JP3544055B2 - Driving device for plasma display panel - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a driving device for a plasma display panel (hereinafter, referred to as “PDP”), and particularly to a so-called power saving automatic limit (ABL: auto limit) that automatically limits a current when the number of lit pixels exceeds a certain limit. The present invention relates to a driving device having a brightness limiter function.
[0002]
[Background description]
PDPs, which are a type of flat panel display, have a very simple panel structure and all the panel structures, including the electrodes, can be easily formed using thick-film printing technology. On the other hand, there is a drawback that power consumption is basically large due to self-luminous display. There is a demand for a useful technology that can solve the problem.
[0003]
[Prior art]
(1) Basic structure of PDP The most basic structure of PDP is to provide a pair of electrodes (anode and cathode) regularly arranged on two flat glass plates and fill a gas mainly composed of Ne between them. Things. When a voltage is applied between the anode and the cathode, a glow discharge occurs in a minute space (discharge space or discharge cell) around the electrode and emits orange light. Display is made using this light emission. In order to display arbitrary information, it is sufficient to selectively discharge and emit light from the regularly arranged discharge cells.
(2) DC PDP and AC PDP
There are two types of PDPs, a direct current type (also referred to as a DC type) in which electrodes are exposed to the discharge cells and an alternating current type (also referred to as an AC type) in which an electrode is covered with an insulating layer. Type. The DC PDP has the advantage that the brightness can be easily changed by changing the voltage application time, that is, the pulse width, and it is easy to obtain a halftone display, but is inferior to the AC PDP in terms of screen brightness. . The AC type PDP has a structural feature in that an anode and a cathode are covered with a dielectric layer. An AC voltage of about several tens to 100 KHz is applied between the anode and the cathode to discharge and emit light at the intersection of the electrodes. The electrons and ions generated in the discharge space move along the electric field, and are accumulated on the surface of the dielectric layer on the positive electrode side and the negative electrode side to form an electric field having a polarity opposite to the applied voltage. As a result, the effective voltage of the discharge space decreases, and the discharge ends in a short time. Since the charge (wall charge) on the surface of the dielectric layer remains (so-called memory effect) even after the applied voltage is lost, the next time an external voltage of opposite polarity is applied, the voltage on which the wall charge is superimposed is applied. And discharge starts at a lower voltage. Therefore, in the AC type PDP, the discharge can be maintained only by applying the sustain pulse of a relatively low voltage even outside the writing period for scanning, so that the duty time of the driving system can be lengthened and the brightness of the screen can be reduced. Can be enhanced.
(3) Two-electrode type and three-electrode AC PDPs have a two-electrode type in which an anode and a cathode are provided on each of two substrates (FIG. 3), and an anode and a cathode are provided on one substrate and the other is provided on the other. There is a three-electrode type (FIG. 4) in which a third electrode (a so-called address electrode; sometimes abbreviated as “A electrode”) is provided on the substrate. The “positive / negative” of the electrode is determined by the polarity of the applied voltage, and the polarity is inverted depending on the driving method. Therefore, the “positive / negative” is generally referred to with the panel coordinate axes (X, Y).
[0004]
In FIG. 3 (two-electrode type), 1 and 2 are glass substrates, 3 is an X electrode, 4 is a Y electrode, 5 and 6 are dielectric layers, 7 is a discharge space, and FIG. , 11 and 12 are glass substrates, 13 is an A electrode, 14 is an X electrode (a laminate of a bus electrode 14a and a transparent electrode 14b), 15 is a Y electrode (a laminate of a bus electrode 15a and a transparent electrode 15b), Reference numeral 16 denotes an ultraviolet-excited phosphor (hereinafter simply referred to as a phosphor), 17 denotes an MgO film, 18 denotes a dielectric layer, and 19 denotes a discharge space.
[0005]
The two-electrode type has a shape in which the X electrode 3 and the Y electrode 4 are opposed to the discharge space 7, and has an advantage that the structure is simple and easy to fabricate. There is a drawback that it is easy to invite. This is because in a color PDP, a phosphor must be applied to one of the two substrates 1 and 2, and charged particles generated at the time of discharge directly jump into the phosphor.
[0006]
On the other hand, in the three-electrode type PDP, the X electrode 14 and the Y electrode 15 are combined on one side of the substrate 12, and the discharge between the X electrode 14 and the Y electrode 15 is caused in the surface direction of the one side of the substrate 12. (So-called "surface discharge type" structure). Therefore, if the phosphor 16 is applied to the substrate 11 on the opposite side, the phosphor 16 and the discharge space 19 can be spatially separated from each other, so that charged particles do not directly enter the phosphor. Thus, the deterioration of the phosphor 16 can be prevented.
[0007]
FIG. 5 is a schematic cross-sectional view of a three-electrode type color PDP (a cross-sectional view in a direction crossing the A electrode), wherein 21 and 22 are glass substrates, 23 is an A electrode, 24 is a Y electrode (or X electrode), 25 Is a dielectric layer, 26 is a partition, 27 is a discharge space, and 28 is a phosphor. The illustration of the MgO film and the stacked structure of the X and Y electrodes is omitted.
(4) Sub-frame method As a driving method of such a three-electrode type color PDP, one frame is divided into, for example, eight sub-frames, and the sustain discharge period of each sub-frame is 1: 2: 4: 8: 16: A so-called “sub-frame method” is known in which a ratio of 32: 64: 128 is set and these sub-frames are combined to realize multi-tone display.
[0008]
FIG. 6 is a conceptual diagram of the frame structure of the sub-frame system. One frame is composed of eight sub-frames SF _{1 to} SF ₈ . Each subframe is composed of three periods, namely, a “reset period”, an “address period”, and a “sustain discharge period”. The lengths of the first two periods are the same, but the sustain discharge periods t _{1 to} t ₈ are as described above. It is different according to the ratio. _{Incidentally,} L _1, L 2, ......, _{L n} is the horizontal scanning lines, bold hatched in the address period of each _subframe, L _1, L 2, ......, selected in the _{L n} line sequential It shows how you are.
[0009]
FIG. 7 is a waveform timing chart in one subframe. Note that the voltage values used in the following description are merely examples, and the present invention is not limited to these values. In the reset period, a positive pulse of about +110 V is applied to the X electrode while a positive pulse of about +110 V is applied to the address electrode in order to apply a sufficient potential difference required for discharging while applying 0 V to all the Y electrodes. A pulse 31 (also referred to as an entire write pulse) is given. As a result, discharge occurs in all cells. Next, when 0 V is applied to the address electrode and the X electrode to cause a discharge in all the cells again, this discharge is terminated by self-neutralization without forming wall charges because the potential difference between the electrodes is zero. Then, a so-called self-erasing discharge is performed.
[0010]
In the address period, while applying a positive voltage 32 of about +50 V to the X electrode, a negative pulse 33 (hereinafter referred to as a “scan pulse”) of about −150 to −160 V is applied to the Y electrode line-sequentially, and the address electrode is selected. A positive pulse 34 of about +60 V (hereinafter, “address pulse”) is applied. Note that a negative voltage 35 of about -50 to -60 V is applied to the Y electrode to which no scan pulse is applied. Since there is a sufficient potential difference (approximately 210 to 220 V) required for discharge between the address electrode to which the address pulse 34 is applied and the Y electrode to which the scan pulse 33 is applied, a discharge (hereinafter referred to as "main") Address discharge ") occurs. On the other hand, the potential difference in the scan pulse portion between the X electrode and the Y electrode is about 200 to 210 V, which is about 10 V lower than that between the address electrode and the potential difference alone. Since a discharge (hereinafter referred to as a “sub-address discharge”) is also generated between the X electrode and the Y electrode as a trigger, wall charges are formed on the dielectric layer located at the intersection.
[0011]
In the sustain discharge period (also referred to as a sustain period), a positive pulse 36 (sustain pulse) of about +180 V is alternately applied to the X electrode and the Y electrode to generate a sustain discharge using wall charges. The cycle of the sustain pulse 36 is the same in all subframes. Therefore, the number of sustain pulses 36 in each subframe has a ratio relationship of 1n: 2n: 4n: 8n: 16n: 32n: 64n: 128n, and the subframes are selected or used in combination according to the display gradation. Thus, gradations from 0 to 256 (in the case of the above ratio) can be realized. Here, n is an integer determined by the frequency of the sustain pulse 39 (hereinafter, “sustain frequency”).
(5) Schematic Configuration of Plasma Display Panel and its Driving Device FIG. 8 is a configuration diagram of an AC PDP and its driving device. In this figure, 40 is an AC type PDP (hereinafter abbreviated as “panel”), 41 is an address driver, 42 is a Y scan driver, 43 is a Y common driver, 44 is an X common driver, and 45 is a control circuit.
[0012]
The control circuit 45 includes a display data control unit 45a and a panel drive control unit 45b. The display data control unit 45a temporarily stores display data (DATA) given from the outside in a frame memory 45c, The data in the memory 45 c is subjected to predetermined signal operations and timing processing, and is output to the address driver 41. The panel drive control unit 45b includes a scan driver control unit 45d and a common driver control unit 45e, and generates various timing signals based on a vertical synchronization signal (V _SYNC ) and a horizontal synchronization signal (H _SYNC ) given from the outside. The data is supplied to the display data control unit 45a, the Y scan driver 42, the Y common driver 43, the X common driver 44, and the like.
[0013]
The address driver 41 selectively applies an address pulse to the address electrodes (A ₁ , A ₂ ,..., A _m ) of the panel 40. The scan pulses are applied line-sequentially to Y ₁ , Y ₂ , Y ₃ ,..., Y _n . These address pulses and scan pulses are generated in the “address period” in one subframe. I do.
[0014]
The Y common driver 43 simultaneously applies sustain pulses to all the Y electrodes of the panel 40 (through the Y scan driver 42) during the “sustain discharge period” in one subframe, and the X common driver 44 applies the sustain pulse during one subframe. In the “reset period”, a predetermined entire write pulse is simultaneously applied to all the X electrodes of the panel 40, and in the “sustain discharge period” in one subframe, a sustain pulse is simultaneously applied to the X electrodes. is there.
[0015]
Here, reference numeral 46 denotes a variable resistor for luminance control (hereinafter referred to as "luminance control"). By operating the luminance control 46, the “display rate-sustain frequency characteristic” (described later) is switched, and the luminance (brightness) of the panel 40 is adjusted.
(6) ABL Function In general, the power consumption of a PDP depends on the number of illuminated pixels (display ratio). That is, the maximum power is when all the pixels are on (display rate 100%), and the minimum power is when all the pixels are off (display rate 0%). The upper limit power consumption Pmax is mainly determined by specification requirements. For example, if the specification requirements are equivalent to those of a 10-inch backlight liquid crystal panel of 640 × 480 pixels, Pmax = about 6 W. As described above, since the power consumption of the PDP is maximized at a display rate of 100%, it is easy to set the power at the display rate of 100% to Pmax. However, the display rate in the normal operation range of the personal computer is at most 30%. %, There is too much margin between the power in the normal operation range and Pmax, and an over specification cannot be denied.
[0016]
Therefore, when the display ratio exceeds a predetermined reference display ratio (for example, a display ratio slightly higher than the display ratio in the normal operation range), the sustain frequency is lowered (in other words, the above-mentioned ratio “n”). Is reduced), and the power consumption of the PDP is suppressed to Pmax.
FIG. 9 is a schematic diagram of the ABL function. In this figure, the upper half of the vertical axis represents the power, the lower half the sustain frequency, and the horizontal axis the display rate. The power that increases with an increase in the display ratio is limited by Pmax. A plurality of line T ₁ through T _m described in the intersections of the display ratio axis the frequency axis, respectively - a line indicating "display ratio sustain frequency characteristics". One of these characteristic lines T ₁ through T _m is the operating position (brightness setting value) of the brightness control 46 of FIG. 8 is selected depending.
[0017]
When the luminance setting value is set to the maximum luminance, the lowermost characteristic line _Tm is selected. The characteristic line T _m is until the power increases with increasing display ratio matches the Pmax keeps the sustain frequency constant, after more than Pmax (crossover C _m later) lowers the sustain frequency Work like that. When the luminance is lowered by one step, the characteristic line _{Tm-1 above it} is selected. Similarly, after the characteristic line _Tm-1 exceeds Pmax (after the break point Cm _-1 ), the characteristic line _{Tm-1 functions} to lower the sustain frequency. Similarly, other characteristic lines T _i (i is m−2,..., 3, 2, 1) work to lower the sustain frequency after exceeding Pmax (after the break point C _i ).
[0018]
[Problems to be solved by the invention]
However, such a conventional PDP driving device has a problem that the operation feeling of the brightness control in the operation range of the ABL function is poor for the following reasons.
As described above, when the brightness control is set to maximum brightness, it is selected bottom characteristic curve the T _m of FIG. 9, or the top of the characteristic line T ₁ is selected when set to minimum brightness. That is, each characteristic line _T 1 with the operation of the brightness _{control, T 2, T 3, ......} , T m-2, T m-1, T m is selected sequentially, so that switched the sustain frequency Although the brightness of the PDP changes, when the display rate is within the operating range of the ABL function (see reference numeral a in FIG. 9), for example, even if the brightness control is operated from the maximum brightness to the minimum brightness, a “point” is reached. The sustaining frequency is not switched at all (therefore, the luminance does not change), and when passing through that point, the luminance suddenly starts to change, resulting in an unpleasant operation feeling.
[0019]
A “point” is given by the intersection of a perpendicular drawn down from the axis of display rate and the selected characteristic line. If the intersection point is positioned in the hatched portion of the characteristic line (the portion between C ₁ from C _m), it becomes undesirable operation feeling of the. For example, if the “point” is at the X position between C ₃ and C ₂ , the sustain frequency does not change at all from the characteristic line _Tm to T ₃ , so that the brightness control does not work. I feel like that.
[0020]
Therefore, an object of the present invention is to improve the operation feeling of the brightness control in the operation range of the ABL function.
[0021]
[Means for Solving the Problems]
In FIG. 1, a driving apparatus for a plasma display panel according to the present invention uses display rate information indicating the number of lit pixels or a ratio of the number of lit pixels of a plasma display panel (PDP) 1 whose luminance is changed by a sustain frequency. , A brightness setting means 3 for setting the brightness of the plasma display panel 1, and a number of characteristic lines in a predetermined conversion table in accordance with the setting value of the brightness setting means 3. A conversion table selecting unit for selecting one of the plurality of characteristic lines; and a sustain frequency determining unit for determining a sustain frequency by referring to the selected characteristic line based on the display rate information. , in the frequency range between predetermined maximum sustain frequency to a predetermined minimum sustain frequency, the characteristic line, the high-frequency side breakpoints Along with the maximum sustain frequency, a low frequency side break point is matched with the minimum sustain frequency, and the high frequency side break point and the low frequency side break point are connected. The display ratio of the high frequency side break point and the low frequency side break point of a line is shifted .
[0022]
Alternatively, the display ratio detecting means 2 regards the power consumption of the plasma display panel 1 or a physical quantity proportional to the power consumption as the display ratio information.
[0023]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
The point of this embodiment is that the "display ratio-sustain frequency conversion table" of the PDP is improved in order to improve the operation feeling of the brightness control of the AC PDP with the subframe type / ABL function. The principle of the subframe system, the ABL function, and the AC PDP and the configuration thereof will be referred to the description of the related art as appropriate.
[0024]
FIG. 2 is a conceptual diagram showing a “display rate-sustain frequency conversion table” in the present embodiment, and corresponds to FIG. 9 of the related art.
In FIG. 2, the upper half of the vertical axis represents the power, the lower half the sustain frequency, and the horizontal axis the display ratio. Although it is common to the related art in that the power that increases with an increase in the display rate is limited by Pmax, a plurality of characteristic lines T ₁ ′ to T _m ′ described in the intersection region of the frequency axis and the display rate axis are different. Does not match in terms of shape.
[0025]
That is, all the characteristic line T _{1 '~T m'} is in the frequency range fΔ between the predetermined maximum sustain frequency f _H to a predetermined minimum sustain frequency f _L, ▲ 1 ▼ linear in accordance with the display ratio In addition to having the sustain frequency determining characteristics, (2) sustain frequencies (f ₁ , f ₂ , f ₃ ,..., Fm ₋₂ ) for each characteristic line corresponding to the same display ratio (for example, display ratio a). , F _m−1 , f _m ) have different shapes.
[0026]
Specifically, the characteristic line T _m ′ selected when the luminance control (see reference numeral 46 in FIG. 8) is set to the maximum luminance is such that the break point A _Hm on the high frequency side coincides with f _H, and The bend point A _Lm on the frequency side is made to coincide with f _L , and an oblique angle between A _Hm and A _Lm is obtained so as to obtain a linear sustaining frequency determination characteristic according to the display rate within the range of fΔ. Connected by a line. The characteristic line T ₁ ′ selected when the luminance control is set to the minimum luminance is such that the high frequency side break point A _H1 matches f _H and the low frequency side break point A _{L1 changes} to f _L. match, and in the range of Fderuta, as characterized in the linear sustain frequency in accordance with the display ratio is obtained, linking between the a _H1 and a _L1 at an oblique line. Further, the characteristic line T _j ′ (j is 2, 3,..., M−2, m−1) selected when the luminance control is set to an arbitrary luminance between the maximum luminance and the minimum luminance is high. The break point A _Hj on the frequency side is made to coincide with f _H , the break point A _Lj on the low frequency side is made to coincide with f _L , and, within the range of fΔ, the linear sustain frequency determining characteristic according to the display rate is As can be obtained, A _Hj and A _Lj are connected by oblique lines.
[0027]
Then, all the characteristic lines T ₁ ′, T ₂ ′, T ₃ ′,..., T _m−2 ′, T _m−1 ′, and T _m ′ are broken points A _H1 , A _H2 , A _H3 on the high frequency side. _{, ......, a Hm-2,} a Hm-1, a Hm and low-frequency side of the break point _{a L1, a L2, a L3} , ......, a Lm-2, a Lm-1, a Lm is displayed It is offset in the axial direction.
According to such a “display rate-sustain frequency conversion table”, when the luminance control is operated when the display rate (a for convenience) is within the operation range of the ABL function, each characteristic line T ₁ ′ , T ₂ ′, T ₃ ′,..., T _m−2 ′, T _m−1 ′, T _m ′ are defined as f ₁ , f ₂ , f _{3 ,.} since _2, f _m-1, changes at regular intervals and f _m, and the actual luminance change operation amount of the luminance control corresponding to the one-to-one, does not worsen the feeling of operation.
[0028]
As the “display ratio” for referring to the conversion table, the number of illuminated pixels of the PDP may be directly used, or the ratio of illuminated pixels to non-illuminated pixels (ie, the ratio of illuminated pixels) may be used. Good. Alternatively, since there is a correlation between the number of lighting pixels and the power consumption of the PDP, this power consumption or a physical quantity proportional to the power consumption (generally, a converted current value of the power consumption) may be used.
[0029]
Further, the "display rate-sustain frequency conversion table" of the present embodiment can be configured in the form of a so-called table map, or can be configured using, for example, a function calculator or a hard logic.
[0030]
【The invention's effect】
According to the present invention, in the PDP with the ABL function, there is obtained an advantageous effect that the operation feeling of the brightness control in the operation range of the ABL function can be improved, which is not available in the related art.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating the principle of the present invention.
FIG. 2 is a conceptual diagram of a display rate-sustain frequency conversion table according to one embodiment.
FIG. 3 is a sectional structural view of a two-electrode PDP.
FIG. 4 is a sectional structural view of a three-electrode PDP.
FIG. 5 is a sectional structural view of a three-electrode PDP.
FIG. 6 is a diagram illustrating a frame configuration of a subframe system.
FIG. 7 is a waveform timing chart of one subframe.
FIG. 8 is a schematic configuration diagram of an AC type PDP and its driving device.
FIG. 9 is a conceptual diagram of a conventional display rate-sustain frequency conversion table.
[Explanation of symbols]
1: plasma display panel 2: display ratio detection means 3: luminance setting means 4: conversion table selection means 5: sustain frequency decision unit _{T 1 ', T 2',} T 3 ', ......, T m-2' , T _m-1 ′, T _m ′: characteristic line f _H : maximum sustain frequency f _L : minimum sustain frequency fΔ: frequency range

Claims (2)

Display rate detection means for detecting display rate information indicating the number of illuminated pixels or a ratio of the number of illuminated pixels of a plasma display panel for changing luminance according to a sustain frequency;
Brightness setting means for setting the brightness of the plasma display panel,
Conversion table selection means for selecting one of a number of characteristic lines in a predetermined conversion table according to the setting value of the brightness setting means,
Sustain frequency determining means for determining a sustain frequency by referring to the selected characteristic line with the display rate information,
All the characteristic lines in the conversion table are within a frequency range from a predetermined maximum sustain frequency to a predetermined minimum sustain frequency,
Each characteristic line has a high frequency side break point coincident with the maximum sustain frequency, a low frequency side break point coincides with the minimum sustain frequency, and the high frequency side break point and the low frequency side break point. Wherein the display ratios of the break points on the high frequency side and the break points on the low frequency side of all the characteristic lines are shifted from each other . 2. The plasma display panel driving apparatus according to claim 1, wherein the display ratio detection unit regards the power consumption of the plasma display panel or a physical quantity proportional to the power consumption as the display ratio information. .

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