KR20100125937A - Methods for driving a plasma display panel and apparatus thereof - Google Patents

Abstract

PURPOSE: A method for driving a plasma display panel and an apparatus thereof are provided to reduce power consumption by preventing unnecessary sustain voltage from being supplied for one frame. CONSTITUTION: A frame includes a plurality of subfields. An image signal is mapped to the sub-fields(S100). The sustain signal is assigned to a plurality of sub-fields. The number of the sustain signal is reduced based on the maximum gradation of image signal(S200). The maximum gradation of the image signal is adjusted to a first set value which is varied according to a modified value. The modified value is difference between a real gradation and the first set value.

Description

A method for driving a plasma display panel and a device thereof {Methods for driving a plasma display panel and Apparatus}

The present invention relates to a method of driving a plasma display panel and a device thereof which reduce power consumption.

The plasma display panel is a display element in which vacuum ultraviolet rays emitted from a plasma formed by gas discharge excite phosphors, and display a screen by using visible light generated at this time. The plasma display panel has a high resolution and large screen configuration, and has been in the spotlight as the next generation flat panel display device.

In the plasma display panel, millions of unit discharge cells are arranged in a matrix form. The discharge cells select the discharge cells that are turned on and the discharge cells that are not turned on by using the memory characteristics of the wall charges, and display the screen by discharging the selected discharge cells.

When driving such a plasma display panel, an average power level (APL) is used to reduce power consumption. 1 is a view for explaining the APL.

APL adjusts the number of sustain signals per frame in consideration of power consumption. In the direction of increasing power consumption, the number of sustain signals per gray level is reduced, and in the direction of decreasing power consumption, the number of sustain signals per gray level is increased.

For example, when the screen is displayed in a small area as shown in (a), since the power consumption is relatively small, the number of sustain signals per gray level is relatively high. Then, the overall brightness of the screen is increased.

On the contrary, when the image is displayed in a large area as shown in (b), since the power consumption is relatively high, the number of sustain signals per gray level is relatively small. This prevents excessive power consumption.

In this way, the number of sustains for each frame is pre-assigned according to the APL. When driving the plasma display panel, a required frame is selected and subfield mapping is performed on the image signal.

However, in the conventional driving method, despite this APL, the sustain voltage is applied to all the discharge cells regardless of whether the discharge cells are turned on or off in the sustain period of all the subfields belonging to one frame. In such a case, since the sustain voltage is applied even in a subfield not used for one frame, there is a problem that power consumption is unnecessarily increased.

The present invention has been proposed in this technical background, and is to reduce power consumption by preventing a sustain voltage from being applied unnecessarily for one frame.

According to an embodiment of the present invention, in a method of driving a plasma display panel displaying an image in units of frames including a plurality of subfields, an average power level (APL) of an image signal is provided. Mapping an image signal to a plurality of subfields with reference to reducing the number of sustain signals allocated to the mapped plurality of subfields with reference to the maximum gray scale of the video signal, and reducing the maximum gray scale of the video signal. And adjusting the first set value to a reference value, wherein the first set value changes with reference to a change value which is a difference between the actual gray level and the first set value.

When the maximum change value of the change values is smaller than the second set value, it is preferable to adjust the first set value so that the maximum change value is equal to the second set value.

The maximum gradation of the frame is 1024, and the gradation range according to the second setting value is 200.

In the adjusting to the first set value, the number of sustain signals allocated to the mapped plurality of subfields is rearranged in each subfield by a value obtained by dividing the gain by the gain, and the gain is the maximum gray level of the image signal. It may be defined as the ratio (G-max / g-max) of the maximum gray scale weight G-max of the allocated frame to (g-max).

In the adjusting of the first set value, the number of the image data may be increased by multiplying the gain by the image data corresponding to the image signal.

Another embodiment of the present invention includes an electrode, a plasma display panel displaying an image in units of frames including a plurality of subfields, and a controller for supplying a driving signal to the electrodes. The controller maps an image signal to a plurality of subfields with reference to an average power level (APL) of the image signal, and assigns the image signal to the mapped plurality of subfields with reference to a maximum gray scale of the image signal. The number of sustain signals is reduced, and the maximum gray level of the video signal is adjusted to a first set value, and the first set value is a change value which is a difference between an actual gray level and the first set value to be less than or equal to the first set value. The present invention provides a plasma display apparatus which changes with reference to a changed value of pixels.

According to an embodiment of the present invention, since all the subfields are turned on by rearranging the number of the sustain signals for each subfield mapped according to the APL with reference to the maximum gray scale of the video signal, the number of the invalid sustain signals is reduced. Improve the efficiency.

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 can 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.

The driving method of the present invention includes mapping a video signal to subfields according to APL, and then rearranging the number of sustains per subfield with reference to the maximum gray level of the video signal. 2 illustrates a process of rearranging the number of sustains for each subfield according to the maximum gray level of a dual image signal.

In operation S611, it is determined whether the maximum gray level g-max of the video signal is smaller than the maximum gray level G-max of the mapped frame.

As a result, when the maximum gray level g-max of the video signal is smaller than the maximum gray level G-max of the mapped frame, the number of sustains for each subfield is rearranged with reference to the maximum gray level of the video signal (S612). Here, the rearrangement is performed in a direction of decreasing the number of allocated sustain signals.

On the other hand, if the maximum gray level g-max of the video signal is substantially the same as the maximum gray level G-max of the mapped frame, the step ends.

On the other hand, when the maximum gray level g-max of the video signal is greater than the maximum gray level G-max of the frame in step S611, the maximum gray level g-max of the video signal is the maximum gray level G- of the frame. There is no need to judge because it cannot be greater than max).

In this driving method, a process of actually displaying the screen illustrated in FIG. 3 will be described. The screen illustrated in FIG. 3 is a night image and assumes that the APL is 40 levels. In addition, it is assumed that subfields are mapped according to APL as shown in FIG. In FIG. 4 and the following description, the number of sustains for each subfield is illustrated as being equal to the gray scale weight.

Since the screen is an image of the night, it corresponds to a low gray level, and the gray level of the sky 800 is the brightest, and the gray level of a subject such as another mountain or cloud is lower than the gray level of the sky 800. Therefore, the maximum gradation of the screen is 127 gradations of the sky. The number of sustain signals allocated to one frame (or gray scale weight) is 2, 4, 8, and 16 from the first subfield SF1 to the eighth subfield SF8, respectively, as shown in FIG. , 32, 64, 128, 256.

Here, since the maximum gray level g-max of the video signal is 127 gray levels, the first to seventh subfields are turned on and the eighth subfield is turned off.

On the other hand, the maximum gray level of the subfields belonging to this frame is 256. Therefore, in this case, the maximum gray level g-max of the video signal, that is, the video signal is smaller than the maximum gray level G-max of the mapped frame.

In this case, as shown in (b) of FIG. 4, the number of the sustain signals allocated to the plurality of subfields is respectively 1, 2, 4, 8, 16, from the first subfield SF1 to the eighth subfield SF8. Rearrange to 32, 64, 128. That is, the number of sustains allocated to each subfield of the mapped frame (FIG. 4A) is rearranged by a value obtained by dividing the gain (G-max / g-max). This rearrangement may be performed based on the APL. Since the maximum gray level of the image signal is 127 gray levels, the number of sustained sub-fields is re-mapped by remapping the frames having the gray scale weight of 127 (or similar) in the last subfield. Can be arranged.

As a result, as shown in (a) of FIG. 4, the first subfield SF1 to the seventh subfield SF7 are turned on to implement 127 gray levels of the video signal, and the eighth subfield SF8 is turned off. Unlike the above, after rearranging, all subfields from the first subfield to the eighth subfield are turned on as shown in (b) of FIG. 4 to express the same gray level. Accordingly, the numbers of the sustain signals which generate sustain discharge are substantially the same in Figs. 4A and 4B. Therefore, while FIG. 4 (a) and (b) can realize substantially the same image, the sub-fields are turned on (on) as a result of the rearrangement, thereby reducing the reactive power consumption.

When comparing (a) and (b) of FIG. 4, in FIG. 4A, an off subfield may exist according to the maximum gray level g-max of an image signal like the eighth subfield. In FIG. 4A, 256 sustain signals are allocated to the eighth subfield SF8, which is an invalid sustain signal that does not cause sustain discharge. As a result, the reactive power consumption increases.

On the other hand, in (b) of FIG. 4, since all gains are turned on from the first subfield to the eighth subfield by increasing the gain compared to the case of (a) of FIG. While it is possible to realize substantially the same image as, the power efficiency can be improved by reducing the number of invalid sustain signals.

Here, when the number of the assigned sustain signals of (a) and (b) of FIG. 4 is compared, the total number of the sustain signals allocated to (a) of FIG. 4 is approximately 512, and it is allocated from (b) of FIG. The total number of sustain signals is approximately 256, and it can be seen that the number of sustain signals decreases at a ratio of g-max / G-max.

In addition, when the gains of FIGS. 4A and 4B are compared, the gradation implemented in FIG. 3A is about 127 gradations, and the gradation implemented in FIG. 4B is about 256 gradations. It can be seen that the gain increases at the ratio of G-max / g-max.

In the above description, the driving method of the present invention has been described by exemplifying a case where high gradation is not included in the screen. Hereinafter, a case where high gradation is included in the screen will be described.

5 shows a screen including a high gradation screen in a portion of the low gradation screen and a histogram thereof. The histogram is the frequency of each gray level.

Referring to FIG. 5, in the histogram, most of the gray scales are distributed below C, but some have a frequency of B gray scales. A gray scale corresponds to the window 910 of the house 900 of the screen, and (a) is the maximum gray scale on the screen. Accordingly, the gray level of the sky 800 and other subjects is low, whereas the gray level of the window 910 among the subjects is excessively high compared to the gray levels of the sky 800 and other subjects. In this case, the histogram of the frame with respect to the screen of (a) is sufficiently high in the gradations of the sky 800 and other subjects, that is, the gradations of 0 to C, as shown in (b), and the gradations of the window 910, ie, A The frequency of gradation is very low.

In this case, if the gray level of the window 910 is set to the maximum value of the histogram because the area of the window 910 is very small compared to other parts, the reactive power may increase by increasing the number of subfields that are turned off. Therefore, in order to reduce consumption of reactive power, the maximum gradation of this screen (a) is set to B gradation lower than A gradation.

However, lowering the maximum gradation may degrade the screen quality. In addition, as the maximum gradation is lowered much, the effect of reducing power consumption is greater, but the quality is deteriorated in proportion.

On the other hand, when the gradation is displayed lower than the original, when there is a change in the gradation within a certain range, deterioration of the image quality is hardly recognized by the human eye. For example, when the 1000 gray levels are lowered to 850, which is the first set value (the maximum value that can be displayed by lowering the gray scales), and when the 900 gray levels are lowered to the first set value, 750, the gray level is correlated with the gray scales. Without both, the actual gradation changes in the same range (150 gradations), so both are not well perceived degradation of image quality.

On the other hand, when the gray scale is lowered to 750, which is the first set value, the deterioration of the image quality is recognized better than the above example because the change range of the gray scale (250 gray scale) is larger than the above example. As a result, it can be seen that deterioration of image quality is well recognized when the change range of the gray scale, i.e., the difference between the actual gray scale and the first set value (hereinafter referred to as the second set value) exceeds the threshold. Experimentally, when expressing 1024 gray scales, the threshold of the second set value is 200. Therefore, the deterioration of the image quality is well recognized by the human eye when the second set value exceeds 200.

In such a background, it is preferable to change and set a 1st setting value according to a 2nd setting value. That is, if the change range of gray level by pixel is large, the first set value is increased to reduce the range of gray level change so that degradation of image quality is not recognized or when the change range of gray level by pixel is small, the first set value is lowered. Effectively reduce the power consumption.

6 and 7 illustrate screens corresponding to video signals constituting one frame in order to explain a method of correcting a first set value on the screen. The screen of FIG. 6 shows a case where the gray scale change is small, and FIG. 7 illustrates a case where the gray scale change of the screen is large.

The screen illustrated in FIG. 6 is a screen showing stars evenly floating in the entire night sky. Therefore, the night sky corresponds to the low gradation, but the star is a saturated region because it is relatively brighter than the night sky. That is, the gradation of pixels belonging to the saturation region is fixed to the maximum gradation of the frame.

Therefore, according to the driving method described above, the actual gray level of the pixels belonging to the saturation region is lowered to the first setting value and displayed. For example, assuming that the first setting value for the screen illustrated in FIG. 6 is 800, the actual gray level of the pixels belonging to the saturation region is 950, and the second setting value is 200, Since the difference (950-800) (hereinafter, the changed value) is 150, the actual gray level 950 is lowered to 800 to be displayed. By the way, since the second set value is 200, the first set value is lowered from 800 to 750 for this screen, so that the difference between the actual gradation and the first set value is equal to the second set value.

As described above, in the screen of FIG. 6, the first setting value is lowered to 750, which is a range satisfying the change range of the gray scale from the previous 800, so that the degradation of image quality is not recognized but the number of sustains can be effectively reduced to reduce power consumption.

The screen illustrated in FIG. 7 shows that stars and moons are floating together in the night sky. Therefore, since the moon is relatively brighter than the stars, it becomes the maximum gray scale of this screen.

As in the condition of FIG. 6, if the first set value is 800, the second set value is 200, and the maximum gray level is 1050, the maximum gray level is lowered to the first set value and displayed. However, since the change value (1050-800) is 250, it is beyond the allowable change range of the gradation. In such a case, the first set value may be reset to 850 in accordance with the change range of the gradation to be reset, or the original first set value may be maintained as it is.

In the case of raising the first setting value, since the first setting value is adjusted according to the change range of the gradation, the deterioration of the screen is less than before the adjustment, while the first setting value is increased, so the number of sustain increases to increase the power consumption. Is increased. On the contrary, in the case where the first set value is maintained as it is, power consumption can be reduced, but the degradation of the screen is better recognized than after the adjustment.

As described above, the driving method of the present invention will be described with reference to the flowchart of FIG. 8 as follows.

In operation S100, the image signal is mapped to a plurality of subfields with reference to an average power level (APL) of the image signal.

In operation S200, the number of sustain signals allocated to the mapped plurality of subfields is reduced with reference to the maximum gray scale of the image signal. The number of sustain signals can be reduced by the value divided by gain, and the data of the video signal is preferably increased by multiplying the gain. The maximum gray level of the video signal is fixed to a preset reference value.

In operation S300, a difference value between each pixel is obtained by counting a difference between the actual gray level of the pixels belonging to the saturation region, that is, the pixel in which the actual gray level is changed to the first setting value, and the first setting value. Here, the change value is a difference between the actual gray level of the pixels changed to the first setting value and the first setting value. Accordingly, the change value of each pixel belonging to the saturated region is obtained, and the maximum value of the change value is extracted.

In step S400, it is determined whether the change value is smaller than the second set value, and if it is small, the process proceeds to step S500 to readjust the second set value so that the change value is equal to the second set value. On the other hand, if the change value is equal to or larger than the second set value, the step may be terminated, or the operation S500 may be performed as described above.

Hereinafter, a plasma display device according to the present invention will be described in more detail with reference to the accompanying drawings. The terms "module" and "unit" used in the following description are given only in consideration of ease of preparation of the specification and do not have distinct meanings from each other.

9 is a view for explaining in more detail the configuration of the plasma display device implementing the above-described driving method. Herein, the driver is divided into the scan electrode driver 460, the sustain electrode driver 470, and the data driver 465.

Referring to FIG. 8, the plasma display apparatus includes a memory unit 410, an APL calculator 415, a counting unit 417, a histogram generator 420, a controller 425, an inverse gamma correction unit 430, and a gain adjusting unit. 435, half toning unit 440, subfield mapping unit 445, data alignment unit 450, plasma display panel 100, scan electrode driver 460, data driver 465, and sustain electrode driver ( 470, a first signal generator 475, and a second signal generator 480. Reference numeral 485 corresponds to a remote control.

The memory unit 410 stores the first image signal input from the outside.

The APL calculator 415 calculates an APL from the first image signal. That is, the APL calculator 415 calculates an APL through image data corresponding to the first image signal stored in the memory unit 410.

Under the control of the controller 425, the counting unit 417 counts the difference between the actual gradation of the pixels whose actual gradation is changed to the first setting value and the first setting value, and obtains a change value for each pixel.

The histogram generator 420 counts the frequency of each grayscale value from the memory unit 410 through the image data corresponding to the first image signal and outputs the histogram data.

The controller 425 determines whether the maximum gray level g-max of the first image signal is smaller than the maximum gray level G-max of the mapped frame, and thus the maximum gray level g-max of the first image signal is determined. If it is smaller than the maximum gray level (G-max) of the mapped frame, the number of sustains for each subfield is rearranged with reference to the maximum gray level of the mapped frame. The controller 425 may re-assign the number of the sustain signals as a result of dividing the number of the sustain signals allocated according to the APL of the first video signal by the gain. The controller 425 determines whether the maximum change value of the pixel belonging to the saturation region is smaller than the second set value with reference to the calculation result of the counting unit 417. 2 Adjust the setting value to fix the gradation of pixels belonging to the saturation region to the readjusted second setting value.

The inverse gamma correction unit 430 performs inverse gamma correction on the first image signal.

The gain adjusting unit 435 multiplies the gain of the first image signal by the gain and outputs the second image signal. Here, the gain is defined as the ratio (G-max / g-max) of the maximum gray scale (G-max) of the mapped frame to the maximum gray scale (g-max) of the first image signal. The gain adjusting unit 435 may fix the maximum grayscale value of the second video signal to the reference value under the control of the controller 425, and may fix the grayscale value of the second video signal exceeding the reference value to the reference value. The reference value is varied according to the density provided by the density calculator 420.

The half toning unit 440 performs error diffusion and dithering on the second image signal.

The subfield mapping unit 445 outputs subfield mapping data for the second image signal by performing subfield mapping on the second image signal output from the half-toning unit 440.

The data alignment unit 450 receives subfield mapping data of the second image signal output through the subfield mapping unit 445 and rearranges the subfield mapping data for each subfield to output image data corresponding to the second image signal.

The scan electrode driver 460 supplies the scan electrode with a reset signal for uniformizing the wall charge state of the discharge cells in the reset period of the subfield under the control of the controller 425. In addition, the scan electrode driver 460 supplies a scan signal to the scan electrodes for selecting a discharge cell that is turned on in the address period of the subfield. In addition, the scan electrode driver 460 supplies the scan electrodes with the number of sustain signals allocated by the controller 425 in the sustain period of the subfield.

The data driver 465 supplies data pulses corresponding to the image data output from the data alignment unit 450 to the address electrodes in synchronization with the scan signal supplied by the scan electrode driver 460 during the address period. Select the cells.

The sustain electrode driver 470 supplies the number of sustain signals allocated by the controller 425 to the sustain electrode Z in the sustain period of the subfield.

The controller 425 may include an input unit (not shown) that receives a signal for changing gain, that is, a signal for requesting a change in gain. In this case, the input of the controller 425 may be a pin of the controller 425.

For example, the controller 425 may receive a signal for changing a gain from the first signal generator 475 including the keypad or the second signal generator 480 including the wireless signal receiver. That is, the first signal generator 475 outputs a first setting signal for setting the reference gray value or the gain to the controller 425.

The second signal generator 480 outputs a second setting signal for setting a reference gray value or gain to the controller 425. The second signal generator 480 outputs a second setting signal corresponding to the wireless signal received from the remote controller 485 to the controller 425.

The controller 425 receiving the setting signal output from at least one of the first signal generator 475 or the second signal generator 480 may update the reference gray value or the gain. For example, a user manipulates the first signal generator 475 or the remote controller 485 to set the reference gray value 120, and the first signal generator 475 sends the first set signal to the controller 425. The second signal generator 480 may receive a wireless signal and output the second set signal to the controller 425. The controller 425 updates the set reference gradation value 127 to 120, recalculates the gain according to the updated reference gradation value, and outputs it to the gain adjusting unit 435. The gain adjusting unit 435 may output the second image signal by multiplying the updated gain 2.5 by the first image signal.

For another example, when a user operates the first signal generator 475 or the remote controller 485 to set the gain 2.5, the first signal generator 475 sends the first set signal to the controller 425. The second signal generator 480 may receive a wireless signal and output the second set signal to the controller 425. The controller 425 may update the set gain 2 to 2.5 and output the gain 2 to the gain adjusting unit 435. The gain adjusting unit 435 may output the second image signal by multiplying the updated gain 2.5 by the first image signal.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, It will be understood that the invention may be practiced. Therefore, the embodiments described above are to be understood as illustrative and not restrictive in all aspects. In addition, the scope of the present invention is shown by the claims below, rather than the above detailed description. Also, it is to be construed that all changes or modifications derived from the meaning and scope of the claims and their equivalent concepts are included in the scope of the present invention.

1 is a view for explaining the APL.

2 is a diagram illustrating a process of rearranging the number of sustains for each subfield according to the maximum gray level of an image signal in the driving method of the present invention.

3 is a screen exemplified for explaining the driving method of the present invention.

4 is a diagram illustrating a subblock in which the video signal of FIG. 3 is mapped according to APL.

FIG. 5 is a diagram illustrating a screen including a high gradation screen in a portion of the low gradation screen and a histogram thereof.

6 and 7 are screens illustrated to explain the driving method of the present invention.

8 is a flow chart according to the driving method of the present invention.

9 is a block diagram schematically illustrating a configuration of a plasma display apparatus implementing the driving method of the present invention.

Claims (10)

A driving method of a plasma display panel for displaying an image in a frame unit including a plurality of subfields, Mapping the image signal to a plurality of subfields with reference to an average power level (APL) of the image signal; And, Reducing the number of sustain signals allocated to the mapped plurality of subfields with reference to the maximum gray scale of the video signal, and adjusting the maximum gray scale of the video signal to a first setting value; And the first setting value changes with reference to a change value which is a difference between an actual gray level and the first setting value. The method of claim 1, And adjusting the first set value such that the maximum change value is equal to the second set value when the maximum change value of the change values is smaller than the second set value. The method of claim 2, The maximum gray scale of the frame is 1024, the gray scale range according to the second set value is 200 driving method of the plasma display panel. The method according to any one of claims 1 to 3, In the adjusting to the first set value, the number of sustain signals allocated to the mapped plurality of subfields is rearranged in each subfield by a gain divided by a gain, and the gain is the maximum gray level of the image signal. A driving method of a plasma display panel defined by the ratio (G-max / g-max) of the maximum gray scale weight (G-max) of the allocated frame to (g-max). The method of claim 4, wherein And adjusting the first setting value to increase the number of the image data by multiplying the gain by the image data corresponding to the image signal. A plasma display panel displaying an image in units of frames including electrodes and a plurality of subfields; A controller for supplying a driving signal to the electrode, The controller, The image signal is mapped to a plurality of subfields with reference to an average power level (APL) of the image signal. Reduce the number of sustain signals allocated to the mapped plurality of subfields with reference to the maximum gray scale of the video signal, and adjust the maximum gray scale of the video signal to a first setting value; And the first setting value changes a change value, which is a difference between an actual gray scale and the first setting value, with reference to a change value of pixels adjusted to be equal to or less than the first setting value. The method of claim 6, And the controller adjusts the first set value such that the maximum change value is equal to the second set value when the maximum change value of the change values is smaller than a second set value. The method of claim 7, wherein The maximum gray scale of the frame is 1024, the gray scale range according to the second set value is 200 plasma display device. 9. The method according to any one of claims 6 to 8, The controller rearranges the number of the sustain signals allocated to the mapped plurality of subfields by the gains, and rearranges the subfields to each of the subfields, and the gain is applied to the maximum gray level (g-max) of the image signal. And a ratio (G-max / g-max) of the maximum gray scale weight (G-max) of the allocated frame. 10. The method of claim 9, And the controller increases the number of the image data by multiplying the gain by the image data corresponding to the image signal.

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