JP3595273B2 - Panel display device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a gas discharge panel display device and a method for driving a gas discharge panel used for image display of a computer, a television, and the like, and more particularly, to an AC device for writing an image by storing charges in a dielectric layer and emitting light by maintaining a discharge. Type PDP.
[0002]
[Prior art]
2. Description of the Related Art In recent years, in a display device used for a computer, a television, or the like, a gas discharge panel such as a plasma display panel (hereinafter, referred to as a PDP) is a large, thin, and lightweight gas discharge panel. Attention has been paid.
[0003]
The PDP is displayed as an image by selectively emitting light from discharge cells arranged in a matrix.
PDPs are roughly classified into a direct current type (DC type) and an alternating current type (AC type). At present, the AC type suitable for enlargement is mainly used.
In an AC type PDP, each discharge cell can originally express only two gradations of lighting or extinguishing. Therefore, one frame (one field) is divided into a plurality of subframes (subfields), and lighting / extinguishing in each subframe is performed. Are used to display an intermediate gray scale.
[0004]
In each sub-frame, an image is displayed by an ADS (Address Display-period Separation) method. That is, as shown in FIG. 25, each sub-frame is composed of a series of sequences including an initialization period, a writing period, a discharge sustaining period, and an erasing period. In the discharge sustaining period, an AC sustaining pulse is applied to all the discharge cells at once. The voltage of the sustain pulse applied at this time is set in a range (usually in the range of 150 to 200 V) such that the discharge is performed in the discharge cells in which the wall charges are accumulated and is not discharged in the other cells.
[0005]
The principle of this light emission is basically the same as that of a fluorescent lamp. By applying a sustain pulse to generate a normal glow discharge, ultraviolet rays (Xe resonance line, wavelength 147 nm) are generated from Xe, and the phosphor is excited to emit light. However, since the conversion efficiency of the discharge energy to ultraviolet light and the conversion efficiency of the phosphor to visible light are poor, it is difficult to obtain a high luminance like a fluorescent lamp.
[0006]
Like other displays, there is also a demand for higher definition in PDPs (for example, a high-definition television that is being put into practical use in recent years has a high-definition pixel with 1920 × 1080 full specifications). In such a high-definition PDP, the luminous efficiency tends to be further reduced.
[0007]
[Problems to be solved by the invention]
Under such a background, it is desired to improve the luminous efficiency (the luminous amount with respect to the input electric energy) in the PDP. To address this problem, for example, a technology for improving the luminous efficiency by improving the structure of the PDP and a technology for collecting a current (reactive current) that does not contribute to the emission of ultraviolet light have been developed. There is also a demand for a technique for reducing the amount.
[0008]
As shown in FIG. 25, a rectangular wave is generally used as the sustain pulse. Since the rise of this rectangular wave is sharper than that of a waveform such as a trigonometric function wave, basically, if a rectangular wave is used as the sustain pulse, discharge can be started in a relatively short time from the start of rise. Therefore, a relatively stable image can be displayed.
[0009]
However, when a sustain pulse is applied, a so-called "discharge delay" occurs in which the discharge is started with a considerable delay from its rise, with a certain probability. In particular, a discharge delay is likely to occur in the first sustain pulse applied during the sustain period.
Such “discharge delay” is a factor that degrades the quality of the displayed image. That is, although a large number of discharge cells are arranged in a PDP, if "discharge delay" occurs with a certain probability as described above, "discharge delay" occurs in some of the discharge cells to be turned on. As a result, lighting failure occurs and the image quality of the displayed image is degraded. Therefore, a technique for improving this is also desired.
[0010]
In view of such problems, a first object of the present invention is to improve the luminous efficiency by suppressing the generation of a reactive current when driving a gas discharge panel such as a PDP.
A second object is to improve the image quality by suppressing the occurrence of a discharge delay in the discharge sustaining period.
[0011]
[Means for Solving the Problems]
In order to achieve the first object, the present invention provides a method for applying a sustain pulse in which a fall is completed by a time three times as long as a rise time of the sustain pulse from a peak time. The waveform of the sustain pulse is defined so that the waveform is formed.
[0012]
In addition, in order to form a current waveform having the above characteristics, when applying the sustain pulse, any one of the following first to third characteristics is added to the sustain pulse.
A first feature is that a pulse having a polarity opposite to that of the sustain pulse is applied for a short time before the leading edge (pulse rise) of the sustain pulse.
The second feature is that the waveform is set so that a higher voltage is applied in a certain period from the leading edge of the sustain pulse (rising edge of the pulse) in absolute value than a voltage applied thereafter.
[0013]
The third feature is that a pulse having a polarity opposite to that of the sustain pulse is applied immediately after the trailing edge (falling pulse) of the sustain pulse.
When a current waveform having the above characteristics is formed, the reactive current is suppressed as compared with a case where a sustain pulse having a general waveform is applied, so that luminous efficiency can be improved.
[0014]
When the first to third characteristics are added to the sustain pulse, the following effects are exhibited in addition to the above-described improvement in the light emission efficiency.
When the first feature is added to the sustain pulse, when an opposite polarity pulse is initially applied, electrons move from one electrode to the other electrode, but before the pulse reaches the other electrode, the electron moves toward the other electrode. Starts to be returned to one electrode side.
[0015]
The reciprocation of electrons in the discharge space in the initial stage generates a large amount of charged particles (electrons and ions) contributing to light emission, thereby further improving the light emission efficiency.
In addition, since the charged particles reciprocate between the electrodes, a pilot spark of discharge is formed, and the discharge is started with high probability (EVOLUTION OF DISCHARGE) by the pilot spark, so that the second object, that is, the suppression of the discharge delay, is also performed. You.
[0016]
In order to reliably obtain the above effect, the voltage of the reverse polarity pulse is preferably set to have a voltage absolute value of 1.0 times or more with respect to the sustain pulse voltage. It is preferable to set the absolute value to 1.5 times or more.
Further, it is preferable to set this time to 100 ns or less for the period for applying the reverse polarity pulse.
[0017]
In particular, the time during which the voltage absolute value becomes 1.0 times or more the sustain pulse voltage is preferably set to 100 ns or less, and more preferably 50 ns or less.
Also when the second feature is added to the sustain pulse, a high voltage is applied for a certain period from the rise of each sustain pulse, so that the discharge is started reliably and the discharge delay is suppressed.
[0018]
In particular, if a high voltage equal to or higher than the discharge starting voltage of the discharge cell is applied during this fixed period, the effect is remarkable.
Here, it is preferable that a voltage higher than the sustain voltage applied thereafter by 50 V or more in absolute value be applied for a certain period from the leading edge of the sustain pulse.
[0019]
In general, when a high voltage is applied, dielectric breakdown of the dielectric layer and an increase in power consumption tend to occur, but the time for applying the high voltage (voltage equal to or higher than the discharge starting voltage of the discharge cell) is set to 100 ns or less or 10 ns or less. If the setting is made in a short time, dielectric breakdown of the dielectric layer and increase in power consumption can be avoided.
When the third feature is added to the sustain pulse, the reactive current caused by ions remaining in the discharge cells after the fall of the sustain pulse is suppressed.
[0020]
In other words, ions remaining in the discharge cells after the falling of the pulse are low-active and do not contribute to light emission. When the ions reach the electrodes, a reactive current is generated and the light emission efficiency is reduced. If the pulse is added with the third feature, the reactive current can be suppressed, and in this respect, it greatly contributes to the improvement of the luminous efficiency.
Here, it is preferable that the maximum value of the absolute voltage value of the reverse polarity pulse be 50 V or more.
[0021]
Further, the time for applying the reverse polarity pulse is set to 100 ns or less, and more preferably 10 ns or less.
By the way, in one discharge sustaining period, usually, a plurality of sustaining pulses are continuously applied to each discharge cell while switching the polarity. Therefore, in order to achieve a sufficient effect, it is preferable to apply the above-described waveform characteristics to all of the continuous sustain pulses, but apply the above-described waveform characteristics to only some of the sustain pulses. You may. However, also in this case, the characteristics of the waveform should be applied to at least the leading sustain pulse in the discharge sustain period.
[0022]
BEST MODE FOR CARRYING OUT THE INVENTION
(Overall description of display device)
First, the overall configuration of the PDP display device according to the present embodiment will be described.
This PDP display device is composed of an AC surface discharge type (AC type) PDP and its driving device. FIG. 1 is a sketch of this PDP.
[0023]
In this PDP, a front substrate 11 and a rear substrate 12 are arranged parallel to each other with a gap therebetween, and their outer peripheral portions are sealed.
On the facing surface of the front substrate 11, a scanning electrode group 19a and a sustaining electrode group 19b in the form of stripes are formed in parallel with each other, and the electrode groups 19a and 19b are covered with a dielectric layer 17 made of lead glass or the like. The surface of the dielectric layer 17 is covered with a protective layer 18 made of an MgO film. On the opposing surface of the rear substrate 12, a stripe-shaped data electrode group 14 and a dielectric layer 13 made of lead glass or the like covering the surface are provided, and a partition 15 is arranged thereon in parallel with the data electrode group 14. Is established. The gap between the front substrate 11 and the rear substrate 12 is partitioned by a partition 15 at an interval of about 100 to 200 μm, and the discharge gas is sealed. The charging pressure of the discharge gas is usually 1 × 10 3 so that the inside of the panel becomes negative with respect to the external pressure (atmospheric pressure). ⁴ ~ 7 × 10 ⁴ It is set in the range of about Pa, but 8 × 10 ⁴ Setting the pressure to a high pressure of Pa or more is advantageous for obtaining high luminous efficiency.
[0024]
FIG. 2 is a diagram showing an electrode matrix of the PDP. The electrode groups 19a and 19b and the data electrode group 14 are arranged orthogonally to each other, and a discharge cell is formed in a space between the front substrate 11 and the rear substrate 12 where the electrodes intersect. Adjacent discharge cells are separated by the partition walls 15 so that discharge diffusion to the adjacent discharge cells is blocked, so that high-resolution display can be performed.
[0025]
In a PDP for a single color display, a mixed gas mainly composed of neon is used as a discharge gas, and display is performed by emitting light in a visible region at the time of discharge. However, in a PDP for a color display as shown in FIG. A phosphor layer 16 made of phosphors of the three primary colors red (R), green (G), and blue (B) is formed on the inner wall of the cell, and a mixed gas (neon-neutral) mainly composed of xenon is used as a discharge gas. Xenon or helium-xenon) is used, and color display is performed by converting the ultraviolet light generated by the discharge into visible light of each color by the phosphor layer 16.
[0026]
This PDP is driven using an in-frame time division gray scale display method.
FIG. 3 is a diagram illustrating a method of dividing one frame when expressing 256 gradations, where the horizontal direction indicates time, and the hatched portions indicate discharge sustaining periods.
For example, in the example of the division method shown in FIG. 3, one frame is composed of eight subframes, and the ratio of the sustaining periods of each subframe is 1, 2, 4, 8, 16, 32, 64. , 128, and 256 gradations can be expressed by the combination of the 8-bit binaries. In addition, in the NTSC system television video, since the video is composed of 60 frames per second, the time of one frame is set to 16.7 ms.
[0027]
In each subframe, an image is displayed on the PDP by the ADS method. That is, each subframe is configured by a series of sequences including an initialization period, a writing period, a discharge sustaining period, and an erasing period.
FIG. 4 is a timing chart when a pulse is applied to each electrode in one subframe in the present embodiment.
[0028]
In the initialization period, the state of all the discharge cells is initialized by applying an initialization pulse to the entire scan electrode group 19a at once.
During the writing period, a wall pulse is accumulated in a discharge cell to be turned on by applying a data pulse to a selected electrode in the data electrode group 14 while sequentially applying a scan pulse to the scan electrode group 19a. Then, pixel information for one screen is written.
[0029]
In the discharge sustaining period, by applying a sustaining pulse while changing the polarity at once between the scan electrode group 19a and the sustaining electrode group 19b, a discharge occurs in the discharge cell in which the wall charges are accumulated, and light emission occurs for a predetermined time. Let it.
As shown in FIG. 4, each sustain pulse has a unique waveform instead of a simple rectangular wave, which will be described in detail later.
[0030]
In the erasing period, the wall charges of the discharge cells are erased by applying a narrow erasing pulse to the scan electrode group 19a or the sustain electrode group 19b at a time.
(Detailed description of driving device and driving method)
FIG. 5 is a block diagram showing a configuration of the driving device 100.
The driving device 100 includes a preprocessor 101 for processing video data input from an external video output device, a frame memory 102 for storing processed video data, and a synchronization pulse for generating a synchronization pulse for each frame and each subframe. The generating unit 103 includes a scan driver 104 for applying a pulse to the scan electrode group 19a, a sustain driver 105 for applying a pulse to the sustain electrode group 19b, and a data driver 106 for applying a pulse to the data electrode group 14.
[0031]
The preprocessor 101 extracts video data (frame video data) for each frame from the input video data, creates video data of each sub-frame (sub-frame video data) from the extracted frame video data, and To be stored. Also, data is output to the data driver 106 line by line from the current sub-frame video data stored in the frame memory 102, or a synchronization signal such as a horizontal synchronization signal or a vertical synchronization signal is detected from the input video data, It also sends a synchronization signal to the synchronization pulse generator 103 for each frame and each subframe.
[0032]
The frame memory 102 can divide and store each sub-frame video data for each frame.
Specifically, the frame memory 102 is a two-port frame memory including two memory areas for one frame (stores eight sub-frame images), and writes frame image data to one of the memory areas. The operation of reading frame video data written in the other memory area from the other memory area can be alternately performed.
[0033]
The synchronization pulse generation unit 103 refers to a synchronization signal transmitted from the preprocessor 101 for each frame and each subframe, and generates a trigger signal for instructing a timing to start an initialization pulse, a scan pulse, a sustain pulse, and an erase pulse. Generated and sent to each of the drivers 104-106.
The scan driver 104 generates and applies an initialization pulse, a scan pulse, a sustain pulse, and an erase pulse in response to a trigger signal sent from the synchronization pulse generator 103.
[0034]
FIG. 6 is a block diagram showing the configuration of the scan driver 104.
The initialization pulse, the sustain pulse, and the erase pulse are applied to all the scan electrodes 19a in common.
Therefore, as shown in FIG. 6, the scan driver 104 includes three pulse generators (initialization pulse generator 111, sustain pulse generator 112a, and erase pulse generator 113) for generating each pulse. ing. These three pulse generators are connected in series by a floating ground method, and operate in response to a trigger signal from the synchronizing pulse generation unit 103, so that an initialization pulse, a sustain pulse, and an erase pulse are alternatively selected. , Are applied to the scanning electrode group 19a.
[0035]
The scan driver 104 includes a scan pulse generator 114 and a multiplexer 115 connected thereto as shown in FIG. 6 in order to sequentially apply scan pulses to the scan electrodes 19a1, 19a2,. According to a method in which a pulse is generated by the scanning pulse generator 114 and switched and output by the multiplexer 115 in response to a trigger signal from the synchronization pulse generating unit 103, a scanning pulse generating circuit is individually provided for each scanning electrode 19a. May be provided.
[0036]
Switches SW1 and SW2 are provided to selectively apply the outputs from the three pulse generators 111 to 113 and the output from the scan pulse generator 114 to the scan electrode group 19a.
The sustain driver 105 includes a sustain pulse generator 112b, generates a sustain pulse in response to a trigger signal from the synchronization pulse generator 103, and applies the generated sustain pulse to the sustain electrode group 19b.
[0037]
The data driver 106 outputs data pulses in parallel to the data electrode groups 141 to 14M based on subfield information corresponding to one line input serially.
FIG. 7 is a block diagram showing the configuration of the data driver 106.
The data driver 106 includes a first latch circuit 121 that captures sub-frame video data for each scan line, a second latch circuit 122 that stores the data, a data pulse generator 123 that generates data pulses, and data electrodes 141 to 14M. It is composed of AND gates 1241 to 124M provided at the entrance.
[0038]
The first latch circuit 121 fetches the sub-frame video data sequentially sent from the preprocessor 101 in order of several bits in synchronization with the CLK signal, and scans one scan line of the sub-frame video data (for each of the data electrodes 141 to 14M). When information indicating whether or not to apply a data pulse is latched, it is moved to the second latch circuit 122 collectively. The second latch circuit 122 opens one of the AND gates 1241 to 124M corresponding to the data electrode to which the data pulse is applied, in response to the trigger signal sent from the synchronization pulse generator 103. Then, the data pulse generator 123 generates a data pulse in synchronization with this. As a result, a data pulse is applied to the data electrode corresponding to the one whose AND gate is opened.
[0039]
In such a driving device 100, as described below, the operation for one sub-frame constituted by a series of a sequence including an initialization period, a writing period, a discharge sustaining period, and an erasing period is repeated eight times, whereby 1 An image of the frame is displayed. It should be noted that the number of subframes may be set to more than eight in order to prevent false contours.
[0040]
In the initialization period, the switch SW1 of the scan driver 104 is turned on and the switch SW2 is turned off, and the initialization pulse generator 111 applies the initialization pulse to all the scan electrodes 19a at once, thereby setting all the discharge cells. An initialization discharge is performed to accumulate wall charges in each discharge cell. Here, by applying a certain wall voltage to each discharge cell, the rise of the write discharge in the next write period can be hastened.
[0041]
During the writing period, the switch SW2 of the scan driver 104 is turned on and the switch SW1 is turned off, and the scan pulse of the negative voltage generated by the scan pulse generator 114 is applied to the scan electrodes 19a1 to 19aN of the first row to the last row. Are sequentially applied. At the same time, the data driver 106 performs a write discharge by applying a positive voltage data pulse to the data electrodes 141 to 14M corresponding to the discharge cells to be lit, The wall charges are accumulated in the discharge cells. In this way, by accumulating wall charges on the surface of the dielectric layer of the discharge cell to be lighted, a latent image for one screen is written.
[0042]
The pulse width (write pulse width) of the scan pulse and the data pulse is desirably set as short as possible in order to increase the driving speed. However, if the write pulse width is too short, a write failure easily occurs. Also, the pulse width usually needs to be set to about 1.0 μsec or more due to circuit restrictions.
In the discharge sustaining period, the switch SW1 of the scan driver 104 is turned on and the switch SW2 is turned off, and a sustain pulse generator 112a applies a discharge pulse of a fixed length (for example, 1 to 5 μsec) to the scan electrode group 19a. The operation and the operation in which the sustain pulse generator 112b of the sustain driver 105 collectively applies a discharge pulse of a fixed length to the sustain electrode group 19b are alternately repeated.
[0043]
As a result, in the discharge cells in which the wall charges are accumulated during the writing period, a discharge occurs when the potential on the dielectric layer surface exceeds the discharge starting voltage, and ultraviolet light is emitted in the discharge cells along with the sustain discharge. This is converted into visible light by the phosphor layer, thereby emitting visible light corresponding to the color of the phosphor layer.
During the erasing period, the switch SW1 of the scan driver 104 is turned on and the switch SW2 is turned off, and a narrow erasing pulse is applied from the erasing pulse generator 113 to the scanning electrode group 19a collectively to generate an incomplete discharge. Thereby, wall charges in each discharge cell are erased.
[0044]
<Pulse waveform during discharge sustain period>
First, an outline will be given of the characteristics of the waveform of the sustain pulse applied between the scan electrode group 19a and the sustain electrode group 19b and their effects during the discharge sustain period.
According to the present invention, when a sustain pulse is applied, a current waveform is formed that has a characteristic that the fall ends before the time required for the rise to the peak reaches three times the elapsed time from the peak time. Thus, the waveform of the sustain pulse was adjusted.
[0045]
That is, when the sustain pulse is applied, when the time that is three times longer than the time required for the rise has elapsed from the peak time, the current is adjusted to be extremely small, thereby suppressing the reactive current and improving the luminous efficiency. I tried to make it.
It has also been found that the current waveform having the above characteristics can be obtained by adding any of the following first to third characteristics when applying the sustain pulse.
[0046]
First feature: Prior to the leading edge (pulse rise) of the sustain pulse, a pulse of the opposite polarity to the sustain pulse is applied for a short time.
Second feature: The waveform is set so that a higher voltage is applied in a certain period from the leading edge of the sustain pulse (rising edge of the pulse) in absolute value than the voltage applied thereafter.
[0047]
Third feature: Immediately after the trailing edge (falling pulse) of the sustain pulse, a pulse of the opposite polarity is applied.
In addition, when the sustain pulse is applied, by adding any one of the above-described first to third features, the above-described feature (the time that is three times as long as the time required for the rise to the peak elapses from the peak time) It was also experimentally confirmed that a current waveform having a time until the end of the current) was obtained.
[0048]
Next, the reason why the generation of the current waveform having the above characteristics can suppress the reactive current will be described below.
Here, a mechanism in which light emission occurs in the discharge space will be considered by taking a case where a positive sustain pulse is applied to the scan electrode 19a as an example.
When a positive sustain pulse (+ V) is applied to the electrode 19a, an electric field E from the electrode 19a to the electrode 19b is generated in the discharge space 20, as shown in FIG. Immediately after the start of pulse application (initial stage), electrons that move at a very high speed from one electrode 19b toward the other electrode (19a) are generated in the discharge space 20, and FIG. As shown in (1), the electrons collide with the neutral gas particles (Xe), generating electrons (e) and ions (Xe +) from the gas particles, and also generating excited gas particles. Then, the generated electrons move toward the electrode 19a, start discharging while colliding with other gas particles, and the discharge further spreads. On the other hand, it is considered that the generated positive ions also move toward the electrode 19b as shown in FIG.
[0049]
Here, since the electrons (e) and the ions (Xe +) in the discharge space are regarded as current carriers, when the electrons or ions generated in the discharge space 20 reach the electrode 19a or the electrode 19b, the electrode 19a and the electrode 19b is generated.
By the way, comparing the moving speeds of the electron and the ion in the electric field, the moving speed of the electron is much higher than that of the ion due to the difference in mass (the speeds of both are different by several orders of magnitude).
[0050]
Therefore, as shown in FIG. 9A, the peak of the current (current due to the electrons) mainly due to the electrons reaching the electrode 19a appears at an early time immediately after the start of the application of the sustain pulse, and thereafter, the peak is relatively high. At a later time, a peak of current (current by ions) due to the ions reaching the electrode appears.
Here, the current at an early time, which is considered to be due to electrons moving at high speed in the discharge space, greatly contributes to light emission, whereas the current at a late time, which is considered to be due to ions moving at low speed, has a small contribution to light emission, and is therefore slow. If the current at the time is suppressed, the luminous efficiency can be improved.
[0051]
Further, as described above, when the above-described first to third features are added when the sustain pulse is applied, “the time that is three times as long as the time required for the rise to the peak to elapse from the peak time” elapses. Since it is known that a current waveform having the characteristic of “falling ends” can be formed, it can be said that “current by electrons” also has the characteristic of this waveform.
[0052]
Therefore, when a current waveform having the above characteristics is formed, “current due to ions” that does not contribute to light emission is suppressed, and light emission efficiency is improved.
The above contents are supported by the following experimental results.
FIG. 9B shows a voltage waveform and a current waveform observed when a rectangular pulse is applied by a drive circuit between display electrodes of an AC type gas discharge panel, as shown in FIG. 9C. The measurement is performed by incorporating a voltmeter and an ammeter (current probe) in the wiring connecting the drive circuit and the display electrode.
[0053]
The fact that the current waveform in FIG. 9B substantially matches the sum of the two current waveforms shown in FIG. 9A supports the above description.
FIG. 10A shows a current waveform and a light emission luminance waveform observed when a pulse is applied by a drive circuit between display electrodes of an AC gas discharge panel. In the current waveform in FIG. 10A, a sharp peak A1 is seen at an early time and a gentle peak A2 is seen at a late time. On the other hand, in the emission luminance waveform, a sharp peak B1 is clearly seen at an early time, but a gentle peak B2 at a late time is hardly seen. Note that this emission luminance waveform is similar to the waveform of the current caused by electrons in FIG.
[0054]
FIG. 10B is a waveform of the light emission efficiency derived from the voltage waveform and the current waveform of FIG. 9B and the light emission luminance waveform of FIG. 10A. This luminous efficiency waveform indicates a change in luminous efficiency when the sustain pulse is applied (how the ratio of the luminous luminance to the power supplied every minute time changes).
FIG. 10 (c) shows the luminous efficiency waveform of FIG. 10 (b) superimposed on the current waveform of the electrons of FIG. 9 (a). FIG. 10C shows that the peak of the current waveform due to the electrons and the peak of the luminous efficiency waveform overlap, which indicates that high luminous efficiency can be obtained at the time when the current due to the electrons flows.
[0055]
That is, as shown in FIG. 10C, if a current waveform close to the peak waveform of “current due to electrons” is formed when the sustain pulse is applied, power is supplied intensively at a time when the luminous efficiency is high. Therefore, it can be seen that high luminous efficiency can be obtained.
The first to third features and effects will be more specifically described in the following first to fourth embodiments.
[0056]
[Embodiment 1]
As shown in FIG. 4, in the present embodiment, positive sustain pulses are alternately applied to scan electrode group 19a and sustain electrode group 19b during the discharge sustain period, but prior to the rise of each sustain pulse. A reverse polarity pulse is applied for a short time.
Hereinafter, the case where the sustain pulse is applied to the scan electrode group 19a will be described in detail, and the case where the sustain pulse is applied to the sustain electrode group 19b is the same.
[0057]
First, when a positive sustain pulse is applied to the scan electrode group 19a, a negative pulse is applied for a short time prior to its rise, and then a positive sustain pulse (sustain voltage Vs) is applied.
Here, the value of the sustain voltage Vs is a voltage value set within a range such that discharge is performed in a discharge cell in which wall charges are accumulated at the time of addressing and is not discharged in a discharge cell in which wall charges are not accumulated. , PDP panel design (discharge cell size, electrode width, dielectric layer thickness, etc.).
[0058]
Generally, the sustain voltage Vs is set at a voltage lower than the discharge start voltage of the discharge cell (a range from the discharge start voltage -50 V to the discharge start voltage). It can be set lower than a reasonable value.
In addition, the discharge starting voltage in a PDP can be measured as follows.
[0059]
While visually observing the PDP, the voltage applied to the PDP from the panel driving device is gradually increased, and the applied voltage when one or a specified number (for example, three) or more of the discharge cells of the PDP starts to light up is increased. Read and record this as the firing voltage.
(Description of effects of the present embodiment)
FIG. 11A shows an example of the sustain pulse waveform according to the present embodiment. The basic part of the sustain pulse is a rectangular wave, but when the sustain pulse is applied, the polarity is reversed before the rise of the sustain pulse. A pulse is applied for a short time. On the other hand, FIG. 11B shows an example in which the sustain pulse is a general rectangular wave.
[0060]
In the case where a simple rectangular wave is used as shown in FIG. 11B, when a sustain pulse is applied to the discharge cells, fast electrons initially generated in the discharge space do not contribute to light emission, and do not contribute to light emission. From the first electrode to the other electrode.
On the other hand, when a positive sustain pulse is applied to the electrode 19a, if a negative pulse (-V) is applied for a short time prior to the rise of the sustain pulse as shown in FIG. Accordingly, as shown in FIG. 12A, an electric field E from the electrode 19b to the electrode 19a is generated in the discharge space 20. Then, in the discharge space 20, electrons that move quickly from the electrode 19a to the electrode 19b are generated. Thereafter, when a positive voltage is applied to the electrode 19a as shown in FIG. 12B, the above electrons are pulled back toward the electrode 19a and are absorbed by the dielectric layer on the electrode 19a.
[0061]
As described above, while the electrons reciprocate in the discharge space, they frequently collide with the gas particles, so that many excited atoms and the like that contribute to light emission are generated. Therefore, the luminous efficiency is improved as compared with the case where a simple rectangular wave is applied as shown in FIG.
In addition, when a sustain pulse composed of a general rectangular wave is applied, a discharge delay may occur due to a voltage drop at the time of rising. It is considered that this discharge delay occurs because a voltage suddenly starts flowing at the rise of the sustain pulse, causing a voltage drop, and it takes time until the potential rises again.
[0062]
On the other hand, if the reverse polarity pulse is added immediately before the start of the application of the sustain pulse, the electrons reciprocate as described above, so that the collision with the gas particles frequently occurs, and the pilot flame is surely formed. Discharge can be started with high probability, and discharge delay can be suppressed.
Therefore, even if the sustain voltage Vs is set relatively low, the discharge is reliably performed. That is, the sustain voltage Vs in FIG. 11A is set lower than the sustain voltage V in FIG. 11B. Image display is possible.
[0063]
When the maintenance voltage is set to a lower value in this manner, the “current due to ions” can be reduced, and from this point, it can be said that the luminous efficiency is improved compared to the related art.
In order to obtain such an effect, the voltage value of the negative pulse (the voltage indicated by Vmin in FIG. 11A) applied before the rising (the period indicated by Ta in FIG. 11A) is It is preferable to set the absolute value of the voltage to be equal to or greater than the sustain voltage Vs or the discharge start voltage, and it is more preferable to set the absolute value of the voltage to 1.5 times or more.
[0064]
If the period during which the negative pulse is applied prior to the rise (the period indicated by Tb in FIG. 11A) is too long, there may be a problem that power consumption increases due to the current flowing during this period. . In particular, if the period in which the voltage absolute value is larger than the sustain voltage Vs (or the discharge start voltage) (the period indicated by Tc in FIG. 11A) is too long in the period Tb, the current flowing in this period Although the power consumption increases, by setting this to a short time, the increase in the power consumption can be suppressed to a slight level.
[0065]
From such a viewpoint, it is considered necessary to set the application time shorter as the absolute value of the voltage Vmin of the reverse polarity pulse to be applied is set larger. Generally, it is preferable to set this period Tc to 100 ns or less.
For example, when the gap between the scan electrode 19a and the sustain electrode 19b is 60 μm, a negative pulse is applied to the scan electrode 19a at a voltage Vmin (−400 V) before a positive sustain pulse is applied to the scan electrode 19a. In this case, if a negative voltage equal to or higher than the discharge start voltage is applied to the scan electrode 19a so as to convert it to a positive voltage within 100 ns, the charged particles generated in the discharge space by the application of the negative pulse will be applied to the scan electrode 19a. (Or the sustain electrode 19b) The polarity is switched before reaching the sustain electrode 19b, and the current is drawn back toward the opposite sustain electrode 19b (or the scan electrode 19a), so that the current generated during this period is small. In addition, since the charged particles reciprocate between the electrodes in this way, so to speak, a pilot flame is formed. Therefore, when the voltage Vs at the time of applying the pulse of the positive polarity is set to about 200 V, the discharge is reliably performed. The discharge delay does not increase.
[0066]
Further, it is more preferable that the time during which the voltage absolute value is equal to or higher than the discharge starting voltage is set to 50 ns or less in the period in which the negative pulse is applied, since the current flowing in the period can be almost zero. I can say.
(About the circuit that applies a reverse polarity pulse to the sustain pulse)
In order to apply a reverse polarity pulse to the sustain pulse, a pulse synthesis circuit as shown in FIG. 13 may be used for each of the sustain pulse generator 112a and the sustain pulse generator 112b shown in FIGS.
[0067]
FIG. 13 is a block diagram of a pulse synthesis circuit that forms such a pulse waveform.
The pulse synthesizing circuit includes a first pulse generator 131, a second pulse generator 132, and the like.
The first pulse generator 131 generates a negative voltage pulse, and the second pulse generator 132 generates a positive voltage pulse. The first pulse generated by the first pulse generator 131 is a relatively narrow pulse. The second pulse generated by the second pulse generator 132 is a relatively wide rectangular wave.
[0068]
The rising timing of the second pulse is set so as to substantially coincide with the falling of the first pulse.
The first and second pulse generators 131 and 132 are connected in series by a floating ground system so that the output voltages of the first and second pulses are added.
Then, in this pulse synthesizing circuit, in response to the trigger signal sent from the synchronizing pulse generator 103, each pulse generator operates as follows to generate a pulse, and synthesizes the generated pulse and outputs the synthesized pulse. I do.
[0069]
FIG. 14 is a diagram showing how the first pulse and the second pulse are synthesized by the pulse synthesis circuit.
First, a trigger signal is sent from the synchronization pulse generator 103 to the first pulse generator 131, and the first pulse generator 131 raises a first pulse. This first pulse falls in a short time. At substantially the same time, a trigger signal is sent from the synchronous pulse generator 103 to the second pulse generator 132, and the second pulse is raised by the second pulse generator 132. Then, after being output for a while at the voltage of the second pulse, it falls.
[0070]
As a modification of the pulse synthesizing circuit shown in FIG. 13, a first pulse generator 131 and a second pulse generator 132 are connected in parallel to output the larger one of the first pulse and the second pulse. Even in this case, a similar waveform is synthesized.
(About the rising slope of the reverse polarity pulse)
By the way, when the reverse polarity pulse is applied prior to the sustain pulse, if the slope at the rising portion of the reverse polarity pulse is too large, that is, if the applied voltage is changed in a very short time with a large voltage change width, the applied voltage becomes large. There is a tendency for the luminous efficiency to decrease due to the flow of current.
[0071]
Therefore, in order to secure high luminous efficiency, it is considered that the slope of the rising portion of the reverse polarity pulse should be set to a moderate degree. However, if the slope is gradual in the range where the absolute value exceeds the sustain voltage Vs in the rising portion, the effect of suppressing the discharge delay will be impaired.
Considering such points, as in the pulse waveform shown in FIG. 11A, the gradient is set gently in the first half of the rising portion of the reverse polarity pulse to suppress the current, and the gradient is increased in the second half. Is preferred.
[0072]
In order to adjust the slope at the time of the rising of the reverse polarity pulse, the slope of the rising of the first pulse may be adjusted, which may be adjusted by adjusting the time constant of the RLC circuit in the first pulse generator 131. Can be.
[Embodiment 2]
Also in the present embodiment, the characteristics of the sustain pulse applied between scan electrode group 19a and sustain electrode group 19b during the discharge sustain period are the same as in the first embodiment.
[0073]
However, in the first embodiment, in the discharge sustaining period, the voltage is applied to only one of the electrode groups at a moment, that is, when the sustain pulse is applied to the scan electrode group 19a, the sustain electrode group 19b is applied. Shows an example in which no voltage is applied and no voltage is applied to scan electrode group 19a when a sustain pulse is applied to sustain electrode group 19b. However, in the present embodiment, scan electrode group 19a and sustain electrode group 19b are not applied. Are applied, and the combination thereof forms a sustain pulse and a reverse polarity pulse between the scan electrode group 19a and the sustain electrode group 19b.
[0074]
FIG. 15 shows that the sustain pulse generator 112a and the sustain pulse generator 112b apply rectangular pulses of opposite polarities to each of the scan electrode group 19a and the sustain electrode group 19b during the sustain period. 6 is a timing chart showing a state in which a potential difference occurs between the group 19a and the sustain electrode group 19b. In each case, the potential difference waveform (sustain pulse) generated between the scan electrode group 19a and the sustain electrode group 19b is as described above. It has characteristics.
[0075]
In the example of FIG. 15, a rectangular wave pulse (V1) of a positive voltage is applied to the sustaining electrode group 19b for a short time prior to the rising of the rectangular wave of the positive voltage (V2) at the timing of applying the rectangular wave of the positive voltage (V2) to the scanning electrode group 19a. Has been applied. At about the same time as the fall of the pulse applied to the sustain electrode group 19b, a rectangular wave of a positive voltage to the scan electrode group 19a rises. As a result, a negative voltage (-V1) is applied between the scan electrode group 19a and the sustain electrode group 19b in a short time immediately before the positive pulse rises, and thereafter, the positive sustain voltage V2 is applied for a while. You will fall.
[0076]
On the other hand, a rectangular wave pulse (V1) of a positive voltage is applied to the scan electrode group 19a for a short time prior to the leading edge thereof in accordance with the timing at which the rectangular wave of the positive voltage (V2) is applied to the sustain electrode group 19b. I have. At about the same time as the fall of the pulse applied to the scan electrode group 19a, a rectangular wave of a positive voltage to the sustain electrode group 19b rises.
[0077]
As a result, a positive pulse (-V1) is applied between the scan electrode group 19a and the sustain electrode group 19b shortly before the leading edge of the negative sustain pulse, and thereafter, the negative voltage (-V2) is applied for a while. Will be applied.
As described above, in the example of this figure, since the pulses applied to each of the electrode groups 19a and 19b are both rectangular waves, it is not necessary to use the pulse synthesis circuit used in the first embodiment.
[0078]
[Embodiment 3]
As shown in FIG. 16, in the present embodiment, positive sustain pulses are alternately applied to scan electrode group 19a and sustain electrode group 19b during the discharge sustain period, but immediately after the leading edge of each sustain pulse. In a short time, a voltage having a higher voltage absolute value than usual is applied, and a reverse polarity pulse is applied immediately after the trailing edge of the sustain pulse.
[0079]
Hereinafter, the case where the sustain pulse is applied to the scan electrode group 19a will be described in detail, and the case where the sustain pulse is applied to the sustain electrode group 19b is the same.
(Explanation of the effect of the sustain pulse waveform of the present embodiment)
FIG. 17A is an example of a sustain pulse waveform according to the present embodiment. In a positive sustain pulse, a basic portion is a rectangular wave, but is applied after a certain period from the leading edge thereof. A voltage higher than the voltage is applied (second feature), and a negative pulse is applied immediately after the fall of the sustain pulse (third feature). On the other hand, FIG. 17B is an example of a general rectangular wave sustain pulse.
[0080]
The second feature and the third feature may be added independently, and each has the following effects.
Effect of adding the second feature:
When a sustain pulse composed of a simple rectangular wave is applied as shown in FIG. 17 (b), a discharge delay is likely to occur due to a voltage drop at the time of rising. On the other hand, as shown in FIG. When a high voltage is applied for a certain period from the leading edge of the pulse, the above-described voltage drop is suppressed, so that it is possible to avoid an increase in the discharge start delay.
[0081]
Therefore, even if the sustain voltage Vs is set relatively low, the discharge is reliably performed. That is, in the waveform of FIG. 17A, the normal sustain voltage Vs is set to be considerably lower than the waveform of FIG. 17B. However, even if such a waveform is used, the discharge delay increases. However, it is possible to display images satisfactorily.
Thus, when the sustain voltage Vs is set low, it can be said that the luminous efficiency is improved in that the “current due to ions” can be reduced.
[0082]
In order to obtain such an effect, the voltage value (the maximum voltage value indicated by Vmax in FIG. 17A) applied immediately after the start of the rise (the period indicated by Ta in FIG. 17A) is It is preferable that the voltage is set to be equal to or higher than the discharge starting voltage, and set to be 50 V or higher than the “normal sustain voltage” (the voltage value indicated by Vs in FIG. 17A).
[0083]
For a period during which a high voltage is applied (a period during which a voltage equal to or higher than the discharge starting voltage indicated by Tb in FIG. 17A) is applied, if this is set too long, dielectric breakdown will occur even in discharge cells that should not be turned on. May occur, and a problem may arise in that power consumption increases due to current flowing during this period, but by setting this to a short time, dielectric breakdown of the dielectric can be avoided.
[0084]
From such a viewpoint, it is considered that the higher the voltage value Vmax applied immediately after the start of rising, the shorter the application time Tb is required. In general, it is preferable to set the time Tb to 100 ns or less in order to keep the current flowing in the period small, and if the time Tb is set to 10 ns or less, the current flowing in the period is almost zero. Can be said to be more preferable in that
[0085]
In order to obtain a more remarkable effect, it is considered that the voltage value Vmax applied immediately after the start of the rise may be set to a considerably high value of about 400 V. In this case, the time Tb for applying the high voltage is considerably shortened (10 (20 ns or less), it is considered that a circuit performance capable of sharply starting up to a high voltage is required.
[0086]
Effect of adding the third feature:
In the sustain pulse waveform of FIG. 17A, in addition to the second feature, when a positive sustain pulse is applied to the scan electrode group 19a, a reverse polarity (negative) pulse is applied for a short period immediately after the fall. Is applied for a short time.
As shown in FIG. 18A, when a positive sustain pulse is applied to the electrode 19a, the ions generated in the discharge space 20 by the electric field E from the electrode 19a to the electrode 19b are converted to the electrode (positive ion). In this case, it moves toward the electrode 19b).
[0087]
Even after the sustain pulse falls, ions remaining in the discharge space toward the other electrode remain. However, as described above, these ions do not contribute much to light emission. Become.
On the other hand, if a negative pulse is applied immediately after the fall of the sustain pulse (at the time indicated by Tc in FIG. 17A), the electrode goes from the electrode 19b to the electrode 19a as shown in FIG. 18B. Due to the electric field E, ions in the discharge space 20 moving toward the electrode 19b are forcibly repelled without reaching the electrode 19b. Therefore, generation of a reactive current can be suppressed.
[0088]
The voltage value of the reverse polarity (negative) pulse applied immediately after the fall of the sustain pulse (the voltage value indicated by Vmin in FIG. 11A) is also set to have an absolute value of 50 V or more at the maximum, and to apply the voltage. The time is desirably set to 100 ns or less, and more desirably 10 ns or less.
When the third feature is combined with the sustain pulse, since the latter half of the discharge is erased compared to the conventional case, it is considered that the amount of wall charges accumulated at the end of the discharge is reduced. If the amount of wall charges accumulated at the end of the discharge is small, the discharge may not be stably started when the next sustain pulse of the opposite polarity is applied.
[0089]
Therefore, when only the third feature is added to the sustain pulse, it is considered desirable to set the sustain voltage Vs higher in order to secure a stable discharge.
(About the circuit that adds features to the sustain pulse)
In order to apply a waveform having characteristics at the time of rising and falling as a sustain pulse to the scan electrode group 19a and the sustain electrode group 19b, the sustain pulse generator 112a and the sustain pulse generator shown in FIGS. The pulse synthesizing circuit shown in FIG. 19 may be used for each of 112b.
[0090]
FIG. 19 is a block diagram of a pulse synthesis circuit that generates a pulse having such a waveform.
This pulse synthesizing circuit includes a first pulse generator 231, a second pulse generator 232, a third pulse generator 233, and the like that generate a pulse in response to a trigger signal.
[0091]
The first pulse generator 231 and the second pulse generator 232 generate positive voltage pulses, and the voltage of the second pulse is set to the “sustain voltage Vs”.
The first pulse generated by the first pulse generator 231 is a relatively narrow pulse. On the other hand, the second pulse generated by the second pulse generator 232 is a relatively wide rectangular wave.
[0092]
The third pulse generator 233 generates a third pulse having a narrow negative voltage, and the rising timing of the third pulse is set to coincide with the falling of the second pulse. .
The first to third pulse generators 231 to 233 are connected in series by a floating ground system so that the output voltages of the first to third pulses are added.
[0093]
Then, in this pulse synthesizing circuit, in response to the trigger signal sent from the synchronizing pulse generator 103, each pulse generator operates as follows to generate a pulse, and synthesizes the generated pulse and outputs the synthesized pulse. I do.
FIG. 20 is a diagram showing how the first to third pulses are synthesized by the above-described pulse synthesis circuit.
[0094]
First, a trigger signal is sent from the synchronization pulse generator 103 to the first pulse generator 231 and the second pulse generator 232, and the first pulse is generated by the first pulse generator 231 and the second pulse is generated by the second pulse generator 232. The pulses are launched almost simultaneously. Therefore, immediately after the start of the rising, a high voltage obtained by adding the voltage of the first pulse and the voltage of the second pulse is output.
[0095]
Since the first pulse falls in a short time, only the second pulse is output after the first pulse falls.
Then, at the same time as the falling of the second pulse, a trigger signal is sent from the synchronizing pulse generator 103 to the third pulse generator 233, and the third pulse generator 233 causes the third pulse of negative voltage to rise. Then, the third pulse falls in a short time. Therefore, immediately after the falling of the second pulse, a negative pulse is output for a short time.
[0096]
As a result, a waveform as shown in FIG.
In the pulse synthesizing circuit shown in FIG. 19, the synthesizing is performed such that the output voltages of the first to third pulse generators 231 to 233 are added. The pulse generator 231 to the third pulse generator 233 may be connected in parallel to perform pulse synthesis such that the maximum voltage value among the first to third pulses is output.
[0097]
However, in this case, it is necessary to set the voltage value of the first pulse generated by the first pulse generator 231 to be higher than the second pulse by about 50 V or more. Since a pulse having a short time width must be generated, more advanced circuit technology is required.
(About the rising slope of the sustain pulse)
As in the present embodiment, when a sustain pulse is applied, when a voltage higher than the normal sustain voltage is applied for a short time in a short time immediately after the start of the rise, when the voltage is higher than the normal sustain voltage in a short time immediately after the start of the rise. Since a large voltage change width occurs, a large current flows along with this, and the luminous efficiency tends to decrease.
[0098]
Therefore, in order to secure high luminous efficiency, it is considered that the slope of the rising portion should be set to some degree gently. However, if the slope is made gentle within a high voltage range exceeding the normal sustain voltage in the rising portion, the effect of suppressing the discharge delay will be impaired.
Considering such points, it is preferable to set a gentle slope in the first half of the rising portion to suppress the current and increase the slope in the second half, as in the pulse waveform shown in FIG. be able to.
[0099]
Similarly, at the falling edge of the pulse applied with the opposite polarity (Td in FIG. 17A), it is preferable to set the slope to a certain degree so that a large current does not flow.
To adjust the slope of the sustain pulse at the rising edge Ta, the rising slope of the first pulse may be adjusted, or the rising slopes of both the first pulse and the second pulse may be adjusted. The rising slope of the two pulses can be adjusted by adjusting the time constant of the RLC circuit in the first pulse generator 231 and the second pulse generator 232.
[0100]
In addition, in order to adjust the slope at the falling time Td of the reverse polarity pulse, the falling slope of the third pulse may be adjusted by adjusting the time constant of the RLC circuit in the third pulse generator.
(About a modification of the present embodiment)
In FIG. 17A, a waveform is shown in which the applied voltage rises at a stroke to a high voltage equal to or higher than the discharge starting voltage at the rising time Ta of each sustain pulse. The same effect can be obtained by using a waveform that rises and rises to a high voltage with a slight delay.
[0101]
In addition, a modified example as shown in FIG. 21 is also possible.
In this modification, in a positive sustain pulse, a voltage higher than a voltage applied thereafter is applied for a certain period from the leading edge thereof (second characteristic), and a negative pulse is applied immediately after the fall. (Third feature) is the same as FIG. 17A, except that the period of the sustain voltage Vs is considerably short, and the time for applying the negative pulse applied immediately after the fall is long. Their waveforms are also different. That is, in the example of FIG. 19, immediately after the falling of the sustain pulse, the negative voltage Vmin is applied for a short time, and then the weak negative voltage is applied for a relatively long time.
[0102]
Even when such a modified example is used, the luminous efficiency can be similarly improved.
Note that the waveform as in the modified example may occur naturally when a small-capacity power supply (drive circuit) is used, or may occur accidentally depending on a combination of circuits.
[0103]
Further, in the present embodiment, by applying a high voltage immediately after the leading edge of each sustain pulse (second feature) and applying a reverse polarity pulse immediately after the trailing edge (third feature), the effect of both features is achieved. Has been described, but an effect equivalent to that can be obtained by simply adding one of the features to the sustain pulse.
[Embodiment 4]
Also in the present embodiment, the characteristics of the voltage waveform applied between the scan electrode group 19a and the sustain electrode group 19b during the sustain period are the same as in the third embodiment.
[0104]
However, in the third embodiment, when a sustain pulse is applied to scan electrode group 19a, sustain electrode group 19b does not apply a voltage, and when a sustain pulse is applied to sustain electrode group 19b, scan electrode group 19a is applied to scan electrode group 19a. Although an example in which no voltage is applied has been described, in the present embodiment, a pulse is applied to both the scan electrode group 19a and the sustain electrode group 19b, and a combination of the pulse is applied between the scan electrode group 19a and the sustain electrode group 19b. The second and third features are formed in the applied voltage waveform.
[0105]
That is, in each of the timing charts of FIGS. 22 to 24, in the sustaining period, the sustain pulse generator 112a and the sustain pulse generator 112b respectively partially apply the scan electrode group 19a and the sustain electrode group 19b in time. Pulses are applied so as to overlap. As a result, a state in which a potential difference is generated between scan electrode group 19a and sustain electrode group 19b is shown. In any case, a potential difference waveform generated between scan electrode group 19a and sustain electrode group 19b is shown. It can be seen that the above has the second and third features.
[0106]
In the example of FIG. 22, the sustain electrode group 19b has a short time width that rises almost simultaneously with the rise of the rectangular wave pulse in accordance with the timing at which the rectangular wave pulse (V1) of the positive voltage is applied to the scan electrode group 19a. A negative pulse (-V2) and a short-time width positive pulse (V3) that falls almost simultaneously with the fall of the rectangular pulse are applied. As a result, between the scan electrode group 19a and the sustain electrode group 19b, a positive high voltage (V1 + V2) is applied in a short time immediately after the rise, and thereafter, the positive sustain voltage V1 is applied for a while, and the falling voltage is applied. Immediately thereafter, a negative pulse (-V3) is applied for a short time.
[0107]
On the other hand, in synchronism with the timing at which the positive rectangular wave pulse (V1) is applied to the sustain electrode group 19b, the scan electrode group 19a applies a short-time negative pulse (-V2) that rises almost simultaneously with the rise of the rectangular wave pulse. ) And a short-time positive pulse (V3) falling almost simultaneously with the falling of the rectangular pulse.
As a result, a negative high voltage − (V1 + V2) is applied between the scan electrode group 19a and the sustain electrode group 19b in a short time immediately after the rise, and thereafter, the negative sustain voltage V1 is applied for a while. Immediately after the fall, the positive pulse (V3) is applied for a short time.
[0108]
In the example of this figure, since the pulses applied to each of the electrode groups 19a and 19b are both rectangular waves, it is not necessary to use the pulse synthesizing circuit as used in the first embodiment.
In the example of FIG. 23, rectangular wave pulses having substantially the same time width and different voltage values are applied to the scan electrode group 19a and the sustain electrode group 19b so as to temporally overlap. A pulse of high voltage V11 (corresponding to voltage Vmax) is applied to scan electrode group 19a, and low voltage V12 (voltage Vmax) is applied to sustain electrode group 19b by delaying the rising and falling timing for a short time. -Vs) is applied. As a result, a positive high voltage (V11) is applied between the scan electrode group 19a and the sustain electrode group 19b in a short time immediately after the rise, and thereafter, a positive sustain voltage (V11-V12) is applied for a while. Immediately after the fall, a negative pulse (-V12) is applied for a short time.
[0109]
On the other hand, when the pulse of the high voltage V1 is applied to the sustain electrode group 19b, the pulse of the low voltage V2 is applied to the scan electrode group 19a by delaying the rising and falling timing for a short time. As a result, a negative high voltage (-V11) is applied between the scan electrode group 19a and the sustain electrode group 19b in a short time immediately after the rise, and thereafter, a negative sustain voltage (V12-V11) is applied for a while. Immediately after the fall, a positive pulse (V12) is applied for a short time.
[0110]
In the example of this drawing, the sustain pulse generator 112a and the sustain pulse generator 112b do not need to apply a pulse having a short time width as shown in FIG. 22 and need only generate a pulse having a relatively long time width. The circuit performance of starting up sharply to a high voltage is not so required, and the load on the circuit is small.
In the example of FIG. 24, a positive high voltage V21 is applied to the scan electrode group 19a during the period from the time point t1 to the time point t3, and the voltage falls at the time point t3, and during the period from the time point t3 to the time point t4. A positive sustain voltage V22 is applied.
[0111]
On the other hand, a positive pulse V23 is applied to the sustain electrode group 19b during a period from time t2, which is slightly delayed from time t1, to time t3. Here, V23 = V21−V22 is set. Further, a positive pulse V24 is applied to the sustain electrode group 19b in a short period from time t4 to time t5.
As a result, regarding the potential difference between the electrode 19a and the electrode 19b, in the short period of the rising (time t1 to time t2), the positive high voltage V21 is applied, and in the subsequent period (time t2 to time t4). Has a waveform in which a positive sustain voltage V22 (= V21-V23) is applied and a negative pulse (-V24) is applied for a short time in a short time after the fall (time t4 to time t5). I have.
[0112]
From time t6 to time t10, the scan electrode group 19a and the sustain electrode group 19b are switched, and the voltage is applied in the same manner as the time t1 to time t5. As a result, a similar waveform having the opposite polarity is formed between the electrode 19a and the electrode 19b.
In the example of this figure, since the period during which the high voltage V21 is applied to each of the electrodes 19a and 19b is not short and not long as shown in FIG. 12, the sustain pulse generator 112a and the sustain pulse The burden is relatively small.
[0113]
In this example, since V21 = V22 + V23 is set, there is no change in the potential difference between the electrode 19a and the electrode 19b at the time t3. However, it is not always necessary to set in this manner. The same effect is obtained even if the potential difference between the electrode 19a and the electrode 19b slightly changes.
(Variations of Embodiments 1 to 4)
In the first to fourth embodiments, a feature is added to all the sustain pulses in the discharge sustain period. However, when the main purpose is to perform good image display, the feature is not necessarily required in the discharge sustain period. It is not necessary to add a feature to every sustain pulse, and it may be added to some sustain pulses.
[0114]
However, in general, when a plurality of sustain pulses are successively applied during the discharge sustain period, a discharge delay is particularly likely to occur when the first sustain pulse is applied. Since the discharge is easily started even with the sustain pulse of, the above-mentioned feature should be added to at least the first sustain pulse in order to display a good image.
[0115]
For example, the above-described characteristics may be added to the first sustain pulse, and a simple rectangular wave similar to the conventional one may be used for the second and subsequent sustain pulses.
Alternatively, when the positive sustain pulse is applied to the scan electrode group 19a, the above feature is added. When the positive sustain pulse is applied to the sustain electrode group 19b, a simple rectangular wave similar to the related art is used. Is also good.
[0116]
In this case, although the effect of improving the luminous efficiency is inferior to the case where the feature is added to all the sustain pulses, it is considered that the effect of suppressing the discharge delay is almost the same.
In the above-described embodiment, an AC surface discharge type PDP has been described as an example. However, the present invention can be applied to a facing discharge type PDP and has the same effect. In general, a panel display device that writes an image by applying a write pulse and sustains a discharge by applying a sustain pulse to a plurality of discharge cells can be similarly implemented. It works.
[0117]
【The invention's effect】
As described above, according to the present invention, when the sustain pulse is applied, the current waveform is formed such that the fall is completed before the time required for the rise is three times as long as the peak time. Thus, by defining the waveform of the sustain pulse, it is possible to suppress the reactive current and improve the luminous efficiency.
[0118]
Here, the current waveform having the above characteristics can be formed by adding any of the following first to third characteristics to the sustain pulse when applying the sustain pulse.
A first feature is that a pulse having a polarity opposite to that of the sustain pulse is applied for a short time before the leading edge (pulse rise) of the sustain pulse.
The second feature is that the waveform is set so that a higher voltage is applied in a certain period from the leading edge of the sustain pulse (rising edge of the pulse) in absolute value than a voltage applied thereafter.
[0119]
The third feature is that a pulse having a polarity opposite to that of the sustain pulse is applied immediately after the trailing edge (falling pulse) of the sustain pulse.
In addition, when the first characteristic or the second characteristic is added to the sustain pulse, the discharge delay is suppressed.
[Brief description of the drawings]
FIG. 1 is a sketch of an AC surface discharge type PDP according to an embodiment.
FIG. 2 is a view showing an electrode matrix of the PDP.
FIG. 3 is a diagram showing a frame dividing method at the time of driving the PDP.
FIG. 4 is a chart showing a timing of applying a pulse to each electrode in the first embodiment.
FIG. 5 is a block diagram illustrating a configuration of a PDP driving device according to an embodiment.
FIG. 6 is a block diagram illustrating a configuration of a scan driver in FIG. 5;
FIG. 7 is a block diagram illustrating a configuration of a data driver in FIG. 5;
FIG. 8 is a diagram illustrating movement of a current carrier when a sustain pulse is applied.
FIG. 9 is a diagram illustrating a current waveform formed when a sustain pulse is applied.
FIG. 10 is a diagram illustrating a relationship between a current waveform formed when a sustain pulse is applied and luminous efficiency.
FIG. 11 is a diagram showing an example of a sustain pulse waveform according to the first embodiment, and an example of a rectangular wave sustain pulse conventionally used.
FIG. 12 is a diagram illustrating the movement of a current carrier when a sustain pulse is applied.
FIG. 13 is a block diagram of a pulse synthesizing circuit that forms a feature of the sustain pulse according to the first exemplary embodiment;
FIG. 14 is a diagram illustrating a state in which pulses are synthesized by the pulse synthesis circuit.
FIG. 15 is a timing chart showing a state in which a pulse is applied to each electrode during a sustain period in the second embodiment.
FIG. 16 is a chart showing a timing of applying a pulse to each electrode in the third embodiment.
FIG. 17 is a diagram showing an example of a sustain pulse waveform according to the third embodiment, and is an example of a rectangular wave sustain pulse conventionally used.
FIG. 18 is a diagram illustrating movement of a current carrier when a sustain pulse is applied.
FIG. 19 is a block diagram of a pulse synthesizing circuit that forms a feature of a sustain pulse according to the third embodiment;
FIG. 20 is a diagram illustrating a state in which pulses are synthesized by the pulse synthesis circuit.
FIG. 21 is a diagram showing characteristics of a sustain pulse according to a modification of the third embodiment.
FIG. 22 is a chart showing an example of a timing at which a pulse is applied to each electrode during a sustain period in the fourth embodiment.
FIG. 23 is a chart showing an example of a timing at which a pulse is applied to each electrode during a sustain period in the fourth embodiment.
FIG. 24 is a chart showing an example of a timing at which a pulse is applied to each electrode during a sustain period in Embodiment 4.
FIG. 25 is a chart showing a timing of applying a pulse to each electrode in a conventional example.
[Explanation of symbols]
11 Front board
12 Back substrate
13 Dielectric layer
14 Data electrode
15 Partition wall
16 phosphor layer
17 Dielectric layer
18 Protective layer
19a scanning electrode
19b sustain electrode
20 Discharge space
100 drive
112a Sustain pulse generator
112b Sustain pulse generator

Claims (8)

A gas discharge panel in which a plurality of discharge cells are arranged in a matrix between a pair of substrates having sustain electrodes, scan electrodes, and data electrodes ;
A driving circuit for writing an image by applying a write pulse to the plurality of discharge cells and maintaining a discharge by applying a sustain pulse to the plurality of discharge cells; A panel display device for displaying
The drive circuit may further provide different with the sustain pulses of the phase in the same waveform is applied alternately to the sustain electrode and the scan electrodes, a certain period prior to continuous leading edge of at least the beginning of the sustain pulse, and the sustain pulse Wherein a pulse of a potential level preliminarily discharged with a reverse polarity is alternately applied to the sustain electrode and the scan electrode . The opposite polarity of the pulse driving circuit is applied to the discharge cell, to the sustain pulse voltage, the panel display device according to claim 1, wherein the absolute value is 1.0 times or more. 3. The panel display according to claim 2, wherein a period during which the absolute value is 1.0 times or more of the sustain pulse voltage is 100 ns or less in a period in which the driving circuit applies the pulse of the opposite polarity. apparatus. 3. The panel display according to claim 2, wherein a period during which the absolute value of the sustain pulse voltage is 1.0 times or more of the sustain pulse voltage is 50 ns or less during a period in which the drive circuit applies the pulse of the opposite polarity. apparatus. The opposite polarity of the pulse driving circuit is applied to the discharge cells, the panel display device according to claim 1, wherein the absolute value with respect to sustain pulse voltage is 1.5 times or more. A gas discharge panel in which a plurality of discharge cells are arranged in a matrix between a pair of substrates;
A driving circuit for writing an image by applying a write pulse to the plurality of discharge cells and maintaining a discharge by applying a sustain pulse to the plurality of discharge cells; A panel display device that displays an image,
At least the first sustain pulse applied to the discharge cells by the driving circuit is
The voltage in a certain period from the leading edge of the sustain pulse has a higher absolute value than the voltage in a period from the elapse of the certain period to the trailing edge of the sustain pulse, and the absolute value is higher than the discharge start voltage of the discharge cell, The voltage applied to the discharge cell during the period from the elapse of the certain period to the trailing edge of the sustain pulse is lower than the discharge start voltage of the discharge cell in absolute value, and the time for applying the voltage higher than the discharge start voltage is 100 ns. A panel display device characterized by the following . The driving circuit further includes:
7. The panel display device according to claim 6 , wherein a pulse having a polarity opposite to that of the sustain pulse is applied to the discharge cells for a predetermined period from a trailing edge of each sustain pulse. 8. The panel display device according to claim 7, wherein the driving circuit applies a pulse of a reverse polarity to the discharge cell for 100 ns or less.

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