JP4528449B2 - Driving method and display device of plasma display panel - Google Patents

Description

The present invention relates to a method for driving a plasma display panel (PDP).
[0001]
The PDP is a digital display device composed of binary light emitting cells and is suitable for displaying digital data, and thus has attracted attention as a multimedia monitor. Development of a driving method capable of brighter and multi-gradation display is underway for expanding the application of PDP.
[0002]
[Prior art]
In the display using the AC type PDP, addressing is performed so that an appropriate amount of wall charges exists only in the cells to be lit among the cells arranged in a matrix, and then the display discharge is performed a number of times according to the luminance using the wall charges. The lighting that is generated is maintained. In both the addressing and the lighting maintenance, the pulse width of the pulse to be applied needs to be longer than the discharge delay time (the time from the leading edge of the pulse to the discharge start time). The discharge delay time depends on the environmental temperature. The lower the temperature, the longer the discharge delay time.
[0003]
Conventionally, the pulse width is set based on the lower limit value (for example, 0 ° C.) of the operating temperature range in the specification. That is, the pulse width is selected to be a sufficiently long value so that a desired discharge occurs even under the lowest temperature condition.
[0004]
[Problems to be solved by the invention]
Since the required time for addressing is proportional to the number of rows on the display surface (vertical resolution), the period that can be allocated for display discharge in the frame period becomes shorter as the resolution increases. In addition, the number of frames that can be divided for gradation display is reduced. In order to increase luminance by increasing the number of display discharges or increase gradation by increasing the number of frame divisions, it is desirable to shorten the time required for addressing as much as possible.
[0005]
In the conventional driving method, the pulse width is longer than necessary in the operation at a general environmental temperature that is near the center of the operating temperature range and higher, thereby limiting the increase in brightness and multi-gradation. It was. In addition, since the addressing period is long, there is a problem that the probability of erroneous discharge occurring in a non-selected row is high.
[0006]
An object of the present invention is to realize a high-quality and stable display by effectively using a frame period.
[0007]
[Means for Solving the Problems]
In the present invention, the pulse width of the drive voltage pulse is changed in accordance with the temperature change of the panel surface corresponding to the cell. When the panel surface temperature is relatively low, the pulse width is lengthened, and when the temperature is high, the pulse width is shortened. For example, the operation temperature range is divided into two, and the pulse width is switched depending on whether the panel surface temperature is a low temperature range below the threshold value or a high temperature range exceeding the threshold value. If two or more threshold values are set and multistage switching is performed, the pulse width can be optimized more precisely. It is also possible to continuously change the pulse width following the temperature change. The change of the pulse width can be performed for pulses in any of the processes of addressing, lighting maintenance, and preparation for addressing (charge initialization).
[0008]
By shortening the pulse width, the period allocated to the application of the pulse can be shortened. For example, if the width of a pulse for selecting a row in addressing is shortened, the time can be shortened by the number of rows corresponding to the shortening of each pulse width for one addressing. Specifically, when the maximum delay time of the address discharge at 0 ° C. is 2.0 μs and the maximum delay time at 25 ° C. is 1.0 μs, the shortened amount per pulse is 1.0 μs. In a PDP with 480 rows of VGA specifications, if one frame is divided into 10 subframes and gradation display is performed, the total reduction time is 4.8 ms (= 1.0 μs × 480 × 10). Become. This value is about 28.7% of the frame period (about 16.7 ms). Note that, in the case of interlaced display, when a field constituting a frame is divided into a plurality of subfields, the time can be similarly reduced.
[0009]
If the shortened time is assigned to maintaining the lighting, the number of display discharges can be increased to increase the luminance. The reliability of display discharge may be increased by increasing the pulse width in maintaining the lighting. If the number of subframes is increased, it is possible to diversify the light emission distribution that is effective for improving gradation and preventing false contours. If assigned to addressing preparation, more reliable initialization processing can be performed. Further, when the addressing is shortened, the half-selected period is shortened, so that erroneous discharge can be prevented and the display can be stabilized. Furthermore, by providing a period during which the application of voltage is stopped to calm the charge in the discharge space, erroneous discharge can be prevented and display can be stabilized.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
[Outline of device configuration and drive]
FIG. 1 is a configuration diagram of a display device according to the present invention. The display device 100 includes a surface discharge type PDP 1 having a display surface capable of color display composed of m × n cells, a drive unit 70 that controls light emission of the cells, and a sensor 90 that detects a panel surface temperature. ing. The controller 71 incorporated in the drive unit 70 changes the pulse width of the drive voltage pulse applied to the cell according to the output of the sensor 90. Note that the application of a pulse means that the electrode is temporarily biased to a predetermined potential.
[0011]
In order to generate a desired discharge in all the cells, the pulse width must be longer than the discharge delay time in the cell having the lowest temperature. Therefore, the temperature monitoring by the sensor 90 is performed on a portion of the display surface where the temperature tends to be relatively low. It is desirable to directly measure the temperature inside the cell related to the discharge characteristics such as the electron ion temperature, the MgO film surface temperature, and the phosphor temperature, but the sensor 90 is disposed at a position away from the cell to indirectly control the temperature. You may measure. It is also possible to estimate the cell temperature based on a function of the rear chassis temperature, drive circuit element temperature, time since power-on, display load factor and time. Since the temperature distribution on the display surface depends on the display content, the cells to be lit may concentrate on a part of the display surface and locally rise in temperature. Measuring the temperature at multiple locations increases the reliability of the measurement.
[0012]
FIG. 2 is a diagram showing an electrode arrangement of the PDP. In PDP 1, display electrodes X and Y constituting an electrode pair for generating display discharge are arranged in parallel, and address electrodes A are arranged so as to intersect these display electrodes X and Y. The display electrodes X and Y extend in the row direction (horizontal direction) of the matrix display, and the address electrodes extend in the column direction (vertical direction). In the figure, the suffixes of the reference symbols of the display electrodes X and Y and the address electrode A indicate the arrangement order. The potentials of the display electrodes X and Y are controlled by the X driver 74 and the Y driver 77, and the potential of the address electrode A is controlled by the A driver 80.
[0013]
FIG. 3 is a diagram showing a cell structure of the PDP. The PDP 1 includes a pair of substrate structures (structures in which cell components are provided on a substrate) 10 and 20. Each of the display electrodes X and Y arranged on the inner surface of the front glass substrate 11 includes a transparent conductive film 41 forming a surface discharge gap and a metal film (bus electrode) 42 extending over the entire length of the row. A dielectric layer 17 is provided so as to cover the display electrode pairs X and Y, and magnesia (MgO) is deposited as a protective film 18 on the surface of the dielectric layer 17. On the inner surface of the glass substrate 21 on the back side, one address electrode A is arranged in a row, and a plurality of partition walls 29 in a plan view are formed on the dielectric layer 24 covering these address electrodes A. ing. These partition walls 29 divide the discharge space for each column in the row direction. Then, phosphor layers 28R, 28G, and 28B of three colors of R, G, and B for color display are provided so as to cover the side surfaces of the address electrodes A and the partition walls 29. Italic alphabets R, G, B in the figure indicate the emission color of the phosphor. The phosphor layers 28R, 28G, and 28B are locally excited by the ultraviolet rays emitted by the discharge gas and emit light.
[0014]
FIG. 4 is a conceptual diagram of field division. In displaying a television image by the PDP 1, in order to perform color reproduction by selecting a combination of lighting / non-lighting, a time series field f as an input image is divided into a predetermined number q of subfields sf. That is, each field f is replaced with a set of q subfields sf. Luminance weights U ₁ , U ₂ , U ₃ ,... U _q are sequentially assigned to these subfields sf to set the number of display discharges in each subfield sf. In the figure, the subfield arrangement is in the order of weights, but other orders may be used. A field period Tf, which is a field transfer period, is divided into q subfield periods Tsf in accordance with such a field configuration, and one subfield period Tsf is assigned to each subfield SF. Further, the subfield period Tsf is divided into a reset period TR for initialization, an address period TA for addressing, and a display period TS for maintaining lighting. While the length of the reset period TR and the address period TA does not depend on the weight, the length of the display period TS is longer as the weight is larger. Therefore, the length of the subfield period Tsf is longer as the weight of the corresponding subfield sf is larger.
[0015]
FIG. 5 is a voltage waveform diagram showing an outline of the drive sequence. The order of the reset period TR, the address period TA, and the display period TS is common in q subfields sf, and the drive sequence is repeated for each subfield. Note that the amplitude, polarity, and timing of the waveform can be variously changed. The erasure address format is not limited to the illustrated write address format.
[0016]
In the reset period TR, a positive pulse Pry1 and a negative pulse Pry2 are sequentially applied to all the display electrodes Y. Simultaneously with the application of the pulse Pry1, a negative pulse Prx is applied to all the display electrodes X, and then the display electrodes X are biased to a positive potential. A combined voltage obtained by adding the amplitudes of the pulses applied to the display electrodes X and Y is applied to the cell. The pulse Pry1 is applied in order to generate an appropriate wall voltage having the same polarity in all the cells regardless of lighting / non-lighting in the previous subfield. The wall voltage can be adjusted to a value corresponding to the difference between the discharge start voltage and the pulse amplitude by applying the pulse Pry2 to a cell in which an appropriate wall charge exists. Initialization (equalization of charge) in this example is to make the electric field state in all cells the same when an address voltage is applied.
[0017]
In the address period TA, wall charges necessary for maintaining lighting are formed only in the cells to be lit. In a state where all the display electrodes X and all the display electrodes Y are biased to a predetermined potential, a negative scan pulse Py is applied to one display electrode Y corresponding to the selected row every row selection period (scanning cycle). Simultaneously with the row selection by the application of the scan pulse Py, the address pulse Pa is applied only to the address electrode A corresponding to the selected cell in which the address discharge is to be generated. In the selected cell, a discharge is generated between the display electrode Y and the address electrode A, which is used as a trigger to generate a surface discharge between the display electrodes. These series of discharges are address discharges. Wall charges are formed in the dielectric layer 17 by the address discharge, and a wall voltage necessary for maintaining lighting is generated between the display electrodes.
[0018]
In the display period TS, the positive sustain pulse Ps1 is alternately applied to the display electrode Y and the display electrode X. By the first application to the display electrode Y, the cell voltage exceeds the discharge start voltage in the selected cell, and surface discharge between the display electrodes occurs. Since the wall charges having the opposite polarity to the previous one are formed by the surface discharge, the surface discharge occurs again in the selected cell by the application of the sustain pulse Ps to the display electrode X. Similarly, a surface discharge is generated in the selected cell every time the sustain pulse Ps is applied thereafter. In the display period TS, the address electrode A is biased to a potential having the same polarity as the sustain pulse Ps in order to prevent unnecessary discharge.
[0019]
In such a drive sequence, the pulse width of the pulse applied to cause discharge is changed in accordance with the panel surface temperature change.
[Pulse width switching]
FIG. 6 is a diagram showing a first example of changing the drive waveform. In the first example, the pulse width of the address pulse Pa is switched in two steps, and the number of times of applying the sustain pulse Ps is changed in accordance with the increase / decrease of the address period TA.
[0020]
When the panel surface temperature is lower than a preset threshold value, a scan pulse Py _L and an address pulse Pa _L having a relatively long pulse width W _L are applied. The length of the address period TA _L becomes greater than or equal to n times the pulse width W _L (n is the number of rows). In the figure, for convenience, the application period of the scan pulse Py _L is a pulse width W _L.
[0021]
On the other hand, when the panel surface temperature is high, a scan pulse Py _H and an address pulse Pa _H having a relatively short pulse width W _H are applied. The length of the address period TA _H, as compared with the address period TA _L when the temperature is low ΔT _{[= (W L -W H) ×} n ] only short. By assigning the shortened amount ΔT in sustaining, it is longer than the sustain period TS _L when the sustain period TS _H temperature is low. The luminance can be increased by applying more sustain pulses Ps as much as the length increases. In the figure, the hatched sustain pulse Ps is an additional portion.
[0022]
FIG. 7 is a diagram showing a second example of changing the drive waveform. In the second example, the pulse width of the address pulse Pa is switched in two steps, and according to the increase / decrease of the address period TA, any timing from the end of the lighting maintenance to the start of the addressing of the next subfield The length of the blank period (ΔT) in is changed. That is, the start timing of the sustain period TS is variable, when the panel surface temperature is high, for a time period from the end of the sustain period TS following drawing in the address period TA _H to the start of the reset period TR of the next subframe, the display electrodes X, Y and the address electrode A are kept at the ground potential. However, it is only necessary to substantially stop the voltage application to the cell, and the bias potential of each electrode can be selected within a range where there is no possibility of erroneous discharge. If the blank period is lengthened when the panel temperature is high, the space charge is calmed and subsequent erroneous discharge is less likely to occur. Further, the length of the reset period TR may be changed according to the increase / decrease of the address period TA. This makes it possible to perform more reliable initialization processing when the panel temperature is high.
[0023]
FIG. 8 is a diagram showing a third example of changing the drive waveform. In the third example, two stages of switching are performed for the pulse widths of the pulses Prx, Pry1, and Pry2 for initialization. When the panel surface temperature is low, pulses Prx _L , Pry1 _L and Pry2 _L having relatively long pulse widths W1 _L and W2 _L are applied. When the panel surface temperature is high, pulses Prx _H , Pry1 _H , Pry2 _H with relatively short pulse widths W1 _H and W2 _H are applied. And the time for the shortening by this is used effectively. That is, the brightness is increased by assigning it to maintain the lighting, the image quality is improved by increasing the number of subfields, or erroneous discharge is prevented by setting the blank period.
[0024]
FIG. 9 is a diagram showing a fourth example of changing the drive waveform. In the fourth example, two stages of switching are performed for the pulse width of the sustain pulse Ps. When the panel surface temperature is low, a sustain pulse Ps _L having a relatively long pulse width Ws _L is applied. When the panel surface temperature is high, a sustain pulse Ps _H having a relatively short pulse width Ws _H is applied. Since the pulse width Ws _H is short, the brightness can be increased by applying more sustain pulses Ps _H when the panel surface temperature is high than when the panel surface temperature is low. Image quality can be improved by increasing the number of subfields. It is also possible to assign a shortened time to the reset period TR and perform highly reliable initialization processing, thereby expanding the voltage margin for addressing and lighting maintenance.
[0025]
In the above first to fourth examples, the pulse width is changed by dividing the operating temperature range into two parts with the threshold Tth as a boundary as shown in FIG. It was a two-stage change in which the pulse width was switched depending on which value was in the high temperature range exceeding. If two or more threshold values Tth1 and Tth2 are set and switching is performed in multiple stages as shown in FIG. 10B, the pulse width can be optimized more precisely. Furthermore, as shown in FIG. 10C, the pulse width can be continuously changed by following the temperature change. Whether the tracking characteristic is non-linear or linear depends on the temperature dependence of the discharge characteristics.
[0026]
【The invention's effect】
According to the first to ninth aspects of the invention, it is possible to realize a high-quality and stable display by effectively using the frame period.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a display device according to the present invention.
FIG. 2 is a diagram showing an electrode arrangement of a PDP.
FIG. 3 is a diagram illustrating a cell structure of a PDP.
FIG. 4 is a conceptual diagram of field division.
FIG. 5 is a voltage waveform diagram showing an outline of a drive sequence.
FIG. 6 is a diagram illustrating a first example of changing a drive waveform.
FIG. 7 is a diagram showing a second example of changing a drive waveform.
FIG. 8 is a diagram illustrating a third example of changing a drive waveform.
FIG. 9 is a diagram showing a fourth example of changing a drive waveform.
FIG. 10 is a diagram showing a form of changing a pulse width.
[Explanation of symbols]
1 PDP (Plasma Display Panel)
ES display surface Py scan pulse Pa address pulse Ps sustain TA address period TS display period 90 sensors W _L, W _H pulse width Tth, Tth1, Tth2 threshold (set temperature)

Claims (16)

In a driving method of a plasma display panel that displays using a subfield having at least an address period,
When the temperature is the first temperature, an address pulse having a first width is applied to the address electrode in the address period, and a scan pulse having a width corresponding to the address pulse having the first width is applied to the display electrode. Applied,
When the temperature is a second temperature higher than the first temperature, an address pulse having a second width shorter than the first width is applied to the address electrode in the address period , and the second A driving method of a plasma display panel, wherein a scan pulse having a width corresponding to an address pulse having a width of 2 is applied to the display electrode . The driving method of the plasma display panel according to claim 1,
If the temperature is the first temperature, the length of the address period is the first length,
When the temperature is the second temperature, the driving method of the plasma display panel, wherein the length of the address period is a second length shorter than the first length . The method for driving a plasma display panel according to claim 1 or 2,
When the temperature is a third temperature higher than the second temperature, the width of the address pulse is set to a third width shorter than the second width, and the width of the scan pulse is set to the third width. A method for driving a plasma display panel, characterized in that the width corresponds to an address pulse . The method of driving a plasma display panel according to claim 3,
When the temperature is the first temperature, the width of the scan pulse is the first width,
When the temperature is the second temperature higher than the first temperature, the width of the scan pulse is a second width shorter than the first width,
The method of driving a plasma display panel , wherein when the temperature is a third temperature higher than the second temperature, the width of the scan pulse is a third width shorter than the second width . The method for driving a plasma display panel according to any one of claims 1 to 4,
A method for driving a plasma display panel, wherein a reset pulse including a positive pulse whose voltage value increases with the elapse of time is applied to the display electrode in a reset period . The method for driving a plasma display panel according to any one of claims 1 to 5,
A method for driving a plasma display panel, wherein a reset pulse including a negative pulse whose voltage value decreases with the passage of time is applied to the display electrode in a reset period . The method for driving a plasma display panel according to any one of claims 1 to 6,
A driving method of a plasma display panel , wherein an arrival potential of a scan pulse applied to the display electrode in an address period is lower than an arrival potential of a negative reset pulse applied to the display electrode in a reset period . The method for driving a plasma display panel according to any one of claims 1 to 7,
A driving method of a plasma display panel , wherein a constant potential is applied to the display electrode when a cell is not selected in an address period . In a display device that displays using a subfield having at least an address period,
A plasma display panel and a driving unit for driving the plasma display panel;
The plasma display panel is:
An address electrode formed on the first substrate and extending in the first direction;
A display electrode formed on a second substrate facing the first substrate and extending in a second direction intersecting the first direction,
The drive unit is
A first driver for applying a pulse to the address electrode;
A second driver for applying a pulse to the display electrode;
A temperature detector for detecting the temperature,
When the temperature is the first temperature, the first driving unit applies an address pulse having a first width to the address electrode in an address period, and corresponds to the address pulse having the first width. Applying a scan pulse having a first width to the display electrode,
When the temperature is a second temperature higher than the first temperature, an address pulse having a second width shorter than the first width is applied to the address electrode in the address period, and the second A display device, wherein a scan pulse having a second width corresponding to an address pulse having a width of 2 is applied to the display electrode . The display device according to claim 9, wherein
If the temperature is the first temperature, the length of the address period is the first length,
When the temperature is the second temperature, the display device is characterized in that the length of the address period is a second length shorter than the first length . The display device according to claim 9 or 10,
When the temperature is a third temperature higher than the second temperature, the width of the address pulse is set to a third width shorter than the second width, and the width of the scan pulse is set to the third width. A display device having a third width corresponding to an address pulse . The display device according to claim 11,
When the temperature is the first temperature, the width of the scan pulse is the first width,
When the temperature is the second temperature higher than the first temperature, the width of the scan pulse is a second width shorter than the first width,
When the temperature is a third temperature higher than the second temperature, the width of the scan pulse is set to a third width shorter than the second width . The display device according to any one of claims 9 to 12,
In the reset period, the second driving unit applies a reset pulse including a positive pulse whose voltage value increases with the lapse of time to the display electrode . The display device according to any one of claims 9 to 13,
The display device, wherein the second driving unit applies a reset pulse including a negative pulse whose voltage value decreases with time in the reset period to the display electrode . The display device according to any one of claims 9 to 14,
A display device, wherein an arrival potential of a scan pulse applied to the display electrode in an address period is lower than an arrival potential of a negative reset pulse applied to the display electrode in a reset period . The display device according to any one of claims 9 to 15,
A display device, wherein a constant potential is applied to the display electrode when a cell is not selected in an address period .

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