Abstract:
A method and apparatus for driving a plasma display panel for preventing and a spot misfire and a miswriting is disclosed. In the method, wall charges are formed at a discharge cell in an initial period. The discharge cell selects discharge cells in an address period. A wall charge control period is arranged between said initialization period and said address period. A wall charge distribution at the discharge cell is controlled in the wall charge control period. A sustain discharge is caused at discharge cells selected in said address period in the sustain period.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a plasma display panel, and more particularly to a method and apparatus for driving a plasma display panel that is adaptive for preventing and a spot misfire and a miswriting. 
     2. Description of the Related Art 
     Generally, a plasma display panel (PDP) excites and radiates a phosphorus material using an ultraviolet ray generated upon discharge of an inactive mixture gas such as He+Xe, Ne+Xe or He+Ne+Xe, to thereby display a picture. Such a PDP is easy to be made into a thin-film and large-dimension type. Moreover, the PDP provides a very improved picture quality owing to a recent technical development. 
     Referring to  FIG. 1 , a discharge cell of a conventional three-electrode, AC surface-discharge PDP includes a scan electrode  30 Y and a sustain electrode  30 Z provided on an upper substrate  10 , and an address electrode  20 X provided on a lower substrate  18 . Each of the scan electrode  30 Y and the sustain electrode  30 Z includes transparent electrodes  12 Y and  12 Z, and metal bus electrodes  13 Y and  13 Z having smaller line widths than the transparent electrodes  12 Y and  12 Z and provided at one edge of the transparent electrodes  12 Y and  12 Z. 
     The transparent electrodes  12 Y and  12 Z are usually formed from indium-tin-oxide (ITO) on the upper substrate  10 . The metal bus electrodes  13 Y and  13 Z are usually formed from a metal such as chrome (Cr), etc. on the transparent electrodes  12 Y and  12 Z to thereby reduce a voltage drop caused by the transparent electrodes  12 Y and  12 Z having a high resistance. 
     On the upper substrate  10  provided, in parallel, with the scan electrode  30 Y and the common sustain electrode  30 Z, an upper dielectric layer  14  and a protective film  16  are disposed. Wall charges generated upon plasma discharge are accumulated onto the upper dielectric layer  14 . The protective film  16  prevents a damage of the upper dielectric layer  14  caused by a sputtering during the plasma discharge and improves the emission efficiency of secondary electrons. This protective film  16  is usually made from magnesium oxide (MgO). 
     A lower dielectric layer  22  and barrier ribs  24  are formed on the lower substrate  18  provided with the address electrode  20 X. The surfaces of the lower dielectric layer  22  and the barrier ribs  24  are coated with a phosphorous material  26 . The address electrode  20 X is formed in a direction crossing the scan electrode  30 Y and the sustain electrode  30 Z. The barrier rib  24  is formed in parallel to the address electrode  20 X to thereby prevent an ultraviolet ray and a visible light generated by a discharge from being leaked to the adjacent discharge cells. The phosphorous material  26  is excited by an ultraviolet ray generated during the plasma discharge to generate any one of red, green and blue visible light rays. An inactive mixture gas for a gas discharge is injected into a discharge space defined between the upper and lower substrate  10  and  18  and the barrier rib  24 . 
     Such a PDP makes a time-divisional driving of one frame, which is divided into various sub-fields having a different emission frequency, so as to realize gray levels of a picture. Each sub-field is again divided into an initialization period for initializing the entire field, an address period for selecting a scan line and selecting the cell from the selected scan line and a sustain period for expressing gray levels depending on the discharge frequency. Herein, the initialization period is again divided into a set-up interval supplied with a rising ramp waveform and a set-down interval supplied with a falling ramp waveform. 
     For instance, when it is intended to display a picture of 256 gray levels, a frame interval equal to 1/60 second (i.e. 16.67 msec) is divided into 8 sub-fields SF 1  to SF 8  as shown in  FIG. 2 . Each of the 8 sub-field SF 1  to SF 8  is divided into an initialization period, an address period and a sustain period as mentioned above. Herein, the initialization period and the address period of each sub-field are equal for each sub-field, whereas the sustain period and the number of sustain pulses assigned thereto are increased at a ratio of 2 n  (wherein n=0, 1, 2, 3, 4, 5, 6 and 7) at each sub-field. 
       FIG. 3  shows a driving waveform of the PDP applied to two sub-fields. In  FIG. 3 , Y represents the scan electrode; Z does the sustain electrode; and X does the address electrode. 
     Referring to  FIG. 3 , the PDP is divided into an initialization period for initializing the full field, an address period for selecting a cell, and a sustain period for sustaining a discharge of the selected cell for its driving. 
     In the initialization period, a rising ramp waveform Ramp-up is simultaneously applied to the entire scan electrodes Y in a set-up interval. This rising ramp waveform Ramp-up causes a weak discharge within cells at the full field to generate wall charges within the cells. The rising ramp waveform Ramp-up rises from a sustain voltage Vs until a sum value of a set-up voltage Vsetup with the sustain voltage Vs. 
     In the set-down interval, after the rising ramp waveform Ramp-up was supplied, a falling ramp waveform Ramp-down falling from a positive voltage lower than a peak voltage of the rising ramp waveform Ramp-up is simultaneously applied to the scan electrodes Y. The falling ramp waveform Ramp-down causes a weak erasure discharge within the cells, to thereby erase spurious charges of wall charges and space charges generated by the set-up discharge and uniformly leave wall charges required for the address discharge within the cells of the full field. In real, the falling ramp waveform Ramp-down falls from the sustain voltage Vs until a negative voltage −Vy so that desired wall charges can be left during the set-down interval. 
     In the address period, a negative scanning pulse scan is sequentially applied to the scan electrodes Y and, at the same time, a positive data pulse data is applied to the address electrodes X. A voltage difference between the scanning pulse scan and the data pulse data is added to a wall voltage generated in the initialization period to thereby generate an address discharge within the cells supplied with the data pulse data. Wall charges are formed within the cells selected by the address discharge. 
     Meanwhile, a positive direct current voltage having a sustain voltage level Vs is applied to the sustain electrodes Z during the set-down interval and the address period. 
     In the sustain period, a sustaining pulse sus is alternately applied to the scan electrodes Y and the sustain electrodes Z. Then, a wall voltage within the cell selected by the address discharge is added to the sustain pulse sus to thereby generate a sustain discharge taking a surface-discharge type between the scan electrode Y and the common sustain electrode Z whenever each sustain pulse sus is applied. Finally, after the sustain discharge was finished, a erasing ramp waveform erase having a small pulse width is applied to the sustain electrode Z to thereby erase wall charges left within the cells. 
     In the set-up interval of such a convention PDP, the scan electrode Y is supplied with a positive voltage while the sustain electrode Z is supplied with a negative voltage (or a ground voltage). Accordingly, in the set-up interval, negative wall charges are formed at the scan electrode Y while positive wall charges are formed at the sustain electrode Z as shown in  FIG. 4 . The falling ramp waveform Ramp-down falling from a positive voltage lower than a peak voltage of the rising ramp waveform Ramp-up are supplied in the set-down interval. Thus, spurious wall charges formed excessively and non-uniformly are erased to thereby reduce the wall charges within the cell into a predetermined amount. 
     Subsequently, in the address period, the scan electrode Y is supplied with a negative voltage while the sustain electrode Z is supplied with a positive voltage. At this time, a voltage value (having a negative polarity) of wall charges formed in the set-down interval is added to a negative voltage value applied to the scan electrode Y, to thereby cause an address discharge. 
     The conventional PDP driven as mentioned above does not make a stable address discharge until desired wall charges are formed in the initialization period. However, in the conventional PDP, desired wall charges are not formed in the initialization period depending upon a property of the panel, and thus a spot misfire or a miswriting occurs. 
     More specifically, when wall charges are normally formed in the initialization period, negative wall charges are formed at the scan electrode Y while positive wall charges are formed at the sustain electrode Z as shown in  FIG. 4 . However, due to problems of the panel property, etc., positive wall charges are formed at the scan electrode Y of a portion of discharge cells during the set-down interval as shown in  FIG. 5 . In other words, the falling ramp waveform Ramp-down falls until a negative voltage −Vy in the set-down interval. At this time, positive wall charges are formed at the scan electrode Y provided at the portion of discharge cells. If positive wall charges are formed at the scan electrode Y as mentioned above, then a spot misfire or a miswriting is generated to thereby cause a deterioration of picture quality in the PDP. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the present invention to provide a method and apparatus for driving a plasma display panel that is adaptive for preventing and a spot misfire and a miswriting. 
     In order to achieve these and other objects of the invention, a method of driving a plasma display panel according to one aspect of the present invention includes an initial period for forming wall charges at a discharge cell; an address period for selecting the discharge cell; a wall charge control period, being arranged between said initialization period and said address period, for controlling a wall charge distribution at the discharge cell; and a sustain period for causing a sustain discharge at discharge cells selected in said address period. 
     In the method, said initialization period is divided into a set-up interval and a set-down interval; a rising ramp, waveform rising at a first slope from a sustain voltage until a sum value of said sustain voltage and a set-up voltage; and a falling ramp waveform falling at a second slope from said sustain voltage until a negative voltage. 
     A control pulse having a voltage rising at said first slope from a ground voltage is applied to the scan electrode during said wall charge control period. 
     Herein, a voltage of said control pulse is a voltage less than said set-up voltage. 
     An application time of said control pulse is differentiated depending upon sub-fields. 
     Herein, an application time of said control pulse is set more shortly as it goes from a sub-field arranged in an initial time of a frame into the last sub-field of the frame. 
     Alternatively, an application time of said control pulse is set longer as it goes from a sub-field arranged in an initial time of a frame into the last sub-field of the frame. 
     Application time of said control pulse is equal to each other at the entire sub-fields included in one frame. 
     A ground voltage is applied to a sustain electrode arranged in parallel to the scan electrode during said wall charge control period. 
     A control pulse rising at a slope different from said first slope from a ground voltage is applied to the scan electrode during wall charge control period. 
     Alternatively, a rectangular control pulse having said sustain voltage is applied to the scan electrode during said wall charge control period. 
     Herein, said control pulse is applied during a time less than 1 μs. 
     An application time of said control pulse is differentiated depending upon sub-fields. 
     Application time of said control pulse is equal to each other at the entire sub-fields included in one frame. 
     A ground voltage is applied to a sustain electrode arranged in parallel to the scan electrode during said wall charge control period. 
     A driving apparatus for a plasma display panel according to another aspect of the present invention includes a set-up supplier for supplying a rising ramp waveform to scan electrodes during an initialization period; and a scan voltage supplier for sequentially supplying a scanning pulse to the scan electrodes during an address period, wherein the set-up supplier applies a control pulse rising at the same slope as said rising ramp waveform to the scan electrodes between said initialization period and said address period. 
     Herein, after said control pulse was supplied, a ground voltage is applied to the scan electrodes. 
     A driving apparatus for a plasma display panel according to still another aspect of the present invention includes a set-up supplier for supplying a rising ramp waveform to scan electrodes during an initialization period; a scan voltage supplier for sequentially supplying a scanning pulse to the scan electrodes during an address period; an energy recovering circuit for supplying a sustaining pulse having a sustain voltage during a sustain period; and a scan reference voltage supplier for supplying a scan reference voltage to the remaining scan electrodes other than said scan electrodes to which said scanning pulse is applied during said address period, wherein said energy recovering circuit applies a rectangular control pulse having said sustain voltage to the scan electrodes between said initialization period and said address period. 
     In the driving apparatus, prior to said control pulse was supplied, said scan reference voltage is applied to the scan electrodes. 
     Said control pulse is applied during a time less than 1 μs. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other objects of the invention will be apparent from the following detailed description of the embodiments of the present invention with reference to the accompanying drawings, in which: 
         FIG. 1  is a perspective view showing a discharge cell structure of a conventional three-electrode, AC surface-discharge plasma display panel; 
         FIG. 2  illustrates sub-fields included in one frame of the conventional plasma display panel; 
         FIG. 3  is a waveform diagram of driving signals supplied to the electrodes during the sub-fields shown in  FIG. 2 ; 
         FIG. 4  depicts wall charges formed at the electrodes in the initialization period shown in  FIG. 2 ; 
         FIG. 5  depicts wall charges formed at a portion of discharge cells in the initialization period shown in  FIG. 2 ; 
         FIG. 6  is a waveform diagram for explaining a method of driving a plasma display panel according to a first embodiment of the present invention; 
         FIG. 7  is a circuit diagram of a driving apparatus for the plasma display panel according to an embodiment of the present invention; and 
         FIG. 8  is a waveform diagram for explaining a method of driving a plasma display panel according to a first embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       FIG. 6  shows a method of driving a plasma display panel (PDP) according to a first embodiment of the present invention. 
     Referring to  FIG. 6 , the PDP according to the first embodiment of the present invention is divided into an initialization period for initializing the entire field, a wall charge control period for preventing an inversion of wall charges, an address period for selecting a cell and a sustain period for sustaining a discharge of the selected cell for its driving. 
     In the initialization period, a rising ramp waveform Ramp-up is simultaneously applied to all of scan electrodes Y in a set-up interval. This rising ramp waveform Ramp-up causes a weak discharge within cells at the full field to generate wall charges within the cells. The rising ramp waveform Ramp-up rises from a sustain voltage Vs until a sum value of a set-up voltage Vsetup with the sustain voltage Vs. 
     In the set-down interval, after the rising ramp waveform Ramp-up was supplied, a falling ramp waveform Ramp-down falling from a positive voltage lower than a peak voltage of the rising ramp waveform Ramp-up is simultaneously applied to the scan electrodes Y. The falling ramp waveform Ramp-down causes a weak erasure discharge within the cells, to thereby erase spurious charges of wall charges and space charges generated by the set-up discharge and uniformly leave wall charges required for the address discharge within the cells of the full field. In real, the falling ramp waveform Ramp-down falls from the sustain voltage Vs until a negative voltage −Vy so that desired wall charges can be left during the set-down interval. 
     In the wall charge control period, the scan electrodes Y are supplied with a positive control pulse Ramp-p rising from a ground voltage GND until a set-up voltage Vsetup. If the positive control pulse Ramp-p is applied to the scan electrodes Y, then a fine discharge is generated at the discharge cells to thereby control the polarities of the discharge cells into desired types. 
     More specifically, in the set-down interval, wall charges having an undesired type of polarities are formed at a portion of discharge cells as shown in  FIG. 5 . Thereafter, if the positive control pulse Ramp-p is applied to the scan electrodes Y, then a fine discharge is generated at the discharge cells to thereby form negative wall charges at the scan electrodes Y while forming positive wall charges at the sustain electrodes Z. In other words, in the embodiment of the present invention, the polarities of wall charges of the entire discharge cells can be controlled into desired polarities during the wall charge control period. 
     Meanwhile, an application time of the control pulse Ramp-p can be set in various methods. For instance, an application time of the control pulse Ramp-p may be set equally or differently for each sub-field. Herein, if an application time of the control pulse Ramp-p is set differently for each sub-field, then a voltage value of the control pulse Ramp-p also is set differently for each sub-field. In other words, an application time of the control pulse Ramp-p rising at the same slope is controlled, so that the control pulse Ramp-p having a different voltage value can be applied to each sub-field. Herein, an application time of the control pulse may be set to be shorter as it goes from the initial sub-field into the later sub-fields. Then, as it goes from the initial sub-field into the later sub-fields, a voltage value of the control pulse becomes lower. Alternatively, an application of the control pulse may be set to be longer as it goes from the initial sub-field into the later sub-fields. In real, an application time of the control pulse is experimentally determined in consideration of a length (i.e., inch) of the panel, a resolution of the panel and a process state, etc. Otherwise, the control pulse Ramp-p having different slope and/or voltage for each sub-field may be supplied. 
     In the address period, a negative scanning pulse scan is sequentially applied to the scan electrodes Y and, at the same time, a positive data pulse data is applied to the address electrodes X. A voltage difference between the scanning pulse scan and the data pulse data is added to a wall voltage generated in the initialization period to thereby generate an address discharge within the cells supplied with the data pulse data. Wall charges are formed within the cells selected by the address discharge. In the above-mentioned embodiment of the present invention, negative wall charges are formed at the scan electrodes of the entire discharge cells during the wall charge control period to thereby cause a stable address discharge. Accordingly, it becomes possible to prevent a miswriting and/or a spot misfire. 
     Meanwhile, a positive direct current voltage having a sustain voltage level Vs is applied to the sustain electrodes Z during the set-down interval and the address period. Further, in the wall charge control period, the sustain electrodes Z are supplied with a ground voltage GND. The sustain electrodes Z are supplied with the ground voltage GND during the wall charge control period to thereby cause a stable intensified discharge. 
     In the sustain period, a sustaining pulse sus is alternately applied to the scan electrodes Y and the sustain electrodes Z. Then, a wall voltage within the cell selected by the address discharge is added to the sustain pulse sus to thereby generate a sustain discharge taking a surface-discharge type between the scan electrode Y and the common sustain electrode Z whenever each sustain pulse sus is applied. Finally, after the sustain discharge was finished, an erasing ramp waveform erase having a small pulse width is applied to the sustain electrode Z to thereby erase wall charges left within the cells. 
       FIG. 7  shows a scan electrode driver according to an embodiment of the present invention. 
     Referring to  FIG. 7 , the scan electrode driver includes an energy recovering circuit  41 , a fourth switch Q 4  connected between the energy recovering circuit  41  and a driving integrated circuit (IC)  42 , a negative scan voltage supplier  43  and a scan reference voltage supplier  44  connected between the fourth switch Q 4  and the driving IC  42  to apply a scanning pulse Scan, and a set-up supplier  45  connected among the fourth switch Q 4 , the negative scan voltage supplier  43  and the scan reference voltage supplier  44  to generate a rising ramp waveform Ramp-up. 
     The driving IC  42  is connected in a push-pull shape, and consists of tenth and eleventh switches Q 10  and Q 11  to which voltage signals from the energy recovering circuit  41 , the scan voltage supplier  43  and the scan reference voltage supplier  44  are inputted. An output line between the tenth and eleventh switches Q 10  and Q 11  are connected to any one of scan electrode lines Y 1  to Ym. 
     The energy recovering circuit  41  includes an external capacitor CexY for charging an energy recovered from the scan electrode lines Y 1  to Ym, switches Q 14  and Q 15  connected, in parallel, to the external capacitor CexY, an inductor Ly connected between a first node n 1  and a second node n 2 , a first switch Q 1  connected between a sustain voltage supply Vs and the second node n 2 , and a second switch Q 2  connected between the second node n 2  and a ground voltage terminal GND. 
     An operation of the energy recovering circuit  41  will be described below. 
     First, it is assumed that a Vs/2 voltage has been charged in the external capacitor CexY. If the fourteenth switch Q 14  is turned on, then a voltage charged in the external capacitor CexY is applied, via the fourth switch Q 14 , a first diode D 1 , the inductor Ly and the fourth switch Q 4 , to the driving IC  42  and, at the same time, is applied, via an internal diode (not shown), to the scan electrode lines Y 1  to Ym. At this time, the inductor Ly configures a serial LC resonance circuit along with a capacitance C of the cell of the PDP to thereby apply a resonating waveform to the scan electrode lines Y 1  to Ym. 
     The first switch Q 1  is turned on at a resonance point of the resonating waveform. If the first switch Q 1  is turned on, then the sustain voltage Vs is applied, via the first switch Q 1  and the driving IC  42 , to the scan electrode lines Y 1  to Ym. During the time interval when voltages on the scan electrode lines Y 1  to Ym are charged and discharged by such an operation of the energy recovering circuit  41 , the fourth switch Q 4  keeps an ON state so as to form a current path between the energy recovering circuit  41  and the driving IC  42 . 
     The energy recovering circuit  41  recovers an energy from the PDP and then applies a voltage to the scan electrode lines Y 1  to Ym using the recovered energy, thereby reducing an excessive power consumption upon discharging in the set-up interval and in the sustain period. 
     The negative scan voltage supplier  43  consists of a sixth switch Q 6  connected between a third node n 3  and a scan voltage source −Vy. The sixth switches Q 6  is switched in response to a control signal yw from a timing controller (not shown) during the address period to thereby apply a scan voltage −Vy to the driving IC n 4 . 
     The scan reference voltage supplier  44  consists of an eighth switch Q 8  connected between a scan reference voltage source Vsc and a fourth node n 4 . The eighth switch Q 8  is switched in response to a control signal SCW from the timing controller (not shown) to thereby apply the scan reference voltage Vsc to the driving IC  42 . 
     The set-up supplier  45  consists of a fourth diode D 4  and a third switch Q 3  connected between a set-up voltage source Vsetup and a third node n 3 . The fourth diode D 4  shuts off a backward current flowing from the third node n 3  into the set-up voltage source Vsetup. The third switch Q 3  is switched in response to a control signal setup from the timing controller (not shown) to thereby apply a rising ramp waveform Ramp-up having a slope determined by a RC time constant value to the third node n 3 . 
     A procedure in which a control pulse Ramp-p is supplied from the scan electrode driver of the present invention will be described below. 
     First, since a control signal set-up is applied via a first variable resistor R 1 , a channel width of the third switch Q 3  is controlled by a resistance value of the first variable resistor R 1 . In real, a channel width of the third switch Q 3  is controlled by a capacitance value of a capacitor or a parasitic capacitor (not shown) and a RC time constant of the first variable resistor R 1 . 
     Accordingly, a control pulse Ramp-p supplied via the third switch Q 3  at a predetermined slope (i.e., the same slope as the rising ramp waveform) is applied, via the third node n 3 , to the driving IC  42 . The control pulse Ramp-p applied to the driving IC  42  is applied, via the driving IC  42 , to the scan electrode Y. If the control pulse Ramp-p is applied to the scan electrode Y, then an intensified discharge is generated at the discharge cells to thereby form negative wall charges at the entire scan electrodes Y. After the control pulse Ramp-p was applied to the scan electrodes Y, the second switch Q 2  is turned on. If the second switch Q 2  is turned on, then a ground voltage GND is applied to the scan electrodes Y. 
     Such an embodiment of the present invention can apply the control pulse Ramp-p with the aid of the set-up supplier  45  for supplying the rising ramp waveform without any additional circuit for supplying the control pulse Ramp-p. 
       FIG. 8  shows a method of driving a plasma display panel (PDP) according to a second embodiment of the present invention. 
     Referring to  FIG. 8 , the PDP according to the second embodiment of the present invention is divided into an initialization period for initializing the entire field, a wall charge control period for preventing an inversion of wall charges, an address period for selecting a cell and a sustain period for sustaining a discharge of the selected cell for its driving. 
     In the initialization period, a rising ramp waveform Ramp-up is simultaneously applied to all of scan electrodes Y in a set-up interval. This rising ramp waveform Ramp-up causes a weak discharge within cells at the full field to generate wall charges within the cells. The rising ramp waveform Ramp-up rises from a sustain voltage Vs until a sum value of a set-up voltage Vsetup with the sustain voltage Vs. 
     In the set-down interval, after the rising ramp waveform Ramp-up was supplied, a falling ramp waveform Ramp-down falling from a positive voltage lower than a peak voltage of the rising ramp waveform Ramp-up is simultaneously applied to the scan electrodes Y. The falling ramp waveform Ramp-down causes a weak erasure discharge within the cells, to thereby erase spurious charges of wall charges and space charges generated by the set-up discharge and uniformly leave wall charges required for the address discharge within the cells of the full field. In real, the falling ramp waveform Ramp-down falls from the sustain voltage Vs until a negative voltage −Vy so that desired wall charges can be left during the set-down interval. 
     In the wall charge control period, the scan electrodes Y are supplied with a rectangular control pulse pp rising from a ground voltage GND until a sustain voltage Vs. If the rectangular control pulse pp is applied to the scan electrodes Y, then a discharge is generated at the discharge cells to thereby control the polarities of the discharge cells into desired types. 
     More specifically, in the set-down interval, wall charges having an undesired type of polarities are formed at a portion of discharge cells as shown in  FIG. 5 . Thereafter, if the rectangular control pulse pp is applied to the scan electrodes Y, then a discharge is generated at the discharge cells to thereby form negative wall charges at the scan electrodes Y while forming positive wall charges at the sustain electrodes Z. In other words, in the embodiment of the present invention, the polarities of wall charges of the entire discharge cells can be controlled into desired polarities during the wall charge control period. 
     Meanwhile, an application time of the control pulse pp is set within 1 μs. For instance, an application time of the control pulse pp may be set more shortly as it goes from the initial sub-field into the later sub-fields. Alternatively, an application time of the control pulse pp may be set longer as it goes from the initial sub-field into the later sub-fields. In real, an application time of the control pulse pp is experimentally determined in consideration of a length (i.e., inch) of the panel, a resolution of the panel and a process state, etc. Further, a scan reference voltage Vsc is applied to the scan electrode Y prior to an application of the control pulse pp. 
     In the address period, a negative scanning pulse scan is sequentially applied to the scan electrodes Y and, at the same time, a positive data pulse data is applied to the address electrodes X. A voltage difference between the scanning pulse scan and the data pulse data is added to a wall voltage generated in the initialization period to thereby generate an address discharge within the cells supplied with the data pulse data. Wall charges are formed within the cells selected by the address discharge. In the above-mentioned embodiment of the present invention, negative wall charges are formed at the scan electrodes Y of the entire discharge cells during the wall charge control period to thereby cause a stable address discharge. Accordingly, it becomes possible to prevent a miswriting and/or a spot misfire. 
     Meanwhile, a positive direct current voltage having a sustain voltage level Vs is applied to the sustain electrodes Z during the set-down interval and the address period. Further, in the wall charge control period, the sustain electrodes Z are supplied with a ground voltage GND. The sustain electrodes Z are supplied with the ground voltage GND during the wall charge control period to thereby cause a stable intensified discharge. 
     In the sustain period, a sustaining pulse sus is alternately applied to the scan electrodes Y and the sustain electrodes Z. Then, a wall voltage within the cell selected by the address discharge is added to the sustain pulse sus to thereby generate a sustain discharge taking a surface-discharge type between the scan electrode Y and the common sustain electrode Z whenever each sustain pulse sus is applied. Finally, after the sustain discharge was finished, an erasing ramp waveform erase having a small pulse width is applied to the sustain electrode Z to thereby erase wall charges left within the cells. 
     In the mean time, in  FIG. 8 , the control pulse pp can be supplied by means of the scan electrode driver shown in  FIG. 7 . This will be described with reference to  FIG. 7  below. 
     First, an eighth switch Q 8  is turned on during the wall charge control period to thereby apply a scan reference voltage Vsc to the scan electrodes Y. Thereafter, a second switch Q 2  is turned on, to thereby apply a ground voltage GND to the scan electrodes Y. After the ground voltage GND was applied to the scan electrodes Y, a first switch Q 1  is switched (e.g., during a time less than 1 μs), to thereby apply a control pulse pp having a sustain voltage level Vs to the scan electrodes Y. Thereafter, the ground voltage GND, the scan reference voltage Vs and a scan voltage −Vr are applied to the scan electrodes Y, to thereby cause an address discharge. 
     As described above, according to the present invention, a control pulse is applied after the reset period to thereby prevent an inversion phenomenon of wall charges. In other words, a positive control pulse is applied to the scan electrodes after the reset period to thereby form negative wall charges at the entire scan electrodes. Accordingly, it becomes possible to generate a stable address discharge and thus to prevent a miswriting and a spot misfire. 
     Although the present invention has been explained by the embodiments shown in the drawings described above, it should be understood to the ordinary skilled person in the art that the invention is not limited to the embodiments, but rather that various changes or modifications thereof are possible without departing from the spirit of the invention. Accordingly, the scope of the invention shall be determined only by the appended claims and their equivalents.