Electric lamp and discharge devices: systems – Plural power supplies – Plural cathode and/or anode load device
Reexamination Certificate
2001-06-19
2002-10-01
Wong, Don (Department: 2821)
Electric lamp and discharge devices: systems
Plural power supplies
Plural cathode and/or anode load device
C315S169200, C345S060000, C345S067000, C345S211000, C345S214000
Reexamination Certificate
active
06459212
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a plasma display apparatus including a plasma display panel.
2. Description of Related Art
In recent years, with the increase in screen size of display apparatuses, the demand for thin shape display devices is increasing and various kinds of thin display device have been put into the practical use. A plasma display panel of an alternating current discharge type has attracted much attention as one type of the thin shape display device.
FIG. 1
is a view schematically showing the construction of a plasma display apparatus equipped with such a plasma display panel.
In
FIG. 1
, PDP
10
as a plasma display panel is provided with m of column electrodes D
1
through D
m
and respective n of row electrodes X
1
through X
n
and row electrodes Y
1
through Y
n
aligned to intersect with the respective column electrodes. The row electrodes X
1
through X
n
and the row electrodes Y
1
through Y
n
, constitute a 1-th display line through an n-th display line in PDP
10
by respective pairs of row electrodes X
i
(1≦i≦n) and Y
i
(
1
≦i≦n). The PDP
10
is constructed in such a way that discharge spaces enclosing a discharge gas are formed between the column electrodes D and the row electrodes X and Y and discharge cells constituting pixels are formed. at intersecting portions of the respective row electrode pairs and the column electrodes including the discharge spaces.
In this case, the respective discharge cell has only two states of “light emission” and “no light emission”, since light is emitted by utilizing a discharge phenomenon. That is, the PDP
10
is capable of displaying only brightness of two gray scales of lowest brightness (non light emitting state) and highest brightness (light emitting state).
Hence, a driver
100
carries out a gray-scale drive using the subfield method for the PDP
10
in order to realize the display with halftone brightness in accordance with an inputted image signal.
According to the subfield method, an inputted image. signal is converted into, for example, corresponding 4 bit pixel data for each of the pixels. In correspondence respectively with the bit digits of the four bits, 1 field is constituted by four subfields SF
1
through SF
4
as shown in FIG.
2
.
FIG. 3
is a diagram showing various drive pulses applied by the driver
100
on the row electrodes and the column electrodes of PDP
10
and application timings thereof in one subfield.
First, at simultaneous resetting step Rc, the driver
100
applies reset pulses RP
X
having a positive polarity simultaneously to the respective row electrodes X
1
through X
n
and applies reset pulses RP
Y
having a negative polarity simultaneously to the respective row electrodes Y
1
through Y
n
as shown in FIG.
3
. In accordance with application of the reset pulses RP
X
and RP
Y
, all of the discharge cells of PDP
10
are discharged to reset. After finishing the reset discharge, a predetermined amount of wall charge is uniformly formed in the respective discharge cells and the wall charge is maintained.
By executing the simultaneous resetting step Rc, all of the discharge cells in PDP
10
are initialized to the state (sustaining discharge) capable of emitting light in a light emission sustaining step Ic, mentioned later (hereinafter, referred to as “light emitting cell” state).
Next, at a pixel data writing step Wc, the driver
100
separates respective bits of the 4 bit pixel data in correspondence with the respective subfields SF
1
through SF
4
and generates pixel data pulses having a pulse voltage in accordance with the logical level of the corresponding bit. For example, at pixel data writing step Wc of the subfield SF
1
, the driver
100
generates a pixel data pulse having a pulse voltage in accordance with the logical level of the first bit of the pixel data. In this process, the driver
100
generates a pixel data pulse having a pulse voltage of high voltage when the logical level of the first bit is “1”, or low voltage (0 volt) when the logical level of the first bit is “
0
0”. Further, the driver
100
applies the pixel data pulses successively to the column electrodes D
1
through D
m
as shown in
FIG. 3
as a group of pixel data pulses DP
1
through DP
n
for respective single display line in correspondence with each of the 1-th through the n-th display lines. Further, the driver
100
generates a scan pulse SP having a negative polarity as shown in
FIG. 3
in synchronism with an application timing of each of the respective pixel data pulse group DP and applies it successively to the row electrodes Y
1
through Y
n
. With this operation, there causes discharge (selective erasure discharge) only at the discharge cell at a portion intersected with the display line applied with the scan pulse SP and “column” applied with the pixel data pulse having high voltage. By the selective erasure discharge, wall charge held in the discharge cell is extinguished and the discharge cell is shifted to a state of being incapable of emitting light (sustaining discharge) in the light emission sustaining step Ic, mentioned later (hereinafter, referred to as “no light emitting cell”). Meanwhile, the selective erasure discharge is not caused in the discharge cell applied with the pixel data pulse having low voltage even when the discharge cell is applied with the scan pulse SP and the discharge cell maintains the state of being initialized at the simultaneous resetting step Rc, that is, the state of “light emitting cell”.
That is, according to the pixel data writing step Wc, the respective discharge cell of PDP
10
is set to either of the “light emitting cell” state and the “no light emitting cell” state in accordance with the pixel data based on the inputted image signal.
Next, at the light emission sustaining step Ic, as shown in
FIG. 3
, the driver
100
applies sustaining pulses IP
X
having a positive polarity and sustaining pulses IP
Y
having a positive polarity respectively to the row electrodes X
1
through X
n
and the row electrodes Y
1
through Y
n
alternately repeatedly. Further, the number of times (periods) of application of the sustaining pulses IP
X
and IP
Y
in one subfield are set in accordance with weighting of the respective subfields as shown in FIG.
2
. In this process, only the discharge cell at which wall charge is present, that is, the discharge cell brought into the “light emitting cell” state, carries out a sustaining discharge each time the sustaining pulses IP
X
and IP
Y
are applied. That is, only the discharge cell set to the “light emitting cell” state in the pixel data writing step Wc, repeats light emission in accordance with sustaining discharge by the number of times set in correspondence with the weighting of the respective subfield as shown in
FIG. 2
, and maintains the light emitting state.
The driver
100
carries out the above-described operation for the respective subfield. The brightness of an intermediate tone in correspondence with the image signal is expressed by a total number of light emission (in one field) associated with the sustaining discharge created in the respective subfield. That is, by the light emission associated with the sustaining discharge, an image in correspondence with the image signal is displayed.
However, according to the above-described driving operation utilizing the discharge phenomenon, discharges accompanied by light emission which are not related to the display image, that is, the resetting discharge and selective erasure discharge must also be produced. Particularly, as a result of the reset discharge, all of the discharge cells simultaneously emit light. Therefore, there arises a problem that, when displaying a black image or an image having a extremely low brightness near to the black peak, a deterioration in contrast becomes remarkable.
OBJECT AND SUMMARY OF THE INVENTION
The invention has been made in view of the above-described problem and it is an object of the present invention to provide a method of driving a plasma d
Ide Shigeo
Tokunaga Tsutomu
Pioneer Corporation
Tran Thuy Vinh
Wong Don
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