JP2008209843A - Plasma display device and driving method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To control a detection temperature so as to attain a value below a threshold without frequently changing the image display brightness of a plasma display device. <P>SOLUTION: The plasma display device 100 equipped with a plasma display panel 10 and a driving circuit for driving the same includes a temperature sensor 47 which detects the temperature of the inside of the plasma display device 100, and a brightness magnification setting circuit 46 which sets the brightness magnification so as to attain the value below the brightness magnification limit value based on the detected temperature. The brightness magnification setting circuit 46 decreases the brightness magnification limit value when the detected temperature is above the threshold and the detected temperature does not fall, and increases the brightness magnification limit value when the detected temperature is less than the temperature threshold and the detected temperature does not increase. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a plasma display device used for a wall-mounted television, a large monitor, and the like and a driving method thereof.

  A typical AC surface discharge type panel as a plasma display panel (hereinafter abbreviated as “panel”) has a large number of discharge cells formed between a front plate and a back plate arranged to face each other.

  A plurality of pairs of display electrodes consisting of scan electrodes and sustain electrodes are formed on the front glass substrate in parallel on the front glass substrate, and a plurality of data electrodes are formed on the rear glass plate in parallel on the rear glass substrate. Then, the front plate and the rear plate are arranged opposite to each other so that the display electrode pair and the data electrode are three-dimensionally crossed and sealed, and a discharge gas is sealed in the internal discharge space. Here, a discharge cell is formed in a portion where the display electrode pair and the data electrode face each other.

  As a method of driving the panel, a subfield method, that is, a method of displaying an image by combining subfields to emit light after dividing one field period into a plurality of subfields is generally used. Each subfield has an initialization period, an address period, and a sustain period. In the initialization period, an initialization discharge is generated, and wall charges necessary for the subsequent address operation are formed on each electrode. In the address period, address discharge is selectively generated in the discharge cells to be displayed to form wall charges. In the sustain period, the number of sustain pulses obtained by multiplying the luminance weight determined in advance for each subfield by a proportional coefficient (hereinafter referred to as “luminance magnification”) is alternately applied to the display electrode pairs to cause address discharge. An image is displayed by generating a sustain discharge in the discharge cell to emit light.

  As one of the techniques for improving the image display luminance using the subfield method, a technique for controlling the number of sustain pulses applied to the display electrode pair in the sustain period is disclosed in, for example, Patent Document 1. In Patent Document 1, a luminance magnification is set based on an average luminance level (hereinafter referred to as “APL”) of an image signal, and the number of sustain pulses in each subfield is set to 1 ×, 2 ×, 3 ×,. And a method for improving the luminance by increasing the number is described.

However, when the luminance is increased by increasing the number of sustain pulses, the power consumption of the plasma display device also increases and the temperature inside the housing rises. If the panel temperature or the temperature of the drive circuit rises too much, the image display operation may be stopped due to the operation of the protection circuit. For this reason, a method is disclosed in which the temperature of the plasma display device is detected and the temperature is lowered by limiting the number of sustain pulses if the temperature is too high (for example, Patent Document 2).
JP-A-8-286636 JP 2004-325568 A

  However, if the brightness magnification is feedback controlled so that the temperature of the plasma display device is equal to or lower than the temperature threshold by simply comparing the detected temperature value with the temperature threshold, the detected temperature becomes the temperature threshold. The image display brightness frequently changes when the temperature is close to, causing a problem that the image display quality is lowered.

  The present invention has been made in view of the above problems, and provides a plasma display device that controls a detected temperature to be equal to or lower than a temperature threshold without frequently changing image display brightness and a driving method thereof. Objective.

  The present invention has a panel having a plurality of discharge cells each having a display electrode pair, and a sustain period in which a sustain pulse of a number obtained by multiplying a luminance weight by a luminance magnification is applied to the display electrode pair to generate a sustain discharge in the discharge cell. A plasma display device including a drive circuit that displays an image using a plurality of subfields, the drive circuit detecting a temperature inside the plasma display device and outputting a detected temperature, and a detection temperature A luminance magnification setting circuit for setting the luminance magnification so as to be equal to or lower than the original luminance magnification limit value, and the luminance magnification setting circuit has a luminance magnification when the detected temperature is equal to or higher than the temperature threshold and the detected temperature does not decrease. The limit value is decreased, and when the detected temperature is lower than the temperature threshold and the detected temperature does not increase, the brightness magnification limit value is increased. An object of the present invention is to provide a plasma display device that controls the detected temperature to be equal to or lower than the temperature threshold without frequently changing the image display luminance.

  In addition, the luminance magnification setting circuit of the plasma display device of the present invention includes an APL calculating unit that calculates the APL of the image signal, a basic magnification setting unit that sets the basic luminance magnification based on the APL, and a detection temperature that is set in advance. A temperature comparison unit for comparing with a threshold value, a temperature change determination unit for determining an increase or decrease in the detected temperature, a limit value setting unit for setting a luminance magnification limit value based on outputs of the temperature comparison unit and the temperature change determination unit, A configuration may be provided that includes a luminance magnification limiting unit that limits the basic luminance magnification output from the basic magnification setting unit to a luminance magnification limiting value or less.

  The present invention also relates to a driving method of a plasma display device for detecting an internal temperature and applying a sustain pulse of a number obtained by multiplying a luminance weight by a luminance magnification to a display electrode pair to generate a sustain discharge to display an image. The brightness magnification is set to be less than the brightness magnification limit value based on the detected internal temperature. If the internal temperature is equal to or higher than the temperature threshold and the internal temperature has not decreased, the brightness magnification is set. The limit value is decreased, and the brightness magnification limit value is increased when the detected temperature is lower than the temperature threshold and the detected temperature is not increased. By this method, it is possible to provide a driving method of a plasma display device that controls the detected temperature to be equal to or lower than the temperature threshold without frequently changing the image display luminance.

  According to the present invention, it is possible to provide a plasma display apparatus that controls the detected temperature to be equal to or lower than the temperature threshold without frequently changing the image display luminance, and a driving method thereof.

(Embodiment)
FIG. 1 is an exploded perspective view showing a structure of panel 10 according to the embodiment of the present invention. A plurality of display electrode pairs 24 each including a scanning electrode 22 and a sustaining electrode 23 are formed on a glass front substrate 21. A dielectric layer 25 is formed so as to cover the display electrode pair 24, and a protective layer 26 is formed on the dielectric layer 25. A plurality of data electrodes 32 are formed on the back substrate 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 red, green, and blue light is provided on the side surface of the partition wall 34 and on the dielectric layer 33.

  The front substrate 21 and the rear substrate 31 are arranged to face each other so that the display electrode pair 24 and the data electrode 32 cross each other across a minute discharge space, and the outer periphery thereof is sealed with a sealing material such as glass frit. It is worn. In the discharge space, for example, a mixed gas of neon and xenon is enclosed as a discharge gas. 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. In panel 10, n scanning electrodes SC1 to SCn (scanning electrode 22 in FIG. 1) and n sustaining electrodes SU1 to SUn (sustaining electrode 23 in FIG. 1) long in the row direction are arranged and long in the column direction. M data electrodes D1 to Dm (data electrode 32 in FIG. 1) are arranged. A discharge cell is formed at a portion where one pair of scan electrode SCi (i = 1 to n) and sustain electrode SUi intersects one data electrode Dj (j = 1 to m), and the discharge cell is in the discharge space. M × n are formed.

  Next, a driving voltage waveform for driving panel 10 and its operation will be described. The plasma display device displays an image by subfield method, that is, 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. In the initializing period, initializing discharge is generated, and wall charges necessary for the subsequent address discharge are formed on each electrode. In the address period, address discharge is selectively generated in the discharge cells to emit light to form wall charges. In the sustain period, a sustain pulse of the number obtained by multiplying the luminance weight determined in advance for each subfield by the luminance magnification is alternately applied to the display electrode pair to generate a sustain discharge in the discharge cell in which the address discharge is generated. Make it emit light.

  In the present embodiment, one field is divided into 10 subfields (first SF, second SF,..., 10th SF), and each subfield is, for example, (1, 2, 3, 6, 11, 18, 30, 44, 60, 80). In addition, the initialization operation is performed in all the discharge cells in the initialization period of the first SF, and the initialization operation is selectively performed in the discharge cells in which the sustain discharge is generated in the initialization period of the second SF to the tenth SF. However, in the present invention, the number of subfields and the luminance weight of each subfield are not limited to the above values.

  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 in two subfields, but drive voltage waveforms in other subfields are substantially the same.

  In the first half of the initializing period of the first SF, 0 (V) is applied to the data electrodes D1 to Dm and the sustain electrodes SU1 to SUn, respectively, and the discharge start voltage with respect to the sustain electrodes SU1 to SUn is applied to the scan electrodes SC1 to SCn. A ramp waveform voltage that gently rises from the voltage Vi1 below toward the voltage Vi2 that exceeds the discharge start voltage is applied. While this ramp waveform voltage rises, a weak initializing discharge occurs 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. Here, the wall voltage on 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, and scan electrodes SC1 to SCn receive a discharge start voltage from voltage Vi3 that is equal to or lower than the discharge start voltage with respect to sustain electrodes SU1 to SUn. A ramp waveform voltage that gently falls toward the exceeding voltage Vi4 is applied. During this time, weak initializing discharges occur between scan electrodes SC1 to SCn, sustain electrodes SU1 to SUn, and data electrodes D1 to Dm, respectively. Then, the negative wall voltage on scan electrodes SC1 to SCn and the positive wall voltage on sustain electrodes SU1 to SUn are weakened, and the positive wall voltage on data electrodes D1 to Dm is adjusted to a value suitable for the write operation. The Thus, the initialization operation ends.

  As the drive voltage waveform in the initialization period, only the voltage waveform in the latter half of the initialization period may be applied as shown in the initialization period of the second SF in FIG. Initializing discharge is selectively generated in the discharge cells that have undergone sustain discharge in the sustain period of the field.

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

  Next, the negative scan pulse 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 Vd is applied. At this time, the voltage difference at the intersection between the data electrode Dk and the scan electrode SC1 is the difference between the wall voltage on the data electrode Dk and the wall voltage on the scan electrode SC1 due to the difference between the externally applied voltages (Vd−Va). It becomes the sum and exceeds the discharge start voltage. Then, address discharge occurs between data electrode Dk and scan electrode SC1, and between sustain electrode SU1 and scan electrode SC1, positive wall voltage is accumulated on scan electrode SC1, and negative wall is applied on sustain electrode SU1. A voltage is accumulated, and a negative wall voltage is also accumulated on the data electrode Dk.

  In this manner, an address operation is performed in which an address discharge is caused in the discharge cells to be lit in the first row and wall voltage is accumulated on each electrode. On the other hand, the voltage at the intersection of the data electrodes D1 to Dm to which the address pulse Vd is not applied and the scan electrode SC1 does not exceed the discharge start voltage, so that address discharge does not occur. The above address operation is performed until the discharge cell in the nth row of scan electrode SCn, and the address period ends.

  In the sustain period, first, sustain pulse Vs is applied to scan electrodes SC1 to SCn, and 0 (V) is applied to sustain electrodes SU1 to SUn. Then, in the discharge cell in which the address discharge has occurred, the voltage difference between scan electrode SCi and sustain electrode SUi is the sustain pulse Vs, and the difference between the wall voltage on scan electrode SCi and the wall voltage on sustain electrode SUi is added. The discharge start voltage is exceeded. Then, a sustain discharge occurs between scan electrode SCi and sustain electrode SUi, and phosphor layer 35 emits light by the ultraviolet rays generated at this time. Then, a negative wall voltage is accumulated on scan electrode SCi, and a positive wall voltage is accumulated on sustain electrode SUi. Further, a positive wall voltage is accumulated on the data electrode Dk. 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.

  Subsequently, 0 (V) is applied to scan electrodes SC1 to SCn, and sustain pulse Vs is applied to sustain electrodes SU1 to SUn. Then, in the discharge cell in which the sustain discharge has occurred, the voltage difference between the sustain electrode SUi and the scan electrode SCi exceeds the discharge start voltage, so that the sustain discharge occurs again between the sustain electrode SUi and the scan electrode SCi. A negative wall voltage is accumulated on SUi, and a positive wall voltage is accumulated on scan electrode SCi.

  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.

  At the end of the sustain period, a so-called narrow pulse-like potential difference is applied between scan electrodes SC1 to SCn and sustain electrodes SU1 to SUn, and the positive wall voltage on data electrode Dk is left while scanning. Part or all of the wall voltage on electrode SCi and sustain electrode SUi is erased. Thus, the maintenance operation in the maintenance period is completed.

  Although the details will be described later, the luminance magnification is controlled based on the APL of the image signal. Furthermore, it is controlled depending on the detection temperature T of a temperature sensor provided in the plasma display device.

  The subsequent operation of the subfield is substantially the same as the operation of the first SF, and thus description thereof is omitted.

  Next, a driving circuit for driving the panel 10 and its operation will be described. FIG. 4 is a circuit block diagram of plasma display device 100 in accordance with the exemplary embodiment of the present invention. The plasma display device 100 includes a panel 10, an image signal processing circuit 41, a data electrode drive circuit 42, a scan electrode drive circuit 43, a sustain electrode drive circuit 44, a timing generation circuit 45, a luminance magnification setting circuit 46, a temperature sensor 47, and each circuit. A power supply circuit (not shown) for supplying power necessary for the block is provided.

  The image signal processing circuit 41 converts the input image signal into image data indicating light emission / non-light emission for each subfield. The data electrode drive circuit 42 converts the image data for each subfield into signals corresponding to the data electrodes D1 to Dm, and drives the data electrodes D1 to Dm.

  The temperature sensor 47 includes a generally known thermal element such as a thermistor or a thermocouple used for detecting the temperature, detects the temperature inside the plasma display device 100, and outputs a detected temperature T. In the present embodiment, in order to increase the temperature detection accuracy, the output of the thermal element is read every 50 ms, the average value for 20 times is calculated, and the detected temperature T is output every 5 s. Further, the temperature sensor 47 is preferably installed at a position where the heat of the panel 10 is not directly affected. For example, various drives supported on the front surface of a chassis member (not shown) that supports the panel 10 with an air layer interposed therebetween. It is installed on the surface of the circuit board.

  The luminance magnification setting circuit 46 sets the luminance magnification depending on the APL of the image signal, and becomes a luminance magnification limit value H or later described below based on the value of the detected temperature T detected by the temperature sensor 47 and the change thereof. The luminance magnification is set as follows.

  The timing generation circuit 45 determines the number of sustain pulses in the sustain period of each subfield based on the luminance magnification set by the luminance magnification setting circuit 46, and each circuit block based on the horizontal synchronization signal and the vertical synchronization signal. Various timing signals for controlling the operation are generated and supplied to the respective circuit blocks. Scan electrode drive circuit 43 drives each of scan electrodes SC1 to SCn based on the timing signal, and sustain electrode drive circuit 44 drives sustain electrodes SU1 to SUn based on the timing signal.

  FIG. 5 is a circuit block diagram of the luminance magnification setting circuit 46 according to the embodiment of the present invention. The luminance magnification setting circuit 46 includes an APL calculation unit 51, a basic magnification setting unit 52, a luminance magnification limitation unit 53, a temperature comparison unit 61, a temperature change determination unit 62, an absolute value storage unit 63, and a limit value setting. Part 64.

  The APL calculation unit 51 calculates the APL (average luminance level) of the image signal. Specifically, the APL is calculated by using a generally known method such as accumulating the luminance value of the image signal over one field period or one frame period. In addition to using the luminance value, a method of calculating the APL by accumulating each of the primary color signals of red, green, and blue over one field period and obtaining an average value thereof may be used.

  The basic magnification setting unit 52 sets the luminance magnification based on the APL of the image signal and outputs it as the basic luminance magnification. FIG. 6 is a diagram showing the characteristics of the basic magnification setting unit 52 in the embodiment of the present invention. The basic magnification setting unit 52 sets the basic luminance magnification small for an image signal with a high APL, and sets the basic luminance magnification large for an image signal with a low APL. In the present embodiment, for an image signal having an APL of 10% or less, the basic luminance magnification is “3.5”, and the basic luminance magnification is set to decrease as the APL increases. The basic luminance magnification is set to “1” for an image signal having an APL of 90% or more. Thus, by setting the basic luminance magnification based on the APL, the number of sustain pulses is limited for a bright image signal, and the power consumption of the plasma display apparatus 100 is suppressed. For dark images with low APL, the display luminance is improved by setting a large basic luminance magnification.

  The temperature comparison unit 61 compares the detected temperature T detected by the temperature sensor 47 with a predetermined temperature threshold, which is 70 ° C. in the present embodiment, and when the detected temperature T is equal to or higher than the temperature threshold. When “1” is detected and the detected temperature T is lower than the temperature threshold value, “0” is output as the temperature comparison signal TC. Note that the temperature threshold value is desirably set as appropriate according to the specifications of the plasma display device.

  The temperature change determination unit 62 determines whether the detected temperature T detected by the temperature sensor 47 increases or decreases. In the present embodiment, the detected temperature T output from the temperature sensor 47 is compared with the detected temperature T output before that, and when the detected temperature T increases, “+1” is decreased. "-1" is output as the temperature change signal TD when there is no change.

  The absolute value storage unit 63 stores the maximum value and the minimum value of the luminance magnification limit value H. As will be described later, the maximum value and the minimum value stored here are the maximum value of the fluctuating luminance magnification limit value H (hereinafter abbreviated as “absolute maximum value Hmax”) and the minimum fluctuating luminance magnification limit value H. Value (hereinafter abbreviated as “absolute minimum value Hmin”). In the embodiment of the present invention, the absolute maximum value Hmax is “3.5” and the absolute minimum value Hmin is “1”. However, the absolute maximum value Hmax and the absolute minimum value Hmin are plasma. It is desirable to set appropriately according to the specifications of the display device.

  Limit value setting unit 64 sets luminance magnification limit value H based on the outputs of temperature comparison unit 61 and temperature change determination unit 62 and absolute maximum value Hmax and absolute minimum value Hmin stored in absolute value storage unit 63. . FIG. 7 is a diagram showing conditions for setting the luminance magnification limit value H in the embodiment of the present invention. In FIG. 7, the previous brightness magnification limit value is indicated by H (t−1), and the newly set brightness magnification limit value is indicated by H (t). If the detected temperature T is equal to or higher than the temperature threshold value Tth and the detected temperature T has not decreased, a new luminance magnification width ΔH is subtracted from the previous luminance magnification limit value H (t−1). Let it be the luminance magnification limit value H (t). However, no subtraction is performed when the new luminance magnification limit value H (t) is less than the absolute minimum value Hmin. When the detected temperature T is lower than the temperature threshold value Tth and the detected temperature T has not risen, a predetermined luminance magnification width ΔH is added to the luminance magnification limit value H (t−1) so far. A new luminance magnification limit value H (t) is set. However, when the new luminance magnification limit value H (t) exceeds the absolute maximum value Hmax, the luminance magnification width ΔH is not added. In the case of other conditions, the luminance magnification limit value H (t) is set equal to the luminance magnification limit value H (t−1).

  FIG. 8 is a flowchart for explaining the operation of limit value setting unit 64 in the embodiment of the present invention. In the present embodiment, the setting of the luminance magnification limit value H described below is executed every 5 s.

  (Step S11) First, the temperature comparison signal TC, the temperature change signal TD, the absolute maximum value Hmax, and the absolute minimum value Hmin are captured.

  (Step S12) If the temperature comparison signal TC is “1”, that is, if the detected temperature T is equal to or higher than the temperature threshold value Tth, the process proceeds to step S13; otherwise, the process proceeds to step S23.

  (Step S13) If the temperature change signal TD is “+1” or “0”, that is, if the detected temperature T has not decreased, the process proceeds to step S14; otherwise, the process proceeds to step S35.

  (Step S14) If the value obtained by subtracting the predetermined luminance magnification width ΔH from the previous luminance magnification limit value H (t-1) is equal to or larger than the absolute minimum value Hmin, the process proceeds to step S15. Otherwise, the process proceeds to step S35.

  (Step S15) The new luminance magnification limit value H (t) is set to the luminance magnification limitation value H (t) = H (t−1) −ΔH, and the process returns to Step S11.

  (Step S23) If the temperature change signal TD is “−1” or “0”, that is, if the detected temperature T has not risen, the process proceeds to step S24; otherwise, the process proceeds to step S35.

  (Step S24) If the value obtained by adding the predetermined luminance magnification width ΔH to the previous luminance magnification limit value H (t-1) is equal to or smaller than the absolute maximum value Hmax, the process proceeds to step S25, and if not, the process proceeds to step S35.

  (Step S25) The new brightness magnification limit value H (t) is set to the brightness magnification limit value H (t) = H (t−1) + ΔH, and the process returns to step S11.

  (Step S35) The new luminance magnification limit value H (t) is set to the luminance magnification limitation value H (t) = H (t−1), and the process returns to step S11.

  As described above, the limit value setting unit 64 sets the brightness magnification limit value H every 5 s. As described above, it is desirable to set the luminance magnification limit value H in synchronization with the cycle in which the temperature sensor 47 outputs the detected temperature T.

  The luminance magnification limiting unit 53 limits the basic luminance magnification output from the basic magnification setting unit 52 to a luminance magnification limiting value H or less and outputs it as a luminance magnification. By controlling in this way, the maximum value of the luminance magnification is limited, and the luminance magnification can be controlled so that the detected temperature T does not rise above the temperature threshold value Tth.

  Next, the operation of the luminance magnification setting circuit 46 will be described with an example. 9A and 9B are diagrams for explaining the operation of the luminance magnification setting circuit 46 according to the embodiment of the present invention. FIG. 9A shows the detected temperature T, and FIG. An example is shown.

  When the detected temperature T is low (before time t1), the luminance magnification limit value H becomes the absolute maximum value Hmax, and the luminance magnification limiting unit 53 does not limit the basic luminance magnification. The luminance magnification at this time is set based on the APL of the image signal according to the characteristics shown in FIG.

  Thereafter, when the detected temperature T starts to increase due to a bright image being displayed or the like and the detected temperature T exceeds the temperature threshold value Tth at time t1, as shown in FIG. 7 or FIG. Sets the luminance magnification limit value H (t) to a value H (t−1) −ΔH that is smaller than the previous luminance magnification limitation value H (t−1) by the luminance magnification width ΔH.

  Then, when the detected temperature T starts to decrease at time t2, even if the detected temperature T is larger than the temperature threshold value Tth, the brightness magnification limit value H up to that time is not reduced without decreasing the brightness magnification limit value H (t). Set to the same value as (t-1). This is to prevent the brightness magnification limit value H (t) from being decreased and further accelerate the decrease in the detected temperature T even though the detected temperature T has started to decrease. As a result, a rapid change in temperature can be suppressed, and therefore the image display luminance does not change rapidly. Further, the image display luminance is not lowered too much by reducing the luminance magnification more than necessary.

  When the detected temperature T becomes lower than the temperature threshold Tth at time t3, as shown in FIG. 7 or FIG. 8, the luminance magnification limiting unit 53 sets the luminance magnification limiting value H (t) up to that time. The value is set to H (t−1) + ΔH, which is larger than the luminance magnification limit value H (t−1) by the luminance magnification width ΔH.

  When the detected temperature T starts to increase at time t4, even if the detected temperature T is smaller than the temperature threshold value Tth, the luminance magnification limit value H up to that time is not increased without increasing the luminance magnification limit value H (t). Set to the same value as (t-1). This is for preventing the acceleration of the increase in the detection temperature T by increasing the luminance magnification limit value H (t) even though the detection temperature T has started to increase.

  By driving as described above, a rapid change in the detection temperature T can be suppressed, the luminance magnification limit value H does not fluctuate frequently, and thus the detection temperature does not change frequently. T can be controlled to be equal to or lower than the temperature threshold value Tth.

  In this embodiment, the luminance magnification width ΔH is set to 0.05 times. However, as the luminance magnification width ΔH, even if the luminance magnification limit value H is increased or decreased, a change in image display luminance is visually recognized. It is desirable to set the value to such an extent that it does not bother you, and it is desirable to set it appropriately according to the specifications of the plasma display device.

  In addition, the specific numerical values used in this embodiment are merely examples, and it is desirable to appropriately set the optimal values according to the panel characteristics, the plasma display device specifications, and the like.

  According to the present invention, power consumption can be suppressed by limiting the number of sustain pulses without greatly degrading image display quality, which is useful as a plasma display device.

The disassembled perspective view which shows the structure of the panel in embodiment of this invention Electrode arrangement of the panel Drive voltage waveform diagram applied to each electrode of the panel Circuit block diagram of plasma display device in accordance with exemplary embodiment of the present invention Circuit block diagram of luminance magnification setting circuit in the embodiment of the present invention The figure which shows the characteristic of the basic magnification setting part in embodiment of this invention The figure which shows the conditions of the setting of the brightness | luminance magnification limit value in embodiment of this invention The flowchart for demonstrating operation | movement of the limit value setting part in embodiment of this invention The figure explaining operation | movement of the luminance magnification setting circuit in embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Panel 22 Scan electrode 23 Sustain electrode 24 Display electrode pair 32 Data electrode 41 Image signal processing circuit 42 Data electrode drive circuit 43 Scan electrode drive circuit 44 Sustain electrode drive circuit 45 Timing generation circuit 46 Luminance magnification setting circuit 47 Temperature sensor 51 APL calculation Unit 52 Basic magnification setting unit 53 Luminance magnification limiting unit 61 Temperature comparison unit 62 Temperature change determination unit 63 Absolute value storage unit 64 Limit value setting unit 100 Plasma display device

Claims (3)

A plasma display panel comprising a plurality of discharge cells having display electrode pairs;
And a drive circuit for displaying an image using a plurality of subfields having a sustain period in which a sustain pulse of a number obtained by multiplying a brightness weight by a brightness magnification is applied to the display electrode pair to generate a sustain discharge in the discharge cell. A plasma display device,
The drive circuit is
A temperature sensor that detects the temperature inside the plasma display device and outputs the detected temperature;
A luminance magnification setting circuit for setting the luminance magnification to be equal to or less than a luminance magnification limit value based on the detected temperature,
The luminance magnification setting circuit decreases the luminance magnification limit value when the detected temperature is equal to or higher than a temperature threshold and the detected temperature does not decrease, and the detected temperature is lower than the temperature threshold; The plasma display apparatus, wherein the brightness magnification limit value is increased when the detected temperature does not increase. The luminance magnification setting circuit includes:
An APL calculating unit that calculates an APL of an image signal; a basic magnification setting unit that sets a basic luminance magnification based on the APL; a temperature comparing unit that compares the detected temperature with a predetermined temperature threshold; and the detection A temperature change determination unit for determining an increase or decrease in temperature, a limit value setting unit for setting the luminance magnification limit value based on outputs from the temperature comparison unit and the temperature change determination unit, and an output from the basic magnification setting unit The plasma display apparatus according to claim 1, further comprising a luminance magnification limiting unit that limits a basic luminance magnification to be less than or equal to the luminance magnification limiting value. A method of driving a plasma display device that detects an internal temperature and applies a sustain pulse of a number obtained by multiplying a brightness weight by a brightness magnification to a display electrode pair to generate a sustain discharge and display an image,
The luminance magnification is set to be equal to or less than a luminance magnification limit value based on the detected internal temperature, and when the internal temperature is equal to or higher than a temperature threshold and the internal temperature is not lowered. Decreases the brightness magnification limit value, and increases the brightness magnification limit value when the detected temperature is lower than the temperature threshold and the detected temperature is not increased. Driving method.

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