KR100648678B1 - Plasma display and driving method thereof - Google Patents

Abstract

A plasma display device and a driving method thereof are provided to increase contrast ratio by removing a main reset operation of some subfields in a part of frames if a pattern that an input image is displayed on only a specific region is generated. A plasma display device includes a plasma display panel comprising discharge cells formed by first and second electrodes(X,Y) and third electrodes(A) formed across the first and second electrodes; and a control unit for driving a frame by dividing the frame into subfields(SF1~SF4) and substituting a main reset operation initializing all discharge cells, for an auxiliary reset operation initializing only the cell where sustain discharge is performed in the preceding subfield during reset periods of some subfields, if an image with a first screen load factor lower than a reference screen load factor is input.

Description

Plasma display device and driving method thereof {PLASMA DISPLAY AND DRIVING METHOD THEREOF}

1 is a diagram illustrating a general contrast ratio measurement pattern.

2 is a diagram illustrating a plasma display device according to an exemplary embodiment of the present invention.

3 is a view illustrating a driving waveform of a plasma display device according to an exemplary embodiment of the present invention.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma display device, and more particularly, to a plasma display device and a driving method thereof capable of improving contrast ratio.

The present invention relates to a plasma display device and a driving method thereof.

The plasma display device is a display device using a plasma display panel that displays text or an image by using plasma generated by gas discharge.

The display panel of the plasma display device is driven by dividing one frame into a plurality of subfields having respective weights, and each subfield is configured for a reset period, an address period, and a sustain period. Is done. The reset period is a period for initializing the state of the discharge cells in order to stably perform the address discharge, and the address period is a period for selecting a cell to be turned on from the plurality of discharge cells through the address discharge. The sustain period is a period in which sustain discharge is performed for the cells to be turned on to actually display an image.

In the plasma display device, sustain discharge pulses are applied to the scan electrodes and the sustain electrodes as many times as the weights indicated by the corresponding subfields in the sustain period.

In such a plasma display device, luminance (brightness) is determined by the number of sustain discharge pulses applied in the sustain period. However, since there is a limit to the number of sustain discharge pulses that can be applied in the sustain period, the luminance that can be implemented also has a limit. Therefore, as shown in FIG. 1, when the screen load ratio is small, that is, when only a specific region is turned on, the contrast ratio is deteriorated.

SUMMARY OF THE INVENTION The present invention has been made in an effort to provide a plasma display device and a driving method thereof capable of improving contrast ratio.

According to an aspect of the present invention, a plasma display device including a plasma display panel and a controller is provided. In the plasma display panel, a plurality of discharge cells are formed by a plurality of first electrodes, a plurality of second electrodes, and a plurality of third electrodes formed in a direction crossing the first electrode and the second electrode. The controller divides and drives one frame into a plurality of subfields, and when an image having a first screen load factor lower than a reference screen load factor is input, all of the discharge cells are in the reset period of some subfields of the plurality of subfields. Control to perform a main reset to initialize the.

The controller may control the main reset to be performed only during a reset period of the subfields in some frames of a plurality of frames when an image having the first screen load ratio is input.

According to another aspect of the present invention, there is provided a driving method of a plasma display device for dividing and driving each of a plurality of frames into a plurality of subfields having respective weights. According to this driving method, the method may further include detecting a pattern of an input image, comparing the detected input pattern with a predetermined pattern, and when the detected input pattern is the predetermined pattern. Removing a main reset that performs initialization for all discharge cells in the subfield.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention, and like reference numerals designate like parts throughout the specification. In addition, when a part is said to "include" a certain component, this means that it may further include other components, except to exclude other components unless otherwise stated.

In the present invention, the wall charge refers to a charge formed close to each electrode on the wall of the cell (eg, the dielectric layer). And the wall charge is not actually in contact with the electrode itself, but is described here as “formed”, “accumulated” or “stacked” on the electrode. In addition, the wall voltage refers to the potential difference formed in the wall of the cell by the wall charge.

Now, a plasma display device and a driving method thereof according to an exemplary embodiment of the present invention will be described in detail.

First, a schematic structure of a plasma display device according to an exemplary embodiment of the present invention will be described in detail with reference to FIG. 2.

2 is a diagram illustrating a plasma display device according to an exemplary embodiment of the present invention.

As shown in FIG. 2, a plasma display device according to an exemplary embodiment of the present invention includes a plasma display panel 100, a controller 200, an address electrode driver 300, a scan electrode driver 400, and a sustain electrode driver 500. It includes.

The plasma display panel 100 includes a plurality of address electrodes A1 to Am extending in the column direction, and a plurality of sustain electrodes X1 to Xn and scan electrodes Y1 to Yn extending in pairs in the row direction. Include. The sustain electrodes X1 to Xn are formed corresponding to the scan electrodes Y1 to Yn, and generally have one end connected to each other in common. The plasma display panel 100 includes a substrate (not shown) on which the sustain and scan electrodes X1 to Xn and Y1 to Yn are arranged, and a substrate (not shown) on which the address electrodes A1 to Am are arranged. The two substrates are arranged to face each other so that the scan electrodes Y1 to Yn and the address electrodes A1 to Am and the sustain electrodes X1 to Xn and the address electrodes A1 to Am are orthogonal to each other. At this time, the discharge space at the intersection of the address electrodes A1 to Am and the sustain and scan electrodes X1 to Xn and Y1 to Yn forms a discharge cell. The structure of the plasma display panel 100 is an example, and a panel having another structure to which the driving waveform described below may be applied may also be applied to the present invention.

The controller 200 receives an image signal from an external source, outputs an address electrode driving control signal, a sustain electrode driving control signal, and a scan electrode driving control signal, and controls to drive one frame into a plurality of subfields. At this time, each subfield is composed of a reset period, an address period, and a sustain period, which is expressed as a change in time. In addition, the controller 200 controls the address electrode driving control signal, the sustain electrode driving control signal, and the scan electrode driving control to remove the main reset (see FIG. 3) when the screen load ratio is very small, that is, when a pattern of turning on only a specific region occurs. Output the signal.

The address electrode driver 300 receives an address electrode driving control signal from the controller 200 and applies a display data signal for selecting a discharge cell to be displayed to each address electrode A1 to Am.

The scan electrode driver 400 receives a scan electrode driving control signal from the controller 200 and applies a driving voltage to the scan electrodes Y1 to Yn.

The sustain electrode driver 500 receives the sustain electrode driving control signal from the controller 200 and applies a driving voltage to the sustain electrodes X1 to Xn.

Next, when a pattern of turning on only a specific region occurs as shown in FIG. 1, a driving waveform of the plasma display device will be described in detail with reference to FIG. 3.

3 is a view illustrating a driving waveform of a plasma display device according to an exemplary embodiment of the present invention. In the following, the reset period consisting of only the falling period is defined as the auxiliary reset period, and the reset period consisting of the rising period and the falling period is defined as the main reset period. At this time, the auxiliary reset period is initialized for the cell in which the sustain discharge has occurred in the immediately preceding subfield, and the main reset period is initialized for all the discharge cells.

As shown in FIG. 3, when a pattern in which only a specific region is turned on occurs as shown in FIG. 1, a main reset is applied only to a predetermined subfield among a plurality of subfields constituting one frame, and a subsidiary reset is applied to a subsequent subfield. Apply and drive. This improves the contrast ratio because the reset discharge is reduced compared to the case of performing the main reset in all subfields. In FIG. 3, the main reset is applied only to the first and second subfields, and the auxiliary reset is applied to subsequent subfields.

Specifically, in the rising period of the reset period of the first subfield, the voltage of the scan electrode Y is gradually increased from the voltage Vs to the voltage Vset while the sustain electrode X is held at 0V. Then, a weak reset discharge occurs from the scan electrode Y to the address electrode A and the sustain electrode X, respectively, and a negative wall charge is formed on the scan electrode Y, and the address electrode A and the A positive wall charge is formed on the sustain electrode X.

In the falling period of the reset period of the first subfield SF1, the voltage of the scan electrode Y is gradually decreased from the Vs voltage to the Vnf voltage while the sustain electrode X is maintained at the Ve voltage. Then, while the voltage of the scan electrode Y decreases, a weak reset discharge occurs between the scan electrode Y and the sustain electrode X and between the scan electrode Y and the address electrode A, and thus the scan electrode ( The negative wall charges formed on Y) and the positive wall charges formed on the sustain electrode X and the address electrode A are erased. In general, the magnitude of the (Vnf-Ve) voltage is set near the discharge start voltage between the Y electrode and the X electrode. As a result, the wall voltage between the Y electrode and the X electrode becomes almost 0 V, whereby a cell that does not have an address discharge in the address period can be prevented from being erroneously discharged in the sustain period.

In the address period of the first subfield SF1, in order to select a discharge cell to be turned on, a scan pulse having a VscL voltage and an address pulse having a Va voltage are respectively applied to the Y and A electrodes while the voltage of the X electrode is maintained at a Ve voltage. Is applied. The unselected Y electrode is biased to a VscH voltage higher than the VscL voltage, and a 0V voltage is applied to the A electrode of the cell that is not turned on. Then, an address discharge is generated in the discharge cells formed by the A electrode to which the Va voltage is applied and the Y electrode to which the VscL voltage is applied, so that positive wall charges are applied to the Y electrode, and negative wall charges to the A electrode and the X electrode, respectively. Is formed. In order to perform this operation in the address period, the scan electrode driver 400 selects a Y electrode to which a scan pulse of VscL is to be applied among the Y electrodes Y1 to Yn, and the address electrode driver 300 selects one Y electrode. When selected, a cell to which an address pulse of Va voltage is applied is selected among the A electrodes A1 to Am passing through the cell formed by the corresponding Y electrode.

In the sustain period of the first subfield SF1, the sustain discharge pulses having the Vs voltage and the 0 V voltage are alternately applied to the Y electrode and the X electrode in the opposite phase to generate the sustain discharge between the Y electrode and the X electrode. Thereafter, the process of applying the sustain discharge pulse of the Vs voltage to the Y electrode and the process of applying the sustain discharge pulse of the Vs voltage to the X electrode are repeated the number of times corresponding to the weight indicated by the first subfield SF1.

In this manner, when the first subfield SF1 ends, the second subfield SF2 is performed, and the reset period, the address period, and the sustain period of the second subfield SF2 are the first subfield SF1. The description is omitted because it is the same as.

In the reset period of the third subfield SF3, only the falling period is performed. In the reset period of the third subfield, the sustain discharge pulse of the voltage Vs is applied to the Y electrode in the sustain period of the second subfield. The voltage at the electrode is gradually reduced to the voltage Vnf. At this time, when sustain discharge occurs in the sustain period of the second subfield SF2, since negative wall charges are formed on the Y electrode and positive wall charges are formed on the X electrode and the A electrode, the voltage of the Y electrode is gradually increased. When the discharge start voltage is exceeded together with the wall voltage formed in the cell during the decrease, the weak discharge occurs as in the falling period of the reset period of the second subfield. Since the final voltage Vnf of the Y electrode is the same as the final voltage Vnf of the falling period of the second subfield SF2, the wall charge state of the cell after the falling period of the third subfield SF3 ends is determined to be the second voltage. It becomes substantially the same as the wall charge state after the fall period of the subfield SF2.

When no sustain discharge has occurred in the sustain period of the second subfield SF2, no address discharge occurs in the address period, so that the wall charge state of the cell remains as it is after the end of the falling period of the second subfield SF2. Keep it. Since the wall voltage formed in the cell after the fall period of the second subfield SF2 is formed near the discharge start voltage together with the applied voltage, discharge does not occur when the voltage of the Y electrode decreases to the Vnf voltage. Therefore, since no discharge occurs in the reset period of the third subfield SF3, the wall charge state set in the reset period of the second subfield SF2 is maintained.

In addition, since the address period and the sustain period of the third subfield SF3 are the same as the description of the address period and the sustain period in the first subfield SF1 described above, they are omitted.

In this way, in the subfield in which the reset period is in the falling period, reset discharge occurs when there is sustain discharge in the immediately preceding subfield, and reset discharge does not occur when there is no sustain discharge in the immediately preceding subfield. Therefore, when the first predetermined number of subfields are formed like the first subfield and the remaining subfields are formed like the third subfield SF3 in one frame as in the embodiment of the present invention, all the subfields are the first subfield. Since the reset discharge is reduced rather than forming as (SF1), the contrast ratio can be increased.

That is, when the input image turns on only a specific region as shown in FIG. 1, the contrast ratio is improved by removing the main reset and performing the auxiliary reset in some subfields.

Meanwhile, according to an embodiment of the present invention, the main reset is applied only to the first and second subfields SF1 and SF2 in one frame and the auxiliary reset is applied to the subsequent subfields SF3 to SF. Since the charge state disappears over time, the main reset may be applied intermittently in subsequent subfields.

In addition, although the driving waveform of FIG. 3 may be applied to every frame of the plurality of frames, the driving waveform of FIG. 3 may be applied to some frames of the plurality of frames, and only the auxiliary reset may be performed on all the remaining frames. In this way, the contrast ratio can be further improved than applying the driving waveform of FIG. 3 in every frame.

Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

According to the present invention, when a pattern in which an input image turns on only a specific region occurs, the contrast ratio can be improved by removing the main reset of some subfields in some frames of the plurality of frames.

Claims (8)

A plasma display panel in which a plurality of discharge cells are formed by a plurality of first electrodes, a plurality of second electrodes, and a plurality of third electrodes formed in a direction crossing the first electrode and the second electrode, and When a frame is divided into a plurality of subfields and driven, and an image having a first screen load ratio lower than a reference screen load ratio is input, the reset period of some subfields of the plurality of subfields is initialized. And a control unit for replacing the main reset with an auxiliary reset for initializing only the cells in which sustain discharge has occurred in the immediately preceding subfield. The method of claim 1, And the controller replaces the main reset of the partial subfield with the auxiliary reset in some frames of a plurality of frames when an image having the first screen load ratio is input. The method of claim 2, The reset period of the remaining subfields of the plurality of subfields is a main reset. The method according to any one of claims 1 to 3, And the first screen load ratio is 1%. In the driving method of a plasma display device which drives each of a plurality of frames divided into a plurality of subfields having respective weights, Detecting a pattern of an input image; Comparing the detected input pattern with a predetermined pattern, and When the detected input pattern is the predetermined pattern, initialization is performed only for cells in which sustain discharge has occurred in the immediately preceding subfield instead of main reset for initializing all discharge cells in some subfields of the plurality of subfields. And replacing the auxiliary reset with the auxiliary reset. The method of claim 5, And a sub-reset instead of the main reset in some of the plurality of frames. The method according to claim 5 or 6, A method of driving a plasma display device which replaces a main reset of a subfield that is later in time with the auxiliary reset. The method of claim 7, wherein And the predetermined pattern is a contrast ratio measurement pattern in which only a specific region of all cells is turned on.

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