KR100521469B1 - Driving apparatus of plasma display panel and driving method thereof - Google Patents

Abstract

The present invention relates to a driving apparatus for a plasma display panel and a driving method thereof for preventing gray level low discharge and gray level reverse phenomenon due to an address discharge failure.

According to the present invention, the dual subfield coding that can prevent the gray level low discharge due to the address discharge through the subfield gray weight design having a plurality of margin degrees of freedom in all grays except the gray level having the minimum gray weight and the maximum gray weight. A driving apparatus for a plasma display panel is provided. In addition, in order to prevent gradation inversion caused by dual subfield coding, gradation inversion is prevented by using the same subfield coding for some gradations in which gradation inversion occurs severely.

Description

A driving device of a plasma display panel and a driving method thereof {DRIVING APPARATUS OF PLASMA DISPLAY PANEL AND DRIVING METHOD THEREOF}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving apparatus for a plasma display panel (PDP) and a driving method thereof. In particular, the driving apparatus for a plasma display panel and a driving thereof for preventing gradation low discharge and gradation reversal due to an address discharge failure. It is about a method.

In particular, the present invention relates to a driving device of a screen display device for displaying an image on a panel by discharge, but hereinafter, the driving device by dual subfield coding for gray scale implementation in a plasma display display device as a typical example thereof will be described. Describe as.

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

Referring to the drawings, between the front and rear glass substrates 10 and 13 of the conventional surface discharge plasma display panel 1, the address electrode lines A _R1 , A _G1 , ..., A _Gm , A _Bm ), Dielectric layers 11 and 15, Y electrode lines (Y ₁ , ..., Y _n ), X electrode lines (X ₁ , ..., X _n ), fluorescent layer 16, partition wall 17 ) And a magnesium monoxide (MgO) layer 12 as a protective layer.

The address electrode lines A _R1 , A _G1 ,..., A _Gm , A _Bm are formed in a predetermined pattern on the front side of the rear glass substrate 13. The lower dielectric layer 15 is entirely applied in front of the address electrode lines A _R1 , A _G1 ,..., A _Gm , 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 , A _G1 ,..., A _Gm , A _Bm . These partitions 17 function to partition the discharge area of each discharge cell and to prevent optical cross talk between each discharge cell. The fluorescent layer 16 is formed between the partition walls 17.

The X electrode lines (X ₁ , ..., X _n ) and the Y electrode lines (Y ₁ , ..., Y _n ) are the address electrode lines (A _R1 , A _G1 , ..., A _Gm , A _Bm ) is formed in a predetermined pattern on the back of the front glass substrate 10 to be orthogonal to each other. Each intersection sets a corresponding discharge cell. Each X electrode line (X ₁ , ..., X _n ) and each Y electrode line (Y ₁ , ..., Y _n ) have a conductivity and a transparent electrode line made of a transparent conductive material such as indium tin oxide (ITO). Metal electrode lines for heightening are formed in combination. 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.

As a driving method of the plasma display panel 1 having the structure described above, an address-display separation driving method which is mainly used is disclosed in US Pat.

FIG. 2 is a timing diagram illustrating a conventional driving method of the plasma display panel of FIG. 1.

Referring to the drawing, a unit frame is divided into eight subfields SF1, ..., SF8 to realize time division gray scale display. Each of the subfields SF1, ..., SF8 includes reset periods R1, ..., R8, address periods A1, ..., A8, and sustain discharge periods S1, ..., SF8. , S8).

The luminance of the plasma display panel is proportional to the length of the sustain discharge cycles S1, ..., S8 occupied in the unit frame. The lengths of the sustain discharge cycles S1, ..., S8 occupy a unit frame are 255T (T is the unit time). At this time, a time corresponding to 2 ^n-1 is set in the sustain discharge period Sn of the n th subfield SFn. Accordingly, when appropriately selecting a subfield to be displayed among the eight subfields, it can be seen that display of 256 gray levels can be performed including all zero (zero) gray levels that are not displayed in any of the subfields.

3 is a timing diagram illustrating driving signals applied to electrode lines of the plasma display panel of FIG. 1 in a unit sub-field of FIG. 2.

Referring to the drawings, reference numeral S _{AR1 ..ABm} denotes a drive signal applied to each address electrode line (A _R1 , A _G1 ,..., A _Gm , A _{Bm in} FIG. 1), and S _{X1 ..Xn} denotes A driving signal applied to the X electrode lines (X ₁ , ..., X _{n in} FIG. 1), and S _{Y1 .. Yn} is each Y electrode line (Y ₁ , ..., Y _{n in} FIG. 1). Indicates a drive signal applied to.

Referring to the drawing, in the reset period PR of the unit sub-field SF, first, the voltage applied to the X electrode lines X ₁ ,..., X _n is set from the ground voltage V _G to the second. for the voltage (V _S) for example, then continue to rise to 155 volts (V). Here, the ground voltage V _G is applied to the Y electrode lines Y ₁ ,..., Y _n and the address electrode lines A _R1 , A _G1 ,..., A _Gm , A _Bm .

Next, the voltage applied to the Y electrode lines Y ₁ ,..., Y _n is third from the second voltage V _S , for example, from 155 volts V to a second voltage than the second voltage V _S. The highest voltage V _SET + V _{S that} is as high as the voltage V _SET is continuously raised to, for example, 355 volts (V). Here, the ground voltage V _G is applied to the X electrode lines X ₁ ,..., X _n and the address electrode lines A _R1 , A _G1 ,..., A _Gm , A _Bm .

Next, in the state where the voltage applied to the X electrode lines X ₁ ,..., X _n is maintained at the second voltage V _S , the Y electrode lines Y ₁ ,..., Y _n The voltage applied to) is continuously lowered from the second voltage V _S to the ground voltage V _G. Here, the ground voltage V _G is applied to the address electrode lines A _R1 , A _G1 ,..., A _Gm , and A _Bm .

Accordingly, in the address period (PA), leading address is applied to a display data signal to the electrode lines, the the second voltage (V _S) lower fourth voltage (V _SCAN) to bias the Y-electrode line than the (Y ₁ As a scan signal of the ground voltage V _G is sequentially applied to the ..., Y _n ), smooth addressing may be performed. The display data signal applied to each of the address electrode lines A _R1 , A _G1 , ..., A _Gm , A _Bm has a positive address voltage V _A when the discharge cell is selected, and a ground voltage when the discharge cell is not. (V _G ) is applied. Accordingly, when the display data signal of the positive address voltage V _A is applied while the scan pulse of the ground voltage V _G is applied, wall charges are formed by the address discharge in the corresponding discharge cell. Wall charges do not form. Here, for more accurate and efficient address discharge, the second voltage V _S is applied to the X electrode lines X ₁ ,..., X _n .

In the sustain discharge period PS that follows, the second voltage V _S is applied to all of the Y electrode lines Y ₁ , ..., Y _n and the X electrode lines X ₁ , ..., X _n . The display sustain pulse is alternately applied, causing a discharge for display retention in the discharge cells in which wall charges are formed in the corresponding address period PA.

FIG. 4 is a graph showing gradation degrees of freedom for each gradation level in an example in which each frame is divided into ten subfields to represent gradations, and FIG. 5 divides each frame into ten subfields to generate gradations. A table showing an example of subfield coding results for each gradation level in an example to be expressed.

Referring to the drawings, in FIG. 4 and FIG. 5, an example of expressing gray scales by dividing 256 gray scales into 10 subfields, gray scale weight of each subfield is 1, 2, 4, 8, 16, An example of the gradation degrees of freedom and the subfield coding result in the case of 25, 35, 45, 55, and 64 is shown. In this case, subfield coding in FIG. 5 is performed in the order of SF1, SF2, ..., SF10. When the gray level is expressed in this way, the gray level has redundancy as shown in FIG. 4 at each gray level, and thus, another subfield expressing the same gray level for a subfield combination that may cause a problem. There is a possibility of using a combination to avoid problems.

On the other hand, as shown in FIG. 2, when each frame is divided into eight subfields to express gray scales, 2 ⁸ = 256 gray scales are represented. The gray scale weight of each subfield at this time is represented by 1, 2, 4, 8, 16, 32, 64, 128 as 2 ^n-1 , and there is no margin of freedom of gray scale. However, in this case, there is a problem in that it is impossible to solve the occurrence of pseudo contours caused by changing the combination of the subfields displayed whenever the gray level increases as the subfields are increased in expressing a moving image. In this case, the pseudo contour problem can be avoided by expressing the gray scale using a combination of subfields in which the problem does not occur by increasing the number of subfields constituting each frame while expressing the same gray scale.

The plasma display panel writes data in a subfield to be displayed through address discharge. The address discharge is generated by applying a data pulse and a scan pulse to each of the address electrode and the scan electrode. Since the discharge delay time is required for this, the address period required for the address discharge is determined by the discharge delay time.

This address discharge delay time is greatly affected by priming caused by address discharge of neighboring cells. That is, when there is addressing of adjacent cells, the discharge delay time is reduced and the probability of success of address discharge is increased. On the contrary, when there is no addressing of adjacent cells, the probability of success of address discharge becomes low. When the addressing of the adjacent cells is extremely low, the probability of success of address discharge is very low. Therefore, failure of sustain discharge may occur due to the address discharge failure, which may be caused by poor gradation expression. In particular, when the failure of the address discharge is indicated in a subfield having a large gray scale weight, the gray level low discharge phenomenon in which high gray scales are not expressed intermittently becomes very serious. Should be high.

In a typical plasma display panel, an input gray scale, which is an integer, is converted into a rational number through a gamma block, and a method of distributing errors through the error diffusion block is used to convert the gray scale data converted into a rational number through an error diffusion block. . For example, when the rational number gradation input from the gamma block is 56.0625, when the number 56.0625 is to be expressed by the error diffusion block, the gradation of 56 and 57 is mixed at a spatially appropriate ratio to express the gradation 56.0625. . In the case of using the subfield coding of FIG. 5, the subfield coding corresponding to 56 and 57 becomes 1111110000 and 0 11 0 1 01 000, respectively.

As such, when 56.0625 is displayed in the spatial combination of 56 and 57, data switching occurs in SF1, SF4, SF6, SF7. Since 56.0625, the gradation 56 is turned on at an area ratio of about 93.8% per predetermined area, and 57 is turned on at an area ratio of about 6.2%. Here, the address discharge success probability of SF7 of gradation 57 becomes a problem. That is, since the SF7 of 57 is not turned on in the previous subfield, there is no priming effect due to the sustain discharge of the previous subfield, and since the neighboring cells are mostly grayscale 56, SF7 of the neighboring cell does not have address data. There is no priming effect. Therefore, addressing alone causes address discharge in a state in which the priming effect is considerably lacking, which causes grayscale low discharge.

At this time, if the 56 subfield coding is made similar to the 57 subfield coding within a range that allows the degree of freedom of gradation, the effect of reducing low discharge in low gradations can be obtained. However, in such a case, since the gray level low discharge between 55 and 56 is shifted, this means that the gray level at which the low gray level discharge occurs is eliminated, and is shifted to another gray level.

That is, when gradation switching is performed in a subfield having a large gradation weight, low discharge may occur at a low gradation, which may cause serious gradation defect of the plasma display panel. In particular, when the input grayscale passes through the gamma block, most of the grayscale moves to the low gray scale region. For example, when the input gray level is 100, the gray level is reduced to about 20 at the rear end of the gamma block. In this case, most grayscales are represented as subfields having small grayscale weights. When a subfield is designed by subfield weights as shown in FIG. 5, there is no margin in the case of a minimum weight subfield (LSB subfield). As a result, the low gray scale low discharge phenomenon is intensified due to a single addressing phenomenon caused by subfield switching due to error diffusion.

That is, the error diffusion is such that when there is any gray level g to express the gray level x below the decimal point, the gray level g + 1 is spatially combined to satisfy g <x <g + 1. At this time, a phenomenon in which the subfield coding of gray levels g and g + 1 is significantly changed according to x occurs, and a low discharge phenomenon in the rapidly changing subfield is aggravated.

The technical problem to be solved by the present invention is to solve the above-mentioned problems of the prior art and to design a subfield grayscale weight having a plurality of degrees of freedom in all grayscales except the grayscale having the minimum grayscale weight and the maximum weight, and dynamic dual subfield coding. The present invention provides a driving apparatus for a plasma display panel using dual subfield coding and a driving method thereof capable of preventing grayscale low discharge due to an address discharge failure.

Another object of the present invention is to provide a plasma display panel driving apparatus and a driving method thereof, which prevent a gray level inversion phenomenon which may occur when two subfield arrays for one gray level are designed for a subfield gray scale weight.

A driving method of a plasma display panel according to a feature of the present invention for achieving the above object is

A plasma display panel which divides an image of each field displayed on a plasma display panel in response to an input video signal into a plurality of subfields, and displays a gray level according to the combination of the subfields to display an image corresponding to the video signal. In the driving method,

(a) gamma correcting the input image signal;

(b) detecting whether the integer part of the gamma corrected gradation is odd or even;

(c) generating subfield coding such that subfield coding of a gray level having a gray level greater than an even gray level is the same for all bits except the bit having the least weight and the subfield coding of the even gray level;

(d) generating subfield coding such that a subfield coding of a gray level having a gray level greater than an odd gray level is the same for all bits except the bit having the least weight and the subfield coding of the odd subscale; And

(e) If it is detected as an even number in the step (b), the subfield generated in the step (c) is selected, and if it is detected as an odd number in the step (b), it is generated in the step (d). Selecting one subfield,

For the first gradation for the gamma corrected gradation, the subfield coding generated in the step (d) and the subfield coding generated in the step (c) are subfield codings different from each other in the subfield having a large weight. Regardless of whether the integer part of the gamma corrected gray level is even or odd, the same subfield coding is selected in step (e). The subfield having a large weight may be a subfield having the largest weight among subfields to be turned on to express the gray level in the subfield coding generated for the gamma corrected grayscale. The subfield selected in step (e) may select the subfield generated in step (d) even when the integer part of the gamma corrected gray level is an even number with respect to the first gray level.

A driving apparatus of a plasma display panel according to another aspect of the present invention is

Driving a plasma display panel for dividing an image of each field displayed on the plasma display panel in response to an input video signal into a plurality of subfields, and displaying a gray level according to the combination of the subfields to display an image corresponding to the video signal. In the apparatus,

A gamma correction unit configured to gamma correct the input image signal;

A gray level detector for detecting whether the integer part of the gamma corrected gray level is odd or even;

Generation of a first subfield such that subfield coding of a gradation level having a gradation level one level greater than an even gradation generates a subfield coding such that the subfield coding of the gradation is the same for all bits except the bit having the least weight and the subfield coding of the even gradation. part;

A second subfield generation unit for generating subfield coding so that subfield coding of a gray level having a gray level greater than an odd gray level is the same for all bits except the bit having the least weight and the subfield coding of the odd subscale ;

If the gray level regulator detects an even number, the subfield generated by the first subfield generator is selected, and if the gray level regulator detects an odd number, the gray level is generated by the second subfield generator. A subfield selector for selecting a subfield to generate a subfield,

The first gradation is a subfield coding generated by the first subfield generator and the subfield coding generated by the second subfield generator is a different subfield coding in a subfield having a large weight. The subfield selector selects the same subfield coding regardless of whether the integer part of the gamma corrected gray level is even or odd. The subfield weight array for subfield coding generated by the first subfield generator and the second subfield selector is a subfield weight array in which a subfield having a minimum gray scale weight is two or more. The subfield having a large weight may be a subfield having the largest weight among subfields to be turned on to express the gray level in the subfield coding generated for the gamma corrected grayscale. The subfield selected by the subfield selector may select a subfield generated by the second subfield generator even when the integer part of the gamma corrected grayscale is an even number with respect to the first grayscale. It is done.

DETAILED DESCRIPTION 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. Like parts are designated by like reference numerals throughout the specification.

6 is a block diagram schematically showing a driving apparatus of a plasma display panel as a preferred embodiment of the present invention. FIG. 7 is a block diagram schematically illustrating the inside of a driving controller in the driving apparatus of the plasma display panel of FIG. 6. FIG. 10 illustrates an example of subfield coding results for respective grayscale levels in an example in which grayscales are expressed by dividing each frame into 11 subfields by the driving apparatus of the plasma display panel of FIGS. 6 to 9. It is a vote.

Referring to the drawing, the driving device 2 of the plasma display panel 1 includes an image processing unit 21, a driving control unit 22, an address driving unit 23, an X driving unit 24, and a Y driving unit 25. . The image processing unit 21 converts an external analog image signal into a digital signal to convert an internal image signal, for example, 8 bits of red (R), green (G), and blue (B) image data, a clock signal, vertical and horizontal, respectively. Generate synchronization signals. The driving controller 22 generates driving control signals S _A , S _Y , and S _X according to an internal image signal from the image processor 21.

In this case, the driving unit such as the address driver 23, the X driver 24, and the Y driver 25 receives input from the driving control signals S _A , S _Y , and S _X , and generates respective driving signals. The applied driving signal to each of the electrode lines.

That is, the address driver 23 processes the address signal S _A among the drive control signals S _A , S _Y , and S _X from the logic controller 22 to generate a display data signal, and generates the displayed display. The data signal is applied to the address electrode lines. The X driver 24 processes the X driving control signal S _X among the driving control signals S _A , S _Y , and S _X from the logic controller 22 and applies the X driving control signal S _X to the X electrode lines. The Y driver 25 processes the Y driving control signal S _Y among the driving control signals S _A , S _Y , and S _X from the logic controller 22 and applies the Y driving control signal S _Y to the Y electrode lines.

The driving device 2 of the plasma display panel processes an image signal input from the outside and divides the image signal into frame units, obtains an input gray level in each frame from the video signal, and stores a plurality of frames having respective gray scale weights. The time division gray scale display according to the input gray scale is performed on the discharge display panel by dividing into subfields.

In particular, it has a margin of freedom in all input gradations except the input gradation having the minimum gradation weight and the highest gradation weight.

Further, in order to prevent the sustain discharge failure in a specific subfield, at least two subfield codings are possible in all the gray scales displayed on the plasma display panel, so that the subfield configuration in which the sustain discharge failure may occur can be avoided. The subfields are configured such that the subfields having gradation weights become two or more.

That is, for example, in the case where one frame having 256 gray levels is represented by eleven subfields, the subfield configuration is such that each subfield weight from the minimum weight subfield to the maximum weight subfield is 1 , 1 , 2. , 4, 8, 16, 25, 35, 45, 55, 63. Hereinafter, a description will be given focusing on an example of such a subfield configuration.

As such, when each subfield is designed to have such a weight, a plurality of margin degrees of freedom may be obtained in all grayscales except a grayscale having a minimum grayscale weight (0) and a grayscale having a maximum grayscale weight (255). Accordingly, even in low gray levels, the degree of freedom of gray levels is 2 or more, and other subfield configurations having the same coding of all upper subfields except the subfield having the minimum gray scale weight can be found.

FIG. 10 shows an example of such dual subfield coding. In the first subfield coding, the subfield configuration when the grayscale to be expressed is even (g = 2n) is a sub1 having a gray scale greater than 1 (2n + 1). The subfield structure is the same except for the field structure and the subfield LSB having the minimum weight, and in the second subfield coding, when the gray level to be expressed is odd (g = 2n-1), the subfield structure is larger than 1 ( 2n) The design is the same except for the subfield configuration of the gray level and the subfield LSB having the minimum weight.

Therefore, in the case of expressing grayscales having successive grayscale weights in adjacent cells, switching in a subfield having a large grayscale weight does not occur, so that priming effects due to discharge in the previous subfield and discharge in the adjacent cells are prevented. I can get enough. Accordingly, it is possible to prevent the grayscale low discharge phenomenon due to the lack of priming effect from the adjacent cell or the previous subfield occurring in the conventional subfield design.

For example, referring to FIG. 10, in the case where even 56 grays and 57 grays are sequentially turned on in adjacent cells, the first subfield having the minimum gray weight in each case is first coded by the first subfield coding. Except for, all subfields have the same subfield configuration. In addition, in the case where odd 57 grays and 58 grays are turned on in sequence in adjacent cells, the same subs in all subfields except the first subfield having the minimum gray weight in each case by the second subfield coding. You will have a field configuration. Accordingly, the gray level to be expressed is sensed to detect whether it is even or odd, so that the first subfield coding or the second subfield coding can be selected.

That is, the subfield can be selectively selected from two or more subfield codings according to the gradation level of the input gradation, and the subfield coding of the input gradation having a gradation level one level greater than the input gradation is performed by the subfield coding of the input gradation. This allows switching to occur only in one subfield, preferably in the subfield with the least weight.

To this end, the driving apparatus 2 of the plasma display panel according to the present invention can design a plasma display panel driving apparatus having a dual subfield generation system capable of dynamic dual subfield coding design. The plasma display panel driving apparatus 2 having the dual subfield generation system includes an input gray scale generator 31, a gray scale detector 33, and a subfield generator 34. It may be configured to be located in the drive control unit 22, 30 in the driving device of the plasma display panel.

The input gray scale generator 31 generates a gray scale level of the input gray scale from the image signal. In this case, the input gray level may be expressed as a rational number by inverse gamma correction according to the gray level expression method.

The gray level detector 33 detects whether the integer part of the input gray level is odd or even. The subfield generator 34 generates a subfield from the input grayscale depending on whether the number of the odds of the input grayscale is odd or even.

In this case, the subfield generator 34 may include a first subfield generator 341, a second subfield generator 342, and a subfield selector 343.

The first subfield generation unit 341 is for a case where the integer part of the input grayscale is even (g = 2n, n = natural number), and a gray level (2n + 1) having one level larger than the even input grayscale is selected. The subfield coding of the input grayscale having the same produces the same subfield coding on all the bits except the bit having the minimum weight and the subfield coding of the even input grayscale (g = 2n).

The second subfield generator 342 is for the case where the integer part of the input grayscale is odd (g = 2n-1), and the sub gray of the input grayscale having a grayscale level 2n one level larger than the odd input grayscale Field coding produces the same subfield coding at all bits except for the bit with the least weight and the subfield coding with odd input gradation (g = 2n-1).

The subfield selector 343 selects a subfield generated by the first subfield generator when the integer number of the input grayscale is even. When the integer part of the input grayscale is odd, the subfield selector 343 selects the subfield by the second subfield generator. Select the created subfield to generate a subfield.

8 and 9 are block diagrams schematically illustrating the inside of a driving controller in a driving apparatus of a plasma display panel according to another exemplary embodiment of the present invention.

Referring to the drawings, the embodiments shown in FIGS. 8 and 9 are similar embodiments according to the present invention, and the subfield generator 521 in the embodiment shown in FIG. 9 is the subfields of FIGS. 7 and 8. The same component performs the same function as the field generators 34 and 44. Hereinafter, the configuration of the present invention will be described in more detail with reference to the embodiment shown in FIG. 9.

Referring to the drawings, the driving controller 50 according to the present invention includes a clock buffer 55, a synchronization adjusting unit 526, a gamma correcting unit 51, an error diffusion unit 512, and first-in first-out. ) Memory 511, subfield generator 521, subfield matrix 522, matrix buffer 523, memory controller 524, frame-memory (RFM1, ..., BFM3), cultivation A heat unit 525, an average signal level detector 53a, a power control unit 53, EPIROM 54a, an I2C serial communication interface 54b, a timing-signal generator 54c, an XY control unit 54, and The gray scale detecting unit 63 is included.

The gamma correction unit 51 generates the gradation level of the input grayscale having the linear input / output characteristic of the video signal having the first bit number having the nonlinear input / output characteristic, and having the second bit number greater than the first bit number. . The image data R, G, and B input to the gamma correction unit 51 has a reverse nonlinear input / output characteristic in order to correct the nonlinear input / output characteristics of the cathode ray tube. Therefore, the gamma correction unit 51 processes the image data R, G, and B of the reverse nonlinear input and output characteristics to have the linear input and output characteristics. That is, in a plasma display panel having a linear characteristic, an inverse gamma correction is required for a gray scale expression that is adapted to a CRT characteristic. For example, since a low gray scale data is lost after inverse gamma correction for 8-bit gray data, a 12-bit look-up table is required. (Look-Up Table, LUT) is used to generate 12-bit inverse gamma correction gray scale data.

The error diffusion unit 512 generates a quantized input gray level expressed by quantizing the gray level of the input gray level to a third number of bits smaller than the second number of bits. That is, the error diffusion unit 512 reduces the data transmission error of the image data R, G, and B by using the first-in, first-out memory 511, which is a technique of dithering. It is used to express. At this time, the error generated during quantization is propagated to neighboring cells to maintain a local average. As a representative algorithm, Floyd Steinberg algorithm or Jarvis algorithm may be used.

 Here, the first bit number is 8 bits, the second bit number is 12 bits, and the third bit number may be 8 bits again.

In particular, the present invention converts the input grayscale, which is an integer, to the rational number through the gamma correction unit 51 to express the low grayscale, as shown in the present embodiment. In the case of toning, it is more useful to prevent data switching between adjacent cells in the same subfield.

For example, in the case where the rational number gradation output from the gamma correction unit 51 is 56.0625, in order to express the 56.0625 gradation by error diffusion, the 56 gradations and the 57 gradations can be mixed and expressed at a spatially appropriate ratio. In this case, if this is represented by 10 subfields having gray scale weights of 1, 2, 4, 8, 16, 25, 35, 45, 55, and 64, 56 may be represented by 111111000 and 57 may be represented by 0110101000. In this case, when the 56th and 57th grays are sequentially expressed in the neighboring cells, switching occurs in the seventh subfield, and switching from the sixth subfield occurs in the case of 57th gray.

However, as described in the description of FIG. 7, when the minimum weight subfield is added and the dual subfield design is performed according to the present invention, the data switching problem from the adjacent cell or the previous subfield can be solved. The gray level low discharge problem due to the sustain discharge failure in the high weight subfield can be solved.

As shown in FIGS. 7 and 8, the gray detector 63 detects whether the integer part of the input gray is odd or even, and thus, the subfield generator 521 uses a subfield configuration from two or more subfield codings. Make a choice.

The subfield generator 521 quantizes the gradation representation that has been rationalized by the gamma correction unit 51 to an integer by the error diffusion unit 512 according to whether the integer of the input grayscale is odd or even, and the quantized grayscale Generate a subfield from. The subfield generator 521 may include a first subfield generator 441, a second subfield generator 442, and a subfield selector 443. Here, since the functions of the respective components in the present invention are the same as those in Figs. 6 and 7, the detailed description is omitted.

In addition, the subfield generation unit 521 converts the 8-bit image data R, G, and B into image data R, G, and B of the number of bits corresponding to the number of subfields, respectively. For example, when grayscale driving is performed with 14 subfields in a unit frame, after converting 8-bit image data R, G, and B into 14-bit image data R, G and B, respectively, In order to reduce a data transmission error, 16 bits of image data R, G, and B are output by adding invalid data '0' of a maximum value bit (MSB) and a minimum value bit (Least Significant Bit).

The clock buffer 55 converts the 26-megahertz (MHz) clock signal CLK26 from the image processor 21 (21) into a 40-megahertz (MHz) clock signal CLK40 and outputs it. The synchronization adjustment unit 526 includes a 40-megahertz (MHz) clock signal CLK40 from the clock buffer 55, an initialization signal RS from the outside, and a horizontal synchronization signal from the image processing unit (36 in FIG. 8). (H _SYNC ) and the vertical sync signal V _SYNC are input. The synchronization adjusting unit 526 outputs the horizontal synchronization signals H _SYNC1 , H _SYNC2 , and H _SYNC3 to which the input horizontal synchronization signal H _SYNC is delayed by a predetermined number of clocks, respectively. V _SYNC ) outputs vertical synchronization signals V _SYNC2 and V _SYNC3 delayed by a predetermined number of clocks, respectively.

The subfield matrix unit 522 rearranges 16-bit video data R, G, and B into which data of different subfields is simultaneously input, so that data of the same subfield is simultaneously output. The matrix buffer unit 523 processes the 16-bit image data R, G, and B from the subfield matrix unit 522 and outputs the 32-bit image data (R, G, B).

The memory control unit 524 may include a red memory control unit for controlling three red frame R memories (RFM1, RFM2, and RFM3), and three green (G) frame memory memories (GFM1, GFM2, A green memory control unit for controlling GFM3) and a blue memory control unit for controlling the three blue frame B memories (BFM1, BFM2, BFM3). Frame data from the memory controller 524 is continuously output in units of frames and input to the rearrangement unit 525. In the drawing, reference numeral EN denotes an enable signal generated from the XY controller 54 and input to the memory controller 524 to control the data output of the memory controller 524. In addition, the reference numeral S _SYNC is generated from the XY control unit 54 to control data input / output in units of 32-bit slots in the memory control unit 524 and the rearrangement unit 525, and thus the memory control unit 524 and the rearrangement unit. The slot synchronization signal input to 525 is indicated. The rearrangement unit 525 rearranges and outputs 32-bit image data R, G, and B from the memory control unit 524 in accordance with the input format of the address driver 23 (Fig. 6).

On the other hand, the average signal level detector 53a detects the average signal-level ASL in units of frames from the 8-bit image data R, G, and B from the error diffusion unit 512, respectively, and performs the power control unit 53. To enter. The power control unit 53 generates the discharge frequency control data APC corresponding to the average signal-level ASL input from the average signal level detection unit 53a, thereby making the power consumption constant in each frame constant. Perform the function of control. Here, the load rate means the average load rate of the load rates of each subfield of the frame. The load ratio of each subfield means a ratio of the number of cells to be displayed to the number of all cells of the plasma display panel 1. In the present embodiment, the power control unit 53 performs the automatic power control function when the load rate of the frame exceeds 30%. In the YEPROM 54a, the driving sequence of the X electrode lines (X ₁ , ..., X _n in FIG. 1) and the Y electrode lines (Y ₁ , ..., Y _{n in} FIG. Timing control data is stored. The discharge recovery control data APC from the power control unit 53 and the timing control data from EPIROM 54a are input to the timing-signal generator 54c via the I2C serial communication interface 54b. The timing-signal generator 54c operates according to the input discharge count control data APC and the timing control data to generate the timing-signal. The XY control unit 54 operates in accordance with the timing-signal from the timing-signal generator 54c to output the X drive control signal S _X and the Y drive control signal S _Y.

In addition, the driving method of the plasma display panel according to the present invention is implemented in the driving apparatus of the plasma display panel shown in Figs. 6 to 10, comprising: an input gradation generating step of generating a gradation level of an input gradation from an image signal; A gray level sensing step of detecting whether the integer part of the input gray level is odd or even; A first subfield in which subfield coding of an input gradation having a gradation level one level greater than an even input gradation produces the same subfield coding in all bits except the bit having the least weight and the subfield coding of the even input gradation. Generation step; A second subfield in which the subfield coding of the input gradation having a gradation level one level greater than the odd input gradation produces the same subfield coding in all bits except the bit having the least weight and the subfield coding of the odd input gradation. Generation step; If the integer portion of the input grayscale is even, the subfield generated by the first subfield generator is selected. If the integer portion of the input grayscale is odd, the subfield generated by the second subfield generator is selected. And a subfield selection step of generating a field.

In this case, the input gray level generating step may include a gamma correction step of generating a gray level of an input gray level having a second number of bits greater than the first number of bits, and a third gray level of the input gray level less than the second number of bits. It is preferable to include an error diffusion step of generating a quantized input gray scale expressed by quantizing by the number of bits.

However, as shown in FIGS. 6 to 10, when the subfield coding is different from the input gray levels, gray level inversion may occur. For example, if there are input grayscales of 56.XX and 57.XX in one frame, since the integer part is even for 56.XX, the first subfield coding of FIG. 10 is applied as in the embodiment of the present invention. Since 56 is a subfield array of 01111110000, 57 is 111111110000, and an integer portion of 57.XX is an odd number, so 57 is 00110101000 and 58 using the second subfield coding of FIG. 10 as in the embodiment of the present invention. Becomes 10110101000. Here, 57 is a gray level reversal phenomenon in which the amount of light is changed due to a change in the subfield load because the coding arrangements are different from each other despite the same gray level. That is, when the sub-field coding arrangement is different even though the same gray level, the light-on position is different in each subfield, and thus the amount of light is changed.

In particular, as in the case of 1111111 0 000 which is the coding of gray level 57 by the first subfield coding and 1011010 1 000 which is the coding of gray level 57 by the second subfield coding, the eighth subfield weight, that is, the subfield expressing the gray scale If the largest weights are different from each other, the amount of light is different, or the gray level reversal phenomenon occurs more.

On the other hand, as shown in Figs. 11A and 11B, not only the gradation 57 but also the subfield coding according to the embodiment of the present invention, gradation 1, gradation 4, gradation 8, gradation 16, and gradation 32 are expressed. Among the subfields, the largest weights are different from each other, and thus, there is a large difference in light quantity and more gray level inversion occurs. In FIG. 11A and FIG. 11B, only some of the gray scales are shown, but other gray scales, that is, subfields having the same gray scale but particularly high weight may be different. Also, the structure of the subfield arrangement different from the embodiment of the present invention may be seen. This problem may occur when dual subfield coding is applied as in the embodiment of the present invention.

  12 is a driving device of a plasma display panel according to another embodiment of the present invention to solve such gray level inversion. 12 and the driving apparatus of the plasma display panel according to the exemplary embodiment of the present invention have the same configuration as the driving apparatus of the plasma display panel shown in FIG. 7, but the gray scale detector 33 ′ and the subfield selector 343 are the same. Since the function of ') has been changed slightly, duplicate descriptions are omitted.

As described above, since some gray scales in particular occur in some gray scales, even for even gray scale inputs, even if an even input gray scale is not selected, the subfield array generated by the first subfield generating unit 341 is selected. The subfield array generated by the field generator 342 is selected. For example, in the case of 56.XX input grayscale, the subfield array originally generated by the first subfield generation unit 341 is not selected to generate subfields for adjacent grayscales 56 and 57, but at this time, By selecting the subfield array generated by the second subfield generator 341, the coding of the subfield array generated by the second subfield generator 341 for the gray level 57 for the 57.XX input gray level is the same. This can prevent gradation inversion. Each of the gray levels generated by the second subfield generation unit 341 even when the input gray level is even in other gray levels such as gray level 0.XX, gray level 4.XX, gray level 8.XX, gray level 16.XX, gray level 32.XX The subfield arrangement of 0, gradation 4, gradation 8, gradation 16 and gradation 32 is selected.

The gray level detector 33 ′ is similar to the function described with reference to FIG. 7, but not only whether the gray level is odd or even, but also gray level in which gray level reversal occurs (for example, gray level 0.0, gray level 4). .XX, gradation 8.XX, gradation 16.XX, gradation 32.XX, gradation 56.XX). The gradation in which the gradation inversion phenomenon occurs is stored in a memory (not shown) in advance.

The subfield selector 343 'selects a subfield generated by the first subfield generator 341 when the integer number of the input grayscale is even, and a second subfield when the integer portion of the input grayscale is odd. The subfield generated by the generation unit 342 is selected to generate a subfield. In addition, the subfield selector 343 'is a gray scale in which the gray scale reversal phenomenon occurs in the gray scale detecting unit 33' (for example, gray scale 0.0, gray scale 4.XX, gray scale 8.XX, gray scale). 16.XX, gradation 32.XX, gradation 56.XX), and generate a subfield by selecting the subfield generated by the second subfield generator 342 even when the integer part is even. . Here, the gradation 4, the gradation 8, and the gradation 16 are the subs for the gradation 4, the gradation 8, and the gradation 16 in the first subfield generation unit 341 when the input gradation is 4.XX, 8.XX, and 16.XX, respectively. Instead of selecting a field, the subfield array generated by the second subfield generator 341 is selected. For the adjacent grayscales 5, 9, and 17, the subfields generated by the first subfield generator 341 are selected. The field may be selected, and the subfield generated by the second subfield generator 342 may be selected.

By doing so, it is possible to partially improve the gradation inversion caused by using different subfield coding.

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.

As described above, according to the present invention, an address discharge failure may be performed through a subfield grayscale weight design having a plurality of free degrees of freedom and a dynamic dual subfield coding design in all grayscales except a grayscale having a minimum grayscale weight and a maximum grayscale weight. It is possible to significantly reduce the gradation low discharge phenomenon.

In addition, since the probability of success of the address discharge can be increased, the address period can be reduced to enable high-speed addressing.

The same subfield coding may be applied to the gray level in which the gray level inversion occurs more, thereby reducing the gray level inversion.

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

FIG. 2 is a timing diagram illustrating a typical driving method of the plasma display panel of FIG. 1.

3 is a timing diagram illustrating driving signals applied to electrode lines of the plasma display panel of FIG. 1 in a unit sub-field of FIG. 2.

4 is a graph showing gradation degrees of freedom for each gradation level in an example in which each frame is divided into ten subfields to represent gradations.

FIG. 5 is a table showing an example of subfield coding results for each grayscale level in an example in which grayscale is expressed by dividing each frame into ten subfields.

6 is a block diagram schematically showing a driving apparatus of a plasma display panel as a preferred embodiment of the present invention.

FIG. 7 is a block diagram schematically illustrating the inside of a driving controller in the driving apparatus of the plasma display panel of FIG. 6.

FIG. 8 is a block diagram schematically illustrating the inside of a driving controller in a driving apparatus of a plasma display panel according to another exemplary embodiment of the present invention.

FIG. 9 is a block diagram schematically illustrating the inside of a driving controller in a driving apparatus of a plasma display panel according to another exemplary embodiment of the present invention.

FIG. 10 illustrates an example of subfield coding results for respective grayscale levels in an example in which grayscales are expressed by dividing each frame into 11 subfields by the driving apparatus of the plasma display panel of FIGS. 6 to 9. It is a vote.

FIG. 11 is a diagram illustrating a gray scale in which a gray level inversion phenomenon occurs a lot in the subfield coding result shown in FIG. 10.

12 is a view showing a driving apparatus of a plasma display panel according to another embodiment of the present invention.

Claims (10)

A plasma display panel which divides an image of each field displayed on a plasma display panel in response to an input video signal into a plurality of subfields, and displays a gray level according to the combination of the subfields to display an image corresponding to the video signal. In the driving method, (a) gamma correcting the input image signal; (b) detecting whether the integer part of the gamma corrected gradation is odd or even; (c) generating subfield coding such that subfield coding of a gray level having a gray level greater than an even gray level is the same for all bits except the bit having the least weight and the subfield coding of the even gray level; (d) generating subfield coding such that a subfield coding of a gray level having a gray level greater than an odd gray level is the same for all bits except the bit having the least weight and the subfield coding of the odd subscale; And (e) If it is detected as an even number in the step (b), the subfield generated in the step (c) is selected, and if it is detected as an odd number in the step (b), it is generated in the step (d). Selecting one subfield, For the first gradation for the gamma corrected gradation, the subfield coding generated in the step (d) and the subfield coding generated in the step (c) are subfield codings different from each other in the subfield having a large weight. And irrespective of whether the integer part of the gamma corrected gradation is even or odd, the same subfield coding is selected in the step (e). The method of claim 1, And wherein the weighted subfield is the weighted subfield among the subfields that should be turned on to express the grayscale in the subfield coding generated for the gamma corrected grayscale. The method according to claim 1 or 2, In the case of the first gray level, even if the integer part of the gamma corrected gray level is an even number, the subfield selected in the step (e) selects the subfield generated in the step (d). Method of driving. The method according to claim 1 or 2, And diffusing the gamma corrected data after the step (a).  The method according to claim 1 or 2, And the first gray level is stored in advance, and detecting whether the gamma corrected gray level is the first gray level. Driving a plasma display panel for dividing an image of each field displayed on the plasma display panel in response to an input video signal into a plurality of subfields, and displaying a gray level according to the combination of the subfields to display an image corresponding to the video signal. In the apparatus, A gamma correction unit configured to gamma correct the input image signal; A gray level detector for detecting whether the integer part of the gamma corrected gray level is odd or even; Generation of a first subfield such that subfield coding of a gradation level having a gradation level one level greater than an even gradation generates a subfield coding such that the subfield coding of the gradation is the same for all bits except the bit having the least weight and the subfield coding of the even gradation. part; A second subfield generation unit for generating subfield coding so that subfield coding of a gray level having a gray level greater than an odd gray level is the same for all bits except the bit having the least weight and the subfield coding of the odd subscale ; If the gray level regulator detects an even number, the subfield generated by the first subfield generator is selected, and if the gray level regulator detects an odd number, the gray level is generated by the second subfield generator. A subfield selector for selecting a subfield to generate a subfield, The first gradation is a subfield coding generated by the first subfield generator and the subfield coding generated by the second subfield generator is a different subfield coding in a subfield having a large weight. The subfield selector selects the same subfield coding regardless of whether the integer part of the gamma corrected gray level is even or odd. The method of claim 6, The subfield weight array for subfield coding generated by the first subfield generator and the second subfield selector is a subfield weight array in which a subfield having a minimum gray scale weight is two or more. Driving device. The method according to claim 6 or 7, And wherein the weighted subfield is the weighted subfield among the subfields that should be turned on to express the grayscale in the subfield coding generated for the gamma corrected grayscale. The method according to claim 6 or 7, The subfield selected by the subfield selector may select a subfield generated by the second subfield generator even when the integer part of the gamma corrected grayscale is an even number with respect to the first grayscale. Driving device of the plasma display panel. The method according to claim 6 or 7, And an error diffusion unit configured to error-diffuse the gamma corrected data.