JP3458996B2 - Plasma display panel display device and driving method thereof - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display device which performs halftone display by an in-field time division drive display method,
In particular, the present invention relates to a plasma display panel display device for displaying an image on a plasma display panel and a driving method thereof.

[0002]

2. Description of the Related Art A plasma display panel uses an operating state as a binary display of lighting or non-lighting. And
In order to perform multi-gradation display for image display, halftone display is realized by utilizing the visual integration effect of the time division drive display method within the field (16.6 ms). Less than,
As a conventional technique, a three-electrode AC-type plasma display panel display device that performs halftone display by the time-division drive method in the field will be described as an example.

FIG. 12 is a block diagram showing a general AC type plasma display panel display device. Figure 1
In 2, the frame memory 1 is supplied with image signals (R, G, B signals) converted into, for example, 8-bit digital signals. The frame memory 1 is composed of two field memories, and writing and reading are alternately switched for each field. If the signal form of the image signal is three systems of R, G, and B signals separately, three frame memories are required, and the R, G, and B signals are combined to form one system. Frame memory 1
Consists of one.

The memory writing control circuit 2 inputs a writing control signal to the frame memory 1 to control writing of an image signal into the frame memory 1. The memory read control circuit 3 inputs a read control signal to the frame memory 1 to control the reading of the subfield image bit signal from the frame memory 1. The subfield image bit data which is the display data signal read from the frame memory 1 is input to the address electrode drive circuit 5.
The drive pulse generating circuit 4 drives the plasma display panel 11 to drive the address electrodes 8, the X electrodes 9, and the Y electrodes.
Various drive pulses supplied to the electrode 10 are generated. That is,
The drive pulse generation circuit 4 supplies the address electrode drive pulse to the address electrode drive circuit 5, and the X electrode drive circuit 6 receives the X pulse.
The electrode drive pulse is supplied, and the Y electrode drive pulse is supplied to the Y electrode drive circuit 7.

FIG. 13 is a diagram showing an example of drive waveforms for explaining a display operation by the plasma display panel display device shown in FIG. In FIG. 13, A1 to Am
Address electrode 8, X electrode 9, and Y1 to Yn
The drive waveform supplied to the Y electrode 10 is shown. As shown in FIG. 13, one subfield is composed of three types of periods: a reset period, an address period, and a sustain discharge period. The subfield constitutes a part of the field, which will be described in detail later.

First, in the reset period, three-step operations of all-screen batch erase, all-screen batch write, and all-screen batch erase are performed in order. In this way, the reset period is 3
The main reason for being configured by the step operation is to stabilize the display writing discharge in the address period subsequent to the reset period, to suppress the power consumption of the drive driver IC, and to perform the display writing discharge at a high speed with a low address voltage. This is because. Next, in the address period, an operation of sequentially writing the image bit information, which is the display data assigned to each subfield, for each line is performed. The address electrode 8 sequentially outputs image bit information for n rows corresponding to the number of display lines as serial data row by row from Y1 row. At this time, in each of the address electrodes A1 to Am,
The address pulse is selectively applied only to the discharge cells to be displayed.

Further, the Y electrodes 10 correspond to the serial data applied to the address electrodes 8 one by one in order from the electrode Y1 in the Y electrodes 10 toward the electrodes Yn.
A scan pulse having the same phase as the address pulse and a voltage of 0 V is applied. As a result, the image bit information is written only when the address pulse is applied to the address electrode 8 and the scan pulse is applied to the Y electrode 10.

During the sustain discharge period, sustain pulses for sustaining the discharge are alternately applied to the Y electrode 10 and the X electrode 9. At this time, although the address electrode 8 is fixed at 0V, it is re-discharged (sustain discharge) only by the wall charge and the sustain pulse remaining in the discharge cell in which the image bit information is written in the address period. Therefore, in the sustain discharge period, the discharge continues only in the discharge cells in which the image bit information is written in the address period, the number of times the sustain pulse is applied. As described above, the AC type plasma display panel 11 has a memory function by allowing wall charges to remain in the cells themselves.

FIG. 14 is a diagram showing an example of the operation in the case of performing halftone display by subfield division by the driving method shown in FIG. The vertical axes Y1 to Yn in FIG. 14 represent display lines, and the horizontal axis represents the time axis. Figure 1
In No. 4, in order to obtain 256 gradations (8 bits), one field (16.6 ms) is divided into eight subfields (SF1 to SF8) having different luminance relative ratios, and the LSB (maximum) of the image bit information is divided. The sub-fields are arranged in order from the lower bit) to the MSB (most significant bit). In this way, one field is divided into M subfields, and a visual integration effect by weighting bits based on image bit information is used to generate 2 M gray scales in the plasma display panel 11. Image representation.

As described above, each subfield is composed of the reset period, the address period, and the sustain discharge period. The length of the sustain discharge period differs for each subfield because the number of sustain pulses (sustain pulses) corresponding to the weighting of bits is applied. The number of sustain pulses actually applied is 1, 2,
4, ..., 128, and the pulse number N times (N is a positive integer) is further applied in order to obtain the emission brightness.

[0011]

As described above, according to the driving method of the plasma display panel display device, one field is divided into a plurality of sub-fields having different luminance relative ratios to express the halftone display of the image signal. ing. Under the current driving conditions, gradation expression by an 8-bit digital signal required for image expression must spend most of one field as shown in FIG. This driving method can express an image without any significant problem in the case of a still image, but when displaying a moving image that moves within one field and has a fast movement, before the display of the image of 8 subfields is completed. , The image to be displayed moves from its original location. Therefore, it looks like a bit dropped image,
Due to the difference in the number of sustain discharges for each subfield, a pseudo contour appears or looks like a flicker.

This problem also occurs in the case of an entirely dark image, fade-in / fade-out, and scene change, and the display quality is significantly deteriorated.

In order to improve this, as an example, Japanese Unexamined Patent Publication (Kokai) No.
There is a driving method described in Japanese Unexamined Patent Publication No. 127194/1997. This is a method in which an upper subfield having a large number of sustain discharges is divided into a plurality of subfields and dispersed to display images. However, this method works well for a bright image in which the upper bits are always displayed,
In the case of an image that is dark as a whole, the usage rate of the upper subfields decreases, so that the effect as an improvement measure against the false contour and flicker of the moving image cannot be exhibited.

Further, the driving method of the plasma display panel display device described above has a problem that the reactive power that does not directly contribute to the discharge consumed in the entire panel is large. This reactive power remarkably occurs particularly when there is an entirely dark image or a partially bright image.

The above-mentioned problems are not limited to the display device of the above-mentioned system, and a plasma display panel in which one field is divided into a plurality of subfields having different luminance relative ratios to express halftone display of image signals. Except for display devices, they are the same in all cases. Further, the above problem is not limited to the plasma display panel display device, but is a common problem in a display device that realizes halftone display by utilizing the visual integration effect of the time division drive display method in the field.

The present invention has been made in view of the above problems, and can reduce false contours and flicker of a moving image, and even in the case of an overall dark image, fade-in / fade-out, and scene change. A plasma display panel display device and a plasma display panel display device capable of reducing false contours and flicker, maintaining good display quality, and efficiently reducing reactive power that does not directly contribute to discharge consumed in a drive circuit unit. An object is to provide a driving method.

[0017]

In order to solve the above-mentioned problems of the prior art, the present invention is as follows: (1) One field is divided into a plurality of sub-fields to perform halftone display of an image signal, Plasma for driving the sub-fields so that the sub-fields are composed of at least an address period and a sustain discharge period, and the sustain discharges are weighted for each of the sub-fields by the number of times necessary for halftone display of the image signal in the sustain discharge period. In a display panel display device, an image area highest gradation detection circuit for detecting the highest gradation for each field of the image signal,
As a result of the detection by the image area maximum gradation detection circuit, for a field in which the maximum gradation does not reach the maximum value corresponding to the digital conversion bit number of the image signal, all the halftones in the field are displayed. At this time, depending on the difference in luminance between the maximum value and the highest gradation, the sub-field of the next lower bit is subordinated until the number of sustain discharges of the sub-field assigned to display the most significant bit of the image signal becomes 0. In order not to reduce the number of sustain discharges in the field, the intra-field sustain discharge frequency control circuit for controlling the sustain discharge frequency to be preferentially reduced from the subfield assigned to the display of the most significant bit of the image signal, or the maximum in accordance with the intensity difference between the value and the highest gray level, maintaining weighted number of sustain discharges in the sub-field is in the order of larger subfields Controls to reduce electrostatic number, and, if the weighting of the number of sustain discharges is present the same subfield, the weighting of the number of sustain discharges is within the same subfield, the display of the most upper bit of the image signal (2) A plasma display panel display device, comprising: an intra-field sustain discharge frequency control circuit for controlling the number of sustain discharges in a subfield assigned to a plurality of fields. Divided into subfields for halftone display of the image signal, the subfield is composed of at least an address period and a sustain discharge period, and the number of times required for halftone display of the image signal in the sustain discharge period. A plasma display panel driven so as to perform sustain discharge by weighting each subfield. A method of driving a display device, 1 of the image signal
When detecting the highest gradation for each field and performing all halftone display in the field for which the highest gradation does not reach the maximum value corresponding to the digital conversion bit number of the image signal , The maximum value and the highest gray level so as not to decrease the number of sustain discharges of the subfield of the next lower bit until the number of sustain discharges of the subfield assigned to display the most significant bit of the image signal becomes 0. In accordance with the brightness difference between the above-mentioned image signal and the subfield assigned to display the most significant bit, the number of sustain discharges is reduced, or the brightness difference between the maximum value and the highest gradation is set. in response, the control to decrease the number of sustain discharges in the order of the weighting Gayori large subfield number of sustain discharges in sub-fields, and the number of sustain discharges When subfields having the same weighting exist, control is performed to reduce the number of sustaining discharges of the subfield assigned to display of the most significant bit of the image signal among the subfields having the same weighting of the number of sustain discharges. A method for driving a plasma display panel display device is provided.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION A plasma display panel display device and a driving method thereof according to the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a block diagram showing an embodiment of a plasma display panel display device of the present invention, and FIGS. 2 to 5 are views for explaining a first embodiment of a driving method of the plasma display panel display device of the present invention. 6 and 7 are views for explaining the second embodiment of the driving method of the plasma display panel display device of the present invention, and FIGS. 8 to 10 are the third embodiments of the driving method of the plasma display panel display device of the present invention. FIG. 11 is a diagram for explaining a fourth embodiment of the driving method of the plasma display panel display device of the present invention. In FIG. 1, the same parts as those in FIG. 12 are designated by the same reference numerals.

First, the structure and operation of the plasma display panel display device of the present invention will be described. The driving waveform of the plasma display panel display device of the present invention is similar to that of FIG.

In FIG. 1, an image signal (R, G, B signal) converted into, for example, an 8-bit digital signal is input to the frame memory 1 and also to the image region highest gradation detection circuit 12. It The frame memory 1 is composed of two field memories, and writing and reading are alternately switched for each field. If the signal form of the image signal is three systems of R, G, and B signals separately, three frame memories are required.
When the G and B signals are combined into one system,
The frame memory 1 is composed of one.

The memory writing control circuit 2 inputs a writing control signal to the frame memory 1 to control writing of an image signal into the frame memory 1. The memory read control circuit 3 inputs a read control signal to the frame memory 1 and controls reading of subfield image bit data from the frame memory 1.

The image area maximum gradation detection circuit 12 detects the maximum gradation in all effective image areas displayed on the plasma display panel 11 for each digital field of the inputted digital image signal and is detected. The highest gradation level is input to the in-field sustain discharge frequency control circuit 13. When the signal form of the image signal is three systems of R, G, and B signals separately, the highest gradation is detected from the digital image signals of all three systems.

In-field sustain discharge frequency control circuit 13
Is the maximum value in the image area highest gradation detection circuit 12 where the highest gradation in the image area corresponds to the digital conversion bit number of the input image signal (in FIG. 1, since the input signal is 8 bits, the maximum value is 255). In this case, as in the conventional case, as shown in FIG. 14, a control signal for weighting the number of sustain pulses for each subfield is supplied to the data conversion circuit 14.

However, when the highest gradation in the image area does not reach the maximum value corresponding to the digital conversion bit number of the input image signal, the luminance difference obtained by subtracting the highest gradation in the image area from the maximum value 255 is obtained. Accordingly, when displaying all the halftones in the image area, the control signal for changing the number of sustain discharges is preferentially driven from the subfield assigned to the display of the most significant bit of the image signal. It is supplied to the pulse generation circuit 4 and the data conversion circuit 14.

The drive pulse generating circuit 4 is provided with the address electrodes 8 to drive the plasma display panel 11.
Various drive pulses supplied to the X electrode 9 and the Y electrode 10 are generated. That is, the drive pulse generation circuit 4 supplies the address electrode drive circuit 5 with the address electrode drive pulse, the X electrode drive circuit 6 with the X electrode drive pulse, and the Y electrode drive circuit 7 with the Y electrode drive pulse. . When the highest gradation in the image area does not reach the maximum value corresponding to the digital conversion bit number of the input image signal, the drive pulse generation circuit 4 should reduce the number of sustain discharges according to the input control signal. , X electrode drive circuit 6 and Y electrode drive circuit 7 are controlled. This will be described later in detail.

In this way, when the highest gradation in the image area does not reach the maximum value corresponding to the digital conversion bit number of the input image signal, the plasma display panel 11
Since the number of sustain discharges in the
It is possible to efficiently reduce the reactive power that does not directly contribute to the discharge consumed by the electrode drive circuit 6 and the Y electrode drive circuit 7).

Further, the data conversion circuit 14 reduces the number of sustain discharges of the sub-field image bit data read from the frame memory 1 based on the control signal input from the in-field sustain discharge count control circuit 13. Convert data accordingly. The image bit data converted by the data conversion circuit 14 will be referred to as display subfield data. The data conversion circuit 14 supplies to the address electrode drive circuit 5 display subfield data which is a display data signal when displaying on the plasma display panel 11.

More specifically, the data conversion circuit 14 is
The generation pattern of the display subfield data to be input to the address electrode drive circuit 5 is converted in response to the decrease in the number of sustain discharges. Further, as will be described later in detail, it is possible to diversify the generation pattern of the display subfield data in response to the decrease in the number of sustain discharges, and thus the plurality of generation patterns are appropriately switched and output. To do.

Next, the first embodiment of the method of driving the plasma display panel display device of the present invention, and the details of the control of the drive pulse generation circuit 4 and the data conversion circuit 14 by the in-field sustain discharge frequency control circuit 13 will be described. The example to the fourth embodiment will be described in order. In the first to fourth embodiments of the driving method of the plasma display panel display device of the present invention described below, the case where the input image signal is 5 bits and 32 gradations will be described for simplification of description. . Therefore, the same applies when the input image signal has 8 bits and 256 gradations.

<First Embodiment> In FIG. 2, the input image signal is 5
An example of the relationship between the highest gradation (hereinafter, peak value) and the number of sustain discharges in the case of 32 gradations in bits is shown. The in-field sustain discharge frequency control circuit 13 in FIG. 1 sets the sustain discharge frequency as shown in FIG. 2A or 2B according to the peak value detected by the image area highest gradation detection circuit 12. The drive pulse generation circuit 4 is controlled so that

In this example, 32 gradations are divided into 5 subfields (SF1 to SF5). The numbers below the subfields SF1 to SF5 represent the original number of sustain discharges in each subfield. Further, the numbers shown in the respective sections indicate the number of sustain discharges in each subfield in which the number of sustain discharges is reduced at each peak value in the image area. As described with reference to FIG. 14, the number of sustain discharges (the number of pulses) that is N times the number of sustain discharges shown in FIG. 2 is actually applied. Therefore, the numbers shown in FIG. 2 actually represent the sustain discharge frequency ratio, but for simplification,
It will be described as the number of sustain discharges.

In the first mode shown in FIG. 2A, the peak value of the image area is not reached to the maximum value (31 in this case) corresponding to the digital conversion bit number of the input image signal for the field. The sub-field assigned to display the most significant bit of the image signal (in this case, SF
5) shows the number of sustain discharges in each subfield for each peak value when the number of sustain discharges is changed to be reduced from 5).

That is, if the peak value is 31, the number of sustain discharges in each subfield is not changed. For example, if the peak value is 30, 1 is subtracted from the subfield SF5 assigned to display the most significant bit by 1 obtained by subtracting 30 from the maximum value, 31. Therefore, each subfield from SF1 to SF5 is maintained. The number of discharges is 1, 2, 4,
8 and 15. Similarly, if the peak value is 29, 2 is subtracted from subfield SF5, and the number of sustain discharges in each subfield from SF1 to SF5 is 1, 2, 4,
8 and 14.

Then, when the number of sustain discharges in the subfield SF5 to be preferentially reduced becomes 0 like the peak value 15, the number of sustain discharges in the next priority subfield SF4 is similarly reduced. Thus, the first
In the mode, when the number of sustain discharges is decreased from the subfield SF5 assigned to display of the most significant bit to the subfield SF1 assigned to display of the least significant bit, the number of sustain discharges in the subfield is reduced. When it becomes 0, the number of sustain discharges is sequentially changed so as to decrease the number of sustain discharges of the subfield of the next lower bit.

In the second mode shown in FIG. 2B, like the first mode, the number of sustain discharges is reduced in priority from the subfield SF5. However, as in the case where the peak value is 20, the subfield SF5 is reduced. When the number of sustain discharges in SF5 becomes smaller than the number of sustain discharges in subfield SF4, at peak value 19, the number of sustain discharges in subfield SF4 is reduced so that the number of sustain discharges in subfields SF4 and SF5 becomes equal. Furthermore, when the number of sustain discharges in the subfield SF3 becomes smaller than the number of sustain discharges in the subfields SF4 and SF5, as in the peak value 10, at the peak value 9, the subfields SF3 to SF5 are reached.
So that the number of sustain discharges of
The number of sustain discharges of 3 is reduced.

As described above, in the second mode, when the number of sustain discharges becomes 0 as in the first mode, the number of sustain discharges of the subfields of the next lower bit is not decreased sequentially, but the most significant bit of the most significant bit. When decreasing the number of sustain discharges from the subfield SF5 assigned to display toward the subfield SF1 assigned to display of the least significant bit, the number of sustain discharges in that subfield and the subfield of the next lower bit When the number of sustain discharges in the subfield becomes smaller than the number of sustain discharges in the subfield of the next lower bit, the subfields in which the number of sustain discharges is decreased are sequentially performed in the next lower order. The number of sustain discharges is changed so as to move to the bit subfield.

In this way, the subfield SF3
The number of sustain discharges of SF5 is almost equal in many peak values. Note that the number of sustain discharges in subfield SF5 is 0 when the peak value is 4 or less.

In the first embodiment, as in the first and second modes shown in FIGS. 2A and 2B, the field in which the highest gradation does not reach the maximum value corresponding to the number of bits of the input image signal. In contrast, when displaying all halftones in the image area, priority is given to the subfield assigned to the display of the most significant bit by the amount corresponding to the luminance obtained by subtracting the highest gradation from the maximum value. Reduce the number of sustain discharges. Therefore,
The smaller the peak value of the image area, the smaller the number of sustain discharges in the subfield where the number of sustain discharges is weighted. Therefore, according to the peak value of the image area, it does not directly contribute to the discharge consumed in the drive circuit unit. Reactive power can be greatly reduced.

Further, the relationship between the gradation and the generation pattern of the display subfield data will be described with reference to FIG. In FIG. 3, (a) shows the generation pattern of the display sub-field data in each gradation when the peak value in the image area matches the maximum value 31 of the input image signal, and (b) shows the image. The generation pattern of the display sub-field data in each gradation when the peak value in the area is 29 is shown. In addition, in FIG.
Indicates that there is display subfield data, and blank indicates that there is no display subfield data.

When the peak value in the entire image area shown in FIG. 3A is 31, it is exactly the same as the conventional one, and the generation pattern of the display subfield data from the gradation 31 to the gradation 0 is shown in the figure. It seems that. In this case, if the image near the gradation 16 occupies a large area, pseudo contour color noise and luminance noise such as contour lines are likely to occur especially in moving images.
This is because the generation pattern of the display sub-field data in the gradation 16 has no display sub-field data in the sub-fields SF1 to SF4 as shown in FIG. 3A, and is biased only to the uppermost sub-field SF5. This is because it ends up.

Therefore, when the line of sight follows the motion of the moving image, the line of sight moves to a different place in the field before the image is completed, and the above noise is recognized. In this phenomenon, interference of noise tends to be particularly conspicuous in an image near the gradation in which the subfield (SF5 in this case) having the maximum weighting of the number of sustain discharges is independently selected.

When the peak value in the entire image area shown in FIG. 3 (b) is 29, as described above, the most significant bit is displayed by the two gradations obtained by subtracting the peak value 29 from the maximum value 31. The number of sustain discharges of the subfield SF5 assigned to is reduced and displayed. Therefore, the number of sustain discharges in the subfield SF5 is 14. When the number of sustain discharges in the subfield SF5 is changed in this manner, as shown in FIG.
3A and 3B when the peak value is 31 shown in FIG.
As can be seen by comparing with the gradation 29 at the peak value 29 shown in (b), the generation pattern of the display subfield data is different. In this way, the data conversion circuit 14
The generation pattern of the display subfield data is converted according to the change (decrease) in the number of sustain discharges.

Moreover, there are two generation patterns of the display sub-field data of gradation 14 to gradation 16 of the first pattern and the second pattern. For example,
At gradation 14, it is possible to select a first pattern for generating display subfield data only in subfield SF5 and a second pattern for generating display subfield data in all of subfields SF2 to SF4.

Therefore, the data conversion circuit 14 converts the sub-field image bit data to be input to the address drive circuit 5, and further, in each gradation, the pseudo contour noise among these plural generation patterns. It is possible to select a generation pattern in which is less likely to occur. In addition, the generation pattern of the display subfield data is changed, for example, for each even-numbered column and odd-numbered column in the plasma display panel 11, or for each line,
Alternatively, if it is changed at random, it is possible to greatly reduce the pseudo contour noise in the moving image described above.

As described above, according to the present invention, even when the image near the gradation 16 occupies a wide area, if the above-mentioned control is performed when the peak value in the entire image area is less than 31, the number of sustain discharges can be reduced. The probability that the subfield with the maximum weighting is selected alone is drastically reduced, and image interference such as false contour and flicker in a moving image can be significantly reduced.

Image interference such as false contours and flicker in moving images as described above is caused not only in the vicinity of the gradation where the upper subfield is independently selected, but also in dark images, fade-in / fade-out and scene changes. In some cases, it tends to stand out. Therefore, the present invention can significantly reduce the moving image disturbance even in such a case.

Here, the peak value in the entire image area is 29.
However, the peak value in the entire image area is 3
Even in other cases where the number is less than 1, the effect of reducing the pseudo contour noise at the time of moving image can be similarly exhibited. 4 is shown in FIG.
2 shows the generation pattern of the display subfield data when the peak value is 19 in the first mode, and FIG. 5 shows the generation pattern of the display subfield data when the peak value is 19 in the second mode of FIG.

In the first mode shown in FIG. 4, gradation 4
There are two generation patterns of the display sub-field data in the area from 1 to 15. Further, in the second mode shown in FIG. 5, there are two or three generation patterns of the display subfield data in the regions from the gradation 6 to the gradation 13.

In this way, in the gradation of the region where a plurality of generation patterns exist, the selection probabilities of the subfields are controlled so as to be displayed so as to be dispersed so as to be almost equal so as not to concentrate. Further, as described above, by combining the selection patterns for each column or each line, it is possible to drastically reduce the generation of pseudo contour noise during moving images. Furthermore, during fade-in / fade-out and scene changes, the peak value in the entire image area changes gradually, so if you repeat the above control, the subfield selection probability will be dispersed in the time domain as well. Interference can be effectively reduced.

As described above, in the first embodiment of the present invention,
For the field where the peak value of the input image signal in the image area (1 field) does not reach the maximum value corresponding to the digital conversion bit number of the input image signal, the peak value from the maximum digital conversion bit number of the input image signal The sub-field assigned to display the most significant bit of the image signal is controlled so that the number of sustain discharges is reduced in accordance with the brightness obtained by subtracting, so that the reactive power that does not directly contribute to the discharge consumed by the drive circuit unit Can be significantly reduced.

Moreover, since the generation pattern of the display subfield data can be changed or increased according to the decrease in the number of sustain discharges, the subfield having the maximum weight of the number of sustain discharges is independent. The probability of selection is drastically reduced, and image interference such as false contours and flicker in moving images can be significantly reduced. Further, even when the image is dark as a whole, or when the fade-in / fade-out and the scene change are performed, it is possible to reduce the moving image interference, and it is possible to display a high-quality image.

<Second Embodiment> The second embodiment has the same basic concept as that of the first embodiment, but the subfield assigned to display the most significant bit of the image signal is another image bit. Shows the case of straddling the subfields assigned to the display of.

Specifically, in FIG. 6 which is the second embodiment, when the input image signal is 5 bits and 32 gradations, the subfields assigned to display the most significant bit and the second most significant bit are maintained. The figure shows the case where the number of discharges is added and the number of discharges is evenly divided and divided into four. In this example, 32 gradations are divided into 7 subfields (SF1 to SF7) for conversion. The numbers below the subfields SF1 to SF7 represent the original number of sustain discharges in each subfield. Further, the numbers shown in the respective sections indicate the number of sustain discharges in each subfield in which the number of sustain discharges is reduced at each peak value in the image area. In this case as well, the number actually represents the sustain discharge frequency ratio, but for simplicity, it will be described as the sustain discharge frequency.

In the first mode shown in FIG. 6A, the peak value in the image area is set to the field which is found not to reach the maximum value (31 in this case) corresponding to the digital conversion bit number of the input image signal. On the other hand, sustain discharge of each subfield for each peak value when the number of sustain discharges is changed to be preferentially decreased from SF7 of subfields SF4 to SF7 assigned to display the most significant bit of the image signal. Shows the number of times. In the first mode, from the subfield SF7 toward the subfield SF1, when the number of sustain discharges in the subfield becomes 0, the number of sustain discharges is sequentially decreased so as to decrease the number of sustain discharges in the subfield of the next lower bit. change.

In the second mode shown in FIG. 6 (b), when the number of sustain discharges becomes 0 as in the first mode, the number of sustain discharges in the next lower subfield is not decreased but is set to the highest level. When reducing the number of sustain discharges from SF7 of the subfields SF4 to SF7 assigned to display bits to the subfield SF1 assigned to display of the least significant bit, the number of sustain discharges in the subfields is reduced. Is smaller than the number of sustain discharges in the next lower subfield, the number of sustain discharges is changed so that the subfields for decreasing the number of sustain discharges are sequentially moved to the next lower subfield.

In this case, the number of sustain discharges in the subfield SF7 becomes 0 when the peak value is 6 or less.

Also in the second embodiment, as in the first and second modes shown in FIGS. 6A and 6B, the maximum gradation does not reach the maximum value corresponding to the bit number of the input image signal. In contrast, when performing halftone display in the image area, the sustain discharge is given priority over the subfield assigned to the display of the most significant bit according to the brightness obtained by subtracting the highest gradation from the maximum value. Reduce the number of times. Therefore, the smaller the peak value of the image area, the smaller the number of sustain discharges in the subfield where the number of sustain discharges is heavily weighted. Reactive power that does not contribute can be greatly reduced.

Further, the relationship between the gradation and the generation pattern of the display subfield data will be described with reference to FIG. In FIG. 7, the first mode shown in (a) and (b)
In the second mode shown in FIG. 6, the peak value of the image area in the first mode and the second mode shown in FIGS.
In this case, a representative example of the display subfield data generation pattern is shown. The numbers below the subfields SF1 to SF7 indicate the number of sustain discharges in each subfield when the peak value of the image area is 19, and the circles in the section indicate that there is display subfield data. There is. The number shown as the selected number indicates the total number (selectable number) of combinations of the generated patterns in each gradation.

Also in the second embodiment, as shown in FIGS. 7 (a) and 7 (b), in the gradation having a plurality of occurrence patterns, the selection patterns such as columns and lines are dispersed with almost the same probability. By combining them, it is possible to drastically reduce the generation of pseudo contour noise during moving images. Furthermore, during fade-in / fade-out and scene changes, the peak value in the entire image area changes gradually, so if you repeat the above control, the subfield selection probability will be dispersed in the time domain as well. Interference can be effectively reduced.

Particularly, in the case of the second mode shown in FIG. 7 (b), the utilization efficiency of each subfield is high even in the low gradation, and since there are many occurrence patterns, they can be widely dispersed. The effect is greater than in the first mode. When there are a large number of generation patterns of display subfield data, it is needless to say that all of them may not be used and a preferable part of them may be used.

As described above, in the second embodiment, the subfield assigned to the display of the most significant bit of the image signal extends over the subfield assigned to the display of another image bit, and the In the field where the peak value of the input image signal does not reach the maximum value corresponding to the digital conversion bit number of the input image signal, according to the brightness obtained by subtracting the peak value from the maximum value of the digital conversion bit number of the input image signal. Since the sub-field assigned to display the most significant bit of the image signal is controlled so as to reduce the number of sustain discharges with priority, the reactive power that does not directly contribute to the discharge consumed in the drive circuit unit can be significantly reduced. it can.

Moreover, since the generation pattern of the display subfield data is further increased as compared with the first embodiment, the probability that the subfield having the maximum weight of the number of sustain discharges is independently selected is drastically reduced, and the pseudo contour in the moving image is reduced. Image interference such as flicker and flicker can be significantly reduced. Also, if the image is dark overall, fade-in /
Even at the time of fade-out and scene change, it is possible to reduce the disturbance of the moving image and display a high quality image.

<Third Embodiment> The third embodiment has the same basic concept as that of the first embodiment, but the subfield assigned to display the most significant bit of the image signal is further divided into a plurality of subfields. It shows the case of being divided into fields.

Specifically, FIGS. 8 and 9 showing the third embodiment.
When the input image signal is 5 bits and 32 gradations, the subfield SF5 assigned to display the most significant bit in FIG. 2 is further divided into 3 or 2 subfields, and the subfields SF5 to SF7 are Alternatively, the case is shown where the subfields are SF5 and SF6. Note that FIG. 8 shows each of the subfields SF5 to SF.
7, the number of sustain discharges is weighted, and the number of sustain discharges 3,
This is an example of the case where the sub-fields SF5 and SF8 are not equal, and FIG. 9 is an example where the number of sustain discharges in the sub-field SF5 in FIG.

In these examples, 32 gradations are divided and converted into 7 subfields (SF1 to SF7) or 6 subfields (SF1 to SF6). The numbers shown under the subfields SF1 to SF7 and SF1 to SF6 represent the original number of sustain discharges in each subfield. Further, the numbers shown in the respective sections indicate the number of sustain discharges in each subfield in which the number of sustain discharges is reduced at each peak value in the image area. In this case as well, the number actually represents the sustain discharge frequency ratio, but for simplicity, it will be described as the sustain discharge frequency.

In the first mode shown in FIG. 8A, the peak value of the image area is not reached to the maximum value (31 in this case) corresponding to the digital conversion bit number of the input image signal for the field. Then, the sustain discharge of each subfield for each peak value in the case where the subfield SF7 assigned to the most significant bit of the image signal and having a large number of weights of the sustain discharge is changed so that the number of sustain discharge is reduced first. Shows the number of times. In the first mode, when the number of sustain discharges is decreased from the subfield SF7 toward the subfield SF1, when the number of sustain discharges in the subfield becomes 0, the number of sustain discharges of the next lower subfield is sequentially performed. The number of sustain discharges is changed so that

In the second mode shown in FIG. 8B, unlike the first mode, the subfields SF5 to SF7 assigned to display the most significant bit of the image signal are not simply prioritized, but the subfields are not prioritized. In SF1 to SF7, the number of sustain discharges is reduced in descending order of weighting of the number of sustain discharges. In the examples up to now, the subfield assigned to display the most significant bit of the image signal is the subfield having the highest weighting of the number of sustain discharges. However, as shown in FIG. Is larger than the number of sustain discharges of the subfield 5, the subfield having the larger weight of the number of sustain discharges may be prioritized.

For example, if the peak value is 30, 1 is subtracted from the subfield SF7 assigned to the display of the most significant bit by 1 obtained by subtracting 30 from the maximum value 31. Therefore, each subfield of SF1 to SF7 is subtracted. The number of sustain discharges in the field is 1, 2, 4, 8, 3, 5, 7. If the peak value is 29, the subfield SF4
By subtracting 1, the number of sustain discharges in each subfield from SF1 to SF7 is set to 1, 2, 4, 7, 3, 5, 5.

In this example, when the number of sustain discharges in each subfield is the same at each peak value, the number of sustain discharges is made smaller than that in the subfield assigned to the display of higher bits. That is, the subfields SF4, SF6, S at the peak value 25
Since the number of sustain discharges in F7 is 5, the peak value 24 is 1 from the highest subfield SF7.
Is being reduced.

As described above, in the second mode, the sustain discharge frequency is reduced in descending order of the weight of the sustain discharge frequency in consideration of the weighting of the sustain discharge frequency at each peak value. In this case, subfield SF7
The number of sustain discharges of 0 is 0 when the peak value is 6 or less.

Further, also in FIG. 9, the first mode shown in (a) is assigned to the display of the most significant bit, and the number of sustain discharges is preferentially reduced from the subfield SF6 in which the number of sustain discharges is weighted. In the second mode shown in (b), the number of sustain discharges decreases from subfield SF6 assigned to display of the most significant bit to subfield SF1 assigned to display of the least significant bit. When the number of sustain discharges in the subfield becomes smaller than the number of sustain discharges in the next lower subfield, the subfields for decreasing the number of sustain discharges are sequentially moved to the next lower subfield. Change the number of sustain discharges.

Also in the third embodiment, (a) of FIG. 8 and FIG.
As in the first and second modes shown in (b), for a field in which the highest gradation does not reach the maximum value corresponding to the number of bits of the input image signal, all halftone display in the image area is performed. When performing, the number of sustain discharges is preferentially reduced over the subfield assigned to the display of the most significant bit according to the luminance obtained by subtracting the highest gradation from the maximum value. Therefore,
The smaller the peak value of the image area, the smaller the number of sustain discharges in the subfield where the number of sustain discharges is weighted. Therefore, according to the peak value of the image area, it does not directly contribute to the discharge consumed in the drive circuit unit. Reactive power can be greatly reduced.

Further, the relationship between the gradation and the generation pattern of the display subfield data will be described with reference to FIG. FIG. 10 shows the total number of combinations of the generated patterns in each gradation (the number of selected patterns) when the peak value of the image region in the first mode and the second mode of FIGS. 8 and 9 is 19.
Is represented. In each mode, the most preferable generation pattern is selected in the gradation in which a plurality of selection patterns exist, and further, each generation pattern such as each column or each line is dispersed with almost the same probability, so that Pseudo contour noise can be significantly reduced.

Particularly, in the case of the second mode shown in FIG. 8B, the utilization efficiency of each subfield is high even in the low gradation, and since each generation pattern is large, they can be widely dispersed. Its effect is greater than other modes.

<Fourth Embodiment> The fourth embodiment shown in FIG. 11 has the same basic concept as that of FIG. 9 in the third embodiment, but the number of sustain discharges is lower for the lower three subfields SF1 to SF3. Shows an example in which no change is made. In FIG. 11, (a) and (b) show the same first and second modes as described above, respectively. As described above, even if the number of sustain discharges is not changed for the lower subfields that originally have a small number of sustain discharges and the number of sustain discharges is changed only for the upper subfields, the same as in the first to third embodiments. The effect of can be produced.

As described above, according to the plasma display panel display device and the driving method thereof of the present invention, an image is generated in a field in which the maximum gradation does not reach the maximum value corresponding to the digital conversion bit number of the image signal. When displaying all the halftones in the area, the number of sustain discharges is reduced in priority to the subfield assigned to display the most significant bit of the image signal according to the brightness difference between the maximum value and the highest gradation. Alternatively, by controlling the number of sustain discharges to be reduced in descending order of the weight of the number of sustain discharges, the reactive power that does not directly contribute to the discharge consumed in the drive circuit unit can be efficiently reduced.

Further, by converting the generation pattern of the image bit data to be supplied to the plasma display panel 11 in accordance with the decrease in the number of sustain discharges, it is possible to reduce the pseudo contours and flicker of the moving image, and overall. Even in the case of a dark image, fade-in / fade-out, and scene change, pseudo contours and flicker can be reduced, and good display quality can be maintained.

By the way, the plasma display panel display device of the present invention is not limited to the embodiment shown in FIG. For example, the control signal output from the intra-field sustain discharge frequency control circuit 13 is input to the data conversion circuit 14, but the output of the image area highest gradation detection circuit 12 is input to the data conversion circuit 14 in the same manner. It is also possible to change the generation pattern of field data. Various changes can be made to the circuit configuration.

Further, in the present embodiment, the generation pattern of the display subfield data is selected such that the number of sustain discharges is completely the same. However, particularly in the subfield assigned to the display of the upper bit, Since the number of sustain discharges is extremely large, no visual problem occurs even if the number of sustain discharges is not the original number. Therefore, when selecting a plurality of generation patterns of the display sub-field data, it is possible to include those having substantially the same number of sustain discharges.

[0080]

As described above in detail, the plasma display panel display device and the driving method thereof according to the present invention can be applied to a field in which the highest gradation does not reach the maximum value corresponding to the digital conversion bit number of the image signal. , When displaying all halftones in the image area, the number of sustain discharges is given priority from the subfield assigned to display the most significant bit of the image signal according to the brightness difference between the maximum value and the highest gradation. Or the number of sustain discharges is reduced in descending order of weighting of the number of sustain discharges, it is possible to efficiently reduce the reactive power that does not directly contribute to the discharge consumed in the drive circuit unit. Furthermore, by converting the generation pattern of the image bit data to be supplied to the plasma display panel according to the decrease in the number of sustain discharges, it is possible to reduce the false contours and flicker of the moving image, resulting in an overall dark image or fading. Even in the case of in / fade out and scene change, pseudo contours and flicker can be reduced, and good display quality can be maintained.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a plasma display panel display device of the present invention.

FIG. 2 is a diagram for explaining the first embodiment of the driving method of the plasma display panel display device of the present invention.

FIG. 3 is a diagram for explaining the first embodiment of the driving method of the plasma display panel display device of the present invention.

FIG. 4 is a diagram for explaining the first embodiment of the driving method of the plasma display panel display device of the present invention.

FIG. 5 is a diagram for explaining the first embodiment of the driving method of the plasma display panel display device of the present invention.

FIG. 6 is a diagram for explaining a second embodiment of the driving method of the plasma display panel display device of the present invention.

FIG. 7 is a diagram for explaining a second embodiment of the driving method of the plasma display panel display device of the present invention.

FIG. 8 is a diagram for explaining a third embodiment of the driving method of the plasma display panel display device of the present invention.

FIG. 9 is a diagram for explaining a third embodiment of the driving method of the plasma display panel display device of the present invention.

FIG. 10 is a diagram for explaining a third embodiment of the driving method of the plasma display panel display device of the present invention.

FIG. 11 is a diagram for explaining a fourth embodiment of the driving method of the plasma display panel display device of the present invention.

FIG. 12 is a block diagram showing an example of a conventional plasma display panel display device.

FIG. 13 is a diagram showing an example of drive waveforms for explaining a display operation by the plasma display panel display device.

FIG. 14 is a diagram showing an example of an operation when displaying a halftone by subfield division.

[Explanation of symbols]

1 frame memory 2 Memory write control circuit 3 Memory read control circuit 4 Drive pulse generation circuit 5 Address electrode drive circuit 6 X electrode drive circuit 7 Y electrode drive circuit 8 address electrodes 9 X electrodes 10 Y electrodes 11 Plasma display panel 12 Image area highest gradation detection circuit 13 Field sustaining frequency control circuit 14 Data conversion circuit

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI G09G 3/20 G09G 3/20 641R 3/28 K (56) Reference JP-A-11-65521 (JP, A) JP-A 10-333639 (JP, A) JP 10-319894 (JP, A) JP 10-282929 (JP, A) JP 3-238497 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G09G 3/28 G09G 3/20 611 G09G 3/20 641

Claims (8)

(57) [Claims] 1. One field is divided into a plurality of sub-fields to perform halftone display of an image signal, the sub-fields are composed of at least an address period and a sustain discharge period, and the image is generated in the sustain discharge period. In a plasma display panel display device that is driven so as to perform sustain discharge by weighting each subfield for the number of times necessary for displaying a halftone of a signal, the maximum image area for detecting the highest gradation for each field of the image signal As a result of detection by the gradation detection circuit and the image area maximum gradation detection circuit, for the field in which the maximum gradation does not reach the maximum value corresponding to the digital conversion bit number of the image signal, all in the field When performing the halftone display of the, the most significant bit of the image signal according to the brightness difference between the maximum value and the highest gradation. The subfield assigned to display the most significant bit of the image signal is prioritized so as not to decrease the number of sustain discharges of the subfield of the next lower bit until the number of sustain discharges of the subfield assigned to And a sustain discharge frequency control circuit for controlling the number of sustain discharges to reduce the number of sustain discharges. 2. One field is divided into a plurality of subfields for halftone display of an image signal, the subfields are composed of at least an address period and a sustain discharge period, and the image is generated in the sustain discharge period. In a plasma display panel display device that is driven so as to perform sustain discharge by weighting each subfield for the number of times necessary for displaying a halftone of a signal, the maximum image area for detecting the highest gradation for each field of the image signal As a result of detection by the gradation detection circuit and the image area maximum gradation detection circuit, for the field in which the maximum gradation does not reach the maximum value corresponding to the digital conversion bit number of the image signal, all in the field When performing halftone display of, the brightness in the subfield is changed according to the brightness difference between the maximum value and the highest gradation. Controlled to weighting discharge frequency decreases the number of sustain discharges in the order of larger subfield, and,
When there are subfields having the same sustain discharge weighting, the number of sustain discharges of the subfields assigned to the display of the most significant bit of the image signal among the subfields having the same sustain discharge weighting is calculated. A display device for a plasma display panel, comprising a control circuit for controlling the number of sustain discharges in a field for controlling so as to decrease. 3. A data conversion circuit for converting an image bit data generation pattern of the image signal according to a decrease in the number of sustain discharges.
Alternatively, the plasma display panel display device according to item 2. 4. The plasma display panel display device according to claim 3, wherein the data conversion circuit has a plurality of generation patterns of image bit data of the image signal and switches the plurality of generation patterns. 5. One field is divided into a plurality of subfields for halftone display of an image signal, the subfields are composed of at least an address period and a sustain discharge period, and the image is generated in the sustain discharge period. In a driving method of a plasma display panel display device, which is driven so as to carry out sustain discharge by weighting each subfield as many times as necessary for halftone display of a signal, the highest gradation is detected for each field of the image signal. Together with the field where the highest gradation does not reach the maximum value corresponding to the digital conversion bit number of the image signal,
When performing all halftone display in the field, the number of sustain discharges of the subfields assigned to display the most significant bit of the image signal is determined according to the brightness difference between the maximum value and the highest gradation. In order not to reduce the number of sustain discharges in the subfield of the next lower bit until 0, control is performed to reduce the number of sustain discharges preferentially from the subfield assigned to display the most significant bit of the image signal. And a method for driving a plasma display panel display device. 6. One field is divided into a plurality of subfields for halftone display of an image signal, and each subfield is composed of at least an address period and a sustain discharge period, and the image is generated in the sustain discharge period. In a driving method of a plasma display panel display device, which is driven so as to carry out sustain discharge by weighting each subfield as many times as necessary for halftone display of a signal, the highest gradation is detected for each field of the image signal. Together with the field where the highest gradation does not reach the maximum value corresponding to the digital conversion bit number of the image signal,
When performing halftone display in all of the fields, the number of sustain discharges is increased in the order of the subfields in which the weighting of the number of sustain discharges in the subfield is larger in accordance with the luminance difference between the maximum value and the highest gradation. Control to reduce
And, if there are subfields having the same weighting of the sustain discharge frequency, among the subfields having the same weighting of the sustain discharge frequency, of the subfields assigned to the display of the most significant bit of the image signal. A method of driving a plasma display panel display device, comprising controlling the number of sustain discharges to be reduced. 7. The driving method of the plasma display panel display device according to claim 5, wherein the generation pattern of the image bit data of the image signal is converted according to the decrease in the number of sustain discharges. 8. A method of driving a plasma display panel display device according to claim 7, wherein a plurality of generation patterns of image bit data of the image signal are provided and the plurality of generation patterns are switched.