Electricity: power supply or regulation systems – In shunt with source or load – Using a three or more terminal semiconductive device
Reexamination Certificate
2001-03-21
2002-04-02
Berhane, Adolf Deneke (Department: 2838)
Electricity: power supply or regulation systems
In shunt with source or load
Using a three or more terminal semiconductive device
C323S271000, C327S111000
Reexamination Certificate
active
06366063
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a circuit and method for driving a capacitive load and, more particularly, to a driving circuit and driving method for a capacitive load suitable to drive a load that has a capacitance like an electrode of a dot matrix type display panel such as a plasma display panel and an EL display panel.
2. Description of the Related Art
In recent years, the need for a large-screen display device greater in size than a 40-inch type (102 cm diagonal) has risen as a process of improving a display device. This achievement will be difficult if such a large screen display device is constructed with a CRT (cathode ray tube). The reason is that its volume, weight, operating voltage, etc., becomes very large. Accordingly, a projection type display device and a reflection type display device have come into practical use as such large screen display devices. However, they are fundamentally inferior in display brightness, visual angle, color reproducibility, and depth, and have difficulty in following recent trends to construct a display device in the form of a flat panel and to realize a lightweight display device. In order to answer the marketing needs, demands have been made to develop and commercialize a self-luminous type large-screen plasma display device that has a flat display surface, that is light in weight, that is thin in depth, and that is excellent in visibility, such as the visual angle and color reproducibility. The rapid spread of the device is expected.
The plasma display device is made up of a panel portion (hereinafter designated simply as “panel” or in detail as “plasma display panel”) for displaying an image by the use of a luminous discharge phenomenon and a driving circuit portion for driving this panel. According to differences in the discharge type, plasma display devices are classified into DC discharge types and an AC discharge types, and, according to differences in the electrode structure, they are classified into surface discharge types, opposition discharge types, two-electrode types, three-electrode types, etc. Among these types, the DC discharge type display device is constructed such that electrodes are exposed directly to a discharge space and, once an electric discharge occurs, a DC electric current continues running. By contrast, the AC discharge type display device is constructed such that an insulating layer lies between electrodes and a discharge gas, and therefore an electric current is restricted by the electrostatic capacity of the insulating layer, and, after a voltage is applied, the current runs for a short time of about one microsecond like a pulse and stops running. Since the insulating layer serves as a condenser, the AC discharge type display device repeats light emission and displays images by applying a bipolar AC pulse voltage to one of the electrodes or by alternately applying a pulse to both the electrodes.
The DC type display device is at a disadvantage in that, in spite of its simple structure, the electrodes deteriorate so significantly that the display device cannot maintain its long life because the electrodes are exposed directly to a discharge space on the other hand, the AC type display device is a t an advantage in t hat the lifetime thereof is long because the electrodes are covered with the insulating layer.
After all, these days, a method in which a surface discharge type plasma panel is allowed to undergo AC driving while separating a scanning electrode and a sustaining electrode from each other by the use of three kinds of electrodes is chiefly used among various plasma display methods that have been proposed until now. The reason is that, at the present time, this method is excellent in durability, is simple in structure, is relatively easy to aim at high definition/screen enlargement, and, in addition, is capable of easily realizing a luminescence maintaining function, called memory, that enables high-luminance light emission.
In any type, the plasma display panel is made up of two substrates facing each other, i.e., a front transparent substrate and a back substrate, a discharge gas space in which discharge gas, such as He—Xe or Ne—Xe, is filled and display cells are arranged in a matrix form at a gap between the substrates, and various stripe-shaped electrodes arranged perpendicularly to each other on each inner surface of the front transparent substrate and the back substrate. Electrodes on the side of the front transparent substrate and electrodes on the side of the back substrate are arranged to intersect at the position of each display cell.
Next, a description will be provided of a three-electrode surface discharge type panel structure as a representative of a plasma display panel of AC driving.
FIG. 1
is an exploded perspective view that separately shows the structure of a plasma display panel of the three-electrode surface discharge type,
FIG. 2
is a cross-sectional view of the panel,
FIG. 3
is an enlarged sectional view that shows a part of the panel by further enlarging it,
FIG. 4
is a plan view that shows the electrode structure of the panel, and
FIG. 5
is a plan view that shows the display cell structure of the panel.
As shown in
FIGS. 1
to
5
, in a panel
1
of the three-electrode surface discharge type, three kinds of display cells Cr, Cg, and Cb are disposed on the inner surface of a front transparent substrate
2
. The display cells Cr, Cg, and Cb serve to produce the colors of red, green, and blue, respectively. The display cells Cr, Cg, and Cb are arranged in the direction of columns. The column of the display cell Cg is disposed next to the column of the display cell Cr, and the column of the display cell Cb is disposed next to the column of the display cell Cg. Thus, the column of the display cell Cr, the column of the display cell Cg, and the column of the display cell Cb are disposed repeatedly in the direction of rows. Further, in the plasma display panel, there are formed a lot of surface discharge electrode pairs that are made by pairs of a plurality of transparent scanning electrodes S
1
, S
2
, . . . (hereinafter designated generically as “scanning electrode S”) and a plurality of transparent sustaining electrodes Su
1
, Su
2
, . . . (hereinafter designated generically as “sustaining electrode Su”). The scanning electrode S and the sustaining electrode Su extend in the row wise direction. Each scanning electrode S and each sustaining electrode Su are disposed to pass through the display cells arranged in the row wise direction. The scanning electrode S (S
1
, S
2
, . . . ) and the sustaining electrode Su (Su
1
, Su
2
, . . . ) are each made of a transparent conductive thin film, such as ITO (Indium Tin Oxide) or SnO
2
. In order to supply a sufficient electric current to the scanning electrode S and the sustaining electrode Su, a bus electrode B made of, for example, a silver thick film is disposed at one side end of the surface of each of the scanning electrode S and the sustaining electrode Su. The surfaces of the scanning electrode S and the sustaining electrode Su that are each provided with the bus electrode B are covered with a transparent dielectric layer
3
. An MgO protective layer
4
to protect the dielectric layer
3
from ion bombardment during a discharge is further placed on the transparent dielectric layer
3
.
On the inner surface of the back substrate
6
, stripe-shaped partitions
7
are disposed between columns that are constructed of the display cells. The partitions
7
define a stripe-shaped discharge gas space that divides the columns of the display cells and extends in the column wise direction. A plurality of data electrodes (column electrodes) D
1
, D
2
. . . (hereinafter designated generically as “data electrode D”) are further disposed on the plasma display panel. The data electrode D extends in the column wise direction. Each data electrode D is disposed to pass through each of the columns of the display cells Cr, Cg, and Cb arranged in the column wise direction. A dielectric lay
Berhane Adolf Deneke
Hayes, Soloway, Hennessey Grossman & Hage, P.C.
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