, during the address period, the address pulse is applied to the address electrode, whereas in the address period of the odd-numbered field the scan pulse is applied to Y
1
, Y
2
. . . Yn electrodes. During the address period, in the even-numbered field, the scan pulse is applied to the X
2
, X
3
. . . Xn electrodes. During the sustain discharge period in the odd-numbered field, the sustain pulse is applied to X
1
-Y
1
electrodes, X
2
-Y
2
electrodes, X
3
-Y
3
electrodes, and so on, so that an addressed cell is illuminated. During the sustain discha
Ho Shirun
Kanazawa Yoshikazu
Suzuki Keizo
Hitachi , Ltd.
Mattingly Stanger & Malur, P.C.
Vu David
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