JP2007133289A - Plasma display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To control power consumption which can be set to an emitted light quantity of discharge cells, in matching with the user's preference. <P>SOLUTION: In a plasma display device 100, one field period of an image signal is constituted of two or more sub-fields with a write-in period and a sustaining period; in the sustaining period, an image is displayed by applying to a scan electrode and a sustain electrode sustaining pulses of the number obtained by multiplying the luminance weight set for each sub-field by a proportionality coefficient, to generate sustaining discharges; and the plasma display device 100 is so configured to output a power prediction signal, based on APL of an image signal, and also to output the proportionality coefficient by the power prediction signal, and is further configured to enable changing the relation between the power prediction signal and the proportionality coefficient. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a plasma display device using a plasma display panel.

The plasma display device is a display device that displays an image by discharging and emitting light from each discharge cell using a plasma display panel including a large number of discharge cells. Therefore, the number of discharge cells that should emit light increases, and the power consumption increases as the amount of light emission per discharge cell increases. However, on the other hand, low power consumption of the plasma display device is demanded. Therefore, a method has been proposed in which even if the number of discharge cells to emit light increases, the amount of light emitted from the discharge cells is adjusted so that the power consumption does not become too large. For example, in Patent Document 1, based on an input image signal, means for obtaining a power prediction signal for predicting power consumption when an image is displayed as it is, and the light emission amount of a discharge cell is controlled according to the power prediction signal. There is disclosed a plasma display device that includes a control means and suppresses power consumption to be substantially constant.
Japanese Patent Laid-Open No. 2001-22318

  If the power consumption is suppressed in this way, the light emission amount, that is, the luminance at the time of image display is naturally limited. However, with the spread of plasma display devices, user demands have also diversified, and there has been a demand to display images according to user preferences while controlling power consumption.

  The present invention has been made in view of these demands, and provides a plasma display device capable of controlling the power consumption that can be set to the light emission amount of the discharge cell according to the user's preference using a relatively simple circuit. For the purpose.

  In the present invention, one field period of an image signal is composed of a plurality of subfields having an address period and a sustain period. In the address period, a scan pulse is applied to the scan electrode and a write pulse is selectively applied to the data electrode. Then, an address discharge is selectively generated in the discharge cells, and in the sustain period, sustain pulses of the number obtained by multiplying the luminance weight set for each subfield by a proportional coefficient are applied to the scan electrodes and the sustain electrodes, and the sustain discharge is performed. Is a plasma display device that generates an image and displays a power prediction signal based on the APL of the image signal, and is configured to output a proportional coefficient based on the power prediction signal, and is proportional to the power prediction signal It is characterized in that the relationship with the coefficient can be changed. With this configuration, it is possible to provide a plasma display device capable of controlling power consumption that can be set to the light emission amount of the discharge cell according to the user's preference using a relatively simple circuit.

  In the present invention, one field period of an image signal is composed of a plurality of subfields having an address period and a sustain period, and in the address period, a scan pulse is applied to the scan electrode and an address pulse is selectively applied to the data electrode. Then, an address discharge is selectively generated in the discharge cells, and a sustain discharge is generated by applying a number of sustain pulses to the scan electrodes and sustain electrodes, which is obtained by multiplying the luminance weight set for each subfield by a proportional coefficient during the sustain period. A power display that outputs a power prediction signal based on the APL of the image signal, a proportional coefficient generation unit that receives the power prediction signal and outputs a proportional coefficient, and a luminance weight Multiply the proportionality coefficient to determine the number of sustain pulses in each sustain period of the subfield, and input data to the proportionality coefficient generator That a data input unit, the proportional coefficient generating unit, the relationship between the power prediction signal proportional coefficient, may be changed based on the input data from the data input unit. With this configuration, it is possible to provide a plasma display device capable of controlling power consumption that can be set to the light emission amount of the discharge cell according to the user's preference using a relatively simple circuit.

  Moreover, as for the proportionality coefficient of the plasma display apparatus of this invention, it is desirable that the maximum value which can be set is predetermined with respect to the electric power prediction signal. With this configuration, it is possible to control so that power consumption accompanying discharge does not become too large.

  Further, the proportionality coefficient of the plasma display device of the present invention may be set to be inversely proportional to the power prediction signal. With this configuration, the initial setting can be made so that the power consumption accompanying the discharge becomes constant.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the plasma display apparatus which can control the power consumption which can be set to the light emission amount of the discharge cell according to a user's liking using a comparatively simple circuit.

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

(Embodiment 1)
FIG. 1 is an exploded perspective view showing the structure of a plasma display panel (hereinafter abbreviated as “panel”) used in the plasma display device in accordance with the exemplary embodiment of the present invention. The panel 10 is configured such that a glass front substrate 21 and a rear substrate 31 are arranged to face each other and a large number of discharge cells are formed therebetween. On the front substrate 21, a plurality of scanning electrodes 22 and sustaining electrodes 23 constituting a display electrode pair are formed in parallel with each other. A dielectric layer 24 is formed so as to cover the scan electrodes 22 and the sustain electrodes 23, and a protective layer 25 is formed on the dielectric layer 24. A plurality of data electrodes 32 covered with an insulating layer 33 are provided on the back substrate 31, and a grid-like partition wall 34 is provided on the insulating layer 33. A phosphor layer 35 is provided on the surface of the insulator layer 33 and the side surfaces of the partition walls 34. The front substrate 21 and the rear substrate 31 are arranged to face each other so that the scan electrode 22, the sustain electrode 23, and the data electrode 32 intersect, and a discharge cell is formed at each position where the electrodes intersect. For example, a mixed gas of neon and xenon is sealed in the discharge cell as a discharge gas. Note that the structure of the panel is not limited to that described above, and for example, a panel having a stripe-shaped partition instead of a cross-shaped partition may be used.

  Next, a method for driving the panel will be described. In the present embodiment, a so-called subfield method is used as a method for displaying a gradation corresponding to an image signal. The subfield method is a method in which one field period is divided into a plurality of subfields having different display luminances, and gradation is displayed by combining these subfields. Here, the ratio of display luminance for each subfield is hereinafter referred to as “luminance weight”.

  For the purpose of explanation, one field period is divided into 8 subfields (SF1, SF2,..., SF8), and each subfield is composed of (1, 2, 4, 8, 16, 32, 64, 128). If it has a luminance weight, 256 gradation levels from “0” to “255” can be displayed by combining the subfields to emit light. For example, gradation “7” is obtained by causing discharge cells to emit light in subfields SF1, SF2, and SF3 having luminance weights 1, 2, and 4, and gradation “21” is a subfield having luminance weights 1, 4, and 16. Each field can be displayed by causing the discharge cells to emit light in the fields SF1, SF3, and SF5.

  Each subfield has an initialization period, an address period, and a sustain period. FIG. 2 is a diagram showing drive voltage waveforms applied to the respective electrodes of the panel used in the embodiment of the present invention. FIG. 2 shows drive voltage waveforms for two subfields, but in other subfields. The drive waveforms are substantially the same except for the number of sustain pulses described later.

  In the initializing period of the subfield, as shown by SF1 in FIG. 2, a ramp voltage that gradually increases and a ramp voltage that gradually decreases are applied to the scan electrode 22. Alternatively, as shown by SF2 in the figure, when a ramp voltage that gradually falls is applied, a weak initializing discharge is caused in the discharge cells, and wall charges necessary for the subsequent address operation are formed on each electrode.

  In the subsequent address period, a negative scan pulse Va is applied to one of the scan electrodes 22, and a positive address pulse Vd is applied to the data electrode 32 corresponding to the discharge cell to emit light. Then, an address discharge occurs in the discharge cells to which the scan pulse Va and the address pulse Vd are simultaneously applied, and an address operation for accumulating wall charges in the scan electrode 22 and the sustain electrode 23 is performed. By performing the above address operation in all the discharge cells that should emit light, an address discharge is selectively generated in the discharge cells that should emit light, thereby forming wall charges.

  In the subsequent sustain period, first, positive sustain pulse Vs is applied to scan electrode 22. Then, in the discharge cell in which the address discharge has occurred, a sustain discharge occurs between the scan electrode 22 and the sustain electrode 23 to emit light. Next, sustain pulse Vs is applied to sustain electrode 23. Then, in the discharge cell in which the sustain discharge has occurred, the sustain discharge occurs again to emit light. Similarly, when sustain pulses are alternately applied to the scan electrode 22 and the sustain electrode 23, a sustain discharge is generated and light is emitted in each discharge cell in which the sustain discharge has occurred. Therefore, the luminance of the discharge cells that emit light increases in proportion to the number of discharge cells that have caused the address discharge and in proportion to the number of sustain pulses applied to the scan electrode 22 and the sustain electrode 23, and the power consumption associated with the discharge increases. P also increases. The number of sustain pulses is proportional to the luminance weight of the subfield, and the power consumption P is controlled as described below by controlling the proportional coefficient k.

  Next, the concept for reducing the power consumption P accompanying discharge will be described. As described above, in order to display gradation, it is necessary to generate a sustain pulse proportional to the luminance weight of each subfield in the sustain period of each subfield. At this time, by controlling the proportional coefficient k, The power consumption P can be controlled. That is, when the proportional coefficient k is increased, the number of sustain pulses in each subfield increases, so that the luminance of the entire screen increases and the power consumption P also increases. Conversely, if the proportionality coefficient k is reduced, the number of sustain pulses in each subfield is reduced, the luminance is reduced, but the power consumption P can be reduced.

  FIG. 3 is a diagram showing the relationship between the luminance weight of each subfield and the number of sustain pulses when the proportionality coefficient k is set to 1, 2 and 3 times. As described above, since the number of sustain pulses increases as the proportional coefficient k increases, it is apparent that the luminance is high and the power consumption P is also increased. Therefore, in order to suppress the power consumption of the plasma display device, the proportional coefficient k is set low when displaying an image signal that emits many discharge cells in a subfield having a high APL (Average Picture Level) and a large luminance weight, On the other hand, when displaying an image signal in which the discharge cells hardly emit light in a subfield having a low APL and a large luminance weight, the proportionality coefficient k may be set large. FIG. 3 shows only the relationship between the luminance weight and the number of sustain pulses when the proportional coefficient k is an integer for illustration, but the proportional coefficient k does not have to be an integer, for example, k = 1. It can be set freely in the range of positive real numbers such as 2 and k = 3.96. As a result, when the number of sustain pulses is not an integer, the number of sustain pulses may be determined by rounding off. Display errors caused by rounding errors such as rounding off can be eliminated by using signal processing such as error diffusion together.

  FIG. 4 is a circuit block diagram of the plasma display device in accordance with the exemplary embodiment of the present invention. The plasma display apparatus 100 includes a power prediction unit 110 that detects the sum of APLs of R, G, and B color image signals as a power prediction signal z, indicating power consumption when power consumption control is not performed, and power prediction. A proportional coefficient generation unit 120 for generating a proportional coefficient k based on the signal z and in accordance with user preference, a subfield conversion unit 140 for converting an image signal into a subfield signal indicating light emission / non-light emission for each subfield, luminance An electrode driver 150 is provided that multiplies the weight by a proportional coefficient k to determine the number of sustain pulses and applies a drive voltage waveform to each electrode.

  The power prediction unit 110 includes APL detection circuits 111, 112, and 113 that detect respective APLs of R, G, and B color image signals, and an addition circuit 114. Each of the APL detection circuits 111, 112, and 113 detects, for example, the APL of each of the R, G, and B image signals by integrating the corresponding color image signals. The adder circuit 114 adds these APLs and outputs the result as a power prediction signal z.

  The proportional coefficient generation unit 120 includes a lookup table (hereinafter abbreviated as “LUT”) 121 that receives the power prediction signal z and outputs a proportional coefficient k (z) as a function of the power prediction signal z. The LUT 121 can be composed of a RAM or the like, and further includes an LUT setting circuit 122 for rewriting the contents according to the user's request. Data for rewriting the LUT 121 is input through a data input unit 190 such as an interface.

  As described above, the subfield conversion unit 140 converts the R, G, and B image signals into signals indicating light emission and no light emission for each subfield. This circuit can also be constituted by a conversion table using, for example, a ROM.

  The electrode driving unit 150 includes a timing generation circuit 151, a scan electrode driving circuit 155, a sustain electrode driving circuit 156, and a data electrode driving circuit 159. The timing generation circuit 151 determines the number of sustain pulses in each subfield by multiplying the luminance weight of each subfield by the proportional coefficient output from the proportional coefficient generation unit 120, and creates a drive voltage waveform to be applied to each electrode. A timing pulse is generated. Scan electrode drive circuit 155 and sustain electrode drive circuit 156 apply drive voltage waveforms to the respective electrodes in accordance with timing pulses of timing generation circuit 151. Data electrode driving circuit 159 receives a subfield signal, generates an address pulse corresponding to each data electrode in accordance with the timing pulse of timing generation circuit 151, and applies it to each data electrode.

  FIG. 5 is a diagram showing the relationship between the power prediction signal z and the proportionality coefficient k (z). FIG. 5A shows that the power consumption P (z) accompanying the discharge becomes constant as a function of the power prediction signal z. FIG. 5B and FIG. 5C show an example in which the control method of the power consumption P (z) is changed according to the user's preference. In the present embodiment, the power prediction signal z takes an arbitrary value of 0 ≦ z ≦ 3, and the proportional coefficient k (z) takes an arbitrary value of 0 <k (z) ≦ 5. Will be described.

As shown in FIG. 5A, when the control is performed so that the power consumption P (z) is constant, the proportional coefficient k (z) is set so as to be inversely proportional to the power prediction signal z. Then, the power consumption P (z) accompanying the discharge is proportional to the product of the power prediction signal z and the proportional coefficient k (z).
P (z) = k (z) × z = CC: constant, and power consumption P (z) is kept constant. However, since k (z) ≦ 5, the power consumption P (z) is proportional to the power prediction signal z in a dark image.

FIG. 5B is an example in which the power control is performed more moderately, that is, while the power consumption P (z) accompanying discharge increases with the increase of the power prediction signal z. Also in this case, for the desired power consumption P (z),
k (z) ∝P (z) / z
The proportional coefficient k (z) may be set so that When the power control as shown in FIG. 5B is performed, an image with a low APL is dark and an image with a high APL is brightly displayed, so that a powerful dynamic image can be obtained.

  FIG. 5C shows an example in which power control is performed while the power consumption P (z) accompanying the discharge decreases as the power prediction signal z increases. Further, in FIG. 5C, the value of the proportional coefficient k (z) is set with respect to a specific value of the power prediction signal z, and the value is set in a complementary manner. In this way, the proportional coefficient k (z) is not set for all the values of the power prediction signal z, but is set for several values, and even if it is complemented between them, it is a sufficient setting for practical use. A degree of freedom is obtained. Note that when power control as shown in FIG. 5C is performed, an image with a low APL is displayed brightly, which is suitable for image display such as a movie.

  As described above, the plasma display device according to the present embodiment can change the relationship between the power prediction signal and the proportionality coefficient according to the user's preference, but consumes power so that the power consumption associated with the discharge does not become too large. Control is performed so that the electric power P (z) is set to the maximum value Pmax (z) or less. Further, as shown in FIG. 5A, as the initial set value, the proportional coefficient k (z) is set to be inversely proportional to the power prediction signal z within a range not exceeding the maximum value that can be set. The initial setting is such that the power P (z) is constant.

  Next, a method for controlling power consumption of the plasma display device according to the present embodiment will be described. In the present embodiment, as shown in FIG. 5 (c), power consumption P (z) is set for several values of the power prediction signal z and linear interpolation is performed between them. Further, as an initial setting of the LUT 121, it is assumed that the proportional coefficient k (z) is set such that the power consumption is constant as shown in FIG.

  FIG. 6 is a flowchart showing a method for controlling power consumption of the plasma display device according to the present embodiment. First, the power consumption P (z) whose setting is to be changed and the power prediction signal z at that time are input from the data input unit 190 (S11). The process returns to step S11 and continues to be input until the necessary input is completed (S12). When the input is completed (S12), the values of the power consumption P (z) are rearranged in the order of the power prediction signal z, and the power interpolation P (z) is obtained as a function of a polygonal line by interpolating between them. At this time, if the power consumption P (z) exceeds the maximum allowable power value Pmax (z), the power consumption P (z) is limited to P (z) = Pmax (z) (S13). Next, the power consumption P (z) is divided by the power prediction signal z to obtain the proportional coefficient k (z). At this time, when the proportional coefficient k (z) exceeds the maximum value kmax of the proportional coefficient, which is “5” in the present embodiment, it is limited so that k (z) = kmax (S14). Then, the LUT setting circuit 122 writes the proportional coefficient k (z) thus obtained in the LUT 121 (S15). This completes the setting change.

  In this way, the plasma display device of the present embodiment is configured to output a power prediction signal based on the APL of the image signal, and to output a proportionality coefficient based on the power prediction signal, and is proportional to the power prediction signal. Since the relationship with the coefficient can be changed, it is possible to set the light emission amount of the discharge cell to the user's preference using a relatively simple circuit while suppressing the power consumption associated with the discharge.

  In the present embodiment, one field period is divided into eight subfields (SF1, SF2,..., SF8), and each subfield is (1, 2, 4, 8, 16, 32, 64). However, the present invention is not limited to this subfield configuration. In order to use pseudo contour correction together, it is desirable to have a configuration with a large number of subfields. For example, one field is divided into 10 subfields (SF1, SF2,..., SF10), and the luminance of each subfield is determined. The weights may be (1, 2, 3, 6, 11, 18, 30, 44, 60, 80), respectively.

  In the present embodiment, the subfield configuration is described as not depending on the proportional coefficient k (z). However, when the number of sustain pulses is determined by rounding off the number of sustain pulses, the rounding error is corrected. Therefore, the subfield configuration may be switched depending on the proportional coefficient k (z).

  The plasma display device of the present invention can control the power consumption that can be set to the light emission amount of the discharge cell according to the user's preference using a relatively simple circuit, and is useful as an image display device.

1 is an exploded perspective view showing a structure of a panel used in a plasma display device according to an embodiment of the present invention. The figure which shows the drive voltage waveform impressed to each electrode of the panel The figure which shows the relationship between the proportionality coefficient in the embodiment of this invention, the luminance weight of each subfield, and the number of sustain pulses Circuit block diagram of plasma display device in accordance with exemplary embodiment of the present invention The figure which shows the relationship between the electric power prediction signal z and proportionality coefficient k (z) in embodiment of this invention. The flowchart which shows the control method of the power consumption of the plasma display apparatus in this Embodiment

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Panel 22 Scan electrode 23 Sustain electrode 32 Data electrode 100 Plasma display apparatus 110 Power prediction part 120 Proportional coefficient generation part 140 Subfield conversion part 150 Electrode drive part 151 Timing generation circuit 155 Scan electrode drive circuit 156 Sustain electrode drive circuit 159 Data electrode Drive circuit 190 Data input section

Claims (4)

One field period of the image signal is composed of a plurality of subfields having an address period and a sustain period. In the address period, a scan pulse is applied to the scan electrode and a write pulse is selectively applied to the data electrode. The address discharge is selectively generated in the discharge cells, and in the sustain period, a number of sustain pulses obtained by multiplying the luminance weight set for each subfield by a proportional coefficient is applied to the scan electrode and the sustain electrode, A plasma display device that displays an image by generating a sustain discharge, configured to output a power prediction signal based on an APL of an image signal, and to output the proportionality coefficient based on the power prediction signal, and the power A plasma display device characterized in that the relationship between a prediction signal and the proportionality coefficient can be changed. One field period of the image signal is composed of a plurality of subfields having an address period and a sustain period. In the address period, a scan pulse is applied to the scan electrode and a write pulse is selectively applied to the data electrode. An address discharge is selectively generated in the discharge cells. In the sustain period, a number of sustain pulses obtained by multiplying the luminance weight set for each subfield by a proportional coefficient is applied to the scan electrode and the sustain electrode. A plasma display device for displaying an image by generating a sustain discharge,
A power prediction unit that outputs a power prediction signal based on the APL of the image signal;
A proportional coefficient generation unit that inputs the power prediction signal and outputs the proportional coefficient;
An electrode driver that multiplies the luminance weight by the proportionality factor to determine the number of sustain pulses in the sustain period of each of the subfields;
A data input unit for inputting data to the proportional coefficient generation unit;
The plasma display apparatus characterized in that the proportional coefficient generation unit can change a relationship between the power prediction signal and the proportional coefficient based on data input from the data input unit. 3. The plasma display apparatus according to claim 1, wherein a maximum value that can be set for the proportionality coefficient is predetermined with respect to a power prediction signal. 4. The plasma display apparatus according to claim 3, wherein the proportionality coefficient is set to be inversely proportional to the power prediction signal.

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