JP2008209842A - Plasma display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the power consumption of a plasma display device by limiting the number of sustain pulses without drastically degrading image display quality. <P>SOLUTION: The plasma display device for displaying the image by using a plurality of subfields having a write period and a sustain period when the sustain pulses of the number obtained by multiplying a luminance weight with a luminance magnification cause a display electrode pair to generate sustain discharge, is provided with a temperature sensor for detecting the temperature within the case, a scene change detection section 61 for detecting the scene change of the image based on the image signal, and a temporally magnification setting section 62 for temporarily raising a luminance magnification when the scene change detection section 61 detects the scene change and restricting the upper limit value based on the temperature detected by the temperature sensor. <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.

  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 performing gradation display 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. Patent Document 1 describes a method of improving luminance by setting a luminance magnification based on the APL of an image signal and increasing the number of sustain pulses in each subfield by 1 ×, 2 ×, 3 ×,. Has been.

  Further, Patent Document 2 includes a scene change detection unit that detects a scene change of an input image signal and a unit that controls luminance when a scene change is detected, so that variations in luminance are less noticeable. A plasma display device is disclosed.

On the other hand, 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 panel or the temperature inside the housing is detected, and if the temperature rises too much, the number of sustain pulses is limited to lower the temperature (for example, Patent Document 3).
JP-A-8-286636 JP 2000-330505 A JP 2004-325568 A

  However, if the number of sustain pulses is limited to simply limit the temperature, the image when the temperature is limited is visually recognized as an image having a lower luminance than the actual display luminance. There is a problem that the image display quality of the image is lower than the image display quality when the temperature is not limited.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a plasma display device that can suppress power consumption by limiting the number of sustain pulses without greatly degrading image display quality.

  The present invention includes a panel including a plurality of discharge cells each including a display electrode pair, a temperature sensor that detects a temperature inside the apparatus, an address period in which an address discharge is selectively generated in the discharge cells, and a luminance weight. Display apparatus for displaying an image using a plurality of subfields having a sustain period in which a sustain discharge is generated in a discharge cell in which an address discharge is generated by applying a number of sustain pulses multiplied by a luminance magnification to the display electrode pair A scene change detection unit that detects a scene change of the image based on the image signal, and temporarily increases the luminance magnification when the scene change detection unit detects the scene change and also based on the temperature detected by the temperature sensor. And a temporary magnification setting unit for limiting the upper limit value. With this configuration, it is possible to provide a plasma display device that can suppress power consumption by limiting the number of sustain pulses without significantly reducing image display quality.

  The temporary magnification setting unit of the plasma display device of the present invention includes a temporary increase value calculation unit that calculates a temporary increase value of the luminance magnification that is temporarily increased based on the APL of the image signal, and a temporary detection based on the temperature detected by the temperature sensor. A configuration including a temporary increase value limiting unit that limits the upper limit value of the increase value, and a temporary increase value attenuation unit that attenuates the temporary increase value whose upper limit value is limited after the scene change detection unit detects a scene change. There may be.

  The plasma display device of the present invention includes a basic magnification setting unit that sets a basic luminance magnification based on the APL of an image signal, a basic luminance magnification set by the basic magnification setting unit, and a temporary luminance magnification set by the temporary magnification setting unit. Alternatively, a configuration may be provided that includes a luminance magnification calculation unit that calculates the luminance magnification based on the above.

  According to the present invention, it is possible to provide a plasma display device that can suppress power consumption by limiting the number of sustain pulses without significantly reducing image display quality.

(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 apparatus performs gradation display 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, sustain pulses of the number obtained by multiplying the luminance weight determined in advance for each subfield by the luminance magnification are alternately applied to the display electrode pair 24 to generate a sustain discharge in the discharge cell that has generated the address discharge. To 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. The wall voltage on the electrode SCi and the 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 in the sustain period is controlled based on the content of the image signal and APL. Furthermore, it is controlled depending on the temperature detected by 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 is a generally known thermal element such as a thermistor or a thermocouple that is provided inside the apparatus and used to detect the temperature inside the apparatus.

  The luminance magnification setting circuit 46 sets the luminance magnification depending on the APL of the image signal, detects a scene change of the image signal, and temporarily increases the luminance magnification for each scene change. When the temperature detected by the temperature sensor 47 is high, a temporary increase in luminance magnification is limited, and when the temperature detected by the temperature sensor 47 is higher, the luminance magnification itself is limited.

  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 calculating unit 51, a basic magnification setting unit 52, a luminance magnification calculating unit 53, a luminance magnification limiting unit 54, a scene change detecting unit 61, and a temporary magnification setting unit 62.

  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 APL by accumulating each of the primary color signals of red, blue, and green 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” times for an image signal with 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 a low APL, the display luminance is improved by setting a large luminance magnification.

  The scene change detection unit 61 uses a generally known method such as a method based on the degree of dissimilarity between frames to detect image switching based on a change in the image signal, that is, a scene change.

  The temporary magnification setting unit 62 includes a temporary increase value calculation unit 65, a temporary increase value restriction unit 66, and a temporary increase value attenuation unit 67. Then, when the scene change detection unit 61 detects a scene change, it sets a temporary luminance magnification for temporarily increasing the luminance magnification. In addition, the temporary magnification setting unit 62 limits the upper limit value of the temporary luminance magnification based on the temperature detected by the temperature sensor 47.

  The temporary increase value calculation unit 65 calculates a temporary increase value indicating the magnitude of the luminance magnification to be temporarily increased based on the APL. FIG. 7 is a diagram showing the characteristics of the temporary magnification setting unit 62 in the embodiment of the present invention, and shows the characteristics when there is no limitation on the temporary increase value due to temperature. In the present embodiment, when the APL is low, the temporary increase value increases as the APL increases. However, when the APL is too high, the temporary increase value is conversely set small. This is because when APL is sufficiently high, the power consumption is not further increased. The temporary increase value calculation unit 65 can be configured by a data conversion table using a ROM or the like.

  The temporary increase value limiting unit 66 limits the upper limit of the temporary increase value based on the temperature detected by the temperature sensor 47. FIG. 8 is a diagram illustrating the characteristics of the temporary increase value limiting unit 66 according to the embodiment of the present invention, and is a diagram illustrating the temperature T detected by the temperature sensor 47 and the upper limit value K (T) of the temporary increase value. When the temperature T detected by the temperature sensor 47 is lower than the temperature T11, the upper limit value K (T) of the temporary increase value is limited to the upper limit value K1. When the temperature T12 is higher than the temperature T11 or higher, the upper limit value K (T) of the temporary increase value is limited to the upper limit value K2 that is smaller than the upper limit value K1. When the temperature T is equal to or higher than the temperature T11 and lower than the temperature T12, the upper limit value K (T) of the temporary increase value is limited so as to decrease from the upper limit value K1 to the upper limit value K2 as the temperature T increases. .

  The temporary increase value attenuation unit 67 outputs the temporary increase value as it is immediately after the scene change detection unit 61 detects a scene change, and then gradually attenuates it at a speed that is not visually noticeable. Therefore, when the scene change detection unit 61 does not detect a scene change for a certain period of time, the temporary luminance magnification that is the output of the temporary increase value attenuation unit 67 is “0”.

  The luminance magnification calculation unit 53 adds the basic luminance magnification set by the basic magnification setting unit 52 and the temporary luminance magnification set by the temporary magnification setting unit 62, and outputs the combined luminance magnification.

  The luminance magnification limiting unit 54 limits the upper limit of the total luminance magnification output from the luminance magnification calculating unit 53 based on the temperature detected by the temperature sensor 47, and outputs it as the luminance magnification. FIG. 9 is a diagram illustrating characteristics of the luminance magnification limiting unit 54 according to the embodiment of the present invention, and is a diagram illustrating the temperature T detected by the temperature sensor 47 and the upper limit value H (T) of the total luminance magnification. When the temperature T is lower than the temperature T21, the upper limit value H (T) of the total luminance magnification is limited to the upper limit value H1. When the temperature is equal to or higher than T21, the upper limit value H (T) of the total luminance magnification is limited to decrease as the temperature increases.

  When the temperature T22 is higher than the temperature T21 or higher, the maximum value of the total luminance magnification is limited by feedback control so that the temperature does not increase any more.

  Next, the operation of the luminance magnification setting circuit 46 will be described with an example. First, the operation when the temperature detected by the temperature sensor 47 is low and the temperature is not limited will be described.

  10A and 10B are diagrams for explaining the operation of the luminance magnification setting circuit 46 according to the embodiment of the present invention. FIG. 10A is an APL output from the APL calculation unit 51, and FIG. The basic luminance magnification output from the magnification setting unit 52, the broken line in FIG. 10C is the temporary increase value output from the temporary increase value calculation unit 65, the solid line is the temporary luminance magnification output from the temporary increase value attenuation unit 67, FIG. 10D shows the total luminance magnification output from the luminance magnification calculator 53. When the output of the temperature sensor 47 is low and the temperature is not limited, the temporary increase value limiting unit 66 and the luminance magnification limiting unit 54 output the input signals as they are, and FIG. 10D shows the luminance magnification setting circuit 46. Is equal to the luminance magnification output from

  Assume that the image signal changes with time and the APL changes as shown in FIG. The APL changes stepwise at times t10, t20, and t30 because of a scene change. Since the basic luminance magnification and APL change with an inverse correlation as shown in FIG. 6, the basic luminance magnification at this time changes as shown in FIG.

  Further, since the temporary increase value and the APL have a relationship as shown in FIG. 7, the temporary increase value at this time changes as shown by a broken line in FIG. Then, as shown by the solid line in FIG. 10C, the temporary increase value attenuation unit 67 outputs the temporary increase value as it is immediately after the scene change detection unit 61 detects a scene change at time t10, and then visually At a time t11, the value becomes “0”. Immediately after the scene change detection unit 61 detects a scene change at time t20, the temporary increase value is output as it is, and then gradually attenuated at a speed that is not visually noticeable. When a scene change is detected at time t30 before the value becomes “0”, immediately after that, the temporarily increased value is output as it is, and at time t31, the value becomes “0”. Here, the temporary increase value is described as being attenuated at a constant speed, but may be attenuated exponentially.

  Then, the luminance magnification calculation unit 53 adds the basic luminance magnification shown in FIG. 10B and the temporary luminance magnification shown by the solid line in FIG. 10C to obtain the total luminance magnification shown in FIG. Output as.

  In this way, the basic luminance magnification is determined by APL. In addition, if there is a scene change, the temporary luminance magnification is added and the luminance magnification temporarily rises, so that a bright image display can be felt each time the scene changes. Visually, it is recognized as a powerful image with high brightness. After that, the brightness gradually decreases at a speed that is not visually noticeable, so the increase in power accompanying the scene change is also temporary.

  Next, the operation when the temperature T detected by the temperature sensor 47 is higher than the temperature T11 and the temporary increase value limiting unit 66 limits the upper limit of the temporary increase value will be described.

  FIG. 11 is a diagram for explaining the operation of the temporary increase value limiting unit 66 in the embodiment of the present invention. However, FIG. 11 (a) is the same diagram as FIG. 10 (c), and the temporary rise value and the temporary luminance magnification when the temperature T is lower than the temperature T11 are indicated by a broken line and a solid line, respectively. FIG. 11B shows a temporary increase value and a temporary luminance magnification when the temperature T is higher than the temperature T11 and lower than the temperature T12, and FIG. 11C shows a temporary increase value and a temporary luminance when the temperature T is higher than the temperature T12. The luminance magnification is shown.

  When the temperature T is lower than the temperature T11, the temporary increase value limiting unit 66 limits the temporary increase value so as not to exceed the upper limit value K1. However, in the present embodiment, the upper limit value K1 is set to a value equal to the maximum value of the temporary increase value, so that the upper limit value K1 is not practically limited, and as shown in FIG. The limiting unit 66 outputs the input temporary increase value as it is.

  When the temperature T becomes higher than the temperature T11, as shown in FIG. 11B, the temporary increase value limiting unit 66 limits the temporary increase value so as not to exceed the upper limit value K (T). When the temporary increase value is limited, the temporary luminance magnification is also limited, so that the temporary power associated with the scene change is also limited. Since the upper limit K (T) of the temporary increase value decreases as the temperature T increases, the temporary power associated with the scene change also decreases.

  When the temperature T becomes higher than the temperature T12, the upper limit value K (T) of the temporary increase value becomes equal to a certain upper limit value K2. Here, if the upper limit K2 is set to a finite value other than “0”, the temporary luminance magnification does not become “0” but takes a finite value. Even if it exists, the fall of image display quality, such as being visually recognized as an image whose brightness | luminance is lower than actual display brightness | luminance, can be relieved.

  In the present embodiment, temperature T11 = 50 ° C., temperature T12 = 70 ° C., upper limit value K1 = 1 times, and upper limit value K2 = 0.2 times. However, the present invention is not limited to this value, and it is desirable to set as appropriate according to the characteristics of the panel, the specifications of the plasma display device, and the like.

  Next, an operation when the temperature T detected by the temperature sensor 47 is higher than the temperature T12 and the luminance magnification limiting unit 54 limits the upper limit of the total luminance magnification will be described.

  FIG. 12 is a diagram for explaining the operation of the luminance magnification limiting unit 54 according to the embodiment of the present invention. However, FIG. 12A is the same diagram as FIG. 10D and shows the luminance magnification when the temperature T is lower than the temperature T21. FIG. 12B shows the luminance magnification when the temperature T is higher than the temperature T21 and lower than the temperature T22, and FIG. 12C shows the luminance magnification when the temperature T is higher than the temperature T22.

  When the temperature T is lower than the temperature T21, the luminance magnification limiting unit 54 restricts the luminance magnification so as not to exceed the upper limit value H1. However, in the present embodiment, the upper limit value H1 is set to a value equal to the maximum value of the total luminance magnification, so that the upper limit value H1 is not practically limited. As shown in FIG. The limiting unit 54 outputs the input total luminance magnification as it is.

  When the temperature T becomes higher than the temperature T21, as shown in FIG. 12B, the luminance magnification limiting unit 54 limits the luminance magnification so as not to exceed the upper limit value H (T). When the luminance magnification is limited, the number of sustain pulses is limited, so that the power associated with image display is limited, and the temperature rise inside the housing is suppressed.

  When the temperature T becomes higher than the temperature T22, the luminance magnification limiting unit 54 decreases the upper limit value H of the total luminance magnification by a predetermined value. If the temperature T does not decrease after a predetermined time, the upper limit value H is further decreased by a predetermined value. This operation is repeated as long as the temperature T is higher than the temperature T22 and the temperature does not decrease. When the temperature T becomes lower than the temperature T22, the upper limit value H of the total luminance magnification is increased by a predetermined value. This operation is repeated until the upper limit value H of the total luminance magnification returns to the upper limit value H (T) shown in FIG. In this way, the luminance magnification limiting unit 54 controls the maximum value of the luminance magnification by feedback control so that the temperature inside the housing does not become higher than the temperature T22.

  In the present embodiment, temperature T21 = 50 ° C., temperature T22 = 70 ° C., and upper limit value H1 = 4.5 times. However, the present invention is not limited to this value, and it is desirable to set as appropriate according to the characteristics of the panel, the specifications of the plasma display device, and the like.

  In the present embodiment, the luminance magnification limiting unit 54 has been described as limiting the total luminance magnification that is the output of the luminance magnification calculating unit 53. However, the present invention is not limited to this, for example, a basic magnification setting. The basic luminance magnification that is the output of the unit 52 may be limited.

  In the present embodiment, the temporary increase value limiting unit 66 has been described as limiting the temporary increase value that is the output of the temporary increase value calculation unit 65. However, the present invention is not limited to this, for example, The structure which restrict | limits the output of the temporary raise value attenuation | damping part 67 may be sufficient.

  Furthermore, the specific numerical values used in the present embodiment are merely examples, and it is desirable to set them appropriately to 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 characteristic of the temporary magnification setting part in embodiment of this invention The figure which shows the characteristic of the temporary rise value restriction | limiting part in embodiment of this invention The figure which shows the characteristic of the brightness | luminance magnification limiting part in embodiment of this invention The figure for demonstrating operation | movement of the luminance magnification setting circuit in embodiment of this invention The figure for demonstrating operation | movement of the temporary raise value restriction | limiting part in embodiment of this invention. The figure for demonstrating operation | movement of the brightness | luminance magnification limiting part 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 calculating unit 54 Luminance magnification limiting unit 61 Scene change detection unit 62 Temporary magnification setting unit 65 Temporary increase value calculation unit 66 Temporary increase value limitation unit 67 Temporary increase value attenuation unit 100 Plasma display device

Claims (3)

A plasma display panel having a plurality of discharge cells having display electrode pairs, a temperature sensor for detecting the temperature inside the apparatus, an address period for selectively generating an address discharge in the discharge cells, and a luminance weight A plasma display apparatus that displays an image using a plurality of subfields having a sustain period in which a sustain discharge is generated in a discharge cell in which an address discharge is generated by applying a number of sustain pulses multiplied by a luminance magnification to the display electrode pair Because
A scene change detection unit for detecting an image scene change based on the image signal;
A temporary magnification setting unit that temporarily increases the luminance magnification when the scene change detection unit detects a scene change and restricts the upper limit value based on the temperature detected by the temperature sensor; Plasma display device. The temporary magnification setting unit includes a temporary increase value calculation unit that calculates a temporary increase value of a luminance magnification that is temporarily increased based on the APL of the image signal, and an upper limit of the temporary increase value based on the temperature detected by the temperature sensor. A temporary increase value limiting unit for limiting a value, and a temporary increase value attenuation unit for attenuating a temporary increase value whose upper limit value is limited after the scene change detection unit detects a scene change. The plasma display device according to claim 1. A basic magnification setting unit for setting a basic luminance magnification based on the APL of the image signal;
2. A luminance magnification calculation unit that calculates the luminance magnification based on the basic luminance magnification set by the basic magnification setting unit and the temporary luminance magnification set by the temporary magnification setting unit. Or the plasma display apparatus of Claim 2.

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