JP4178832B2 - Plasma display device and driving method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a plasma display device that performs display using high-frequency discharge and a driving method thereof.
[0002]
[Prior art]
The plasma display panel (PDP) is a display that can cope with thin and large screens that are difficult to achieve with a cathode ray tube (CRT) that has been widely used in television receivers and computer displays. It has attracted attention, and large displays of 40 inches or more have already been commercialized.
[0003]
The display panel of the PDP has a structure in which two glass substrates are bonded together. A pair of sustain electrodes is formed on the front glass substrate, and a data electrode is formed on the rear glass substrate in a direction intersecting with the sustain electrodes. Each matrix is arranged to form a matrix, and each intersection is a pixel. The light emission control is generally composed of three types of operation periods of a reset period, an address period, and a sustain (discharge sustaining) period. The selective erasing method will be described as an example. In the reset period, all the pixels are discharged, and wall charges are uniformly formed on the entire screen. In the address period, each pixel is selectively selected according to light emission / non-light emission. Discharging is performed to erase wall charges from a predetermined pixel, and a display pixel is selected. In the next sustain period, an AC pulse voltage (sustain pulse) is applied to the sustain electrode pairs of all the pixels, and discharge is generated and maintained only in the pixels in which wall charges are formed. Visible light is emitted when the vacuum ultraviolet rays generated during the sustain discharge excite phosphors provided in each pixel to emit light.
[0004]
The sustain pulse applied for the sustain discharge conventionally has a frequency of 200 to 300 kHz and a width of about 10 to 20 μs. However, the discharge per sustain pulse occurs instantaneously in a very short period, and most of the other time is spent on wall charge formation and the preparation stage of the next discharge. Therefore, in the conventional AC type PDP, the luminance and the light emission efficiency are low, and improvement of these has been a big problem.
[0005]
In order to solve the problem, in recent years, attempts have been made to improve the light emission efficiency by introducing a radio frequency (RF) pulse of several hundred MHz as a sustain pulse. For example, Japanese Patent Application Laid-Open No. 2000-322023 discloses a high frequency discharge type PDP panel having a cell structure as shown in FIG. This panel has a three-electrode structure as shown in FIG. 10, and each discharge cell has an intersection of a data electrode 116 (X _{1 to} X _m ), a scanning electrode 120 (Y _{1 to} Y _n ), and a high-frequency electrode 112 (RF). It is located in the part and is indicated by hatching in the figure. In this panel, an RF pulse is supplied to the high-frequency electrode (common electrode) 112. The data electrode 116 is supplied with a data pulse for selecting a cell to be displayed. The scan electrode 120 is supplied with a scan pulse for panel scanning. The scanning electrode 120 is also used as a counter electrode for the high-frequency electrode 112.
[0006]
Taking this panel as an example, the light emission mechanism in high frequency discharge will be described. When an RF signal whose polarity is continuously alternated is applied to one of the high-frequency electrode 112 and the scanning electrode 120 facing each other in the cell, electrons in the discharge space are caused to move to the electrode or Move to the other electrode. Here, if a positive RF signal is applied to the high-frequency electrode 112, the electrons are accelerated toward the high-frequency electrode 112. Therefore, if the polarity of the RF signal is changed to the negative polarity before the electrons reach the high-frequency electrode 112, the electrons are gradually decelerated and finally move toward the opposite scanning electrode 120.
[0007]
In this way, if the polarity of the RF signal applied to the electrodes is changed before the electrons reach the electrodes, the electrons oscillate between the two electrodes. Thereby, while a high frequency signal is applied, ionization, excitation, and transition of gas particles occur continuously without annihilation of electrons. Such a high frequency discharge has the same physical characteristics as the positive column in the glow discharge structure. Therefore, the discharge is sustained for most of the sustain discharge period, and the brightness and discharge efficiency of the PDP are improved. By the way, when a PDP having an RF electrode as shown in FIG. 9 was produced and an RF pulse was introduced, the luminous efficiency was about 10 (lm / W), which was about 10 times that of the conventional AC pulse drive. (J. Kang et al; IDW'99 Proceedings, PDPp1-19, pp691-694, 1999).
[0008]
The discharge cell of the high-frequency discharge type PDP having such a configuration can be driven by the drive waveforms shown in FIGS. 11 (A) to (C), for example. An RF signal (RFS) is continuously supplied to the high-frequency electrode 112. When charged particles or the like are not present in the discharge space, no discharge occurs even when an RF signal is supplied to the high-frequency electrode 112. When the data signal (DS) is supplied to the data electrode 116 and the scan signal (SS) is supplied to the scan electrode 120 in the address period (AP), an address discharge is generated. Among the charged particles generated by the address discharge, electrons having relatively high mobility move in amplitude between the high-frequency electrode 112 and the scan electrode 120 by the RF signal during the discharge sustain period (SP). Visible light is generated by the vibrating electrons exciting the discharge gas to generate vacuum ultraviolet light, which causes the phosphor to emit light. The high frequency discharge is maintained for the discharge sustain period, and then stopped by the erase signal (ES) supplied to either the data electrode 116 or the scan electrode 120 in the erase period (EP). That is, when an erasing signal is supplied, electrons that are oscillating are attracted to the scanning electrode 120 and disappear.
[0009]
In this way, the RF signal is continuously applied to the high-frequency electrode 112, the ON display pixel is selected by the data signal DS, and the display ON / OFF is reset by the erasing signal ES. Therefore, in this case, the address period (AP), the discharge sustain period (SP), and the erase period (EP) constitute one light emission control period. The gradation display is performed.
[0010]
[Problems to be solved by the invention]
A major problem in driving a high-frequency discharge type PDP is how to supply an RF signal to the high-frequency electrode. The RF signal must be supplied uniformly and uniformly to a plurality of high-frequency electrodes arranged in parallel. However, the panel originally has capacity. When high-frequency discharge occurs, a current path is generated between the high-frequency electrode that causes high-frequency discharge and the scan electrode, and the distance between the two electrodes that determine the capacity is narrowed. For this reason, the phenomenon that the capacity of the panel increases occurs. As a result, the impedance of the panel is reduced, the RF signal is absorbed (passed) in the panel, and the power of the RF signal applied to the panel is finally reduced.
[0011]
Therefore, power is supplied by providing a matching circuit in the subsequent stage of the high frequency power supply. When the impedance of the high frequency power supply is the same as the impedance of the panel (input to the common electrode), the RF signal with the maximum power is supplied. Therefore, if impedance matching is performed, the RF signal with the maximum power can be supplied and the panel can be driven stably. Actually, the panel is supplied with the power of the signal in which the incident wave and the reflected wave are superimposed. Taking impedance matching by the matching circuit minimizes the reflected wave and the incident wave is supplied to the panel as it is. Is to do so.
[0012]
However, the matching circuit itself has variations in individual characteristics, and the input-side impedance for each high-frequency electrode varies depending on the wiring length between the electrode and the matching circuit. Therefore, there is a problem that it is difficult to supply the maximum power to all the electrodes in the same way. This phenomenon is due to the fact that the higher the frequency and the larger the panel size, the closer the wavelength of the applied signal and the circuit size become, so the difference in circuit impedance greatly affects the signal size (amplitude). Thus, the voltage fluctuation for each electrode appears as luminance unevenness or non-uniformity of the display image in the entire panel.
[0013]
Therefore, in the past, the impedance was corrected by adjusting the constant of each matching circuit so that the signal amplitude was the maximum and the same at any electrode. However, such adjustment is complicated and depends on the number of circuits to be adjusted. Was a factor in increasing costs.
[0014]
The present invention has been made in view of such problems, and an object thereof is to provide a plasma display device and a driving method thereof that can easily improve luminance unevenness.
[0015]
[Means for Solving the Problems]
The plasma display device of the present invention performs display by generating a counter discharge with high frequency in a cell, and includes a display panel provided with a plurality of high frequency electrodes for applying a high frequency signal of several hundred MHz, and a high frequency signal. And fluctuating high frequency generating means for generating the frequency so as to fluctuate with time.
[0016]
The driving method of the plasma display device of the present invention is a method of driving the above-mentioned plasma display device of the present invention, wherein a high-frequency signal whose frequency fluctuates with time is generated by a variable high-frequency generating means, and this high-frequency signal is used as a high-frequency electrode. Is applied to the display panel to perform light emission display.
[0017]
In the plasma display device and the driving method thereof according to the present invention, a high-frequency signal whose frequency fluctuates with time is temporally applied to each high-frequency electrode due to a difference in impedance in each transmission circuit system from the signal supply side to each high-frequency electrode. The signal varies in amplitude.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0019]
FIG. 1 is a block diagram showing a configuration of a high-frequency signal system of a plasma display device according to an embodiment of the present invention. This plasma display device is driven by a high-frequency signal whose frequency varies with time.
[0020]
A plurality of X electrodes 12 are provided in parallel on the panel 10, and a high frequency signal output from the high frequency power supply unit 20 is supplied to these X electrodes 12 via a power amplifier 23 and a matching circuit 24. It has come to be. The other elements of the panel 10 may be configured in any way. For example, a Y electrode and a data electrode constituting an nxm matrix are further provided to form a three-electrode structure similar to the conventional one. In that case, for example, a drive unit that supplies a scan pulse and a data pulse is connected to each of the Y electrode and the data electrode, for example, as usual, and is configured to write data to each pixel.
[0021]
The high-frequency power supply unit 20 is a supply source of a high-frequency signal whose frequency fluctuates with time. Here, the high-frequency power supply unit 20 includes a signal generator 21 and a VCO (Voltage Controlled Oscillator) 22. That is, the VCO 22 displaces the frequency of the output signal, and the amount of displacement is controlled by the signal waveform from the signal generator 21. The signal generator 21 generates a signal waveform that varies evenly within a predetermined voltage range, such as a triangular wave or a random waveform. The VCO 22 generates and outputs a high-frequency signal that varies evenly within a predetermined frequency range using this waveform as a frequency displacement amount.
[0022]
When the output signal of the signal generator 21 is a triangular wave as shown in FIG. 2, the VCO 22 generates a high-frequency signal as shown in FIG. 3 (B) using this waveform as a frequency displacement amount as shown in FIG. 3 (A). ·Output. Here, the amplitude range V1-V2 of the triangular wave corresponds to the frequency range f1-f2 of the high-frequency signal. Frequency range f1-f2 is basically determined by the displacement amount relative to the specified value f _0. The amount of displacement is set in consideration of variations in the characteristics of the matching circuit 24, but is appropriately set in consideration of variations in the length of the signal supply line with respect to each X electrode 12.
[0023]
The matching circuit 24 is for supplying a high-frequency signal having the maximum power (maximum amplitude) to the X electrode 12. The matching circuit 24 may be any type, and the wiring method for this is arbitrary. For example, a plurality of X electrodes 12 can be arranged in a distributed manner, and when a plurality of matching circuits 24 are used in this way, usually, there is a characteristic between them. There is a variation on the top. In any case, the impedance difference caused by the difference in wiring length between the matching circuit 24 and the X electrode 12 is generated as long as the wiring length varies. Therefore, in this plasma display device, the signal system impedance corresponding to each X electrode 12 varies. Furthermore, the signal system for each X electrode 12 has a different signal frequency at which impedance matching is appropriately performed due to the variation in impedance.
[0024]
In this plasma display device, the signal generator 21 generates a voltage signal for controlling the frequency fluctuation value and outputs it to the VCO 22. The VCO 22 modulates the frequency based on the input voltage signal to generate a high frequency signal and outputs it to the power amplifier 23. The high frequency signal is amplified by the power amplifier 23, adjusted by the matching circuit 24 so that the power becomes maximum, and transmitted to each X electrode 12. At this time, in each signal system for each X electrode 12, impedance matching is performed in consideration of the frequency of the high-frequency signal and the impedance of the signal system. That is, in the signal system in which the signal frequency matches the appropriate frequency, impedance matching is successfully performed, and the high frequency signal is transmitted to the X electrode 12 with the maximum amplitude. As the signal frequency is shifted from the appropriate frequency, the amplitude of the high-frequency signal transmitted without matching becomes smaller.
[0025]
However, here, in order to change the frequency of the high-frequency signal with time, the signal system (X electrode 12) that can be matched well varies depending on the frequency. In other words, if the frequency of the high frequency signal is matched with the variation in the appropriate frequency of the signal system, matching can be achieved for any signal system for a certain period of time. As a result, the amplitude of the high-frequency signal transmitted to the X electrode 12 varies with time so as to always include the maximum amplitude with respect to any X electrode 12. The amplitude change in the direction in which 12 is arranged (vertical direction) is also spatially leveled. In this way, the dispersion of the impedance of the signal system with respect to the amplitude of the high-frequency signal is temporally dispersed, so that the influence can be evenly distributed on the screen. Therefore, the luminance unevenness is averaged and reduced in the display.
[0026]
Next, the above operation will be described more specifically based on an embodiment.
[0027]
FIG. 4 shows an example of an equivalent circuit of a high-frequency signal system in this plasma display device. Here, a matching circuit 24 (24A to 24C) is provided for each X electrode 12 (12A to 12C). Matching circuit 24A~24C, respectively, the inductor L ₁₁ ~L _13, is configured as a T-type circuit having an inductor L ₂₁ ~L ₂₃ and capacitor C ₁₁ -C _13. In addition, the circuit configuration may be a π type or the like. Further, each of the X electrodes 12A - 12C, the resistor R ₁ to R _3, the inductor L ₃₁ ~L _33, and a capacitor C ₂₁ -C _23. These constants of the X electrode 12 are expressed as the load of the panel 10 including the resistance of the electrode 12, the wiring resistance between the matching circuit 24 and the X electrode 12, the capacitance of the panel 10, and the like.
[0028]
In this equivalent circuit, the above-described impedance difference is expressed as a difference in circuit constants in at least one of the matching circuits 24A to 24C and the X electrodes 12A to 12C. Here, the impedance variation is mainly due to the wiring length between the matching circuit 24 and the X electrode 12. Further, since the wiring length is considered to change with the distribution depending on the position of the X electrode 12 on the panel 10, the impedances of the X electrodes 12A to 12C are set to be large, medium, and small from above, A simulation was performed for a case where a signal whose frequency varies was supplied from the power supply unit 20.
[0029]
5 to 7 are voltage waveform diagrams of the X electrodes 12A to 12C when high frequency signals having different frequencies (f1 to f3) are applied. Here, f1 <f2 <f3, and the actual frequency range is about 15 MHz to 20 MHz for simulation.
[0030]
As can be seen from the figure, when the signal frequency changes from f1 to f2 to f3, the X electrode 12 to which a signal is applied with a large amplitude changes accordingly (12A → 12B → 12C). When this is expressed in terms of luminance, it is as shown in FIGS. At each point of time f1, f2, and f3, the screen has brightness unevenness as usual, but the brightness unevenness distribution state is different. As this changes from (A) → (B) → (C) as the signal frequency changes, the luminance unevenness is temporally dispersed and averaged.
[0031]
As described above, according to the present embodiment, since the light emission display of the panel 10 is performed using the high-frequency signal whose frequency fluctuates with time, the X electrodes 12 are matched according to their proper proper frequencies. On the screen of the panel 10, the luminance unevenness distribution changes over time. Therefore, the luminance unevenness is reduced by making the distribution inconspicuous, and the image quality can be improved.
[0032]
In order to completely suppress uneven brightness, matching circuit constants and the wiring length between the matching circuit and the X electrode must be made uniform as in the past, and adjustment of the matching circuit and ingenuity of the wiring method are required. Necessary. Even if this can be done, it is not possible to completely eliminate other factors of luminance variation such as panel capacity variation, discharge state variation, and display time difference for each pixel. On the other hand, the present embodiment tries to eliminate the luminance unevenness by dispersing and averaging, and it is possible to simultaneously expect all the above effects. In the same way, it is also possible to expect variations in the matching circuit 24 and the panel 10 for each device. Of course, it is not necessary to adjust the characteristics of the individual matching circuits 24.
[0033]
In addition, this invention is not limited to the said embodiment and Example, A various deformation | transformation implementation is possible. For example, in the embodiment, the case where the signal frequency is changed from f1 → f2 → f3 has been described. However, since the signal frequency may be changed so as to be uniformly distributed between f1 and f3, the frequency fluctuation is random. As long as the frequency values are evenly distributed within this range, the increase / decrease may be changed in any way. In the embodiment, the frequency fluctuation follows a triangular wave, which is one specific example, but the frequency fluctuation may follow another function.
[0034]
The specific circuit configurations of the high-frequency power supply unit and the matching circuit are not limited to those described in the embodiment, and various modifications can be made.
[0035]
In the above embodiment, the electrode to which the high-frequency signal is applied is described as only the X electrode 12. However, since the feature of the present invention is the waveform of the high-frequency signal supplied to the electrode, which is the basic driving method? The present invention may be applied, and can also be applied to a case where a high frequency signal is applied to a counter electrode such as a Y electrode.
[0036]
【The invention's effect】
As described above, according to the plasma display device and the driving method thereof according to the present invention, by generating a high-frequency signal whose frequency fluctuates with time by the variable high-frequency generating means, and applying this high-frequency signal to the high-frequency electrode, Since light emission display is performed on the display panel, luminance unevenness or luminance non-uniformity on the display screen is dispersed and averaged according to the frequency variation of the high-frequency signal. Therefore, it is not necessary to correct variations in circuit constants such as wiring lengths in high-frequency electrodes or the like by adjusting the impedance matching circuit as in the prior art, and the image quality can be easily improved. In addition, the labor and costs associated with the adjustment of the matching circuit are eliminated, and the cost can be greatly reduced. Furthermore, according to the present invention, it is possible to reduce luminance unevenness or non-uniformity in consideration of not only impedance variation within one device but also variation between devices.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a main configuration of a plasma display device according to an embodiment of the present invention.
FIG. 2 is a diagram showing an output signal waveform of a signal generator of the plasma display device shown in FIG.
3A and 3B are diagrams showing output signal waveforms of a voltage controlled oscillator of the plasma display device shown in FIG. 1, wherein FIG. 3A shows the frequency fluctuation and FIG. 3B shows the actual voltage fluctuation.
4 is an equivalent circuit diagram of the high-frequency signal system shown in FIG. 1. FIG.
5 is a voltage waveform diagram for each X electrode when a high frequency with a low frequency is applied in the equivalent circuit shown in FIG. 4; FIG.
6 is a voltage waveform diagram for each X electrode when a high frequency of an intermediate frequency is applied in the equivalent circuit shown in FIG. 4;
7 is a voltage waveform diagram for each X electrode when a high frequency high frequency is applied in the equivalent circuit shown in FIG. 4; FIG.
8A and 8B are diagrams illustrating luminance unevenness in simulation in the equivalent circuit illustrated in FIG. 4, and FIGS. 8A to 8C are screens when high-frequency signals having different frequencies are applied, respectively.
FIG. 9 is a perspective view showing a main part of a conventional high-frequency plasma display device.
10 is an electrode layout diagram of the plasma display device shown in FIG. 9;
11 is a diagram for explaining a driving method of the plasma display device shown in FIG. 9;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Panel, 12, 12A-12C ... X electrode, 20 ... High frequency power supply part, 21 ... Signal generator, 22 ... VCO, 23 ... Power amplifier, 24, 24A-24C ... Matching circuit.

Claims (9)

A plasma display device for performing display by generating a counter discharge with high frequency in a cell ,
A display panel provided with a plurality of high-frequency electrodes for applying a high-frequency signal of several hundred MHz ;
Optionally Help plasma display device and a fluctuation frequency generating means for generating such a frequency that varies with time the frequency signal. The frequency of the high frequency signal, the plasma display device 請 Motomeko 1, wherein that will be evenly distributed in a predetermined frequency range. The fluctuation high frequency generation means includes a signal generator that generates a voltage signal corresponding to a frequency fluctuation, and a voltage controlled oscillator that generates a high frequency signal by changing the frequency according to the change of the voltage signal. the plasma display device of 請 Motomeko 1, wherein that. The signal generator is a plasma display device 請 Motomeko 3 wherein that generates a triangular wave. The signal generator is a plasma display device 請 Motomeko 3 wherein that generates a random signal. Several hundred MHz and a display panel high-frequency electrode is provided with a plurality of applying high-frequency signal of the a fluctuation high frequency generating means for frequency RF signal is generated to vary temporally, a high frequency by an opposite discharge within the cell A method of driving a plasma display device that performs display by generating
It said frequency generates a high frequency signal varying temporally by changes frequency generation means, by applying a high-frequency signal to the high-frequency electrode, a driving method of a light emitting display in the display panel row Upu plasma display device. The high frequency signal of the frequency driving method of evenly distributed so Ru請 Motomeko 6, wherein at a predetermined frequency range. The high frequency signal of the frequency, time series driving method of 請 Motomeko 7, wherein Ru is varied as represented by a triangular wave. Wherein the frequency of the high-frequency signal, driving method of randomly Ru varied 請 Motomeko 6 wherein.

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