JPH11219152A - Plasma display panel temperature control method and plasma display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a thermal difference from being applied to a PDP due to a temperature difference when high luminance pixels are concentrated in a part of a video signal to be displayed in a plasma display device. . SOLUTION: An average value calculating section 3 removes and samples a low frequency component of a video signal, a histogram calculating section 5 creates a histogram for each luminance range, and a determining section 6 determines whether there is a large change in luminance from the histogram. Is determined, and the control section 7 controls the luminance of the video signal based on the determination result.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a plasma display panel temperature control method and a plasma display device.

[0002]

2. Description of the Related Art FIG. 17 is a block diagram showing a configuration of a conventional plasma display device disclosed in, for example, Japanese Patent Application Laid-Open No. 9-6283. In the figure, reference numeral 101 denotes a plasma display panel (PDP), which includes address electrodes A1 to AM for performing address discharge, X electrodes X1 to XN and Y electrodes Y1 to Y for performing sustain discharge.
N. Reference numeral 102 denotes a predetermined signal (dot clock CLK, display data DATA, vertical synchronizing signal VSYN).
C, horizontal synchronizing signal HSYNC) and a microcomputer 19 described later.
0 is a control circuit that drives the PDP 101 by controlling an address driver 103, an X common driver 104, a Y scan driver 106, and a Y common driver 107, which will be described later.
1 and a panel drive control unit 112. Also 10
Reference numeral 3 denotes an address driver which applies an address pulse PAA and a write pulse PAW to the address electrodes A1 to AM based on a control signal SA from the control circuit 102, and 104 denotes an X based on a control signal SX from the control circuit 102. An X common driver that applies a write pulse PXW and a sustain pulse PXS to the electrodes X1 to XN,
Reference numeral 105 denotes a temperature detector such as a thermocouple that detects the temperature of the X common driver 104 and outputs a detection signal STX to a microcomputer 190 described later. Reference numeral 106 denotes a signal from the Y electrode Y1 based on a control signal SYS from the control circuit 102. A Y scan driver 107 applies a scan pulse PAY to YN. 107 applies a sustain pulse PYS from the Y electrode Y1 to YN via the Y scan driver 106 based on a control signal SYC from the control circuit 102. Y common driver. Reference numeral 108 denotes a temperature detector such as a thermocouple which detects the temperature of the Y common driver 107 and outputs a detection signal STY to a microcomputer 190 which will be described later. A panel heating device such as a heater that heats the PDP 101 when the temperature is low is a temperature detector that detects the temperature of the PDP 101 and outputs a detection signal STP to a microcomputer 190 described later. 111 is a dot clock C
LK, the display data DATA, and the frame data corresponding to one frame in the display data DATA are divided into a plurality of subframe data based on the control of the microcomputer 190, and a control signal SA based on the subframe data is transmitted to the address driver 103. This is a display data control unit to be output, and includes a frame memory 120, a subtractor 121, and a frame memory 122, which will be described later.

A reference numeral 112 outputs control signals SYS, SYC, and SX to the Y scan driver 106, the Y common driver 107, and the X common driver 104, respectively, based on the control of the vertical synchronization signal VSYNC, the horizontal synchronization signal HSYNC, and the microcomputer 190. Panel drive control unit,
It comprises a scan driver control unit 130 and a common driver control unit 131, which will be described later. Reference numerals 120 and 122 denote frame memories for temporarily storing the input display data DATA for one frame at a time. While the display data is being written to one of 120 and 122, the other is written earlier. Is read out.
A subtractor 121 corrects the number of gradations of the display data DATA stored in the frame memories 120 and 122 under the control of the microcomputer 190. 130 is a scan driver control unit, and 131 is a common driver control unit. 1
Reference numeral 40 denotes a voltage conversion unit that applies high-voltage power to each driver, and includes a Vc power supply unit 141, a Vw power supply unit 142, a Vsc power supply unit 143, a Vy power supply unit 144, and a Vx power supply unit 145. Reference numeral 150 denotes an EP-ROM, and the PDP 101
Has a drive waveform region 150A in which the waveform of each pulse applied to the memory is stored in advance and outputs a desired pulse waveform under the control of a microcomputer 190 described later, and a sustain pulse number setting region 150B. Reference numeral 160 denotes an interior atmosphere temperature detector that detects an ambient temperature in the apparatus and outputs a detection signal to a microcomputer 190 described below. Reference numeral 170 denotes an LED that displays a warning. Reference numeral 171 denotes a control of the microcomputer 190 described later. And LED
170 is a control circuit for controlling the display, 180 is an air cooling device for cooling the entire device, 181 is a control circuit for controlling the operation of the air cooling device 180 under the control of a microcomputer 190 described later, and 191 is a control circuit for the air cooling device 180 described later. A relay control unit for inhibiting application of a high voltage to the voltage conversion unit 140 and the control circuit 102 under the control of the microcomputer 190, a power consumption detection unit 192 for detecting the power consumption of the entire plasma display device, 190 is a microcomputer.

Next, the operation will be described. Display data DATA input to the control circuit 2 from the display data input unit
Is stored in one of the frame memories 120 and 122. The data on the frame memory is divided and read for each sub-frame in order to perform multi-tone display.
When 256 gradation display is performed, one frame is divided into eight subframes, and the light emission time of each subframe is set to 1: 2: 4: 8: 16: 32: 64: 128, and the light emission of the subframe is performed. , 0 to 255 are expressed by a combination of non-light emission. First, the light emission time is 128
Will be described with reference to FIG. 18 when displaying a subframe corresponding to. FIG. 18 is a timing chart showing an operation for one subframe of the conventional plasma display device.

First, all display cells are erased during the reset period. The reset period includes a full write period and a self erase period. First, in the entire writing period, the level of all the Y electrodes Y1 to YN is set to 0 V, and the writing pulse P is applied to all the X electrodes X1 to XN.
XW is applied. A write pulse PAW is applied to all the address electrodes A1 to AM in synchronization with the write pulse PXW. Write pulses PXW and P
The AW causes a discharge between all the X electrodes X1 to XN and all the address electrodes A1 to AM. Thereafter, during the self-erasing period, the level of all the X electrodes X1 to XN and all the address electrodes A1 to AM is set to 0 V, so that the discharge is performed until the wall charges disappear in all the display cells, and the erasing is completed. .

Next, in the address period, only the cells to emit light are discharged to accumulate wall charges.
A scan pulse PAY is applied to the Y electrode sequentially from Y1 to YN in a time-division manner.
Based on the subframe data corresponding to 28, an address pulse PAA is applied to the address electrodes corresponding to the cells to emit light among the address electrodes A1 to AM. During the address period, all X electrodes X1 to XN are maintained at a predetermined X address voltage. As a result, first, a priming address discharge is generated between the Y electrode corresponding to the cell to be caused to emit light and the address electrode, and the main address discharge is generated between the corresponding X electrode and Y electrode by using this as a pilot light (priming). Occurs and accumulates wall charges.

[0007] Finally, in the sustain discharge period, the discharge is continuously performed so that the light emitting time becomes 128 in the light emitting cell designated in the address period. Pulses PXS and P alternately for all X and Y electrodes
YS is applied, and a sustain discharge is performed in the light emitting cells in which the wall charges are accumulated during the address period, and display is performed. Here, the greater the number of sustain pulses PXS and PYS, the higher the luminance in the subframe.

According to the sequence including the reset period, the address period, and the sustain discharge period, the light emission time is 12
The sub-frame corresponding to 8 is displayed. Subsequently, similarly, by displaying the sub-frames having the light emission times of 64, 32, 16, 8, 4, 2, and 1, the video of one frame can be displayed with 256 gradations.

In the conventional plasma display device configured as described above, the surface temperature of PDP 101 is detected by temperature detector 110. The temperatures of the X common driver 104 and the Y common driver 107 are detected by temperature detectors 105 and 108. Where P
The brightness of the DP 101 decreases in proportion to the temperature rise of the PDP 101, and decreases in proportion to the temperature rise of the X common driver 104 and the Y common driver 107. The detection signals S obtained from the temperature detectors 110, 105, and 108 are obtained by using the respective proportional constants obtained in advance by measurement.
By processing the TP, STX, and STY by the microcomputer 190, the amount of decrease in luminance can be found. The microcomputer 190 performs control so as to increase the luminance so as to correct the decrease in the luminance. As a method for increasing the luminance, there are a method of controlling the number of pulses, a method of controlling the sustain voltage, and a method of controlling the display data section as described below.

The method of controlling the number of pulses utilizes the fact that the number of sustain pulses is proportional to the brightness of the PDP 101. The microcomputer 190 calculates the number of sustain pulses to correct the decrease in luminance due to the temperature change, and calculates the result as E
This is a selection address signal for the sustain pulse number setting area 150B in the P-ROM 150. In the EP-ROM 150, the number of sustain pulses for each subfield with respect to the reference number of sustain pulses is set. Based on this, the corrected number of sustain pulses in each subfield is output to the panel drive control unit 112. The common driver control unit 131 of the panel drive control unit 112 outputs a sustain pulse corresponding to the corrected number of sustain pulses, and corrects a decrease in brightness of the PDP 101 and each driver due to a rise in temperature.

Next, in the method of controlling the sustain voltage, the voltages of the sustain pulses PXS and PYS (sustain discharge voltage VS) and P
The fact that the luminance of the DP 101 is proportional is used. The microcomputer 190 is connected to the sustain discharge voltage reference voltage output section OUT, which enables control of the sustain discharge voltage VS. Therefore, the microcomputer 190 compensates for a decrease in luminance due to a temperature change. The voltage is calculated, and the result is output from the sustain discharge voltage reference voltage output section OUT to an external high voltage generator and serves as a reference for a voltage value to be input to the driving high voltage input section INV. The sustain discharge voltage VS is set by the driver control unit 131, and the decrease in luminance due to the temperature rise of the PDP 101 and each driver is corrected.

The method of controlling the display data portion utilizes the fact that the gradation value of the display data DATA is proportional to the luminance of the PDP 101. The microcomputer 190 is connected to the display data control unit 111,
In 1, the gradation value of each light emitting cell is subtracted based on the subtraction data of the microcomputer 190. The display data DAT input from the display data input unit IN in the vertical synchronization period n
A is stored and held in the frame memory 120. In the next vertical synchronization period n + 1, after subtracting the gradation value for the luminance correction from the data in the frame memory 120 via the subtractor 121, the data is output to the address driver 103 as display data included in the control signal SA, and the image is stored in the PDP 101. Is displayed. The display data DATA input from the display data input unit IN in the vertical synchronization period n + 1 is stored and held in the frame memory 122. Display data processing is performed by alternately operating the above operations on the two frame memories 120 and 122, and a series of these operations corrects a decrease in luminance due to an increase in temperature.

In the conventional plasma display device configured as described above, the plasma display device including the PDP 101 is used when the ambient temperature for operating the PDP 101 is abnormally high or when an unexpected trouble occurs. If the temperature of the device rises abnormally and exceeds the temperature rating of the circuit element, and the circuit element may be damaged, the operation can be performed to prevent this. Surface temperature of PDP 101, X common driver 10
4. The temperature of the Y common driver 107 is detected by temperature detectors 110, 105, and 108, respectively, and detection signals STP, STX, and STY are output to the microcomputer 190. Further, the ambient temperature inside the apparatus is detected by the ambient temperature detector 160 inside the apparatus and output to the microcomputer 190. When at least one of the temperature information obtained by the above detection signals exceeds the set threshold value, the microcomputer 190 performs control to protect the plasma display device. Specifically, a method of operating an air cooling device 180 such as a fan to perform an air cooling process,
There is a method of warning the user to that effect by blinking, and a method of prohibiting power supply to the plasma display device.

In the method of performing the air cooling process, the microcomputer 1
The temperature information (detection signals STP, STX,
If any one of STY and the ambient temperature detector in the apparatus exceeds the threshold value, the microcomputer 190 controls the air cooling apparatus 18 via the control circuit 181 based on the result.
Operate 0. This operation is continued until all of the temperature information input to the microcomputer 190 falls below the threshold.

In the method of giving a warning by blinking the LED, when any one of the temperature information inputted to the microcomputer 190 exceeds the threshold value, the microcomputer 190 sends the LED 170 via the control circuit 171 based on the result. Flashes. This operation is continued until all of the temperature information input to the microcomputer 190 falls below the threshold.

In the method of prohibiting power supply to the plasma display device, if any one of the temperature information input to the microcomputer 190 exceeds a threshold value, the microcomputer 190 determines the relay control unit 1 based on the result.
By operating 91, the high-voltage line for driving is temporarily cut off.
This operation is continued until all of the temperature information input to the microcomputer 190 falls below the threshold.

With the above operation, when the temperature of the plasma display device including the PDP 101 rises abnormally, the plasma display device can be protected.

In such a conventional plasma display device, a change in the discharge characteristics of the PDP due to a rise in temperature and a change in the characteristics of the driver are corrected so that the display characteristics are not affected even if the temperature of the PDP and the driver rises. Display can be performed without giving. Further, the plasma display device including the PDP can be protected from an abnormal rise in temperature.

[0019]

In the above-described conventional plasma display device, the temperature rise of the PDP is detected by using a detector such as a thermocouple, and the operation of the air-cooling device and the LED are performed.
The plasma display device is protected by the warning by the above and the power cutoff by the relay control device. However,
Depending on the displayed video signal, the temperature of only a part of the PDP panel rises, which may cause thermal stress. When PDP is deformed by thermal stress, PDP
There is an adverse effect such as deterioration of the display performance and shortening of the service life, and in the worst case, the PDP may be damaged.

The PDP has a certain area, and P
Since the main material of DP is a material that has a lower thermal conductivity than metal such as glass, the temperature of PDP is not the same in all places of one PDP, but also in each part in one PDP. Temperatures can vary widely. For example, when a plasma display device is used as a display for a computer, it often happens that a screen is displayed such that a relatively dark background includes a bright window. When only a part of the image in the image is bright and the luminance changes abruptly as in this window (such an image is referred to as an image having a large luminance gradient), the bright part is compared with the dark part. More heated. Therefore, when such an image is continuously displayed, the temperature difference between a bright portion and a dark portion on the PDP increases, and a relatively high temperature portion in the PDP expands more than a low temperature portion.
Thermal stress occurs in P. Since the temperature difference is more likely to occur as the screen size of the PDP is larger, this is a major problem particularly in a large-screen display device. Here, in a method using a detector such as a thermocouple as in a conventional plasma display device, a temperature difference in the PDP cannot be detected unless a plurality of detectors are attached to the PDP. Also,
As the screen size of the PDP increases, the number of necessary detection points increases and the number of detectors increases, so that the cost increases.

The present invention has been made to solve the above-described problems, and detects an image that causes a large temperature difference in a PDP without using a temperature detecting means such as a thermocouple. An object of the present invention is to provide a plasma display device and a temperature control method for a plasma display panel which are low-cost and have a long life with little deterioration of image quality by controlling the temperature difference in the PDP to be small.

[0022]

According to the present invention, there is provided a plasma display apparatus comprising: driving means for driving a plasma display panel based on a video signal input from the outside; and a plasma display panel driven by the driving means for displaying. Means for removing a low-frequency component of the video signal, histogram calculation means for creating a histogram for each gradation range of the video signal from which the low-frequency component has been removed, and brightness gradient from the histogram created by the histogram calculation means. A determination unit for determining a violent image; and a control unit for controlling the driving unit based on a determination result of the determination unit.

Further, the number of sustain pulses in the driving means is controlled by the control means.

Still further, a video signal processing means for processing a video signal inputted from the outside, a driving means for driving a plasma display panel based on the video signal processed by the video signal processing means, and a driving means for driving the plasma display panel And a means for removing low-frequency components of the video signal processed by the video signal processing means, and a histogram calculation for creating a histogram for each gradation range of the video signal from which the low-frequency components have been removed. Means, a judging means for judging an image having a sharp change in luminance from the histogram created by the histogram calculating means, and a control means for controlling the video signal processing means based on the judgment result of the judging means. .

Further, there is provided storage means for holding the control level information of the control means for a certain period after the main power is turned off.

A driving means for driving the plasma display panel based on an externally input video signal;
A plasma display panel that performs display by being driven by the driving unit, a unit that removes a low-frequency component of the video signal, and a histogram calculation unit that creates a histogram for each gradation range of the video signal from which the low-frequency component has been removed, The image processing apparatus further includes a determining unit that determines a video having a sharp change in luminance from the histogram created by the histogram calculating unit, and a communication unit that outputs a determination result of the determining unit to the outside.

Further, the apparatus further comprises a panel characteristic storing means for storing the characteristics of the plasma display panel measured in advance, and the judgment reference value of the judging means is made variable according to the contents of the panel characteristic storing means. It is.

Further, there is provided a coefficient storage means for giving different control coefficients to the control means depending on whether the input video signal is a television signal or a computer signal.

Further, the apparatus has a temperature detecting means for detecting the ambient temperature of the plasma display device, and is configured to correct the judgment reference value of the judging means in accordance with the output of the temperature detecting means.

Further, in the temperature control method for a plasma display panel according to the present invention, a step of removing a low frequency component of a video signal and a histogram calculation for creating a histogram for each gradation range of the video signal from which the low frequency component has been removed are provided. And a control step of controlling the brightness of the plasma display panel based on a determination result of the determination step, based on the determination result of the determination step. .

Further, the number of sustain pulses of the plasma display panel is controlled by the control step.

Further, the amplitude of the video signal input to the plasma display panel is controlled by the control step.

[0033]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In a plasma display device according to an embodiment of the present invention, a low-frequency component of a video signal is removed, and a histogram for each luminance of a sampled video signal is obtained. Since the brightness of the PDP is controlled by detecting the image that causes the difference, it works to reduce the temperature difference in the PDP.

Further, when controlling the brightness of the PDP, the brightness of the PDP is controlled by controlling the number of sustain pulses, so that the temperature difference in the PDP is reduced by a simple circuit configuration.

Further, since the brightness of the PDP is controlled by controlling the video signal processing means, the temperature difference in the PDP can be obtained by adding only a small circuit to the conventional plasma display apparatus having the video signal processing means. Work to reduce.

Further, the control information of the control means is retained in the storage means for a certain period of time even after the main power supply is turned off, so that even if the main power supply is connected again after a relatively short time, appropriate control is performed in the PDP. Works to reduce the temperature difference.

Further, by outputting the judgment result of the judging means to the outside by the communication means, the video signal is controlled on the side of the external signal source. Works to reduce the temperature difference.

The characteristics of the plasma display panel measured in advance are stored in the panel characteristics storage means, and the judgment reference value of the judgment means is made variable in accordance with the contents of the panel characteristics storage means. Even when there is a variation in the characteristics, or when there is a variation in the temperature characteristics depending on the part in the panel, it works to appropriately reduce the temperature difference in the PDP according to the respective temperature characteristics.

Also, by changing the control coefficient given to the control means from the coefficient storage means depending on whether the video signal inputted from the outside is a television signal or a computer signal, the display quality is improved by the display in accordance with the type of the signal. It serves to minimize the effect and reduce the temperature difference within the PDP.

Further, by correcting the judgment value of the control means in accordance with the output of the temperature detecting means for detecting the ambient temperature of the plasma display device, the PDP in the PDP can be effectively adjusted in accordance with the environment in which the device is installed and the use condition. It works to reduce the temperature difference.

Hereinafter, the present invention will be specifically described with reference to the drawings showing the embodiments. Embodiment 1 FIG. First, a first embodiment of the present invention will be described. FIG. 1 is a configuration diagram of a plasma display device according to a first embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a driving circuit, and 2 denotes a plasma display panel (PD).
P), 3 is an average value calculation unit, 4 is an area division unit, 5 is a histogram calculation unit, 6 is a determination unit, and 7 is a control unit.

Next, the operation will be described. First, the video signal and the synchronization signal are input to the drive circuit 1 and also to the average value calculation unit 3. The driving circuit 1 stores an input video signal in a frame memory in the driving circuit 1 in the same manner as in the conventional plasma display device, reads out the divided image signals for each subfield, and applies the divided signals to the X electrode, the Y electrode, and the address electrode of the PDP 2 respectively. A driving pulse is given in the same manner as in a conventional plasma display device. The PDP 2 emits light based on the drive pulse given from the drive circuit 1 and displays an image.

The average value calculating section 3 averages R, G, and B of the color video signal as a pre-process to obtain a monochrome video signal containing only luminance information, and then converts the monochrome video signal in the vertical and horizontal directions. By taking the average value of the determined number of pixels, a video signal sampled with a smaller number of pixels than the original video signal is obtained, and low-frequency components of the video signal are removed. The purpose of removing the low frequency component of the video signal is to remove the influence of the luminance distribution in a relatively small area. For example, when a PDP is used as a computer display, there are many opportunities to display characters on a screen. A character contains both high and low brightness pixels in a relatively small area. It is considered that the presence of high-brightness pixels and low-brightness pixels in a relatively small area does not lead to the occurrence of a problematic large temperature difference. This is because the heat of the panel is transmitted relatively quickly within a small area, and no large temperature difference occurs within that range.

FIG. 2 is an explanatory diagram showing an example of the operation of the average value calculating section 3. In this example, the video signal is equivalent to XGA (10
(24 pixels × 768 pixels) is shown. In the figure, (a) represents a video signal of one frame, and the upper left of a video composed of 1024 pixels in the horizontal direction and 768 pixels in the vertical direction is enlarged and shown. (b) represents a sampled video signal of one frame after being processed by the average value calculation unit 3, and is composed of 64 pixels in the vertical direction and 48 pixels in the horizontal direction.
The average value calculation unit 3 calculates the average of the luminance values over the range of the hatched portion in FIG.
It is assumed that the brightness value of the pixel in the hatched portion corresponding to the position in FIG. By repeating the above processing over the entire frame, the luminance values of all the pixels in FIG. 2B are obtained.

By averaging the luminance values of 16 pixels in the vertical and horizontal directions, even if the luminance value distribution is such that high-luminance pixels and low-luminance pixels are mixed within a range of 16 × 16 pixels. It does not affect the calculation of the luminance distribution described later. Further, by using the average value of the luminance values of 256 pixels, the number of pixels of the video signal to be processed is reduced to 1 / 256th of the original image, so that the circuit scale required for the processing described below is reduced. Alternatively, the processing speed can be increased. It should be noted that the number of pixels for which the average value of the luminance values is to be determined depends on the total number of pixels of the PDP, the size of the PDP, and the thermal conductivity of the material constituting the PDP.

Next, in the area dividing section 4, the average value calculating section 3
Fig. 3 shows the sampled video signal processed by
Is divided into several regions as shown in In the example shown in the figure, a sampled video signal composed of 64 pixels in the horizontal direction and 48 pixels in the vertical direction is divided into 12 regions. By performing the processing described below for each of the divided areas, it is possible to determine which area in the video the image having a large luminance difference to be detected belongs to, so that a temperature difference occurs at which position in the PDP. Can be determined by the processing described below.

Next, the histogram calculator 5 calculates a histogram of luminance values for each of the regions obtained from the region divider 4 by calculation. This will be described with reference to FIGS. FIG. 4 is a diagram showing an example of a region and a histogram corresponding to the region, and has no luminance gradient. FIG. 5 is also a diagram showing an example of a region and a histogram corresponding to the region, in which the luminance gradient is large.
In each figure, (a) is an example of the region, (b)
Is a histogram obtained from (a). Here, the luminance value is divided into three ranges of low luminance, medium luminance, and high luminance for simplicity. In FIG. 4A and FIG. 5A, pixels represented by black have low luminance, pixels represented by oblique lines have medium luminance, and pixels represented by white have high luminance. FIG. 4B and FIG. 5B show the respective histograms. In practice, the histogram is created by dividing the luminance value into more ranges. For example, when the luminance value is divided into eight, if the luminance is 256 gradations (0 to 255), 0 to 31, 32 to 63, 6
4-95, 96-127, 128-159, 160-1
It is sufficient to divide the luminance value into eight equal parts, such as 91, 192 to 223, and 224 to 255, and to make a histogram of the number of pixels in each luminance value range.

Next, in the judgment section 6, the histogram calculation section 5
Whether there is a large luminance gradient based on the histogram data obtained from is determined by a method described later. Since there is one histogram for each divided area, a determination is first made on the histogram for each area, and then the values of the respective luminance ranges of the histograms of the two adjacent areas are added to obtain two histograms. The histograms are combined, and the combined histogram is also determined by a method described later. By combining the histograms of the two adjacent regions in this way, it is possible to detect a luminance gradient that straddles the two adjacent regions. Further, the histogram of the entire video signal of one frame can be obtained by adding the values of the respective luminance ranges for all the histograms of one frame. By making a determination on the histogram of the entire frame by the method described later, the determination can be made more reliably.

Next, specific criteria will be described. In an image having a large luminance gradient, both high-luminance pixels and low-luminance pixels are present in one histogram, and the number of intermediate-luminance pixels is small. Therefore, when the ratio of the number of pixels of intermediate luminance to all pixels is smaller than a certain value and the number of pixels of high luminance is larger than a certain value, it is determined that there is a large luminance gradient.

As described above, the above determination is performed on each of the histogram of each area, the histogram obtained by combining the histograms of the adjacent areas, and the histogram of the entire screen, and it is determined that at least one histogram has a large luminance gradient. When the determination is made, the determination unit 6 outputs a signal indicating “luminance gradient exists” to the control unit 7, and when it is determined that there is no large luminance gradient in all histogram determinations, the control unit 7 outputs “no luminance gradient”. Is output.

Finally, the control unit 7 controls the driving circuit 1 based on the judgment result obtained by the judgment unit 6 and controls the driving circuit 1 to reduce the number of sustain pulses in each subframe when the window image is displayed. By lowering the display luminance of the panel, the occurrence of a temperature difference in the panel can be suppressed. Since the luminance is proportional to the number of pulses, the luminance in the standard state (in a state in which the luminance control is not performed) is 100%, and when the luminance is desired to be x%, the luminance in the standard state (in a state in which the luminance control is not performed) is set. Let Ps be the number of pulses Pc and Pc be the number of pulses when control is performed. Pc = Ps × x /
It should be 100. Actually, since the number of pulses is an integer, the control is performed stepwise. Since a large temperature difference occurs in the PDP when a video signal having a luminance gradient is continuously displayed for a certain period, the actual control is performed based on the presence or absence of the luminance gradient in a certain period in the past. It needs to be done in a dependent manner. A specific control method will be described with reference to FIG.

FIG. 6 is a flowchart showing the operation of the control unit according to the first embodiment of the present invention. S001 is an initial setting, and is executed only once when the power of the plasma display apparatus is turned on. Here, W_CNT and NW
_CNT are variables whose values are held inside the control unit 7, and each of them takes an integer value. Each variable contains information on the luminance gradient in the past frame. In S001, the variable W_CNT and the variable NW
_CNT is initialized, 0 is given to the variable W_CNT as an initial value, and a certain integer WMAX is given to the variable NW_CNT.

In the subsequent step S002, the determination unit 6 obtains the determination result of one frame regarding the presence or absence of the luminance gradient. In B001, according to the determination result obtained in S002,
If there is a luminance gradient, the process branches to S003, and if there is no luminance gradient, the process branches to S007.

First, when there is a luminance gradient, that is, at S00
The case of branching to 3 will be described. In S003, both the variable W_CNT and the variable NW_CNT are incremented by one. In the next B002 and S004, when the variable NW_CNT is equal to or larger than WMAX, the variable NW_CNT is set to WMAX.
Is assigned. In B003, when the variable W_CNT is equal to or greater than WMAX, the process proceeds to S005, where 0 is substituted for the variable W_CNT, and then the driving circuit 1 is controlled in S006 to control the brightness of the PDP 2. In S006, the control value of the luminance is reduced by one step. That is, the number of sustain pulses in the drive circuit 1 is reduced by one stage set in advance. As a result, when the control value falls below the preset lower limit value, nothing is performed. At the stage when the above processing is completed, S002
And waits until the determination result of the next frame is obtained.

Next, when there is no luminance gradient, that is, at S00
The case of branching to 7 will be described. In S007, both the variable W_CNT and the variable NW_CNT are decreased by one. In the next B004 and S008, the variable W_CNT is set to 0.
In the following cases, 0 is substituted for the variable W_CNT. B0
At 05, when the variable NW_CNT becomes 0 or less, S00
Go to 9 and assign WMAX to the variable NW_CNT and then S0
The luminance of the PDP 2 is controlled by controlling the drive circuit 1 at 10. In S010, the control value of the luminance is increased by one level. As a result, when the control value exceeds the upper limit value (the number of pulses in the standard state), nothing is performed. When the above processing is completed, the process returns to S002, and waits until the determination result of the next frame is obtained.

Control is performed by repeating the above processing for each frame. This control method will be described with reference to FIG. FIG. 7 is a diagram illustrating an example of an operation of the control unit according to the first embodiment of the present invention, and is a graph of a control state of a variable W_CNT, a variable NW_CNT, and a control value (standard state is set to 0 level). . The horizontal axis represents time in the number of frames. In the example shown in the figure, the state with the luminance gradient continues for 25 frames and then changes without the luminance gradient. As can be seen from the figure, WMAX
If the situation with the luminance gradient continues during the frame, control is performed so that the control value is reduced by one step. The control is performed for each WMAX frame even at the fastest, and the control is performed correctly without being affected even if the video changes at high speed during several frames. In the graph of FIG. 7, WMAX is set to 10 for simplicity, but in practice, it is desirable to change the luminance about once every few seconds to prevent flicker, and WMAX is about several hundreds.

By controlling as described above, the PD
When an image having a luminance gradient such that a temperature difference occurs in P is displayed, the luminance is decreased stepwise, and when an image having no luminance gradient is displayed, the luminance is increased stepwise ( Will be returned to the standard state)
It is possible to prevent a large temperature difference from occurring in the PDP.

Embodiment 2 Next, a second embodiment of the present invention will be described. In the first embodiment, the control unit 7 controls the drive circuit 1 to control the display brightness of the PDP 2 to reduce the number of sustain pulses.
, The display contrast can be reduced by signal processing. In the plasma display device according to the first embodiment, only a video signal that has been digitized is assumed as an input. However, in a conventional plasma display device, various inputs are assumed, for example, a video signal is decoded. Many types include a signal processing circuit having a function of converting an analog video signal into a digital video signal by A / D conversion, performing inverse gamma conversion, performing brightness adjustment, and contrast adjustment. Thus, by controlling the contrast adjustment function in such a signal processing circuit, the configuration is such that the contrast is reduced when an image that causes a large temperature difference is detected. Hereinafter, such an embodiment will be described. FIG. 8 is a configuration diagram of a plasma display device according to a second embodiment of the present invention, wherein 1 to 7 are the same as those in the first embodiment, and 8 is a video signal processing circuit for controlling the contrast of the video signal. Function.

The operation of the thus configured plasma display device will be described. Drive circuit 1, PDP
2. The operations of the average value calculation unit 3, the area division unit 4, the histogram calculation unit 5, and the determination unit 6 are the same as those in the first embodiment. The control unit 7 controls the brightness of the PDP 2 by controlling the contrast adjustment function in the video signal processing circuit 8 based on the determination result of the determination unit 6 to adjust the contrast. The contrast adjustment is performed by multiplying the brightness value before adjustment by the contrast value as the adjusted brightness value. Therefore, the luminance in the standard state (the state in which the luminance control is not performed) is 100% and the luminance is x%.
If it is desired that the contrast value be Cc, then Cc = x / 100.

The control procedure is performed by controlling the contrast stepwise according to, for example, the flowchart of FIG. 6, as in the first embodiment. Accordingly, when an image having a luminance gradient such that a temperature difference occurs in the PDP is displayed, the luminance is reduced stepwise, and when an image having no luminance gradient is displayed, the luminance is stepwise. Raised (returned to standard state)
That is, it is possible to prevent a large temperature difference from occurring in the PDP.

Embodiment 3 Next, a third embodiment of the present invention will be described. In the plasma display device, when the main power supply is turned off, it takes some time for the PDP to cool down to a temperature close to room temperature. For this reason, if the user turns off the main power supply to interrupt the use of the plasma display device, and then reconnects the main power supply after a relatively short time and resumes use, or a relatively short power outage occurs. If this occurs, a temperature gradient may remain in the PDP. In the third embodiment, even when the main power supply is temporarily cut off as described above, the brightness control is appropriately performed to prevent the occurrence of the temperature difference in the PDP. FIG. 9 is a configuration diagram of a plasma display device according to Embodiment 3 of the present invention. In FIG. 9, 1 to 7 are the same as those of Embodiment 1, and 9 is for storing the control state of the control unit 7. Storage device, for example, a RAM. Reference numeral 10 denotes a backup circuit for holding the contents of the storage device 9 for a certain period without depending on the main power supply.

The storage device 9 stores, for example, a current brightness control value as a control state of the control unit 7, and also stores a check pattern for determining whether the stored content is valid.

The backup circuit 10 supplies power for the storage device 9 to retain the stored contents from when the main power is turned off. FIG. 10 shows an example of the circuit of the backup circuit 10. In the figure, a circuit enclosed by a broken line corresponds to the backup circuit 10, 20 is a diode, and 21 is a capacitor. When the main power supply is connected, a current flows through the diode 20 and charge is accumulated in the capacitor 21. When the main power is cut off, the capacitor 21
A current flows through the storage device 9 until the charge is discharged from the storage device 9. When the capacitor 21 is completely discharged while the main power is cut off, the power is not supplied to the storage device 9 and the stored contents are erased. Approximate time Tm from turning off the main power supply to erasing the stored contents is determined by the capacity of the capacitor 21. It is assumed that the capacitance of the capacitor 21 is selected such that the time Tm is longer than the time Tp required for the PDP panel to be cooled naturally and become substantially equal to room temperature after the main power supply is cut off.

The operation of the control unit 7 having such a configuration will be described. When the main power is turned on, the control unit 7 reads out the check pattern storage location in the storage device 9 and determines whether a prescribed check pattern is stored.
If the check pattern is not stored, a sufficient time has elapsed since the last power-off, and the PDP has been cooled to a temperature substantially equal to the room temperature. Initialization is performed, a check pattern is written, and the control value is set to a specified initial value. When the check pattern is stored, the time elapsed since the last main power-off is short and the PDP is not cooled, so the brightness control value in the storage device 9 is read and set as the control value. After the above operation is performed when the main power is turned on, the operation shifts to a normal operation. In normal operation, the control unit 7 stores the updated control value in the storage device 9 every time the control value is updated. Other operations of the control unit 7 are the same as those of the first embodiment.

In the plasma display device configured as described above, even if the main power supply is turned off and the main power supply is connected again in a relatively short time, control is performed using the held control values. A large temperature difference can be prevented from occurring. Further, even when a long time has elapsed since the main power supply was turned off and the PDP is at a temperature substantially equal to room temperature, the held control value can be discarded and the control can be appropriately performed from the initial value. .

Embodiment 4 Next, a fourth embodiment of the present invention will be described. The fourth embodiment is different from the first to third embodiments in that the brightness is controlled outside the plasma display device, thereby reducing the cost of the device. Since an image in which a temperature difference is a significant problem often occurs when a plasma display device is used as a computer display, the plasma display device determines an image in which a temperature difference occurs and outputs an image signal as a determination result. It can be configured to transmit the data to the computer that performs the processing, and perform the processing on the computer to perform the brightness control. FIG. 11 is a configuration diagram of a plasma display device according to a fourth embodiment of the present invention. In the drawing, reference numerals 1 to 6 denote the same as in the first embodiment.
Is a communication unit that transmits the determination result of the determination unit 6 to the outside,
Reference numeral 12 denotes a signal from a personal computer (PC), a workstation, or the like, which is outside the plasma display device of the present embodiment, supplies a video signal to the plasma display device, and receives a determination result from the communication unit 11 and performs processing. Source.

The operation of the plasma display device thus configured will be described. Drive circuit 1, PDP
2. The operations of the average value calculation unit 3, the area division unit 4, and the histogram calculation unit 5 are the same as those in the first embodiment. The determination unit 6 determines whether or not there is a luminance gradient for each of the histogram of each area, the histogram obtained by combining the histograms of the adjacent areas, and the histogram of the entire screen, as in the embodiment. The determination result is transmitted including the position information of the area having the luminance gradient. Communication unit 1
In step 1, the information received from the determination unit 6 is transmitted to an external signal source 12.
To send to. Processing is performed on the side of the external signal source 12, and based on the information received from the communication unit 11, the display state is changed so that the luminance of the window display portion corresponding to the position where the luminance gradient exists becomes low. For example, by changing the display color of the window portion, it is possible to control the luminance so as to prevent the occurrence of the temperature difference without changing the portion other than the corresponding window.

Embodiment 5 Next, a fifth embodiment of the present invention will be described. The temperature characteristics of PDP may vary from panel to panel due to manufacturing variations.
There is a possibility that the temperature characteristics vary depending on the part in a single PDP. The fifth embodiment is configured so that appropriate luminance control can be performed even when there is such variation. FIG. 12 is a configuration diagram of a plasma display device according to Embodiment 5 of the present invention.
In the figure, 1 to 7 are the same as in the embodiment, and 13
Is a PDP characteristic storage unit that stores the criterion in the determination unit 6, and is a non-volatile memory such as a PROM.

In the plasma display device configured as described above, for example, at the time of manufacturing the plasma display device, the temperature characteristic of the PDP 2 is measured, and the determination criterion for determining the presence or absence of the luminance gradient is set to P based on the result.
It is stored in the DP characteristic storage unit 13. When the plasma display device is used, the determination unit 6 determines the presence or absence of a luminance gradient using the determination criterion read out from the PDP characteristic storage unit 13, and thereby the manufacturing variation of the PDP 2 for each panel and the variation of each panel part. Since the determination can be corrected according to the variation in the characteristics, the luminance control can be performed more appropriately.

Hereinafter, an example of a method of measuring the temperature characteristics of the PDP 2 at the time of manufacturing the plasma display device will be described. In measurement, a signal including a test pattern is used as a test signal. As a test pattern,
For example, a figure with a certain size such as a square,
The luminance value of the graphic portion is set to the maximum value, and the luminance value of the other background portion is set to 0. By changing the display position and area of such a test pattern and performing measurement, P
It is possible to measure the difference in characteristics depending on the display part of DP2. FIG. 13 is a diagram for explaining the display positions of the test patterns, and L1 to L12 represent the display positions of the test patterns. Here, each display position corresponds to an area in the area division unit 4, and L1 to L1
When the test pattern is displayed at position 12, the display of the pattern can be detected based on the histogram distribution of the corresponding area.

A specific measurement procedure will be described. First, a video signal that causes the PDP 2 to display all black is input from the drive circuit 1, and the temperature distribution on the PDP 2 is actually measured using a thermocouple or the like to confirm that there is no temperature difference in the PDP 2. I do. Thereafter, a video signal for displaying a test pattern having a reference area A0 at the display position L1 is input from the drive circuit 1, and is displayed on the PDP 2 for a unit time. By actually measuring the temperature distribution on the PDP 2 using a thermocouple or the like, an in-plane maximum temperature difference T1 is obtained.

Next, a video signal which causes the PDP 2 to display all black again is input from the drive circuit 1 and after a sufficient time is left until the temperature difference in the PDP 2 disappears, an area A0 is provided at the position L2. A video signal for displaying a test pattern is input from the drive circuit 1 and displayed on the PDP 2 for a unit time. By actually measuring the temperature distribution on the PDP 2 using a thermocouple or the like, the in-plane maximum temperature difference T2 at the display position L2 is obtained. Similarly, measurement is performed with the display positions of the test patterns as L3, L4,..., L12, and the maximum in-plane temperature differences T3, T4,.
Obtain T12.

The determination criteria are determined as follows. The temperature difference T1 measured as described above is compared with a predetermined reference value T0. When T1 = T0, the determination criterion in the region corresponding to L1 is determined so that it is determined that there is a luminance gradient when a pattern having an area of A0 or more is displayed, and the determination criterion is determined according to the difference between T1 and T0. Change. That is, when T1> T0, the criterion is made strict so that a pattern having an area smaller than A0 is determined to have a luminance gradient. On the other hand, when T1 <T0, on the contrary, the criterion is loosened so that a pattern having an area slightly larger than A0 is determined to have no luminance gradient. Similarly, T2, T3, ...
By comparing T12 with T0, L2, L3,.
... The criterion for the region corresponding to L12 is determined, and the criterion for each region is stored in the PDP characteristic storage unit 13. By the above-described method, the criterion corresponding to each area can be stored in the PDP characteristic storage unit 13.

Next, the operation when the plasma display device is used will be described. When the determination unit 6 determines whether or not there is a luminance gradient, a determination criterion corresponding to the area of the histogram to be determined is read from the PDP characteristic storage unit 13 and the determination is performed based on this. When making a determination on a histogram obtained by combining histograms of adjacent regions,
The determination is performed based on both of the determination criteria corresponding to the two regions, and if any one of them is determined to have the luminance gradient, the luminance gradient is determined to be present. Also, in the histogram obtained by combining all the histograms for one frame, when it is determined that there is a luminance gradient based on any one of the determination criteria, the luminance gradient is determined to be present. Other operations are described in Embodiment 1.
Is the same as

In the plasma display device configured as described above, even when the temperature characteristics of the PDP vary from panel to panel, or when the temperature characteristics vary from part to part in the panel, the measurement is performed in advance. The presence / absence of a luminance gradient is determined based on the determination criterion corresponding to the temperature characteristic described above, and temperature control is performed based on the determination, so that a temperature difference in the plasma display panel can be prevented.

Embodiment 6 FIG. Next, a sixth embodiment of the present invention will be described. When the plasma display device is used as a display for a computer, for example, a window is often continuously displayed at the same position, but when used as a display for a television, the entire image often changes greatly with time. As described above, since there is a difference in the tendency of the video signal depending on the use of the display, in the present embodiment, the control method is changed so as to perform luminance control suitable for each. FIG. 14 is a configuration diagram of a plasma display device according to a sixth embodiment of the present invention. In FIG. 14, 1 to 7 are the same as those in the first embodiment. It is a control coefficient storage unit that gives a control coefficient to the control unit 7 based on an identification signal for distinguishing between a control signal and a computer signal.

FIG. 15 is a diagram showing a configuration of the control coefficient storage unit 14 according to the sixth embodiment.
Reference numeral 2 denotes a TV signal control coefficient storage unit in which a control coefficient when the input signal is a television signal is stored in advance, and 23 denotes a PC signal control coefficient storage in which a control coefficient when the input signal is a computer signal is stored in advance. Reference numeral 24 denotes a switch for switching the output of the TV signal control coefficient storage unit 22 and the PC signal control coefficient storage unit 23 based on the identification signal and providing the output to the control unit 7.

In the sixth embodiment configured as described above, the switch 24 is switched depending on whether the input signal is a television signal or a computer signal, and when the input signal is a TV signal. Is given to the control unit 7 by the control coefficient from the TV signal control coefficient storage unit 22. If the input signal is a PC signal, the control unit 7
The control coefficient is provided from the control coefficient storage unit 23 at the time of the C signal. That is, it is possible to change the speed and magnitude of the control operation of the control unit 7 by changing the control coefficient according to the input signal.

As a specific control coefficient, for example, there is WMAX shown in FIGS. Hereinafter, WMA
A case where X is a control coefficient will be described. in this case,
WMAX_TV is stored in the TV signal time control coefficient unit 22,
WMAX_PC is stored in the PC signal control coefficient section 23. As a result, any value of WMAX_TV or WMAX_PC is used as WMAX in the control unit 7 according to the input signal.

In the control section 7, when the value of WMAX is large, the number of frames from when the luminance gradient is detected to when the luminance control is actually performed increases, so that the luminance changes slowly. Conversely, when WMAX is small, the number of frames from when the luminance gradient is detected to when the luminance control is performed decreases, and the luminance changes quickly.

On the other hand, when the input signal is a television signal, darkening the image by the brightness control leads to a decrease in image quality. Therefore, it is desirable to perform control gently. Since it is considered that the temperature difference is more likely to occur, it is necessary to shorten the time from when the luminance gradient is detected to when the luminance control is performed. In order to fulfill such a demand, W
MAX_TV may be set to a larger value than WMAX_PC.

As described above, WMAX_TV and WMA
By storing X_PC in the TV signal control coefficient section 22 and the PC signal control coefficient section 23, respectively, the speed at which control is performed changes depending on the type of input signal, and assuming input of both a TV signal and a computer signal. In addition, it is possible to effectively prevent the temperature difference in the plasma display panel while minimizing the deterioration of the image quality of the television signal.

In the above example, WMA is used as the control coefficient.
Although X was used, the width of the actual luminance change when the control value was changed by one step was used as the control coefficient,
A similar effect can be obtained by reducing the luminance change per one-step control in the case of a signal and increasing it in the case of a PC signal.

Embodiment 7 FIG. Next, a seventh embodiment of the present invention will be described. When the ambient temperature in the plasma display device becomes high due to the continuous use of the plasma display device or the influence of the room temperature, the temperature change of the PDP may be greatly affected. In the eighth embodiment, the temperature difference in the plasma display panel is more effectively detected by detecting the ambient temperature in the plasma display device by a temperature detecting means such as a thermocouple and correcting the control method of the control unit based on the detection result. It is configured to prevent the above. FIG. 16 is a configuration diagram of a plasma display device according to a seventh embodiment of the present invention. In the drawing, 1 to 7 are the same as those in the first embodiment.
Reference numeral 15 denotes a temperature detector such as a thermocouple, which detects an ambient temperature of the plasma display device and gives a detection result to the control unit 7.

In the plasma display device configured as described above, the control method is corrected based on the ambient temperature detected by the temperature detector 15. That is, when the ambient temperature is high, the time from when the luminance gradient is detected to when the luminance control is performed is shortened, or correction is performed so as to increase the width of the luminance control in one step, so that the luminance is quickly increased. Control is performed so that it goes down. Conversely, when the ambient temperature is low, by performing correction so that control is performed slowly, unnecessary deterioration of image quality can be suppressed. By performing the control as described above, the temperature difference in the display panel can be more effectively prevented. Since at least one temperature detector 15 for measuring the ambient temperature is sufficient, the increase in manufacturing cost is small.

[0086]

Since the present invention is configured as described above, it has the following effects.

By creating a histogram of the video signal, it is determined whether or not there is a large luminance gradient in the video signal, and the luminance is controlled, so that the PDP can be used without using a temperature detecting means such as a thermocouple. Temperature difference can be prevented, which is effective in reducing the cost of the plasma display device, preventing deterioration in display quality, and extending the life.

Further, since the brightness of the PDP is controlled by controlling the number of sustain pulses when controlling the brightness of the PDP, the temperature difference in the PDP can be reduced by a simple circuit configuration. This is effective in reducing the cost, preventing deterioration in display quality, and extending the life.

Also, since the brightness of the PDP is controlled by controlling the amplitude of the video signal, the temperature difference in the PDP can be obtained by adding only a few circuits to the conventional plasma display device having video signal processing means. Therefore, it is effective in reducing the cost of the plasma display device, preventing deterioration of display quality, and extending the life of the plasma display device.

Further, by maintaining the control information of the control means in the storage means for a certain period of time even after the main power supply is turned off, even if the main power supply is connected again after a relatively short time, appropriate control is performed within the PDP. Can reduce the temperature difference of the plasma display device, which is effective in reducing the cost of the plasma display device, preventing deterioration of display quality, and extending the life.

Further, by outputting the determination result of the determination means to the outside by the communication means, the video signal is controlled by the external signal source side, so that a special control circuit is not required on the plasma display apparatus side, and the PDP is not required. Can reduce the temperature difference of the plasma display device, which is effective in reducing the cost of the plasma display device, preventing deterioration of display quality, and extending the life.

Further, the characteristics of the plasma display panel measured in advance are stored in the panel characteristics storage means, and the judgment reference value of the judgment means is made variable in accordance with the contents of the panel characteristics storage means. Even when there is a variation in the characteristics or when there is a variation in the temperature characteristics between parts in the panel, the temperature difference in the PDP can be appropriately reduced according to the respective temperature characteristics. It is effective for cost reduction, prevention of deterioration of display quality, and long life.

Further, by changing the control coefficient given to the control means from the coefficient storage means depending on whether the video signal input from the outside is a television signal or a computer signal, the display quality is improved by the display according to the type of the signal. Since the temperature difference in the PDP can be reduced by minimizing the influence, it is effective in reducing the cost of the plasma display device, preventing deterioration in display quality, and extending the life.

Further, by correcting the control coefficient of the control means in accordance with the output of the temperature detecting means for detecting the ambient temperature of the plasma display device, the PDP in the PDP can be effectively adjusted according to the environment in which the device is installed and the use conditions. Since the temperature difference can be reduced, it is effective in reducing the cost of the plasma display device, preventing deterioration of display quality, and extending the life.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a plasma display device according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram illustrating an operation of an average value calculating unit according to Embodiment 1 of the present invention.

FIG. 3 is an explanatory diagram illustrating an operation of a region dividing unit according to the first embodiment of the present invention.

FIG. 4 is a diagram showing an example of a histogram calculation in the case where there is no luminance gradient according to the first embodiment of the present invention.

FIG. 5 is a diagram showing an example of histogram calculation in the case where there is a luminance gradient according to the first embodiment of the present invention.

FIG. 6 is a flowchart showing an operation of the control unit according to the first embodiment of the present invention.

FIG. 7 is a diagram illustrating an example of an operation of the control unit according to the first embodiment of the present invention.

FIG. 8 is a configuration diagram of a plasma display device according to a second embodiment of the present invention.

FIG. 9 is a configuration diagram of a plasma display device according to a third embodiment of the present invention.

FIG. 10 is a diagram showing an example of a backup circuit according to a third embodiment of the present invention.

FIG. 11 is a configuration diagram of a plasma display device according to a fourth embodiment of the present invention.

FIG. 12 is a configuration diagram of a plasma display device according to a fifth embodiment of the present invention.

FIG. 13 is a diagram showing a display position of a test signal according to the fifth embodiment of the present invention.

FIG. 14 is a configuration diagram of a plasma display device according to a sixth embodiment of the present invention.

FIG. 15 is a diagram showing a configuration of a control coefficient storage unit according to Embodiment 6 of the present invention.

FIG. 16 is a configuration diagram of a plasma display device according to a seventh embodiment of the present invention.

FIG. 17 is a configuration diagram showing a conventional plasma display device.

FIG. 18 is a timing chart showing the operation of the conventional plasma display device.

[Explanation of symbols]

1 drive circuit, 2 plasma display panel, 3
Average value calculation section, 4 area division section, 5 histogram calculation section, 6 determination section, 7 control section, 8 video signal processing circuit,
9 storage device, 10 backup circuit, 11 communication unit, 13 PDP characteristic storage unit, 14 control coefficient storage unit,
15 Temperature detector.

Claims (11)

[Claims] 1. A driving unit for driving a plasma display panel based on a video signal input from the outside, a plasma display panel driven by the driving unit for displaying, and a unit for removing a low frequency component of the video signal. A histogram calculating unit that creates a histogram for each gradation range of a video signal from which a low-frequency component has been removed; a determining unit that determines a video having a large luminance change from the histogram created by the histogram calculating unit; Control means for controlling the driving means based on a result of the determination. 2. The plasma display device according to claim 1, wherein the number of sustain pulses in said driving means is controlled by said control means. 3. A video signal processing means for processing a video signal input from the outside, a driving means for driving a plasma display panel based on the video signal processed by the video signal processing means, and a driving means for driving the plasma display panel. A plasma display panel for performing display, a unit for removing a low frequency component of the video signal processed by the video signal processing unit, and a histogram calculation unit for creating a histogram for each gradation range of the video signal from which the low frequency component has been removed And determining means for determining an image with a sharp change in luminance from the histogram created by the histogram calculating means; and control means for controlling the video signal processing means based on the determination result of the determining means. Plasma display device. 4. The plasma display apparatus according to claim 1, further comprising a storage unit for holding control level information of said control unit for a certain period after a main power supply is cut off. . 5. A driving unit for driving a plasma display panel based on a video signal input from the outside, a plasma display panel driven by the driving unit for displaying, and a unit for removing a low-frequency component of the video signal. A histogram calculating unit that creates a histogram for each gradation range of a video signal from which a low-frequency component has been removed; a determining unit that determines a video having a large luminance change from the histogram created by the histogram calculating unit; A plasma display device comprising: a communication unit that outputs a determination result to the outside. 6. A panel characteristic storing means for storing characteristics of a plasma display panel measured in advance, and a criterion value of said determining means is made variable in accordance with the contents of said panel characteristic storing means. The plasma display device according to claim 1. 7. The apparatus according to claim 1, further comprising a coefficient storage means for giving a different control coefficient to said control means depending on whether the input video signal is a television signal or a computer signal. Or a plasma display device. 8. The plasma display apparatus according to claim 1, further comprising a temperature detecting means for detecting an ambient temperature of the plasma display device, wherein the reference value of said determining means is corrected in accordance with an output of said temperature detecting means. Item 8. The plasma display device according to any one of items 7. 9. A process for removing a low-frequency component of a video signal, a histogram calculation process for creating a histogram for each gradation range of the video signal from which the low-frequency component has been removed, and a histogram created in the histogram calculation process. A temperature control method for a plasma display panel, comprising: a determination step of determining an image having a sharp change in luminance; and a control step of controlling the luminance of the plasma display panel based on a determination result of the determination step. 10. The method according to claim 9, wherein the number of sustain pulses of the plasma display panel is controlled by the control step. 11. The method according to claim 9, wherein the amplitude of a video signal input to the plasma display panel is controlled by the control step.