JP2010197904A - Method for controlling luminance of display apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a display apparatus and a luminance control method for compensating the temperature of a display panel at the start of power to surely prevent the display panel from being broken, without using a subsidiary power source or a timer. <P>SOLUTION: The display apparatus is provided with: a detection means 65 which divides a display panel 10 into a plurality of blocks and obtains temperature difference prediction information between blocks by predicting the temperature of each block from a video signal; a nonvolatile memory means 42 storing the temperature difference prediction information; and a luminance control means 60 controlling the luminance to be displayed on the display panel 10 on the basis of the temperature difference prediction information stored in the memory means 42 at the start of power. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a display device and a brightness control method for preventing damage to the display panel by compensating for the temperature of the display panel of the display device when the power is turned on.

  In recent years, thin display devices tend to increase in size and definition and increase in power consumption. The display is also becoming thinner. In the case of a plasma display panel, heat is generated at the time of light emission of the discharge cell, and when this heat is locally applied to the glass surface constituting the plasma display panel, there is a problem that the glass is broken. Thus, due to an increase in power consumption of the display device and a reduction in the thickness of the panel, a countermeasure against a partial temperature rise is required structurally.

  For example, in a plasma display panel, a sheet having a good thermal conductivity is often used between the glass surface and the metal constituting the chassis, and a metal having a good thermal conductivity is also used. It is not a cost-effective method.

In order to solve the above problems, various methods have been proposed for panel temperature compensation in conventional display devices. In many cases, it has been proposed to predict temperature information from a video signal and control the luminance of the video to be displayed. About the panel temperature prediction at the time of power activation, in order to predict the panel temperature at the time of power activation, the time from power off to the next power activation is counted by a timer with a sub power supply or battery, and it has elapsed since the power off. A method for predicting the panel temperature state at the time of activation by time (for example, see Patent Document 1) has been proposed.
JP 11-194745 A

  The method of predicting the panel temperature from the video signal in a state where the power is supplied cannot predict the temperature when the power is not supplied during the power-off period. In addition, in the method of operating the timer circuit with the sub power supply and predicting the panel temperature state from the lapse of time until the next power supply start-up, the timer circuit stops when AC power is removed, and accurate temperature prediction becomes impossible. There is a problem that protection control cannot be performed. In addition, this method requires a power supply circuit, which increases costs, requires power supply even during the power-off period, increases power consumption, and is not suitable for power saving.

  The present invention has been made in view of the above problems, can appropriately predict a temperature change during the power-off period, can more reliably prevent damage to the panel that is the display unit, Another object of the present invention is to provide a display device that can prevent damage to a display unit at low cost and without using a timer circuit.

  The display device of the present invention divides the display panel for displaying a video signal input from the outside, and a plurality of blocks, predicts the temperature of the block from the video signal corresponding to the block, Detection means for obtaining temperature difference prediction information between blocks, non-volatile memory means for storing the temperature difference prediction information, and the display panel based on the temperature difference prediction information stored in the memory means at power-on Brightness control means for controlling the brightness displayed on the screen.

  Further, the display device of the present invention divides the display panel into a plurality of blocks for displaying a video signal input from the outside, predicts the temperature of the block from the video signal corresponding to the block, Detection means for obtaining temperature difference prediction information between the blocks, first temperature detection means for detecting temperature information in the vicinity of the display panel, temperature information detected by the first temperature detection means, and the temperature difference prediction Non-volatile memory means for storing information, and brightness control means for controlling brightness displayed on the display panel based on the temperature difference prediction information and temperature information stored in the memory means at the time of power-on Is.

  Further, the display device of the present invention divides the display panel into a plurality of blocks for displaying a video signal input from the outside, predicts the temperature of the block from the video signal corresponding to the block, Detection means for obtaining temperature difference prediction information between the blocks, first temperature detection means for detecting temperature information in the vicinity of the display panel, second temperature detection means for detecting external ambient temperature, and the first Non-volatile memory means for storing the temperature information detected by the temperature detection means, the external ambient temperature detected by the second temperature detection means, and the temperature difference prediction information, and the memory means stored in the memory means at power-on Brightness control means for controlling brightness displayed on the display panel based on the temperature difference prediction information, the external ambient temperature, and the temperature information.

  A display panel that displays an externally input video signal, a detection means that divides the video signal into a plurality of blocks, predicts the temperature of the display panel in each block and obtains temperature difference prediction information, and stores temperature difference prediction information Non-volatile memory means and brightness control means for controlling the brightness of the display panel according to the predicted temperature value, and the brightness is controlled based on the temperature difference prediction information stored in the memory means when the power is turned on It is characterized by that.

  Thereby, even when the power is turned on, it can be determined that there is a region having a large temperature difference on the display panel, and the temperature difference can be reduced by controlling the luminance.

  In addition, the display device includes temperature detection means for detecting temperature information in the vicinity of the display panel, the temperature information detected by the temperature detection means is stored in the memory means, and is stored in the memory means when the power is turned on. The temperature control is performed by predicting the temperature of the display panel based on the temperature difference prediction information, the temperature information, and the temperature information detected by the temperature detecting means. Thereby, the power-off period can be estimated from the temperature difference at the time of power-off and the temperature difference at the time of power-on, and the panel temperature difference can be accurately predicted.

  In addition, the display device includes temperature detection means for detecting the external ambient temperature, temperature information detected by the temperature detection means is stored in the memory means, and temperature difference prediction information stored in the memory means when the power is turned on. Further, the brightness control is performed by predicting the temperature of the display panel based on the temperature information and the temperature information detected by the temperature detecting means. Thereby, the power-off period can be estimated from the temperature difference at the time of power-off and the temperature difference at the time of power-on, and the panel temperature difference can be accurately predicted.

  In addition, the display device includes first temperature detection means for detecting temperature information in the vicinity of the display panel, and second temperature detection means for detecting the external ambient temperature of the display device. Temperature information detected by the detection means and the second temperature detection means is stored in the memory means, and temperature difference prediction information and temperature information stored in the memory means when the power is turned on, and detected by the first and second temperature detection means The brightness control is performed by predicting the temperature of the display panel based on the temperature information. Thereby, the panel temperature difference at the time of starting the power supply can be accurately predicted from the display panel and the external atmosphere temperature difference at the time of turning off the power, and the display panel and the external atmosphere temperature difference at the time of starting the power supply.

  In this display device, the temperature difference prediction information of all blocks is stored in the memory means for the temperature difference prediction information detected by the detection means, and the temperature difference prediction information of all blocks stored in the memory means at the time of power activation is stored. The correction is made based on the temperature detected by the first or second temperature detection means, and the temperature of the display panel is predicted. Thereby, the panel temperature difference after power activation can be estimated accurately.

  Further, in this display device, a display panel for displaying a video signal input from the outside, and a detection means for dividing the video signal into a plurality of blocks, predicting the temperature of the display panel in each block, and obtaining temperature difference prediction information Non-volatile memory means for storing temperature difference prediction information, brightness control means for controlling the brightness of the display panel in accordance with the predicted temperature value, and first temperature detection means for detecting temperature information in the vicinity of the display panel And a second temperature detecting means for detecting the ambient temperature of the display device. Thus, without storing the temperature information detected by the temperature detecting means in the memory, the temperature difference prediction information stored in the memory means at the time of power activation and the temperature information detected by the first and second temperature detecting means are displayed. The brightness can be controlled by predicting the panel temperature.

  ADVANTAGE OF THE INVENTION According to this invention, even if it is a high definition panel, it becomes possible to provide the display apparatus which can improve image display quality, without increasing noise, and the drive method of the panel.

  Hereinafter, a plasma display device will be described with reference to the drawings as an example of a display device according to an embodiment of the present invention.

(Embodiment 1)
Hereinafter, a plasma display device will be described as an example of the display device according to the present invention. FIG. 1 is an exploded perspective view showing a structure of a plasma display panel 10 of a plasma display device according to an embodiment of the present invention. On the front plate 21 made of glass, a plurality of display electrode pairs 24 each including a scanning electrode 22 and a sustain electrode 23 are formed. A dielectric layer 25 is formed so as to cover the scan electrode 22 and the sustain electrode 23, and a protective layer 26 is formed on the dielectric layer 25.

  In addition, the protective layer 26 has been used as a panel material in order to lower the discharge start voltage in the discharge cell. When neon (Ne) and xenon (Xe) gas is sealed, the secondary layer has a large secondary electron emission coefficient and is durable. It is formed from a material mainly composed of MgO.

  A plurality of data electrodes 32 are formed on the back plate 31, a dielectric layer 33 is formed so as to cover the data electrodes 32, and a grid-like partition wall 34 is formed thereon. A phosphor layer 35 that emits light of each color of red (R), green (G), and blue (B) is provided on the side surface of the partition wall 34 and on the dielectric layer 33.

  The front plate 21 and the back plate 31 are arranged to face each other so that the display electrode pair 24 and the data electrode 32 intersect with each other with a minute discharge space interposed therebetween, and the outer periphery thereof is sealed with a sealing material such as glass frit. Has been. A mixed gas of neon and xenon is sealed as a discharge gas in the internal discharge space. The discharge space is partitioned into a plurality of sections by partition walls 34, and discharge cells are formed at the intersections between the display electrode pairs 24 and the data electrodes 32. These discharge cells discharge and emit light to display an image.

  Note that the structure of the panel 10 is not limited to the above-described structure, and for example, the panel 10 may include a stripe-shaped partition wall.

  FIG. 2 is an electrode array diagram of panel 10 in accordance with the exemplary embodiment of the present invention. The panel 10 includes n scan electrodes SC1 to SCn (scan electrodes 22 in FIG. 1) and n sustain electrodes SU1 to SUn (sustain electrodes 23) extended in the row direction, and is extended in the column direction. In addition, m data electrodes D1 to Dm (data electrode 32 in FIG. 1) are arranged. A discharge cell is formed at a portion where a pair of scan electrode SCi (i = 1 to n) and sustain electrode SUi intersects with one data electrode Dj (j = 1 to m), and is formed in the discharge space. The number of discharge cells is m × n.

  Next, a driving voltage waveform for driving the panel 10 and an outline of the operation will be described.

  The plasma display device according to the present embodiment performs gradation display by subfield method, that is, by dividing one field period into a plurality of subfields and controlling light emission / non-light emission of each discharge cell for each subfield. Each subfield has an initialization period, an address period, and a sustain period.

  FIG. 3 is a drive voltage waveform diagram applied to each electrode of panel 10 in accordance with the exemplary embodiment of the present invention. FIG. 3 shows drive voltage waveforms of two subfields, that is, a subfield that performs an initialization operation on all discharge cells (hereinafter referred to as “all-cell initialization subfield”), and selective initialization. A subfield for performing an operation (hereinafter referred to as a “selective initialization subfield”) is shown. Here, the all-cell initialization subfield will be described. The drive voltage waveforms in the other subfields are almost the same. Further, scan electrode SCi, sustain electrode SUi, and data electrode Dk in the following represent electrodes selected from the respective electrodes based on image data.

  In the first half of the initialization period of the first SF, which is the all-cell initialization subfield, 0 (V) is applied to the data electrodes D1 to Dm and the sustain electrodes SU1 to SUn, respectively, and the sustain electrodes SU1 are applied to the scan electrodes SC1 to SCn. A ramp waveform voltage (hereinafter referred to as “up-ramp waveform voltage”) that gradually rises from voltage Vi1 that is equal to or lower than the discharge start voltage to voltage Vi2 that exceeds the discharge start voltage is applied to SUn (hereinafter referred to as “up-ramp waveform voltage”). (The maximum value of the up-ramp waveform voltage applied to scan electrodes SC1 to SCn is referred to as “initialization voltage Vi2”).

  While the rising ramp waveform voltage rises, weak initializing discharges are continuously generated between scan electrodes SC1 to SCn, sustain electrodes SU1 to SUn, and data electrodes D1 to Dm. Negative wall voltage is accumulated on scan electrodes SC1 to SCn, and positive wall voltage is accumulated on data electrodes D1 to Dm and sustain electrodes SU1 to SUn. The wall voltage above the electrode represents a voltage generated by wall charges accumulated on the dielectric layer covering the electrode, the protective layer, the phosphor layer, and the like.

  In the latter half of the initialization period, positive voltage Ve1 is applied to sustain electrodes SU1 to SUn, 0 (V) is applied to data electrodes D1 to Dm, and sustain electrodes SU1 to SUn are applied to scan electrodes SC1 to SCn. In contrast, a ramp waveform voltage (hereinafter referred to as a “down-ramp waveform voltage”) that gently falls from a voltage Vi3 that is equal to or lower than the discharge start voltage to a voltage Vi4 that exceeds the discharge start voltage is applied. During this time, weak initializing discharges are continuously generated between scan electrodes SC1 to SCn, sustain electrodes SU1 to SUn, and data electrodes D1 to Dm. Then, the negative wall voltage above scan electrodes SC1 to SCn and the positive wall voltage above sustain electrodes SU1 to SUn are weakened, and the positive wall voltage above data electrodes D1 to Dm is adjusted to a value suitable for the write operation. The Thus, the all-cell initializing operation for performing the initializing discharge on all the discharge cells is completed.

  In the subsequent address period, voltage Ve2 is first applied to sustain electrodes SU1 to SUn, and voltage Vc is applied to scan electrodes SC1 to SCn.

  Then, a negative scan pulse voltage Va is applied to the scan electrode SC1 in the first row, and the data electrode Dk (k = 1 to m) of the discharge cell to be emitted in the first row among the data electrodes D1 to Dm is positive. The write pulse voltage Vd is applied. As a result, a discharge is generated between data electrode Dk and scan electrode SC1. In addition, using this discharge as a trigger, a discharge can be generated between sustain electrode SU1 and scan electrode SC1 in a region intersecting with data electrode Dk. Thus, an address discharge occurs in the discharge cell to emit light, a positive wall voltage is accumulated on scan electrode SC1, a negative wall voltage is accumulated on sustain electrode SU1, and a negative wall voltage is also accumulated on data electrode Dk. Accumulated.

  The above address operation is performed until the discharge cell in the nth row, and the address period ends.

  In the subsequent sustain period, first, positive sustain pulse voltage Vs is applied to scan electrodes SC1 to SCn, and a ground potential that is a base potential, that is, 0 (V) is applied to sustain electrodes SU1 to SUn. Then, in the discharge cell in which the address discharge has occurred, a sustain discharge occurs between scan electrode SCi and sustain electrode SUi, and phosphor layer 35 emits light due to the ultraviolet rays generated at this time. In the discharge cells in which no address discharge has occurred during the address period, no sustain discharge occurs, and the wall voltage at the end of the initialization period is maintained.

  Thereafter, similarly, the sustain electrodes of the number obtained by multiplying the luminance weight by the luminance magnification are alternately applied to the scan electrodes SC1 to SCn and the sustain electrodes SU1 to SUn, and a potential difference is given between the electrodes of the display electrode pair 24, thereby writing. The sustain discharge is continuously performed in the discharge cell that has caused the address discharge in the period.

  Subsequent subfield operations are substantially the same as those described above except for the number of sustain pulses in the sustain period, and thus description thereof is omitted. The above is the outline of the drive voltage waveform applied to each electrode of panel 10 in the present embodiment.

  Next, the configuration of the plasma display device of the present embodiment will be described. FIG. 4 is a circuit block diagram illustrating a plasma display device as an example. The plasma display device includes a panel 10, a tuner 41, a video signal processing circuit 43, a microcomputer 44, and a drive circuit that drives the panel 10. As a drive circuit, an image signal processing circuit 50, a data electrode drive circuit 52, a scan electrode drive circuit 53, a sustain electrode drive circuit 54, a timing generation circuit 55, and a power supply circuit (not shown) for supplying necessary power to each circuit block It has.

  The tuner 41 extracts a video signal from the reception signal received by the antenna 40 and outputs it to the subsequent stage.

  The video signal processing circuit 43 outputs the video signal output from the tuner 41 to the subsequent stage as a display video signal sig. The microcomputer 44 (hereinafter referred to as “microcomputer”) receives information sent from the video signal processing circuit 43 and information from the memory 42 and the temperature sensor 45, and whether or not brightness control of the video to be displayed is necessary. Judging. When brightness control is necessary, the brightness control is performed by the brightness control unit 60. The image signal processing circuit 50 converts the video signal sig output from the video signal processing circuit 43 into image data indicating light emission / non-light emission for each subfield.

  The timing generation circuit 55 generates various timing signals for controlling the operation of each circuit block and supplies the timing signals to the respective circuit blocks. Scan electrode driving circuit 53 includes an initialization waveform generating circuit 63 for generating an initialization waveform voltage applied to scan electrodes SC1 to SCn in the initialization period, and a sustain pulse generating circuit for generating a sustain pulse voltage in the sustain period. (Not shown) has a scan pulse generation circuit (not shown) for generating a scan pulse voltage in the address period, and drives each of the scan electrodes SC1 to SCn based on the timing signal.

  The data electrode drive circuit 52 converts the image data for each subfield into a signal corresponding to each data electrode D1 to Dm, and drives each data electrode D1 to Dm based on the timing signal. Sustain electrode drive circuit 54 includes a sustain pulse generation circuit and a circuit for generating voltage Ve1 and voltage Ve2, and drives sustain electrodes SU1 to SUn based on a timing signal.

  Next, a first luminance control method of the plasma display device configured as described above will be described. The signal detection unit 61 of the video signal processing circuit 50 divides the entire screen of the panel 10 into a plurality of parts, and periodically transmits information on the signal level and the number of light emission pulses to be displayed for each block to the microcomputer 44. The temperature difference predicting unit 65 performs temperature prediction for each block of the screen divided into a plurality based on this information, and calculates the temperature difference between the blocks from this temperature predicted value. Further, the maximum value of the temperature difference between the blocks is calculated, and this is used as the predicted panel temperature difference value.

  The predicted panel temperature predicted from the information of the input video signal needs to have a time constant so as to change slowly with respect to the video that changes instantaneously. As an example of the detection period of the signal detector 61, the state of the video signal is accumulated every 0.5 seconds and transmitted twice a second. Thereby, the microcomputer 44 can predict the temperature with accuracy in seconds from the change of the video signal.

  The memory 42 is a non-volatile storage means, and holds a value even during a power-off period. The memory 42 holds a temperature difference threshold value and a brightness control state value. The microcomputer 44 determines the brightness control state in three modes from the panel temperature difference prediction value specified by the temperature difference prediction unit 65 and the temperature difference threshold value input from the memory 42. For example, it is determined that the brightness displayed on the panel is lowered / the brightness displayed on the panel is increased / the brightness displayed on the panel is not changed according to the predicted panel temperature difference value. There are three “modes” of “mode” / “room temperature mode”.

  The microcomputer 44 compares the panel temperature difference predicted value with the temperature difference threshold value, and if the panel temperature difference predicted value exceeds the temperature difference threshold value set in the memory 42, a signal is sent to the luminance control unit 60 of the image signal processing circuit 50. To control the brightness. Specifically, the luminance control unit 60 of the image signal processing circuit 50 creates video data so as to lower the luminance of the video signal to be displayed, and outputs the video data to the data electrode driving circuit 52. The luminance control unit 60 outputs a control signal for controlling the number of drive pulses output from the timing generation circuit 55, and performs control so that the luminance to be displayed is lowered.

  The initial state in which there is no difference between the panel temperature difference predicted value and the temperature difference threshold value is the “room temperature mode”, and the luminance control unit 60 of the image signal processing circuit 50 that receives the comparison result receives the standard luminance, that is, luminance control. Display in a state that does not apply.

  Further, when the predicted panel temperature difference value is lower than the temperature difference threshold value, in the “low temperature mode” and when it is lower than the standard luminance, a process of increasing the luminance is performed. However, the luminance is not further increased with the standard luminance as the upper limit.

  Next, operations from when the power source of the plasma display apparatus is turned off until the next power source activation will be described. Each time the mode is switched, the microcomputer 44 records one or more values as history information in the memory 42 as “brightness control state values”. When the power supply (not shown) is turned off, the microcomputer 44 loses the information on the predicted panel temperature difference, which is the internal state. Therefore, the temperature difference prediction unit of the microcomputer 44 is reset when the power is turned on next time. It becomes a state. The microcomputer 44 detects that the power supply is activated based on the input information, and reads the history of the “brightness control state value” recorded in the memory 42. If the “high temperature mode” exists within a set period immediately before the power is turned off, a signal is output to the luminance control unit 60 of the image signal processing circuit 50, and the luminance control is performed for a certain period after the power is turned on. To work. Note that the panel temperature difference prediction of the temperature difference prediction unit 65 restarts after the power is turned on, and after a certain period of time, the operation is switched to perform control according to the predicted value. For this reason, for example, even if there is a power supply interruption or a panel temperature difference in the state where the temperature difference of the display unit of the panel 10 exists, this can be detected, and the panel can be protected.

  Next, the second luminance control method will be described. In addition to the contents described in the first luminance control method, temperature information is transmitted to the microcomputer 44 from the temperature sensor 45 disposed in the vicinity of the panel 10. The memory 42 holds an area for recording temperature information. The microcomputer 44 periodically monitors the temperature information of the temperature sensor 45 and records the temperature information as a “temperature value” in the memory 42 whenever the temperature changes. One or more “temperature values” are recorded to form a temperature history. When the power is turned off, the temperature monitoring is also stopped, and the temperature history immediately before the power is turned off is stored in the memory 42.

  When the power source of the plasma display device is activated, the microcomputer 44 reads the past “brightness control state value” history and the temperature history which is the “temperature value” history recorded in the memory 42, and the elapsed temperature prediction unit At 64, the current panel temperature is predicted. When the “high temperature mode” exists in the history of the “brightness control state value” within the set period, the elapsed temperature prediction unit 64 determines whether the power supply is based on the difference between the temperature history recorded in the memory 42 and the value of the temperature sensor 45. A temperature change is predicted from the time of turning off to the present, and it is determined whether the temperature difference between the blocks is equal to or greater than a set threshold value, and brightness control is performed. For example, when the temperature value recorded in the memory 42 at the time of power activation is 50 ° C., and the value read from the temperature sensor 45 is 25 ° C. at this time, it is sufficient until the power is turned on after the power is turned off. As time passes, the temperature of the panel 10 is in an equilibrium state, and it is determined that the panel temperature difference between the blocks has also disappeared, and the brightness control state is set to “room temperature mode”. The relationship between the change amount of the temperature sensor 45 and the change amount of the panel temperature difference prediction may be recorded in the memory 42 in advance.

  Next, the third luminance control method will be described. In addition to the contents described in the second luminance control method, a temperature sensor 46 that monitors the external ambient temperature is connected to the microcomputer 44. The memory 42 holds an area for recording temperature information of the temperature sensor 46. Regarding the luminance control method based on the temperature information of the temperature sensor 46, control added from the second luminance control method will be described.

  When the power source of the plasma display device is activated, the elapsed temperature predicting unit 64 of the microcomputer 44 has a temperature sensor 45 recorded in the memory 42 when “high temperature mode” exists in the history of “luminance control state value” within a preset period. The current panel temperature is predicted by comparing the difference value between the temperature sensor 46 and the temperature sensor 46 and the difference value between the temperature sensor 45 and the temperature sensor 46 read when the power source is activated. Thus, since the influence of the change in the external ambient temperature can be suppressed by performing the panel temperature prediction from the difference value between the external ambient temperature and the temperature in the vicinity of the panel 10, more accurate prediction can be performed. The relationship between the change amount of the difference value between the temperature sensor 45 and the temperature sensor 46 and the change amount of the panel temperature is recorded in the memory 42 in advance.

  Next, the fourth luminance control method will be described. Unlike the contents described in the third luminance control method, the temperature information of the temperature sensor 45 and the temperature sensor 46 is not recorded in the memory 42. Regarding the brightness control method by not recording the temperature information of the temperature sensor 45 and the temperature sensor 46 in the memory 42, control different from the third brightness control method will be described.

  When the power source of the plasma display device is activated, the elapsed temperature predicting unit 64 of the microcomputer 44 reads the temperature sensor read when the power source is activated when the “high temperature mode” exists in the history of the “brightness control state value” within a preset period. 45 and the temperature sensor 46 are compared to predict the current panel temperature. When the difference value between the external ambient temperature and the temperature in the vicinity of the panel 10 is small, it is predicted that the panel temperature difference is small, and the luminance control state is set to “room temperature mode”.

  As a result, the recording area of the memory 42 is saved, and the temperature history recording process is not required, so that the panel temperature difference can be predicted efficiently and easily. The relationship between the difference value between the temperature sensor 45 and the temperature sensor 46 and the predicted value of the panel temperature difference is recorded in the memory 42 in advance.

  Next, a fifth brightness control method will be described. The use of the temperature sensor 45 is similar to the second brightness control method, but in the fifth brightness control method, the memory 42 stores temperature difference information for each of the blocks obtained by dividing the entire screen into a plurality of blocks. Is different.

  The signal detection unit 61 of the video signal processing circuit 50 divides the entire screen of the panel 10 into a plurality of pieces, and transmits information on the signal level and the number of light emission pulses to the microcomputer 44 for each block. The temperature difference prediction unit 65 predicts the temperature of each block based on this information, and calculates the temperature difference between the blocks. Normally, when the predicted temperature difference exceeds the threshold set in the memory 42, a signal is sent to the luminance control unit 60 to control the luminance. The luminance control unit 60 controls the number of drive pulses output from the timing generation circuit 55. The luminance is controlled by the number of drive pulses.

  At this time, the microcomputer 44 updates and records the temperature difference information of all the blocks in the memory 42 whenever there is a change. Also, the read value of the temperature sensor 45 is recorded in the memory 42 in the same manner. At the time of power activation, the microcomputer 44 reads the temperature difference information of all the blocks recorded in the memory 42, and the elapsed temperature prediction unit 64 estimates the temperature change from the last power-off to the present, Predict the temperature difference value at. If there is a block whose panel temperature difference is larger than the threshold value among all the blocks, it is determined as “high temperature mode” and brightness control is performed. Accordingly, the panel temperature difference can be predicted more accurately than the determination from the brightness control state recorded in the memory 42 before the power is turned off. Further, in the second luminance control method, the panel temperature difference prediction after power-on was started after being once reset, but in the fifth luminance control method, it is stored in the memory 42. The initial state of the panel temperature difference prediction at the time of power activation can be set from the temperature difference information of all blocks before the power is turned off, and the panel temperature difference prediction can be used effectively immediately after the power is activated.

  As a prediction method in the elapsed temperature prediction unit 64, a temperature sensor 46 may be added and a third luminance control method may be used.

  In the description of the first to fifth brightness control methods, the panel temperature difference is predicted by the microcomputer 44. However, the brightness control is performed by providing a panel temperature difference prediction means in the image signal processing circuit instead of the microcomputer 44. Can also be done.

  According to the present invention, it is possible to predict the panel temperature at the time of power activation without using a sub power source, and to perform brightness control, so that the display unit is excessively damaged while realizing power saving and low cost. It is possible to prevent without performing the control.

The disassembled perspective view which shows the structure of the panel in embodiment of this invention Electrode arrangement of the panel The figure which shows the drive voltage waveform impressed to each electrode of the panel Circuit block diagram of plasma display device in accordance with exemplary embodiment of the present invention

DESCRIPTION OF SYMBOLS 10 Panel 21 Front plate 22 Scan electrode 23 Sustain electrode 24 Display electrode pair 25, 33 Dielectric layer 26 Protective layer 31 Back plate 32 Data electrode 34 Partition 35 Phosphor layer 40 Antenna 41 Tuner 42 Memory 43 Video signal processing circuit 44 Microcomputer 45, 46 Temperature sensor 50 Image signal processing circuit 52 Data electrode drive circuit 53 Scan electrode drive circuit 54 Sustain electrode drive circuit 55 Timing generation circuit 60 Brightness control unit 61 Signal detection unit 63 Initialization waveform generation circuit 64 Elapsed temperature prediction unit 65 Temperature Difference prediction unit

Claims (3)

A display panel for displaying an externally input video signal;
Detecting means for dividing the display panel into a plurality of blocks, predicting the temperature of the block from the video signal corresponding to the block, and obtaining temperature difference prediction information between the blocks;
Non-volatile memory means for storing the temperature difference prediction information;
A display device comprising: brightness control means for controlling brightness displayed on the display panel based on the temperature difference prediction information stored in the memory means when the power is turned on. A display panel for displaying an externally input video signal;
Detecting means for dividing the display panel into a plurality of blocks, predicting the temperature of the block from the video signal corresponding to the block, and obtaining temperature difference prediction information between the blocks;
First temperature detecting means for detecting temperature information in the vicinity of the display panel;
Nonvolatile memory means for storing the temperature information detected by the first temperature detection means and the temperature difference prediction information;
A display device comprising: a temperature control means for controlling brightness displayed on the display panel based on the temperature difference prediction information stored in the memory means and the temperature information when the power is turned on. A display panel for displaying an externally input video signal;
Detecting means for dividing the display panel into a plurality of blocks, predicting the temperature of the block from the video signal corresponding to the block, and obtaining temperature difference prediction information between the blocks;
First temperature detecting means for detecting temperature information in the vicinity of the display panel;
A second temperature detecting means for detecting an external ambient temperature;
Nonvolatile memory means for storing the temperature information detected by the first temperature detection means, the external ambient temperature detected by the second temperature detection means, and the temperature difference prediction information;
And a brightness control means for controlling brightness displayed on the display panel based on the temperature difference prediction information stored in the memory means, the external ambient temperature, and the temperature information when the power is turned on. apparatus.

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