KR20040006576A - METHOD Of DRIVING PLASMA DISPLAY PANEL - Google Patents

Abstract

PURPOSE: A method for driving a plasma display panel is provided to minimize the deterioration of the picture quality due to the false contour by improving a driving method of the plasma display panel. CONSTITUTION: The dividing process is to divide a plurality of subfields into two blocks. The reset discharge process is to perform the reset discharge for the first subfields of the divided blocks in order to reset cells. The address discharge process is to perform the address discharge for the subfields of the blocks divided by the number of gray scales. The non-radiative sustain discharge is to perform the non-radiative sustain discharge for the selected cells.

Description

Driving Method of Plasma Display Panel {METHOD Of DRIVING PLASMA DISPLAY PANEL}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma display panel, and more particularly, to a method of driving a plasma display panel capable of minimizing image degradation caused by pseudo contours.

Plasma Display Panel (hereinafter referred to as "PDP") is an ultraviolet light generated when an inert mixed gas such as He + Xe, Ne + Xe, He + Xe + Ne, etc. discharges to display an image by emitting phosphors. do. Such PDPs are not only thin and large in size, but also have improved in image quality due to recent technology development.

Referring to FIG. 1, a discharge cell of a three-electrode AC surface discharge type PDP is formed on a scan / sustain electrode 30Y and a common sustain electrode 30Z formed on an upper substrate 10, and a lower substrate 18. An address electrode 20X is provided. Each of the scan / sustain electrode 30Y and the common sustain electrode 30Z has a line width smaller than the line widths of the transparent electrodes 12Y and 12Z and the transparent electrodes 12Y and 12Z, and is formed on one edge of the transparent electrode. (13Y, 13Z). The transparent electrodes 12Y and 12Z are usually formed on the upper substrate 10 by indium tin oxide (ITO). The metal bus electrodes 13Y and 13Z are usually formed of metals such as chromium (Cr) and formed on the transparent electrodes 12Y and 12Z to reduce voltage drop caused by the transparent electrodes 12Y and 12Z having high resistance. The upper dielectric layer 14 and the passivation layer 16 are stacked on the upper substrate 10 having the scan / sustain electrode 30Y and the common sustain electrode 30Z side by side. In the upper dielectric layer 14, wall charges generated during plasma discharge are accumulated. The protective layer 16 prevents damage to the upper dielectric layer 14 due to sputtering generated during plasma discharge and increases emission efficiency of secondary electrons. As the protective film 16, magnesium oxide (MgO) is usually used. The lower dielectric layer 22 and the partition wall 24 are formed on the lower substrate 18 on which the address electrode 20X is formed, and the phosphor layer 26 is coated on the surfaces of the lower dielectric layer 22 and the partition wall 24. The address electrode 20X is formed in the direction crossing the scan / sustain electrode 30Y and the common sustain electrode 30Z. The partition wall 24 is formed in parallel with the address electrode 20X to prevent ultraviolet rays and visible light generated by the discharge from leaking to the adjacent discharge cells. The phosphor layer 26 is excited by ultraviolet rays generated during plasma discharge to generate visible light of any one of red, green, and blue. Inert mixed gas is injected into the discharge space provided between the upper and lower substrates 10 and 18 and the partition wall 24.

The PDP is time-divisionally driven by dividing one frame into several subfields with different number of emission times in order to realize grayscale of an image. Each subfield is divided into an initialization period for initializing the full screen, an address period for selecting a scan line and selecting a cell in the selected scan line, and a sustain period for implementing gray levels according to the number of discharges. Here, the initialization period is divided into a plurality of setup periods in which the rising ramp waveform is supplied and a set-down period in which the falling ramp waveform is supplied. For example, when the image is to be displayed with 256 gray levels, as shown in FIG. 2, the frame period (16.67 ms) corresponding to 1/60 second is divided into eight subfields SF1 to SF8. As described above, each of the eight subfields SF1 to SF8 is divided into an initialization period, an address period, and a sustain period. The initialization period and the address period of each subfield are the same for each subfield, while the sustain period is increased at a rate of 2 ⁿ (n = 0,1,2,3,4,5,6,7) in each subfield. . The driving method of the PDP shown in FIG. 2 is called an address / display separation subfield (hereinafter, referred to as “ADS”) driving method. Accordingly, one frame is composed of a plurality of subfields, and the degree of light emission of each subfield is different, so that a plurality of gray levels can be expressed by combining each subfield.

Table 1 shows whether or not light emission occurs in each subfield for expressing 256 gray levels in the ADS method of FIG. 2.

SF1 SF2 SF3 SF4 SF5 SF6 SF7 SF8 Dark ↑ √ ◇ ■ √ ◇ ■ √ ◇ ■ √ ◇ ■ √ ◇ ■ √ ◇ ■ √ ◇ ■ √ ◇ ■ √ ◇ □ √ ◇ ■ √ ◇ ■ √ ◇ ■ √ ◇ ■ √ ◇ ■ √ ◇ ■ √ ◇ ■ √ ◇ ■ √ ◇ □ √ ◇ ■ √ ◇ ■ √ ◇ ■ √ ◇ ■ √ ◇ ■ √ ◇ ■ √ ◇ □ √ ◇ □ √ ◇ ■ √ ◇ ■ √ ◇ ■ √ ◇ ■ √ ◇ ■ √ ◇ ■ … … … … … … … ↓ Bright √ ◇ ■ √ ◇ ■ √ □ √ □ √ □ √ □ √ □ √ □ √ □ √ ◇ ■ √ □ √ □ √ □ √ □ √ □ √ □ √ ◇ ■ √ □ √ □ √ □ √ □ √ □ √ □ √ □ √ □ √ □ √ □ √ □ √ □ √ □ √ □ √ □

In Table 1,? Indicates a reset discharge,? Indicates an address discharge by selective erasure,? Indicates a light emission sustain pulse, and? Indicates a non-light emission sustain pulse.

In the ADS driving method as described above, since the reset period and the address period exist in each subfield, the dark brightness is considerably high and the contrast is not good. In addition, since power consumption is severe in the address period and the temporal position at which light is emitted varies depending on the gradation, pseudo contour noise is generated. If pseudo contour noise occurs, pseudo contour appears on the screen, and thus the display quality is deteriorated. For example, as shown in FIG. 3, when the left half of the screen is displayed with a gradation value of 127 and the right half of the screen is displayed with a gradation value of 128, when the screen is moved to the right, light emitted from two pixels on the boundary part is moved. Since both eyes are simultaneously viewed, peak white, or white band, appears at the boundary between gradation values 127 and 128. On the contrary, when the left half of the screen is displayed with a gradation value of 128 and the right half of the screen is displayed with a gradation value of 127, the screen is moved to the right. A black belt will appear.

Therefore, the driving method as shown in FIG. 4 has been proposed to overcome the above disadvantages.

FIG. 4 is a diagram illustrating a frame structure of an m-bit default code according to another conventional technique, and Table 2 shows whether light is emitted in each subfield to express 256 gray scales according to the frame structure of FIG. 4.

Referring to FIG. 4 and Table 2, the driving method of the PDP according to another conventional technique has an initialization period for initializing the full screen, that is, a reset period once in the beginning of the frame, so that the brightness of the dark portion is lowered and the contrast is improved. Since it exists once in one frame, power consumption due to addressing is reduced. In addition, since the temporal position at which light is emitted is the same every frame, the distortion of image quality due to pseudo contours is minimized. .

The PDP according to the clear driving method is driven by dividing one frame into a plurality of subfields having different number of flashes. The clear driving method expresses the gray level to be expressed from the first subfield among the plurality of subfields, and then maintains the cell that is turned off by performing selective erase address discharge from the next subfield. In FIG. 3 and Table 2, one frame is composed of m subfields to express m + 1 gray levels.

SF1 SF2 SF3 SF4 SF5 … SFm-4 SFm-3 SFm-2 SFm-1 SFm Dark ↑ √ ◇ ■ ■ ■ ■ ■ … ■ ■ ■ ■ ■ √ □ ◇ ■ ■ ■ ■ ■ ■ ■ ■ ■ √ □ □ ◇ ■ ■ ■ ■ ■ ■ ■ ■ √ □ □ □ ◇ ■ ■ ■ ■ ■ ■ ■ √ □ □ □ □ ◇ ■ ■ ■ ■ ■ ■ … … ↓ Bright √ □ □ □ □ □ … □ ◇ ■ ■ ■ ■ √ □ □ □ □ □ □ □ ◇ ■ ■ ■ √ □ □ □ □ □ □ □ □ ◇ ■ ■ √ □ □ □ □ □ □ □ □ □ ◇ ■ √ □ □ □ □ □ □ □ □ □ □

In Table 2,? Indicates reset discharge,? Indicates address discharge by selective erasure,? Indicates light emission sustain pulse, and? Indicates non-light emission sustain pulse.

In the case of the CLEAR driving method, in order to express zero gray scale, first, a reset discharge is performed at the beginning of a frame and an address discharge for selective erasure is selected to select a corresponding cell. When a cell is selected, the cell is turned off by sustain discharge by selective erasing. An off cell keeps the cell off for the rest of the frame.

As described above, each gray level is expressed by repeating the driving for each frame. However, the PDP according to the clear driving method has a disadvantage in that the gray scale is considerably limited. That is, when one frame uses twelve subfields as shown in Table 3, the number of gradations that can be expressed is limited to thirteen.

SF1 SF2 SF3 SF4 SF5 SF6 SF7 SF8 SF9 SF10 SF11 SF12 Luminescence One 2 4 8 16 32 32 32 32 32 32 32 Expression 0 One 3 7 15 31 63 95 127 159 191 223 255

In addition, the clear driving method has a disadvantage in that image quality deterioration occurs because a luminance difference between frames is set to increase the number of gray levels.

Accordingly, an object of the present invention is to provide a method of driving a plasma display panel which can minimize image degradation caused by pseudo contours.

Another object of the present invention is to provide a method of driving a plasma display panel which can reduce address power consumption and improve darkroom contrast.

Another object of the present invention is to provide a method of driving a plasma display panel which can increase the number of gray scale expressions than a clear driving method.

1 is a perspective view showing a discharge cell structure of a conventional three-electrode AC surface discharge type plasma display panel.

2 is a diagram illustrating a frame configuration of an 8-bit default code for implementing 256 gray levels.

FIG. 3 is a diagram for describing video pseudo contour noise that appears when the plasma display panel is driven as shown in FIG. 2.

4 is a diagram illustrating a frame structure of an m-bit default code according to another conventional technique.

5 is a diagram illustrating a frame structure according to the method of driving a PDP according to an embodiment of the present invention.

6 is a view for explaining a method of driving a PDP according to another embodiment of the present invention.

<Description of Symbols for Main Parts of Drawings>

10: upper substrate 12Y, 12Z: transparent electrode

13Y, 13Z: metal bus electrode 14, 22: dielectric layer

16: protective film 18: lower substrate

20X: address electrode 24: partition wall

26: phosphor 30Y: scan / sustain electrode

30Z: common sustain electrode

In order to achieve the above object, a driving method of a PDP according to an embodiment of the present invention is a driving method of a plasma display panel having a plurality of subfields in one frame, the method comprising: dividing the plurality of subfields into two blocks; And resetting discharge for initializing the cell only in the first subfield of each of the divided two blocks, and selecting the cells in the combined subfields according to the divided two blocks according to the number of gray levels of the display image. And discharging the non-emission sustain for the selected cell.

Maintaining the discharge by the sustain discharge of the unselected cells in the present invention.

In the present invention, the temporal order for driving the two divided blocks is changed every one frame.

In the present invention, the subfields of the divided blocks have different gradation numbers.

Other objects and features of the present invention in addition to the above object will become apparent from the description of the embodiments with reference to the accompanying drawings.

Hereinafter, exemplary embodiments of the present invention will be described with reference to FIGS. 5 and 6.

5 is a diagram illustrating a frame structure according to the method of driving a PDP according to an embodiment of the present invention. Table 4 shows whether or not light emission occurs in each subfield to express gray scale according to the frame configuration of FIG. 5.

First block Second block Dark ↑ ↑ ↓ ↓ Bright SF1 SF2 SF3 SF4 SF5 … SFm / 2 SFm / 2 + 1 SFm / 2 + 2 SFm / 2 + 3 SFm / 2 + 4 … √ ◇ ■ ■ ■ ■ ■ ■ √ ◇ ■ ■ ■ ■ ■ ■ √ □ ◇ ■ ■ ■ ■ ■ √ ◇ ■ ■ ■ ■ ■ ■ √ ◇ ■ ■ ■ ■ ■ ■ √ □ ◇ ■ ■ ■ ■ ■ √ □ ◇ ■ ■ ■ ■ ■ √ □ ◇ ■ ■ ■ ■ ■ √ □ □ ◇ ■ ■ ■ ■ √ ◇ ■ ■ ■ ■ ■ ■ √ ◇ ■ ■ ■ ■ ■ ■ √ □ □ ◇ ■ ■ ■ ■ √ □ □ □ ◇ ■ ■ ■ √ ◇ ■ ■ ■ ■ ■ ■ … …

In Table 2,? Indicates reset discharge,? Indicates address discharge by selective erasure,? Indicates light emission sustain pulse, and? Indicates non-light emission sustain pulse.

5 and Table 4, the PDP driving method according to an embodiment of the present invention is driven by dividing a frame into two blocks, that is, the first and second blocks. At this time, the first and second blocks separately perform the clear driving method.

The first block and the second block according to the clear driving method each have a reset discharge only at the beginning of the half frame, and maintain the discharge by the sustain discharge before the cell is selected, that is, before the address is addressed. The cell is turned off only when the cell is selected and an address discharge has occurred. In addition, the luminance of each block has a different value by changing the number of sustain pulses, frequency, voltage, and the like, so that more gray scales can be expressed.

For example, as shown in Table 5, when one frame has 12 subfields, the PDP driving method according to the present invention can express 49 gray levels.

1st block SF1 SF2 SF3 SF4 SF5 SF6 One 3 7 15 31 63 2nd block SF7 SF8 SF9 SF10 SF11 SF12 2 5 10 23 47 79

In other words, when driving only the first block without driving the second block, seven gray levels of 0, 1, 4, 11, 26, 57, and 120 may be displayed, and the first block may be driven without driving the first block. When only two blocks are driven, seven gray levels of 0, 2, 7, 17, 40, 87, and 166 can be displayed. Thus, the PDP according to the present invention can display 13 gray levels when driving only each block.

Next, when driving the cell while keeping the cell only in the first subfield of the first block and increasing the light emitting subfield of the second block, six gray levels of 3, 8, 18, 41, 88, and 167 are displayed. In the case where the cell is maintained only in the second subfield of D, and the light emitting subfield of the second block is extended while being driven, six gray levels of 6, 11, 23, 44, 91, and 170 may be displayed. When driving each block as described above, the PDP according to the present invention displays a gray level as shown in Table 6.

SF7 SF8 SF9 SF10 SF11 SF12 SF1 3 8 18 41 88 167 SF2 6 11 23 44 91 170 SF3 13 18 30 51 98 177 SF4 28 33 45 66 113 192 SF5 59 64 76 97 144 223 SF6 122 127 139 160 207 286

The gradation representation method shown in Table 5 is an example, and may represent various gradations for the display image according to various light emission gradation arrangements. In addition, the driving method of the PDP according to the present invention can prevent the deterioration in image quality due to the difference in luminance between frames.

According to the driving method of the PDP according to the present invention, the image quality deterioration due to the pseudo contour is substantially eliminated as shown in FIG. 4 by driving one frame into two blocks, but it may not be completely eliminated. In order to minimize this phenomenon, the driving method of the PDP according to the present invention can minimize the deterioration in image quality due to pseudo contours by changing the temporal order of the first and second blocks used for each frame as shown in FIG. 6.

As described above, the driving method of the PDP according to the present invention divides the subfields in one frame into two blocks and clear-drives each of them. Accordingly, the driving method of the PDP according to the present invention can achieve the effect of increasing the number of expression grayscales, improving darkroom contrast, minimizing image degradation due to address power consumption and pseudo contour. In addition, the PDP driving method according to the present invention can prevent the deterioration of image quality due to pseudo contours by changing the temporal order of the divided two blocks.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the technical spirit of the present invention. Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification but should be defined by the claims.

Claims (4)

A driving method of a plasma display panel having a plurality of subfields in one frame, Dividing the plurality of subfields into two blocks; A reset discharge for initializing a cell only in the first subfield of each of the two divided blocks; Address-discharging the combined subfields according to the divided two blocks according to the number of gray levels of the display image to select the cell; And a non-luminescent sustain discharge for the selected cell. The method of claim 1, And maintaining the discharge of the unselected cells by sustain discharge. The method of claim 2, And a temporal order for driving the two divided blocks every one frame. The method of claim 1, And the subfields of the divided blocks have different gradation numbers.