KR20040047541A - Driving circuit of plasma display - Google Patents

Abstract

PURPOSE: A circuit for driving a plasma display is provided to perform the detection of the moving by using a small amount of memory in comparison with a conventional circuit. CONSTITUTION: A circuit for driving a plasma display includes a signal converter(1) and a false contour processing block. The signal converter(1) generates a lighting pattern for use in a lighting/non-lighting control of each of the sub-fields from the degree of gray level of the inputted image signals. And, the false contour processing block detects the image among the still image or the dynamic image by comparing the changes of the lighting pattern before and after and processing the false contour suppression by adjusting the lighting and non-lighting of the predetermined sub-fields in the lighting pattern when the dynamic image is detected.

Description

Plasma Display Driver Circuit {DRIVING CIRCUIT OF PLASMA DISPLAY}

The present invention relates to a plasma display driving circuit for driving a plasma display panel (PDP).

In recent years, PDPs have been improved in image quality such as brightness and contrast, and are widely used as large-screen flat panel displays.

In such a PDP, the AC type PDP generally uses a subfield method for controlling the lighting of pixels to express gray scales.

However, the subfield method is known to be easy to generate pseudo contours in principle.

4 and 5, the generation of the pseudo contour will be briefly described.

In Fig. 4A, since there is an address setting period for selecting a pixel that is originally lit, the sustain (lighting duration) period is not continuous as shown in Fig. 6, but the address setting period is omitted here for the sake of simplicity. It is.

In the figure, in the sustain signal for driving each pixel in the sustain period of each subfield, the intensity (pulse voltage) of each sustain signal is the same and the amount of light emitted per hour is equal, so that the time width (pulse width) is controlled to show the gray scale. do.

Accordingly, in the retina of the human eye, the intermittent light emission of FIG. 4 (a) is integrated as time and appears as the luminance state shown in FIG. 4 (b), so that the longer the light emission time (the total value of the sustain period) is, The amount of integration increases and the screen looks bright. In this way, gradation expression by subfields is performed.

Therefore, as shown in Fig. 4A, the luminance (vertical axis direction) by each sustain signal is the same as each subfield.

And the horizontal axis | shaft of (a), (b), (c) of FIG. 4 has shown time.

As described above, even in gradation 127 or gradation 128 or all the other gradations, for example, even if it is intermittent luminescence as long as the emission scheme is repeatedly performed when each image is a still image, By the integration effect, normal gradation control is performed.

On the other hand, when the image is a moving image, as shown in Fig. 5, when the object A of 128 gradations moves in the background of 127 gradations, that is, the front portion B changes from 127 gradations to 128 gradations. When the object A moves (rightward) such that the rear portion C changes from 128 gray scales to 127 gray scales, a pseudo contour occurs.

That is, as shown in Fig. 4A, in the front portion B that changes from light emission of gradation 127 to light emission of gradation 128. The non-emission time T2 of the pixel becomes longer than the non-emission time T1 of the pixel that changes from gradation 127 to gradation 127.

For this reason, in the period of 3F (field) of FIG. 4B, the amount of irritation on the retina at time T2 is significantly reduced compared to time T1. Therefore, as shown in Fig. 3C, in the sensitivity of the human eye, the luminance at the front portion B, which changes from gray scale 127 to gray scale 128, appears to be lower than the actual gray scale.

As a result, dark portions (pseudocontours) occur in the front portion B of the moving object A. FIG.

On the contrary, in the rear part C, since the period of substantially no light emission becomes very short when the gray level is changed from the gray level 128 to the gray level 127, that is, since the light emission period is adjacent, the amount of stimulation on the retina increases and the luminance is higher than that of the actual gray level. It increases in appearance.

As described above, the gradation 128 and the gradation 127 are actually only one gradation, but are perceived by the human eye as a large luminance difference compared to the actual gradation difference, so that a pseudo contour occurs and the quality of the moving image is deteriorated.

As a method of preventing the generation of such pseudo contours, as shown in Fig. 7, there is a configuration in which the gray scale of the moving picture portion is compensated by adaptively switching the coding method in accordance with the detection result by using motion detection. Patent Document 1).

That is, the comparison unit 101 compares the pixels of the immediately preceding field stored in the memory 100 with the pixels of the input field, obtains the difference between the gray levels of the pixels, and detects that the pixels are changing when the difference is confirmed. It is determined as a fairy tale.

The gradation number control unit 102 converts the gradation of the input image into a gradation of continuous light emission scheme as shown in FIG. 8 and outputs the gradation.

Then, the switching unit 103 outputs the gradation degree input in the case of a still image to the driving circuit of the PDP as it is by the control signal from the comparing unit 101, and the gradation number converted in the gradation number control unit 102 in the case of moving pictures. The figure is output to the drive circuit of the PDP.

At this time, in order to recover the gradation in the moving picture portion, an image compensation such as an error diffusion loop is performed by using a coefficient circuit or a delay circuit.

Non-Patent Document 1

Kawahara Isao, Sekimoto Kunio, "Development of Fairy Tale Contour Suppression for Fixed-PDP," 2000 Korean Society for Visual Information Media, Lecture Manuscript, pp.369-370

In such a conventional example, it is necessary to compare images on a field-by-field basis, so that the pseudo image can be effectively suppressed by detecting (moving) the light emission scheme of the pixels at the same position in the immediately preceding field.

However, the conventional example requires a storage capacity for storing a video signal (gradation degree) of one field in order to detect a light emission scheme, and requires a storage element for satisfying the storage capacity.

In recent years, miniaturization and high resolution of display images in displays have progressed, and the amount of data in one field has increased, and the storage capacity needs to increase accordingly.

Increasing the capacity of the memory element (memory) to be mounted causes a direct increase in product cost compared to a product that does not perform the comparison process between the fields.

In the conventional example, in the case of detecting motion, the pseudo contour suppression effect can be obtained by performing motion detection in a plurality of fields instead of motion detection between front and rear fields, but the required storage capacity also increases. .

The present invention provides a plasma display driving circuit capable of detecting motion with a smaller storage capacity than in the prior art.

1 is a block diagram showing a configuration example of a plasma display driving circuit according to an embodiment of the present invention.

FIG. 2 is an example of a table showing a block configuration in which the block converting section 2 of FIG. 1 classifies each lighting pattern.

3 is a timing chart illustrating an operation example of the plasma display driving circuit of FIG. 1.

4 is a timing chart showing an operation example of the plasma display driving circuit in the conventional example.

5 is a conceptual diagram showing the concept of generation of pseudo contours in a moving image.

6 is a conceptual diagram illustrating a field configuration of a subfield method.

7 is a block diagram showing a configuration example of a plasma display driving circuit according to the prior art.

8 is a conceptual diagram showing the configuration of a lighting pattern of a subfield for explaining suppression of pseudo contour according to the conventional example.

<Brief description of the symbols in the drawings>

1: signal converter, 2: block converter, 3: memory

4: comparison unit, 5: pattern control unit

A plasma display driving circuit according to the present invention is a plasma display driving circuit which divides one field into a plurality of subfields and performs gradation expression by lighting / non-lighting control of emission of each subfield. A signal converter which generates a lighting pattern used for lighting / non-lighting control of the respective subfields from the gradation diagram of the subfields is compared with a change in the lighting pattern before and after the image to detect whether the video is a still image or a moving image. Is a pseudo contour processing unit (block conversion unit, memory, comparison unit, pattern control unit) for performing pseudo contour suppression processing by adjusting the light emission and non-emission of a predetermined subfield in the lighting pattern. .

In the plasma display driving circuit according to the present invention, the pseudo contour processing unit classifies the lighting pattern corresponding to each gradation degree into a plurality of blocks according to a predetermined rule, and determines the block number of the block in which the input gradation degree is classified. It characterized by having a block conversion unit for outputting.

The plasma display driving circuit according to the present invention is characterized in that the pseudo contour processing unit has a storage unit that stores the block number in association with each pixel of one frame.

In the plasma display driving circuit according to the present invention, the pseudo contour processing unit compares a block number stored in the storage unit with a block number generated from an input video signal for each pixel, and performs motion detection for determining whether to move or not. It is characterized by having a wealth.

The plasma display driving circuit according to the present invention includes a pattern control section in which a pseudo contour processing section controls light emission and non-light emission of a subfield at a predetermined position in the field in response to a comparison result output from the comparison section. It is characterized by.

The present invention divides one field shown in FIG. 6 into a plurality of subfields as described in the conventional example, and expresses the gradation representation of each pixel in the frame by lighting / non-lighting control of light emission of each subfield. The present invention relates to a plasma display driving circuit.

In addition, the plasma display driving circuit according to the present invention relates to a plasma display driving circuit for an AC type PDP, and in particular, blocks the lighting pattern of each gradation level according to a predetermined rule and generates a change between the blocks, that is, a pseudo contour. It is the structure which detects only the lighting pattern change which it is easy to make.

Accordingly, the plasma display driving circuit according to the present invention performs motion detection for determining whether the gradation of each pixel of the video signal has changed, that is, detecting the change in the gradation of the pixel corresponding to the before and after frame image. This is done by comparing the block numbers that contain the gradation diagram, not by comparing. Therefore, the memory capacity for storing data for comparison of each pixel of the frame image is greatly reduced as compared with the conventional example.

The plasma display driving circuit according to the present invention performs motion detection in units of pixels as described above, and based on the result of the motion detection, adjusts the gray level of the detected pixel and adjusts the pseudo outline in the frame image. It has a function to perform a suppression process (pseudo contour suppression process).

Here, in one frame, when a change in the gradation degree (block number) is detected in a pixel, the pixel becomes a moving image part when the motion is detected, and when the change in the gradation degree (block number) is not detected in the pixel, The pixel becomes a still picture part because no motion is detected.

EMBODIMENT OF THE INVENTION Hereinafter, the Example of this invention is described with reference to drawings. 1 is a block diagram showing a configuration example of a plasma display driving circuit according to an embodiment of the present invention.

In this figure, the signal converter 1 corresponds to the gradation level (display gradation) for each pixel of an input video signal (e.g., digital data of RGB (using three primary colors of red, green, and blue)). Then, a lighting pattern used for lighting / non-lighting control of each subfield is generated in accordance with a conversion process using a lookup table or the like.

That is, the signal converter 1 converts the gradation of each pixel of the input video signal into the lighting pattern shown in the table of FIG.

Fig. 2 shows the relationship between the lighting pattern which shows the combination of the gray scale actually displayed and 256 sub-fields which are actually displayed at the time of 256 gray scale display.

That is, the signal converter 1 converts the gradation degree into a lighting pattern for controlling lighting / non-lighting according to the combination of each subfield having a different lighting period as shown in FIG.

In FIG. 2, the larger the number of the subfield is, the higher the gradation is.

The block conversion unit 2 classifies the lighting pattern, which is converted in correspondence with the gradation degree for each pixel in frame units (display screen units), into a plurality of blocks as shown in FIG. 2 according to a predetermined rule. The block converting section 2 outputs the block number of the block to which the lighting pattern is classified for each lighting pattern, and stores the block number in the memory 3 in association with each pixel.

For this reason, the lighting pattern is classified into the several block by the block conversion part 2 based on the said predetermined rule as shown in FIG.

For example, in the example of FIG. 2, the change point of the subfield with high gradation is used as a division | segmentation of each block in the lighting pattern which shows 256 gradations.

That is, in Fig. 2, in each subfield that is in the lighting state in the lighting pattern representing the gradation degree, each block pattern is classified according to the subfield with the longest lighting period (the subfield with the high gradation degree). Is set.

For this reason, in each lighting pattern of FIG. 2, the block 0 is comprised by the gradation degree 0,1 to which subfield number 1 is lit.

Block 1 indicates that subfield No. 2 is lit as the subfield of the highest gradation degree (gradations 2 and 3).

Block 2 indicates that subfield No. 3 is lit as the subfield of the highest gradation degree (gradations 4 to 7).

Block 3 indicates that subfield No. 4 is lit (the gradations 8 to 15) as the subfield of the highest gradation degree.

Block 4 indicates that subfield No. 5 is lit as the subfield of the highest gradation degree (gradations 16 to 31).

Block 5 shows that subfield No. 6 is lit as the subfield of the highest gradation degree (gradations 32 to 63).

Block 6 indicates that subfield No. 7 is lit as the subfield of the highest gradation degree (gradation degrees 64 to 127).

Block 7 indicates that the subfield No. 8 is lit as the subfield of the highest gradation degree (gradation degree 128 to 255).

The classification of FIG. 2 is an example, and which lighting pattern is used as a short circuit of each block, to what extent is the range of lighting patterns included in each block, and how many blocks (classification numbers) classify lighting patterns? The haze is arbitrarily determined according to the conditions such as the degree of suppression processing of pseudo contour and the resolution / gradation degree.

The comparator 4 is a block number of a lighting pattern of each pixel of a previously input frame (for example, the previous frame or every other one) stored in the memory 3 and each pixel of the input frame. The block number of the lighting pattern generated from the video signal of D is compared for each pixel, and motion detection is performed to determine whether the gray level has changed (either the moving image portion or the still image portion).

For example, the comparing unit 4 compares the block number of the lighting pattern generated from the video signal of each pixel of the input frame with the immediately preceding frame stored in the memory 3, so as to compare each pixel of the front and rear frames. Since the block numbers can be compared, the effect of the pseudo contour suppression process is improved.

In addition, the comparator 4 outputs a control signal to the pattern control unit 5 instructing the change of the gradation degree of each pixel in correspondence to which block the movement between blocks in the lighting pattern is performed.

As shown in the timing chart of FIG. 3, the pattern control unit 5 adjusts the gradation degree of each pixel to the PDP according to the control signal corresponding to the comparison result of the comparison unit 4. It outputs, light emission and non-emission control of the subfield of a predetermined position in a field are performed, and an image display is performed by driving a PDP.

Next, an operation example of the plasma display driving circuit according to the embodiment of the present invention will be described with reference to FIGS. 1 and 3.

In the timing chart of Fig. 3, the vertical axis represents luminance and the horizontal axis represents time. In reality, although an address setting period precedes each subfield, it is omitted as shown in Fig. 4A.

The signal converter 1 converts the gradation of each pixel of the input video signal into a lighting pattern and outputs the lighting pattern to the block converter 2.

For example, the video signal is an RGB digital signal, and three primary colors of red, green, and blue are each displayed in 256 gray levels, and if the data amount is 8 bits each, a total of 24 bits signals are input.

For this reason, the signal converter 1 separates the RGB-type video signal input by 24 bits into 8 bits of red, green, and blue, respectively, and outputs the gray level of each primary color as a lighting pattern to the block converter 2, respectively. do.

The block converting section 2 classifies the lighting patterns of the input three primary colors into the blocks shown in Fig. 2 for each primary color, respectively.

Next, the block converting section 2 stores the block numbers of the blocks of the primary colors classified for each lighting pattern in the memory 3 for each of the primary colors and outputs the block numbers of the primary colors to the comparison section 4.

Here, in FIG. 2, the blocks are made of eight types of blocks 0 to 7, so that the block numbers of the primary colors can be represented by 3 bits, respectively. Therefore, the block converter 2 stores 9-bit block number data in the memory 3 and outputs it to the comparator 4.

As a result, the comparison unit 4 independently compares the lighting pattern inputted with the lighting pattern of the immediately preceding frame read out from the memory 3, that is, the block number of the front and rear fields, independently for every three primary colors.

At this time, every time each of the three primary colors, the comparison unit 4 reads the block number of the lighting pattern for comparison from the memory 3, the block converting unit 2 in turn blocks the block number of the lighting pattern of the pixel at the corresponding position. Overwrite the block number of the converted lighting pattern.

As a result, the block number of the lighting pattern of each new frame is stored in the memory 3 each time a comparison is made.

Hereinafter, since the same operation is performed for each of the three primary colors, the kind of the primary colors is not shown, but the same processing is performed for all three primary colors.

For example, in the timing chart of FIG. 3, when the transition from the 2F (field) th of the gradation 127 to the 3F th of the gradation 128 is performed, the non-illumination period occurs even if the gradation is almost the same as described in the conventional example. As it becomes longer, the decrease in gradation is felt in the human eye.

For this reason, as shown in (c) of FIG. 4, it is necessary to prevent the substantially gray level from decreasing so that the front portion B of the object A of FIG. 5 becomes a dark pseudo outline.

Here, the comparing unit 4 compares the block number (block 6) of the memory 3 with the block number (block 7) output from the block converting unit 2. When the comparison unit 4 determines that the non-lighting period between the fields is long, that is, when it detects that the gray level is changed from block 6 (gradation 127) to block 7 (gradation 128), the control signal is patterned. Output to the control part 5 is carried out. This control signal is a signal for instructing a process of inserting a subfield to be newly lit in the lighting pattern so as to light the subfield at a predetermined position in the subfields of the 2F th and 3F th non-lighting periods.

As a result, the pattern control unit 5 adjusts the gradation so as to light any one subfield as a predetermined subfield between the subfields 1 to 7 when shifting from the 2F (field) th to the 3F th described above. (Add pulse in non-lighting period). The pattern control unit 5 outputs the adjusted gradation image signal (RGB system image signal) to the PDP to control light emission and non-emission of the subfield at a predetermined position in the field, and to drive the PDP. Display an image.

As a result, even in the case of changing from gradation 127 to gradation 128, the presence of a subfield that lights up in a long non-lighting period can reduce the decrease in the amount of stimulation on the human retina in time integration. Therefore, since the gradation is not substantially lowered (the luminance felt by human beings is lowered) as in the conventional example, the pseudo contour can be suppressed in the present invention.

On the other hand, in the timing chart of Fig. 3, when transitioning from the 3F th of the gradation 128 to the 4F th gradation of the gradation 127 (when it is detected that the gradation of the pixel is changed by the motion detection), as described in the conventional example Even with the same gradation level, the non-lighting period is extremely short, so the gradation level is felt high in the human eye.

As a result, the amount of stimulation caused by temporal integration is increased, the actual gray level (luminance felt by human being) is increased, and it is necessary to prevent the rear portion C of the object A of FIG. 5 from becoming a bright pseudo contour.

Here, the comparing unit 4 compares the block number "block 7" of the memory 3 with the block number "block 6" output from the block converting unit 2. When the comparison unit 4 determines that the non-illumination period between the fields is shorter than the predetermined period, that is, when the gradation degree is changed from block 7 (gradation degree 128) to block 6 (gradation degree 127), the control signal is returned. Output to the pattern control part 5 is carried out. This control signal removes the subfields to be lit from the lighting pattern (non-lighting any of the lit subfields) so as to make the subfields of the predetermined positions in the subfields of the 3F th and 4F th lighting periods non-lit. Is a signal for processing.

Accordingly, when the pattern control section 5 shifts from the 3F th to the 4 th th mentioned above, the pattern control section 5 performs a process of removing any subfield among the subfields 1 to 7 to make the predetermined subfield non-lighting, The tone is adjusted in the lighting pattern. The pattern control unit 5 outputs the adjusted gradation image signal to a PDP (not shown), controls light emission and non-emission of a subfield at a predetermined position in the field, and drives the PDP to display an image. do.

As a result, even when the gray level is changed from the gray level 128 to the gray level 127, the non-lighting subfield is present in the continuously lit subfields, thereby increasing the amount of stimulation on the human retina in time integration. Therefore, since the gray scale does not substantially increase as in the conventional example, the pseudo contour can be suppressed in the present invention.

When the comparison unit 4 detects that the block number &quot; block 6 &quot; does not change when transitioning from the 1F th to the 2F th as in Fig. 3, i.e., detects that the pixel is not detected motion, A control signal indicating that the figure is not adjusted is output to the pattern control unit 5.

Accordingly, the pattern control unit 5 outputs to the PDP without adjusting the gradation of each pixel of the input video signal.

By independently performing the above-described processing on all three primary colors, the gradation of the human retina is greatly changed due to the characteristics of the subfield system, but the gradation of the human retina is greatly changed by the characteristics of the subfield system. It is possible to suppress pseudo contours.

In addition, the pattern converting unit 2 and the comparing unit 4 may use either a circuit configuration for parallel processing of three primary colors or a circuit configuration for sequentially time series processing as one circuit depending on the processing speed or the limitation of the circuit scale. It is available.

As described above, assuming that the video signal used for motion detection is RGB data, each of 256 gray levels (8 bits) (3 × 8 bits = 24 bits), and the resolution is VGA (640 × 480). Conventionally, a total memory capacity of 24 (bits) x 640 x 480 = 7722800 (bits) is required.

However, in the embodiment of the present invention, since 8 types of blocks (3 bits are required to identify 8 types of blocks 0 to 7) as data of the RGB method (all 3x3 bits = 9 bits), the resolution is conventionally known. If VGA is used as in the example, a total of 9 (bits) x 640 x 480 = 2764800 (bits) of storage capacity is required, so a conventional 37.5% of memory capacity is required.

Accordingly, the plasma display driving circuit according to the embodiment of the present invention can greatly reduce the capacity of the memory of the circuit for performing motion detection and can reduce the cost of the entire circuit.

In addition, the plasma display driving circuit according to the embodiment of the present invention performs the motion detection in the comparing section 4 by comparing (case comparison) the block numbers for respective pixels in the front and rear frames. Therefore, as in the conventional method, the rounding up or down is not individually detected in each bit unit of the gradation level, and the comparison itself can be used as a control signal. For the purpose of suppressing pseudo contours, the pattern control unit 5 can easily and accurately adjust the lighting pattern, that is, the insertion of the lighting subfield and the setting of the non-lighting subfield for the gray scale.

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, when the motion detection is performed for suppressing the pseudo contour, the difference in the gradation degree of the pixel at the corresponding position is not used between the frames before and after the conventional motion detection method. Since motion detection is performed by the block number of the block which classifies the lighting pattern, it is not necessary to store the gradation level for each pixel in the frame unit. Therefore, it becomes possible to provide a plasma display driving circuit which can perform motion detection with a smaller storage capacity than the conventional example.

Claims (5)

A plasma display driving circuit which divides one field into a plurality of subfields and expresses a gray scale by lighting / non-lighting control of light emission of each subfield. A signal conversion unit for generating a lighting pattern used for lighting / non-lighting control of the respective subfields from the gradation diagram of the input video signal, and By comparing the changes in the lighting patterns before and after, detecting whether the video is a still image or a moving image, and when detecting the moving image, adjusts the emission and non-emission of a predetermined subfield in the lighting pattern to suppress pseudo contour. Pseudocontour processing unit to process Plasma display driving circuit comprising a. The method of claim 1, The pseudo contour processing unit, And a block converting unit for classifying the lighting pattern corresponding to each gray level into a plurality of blocks according to a predetermined rule, and outputting a block number of a block in which the input gray level is classified. The method of claim 2, And the pseudo contour processing unit further includes a storage unit for storing the block number corresponding to each pixel of one frame. The method of claim 3, The pseudo contour processing unit, And a comparison unit for comparing the block number stored in the storage unit with the block number generated from the input video signal for each pixel and performing motion detection for judging moving images. In accordance with claim 4, The pseudo contour processing unit, And a pattern control unit for controlling light emission and non-emission of the subfield at a predetermined position in the field, in response to a comparison result output by the comparison unit.