KR20040026849A - Method for driving plasma display panel wherein set gray-scale varies - Google Patents

Abstract

PURPOSE: A method for driving a plasma display panel whose set gray level varies is provided to increase linearity and performance of display gray level at a dark screen and to prevent pseudo contour of moving pictures generated at a bright screen. CONSTITUTION: According to the method for driving a plasma display panel whose set gray level varies, each frame has a plurality of sub fields and gray display is performed according to the display in each sub field. The set gray level of each frame varies according to an average signal level of an input image signal. The set gray level of a high average signal level is lower than that of a low average signal level.

Description

Method for driving plasma display panel where set gray-scale varies}

The present invention relates to a method of driving a plasma display panel. More particularly, the present invention relates to a method of driving a plasma display panel. It relates to a driving method.

1 shows a structure of a conventional three-electrode surface discharge plasma display panel. FIG. 2 illustrates a configuration of a unit display cell of the panel of FIG. 1. 1 and 2, between the front and rear glass substrates 10 and 13 of a conventional surface discharge plasma display panel 1, address electrode lines A _R1 ,..., A _Bm , a dielectric layer. (11, 15), Y electrode lines (Y ₁ , ..., Y _n ), X electrode lines (X ₁ , ..., X _n ), phosphor 16, partition 17 and protective layer As a magnesium monoxide (MgO) layer 12 is provided.

The address electrode lines A _R1 ,..., A _Bm are formed in a predetermined pattern on the front side of the rear glass substrate 13. The lower dielectric layer 15 is applied to the entire surface in front of the address electrode lines A _R1 ,..., A _Bm . In front of the lower dielectric layer 15, barrier ribs 17 are formed in a direction parallel to the address electrode lines A _R1 ,..., And A _Bm . These partitions 17 function to partition the discharge area of each cell and to prevent optical cross talk between each cell. The phosphor 16 is applied between the partition walls 17.

The X electrode lines X ₁ , ..., X _n and the Y electrode lines Y ₁ , ..., Y _n are orthogonal to the address electrode lines A _R1 , ..., A _Bm . It is formed in a constant pattern on the back of the front glass substrate 10. Each intersection sets a corresponding cell. Each X electrode line (X ₁ , ..., X _n ) and each Y electrode line (Y ₁ , ..., Y _n ) is a transparent electrode line of a transparent conductive material such as indium tin oxide (ITO) or the like (FIG. 2). X _na , Y _na ) and a metal electrode line (X _nb , Y _nb of FIG. 2) for increasing conductivity are formed. The front dielectric layer 11 is formed by applying the entire surface to the rear of the X electrode lines X ₁ ,..., X _n and the Y electrode lines Y ₁ ,..., Y _n . A protective layer 12 for protecting the panel 1 from a strong electric field, for example, a magnesium monoxide (MgO) layer, is formed by applying the entire surface to the back of the front dielectric layer 11. The plasma forming gas is sealed in the discharge space 14.

Referring to FIG. 3, a typical driving device of the plasma display panel 1 includes an image processor 56, a logic controller 52, an address driver 53, an X driver 54, and a Y driver 55. . The image processing unit 56 converts an external analog image signal into a digital signal to convert an internal image signal, for example, 8-bit red (R), green (G), and blue (B) image data, a clock signal, vertical and horizontal, respectively. Generate sync signals. The logic controller 52 generates driving control signals S _A , S _Y , and S _X according to an internal image signal from the image processor 56. The address driver 53 generates the display data signal by processing the address signal S _A among the drive control signals S _A , S _Y , and S _X from the logic controller 52, and generates the display data signal. Is applied to the address electrode lines. The X driver 54 processes the X driving control signal S _X among the driving control signals S _A , S _Y , and S _X from the logic controller 52 and applies the X driving control signal S _X to the X electrode lines. The Y driver 55 processes the Y driving control signal S _Y among the driving control signals S _A , S _Y , and S _X from the logic controller 52, and applies the Y driving control signal S _Y to the Y electrode lines.

Referring to FIG. 4, in the conventional driving method of the plasma display panel of FIG. 1, the setting gray level G _MAX of each frame is always constant regardless of the average signal level of the input image signal. For example, the same high average signal level of the set of frames (L _REF ~ L _MAX) gray level (G _MAX) and the lowest setting of the frame in the average signal level (0 ~ L _REF) gray level (G _MAX).

FIG. 5 illustrates a signal level range required by unit gray scale in a low gray scale range by the driving method of FIG. 4. In FIG. 5, reference symbol C _G denotes a characteristic curve of display gradation for green signal level, C _R denotes a characteristic curve of display gradation for red signal level, and C _B denotes a characteristic curve of display gradation for blue signal level. Point to each one. 3 and 5, when the data of the internal image signal input to the logic controller 52 has a reverse nonlinear input / output characteristic in order to correct the nonlinear input / output characteristics of the cathode ray tube, the logic controller 52 inputs a reverse nonlinear input. Nonlinear correction (see C _G , C _R , and C _B ) is performed so that the input / output data has a linear input / output characteristic. Therefore, in the low gradation region, since the deviation of the signal level range required by the unit gradation is large, nonlinearity of the display gradation with respect to the signal level is inevitable. In addition, in the low gradation region, since the signal level range required by the unit gradation is wide, the performance of the gradation display is degraded.

FIG. 6 shows that 256 gray levels are applied to all unit frames by the driving method of FIG. 4. Referring to FIG. 6, each of all unit frames is divided into eight subfields SF1,..., SF8 to realize time division gray scale display. Further, each subfield SF1, ..., SF8 has an initialization period I1, ..., I8, an address period A1, ..., A8, and a sustain-discharge period S1, ... , S8).

The discharge conditions of all the display cells become uniform in each initialization period I1, ..., I8.

In each address period A1, ..., A8, a display data signal is applied to the address electrode lines (A _R1 , ..., A _{Bm in} FIG. 1) and at the same time, each Y electrode line (Y ₁ ,... Scanning pulses corresponding to Y _n ) are sequentially applied. Accordingly, when a high level display data signal is applied while the scan pulse is applied, wall charges are formed by the address discharge in the corresponding discharge cell, and wall charges are not formed in the discharge cell that is not.

In each sustain-discharge period S1, ..., S8, all Y electrode lines Y ₁ , ..., Y _n and all X electrode lines X ₁ , ..., X _n The sustain-discharge pulses are alternately applied, causing display discharge in discharge cells in which wall charges are formed in corresponding address periods A1, ..., A8. Therefore, the luminance of the plasma display panel is proportional to the length of the sustain-discharge periods S1, ..., S8 occupied in the unit frame. The length of the sustain-discharge periods S1, ..., S8 occupied in the unit frame is 255T (T is unit time). Therefore, it can be displayed in 256 gray scales, even if it is not displayed once in a unit frame.

Here, the time 1T corresponding to 2 ⁰ in the sustain-discharge period S1 of the first subfield SF1 corresponds to 2 ¹ in the sustain-discharge period S2 of the second subfield SF2. Time 2T corresponds to 2 ² in the sustain-discharge period S3 of the third subfield SF3, and ² in the sustain-discharge period S4 of the fourth subfield SF4. ^The time 8T corresponding to ³ corresponds to the time 16T corresponding to 2 ⁴ in the sustain-discharge period S5 of the fifth subfield SF5, and the sustain-discharge period of the sixth subfield SF6. S6) corresponds to the time 32T corresponding to 2 ⁵ , the sustain-discharge period S7 of the seventh subfield SF7 includes the time 64T corresponding to 2 ⁶ , and the eighth subfield SF8. In the sustain-discharge period S8, a time 128T corresponding to 2 ⁷ is set, respectively.

Accordingly, if a subfield to be displayed among the eight subfields is appropriately selected, 256 gray levels may be displayed including all zero (zero) grays not displayed in any subfields.

In the time division gray scale display of the plasma display panel as described above, since the display cells in each sub-field do or do not discharge, pseudo contours may appear in a direction perpendicular to the moving direction of the object when a moving image is displayed. . This pseudo contour may appear more frequently as the weight difference between subfields adjacent to each other increases. Here, the weight of each subfield means a time allocated to each subfield. Referring to FIG. 6, a weight difference between the first and second subfields SF1 and SF2 is 1, a weight difference between the second and third subfields SF2 and SF3 is 2, and a third And the weight difference between the fourth subfields SF3 and SF4 is 4, the weight difference between the fourth and fifth subfields SF4 and SF5 is 8, and the fifth and sixth subfields SF5. , The weight difference between SF6 is 16, the weight difference between the sixth and seventh subfields SF6 and SF7 is 32, and the weight difference between the seventh and eighth subfields SF7 and SF8 is 64. Therefore, since the weight difference is large between adjacent subfields having a large weight, the pseudo contour may appear frequently on a bright screen.

Therefore, as shown in FIG. 6, when the setting gray level of all the unit frames is always constant, it is difficult to prevent pseudo contours of a video that appears relatively frequently on a bright screen.

As described above, in the conventional driving method of the plasma display panel, the setting gray level of each frame is always constant regardless of the average signal level of the input video signal. Accordingly, there are the following problems.

First, since the deviation of the signal level range required by the unit gray scale in a dark screen is large, the linearity of the display gray level for each signal level in a dark screen cannot be increased.

Second, since the signal level range required by the unit gray scale is wide on a dark screen, the performance of the gray scale display on a dark screen cannot be improved.

Third, there is a difficulty in preventing pseudo contours of moving images that appear relatively frequently on a bright screen.

Disclosure of Invention An object of the present invention is to provide a driving method of driving a plasma display panel, which can improve linearity and performance of display grayscales on a dark screen, and prevent pseudo contours of moving images that are relatively frequently seen on a bright screen. will be.

1 is a perspective view showing an internal structure of a conventional three-electrode surface discharge plasma display panel.

FIG. 2 is a cross-sectional view illustrating a configuration of a unit display cell of the panel of FIG. 1.

3 is a block diagram illustrating a conventional driving device of the plasma display panel of FIG. 1.

4 is a graph illustrating a conventional driving method of the plasma display panel of FIG. 1.

FIG. 5 is a graph illustrating a signal level range required by unit gray scale in a low gray scale range by the driving method of FIG. 4.

FIG. 6 is a timing diagram illustrating 256 gray scales applied to all unit frames by the driving method of FIG. 4.

7 is a graph illustrating a driving method of the present invention for the plasma display panel of FIG. 1.

FIG. 8 is a graph illustrating a signal level range required by unit gray scale in a low gray scale range by the driving method of FIG. 7.

FIG. 9 is a timing diagram illustrating that 512 gray levels are applied to unit frames having a low average signal level by the driving method of FIG. 7.

FIG. 10 is a timing diagram illustrating that 256 grayscales are applied to unit frames having a high average signal level by the driving method of FIG. 7.

<Explanation of symbols for the main parts of the drawings>

1 ... plasma display panel, 10 ... front glass substrate,

11, 15 dielectric layer, 12 protective layer,

13 ... back glass substrate, 14 ... discharge space,

16 phosphors, 17 bulkheads,

X ₁ , ..., X _n ... X electrode line, Y ₁ , ..., Y _n ... Y electrode line,

A _R1 , ..., A _Bm ... address electrode line, X _na , Y _na ... transparent electrode line,

X _nb , Y _nb ... metal electrode lines, SF1, ..., SF9 ... sub-field,

52 logic controller, 53 address drive,

54 ... X drive, 55 ... Y drive,

56 Image processing unit.

According to an aspect of the present invention, there is provided a method of driving a plasma display panel in which a plurality of subfields exist in each frame, and gray scale display is performed according to whether or not display is performed in each subfield. The set gradation changes in accordance with the average signal level of the input video signal.

This has the following effects.

First, since the set gradation of a frame having a low average signal level can be increased, the deviation of the signal level range required by the unit gradation in a dark screen can be reduced. Accordingly, the linearity of the display gray level for each signal level can be increased in a dark screen.

Second, since the set gray level of a frame having a low average signal level can be increased, the signal level range required by unit gray can be narrowed in a dark screen. Accordingly, the performance of the gradation display can be improved on a dark screen.

Third, since the setting gray level of the frame of the high average signal level can be lowered, the weight difference between the adjacent weighted subfields is reduced. Accordingly, it is possible to easily prevent pseudo contours of moving images that appear relatively frequently on a bright screen.

Hereinafter, preferred embodiments according to the present invention will be described in detail. 1 to 3 are equally applicable to the present invention.

Referring to FIG. 7, in the driving method of the present invention with respect to the plasma display panel of FIG. 1, a setting gray level of each frame is changed according to an average signal level of an input image signal. For example, the set grayscale G _MAX1 of the frames of the high average signal level L _REF to L _MAX is lower than the set grayscale G _MAX2 of the frames of the low average signal level 0 to L _REF .

FIG. 8 is a view illustrating a signal level range required for unit display gradation in a low gradation region by the driving method of FIG. 7. In FIG. 8, reference symbol C _G denotes a characteristic curve of display gradation for a green signal level, C _R denotes a characteristic curve of display gradations for a red signal level, and C _B denotes a characteristic curve of display gradations for a blue signal level. Point to each one. 7 and 8, the setting gray level G _MAX2 of the frames of the low average signal level 0 to L _REF is relatively high. Accordingly, since the deviation of the signal level range required by the unit gray scale in the dark screen is reduced, the linearity of the display gray level for each signal level in the dark screen can be improved. In addition, since the signal level range required by the unit gray scale in a dark screen is narrowed, it is possible to increase the performance of the gray scale display in a dark screen.

Meanwhile, the setting gray level G _MAX1 of the frames having the high average signal level L _REF to L _MAX is relatively low. Accordingly, since the weight difference between the adjacent subfields having a large weight is reduced, it is possible to easily prevent pseudo contours of a moving picture which is relatively frequently displayed on a bright screen.

FIG. 9 shows that 512 gray levels are applied to unit frames of a low average signal level by the driving method of FIG. 7. Referring to FIG. 9, each of the unit frames of a low average signal level is divided into nine subfields SF1,..., SF9 in order to realize time division gray scale display. Further, each subfield SF1, ..., SF9 has an initialization period I1, ..., I9, an address period A1, ..., A9, and a sustain-discharge period S1, ... , S9).

The discharge conditions of all the display cells become uniform in each initialization period I1, ..., I9.

Each of the address periods (A1, ..., A9) In, the address electrode lines (A _R1 of Fig. 1, ..., A _Bm) as soon applying a display data signal for each Y electrode lines (Y _1, at the same time. Scanning pulses corresponding to Y _n ) are sequentially applied. Accordingly, when a high level display data signal is applied while the scan pulse is applied, wall charges are formed by the address discharge in the corresponding discharge cell, and wall charges are not formed in the discharge cell that is not.

In each sustain-discharge period S1, ..., S9, all Y electrode lines Y ₁ , ..., Y _n and all X electrode lines X ₁ , ..., X _n The sustain-discharge pulses are alternately applied, causing display discharge in discharge cells in which wall charges are formed in corresponding address periods A1, ..., A9. Therefore, the luminance of the plasma display panel is proportional to the length of the sustain-discharge periods S1, ..., S9 occupied in the unit frame. The length of the sustain-discharge cycles S1, ..., S9 occupied in the unit frame is 511T (T is the unit time). Therefore, the display may be performed with 512 gray levels, including the case where the display is not performed once in the unit frame.

Here, the time 1T corresponding to 2 ⁰ in the sustain-discharge period S1 of the first subfield SF1 corresponds to 2 ¹ in the sustain-discharge period S2 of the second subfield SF2. Time 2T corresponds to 2 ² in the sustain-discharge period S3 of the third subfield SF3, and ² in the sustain-discharge period S4 of the fourth subfield SF4. ^The time 8T corresponding to ³ corresponds to the time 16T corresponding to 2 ⁴ in the sustain-discharge period S5 of the fifth subfield SF5, and the sustain-discharge period of the sixth subfield SF6. In S6), the time 32T corresponding to 2 ⁵ is maintained, and in the sustain-discharge period S7 of the seventh subfield SF7, the time 64T corresponding to 2 ⁶ is maintained, and the eighth subfield SF8 is maintained. A time 128T corresponding to 2 ⁷ is set in the discharge period S8, and a time 256T corresponding to 2 ⁸ is set in the sustain-discharge period S9 of the ninth subfield SF9, respectively.

Accordingly, if the subfield to be displayed among the nine subfields is appropriately selected, the display of all 512 gray levels, including 0 (zero) gray that is not displayed in any subfield, can be performed.

As described above, the setting gray level (G _MAX2 of FIG. 7) of the frames having the low average signal level (0 to L _REF of FIG. 7) is relatively high as 512 gray levels. Accordingly, since the deviation of the signal level range required by the unit gray scale in the dark screen is reduced, the linearity of the display gray level for each signal level in the dark screen can be improved. In addition, since the signal level range required by the unit gray scale in a dark screen is narrowed, it is possible to increase the performance of the gray scale display in a dark screen.

FIG. 10 shows that 256 grayscales are applied to unit frames having a high average signal level by the driving method of FIG. 7. In FIG. 10, the same reference numerals as used in FIG. 9 refer to the objects having the same function, and thus only the differences from FIG. 9 will be described with respect to the configuration and operating principle of the driving method of FIG. 10.

Referring to FIG. 10, a time 64T corresponding to 2 ⁶ is set for each of the sustain-discharge periods S7, S8, and S9 of the seventh to ninth subfields SF7 to SF9. Accordingly, if the subfield to be displayed among the nine subfields is appropriately selected, the display of all 256 gray levels including zero (zero) gray that is not displayed in any subfield can be performed.

As described above, the setting gray level (G _MAX1 of FIG. 7) of the frames having the high average signal level (L _REF to L _MAX of FIG. 7) is relatively low as 256 gray levels. As a result, the weight difference between the adjacent weighted subfields is reduced. Referring to FIG. 10, a weight difference between the first and second subfields SF1 and SF2 is 1, a weight difference between the second and third subfields SF2 and SF3 is 2, and a third And the weight difference between the fourth subfields SF3 and SF4 is 4, the weight difference between the fourth and fifth subfields SF4 and SF5 is 8, and the fifth and sixth subfields SF5. , The weight difference between SF6 is 16, the weight difference between the sixth and seventh subfields SF6 and SF7 is 32, and the weight difference between the seventh and eighth subfields SF7 and SF8 is There is no weight difference between the eighth and ninth subfields SF8 and SF9. In this high average signal level (L _REF ~ L _MAX ) frames, the weight difference between the heavy adjacent subfields is reduced, so that the pseudo contour of the video that is relatively frequently seen on a bright screen can be easily prevented. have.

As described above, the driving method of the plasma display panel according to the present invention has the following effects.

First, since the set gradation of a frame having a low average signal level can be increased, the deviation of the signal level range required by the unit gradation in a dark screen can be reduced. Accordingly, the linearity of the display gray level for each signal level can be increased in a dark screen.

Second, since the set gray level of a frame having a low average signal level can be increased, the signal level range required by unit gray can be narrowed in a dark screen. Accordingly, the performance of the gradation display can be improved in a dark screen.

Third, since the setting gray level of the frame of the high average signal level can be lowered, the weight difference between the adjacent weighted subfields is reduced. Accordingly, it is possible to easily prevent pseudo contours of moving images that appear relatively frequently on a bright screen.

The present invention is not limited to the above embodiments, but may be modified and improved by those skilled in the art within the spirit and scope of the invention as defined in the claims.

Claims (2)

A method of driving a plasma display panel in which a plurality of subfields exist in each frame, and gray scale display is performed according to whether or not display in each subfield is performed. And a set gray level of each frame is changed according to an average signal level of an input video signal. The method of claim 1, A driving method in which the set gradation of a frame of a high average signal level is lower than that of a low average signal level.