Electric lamp and discharge devices: systems – Plural power supplies – Plural cathode and/or anode load device
Reexamination Certificate
2002-11-26
2004-07-13
Wong, Don (Department: 2821)
Electric lamp and discharge devices: systems
Plural power supplies
Plural cathode and/or anode load device
C315S169200, C345S060000
Reexamination Certificate
active
06762567
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a driving method and a driving device for a matrix display-type plasma display panel (hereinafter referred to as PDP)
2. Description of Related Art
AC (alternating current discharge) type PDP is well known as one such matrix display-type display panel.
The AC-type PDP comprises a plurality of column electrodes, and a plurality of row electrodes, which are arranged orthogonal to these column electrodes, and which form one scanning line per pair of electrodes. These respective row electrodes and column electrodes are covered with a dielectric layer for the discharge space, and assume a structure, wherein a discharge cell, which supports a pixel, is formed at each intersecting portion of a pair of row electrodes and a column electrode.
Here, a subfield method is known as one method for implementing an intermediate brightness display for this PDP. In a subfield method, the display period of one field is displayed by being divided into N subfields, which emit light only for a time corresponding to the weighting of each bit digit of N-bits of pixel data.
When using the subfield method, if it is supposed, for example, that the pixel data being supplied is constituted by six bits, a period of one field is divided into six subfields SF
1
, SF
2
. . . , SF
6
, and emission driving is performed for each subfield.
Each subfield is constituted by a simultaneous resetting step, a pixel data writing step, and an emission sustaining step. In a simultaneous resetting step, by simultaneously causing discharge excitation (reset discharging) of all the discharge cells of the above-mentioned PDP, the wall charges of all the discharge cells are uniformly erased. In the subsequent pixel data writing step, a selective write discharge corresponding to pixel data occurs in each discharge cell. In this state, a wall charge is formed inside a discharge cell in which a write discharge occurred, and this discharge cell is set to an “light-emitting cell.” Conversely, since a wall charge is not formed in a discharge cell in which a write discharge did not occur, this cell becomes a “non-light-emitting cell.” In an emission sustaining step, only a discharge cell, which has been set to an “light-emitting cell”, is discharged repeatedly during a period of time corresponding to the weighting of each subfield. In this process, a brightness corresponding to the total discharge period implemented in the emission sustaining steps of subfields SF
1
through SF
6
, respectively, is visible. That is, if discharge periods of ratios of 1:2:4:8:16:32 are allocated to each subfield SF
1
through SF
6
, then an intermediate brightness of 64 grayscale levels can be represented.
However, the reset discharge, which was implemented for all discharge cells in this simultaneous resetting step, is accompanied by a relatively strong discharge, that is, an emission of light that is a high level of brightness. The problem is that, since an emission that has nothing in the least to do with pixel data is generated by the reset discharge at this time, this causes a drop in dark contrast when enjoying a darker image, especially inside a darkened room.
Furthermore, in another example, when the pixel data for each pixel based on an input picture signal, for example, is eight bits, a one field display period is divided into eight subfields, and a simultaneous resetting step, a pixel data writing step, and an emission sustaining step are executed sequentially inside each subfield.
In a simultaneous resetting step, discharge excitation (reset discharging) is caused in all the discharge cells of the above-mentioned PDP simultaneously, thereby causing wall charges to be formed inside all the discharge cells. In a pixel data writing step, a discharge occurs selectively (selective erase discharge) for each discharge cell according to the logic level of the pixel data bit corresponding to the subfield thereof. In this process, the wall charge inside a discharge cell in which a selective erase discharge occurred is erased, and this discharge cell is set to a non-light-emitting cell state. Conversely, since the wall charge inside a discharge cell in which a selective erase discharge did not occur remains unchanged, this discharge cell is set to an light-emitting cell state. In an emission sustaining step, only a discharge cell, which has been set to the above-mentioned light-emitting cell state, is repeatedly discharged (sustain discharged) during a period of time corresponding to the weighting of each subfield. In this time, a brightness corresponding to the total number of sustain discharges, which occurred in the respective emission sustaining steps of the eight subfields, is visible. In other words, if numbers of sustain discharges having the ratios of 1:2:4:8:16:32:64:128 are allocated to the eight subfields, respectively, by combining the subfields in which sustain discharges occur within a one field display period, an intermediate brightness of 256 (=2
8
) grayscale levels can be represented.
In driving a PDP in this way, a plurality of discharge cells are subjected to repeated sustain discharges in the emission sustaining steps of the respective subfields to achieve a display of intermediate brightness corresponding to input picture signals. Consequently, the problem is that, since current is applied to the respective discharge cells each time this sustain discharge occurs, a lot of power is consumed.
Furthermore, when a picture signal, which represents a high brightness picture, is supplied, the problem is that, since the number of sustain discharges occurring per unit time to realize this high brightness picture display increases, the power consumption increases in accordance with this.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a plasma display driving device, which is capable of enhancing contrast.
A driving device of a plasma display panel according to a first aspect of the present invention is a plasma display panel driving device for driving, in accordance with picture signals, a plasma display panel, in which a plurality of discharge cells supporting display pixels are arranged in a matrix, having resetting means for generating a reset step for causing the occurrence of a reset discharge, which initializes each of the above-mentioned discharge cells to one of either an light-emitting cell state or a non-light-emitting cell state, and applies this to each of the above-mentioned discharge cells; pixel data writing means for applying to the respective above-mentioned discharge cells a scanning pulse for causing the occurrence of a selective discharge, which selectively sets the above-mentioned discharge cells to either the above-mentioned non-light-emitting cell state or the above-mentioned emission-cell state in accordance with pixel data corresponding to the above-mentioned picture signals; emission sustaining means for applying to each of the above-mentioned discharge cells a sustaining pulse for causing the occurrence of a sustain discharge, which causes light to be emitted repeatedly only from the above-mentioned discharge cells that are in the above-mentioned light-emitting cell state; a light sensor for detecting the ambient illuminance of the above-mentioned plasma display panel; and reset step waveform adjusting means for adjusting the level change rate at the leading edge portion of the above-mentioned resetting step in accordance with the above-mentioned illuminance.
Furthermore, a driving device of a plasma display panel according to a second aspect of the present invention is a plasma display panel driving device for driving, in accordance with picture signals, a plasma display panel, in which a plurality of discharge cells supporting display pixels are arranged in a matrix, having resetting means for generating a reset step for causing the occurrence of a reset discharge, which initializes each of the above-mentioned discharge cells to one of either an light-emitting cell state or a non-light-emitt
Dinh Trinh Vo
Pioneer Corporation
Sughrue & Mion, PLLC
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