Electric lamp and discharge devices: systems – Plural power supplies – Plural cathode and/or anode load device
Reexamination Certificate
2001-11-19
2003-03-25
Philogene, Haissa (Department: 2821)
Electric lamp and discharge devices: systems
Plural power supplies
Plural cathode and/or anode load device
C315S169400, C345S204000, C345S213000, C345S214000
Reexamination Certificate
active
06538389
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to plasma display apparatuses, and particularly relates to a plasma display apparatus that has an improved display quality.
2. Description of the Related Art
Plasma display panels have two glass plates on which electrodes are formed, and discharge-purpose gas fills the gap between the two glass plates that is in the order of 100 microns. Voltages higher than a discharge threshold voltage are applied between the electrodes to start gas discharge, and ultraviolet light generated from the discharge induces the light emission of photo florescent provided on the plate, thereby effecting screen displaying.
FIG. 1
is a diagram showing a schematic configuration of a plasma display apparatus.
A display panel
10
includes X electrodes
11
and Y electrodes
12
disposed in parallel, and further includes address electrodes
13
disposed in perpendicular thereto. The X electrodes
11
and the Y electrodes
12
are used to provide sustain discharge for display-purpose light emission. Voltage pulses are applied between the X electrodes
11
and the Y electrodes
12
, thereby carrying out sustain discharge. Further, the Y electrodes
12
serve as scan-purpose electrodes for writing display data. The address electrodes
13
are used to select display cells
15
that are to emit light. A voltage for writing discharge is applied between the Y electrodes
12
and the address electrodes
13
so as to select discharge cells. Shields
14
are provided between the address electrodes
13
for the purpose of separating the discharge cells
15
.
Discharge of a plasma display panel can only assume either one of the “on” state and the “off” state, so that the density, i.e., the gray scale, is represented by the number of repeated light emissions. To this end, a frame is divided into 10 sub-fields, for example. Each sub-field is comprised of a reset period, an address period, and a sustain discharge period. During the reset period, all cells are equally initialized regardless of lighting status in the previous sub-fields, e.g., are placed in the condition in which wall charge is erased. During the address period, selective discharge (addressing discharge) is performed to select the on/off states of cells in accordance with display data, thereby selectively generating wall charge that places cells in the “on” state. During the sustain discharge period, discharge is repeated in the cells where addressing discharge was performed to generate wall discharge, thereby emitting light. The length of the sustain discharge period, i.e., the number of repeated light emissions, differs from sub-field to sub-field. For example, ratios of the numbers of light emissions from the first sub-field to the tenth sub-field are set to 1:2:4:8: . . . :512, respectively. Sub-fields are then selected in accordance with the luminance level of a display cell to be subjected to gas discharge, thereby achieving a desired gray scale level.
FIG. 2
is a drawing showing another configuration of a display panel unit different from that of FIG.
1
.
In a display panel unit
10
A of
FIG. 2
, X electrodes
11
A and Y electrodes
12
A serving as display electrodes are provided in turn at equal intervals so as to cross address electrodes
13
A. All gaps between the electrodes are utilized as display lines (L
1
, L
2
, . . . ). This configuration is called an ALIS (alternate lightning of surfaces) method, and is disclosed in Japanese Patent No. 2801893. Since all the gaps between the electrodes are utilized as display lines, the number of electrodes is half as many as that of
FIG. 2
, which provides a basis for a cost reduction and a scale reduction.
Since all the gaps between electrodes serve as display lines in the ALIS method, it is impossible to light up all the display lines simultaneously. Lighting of odd-number lines (L
1
, L
3
, . . . ) and even-number lines (L
2
, L
4
, . . . ) are temporally separated to effect displaying. In the ALIS method, One frame is divided into two fields, each of which is comprised of a plurality of sub-fields. The first field is used for the displaying of odd-number lines, and the second field is used for the displaying of even-number lines.
FIG. 3
is a drawing showing a configuration of a related-art plasma display apparatus.
The plasma display apparatus of
FIG. 3
includes a plasma display panel
20
, a Y electrode drive circuit
21
, an X electrode drive circuit
22
, an address electrode drive circuit
23
, a discrimination decision circuit
24
, a memory
25
, a control circuit
26
, and a scanning circuit
27
.
A vertical synchronizing signal Vsync, a horizontal synchronizing signal Hsync, a clock signal Clock, and RGB signals each comprised of 8 bits and serving as data signals are supplied to the discrimination decision circuit
24
. The discrimination decision circuit
24
writes RGB data in the memory
25
as display data in response to the vertical synchronizing signal Vsync. The control circuit
26
controls the Y electrode drive circuit
21
, the X electrode drive circuit
22
, the address electrode drive circuit
23
, and the scanning circuit
27
, and displays the display data stored in the memory
25
on the plasma display panel
20
. In conjunction with this, the scanning circuit
27
scans the Y electrodes Y
1
through Yn, and the address electrode drive circuit
23
drives the address electrodes A
1
through An, thereby together effecting writing electric discharge for writing data in the plasma display panel
20
. In the display cells where data were written, further, sustain electric discharge is generated between the Y electrodes Y
1
through Yn and the X electrodes X
1
through Xn by the Y electrode drive circuit
21
and the X electrode drive circuit
22
.
In the related-art configuration shown in
FIG. 3
, lines y
1
through yn that extends from the Y electrode drive circuit
21
to the scanning circuit
27
to be connected to the Y electrodes Y
1
through Yn take different wiring paths between the Y electrode drive circuit
21
and the scanning circuit
27
, so that they have different wire lengths. In the example of
FIG. 3
, similarly, the X electrodes X
1
through Xn extending from the X electrode drive circuit
22
to the plasma display panel
20
take different wiring paths to have different wire lengths. The line y
1
and the Y electrode Y
1
connected thereto both having long wiring lengths have wiring resistance and wiring inductance larger than those of the line y
3
and the Y electrode Y
3
connected thereto both having relatively short wiring lengths. By the same token, the X electrode X
1
having a long wiring length has wiring resistance and wiring inductance larger than those of the X electrode X
3
having a relatively short wiring length. An effect of the wiring inductance is especially strong. Because of this, when an electric current runs through wiring lines and electrodes to generate electric discharge between the Y electrodes Y
1
through Yn and the X electrodes X
1
through Xn, a voltage drop occurs along the wiring lines and electrodes. The voltage drop generated in this manner differs from wiring line to wiring line and from electrode to electrode.
As a result of this voltage drop, when a sufficient margin cannot be secured for the discharge voltage of a plasma display panel with respect to the electrodes having a large voltage drop, a sufficient voltage required to light up an electric discharge may not be supplied. In such a case, a flicker of a screen or the like will appear, thereby degrading display quality.
Accordingly, the present invention is aimed at providing a plasma display panel in which a voltage drop produced in accordance with a wire length is reduced. Moreover, the present invention is aimed at providing a plasma display panel in which a variation in voltage drops produced according to wire lengths is reduced, thereby improving the quality of images.
SUMMARY OF THE INVENTION
It is a general object of the present invention to provide a plasma dis
Awata Yoshimasa
Kuwahara Takeshi
Nakamura Takayoshi
Ohno Taizo
Ohsawa Michitaka
Hitachi , Ltd.
Philogene Haissa
Staas & Halsey , LLP
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