JP2008292868A - Temperature variation suppression device, self-luminous display device, electronic equipment and temperature variation suppression method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To execute suppression control of peak brightness with consideration for panel temperature. <P>SOLUTION: The frequency distribution of pixel data for each frame unit and the temperature of a self-luminous display panel are detected. When the detected temperature is a reference temperature or lower, the position of a boundary gradation value where the frequency distribution area on the maximum gradation value side exceeds a reference value is determined based on the frequency distribution, and luminance levels of all gradations values of the boundary gradation value or more are limited to a luminance level corresponding to the boundary gradation value. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The invention described in this specification relates to a technique for suppressing temperature unevenness on the surface of a self-luminous display panel. The invention has aspects as a temperature unevenness suppressing device, a self-luminous display device, an electronic device, and a temperature unevenness suppressing method.

  Light emitting elements constituting organic EL display panels and other self-luminous display panels have temperature-dependent characteristics. For example, in the case of an organic EL display panel, the IV characteristic, which is an important parameter at the time of light emission, varies according to a temperature change. The cause of the temperature change includes a change in environment temperature and a temperature change caused by heat generation of the light emitting element itself.

  Among these, a change in environmental temperature acts on the entire panel surface, whereas a temperature change accompanying heat generation of the light emitting element itself acts only on a specific pixel or a specific region. For this reason, the panel temperature distribution variation has a characteristic that depends on the display image.

In addition, if the state where the distribution variation of the panel temperature is large continues for the specific region, it also acts in the direction of promoting the expansion of the deterioration amount difference of the light emitting element.
As a result, an increase in unevenness in temperature unevenness causes luminance unevenness. Hereinafter, examples of existing techniques mainly for the purpose of suppressing the burn-in phenomenon will be exemplified.

JP 2003-134418 A JP 2002-351389 A JP 2006-030318 A

  However, in the conventional image sticking suppression technology, the occurrence of variation in the panel temperature distribution is not generally considered. For this reason, the effect of suppressing temperature unevenness is insufficient.

  Accordingly, the inventors of the present invention have (a) a frequency distribution detection unit that detects a frequency distribution of pixel data in units of one frame, and (b) a self-luminous display panel as a temperature unevenness correction device on the surface of the self-luminous display panel. A panel temperature detection unit for detecting temperature; and (c) when the detected temperature is equal to or lower than the reference temperature, the position of the boundary gradation value where the frequency distribution area on the maximum gradation value side exceeds the reference value is obtained based on the frequency distribution. And a luminance level control unit that restricts the luminance level of all gradation values equal to or higher than the boundary gradation value to be equal to or lower than the luminance level corresponding to the boundary gradation value.

  In the case of the invention proposed by the inventors, the brightness level of all gradation values equal to or higher than the boundary gradation value is limited to the boundary gradation value only when a panel temperature with a large temperature unevenness is detected (temperature detection below the reference temperature). It is limited to the luminance level corresponding to.

  At this time, the luminance level of the pixel corresponding to the gradation value smaller than the boundary gradation value is less influenced by whether it is the input gradation value. As a result, the luminance level can be lowered only for a certain ratio of pixels having a large heat generation effect. Thereby, temperature unevenness can be suppressed while minimizing the influence on the image quality.

Hereinafter, the case where the invention is applied to an active matrix driving type organic EL panel module will be described.
In addition, the well-known or well-known technique of the said technical field is applied to the part which is not illustrated or described in particular in this specification.
Moreover, the form example demonstrated below is one form example of invention, Comprising: It is not limited to these.

(A) Form example 1
(A-1) Overall Configuration FIG. 1 shows the main components of the organic EL panel module 1. The organic EL panel module 1 includes an organic EL panel 3, a data line driver 5, a scanning line driver 7, and a temperature unevenness suppressing unit 9 as main components.

  In the effective display area of the organic EL panel 3, pixels 11 are arranged in a matrix according to the panel resolution. In the case of this embodiment, the organic EL panel 3 is for color display, and the pixels 11 are arranged according to the arrangement of emission colors. However, when an organic EL element having a structure in which organic light emitting layers of a plurality of colors are stacked constitutes the pixel 11, one pixel corresponds to a plurality of light emission colors.

  FIG. 2 shows a connection relationship between the internal structure of the pixel 11 corresponding to the active matrix driving method and other driving circuits. However, the actual pixel 11 is provided with a transistor for controlling the light emission period, a transistor corresponding to a threshold correction function and a mobility correction function of the drive transistor, and the like.

The pixel 11 includes a write control transistor T1, a charge holding capacitor C, a current driving transistor T2, and an organic EL element D.
The write control transistor T1 is a thin film transistor that controls writing of the signal voltage Vdata corresponding to the pixel data to the charge retention capacitor C.

  The opening / closing operation of the write control transistor T1 is controlled by a write signal WS supplied from the scan line driver 7 through the scan line WL. Pixel data (signal voltage Vdata) applied through the data line DL is written into the charge storage capacitor C during the period in which the write control transistor T1 is closed.

  The current driving transistor T2 is a thin film transistor that supplies a driving current having a magnitude corresponding to the signal voltage Vdata written in the charge holding capacitor C to the organic EL element D. In the case of FIG. 2, an N-channel field effect transistor is used as the current driving transistor T2.

  The data line driver 5 is a circuit device that applies a signal voltage Vdata corresponding to pixel data to the data line DL. The data line driver 5 has a configuration in which one digital / analog conversion circuit is arranged for one data line DL.

  Note that the digital / analog conversion circuit here uses a circuit with a gamma correction function to which a reference voltage defining an intermediate gradation is given from the outside in addition to a reference voltage defining a black level and a white level. In the case of this embodiment, the two reference voltages on the white level side are switched and controlled according to the detected panel temperature.

  The scanning line driver 7 is a circuit device that gives the write timing of the signal voltage Vdata. The scanning lines WL to which the write timing is supplied are sequentially switched and controlled in units of horizontal scanning periods.

  When the panel temperature is equal to or lower than the reference temperature, the temperature unevenness suppressing unit 9 obtains, for each frame, a boundary gradation value in which the frequency distribution area on the maximum gradation value side exceeds the reference value, and the luminance level corresponding to the boundary gradation value Is a processing device that controls the maximum luminance level in the corresponding frame.

  In the case of this embodiment, the temperature unevenness suppressing unit 9 is only the reference voltage Vref_0 that defines the white level (maximum gradation value) among the plurality of reference voltages supplied to the digital / analog converters constituting the data line driver 5. Is variably controlled to a reference voltage Vref_H corresponding to the boundary gradation value. FIG. 3 shows an application example of the reference voltage supplied to the data line driver 5.

  FIG. 3A shows an application example of a reference voltage when temperature unevenness suppression control is not executed (during off operation). FIG. 3B is an application example of the reference voltage when the temperature unevenness suppression control is executed (during the ON operation). As shown in FIG. 3, an initial set value of the reference voltage Vref_0 corresponding to the maximum gradation value of the pixel data is supplied during the off control, and a reference voltage variably set corresponding to the boundary gradation value during the on control. Vref_H is supplied.

FIG. 4 shows an internal configuration example of the temperature unevenness suppressing unit 9. The temperature unevenness suppression unit 9 includes a frequency distribution detection unit 21, a panel temperature detection unit 23, and a luminance level control unit 25.
Here, the frequency distribution detection unit 21 detects a frequency distribution for each gradation value from 0 level to the maximum level (for example, 255 when the data length is 8 bits) of pixel data input in one frame period. It is.

  The panel temperature detection unit 23 is a temperature sensor that detects the surface temperature of the organic EL panel 3. In the case of this embodiment, a known temperature sensor is used for the panel temperature detection unit 23. Further, the panel temperature detection unit 23 is disposed outside the effective display area. In order to reduce the detection error of the panel temperature, it is desirable to arrange the temperature sensor as close as possible to the effective display area.

  The luminance level control unit 25 is a processing device that switches between performing execution of variable control of the luminance level according to the detected temperature Dtmp and stopping execution (with the initial setting). FIG. 5 shows an internal configuration example of the luminance level control unit 25. The luminance level control unit 25 includes a boundary gradation value detection unit 31 and a reference voltage generation unit 33.

  The boundary gradation value detection unit 31 is a processing device that detects the position of the boundary gradation value where the frequency distribution area on the maximum gradation value side exceeds the reference value based on the frequency distribution when the detected temperature is equal to or lower than the reference temperature. . If the detected temperature is equal to or higher than the reference temperature, the boundary tone value detection unit 31 does not perform the boundary tone value detection process. This is because there is no need for control based on the boundary gradation value.

  However, the boundary gradation value detection unit 31 outputs the maximum gradation value (255 when the data length is 8 bits) that can be taken by the pixel data for generation of the reference voltage Vref_0 as the boundary gradation value. Here, it should be noted that it is not the maximum value of the pixel data constituting the frame image.

  FIG. 6 shows an approximate relationship existing between the panel temperature and the temperature unevenness. That is, in FIG. 6, the approximate relationship is shown by three levels of the panel temperature: “high”, “normal (normal temperature)”, and “low”. Although the three temperature sections are relative expressions, the following description will be made with these three temperature sections in order to focus on the general relationship.

  When the panel temperature is “high”, it means that the temperature of the entire panel is originally high. Therefore, even if the high luminance portion and the low luminance portion are mixed in the organic EL panel, the temperature difference between the portions is not noticeable. On the other hand, when the panel temperature is “normal” or “low”, the high-luminance portion and the low-luminance portion tend to have a temperature difference as they are.

  In the case of this embodiment, the boundary tone value detection unit 31 uses 40 ° C. as the reference temperature. Therefore, when the detected panel temperature is 40 ° C. or higher, the boundary gradation value detection unit 31 sets the maximum level that the pixel data can take (for example, 255 when the data length is 8 bits) as the boundary gradation value. .

  On the other hand, when the detected panel temperature is lower than 40 ° C., the boundary gradation value detection unit 31 detects the position of the boundary gradation value where the frequency distribution area on the maximum gradation value side exceeds the reference value from the frequency distribution. To do. That is, the frequency distribution value of each pixel is cumulatively added from the maximum gradation value side, and the gradation value whose accumulated addition value first exceeds the reference value is detected.

In the case of this embodiment, the boundary tone value detection unit 31 uses a value corresponding to 15% of the total number of pixels as a reference value.
Here, as the reference value is increased, the effect of reducing temperature unevenness after luminance control can be enhanced. On the other hand, the smaller the reference value, the smaller the effect of reducing temperature unevenness after luminance control. Therefore, it is desirable to set the reference value appropriately according to the characteristics of the organic EL panel 3 and the control result.

  Based on the frequency distribution example shown in FIG. 7, the relationship between the frequency distribution and the boundary gradation value is shown. The boundary tone value detection unit 31 sequentially reads the frequency distribution corresponding to each tone value from the maximum tone value side, and the cumulative addition value thereof exceeds the reference value (value corresponding to 15%) each time it is read. It is determined whether or not. While the cumulative addition value does not exceed the reference value, the frequency distribution corresponding to the next gradation value is read and added to the previous cumulative addition value, and the comparison processing between the cumulative addition value and the reference value is executed.

Here, the boundary gradation value detection unit 31 sets the gradation value at which the cumulative addition value first exceeds the reference value as the boundary gradation value.
As described above, the boundary gradation value detection unit 31 switches the control contents depending on whether or not the panel temperature is higher than the reference temperature.

  The reference voltage generation unit 33 defines the maximum voltage level (white level) output from the digital / analog conversion circuit constituting the data line driver 5 based on the boundary gradation value detected by the boundary gradation value detection unit 31. The reference voltage Vref_H (including Vref_0 as an initial value) is generated. For the reference voltage generation unit 33, for example, a digital / analog conversion circuit or a digital potentiometer is used.

(A-2) Control operation and effect Hereinafter, the content of the processing operation performed in the temperature nonuniformity suppression part 9 is demonstrated. FIG. 8 shows an on / off relationship between panel temperature and luminance control.

  The temperature unevenness suppression 9 constantly monitors the panel temperature, and determines whether the detected value of the panel temperature exceeds 40 ° C. for each frame. However, this determination may be performed for each set number of frames, in units of seconds and minutes. This is because the panel temperature generally changes slowly.

  When the detected value of the panel temperature is less than 40 ° C., the temperature unevenness suppressing unit 9 executes brightness control. That is, the temperature unevenness suppression unit 9 obtains a frequency distribution for each gradation value of the pixel data constituting each frame image, and the gradation distribution area on the maximum gradation value side first exceeds the reference value (15%). Find the value.

  FIG. 9 shows a processing image. FIG. 9A shows an example of the frequency distribution of a certain frame image. In this example, the gradation value whose frequency distribution area on the maximum gradation value side first exceeds the reference value (15%) is 70% of the maximum gradation value.

  FIG. 9B shows the luminance distribution that appears on the screen for each gradation value when the reference voltage Vref_H is controlled so that the detected gradation value (70% of the maximum gradation value) becomes the maximum gradation value. FIG. From FIG. 9B, it can be seen that at least 15% of all the pixels constituting one frame have a gradation value lower than that at the time of input.

As a result, the luminance difference between the maximum luminance and the minimum luminance in one frame can be reduced, and the power consumed on the organic EL panel 3 can be reduced accordingly.
Of course, when the power consumption is suppressed as compared with that at the time of input, the amount of heat generated in the organic EL panel 3 is also reduced, and generation and expansion of temperature unevenness can be suppressed accordingly.

  In particular, when the area of the organic EL panel 3 is large, temperature unevenness is likely to occur. However, the method described in the embodiment can be implemented in the organic EL panel 3 because the effect of suppressing temperature unevenness can be realized only by a simple processing operation. It is particularly advantageous.

  The temperature unevenness suppressing unit 9 does not require a large-scale storage area such as a frame memory, and can be easily mounted on a part of an existing circuit device such as a timing generator. In fact, if it can be mounted on an existing circuit device, the design change of the panel surface can be minimized. Therefore, the temperature unevenness suppressing unit 9 has a high effect in terms of manufacturing and cost.

(B) Embodiment 2
In this embodiment, a case will be described in which the above-described temperature unevenness suppressing operation is realized only by digital signal processing.

  FIG. 10 shows main components of the organic EL panel module 41. In FIG. 10, the same reference numerals are assigned to the corresponding parts to those in FIG. The organic EL panel module 41 includes the organic EL panel 3, the data line driver 43, the scanning line driver 7, and the temperature unevenness suppressing unit 45 as main components. Below, the structural example of the data line driver 43 and the temperature nonuniformity suppression part 45 which are the structure peculiar to this form example is shown.

  In this embodiment, the data line driver 43 can be a digital / analog conversion circuit that does not have a gamma correction function. That is, it is possible to use a digital / analog conversion circuit that operates only by applying a reference voltage that defines a black level and a reference voltage that defines a white level. However, as in Embodiment 1, it is also possible to use a digital / analog conversion circuit with a gamma correction function.

The temperature unevenness suppressing unit 45 is a processing device that realizes the luminance level control processing described in the first embodiment by gradation conversion.
FIG. 11 shows an internal configuration example of the temperature unevenness suppressing unit 45. In FIG. 11, parts corresponding to those in FIG. The temperature unevenness suppression unit 45 includes a frequency distribution detection unit 21, a panel temperature detection unit 23, a boundary gradation value detection unit 51, and a gradation conversion unit 53.

  As shown in FIG. 11, the circuit configuration until the boundary gradation value is detected is the same as that in the first embodiment. The boundary gradation value detection unit 51 corresponds to the boundary gradation value detection unit 31 (FIG. 5) constituting the luminance level control unit 25 of FIG.

  The gradation conversion unit 53 is a processing device that performs gradation conversion on the input value Din of the pixel data so that the detected boundary gradation value becomes the maximum output value. FIG. 12 shows the input / output relationship corresponding to the gradation conversion operation of this embodiment.

  As shown in FIG. 12, when the input value Din of the pixel data is equal to or less than the boundary gradation value, the same value as the input value Din is output as the output value DO of the pixel data. On the other hand, when the input value Din of the pixel data is larger than the boundary gradation value, the boundary gradation value is output as the output value DO of the pixel data.

That is, only pixels having a gradation value larger than the boundary gradation value (only 15% of all pixels) are converted into boundary gradation values.
This gradation conversion process can be easily realized only by the comparison process between the input value Din of the pixel data and the boundary gradation value.

Of course, also in this case, the gradation conversion process is executed only when the detected temperature Dtmp is lower than the reference temperature of 40 ° C., and when the detected temperature Dtmp is higher than the reference temperature of 40 ° C., all pixel data (input The value Din) is output as it is as the output value DO.
As a result, the luminance change on the screen is the same as that in the first embodiment.

(C) Other Embodiments (C-1) Temperature Detection Method In the embodiment described above, the case where the panel temperature is detected using the temperature sensor has been described. However, it is possible to detect a change in the anode potential (strictly speaking, the voltage between the anode and the cathode of the organic EL element D) when the pixel 11 in the effective display area or the dummy pixel having the same structure as the pixel is driven with a constant current. Thus, the current panel temperature may be detected.

In this case, the temperature of the effective display region or the temperature in the vicinity thereof can be directly measured, and the switching accuracy between execution and non-execution of temperature unevenness suppression control can be improved.
In addition, since the constant current for measurement is a fixed value determined regardless of the image content, when measuring the temperature using the pixels 11 in the effective display area, it is desirable to devise the arrangement location.

  For example, it is desirable to arrange in the peripheral part of the screen. Further, as described above, temperature unevenness is likely to occur in the screen according to the display contents. Therefore, when detecting the panel temperature that represents the entire panel, use the detection result of the pixel that shines with the screen average value as much as possible (for example, use the detection result of the pixel that is controlled to emit light with the screen average value except during measurement). It is desirable to use the average value of the detection results at a plurality of locations distributed in the screen.

(C-2) Setting Example of Frequency Distribution Area In the case of the above-described embodiment, the case where only one frequency distribution area for determining the boundary gradation value is prepared has been described.
However, a plurality of frequency distribution areas may be selectively used according to the panel temperature.

  FIG. 13 shows a correspondence example between the panel temperature and the frequency distribution area. As described with reference to FIG. 6, the temperature unevenness tends to increase as the panel temperature decreases. Accordingly, when the detected panel temperature is normal (normal temperature), the frequency distribution area is set to 15%, and when the detected panel temperature is low, the frequency distribution area is set to 30%. The frequency distribution area may be switched according to the temperature.

  In addition, 10 degreeC is used for the reference temperature used for judging low temperature and normal, for example. Of course, since the boundary gradation value detected at the reference temperature changes greatly, it is desirable to use the optimum reference temperature in consideration of actual image quality change and panel characteristics.

(C-3) Reference Voltage Control Example In the case of the above-described embodiment, the case where only the reference voltage Vref_0 that defines the white level of the signal voltage output from the data line driver 5 is variably controlled has been described.
However, depending on the relationship between the intermediate reference voltage prepared for gamma correction and the boundary gradation value, one or more intermediate reference voltages Vref_1, Vref_2, etc. other than the reference voltage Vref_0 that defines the white level are also used for the boundary gradation value. It may be switched to the reference voltage Vref_H corresponding to.

(C-4) Product example (a) Drive IC
In the above description, the organic EL panel module in which the pixel array unit (organic EL panel) and the drive circuit (data line driver, scanning line driver, temperature unevenness suppressing unit, etc.) are formed on one substrate has been described.

  However, the pixel array section and the drive circuit section can be manufactured separately and distributed as independent products. For example, the drive circuits may be manufactured as independent drive ICs (integrated circuits) and distributed independently from the pixel array unit.

(B) Display module The organic EL panel modules 1 and 41 according to each of the above-described embodiments can be distributed in the form of a panel module 61 having the appearance configuration shown in FIG.
The panel module 61 has a structure in which a facing portion 63 is bonded to the surface of the support substrate 65.

The facing portion 63 is made of glass or other transparent member as a base material, and a color filter, a protective film, a light shielding film, and the like are arranged on the surface thereof.
The panel module 61 may be provided with an FPC (flexible printed circuit) 67 for inputting / outputting signals and the like to / from the support substrate 65 from the outside.

(C) Electronic device The organic EL panel modules 1 and 41 in the embodiment described above are also distributed in a product form mounted on an electronic device.
FIG. 15 shows a conceptual configuration example of the electronic device 71. The electronic device 71 includes the organic EL panel module 73 and the system control unit 75 described above.

The processing content executed by the system control unit 75 varies depending on the product form of the electronic device 71.
In addition, an operation input unit (not shown) is connected to the system control unit 75, and the system control unit 75 executes a process according to a user operation result.

Note that the electronic device 71 is not limited to a device in a specific field as long as it has a function of displaying an image or video generated in the device or input from the outside.
As this type of electronic device 71, for example, a television receiver is assumed. FIG. 16 shows an appearance example of the television receiver 81.

  A display screen 87 including a front panel 83, a filter glass 85, and the like is disposed on the front of the housing of the television receiver 81. The portion of the display screen 87 corresponds to the organic EL panel module 1 (41) described in the embodiment.

  Further, for example, a digital camera is assumed as this type of electronic device 71. FIG. 17 shows an appearance example of the digital camera 91. FIG. 17A shows an example of the appearance on the front side (subject side), and FIG. 17B shows an example of the appearance on the back side (photographer side).

  The digital camera 91 includes a protective cover 93, an imaging lens unit 95, a display screen 97, a control switch 99, and a shutter button 101. Among these, the part of the display screen 97 corresponds to the organic EL panel module 1 (41) described in the embodiment.

For example, a video camera is assumed as this type of electronic device 71. FIG. 18 shows an example of the appearance of the video camera 111.
The video camera 111 includes an imaging lens 115 that images a subject in front of the main body 113, a shooting start / stop switch 117, and a display screen 119. Among these, the display screen 119 corresponds to the organic EL panel module 1 (41) described in the embodiment.

  In addition, as this type of electronic device 71, for example, a portable terminal device is assumed. FIG. 19 shows an appearance example of a mobile phone 121 as a mobile terminal device. A cellular phone 121 illustrated in FIG. 19 is a foldable type, and FIG. 19A illustrates an appearance example in a state where the housing is opened, and FIG. 19B illustrates an appearance example in a state where the housing is folded.

  The mobile phone 121 includes an upper housing 123, a lower housing 125, a connecting portion (in this example, a hinge portion) 127, a display screen 129, an auxiliary display screen 131, a picture light 133, and an imaging lens 135. Among these, the display screen 129 and the auxiliary display screen 131 correspond to the organic EL panel module 1 (41) described in the embodiment.

Further, for example, a computer is assumed as this type of electronic device 71. FIG. 20 shows an example of the appearance of the notebook computer 141.
The notebook computer 141 includes a lower casing 143, an upper casing 145, a keyboard 147, and a display screen 149. Among these, the part of the display screen 149 corresponds to the organic EL panel module 1 (41) described in the embodiment.

  In addition to these, the electronic device 71 may be an audio playback device, a game machine, an electronic book, an electronic dictionary, or the like.

(C-5) Other Pixel Circuit Examples In the above-described embodiments, the case where the current driving transistor T2 is an N-channel field effect transistor has been described.
However, the present invention can also be applied to the case where the current driving transistor T2 is configured by a P-channel field effect transistor.

FIG. 21 shows an example of a pixel circuit when the current driving transistor T2 is a P-channel field effect transistor. In FIG. 21, the same reference numerals are given to the portions corresponding to FIG. 2.
In the case of this pixel circuit, the charge holding capacitor C is connected to hold the voltage Vdata corresponding to the pixel data between the power supply potential VSS and the gate electrode of the current driving transistor T2.

(C-6) Other Display Device Examples In the description of the embodiment examples, the case where the temperature unevenness suppressing function according to the invention is mounted on the organic EL panel module has been described.
However, the temperature unevenness suppressing function according to the invention can also be applied to other self-luminous display devices.

For example, the present invention can be applied to an inorganic EL display device, a display device in which LEDs are arranged, and other display devices in which light emitting elements having a diode structure are arranged on a screen.
In the case of the embodiment described above, the active matrix driving method is adopted, but the present invention can also be applied to the passive matrix driving method.

(C-7) Other Implementation Method of Control Device In the above description, the case where the temperature unevenness suppressing function is implemented mainly by software processing has been described.
However, a part of the contrast control function may be realized by an application specific IC or other hardware device.

(C-8) Others Various modifications can be considered for the above-described embodiments within the scope of the gist of the invention. Various modifications and applications created or combined based on the description of the present specification are also conceivable.

It is a figure which shows the circuit structure of an organic electroluminescent panel module. It is a figure which shows the connection relation of a pixel circuit and a peripheral circuit. It is a figure which shows the example of application of the reference voltage corresponding at the time of the non-control of temperature nonuniformity, and suppression control, respectively. It is a figure which shows the internal structural example of a temperature nonuniformity suppression part. It is a figure which shows the internal structural example of a luminance level control part. It is a figure explaining the relationship between panel temperature and temperature nonuniformity. It is a figure which shows the frequency distribution example. It is a figure explaining the correspondence of panel temperature and control operation. It is a figure explaining the change of the frequency distribution by luminance control. It is a figure which shows the circuit structure of an organic electroluminescent panel module. It is a figure which shows the internal structural example of a temperature nonuniformity suppression part. It is a figure which shows the input-output relationship of a gradation converter. It is a figure explaining other execution relations of panel temperature and control operation. It is a figure which shows the structural example of a display module. It is a figure which shows the function structural example of an electronic device. It is a figure which shows the example of goods of an electronic device. It is a figure which shows the example of goods of an electronic device. It is a figure which shows the example of goods of an electronic device. It is a figure which shows the example of goods of an electronic device. It is a figure which shows the example of goods of an electronic device. It is a figure which shows the other pixel circuit example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Organic EL panel module 3 Organic EL panel 9 Temperature unevenness suppression part 21 Frequency distribution detection part 23 Panel temperature detection part 25 Luminance level control part 31 Boundary gradation value detection part 33 Reference voltage generation part 41 Organic EL panel module 45 Temperature unevenness suppression Part 51 boundary gradation value detection part 53 gradation conversion part

Claims (6)

A temperature unevenness suppressing device for suppressing temperature unevenness on the surface of a self-luminous display panel,
A frequency distribution detector that detects a frequency distribution of pixel data in units of one frame;
A panel temperature detector for detecting the temperature of the self-luminous display panel;
When the detected temperature is equal to or lower than the reference temperature, the position of the boundary gradation value where the frequency distribution area on the maximum gradation value side exceeds the reference value is obtained based on the frequency distribution, and all gradation values equal to or higher than the boundary gradation value are obtained. And a luminance level control unit for limiting the luminance level to a luminance level corresponding to the boundary gradation value or less. In the temperature nonuniformity suppression apparatus of Claim 1,
The brightness level control unit
One or more reference voltages on the maximum gradation value side to be applied to the data line driver are controlled to voltages corresponding to the detected boundary gradation values. In the temperature nonuniformity suppression apparatus of Claim 1,
The brightness level control unit
Only the pixel data having a gradation value larger than the boundary gradation value is converted into the boundary gradation value. A self-luminous display panel;
A frequency distribution detector that detects a frequency distribution of pixel data in units of one frame;
A panel temperature detector for detecting the temperature of the self-luminous display panel;
When the detected temperature is equal to or lower than the reference temperature, the position of the boundary gradation value where the frequency distribution area on the maximum gradation value side exceeds the reference value is obtained based on the frequency distribution, and all gradation values equal to or higher than the boundary gradation value are obtained. A self-luminous display device, comprising: a luminance level control unit that restricts the luminance level to a luminance level corresponding to the boundary gradation value or less. A self-luminous display panel;
A frequency distribution detector that detects a frequency distribution of pixel data in units of one frame;
A panel temperature detector for detecting the temperature of the self-luminous display panel;
When the detected temperature is equal to or lower than the reference temperature, the position of the boundary gradation value where the frequency distribution area on the maximum gradation value side exceeds the reference value is obtained based on the frequency distribution, and all gradation values equal to or higher than the boundary gradation value are obtained. A luminance level control unit that restricts the luminance level of the luminance level to be equal to or lower than the luminance level corresponding to the boundary gradation value;
A system controller;
An electronic device comprising: an operation input unit for the system control unit. In the temperature unevenness suppressing method for suppressing temperature unevenness on the surface of the self-luminous display panel,
Processing for detecting the frequency distribution of pixel data in units of one frame;
A process for detecting the temperature of the self-luminous display panel;
When the detected temperature is equal to or lower than the reference temperature, the position of the boundary gradation value where the frequency distribution area on the maximum gradation value side exceeds the reference value is obtained based on the frequency distribution, and all gradation values equal to or higher than the boundary gradation value are obtained. And a process of limiting the luminance level to a luminance level corresponding to the boundary gradation value or less.

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