JP3471729B2 - Plasma display device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vertical scanning of a video signal.
Display device capable of responding to changes in scanning frequency
About. 2. Description of the Related Art Generally, a plasma display device is
The drive input voltage and the display output show non-linear characteristics. So
Therefore, the brightness corresponding to the input signal depends on the drive input voltage.
It is not possible to display video signals with
No. Therefore, in a plasma display device,
One frame of the screen is divided into multiple sub-frames (hereinafter,
It is called "SF". ) Is divided in time into
The light time is weighted, and the discharge light emission of each SF is turned ON /
OFF control to change the number of discharge light emission of each SF.
Thus, gradation is displayed. [0004] However, the above-mentioned program
As in a plasma display device, the gradation is controlled by SF processing.
When displaying, the vertical frequency of the video signal changes, especially
As the vertical frequency of the image signal increases, the frequency of the write pulse increases.
Number and the frequency of the sustaining pulse also change,
There is a problem of becoming stable. Addressing such issues
Therefore, a program that can respond to changes in the vertical scanning frequency of video signals
Various plasma display devices have been proposed. [0005] This type of plasma display device is
In Japanese Patent Application Laid-Open No. 8-76716, the vertical
Release of each SF to perform gradation display based on the synchronization frequency
Adjusting the number of times of light emission stabilizes the brightness level
The disclosure of the present invention is disclosed. However
Et al. Of the plasma display device according to the above publication.
Display based on the vertical synchronization frequency of the video signal
When adjusting the number of discharge light emission of each SF for performing
Is the number of times the number of discharge light emission of each SF is proportional to a power of 2.
Can not be set in many cases. Therefore, the linearity of gradation
There is a problem of being damaged. In order to address such a problem, the present inventor has
Is the same as the reference vertical sync signal, separate from the input vertical sync signal of the video signal.
Frame memo required to generate the synchronization signal and perform SF processing
Input of the area where the operation of discharge light emission becomes unstable
Display with reference vertical sync signal against vertical sync frequency,
It is not necessary to perform so-called frame rate conversion
I thought about it. Further, the inventor of the present application has found that the operation of discharge light emission is not sufficient.
For the input vertical synchronization frequency in the area where
I thought that it might be changed. However
Therefore, when the number of SFs is changed, a change in gradation occurs, and the number of SFs is reduced.
If it is reduced, the gradation that can be displayed will decrease.
Problem arises. The present invention solves the above problems.
The operation of discharge light emission is unstable
The input vertical sync frequency in the region where
Plasma display device that can display without inviting
The purpose is to provide a device. [0008] In order to achieve the above object,
And a plasma display according to the invention of claim 1.
The device is designed for multiple subfields with different relative luminance ratios.
One field to correspond to multi-gradation video signal
Image with different gradations on a plasma display panel
In this way, the current video and the past video are
And compare the results to see if there is any motion in the video.
Motion detection means for detecting and generating a vertical synchronizing signal for display.
When moving the video, there must be no motion in the motion detection means
Vertical for display to occur, provided that is detected
Vertical sync for display to output with lower frequency of sync signal
When generating the subfield, the signal generating means
Display vertical with lower frequency than display vertical synchronizing signal generator
Should be generated on condition that the direct sync signal is output
Subfield generator that increases the number of subfields
And a step. Embodiments of the present invention will be described below.
This will be described in detail with reference to the drawings. (Embodiment 1) FIG. 1 shows Embodiment 1 of the present invention.
FIG. 2 is a block diagram illustrating a configuration of a plasma display device.
You. With reference to FIG.
The display device has a plurality of displays with different relative ratios of brightness.
1 fee from Bufffield (hereinafter referred to as "SF")
A grayscale image corresponding to the multilevel video signal.
The image is referred to as a plasma display panel (hereinafter, "PDP").
Say. ) 16 is displayed on the screen.
A / D converting the video signal input from the signal input terminal 1
A / D conversion unit 2 is used to generate SF.
Digitized by the A / D converter 2 for each field
Video signal writing operation and digital
The first operation of alternately performing the read operation of the converted video signal
Frame memory 4 and second frame memory 5
And a first frame memory 4 and a second frame memo
A frame memory for performing a write operation from
The write selection switch 3 to be selected and the first frame
Read from the memory 4 and the second frame memory 5
Read selection to select the frame memory to perform
Input from the select switch 6 and the vertical synchronizing signal input terminal 9
Vertical sync signal (hereinafter referred to as “input vertical sync signal”).
No. " ) To display the image on PDP16
Display vertical sync signal to generate display vertical sync signal for
Signal generator 13 and a first signal based on the input vertical synchronization signal.
Frame memory 4 and second frame memory 5
Write operation and turning off write select switch 3
Frame memory write control unit 7 for controlling the switching operation
And the display generated by the display vertical synchronizing signal generator 13.
Frame memory based on a vertical synchronizing signal for
4, the read operation of the second frame memory 5,
In addition, the switching operation of the read selection switch 6 is controlled.
A frame memory read control unit 8 and a first frame
Read from the memory 4 or the second frame memory 5
Subfield generation for generating SF based on data
Unit 14 and the output signal from subfield generation unit 14
Drive control unit 15 that controls the drive of PDP 16 based on the
And As a video signal, for example, an NTSC signal
(Vertical synchronization frequency is 60Hz), PAL / SECAM
(Vertical synchronization frequency is 50Hz) or personal
Video signals with various vertical synchronization frequencies such as computer
No. The display vertical signal generating section 13 is used for displaying
A reference vertical sync signal that generates a reference vertical sync signal
Raw section 10, frequency of input vertical synchronization signal and reference vertical synchronization
The frequency of the reference vertical synchronization signal generated from the signal generator 10
A frequency comparison unit 11 for comparing the number with a display vertical synchronization signal
Input vertical sync signal and reference vertical sync signal
Switch 1 for selecting either one of
2, the frequency of the input vertical synchronizing signal and the reference vertical
The frequency is compared with the frequency of the direct synchronizing signal.
The vertical sync signal frequency is higher than the reference vertical sync signal frequency.
The reference vertical sync signal for display
Output to the frame memory read control unit 8 as a synchronization signal.
It is configured to force. The reference vertical synchronizing signal generator 10 is, for example,
Crystal oscillator and the clock generated by it
It consists of a circling counter. Frequency comparison unit 11
Are, for example, the input vertical sync signal and the reference vertical sync signal.
Are initialized with two signals that count the same clock.
Performances like counters or microcontrollers
It consists of an arithmetic unit. Here, the plasma display device described above
The operation will be described. Video signal input terminal
1 to the A / D converter 2. Then, A /
The D conversion unit 2 performs A / D conversion of the video signal and digitizes the video signal.
The written video signal is supplied to the write selection switch 3. On the other hand, the input vertical synchronizing signal of the video signal is
Frame memory write control from direct synchronization signal input terminal 9
Unit 7 and a display vertical synchronizing signal generating unit 13.
You. Then, the frame memory write control unit 7
A first frame memory based on an input vertical synchronization signal;
4 and each write operation of the second frame memory 5
Control. Specifically, when the input vertical synchronization signal is
Each time it comes, the frame memory writing control unit 7
Write to switch the frame memory that
Switching of contacts a and b with respect to burn-in selection switch 3
Output a contact switching signal for prompting
For the frame memory 4 and the second frame memory 5
To control whether to perform the write operation.
Outputs the writing control signal. As a result, the first frame
The memory 4 and the second frame memory 5 have an input vertical
It is switched every time a synchronization signal is input,
Write operation of the digitized video signal (data) is performed alternately.
U. The display vertical synchronizing signal generation unit 13
Generates a display vertical sync signal based on the input vertical sync signal.
You. Specifically, the frequency comparison unit 11 receives the input vertical synchronization signal.
Signal and the reference vertical synchronization signal generated by the generator 10.
The frequency is compared with the frequency of the reference vertical synchronization signal. Of this comparison
As a result, the frequency of the input vertical sync signal is
When the frequency is higher than the frequency, the frequency comparing unit 11
Switch to contact e for signal changeover switch 12
A contact switching signal is output to prompt the user to change the contact. Then,
The contact of the synchronization signal switch 12 is switched to e.
Can be As a result, the display vertical synchronization signal generation unit 13
The reference vertical sync signal is used as the display vertical sync signal,
Output to the memory read control unit 8. Meanwhile, the input vertical
The frequency of the sync signal is lower than the frequency of the reference vertical sync signal
The frequency comparison unit 11 sets the synchronization signal switching mode.
A contact that prompts switch 12 to switch to contact f
Outputs the switching signal. Then, the synchronization signal switching
The contact of the switch 12 is switched to f. The result
As a result, the display vertical synchronizing signal generator 13 outputs the input vertical synchronizing signal.
Read out from the frame memory using the signal as the vertical synchronization signal for display.
And outputs it to the control unit 8. Then, the frame memory read control is performed.
The unit 8 controls the first frame based on the display vertical synchronization signal.
Reading of the frame memory 4 and the second frame memory 5
Control the feeding operation. Specifically, the display vertical synchronization signal
Every time is input, the frame memory read control unit
8 switches the frame memory for performing the read operation
In order to achieve this, the contacts c,
Outputs a contact switching signal that prompts switching of d.
First, the first frame memory 4 and the second frame memory
Prompts the memory 5 to start the read operation, respectively.
Outputs a write control signal. As a result, the first frame
Memory 4 and second frame memory 5 are used for display.
It is switched every time the vertical sync signal is input.
Exchanges the read operation of the stored video signal (data).
Do each other. The first frame memory 4 or the second frame memory 4
The data read from the frame memory 5 is
To the field generation unit 14. Then, the subfield generator 14
Is the first frame memory 4 or the second frame memo
To the data of the first bit (MSB) read from memory 5
Generate a first subfield (SF1) based on
A second subfield based on the second bit of data;
(SF2),..., Based on the 8th bit data
Then, an eighth subfield (SF8) is generated. Then, the drive control unit 15 includes a sub-field
The PDP 16 is generated based on the output signal from the
Drive. Specifically, the drive control unit 15
In the field generation unit 14, the relative ratio of the luminance of each SF is set to 12
8 (SF1): 64 (SF2): 32 (SF3): 16
(SF4): 8 (SF5): 4 (SF6): 2 (SF
7): Since 1 (SF8) is set, the first
Read from frame memory 4 or second frame memory 5
Based on the extracted data, each cell of the PDP 16
The video signal is controlled by controlling the discharge light emission of each SF.
Is displayed on the PDP 16. That is, in the first embodiment, the first
Writing to the frame memory 4 or the second frame memory 5
The operation is controlled based on the input vertical sync signal.
The first frame memory 4 or the second frame memory
5 is controlled based on the vertical synchronizing signal for display.
Is to be performed. Therefore, the video signal
A vertical sync frequency different from the frequency of the input
Drive the plasma display device to match the video signal
It is possible to display an image of a desired gradation. In generating a display vertical synchronizing signal,
The input vertical sync signal frequency and the reference vertical sync signal
The frequency is compared with the frequency.
Signal frequency is higher than the reference vertical sync signal frequency
The reference vertical sync signal as the display vertical sync signal.
Output to the frame memory read control unit 8
Has become. Therefore, the discharge light emission operation becomes unstable.
Only when a high vertical sync frequency is input, the reference vertical
The image is driven by driving the PDP 16 based on the synchronization signal.
Can be displayed. As a result, discharge light emission operation is stable
A plasma display device that operates within the range
be able to. In the first embodiment, the first frame
Writing to the memory 4 and the second frame memory 5
Select operation and read operation, respectively,
And the read selection switch 6
As explained in the example to achieve, the frame memory
Write enable signal to read 4 and 5 and read enable
A bull signal may be used. (Embodiment 2) FIG. 2 shows an embodiment of the present invention.
A block diagram showing the configuration of the plasma display device according to state 2.
It is a lock figure. With reference to FIG.
The feature of the plasma display device is the vertical synchronization signal for display.
The generation unit 13 determines the frequency of the input vertical synchronizing signal and the reference vertical synchronizing signal.
The difference between the frequency and the frequency of the
Within the specified range, the input vertical sync signal is
As a direct synchronization signal, the frame memory read control unit 8
Output, and if it is out of the predetermined range, the reference vertical synchronization
The signal is used as the vertical synchronization signal for display, and
The output control unit 8 is configured to output the data. More specifically, the display vertical synchronizing signal generator 1
Reference numeral 3 denotes a reference vertical synchronization signal generator 10 and an input vertical synchronization signal.
Signal and the reference vertical synchronization signal generated by the generator 10.
Difference from the reference vertical synchronization signal frequency
Frequency for determining whether the difference is within a predetermined range
Number difference calculation unit 20 and determination result of frequency difference calculation unit 20
Input vertical sync as display vertical sync signal based on
Signal and the reference vertical sync signal.
And a synchronization signal changeover switch 12. Other configurations are the same as in the first embodiment.
It is like. Here, the table of the above plasma display device is shown.
The operation of generating the indicating vertical synchronization signal will be described. In the display vertical synchronizing signal generator 13,
When generating a vertical sync signal for display, first
The frequency of the input vertical synchronizing signal and the reference vertical
The reference vertical synchronization signal generated by the direct synchronization signal generator 10
And the difference from the frequency of
It is determined whether it is within the fixed range. As a result of this determination, the difference
Is within a predetermined range, the frequency difference calculating unit 2
0 is the contact f for the synchronization signal changeover switch 12.
Outputs a contact switching signal prompting switching. So
Then, the contact of the synchronization signal changeover switch 12 becomes f
Is switched to. As a result, a vertical synchronization signal for display is generated.
The unit 13 uses the input vertical synchronization signal as a display vertical synchronization signal.
And outputs the result to the frame memory read control unit 8. one
On the other hand, if the obtained difference is outside the predetermined range, the frequency
The difference calculation unit 20 controls the synchronization signal changeover switch 12
And a contact switching signal prompting switching to the contact e
Output. Then, the synchronization signal switch 12
Is switched to e. As a result, the display vertical
The synchronization signal generation unit 13 outputs the reference vertical synchronization signal to the display vertical synchronization signal.
Output to the frame memory read control unit 8 as a synchronization signal.
Power. That is, in the second embodiment, the input vertical
The difference between the frequency of the sync signal and the frequency of the reference vertical sync signal
Calculated, and if the obtained difference is within a predetermined range,
If the input vertical sync signal is
Output to the frame memory read control unit 8 and
Outside the specified range, the reference vertical sync signal is
Output to the frame memory read control unit 8 as a period signal
It is supposed to be. Therefore, the discharge light emission operation is stable or
Can tolerate changes in luminance level due to vertical synchronization frequency
Within the range, driving display is performed at the input vertical synchronization frequency,
Instability or frequency where change in brightness level is unacceptable
In the number, it can be driven and displayed based on the reference vertical sync signal.
it can. As a result, it operates within the range where the discharge light emission operation is stable.
And changes in the luminance level due to the vertical synchronization frequency.
Can be reduced. (Embodiment 3) By the way, in the above embodiment,
In the first embodiment and the second embodiment, the frame memory
4 and 5 are performing the read operation, the next frame
The same frame by rewriting
Even though the image of the game is displayed on the PDP 16
Regardless, PDP16
So-called overtaking phenomena such as
There is a risk that. FIG. 3 shows how the overtaking phenomenon occurs.
Shown in FIG. 3 shows vertical writing to the frame memories 4 and 5.
When the sync frequency is higher than the vertical sync frequency for reading
Indicating the control state of the frame memories 4 and 5 in the
FIG. In FIG. 3, a frame memory
Triangular waveforms for writing to and reading from 4, 5
Indicates that the frame memory address has changed.
are doing. Referring to FIG. 3, when the input vertical synchronizing signal is
If an overtaking phenomenon appears when writing a frame of
The PDP 16 is displaying an image over the first frame
The image of the third frame from the middle is displayed.
As a result, scratches appear on the display screen. In the third embodiment, the frame memories 4 and 5
Vertical sync frequency to write to and read vertical sync frequency to
When the wave numbers are different, that is, when performing frame rate conversion
One display image due to the overtaking phenomenon
The screen is divided into upper and lower parts, and images that cover different frames are displayed.
To prevent scratches on the display screen.
It is a proposal. FIG. 4 shows a plug according to a third embodiment of the present invention.
FIG. 2 is a block diagram illustrating a configuration of a zuma display device.
Referring to FIG. 4, a plasma display according to the third embodiment is shown.
A characteristic of the device predicts that an overtaking phenomenon will occur
A point including an overtaking phenomenon occurrence prediction unit 17;
The frame memory write control unit 7
When the overtaking phenomenon is predicted by the
Write operation of the frame memories 4 and 5 is prohibited.
The other configuration is the same as that of the first embodiment.
The same is true. Here, the plasma display device described above
Operation to predict the occurrence of overtaking phenomenon, and frame
The write control operation of the memories 4 and 5 will be described. The input vertical synchronization signal and the reference vertical synchronization signal
When the signal is input, the overtaking phenomenon occurrence prediction unit 17
The frequency of the input vertical synchronizing signal of the wave number comparing unit 11 and the reference vertical
Based on the comparison result with the frequency of the synchronization signal,
Predict the occurrence of an elephant. Specifically, the frequency comparison unit
From 11 the frequency of the input vertical sync signal is the reference vertical sync frequency
When the comparison result signal indicating higher than the number is input
In addition, the overtaking phenomenon occurrence prediction unit 17
And predict the overtaking phenomenon occurrence signal.
Output to the memory write control unit 7. Then, the frame memory writing control
The unit 7 inhibits the writing operation of the frame memories 4 and 5
Write control signals to the frame memories 4 and 5
Output a signal. As a result, the frame memories 4 and 5
No write operation is performed. It is assumed that the overtaking phenomenon is predicted to occur.
The write operation of the frame memories 4 and 5
The child is shown in FIG. Fig. 5 does not cause overtaking
When the passing is predicted, the frame memory
In order to prohibit writing to the frame memories 4 and 5,
5 is a timing chart showing a control state of No. 5; In FIG.
Write and read to and from frame memories 4 and 5
The protruding triangular waveform has a frame memory address
Indicates that it is changing. Referring to FIG. 5, the third
When a frame input vertical sync signal is input,
To prevent scratches from appearing on the screen due to
And the frame memory 5 writes the data of the third frame.
The write operation of the frame memory 5 is controlled to prevent
Is controlled. Also, entering the 9th frame where overtaking occurs
When the vertical synchronization signal is input,
Frame to prevent scratches from appearing on the screen
Make sure that the memory 4 does not write the data of the 9th frame
Next, the writing operation of the frame memory 4 is controlled. As described above, the image of the third frame
The image and the image over the 9th frame are completely PDP
Although it is not displayed on 16, there are scratches caused by overtaking phenomenon
It is less noticeable and is preferable in terms of image quality. That is, in the third embodiment, the passing
The occurrence of an overtaking phenomenon is predicted by the phenomenon occurrence prediction unit 17.
Then, the frame memory writing control unit 7
Write operations of memories 4 and 5 are prohibited
You. Therefore, the occurrence of the overtaking phenomenon can be prevented beforehand.
Can be prevented. Therefore, one display screen is divided vertically.
And the images covering different frames are displayed on the PDP 16.
Never be. As a result, scratches occur on the display screen
Never. In the third embodiment, the overtaking phenomenon
An example in which the occurrence prediction unit 17 is added to the configuration of the first embodiment will be described.
As described above, the overtaking phenomenon occurrence prediction unit 17 is changed to the second embodiment.
The same effect can be obtained by adding to the configuration described above. (Embodiment 4) FIG. 6 shows an embodiment of the present invention.
Overtaking phenomenon of plasma display device according to state 4
It is a figure showing composition of an occurrence prediction part. Referring to FIG.
A feature of the plasma display device according to the fourth embodiment is that
The passing phenomenon occurrence prediction unit 17 is connected to the clock signal input terminal 2
6 counts clock signals input from
First with the input vertical synchronizing signal input from the signal input terminal 27
Counter 21 to be set and counting of counter 21
The value is set to the reference input from the reference vertical synchronization signal input terminal 27.
A first latch 22 for latching based on a vertical synchronization signal;
A reference value setting unit 29 for setting a reference value;
1 and output from the reference value setting unit 29.
Compared with the reference value, and based on the comparison result,
The comparator 23 for predicting the occurrence of
Data 23 is latched based on the input vertical synchronization signal.
The second latch 24 and the frequency comparison result signal input terminal 30
Input vertical sync signal frequency and reference vertical input from
A second latch based on the comparison result signal with the frequency of the signal;
AND gate for determining whether to mask the output signal of
And the other configuration is actual.
This is the same as in the third embodiment. Here, the clock signal is, for example, a frame signal.
A write signal or a read signal to the
It is generated to take the output timing. What
Note that the clock signal is obtained by other means.
You may. The reference value is set in advance by the reference value setting unit 29.
The reference value depends on the frequency of the input vertical sync signal and the reference vertical sync.
The difference between the signal frequency and the frequency of the clock signal
It is set based on the staff. Here, the above plasma display device
The operation of the overtaking phenomenon occurrence prediction unit 17 will be described. The counter 21 counts clocks,
Is output to the first latch 22. In addition,
When the input vertical synchronizing signal 27 is input, the
The period is set (cleared). Then, the first latch 22
Latch the count value of the counter 21 based on the reference vertical synchronization signal.
You. Here, the value latched by the first latch 22 is high.
The higher the reference vertical sync signal is
Overtaking because the incoming vertical synchronization signal 27 is approaching
The possibility that the phenomenon occurs will increase. Also, the first latch
When the value latched at 22 is close to "0",
The direct sync signal is the input vertical sync signal input immediately before
Is approaching. However, the reference vertical sync signal is input
It is input later than the vertical synchronization signal. Also, input vertical
Sync frequency is higher than reference vertical sync signal frequency
The case is assumed. Therefore, if the latched value is
When it is close to "0", the reference vertical sync signal is
It is approaching the incoming vertical sync signal
However, no overtaking phenomenon occurs. The comparator 23 sets a reference value.
Reference value set by unit 29 and output of first latch 22
Compare with value. As a result of this comparison, the first latch 22
When the output value is larger than the reference value, the comparator 23
Predicts that an overtaking phenomenon will occur, for example, "1"
Is output. Next, the second latch 24 is provided with a comparator
23 output value "1" is latched based on the input vertical synchronization signal
And synchronizes with the input vertical synchronizing signal. Then AND
The gate 25 controls the frequency of the reference vertical synchronizing signal and the input vertical synchronizing signal.
Based on the comparison result signal with the frequency of the
It is determined whether to mask the output signal of the latch 24.
Specifically, the frequency of the input vertical sync signal is
The comparison result signal indicating that the frequency is higher than the signal frequency is input.
Then, the AND gate 25 outputs the output of the second latch 24.
Without masking the force signal, the passing signal
Output to the frame memory write control unit 7. On the other hand,
The frequency of the quasi-vertical sync signal is
When a comparison result signal indicating that the
The D gate 25 masks the output signal of the second latch 24
And writes the overtaking phenomenon occurrence prediction signal to the frame memory.
No output to the control unit 7. That is, in the fourth embodiment, the passing
The phenomenon occurrence prediction unit 17 is connected to the clock signal input terminal 26
The input write signal to frame memories 4 and 5
Or a clock signal for generating a read signal.
Input from the vertical synchronization signal input terminal 27
A counter 21 initialized by a vertical synchronization signal;
The count value of the center 21 to the reference vertical synchronization signal input terminal 27.
Latch based on the reference vertical synchronization signal input from the
Latch 22 and a reference value for setting a reference value in advance
Setting unit 29, setting of output value of first latch 22 and reference value
The reference value output from the unit 29 is compared with the reference value.
Comparator that predicts the occurrence of overtaking phenomenon based on
23 and the output value of the comparator 23 as an input vertical synchronization signal.
Latch 24 that latches on the basis of
Of the input vertical synchronizing signal input from the signal input terminal 30
The comparison result signal between the frequency and the frequency of the reference vertical synchronization signal
Whether to mask the output signal of the second latch 24 based on the
And an AND gate 25 for determining whether
Sync signal frequency is higher than reference vertical sync signal frequency
On the condition that overtaking phenomena occur
It has become. Therefore, the time of the reference vertical synchronizing signal
The value of the counter 21 is compared with a reference value according to the position.
Can predict the occurrence of an overtaking phenomenon
You. As a result, the overtaking phenomenon occurrence prediction unit 17
Can be realized on the road. (Embodiment 5) Referring to FIG.
Regarding the operation principle of the plasma display device of the fifth embodiment.
Will be explained. FIG. 7 (a) shows that the input video signal is NTSC
Subfield when the vertical synchronization frequency is 60 Hz
3 shows an example of the operation. In FIG. 7A, 1
The field is 1/60 second and 8 of SF1 to SF8
It is composed of SFs. In addition, each SF
And an address period and a display period. Referring to FIG. 7A, the address period of each SF
In the meantime, the display data read from the frame memories 4 and 5
Write to address electrode of PDP 16 based on data
A pulse is applied. Then, the PD corresponding to this
Wall charges are formed in each cell of P16. And the following table
During the indicated period (sustain period),
Based on the pulse, each cell of the PDP 16 generates a sustain discharge.
Is performed, and an image is displayed. At this time, write
Pulse and sustain pulse
If there is no pulse width, the operation of writing and discharging light emission is
Not determined. So like a personal computer
Have a variety of vertical synchronization frequencies, for example,
When the synchronization frequency is 72 Hz, the time of one field is short.
It becomes. In this case, as in FIG. 7A, eight SFs
If you try to configure one field with
Or the pulse width of the sustain pulse
Will not get. As a result, write and discharge light emission
Operation is not stable. Therefore, for example, as shown in FIG.
By setting the number of SFs to 6, the write pulse and
And the width of the sustain pulse can be set in the same way as in Fig. 6 (a).
You. As a result, writing and discharging operations are stable
Can be done. Further, as shown in FIG.
However, like PAL, the vertical synchronization frequency is as low as 50 Hz
In this case, the time of one field becomes longer. Therefore, the figure
It is possible to generate more SF than 7 (a). Only
In FIG. 7 (c), eight or more SF gradations are
Not necessary. Therefore, the eight SFs are left as they are.
In FIG. 7C, the number of SFs was kept at eight.
However, if you need to increase the number of SF for some reason
Can be implemented by increasing the number of subfields. That is, in the fifth embodiment, the discharge light emission
For the input vertical synchronization frequency in the region where operation becomes unstable,
By changing the SF number, the input vertical
Even if the frequency of the synchronization signal changes, the linearity of the gradation is lost
Operate within the stable range of discharge light emission operation without
To provide a plasma display device capable of
The technology is proposed. FIG. 8 shows a plug according to a fifth embodiment of the present invention.
FIG. 2 is a block diagram illustrating a configuration of a zuma display device. Referring to FIG. 8, the plug of the fifth embodiment
The main feature of the display device is that it generates a vertical synchronization signal for display.
The frequency of the input vertical synchronizing signal of the video signal is
A vertical synchronization frequency measuring unit 41 for measuring the number is provided.
The point and subfield generator 14 are
Generated based on the frequency measurement result by the number measurement unit 41.
That the number of SFs should be changed.
Other configurations are the same as those of the first embodiment. Here, the above plasma display device
The subfield generation operation will be described. Vertical sync cycle
The wave number measuring unit 41 measures the frequency of the input vertical synchronization signal.
You. And the frequency of the input vertical synchronization signal is increasing
In this case, the subfield generator 14 responds
Thus, the number of SFs is reduced. On the other hand, the frequency of the input
If the wave number is decreasing, the subfield generator 1
No. 4 increases the number of SFs accordingly. That is, in the fifth embodiment, SF is generated
The frequency of the input vertical synchronization signal.
The number of SFs to be generated is changed
You. Therefore, when the frequency of the input vertical sync signal is low
To increase the number of gray scale steps to display by increasing the number of SFs
On the other hand, when the frequency of the input vertical sync signal is high
Reduces the number of SFs to perform a stable discharge light emission operation.
Can be (Embodiment 6) FIG. 9 shows an embodiment of the present invention.
A block diagram showing the configuration of the plasma display device according to state 6.
It is a lock figure. With reference to FIG.
The characteristics of the plasma display device are analyzed by the A / D converter 2.
Stores one frame of video signal converted to digital signal
A third frame memory 51 for storing
The contents stored in the memory 51 are read out, and the current video is
Compares with the past image, and based on the comparison result,
A motion detection unit 52 for detecting whether there is
The display vertical synchronization signal generator 13 generates a display vertical synchronization signal.
When playing the video, make sure that the motion
Is to be generated, provided that
Lower the frequency of the direct sync signal and output it.
When the SF is generated by the mode generator 14, the vertical synchronization frequency measurement is performed.
Frequency from the display vertical synchronizing signal generator 13
Low display vertical sync signal is output.
On the condition that the SF to be generated is increased.
The other configuration is the same as that of the fifth embodiment.
The same is true. The display vertical synchronizing signal generation unit 13
Generate a reference vertical sync signal with a lower frequency than the direct sync signal
The reference vertical synchronizing signal generator 10 and the motion detector 52 detect
Based on the output result, input vertical
Either the direct sync signal or the reference vertical sync signal
A synchronization signal changeover switch 12 for selection.
Frame with the selected signal as the display vertical sync signal.
The data is output to the memory read control unit 8. Here, the plasma display device described above
The subfield generation operation will be described. 3rd frame
The memory 51 is converted into a digital signal by the A / D converter 2.
One frame of the converted video signal is stored. Motion
The detection unit 52 is stored in the third frame memory 51
Read current content and compare current video with past video
Then, based on the result of the comparison, it is determined whether or not the image has motion.
Put out. This detection result is output to the display vertical synchronization signal generator 1.
3 given. Then, the display vertical synchronizing signal generator 1
3 is an input vertical based on the detection result of the motion detection unit 52.
Select either the sync signal or the reference vertical sync signal.
And select the selected signal as a vertical sync signal for display.
Output to the memory read control unit 8. Specifically,
The motion of the video is not detected by the
If the image is a still image, the sync signal switch
Twelve contacts are switched to e. As a result, for display
The vertical synchronizing signal generator 13 generates a vertical synchronizing signal for display.
And outputs a low-frequency reference vertical synchronization signal. The vertical synchronizing frequency measuring section 41 displays the vertical
The reference vertical synchronization signal having a low frequency from the synchronization signal generator 13
Is output as the vertical sync signal for display.
Then, the subfield generation unit 14 responds
Increase the SF to be formed. That is, in the sixth embodiment, the current movie
Compare the image with the past image, and from this comparison result,
Detects whether or not there is movement, and also displays vertical synchronization
When generating a signal, check that there is no motion in the video.
Vertical sync for display to occur, provided it is issued
When generating SF by lowering the signal frequency and outputting
Output the low-frequency display vertical sync signal.
On the condition that the number of SFs to be generated is increased.
It has become. Therefore, for a motionless image,
Increase the number of SFs to increase the number of gradation steps to be displayed
Can be done. The present invention is not limited to the above embodiments.
Is not limited to the scope of the claims of the present invention.
Of course, various design changes and modifications can be made in
It is. As is apparent from the above description, claim 1
According to the invention described in the above, the current image and the past image are compared.
And compare the results to see if there is any motion in the video.
Output and generate the display vertical synchronization signal.
Requires that no motion is detected in the video.
To reduce the frequency of the display vertical synchronization signal to be generated.
When generating subfields,
The condition is that a low number of display vertical sync signals are output.
To increase the number of subfields to be generated
For static images, the number of subfields
Increasing the number of gradation steps to be displayed
Can be.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a configuration of a plasma display device according to a first embodiment of the present invention. FIG. 2 is a block diagram illustrating a configuration of a plasma display device according to a second embodiment of the present invention. FIG. 3 is a diagram showing how an overtaking phenomenon occurs. FIG. 4 is a block diagram showing a configuration of a plasma display device according to a third embodiment of the present invention. FIG. 5 is a diagram illustrating a state in which a write operation of frame memories 4 and 5 is prohibited when occurrence of an overtaking phenomenon is predicted. FIG. 6 is a diagram showing a configuration of an overtaking phenomenon occurrence predicting unit of a plasma display device according to a fourth embodiment of the present invention. FIG. 7 is a diagram for explaining the operation principle of the plasma display device according to the fifth embodiment. FIG. 8 is a block diagram showing a configuration of a plasma display device according to a fifth embodiment of the present invention. FIG. 9 is a block diagram showing a configuration of a plasma display device according to a sixth embodiment of the present invention. [Description of Signs] 13 Display vertical synchronization signal generator 14 Subfield generator 16 Plasma display panel (PDP) 52 Motion detector

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁷ identification symbol FI H04N 5/66 101 G09G 3/28 K (58) Investigated field (Int.Cl. ⁷ , DB name) G09G 3/28 G09G 3 / 20 612 G09G 3/20 631 G09G 3/20 660 H04N 5/66 101

Claims (1)

(57) [Claim 1] One field is composed of a plurality of sub-fields having different relative ratios of luminance, and a gradation image corresponding to a multi-gradation video signal is formed on a plasma display panel. A motion detecting means for comparing a current image with a past image and detecting whether or not the image has motion, and generating a display vertical synchronizing signal based on a result of the comparison. A display vertical synchronizing signal generating means for lowering and outputting a frequency of a display vertical synchronizing signal to be generated, on condition that the motion detecting means detects no motion in the video. When generating a field, a subfield for increasing the number of subfields to be generated is provided on condition that a display vertical synchronization signal having a lower frequency is output from the display vertical synchronization signal generating means. A plasma display apparatus comprising a field generation means.