Abstract:
A driving method of a plasma display panel and a driving circuit thereof are disclosed. In the method, image data is inputted by applying a scanning pulse to the scanning electrode and selectively applying a data pulse to the data electrode during an address period. Then, a first pulse and a second pulse of different phase are respectively applied to the first sustaining electrode and the second sustaining electrode during a sustain period. A third pulse is applied to the scanning electrode to sustain the image data. A first discharge current and a second discharge current are occurred, an time interval is formed between the discharge currents to reduce an instant power consumption of the PDP. The driving method is also used to reduce the electromagnetic interference and increases the operation margin.

Description:
This application incorporates by reference Taiwanese application Serial No. 90100657, filed Jan. 11, 2001. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a driving method for a plasma display panel (hereinafter referred to as PDP) and a circuit thereof, particularly to a driving method for reducing a voltage difference of the sustaining electrode and circuit thereof. 
     2. Description of the Related Art 
     Please refer to FIG. 1, it shows a cross-sectional view of a conventional PDP structure. There are several sustaining electrodes X and scanning electrodes Y alternately disposed on the surface of the front glass substrate  102  and are parallel to each other. Each of the sustaining electrode X or scanning electrode Y comprises a transparent electrode  106  and an auxiliary electrode  108 . The auxiliary electrode  108  is used to increase the conductivity of the transparent electrode  106 . A dielectric layer  110  is positioned on the transparent electrode  106  and the auxiliary electrode  108 , and a protective layer  112  covers the dielectric layer  110 . 
     A plurality of address electrodes  114 , which are perpendicular to the sustaining electrodes X and the scanning electrodes Y, are positioned on the surface of the rear glass substrate  104 . Each address electrode  114  is formed below a fluorescent layer  116  and ribs (not shown in FIG.  1 ). The discharge space  118  is formed between the protective layer  112  and the fluorescent layer  116 . The discharge space is filled with discharge gas, for instance, inert gases. 
     Referring to FIG. 2, it is the diagram of the electrode arrangement of the conventional PDP. The sustaining electrode X and the scanning electrode Y are alternately disposed, that is, these electrodes are arranged by the order of scanning electrode Y( 1 ), sustaining electrode X( 1 ), scanning electrode Y( 2 ) and sustaining electrode X( 2 ). The address electrodes A( 1 ), A( 2 ), A( 3 ) and A( 4 ) are perpendicular to the sustaining electrodes X and the scanning electrodes Y. Each discharge cell E 1 , can be turned on and off, is defined by the sustaining electrode X, scanning electrode Y and address electrode A. 
     Referring to FIG. 3, it is the diagram showing another electrode arrangement of the conventional PDP. The sustaining electrode X and the scanning electrode Y are arranged by the order of YXXY, that is, the electrodes are arranged by the order of the scanning electrode Y( 1 ), sustaining electrode X( 1 ), sustaining electrode X( 2 ) and the scanning electrode Y( 2 ). The address electrode A( 1 ), A( 2 ), A( 3 ) and A( 4 ) are perpendicular to the sustaining electrodes X and the scanning electrodes Y. Each discharge element E 2 , can be selectively turned on and off, is defined by each sustaining electrode X, scanning electrode Y and address electrode A. 
     Referring to FIG. 4, it is the diagram of the driving waveform for driving the conventional PDP in FIG. 2 or FIG.  3 . In this driving method, there are three periods in each subfield, including a reset period P 1 , an address period P 2 , and a sustain period P 3 . The following description is the operation of a PDP having n sustaining electrodes X( 1 )˜X(n), n scanning electrodes Y( 1 )˜Y(n) and m address electrodes A( 1 )˜A(m). 
     To make sure that the data can be addressed correctly in the pixels, in the reset period P 1 , a priming pulse  402  of 340V is applied to the sustaining electrodes X( 1 )˜X(n), and an erase pulse  404  with a positive voltage, a reset pulse  406  with a negative voltage and a stabilizing priming pulse  408  are sequentially applied to the scanning electrodes Y( 1 )˜Y(n). The wall charges of the discharge cells are reset to a certain energy state by the pulses described above. Those pulses also reduce the ionized charges in the discharge space  118 . 
     During the address period P 2 , lots of scanning pulses  410  of −180V are inputted to the scanning electrodes Y( 1 )˜Y(n). A voltage V 1 , about 60V, is applied to the sustaining electrodes X( 1 )˜X(n). According to the image data to be displayed, the address pulse  412  of 60V is selectively inputted to the address electrodes A( 1 )˜A(m) for producing wall charges. Therefore, the wall charges can be increased in the selected discharge cells, and are used as the initial charges for a subsequent sustain period P 3 . 
     During the sustain period P 3 , the discharge cells emit UV light and the user will see visible light as UV photons hit the fluorescent layer  116 . By the memory effect of the wall charges, the discharge cells are lighted after applying an alternating current with opposite polarities to the scanning electrodes Y( 1 )˜Y(n) and the sustain electrodes X( 1 )˜X(n). The signals applied to the scanning electrodes Y( 1 )˜Y(n) and the sustain electrodes X( 1 )˜X(n), are in a range between 180V and 0V, and these signals include a plurality of discharge sustaining pulse  414 . 
     Please refer to FIG. 5 which is a block diagram of the circuit and used to drive the conventional PDP in FIG. 2 or FIG.  3 . Take n=8 as an example. The Y driving circuit  502  includes a reset/scan circuit  504  and a Y sustaining circuit  506 . The reset/scan circuit  504  should provide at lease one signal with a positive voltage and one signal with a negative voltage, so the reset/scan circuit  504  is a positive/negative polarity circuit. During the reset period P 1  or the address period P 2 , the reset/scan circuit  504  provides signals with voltages of 180V, −90V or −180V to the scanning electrodes Y. During the sustain period P 3 , the sustaining circuit  506  provides signals with voltages of 180V or 0V to the scanning electrodes Y. During the address period P 2  and the sustain period P 3 , the Y driving circuit  502  provides the signals to the multiplexer  508  and the scanning IC  510  which is electrically connected to all of the scanning electrodes Y( 1 )˜Y( 8 ). The scanning IC  510  sequentially outputs the scanning pulse  410  to the scanning electrodes Y( 1 )˜Y( 8 ) during the address period P 2 , and simultaneously provides discharge sustaining pulses  414  to the scanning electrode Y( 1 )˜Y( 8 ) during the sustain period P 3 . Moreover, all of the sustaining electrodes X are coupled to the X driving circuit  514 . The X driving circuit  514  includes a reset circuit  516  and a X sustaining circuit  512 . The reset circuit  516  only provides signals with a positive voltage, so the reset circuit  516  is a positive polarity circuit. 
     Referring to FIG. 6, it shows the current IX of the sustaining electrode X, and the voltage of the sustaining electrode X and the scanning electrode Y during the sustain period P 3  in FIG.  4 . After the discharge sustaining pulse  414  is applied, the discharge cell is discharged, and a current Ids will pass through the sustaining electrode X, scanning electrode Y, X sustaining circuit  512  and Y sustaining circuit  506 . The X sustaining circuit  512  and the Y sustaining circuit  506  include a lot of transistors, every transistor has its resistance, and the total resistance of these transistors is defined as Rds. When the current Ids is formed, a voltage difference V=Ids*Rds is occurred within a very short time because of the resistances Rds of these transistors. When the electric current flows out of one electrode, the voltage difference V is negative, and a notch may appear in the voltage waveform of the electrode. When the electric current flows in the electrode, the voltage difference V is positive, and a peak may appear in the voltage waveform of the electrode. In addition, whether a notch or a peak is formed may depend on the signals applied on these electrodes. When the sustaining electrode X is in a positive voltage (e.g. 180V) and the scanning electrode is in a relative negative voltage (e.g. 0V), the instant voltage difference V cause a voltage notch  602   a  in the voltage waveforms of the sustaining electrode X and a peak  602   b  in the voltage waveforms of the scanning electrode Y. The voltage difference V can be as higher as 60V. Therefore, the actual voltage waveforms of the sustaining electrode X and the scanning electrode Y are different from these of the inputted signals of the driving circuits. The voltage operation margin of the PDP is then reduced, and the electromagnetic radiation interference (EMI) becomes seriously when the notch or the peak is formed. 
     U.S. Pat. No. 6,072,449 discloses a method for driving the PDP and a method can reduce the instant voltage difference V. The voltage and the current waveforms for the sustaining electrode X and the scanning electrode Y are shown in FIG.  7 . First, the scanning electrodes Y are divided to two groups including first scanning electrodes Y 1  and second scanning electrodes Y 2 . Take a first scanning electrode Y 1  and a second scanning electrode Y 2  as the example, the discharge sustaining pulses with different phases are applied, respectively. Therefore, on the sustaining electrode X, the displacement current  702  caused by the voltage difference of the first scanning electrode Y 1 , the displacement current  702 ′ caused by the voltage difference of the sustaining electrode X, the discharge current  704  of the sustaining electrode X and the first scanning electrode Y 1 , the displacement current  706  caused by the voltage difference of the second scanning electrode Y 2 , and the discharge current  708  of the sustaining electrode X and the second scanning electrode Y 2  will appear at different times. Therefore, the discharge currents  704 ,  708  become smaller. According to the above-mentioned equation V=Ids*Rds, the instant voltage difference can be reduced when the current is reduced. The voltage notches  710 ,  712  or peaks  714 ,  716  formed by the instant voltage difference V can also be reduced. However, the circuit is very complex, and thereby the cost is very high. 
     Referring to FIG. 8, it shows the block diagram of the driving circuit to produce the waveform in FIG.  7 . The first scanning electrode Y 1  and the second scanning circuit Y 2  are respectively coupled to the scanning IC  810  and the scanning IC  820 . There are many transistors in the Y driving circuit  802 , so the scanning ICs  810 ,  820  can&#39;t couple to only one Y driving circuit  802 . Every scanning IC must couple to a corresponding Y driving circuit to output a different driving waveform. Therefore, the scanning ICs  810  and  820  are respectively coupled to the Y driving circuits  802  and  812  through the multiplexer  808  and  818 . The Y driving circuit  802  includes a reset/scan circuit  804  and a Y sustaining circuit  806 , and the Y driving circuit  812  includes a reset/scan circuit  814  and a Y sustaining circuit  816 . The reset/scan circuits  804 ,  814  are negative/positive polarity reset circuits. A X driving circuit  826  includes a reset circuit  828  and a X sustaining circuit  824 . Moreover, the Y driving circuits  802  and  812  respectively receive control signals C_Y( 1 ) and the C_Y( 2 ) from the phase shift controller  822  to produce different discharge sustaining pulses. The phase shift controller  822  further transmits one control signal C_X( 1 ) to the X sustaining circuit  824  to maintain the synchronization of the sustaining circuit  806 ,  816  and  824 . However, there are so many components in the above-mentioned circuit, the prior circuit would be very complicated and the manufacturing cost is high. 
     SUMMARY OF THE INVENTION 
     From the above description, the object of the present invention is to provide a driving method of a Plasma Display Panel (PDP)and circuit thereof. The driving method and circuit of the PDP reduces the voltage difference effectively and increases the operation margin. Especially, the driving method reduces the electromagnetic interference of the PDP efficiently. The object of the present invention is achieved with only a simple circuit. 
     According to the object of the present invention, a driving method of the PDP is disclosed. The PDP includes a first sustaining electrode, a second sustaining electrode, a scanning electrode and a data electrode. The scanning electrode is parallel to the first sustain electrode and the second sustain electrode. The data electrode is perpendicular to the first sustaining electrode. The driving method includes steps of: (a) providing an address period, (b) applying a scanning pulse to the scanning electrode during the address period and selectively applying a data pulse to the data electrode for writing in an image data, (c) providing a sustain period, and (d) applying a first pulse and a second pulse with different phases to the first sustaining electrode and the second sustaining electrode, and applying a third pulse to the scanning electrode for maintaining the image data. The first pulse and the second pulse produce a first discharge current and a second discharge current on the first sustaining electrode and the second sustaining electrode, and an time interval is formed between the second discharge current and the first discharge current to reduce an instant power consumption of the PDP. 
     According to another object of the present invention, a PDP driving circuit is also disclosed. The PDP includes a scanning electrode, a first sustaining electrode, a second sustaining electrode and a data electrode. The scanning electrode is parallel to the first sustain electrode and the second sustain electrode. The data electrode is perpendicular to the first sustaining electrode. The driving circuit of the PDP includes a Y driving circuit, a scanning IC, a first X sustaining circuit, a second X sustaining circuit and a phase shift controller. The scanning IC is coupled to the scanning electrode and the Y driving circuit. The first X sustaining circuit is coupled to the first sustaining electrode X 1 , and the second X sustaining circuit is coupled to the second sustaining electrode X 2 . The phase shift controller is coupled to the first X sustaining circuit and the second X sustaining circuit, the phase shift controller is commanded the first X sustaining circuit and the second X sustaining circuit to output a first and a second pulse, and the first and second pulse are in different phases. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above objects and other advantages of the present invention will become more apparently by describing in detail the preferred embodiment of the present invention with reference to the attached drawings in which: 
     FIG. 1 is the cross section showing the conventional structure of a Plasma Display Panel (PDP); 
     FIG. 2 is the diagram of the electrode arrangement for the YXYX-type according to the conventional PDP; 
     FIG. 3 is the diagram of the electrode arrangement for the YXXY-type according to the conventional PDP; 
     FIG. 4 is the diagram of the driving waveform used to drive the conventional PDP in FIG. 2 or FIG. 3; 
     FIG. 5 is the block diagram of the circuit used to drive the conventional PDP in FIG. 2 or FIG. 3; 
     FIG. 6 shows the waveforms of the current IX for the sustaining electrode X and the voltage for the sustaining electrode X and the scanning electrode Y during the sustain period P 3  in FIG. 4; 
     FIG. 7 shows the voltage and the current waveforms for the sustaining electrode X and the scanning electrode Y according to the method for driving the PDP in U.S. Pat. No. 6,072,449; 
     FIG. 8 shows the block diagram of a circuit for forming the waveform in FIG. 7; 
     FIG. 9 shows the current waveforms of the first sustaining electrode X 1 , the second sustaining electrode X 2 , the first scanning electrode Y 1  and the second scanning electrode Y 2  according to the preferred embodiment in the present invention; 
     FIG. 10 shows the block diagram of a driving circuit used for a PDP having the YXYX-type electrode arrangement according to the preferred embodiment in the present invention; 
     FIG. 11 shows block diagram of a driving circuit used for a PDP having the YXXY-type electrode arrangement according to the preferred the embodiment in the present invention; 
     FIG. 12A shows a part of the X sustaining circuit according to the conventional method in FIG. 8; 
     FIG. 12B shows a part of the first X sustaining circuit according to the driving circuit of FIG. 10 in the present invention; 
     FIG. 13 shows the enlargement of a part of the waveform in FIG. 9; 
     FIG. 14 shows the sustain discharge waveform according to the second embodiment in the present invention; and 
     FIG. 15 shows block diagram of a driving circuit using two different scanning ICs. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In the present invention, the sustaining electrodes X are divided into two groups, including the first sustaining electrodes X 1  and the second sustaining electrodes X 2 . The scanning electrodes Y are also divided into two groups including the first scanning electrodes Y 1  and the second electrodes Y 2 . Take a first sustaining electrode, a second sustaining electrode, a first scanning electrode, and a second scanning electrode as the example in the follow description. 
     During the sustain period P 3 , the first and second discharge sustaining pulses with different phases are applied to the first sustaining electrode X 1  and the second sustaining electrode X 2 , respectively. The third discharge sustaining pulse is applied to the first scanning electrode Y 1  and the second scanning electrode Y 2 . Thus, the first discharge current and the second discharge current are outputted from the first sustaining electrode X 1  and the second sustaining electrode X 2 . The second discharge current appears after the first discharge current for a delay time. The instant power consumption of the PDP is reduced and the voltage differences (notches or peaks) of the first sustaining electrode X 1 , the second sustaining electrode X 2 , the first scanning electrode Y 1  and the second scanning electrode Y 2  are also reduced. 
     Referring to FIG. 9, it shows the voltage and current waveforms of the first sustaining electrode X 1 , the second sustaining electrode X 2 , the first scanning electrode Y 1  and the second scanning electrode Y 2  in the preferred embodiment. Several sustaining signals IN_Y 1 , IN_Y 2 , IN_X 1  and IN_X 2  are inputted from the outer circuits (not shown) to the first scanning electrode Y 1 , the second scanning electrode Y 2 , the first sustaining electrode X 1 , the second sustaining electrode X 2 , respectively. Then, the voltage waveforms of the first scanning electrode Y 1 , the second scanning electrode Y 2 , the first sustaining electrode X 1 , the second sustaining electrode X 2  are shown as VY 1 , VY 2 , VX 1 , VX 2 . The current waveforms of the first scanning electrode Y 1 , the second scanning electrode Y 2 , the first sustaining electrode X 1 , the second sustaining electrode X 2  are shown as IY 1 , IY 2 , IX 1 , IX 2 , respectively. 
     In FIG. 9, the first discharge sustaining pulse  902  applied to the first sustaining electrode X 1  and the second discharge sustaining pulse  904  applied to the second sustaining electrode X 2  have different phases. Therefore, the first rising edge  906  of the first discharge sustaining pulse  902  and the second rising edge  908  of the second discharge sustaining pulse  904  are staggered. The first rising edge  906  appears before the falling edge  912  of the third discharge sustaining pulse  910 . The second rising edge  908  appears after the falling edge  912  of the third discharge sustaining pulse  910 . The third discharge sustaining pulse  910  is the signal inputted to the first scanning electrode Y 1  and the second scanning electrode Y 2 . 
     As voltage differences of the first sustaining electrode X 1  and the first scanning electrode Y 1  happen, first displacement currents  922  and  924  are generated. A first discharge current  926  will appear when the voltage difference between the first sustaining electrode X 1  and the first scanning electrode Y 1  is larger than a threshold voltage. Moreover, as voltage differences of the second sustaining electrode X 2  and the second scanning electrode Y 2  happen, second displacement currents  932  and  934  appear. A second discharge current  936  will be generated if the voltage difference between the second sustaining electrode X 2  and the second scanning electrode Y 2  is larger than the threshold voltage. 
     The first discharging current  926  and the second discharging current  936  are staggered because the phases of the first sustain discharging pulse  902  and the second sustain discharging pulse  904  are different. A delay time D 1  is formed between the second discharging current  936  and the first discharging current  926 . Therefore, the instant power consumption of the PDP can be reduced. The voltage differences (notches or peaks)  940 ,  942 ,  946 ,  948  of the first sustaining electrode X 1 , the second sustaining electrode X 2 , the first scanning electrode Y 1  and the second scanning electrode Y 2  can be reduce, and so as the electromagnetic interference (EMI) do. 
     In FIG. 10, it shows the block diagram of the driving circuit used in the PDP having a YXYX-type electrode arrangement according to the preferred embodiment in the present invention. The sustaining electrodes X are divided into two groups, including a first sustaining electrodes X 1  and a second sustaining electrodes X 2 . Those electrodes are alternately disposed. For example, the first sustaining electrodes X 1  include the first sustaining electrode X 1 ( 1 ), X 1 ( 2 ), X 1 ( 3 ), X 1 ( 4 ), and the second sustaining electrodes X 2  include the second sustaining electrode X 2 ( 1 ), X 2 ( 2 ), X 2 ( 3 ) and X 2 ( 4 ). All first sustaining electrodes X 1  are coupled to the first sustaining circuit  1002 , and all second sustaining electrodes X 2  are coupled to the second X sustaining circuit  1004 . These X sustaining circuits  1002  and  1004  are used to provide the driving waveforms. Furthermore, a phase shift controller  1006  is coupled to the first X sustaining circuit  1002  and the second X sustaining circuit  1004  to provide the first discharge sustaining pulse  902  to the first X sustaining circuit  1002  and provide the second discharge sustaining pulse  904  to the second X sustaining circuit  1004 . The first and second discharge sustaining pulses  902 ,  904  are in different phases. Only one reset circuit  1005  is coupled to the first X sustaining circuit  1002  and the second X sustaining circuit  1004 . The reset circuit  1005  is a positive polarity reset circuit. 
     The first scanning electrode Y 1  and the second scanning electrode Y 2  are both coupled to the scanning IC  1008 , and the scanning IC  1008  is further connected with the multiplexer  1010  of the Y driving circuit  1012 . The Y driving circuit  1012  includes a reset/scan circuit  1014  and a Y sustaining circuit  1016 . The reset/scan circuit  1014  is a negative/positive polarity reset circuit. During the reset period P 1  and the address period P 2 , the reset/scan circuit  1014  provides a voltage, for instance 180V, −90V or −180V, to the first scanning electrode Y 1  and the second scanning electrode Y 2 . During the sustain period P 3 , the Y sustaining circuit  1016  provides a voltage of 180V or 0V to the first scanning electrode Y 1  and the second scanning electrode Y 2 . 
     By a control signal (not shown in FIG.  10 ), the Y sustain scanning driving circuit  1012  provides different driving signals to the first scanning electrode Y 1  and the second scanning electrode Y 2  during the address period P 2  and the sustain period P 3 . These driving signals are transmitted to the scanning IC  1008  via the multiplexer  1010 . 
     During the address period P 2 , scanning pulses are outputted to the first scanning electrodes Y 1 ( 1 )˜Y( 4 ) and the second scanning electrodes Y 2 ( 1 )˜Y 2 ( 4 ) in order by the scanning IC  1008 . During the sustain period P 3 , several sustain discharging pulses  910  are applied to the first scanning electrode Y 1 ( 1 )˜Y 1 ( 4 ) and the second scanning electrode Y 2 ( 1 )˜Y 2 ( 4 ) by the scanning IC  1008  simultaneously. 
     Please refer to FIG. 11, it shows the block diagram of another driving circuit used in the PDP having a YXXY-type electrode arrangement in the present invention. The sustaining electrodes X are divided into two groups, including a first sustaining electrodes X 1  and the second sustaining electrodes X 2 . The scanning electrodes Y are divided into two groups, including first scanning electrodes Y 1  and second scanning electrodes Y 2 . For example, the first sustaining electrodes X 1  include the first sustaining electrode X 1 ( 1 ), X 1 ( 2 ), X 1 ( 3 ), X 1 ( 4 ), the second sustaining electrodes X 2  include the second sustaining electrode X 2 (l), X 2 ( 2 ), X 2 ( 3 ) and X 2 ( 4 ), the first scanning electrodes Y 1  include the first scanning electrode Y 1 ( 1 ), Y 1 ( 2 ), Y 1 ( 3 ), Y 1 ( 4 ), and the second scanning electrodes Y 2  include the second scanning electrode Y 2 ( 1 ), Y 2 ( 2 ), Y 2 ( 3 ) and Y 2 ( 4 ). These electrodes are arranged by the order of Y( 1 ), X 1 ( 1 ), X 1 ( 2 ), Y 1 ( 2 ), Y 2 (l), X 2 ( 1 ), X 2 ( 2 ), Y 2 ( 2 ), Y 3 (l), . . . etc. Meanwhile, all first sustaining electrodes X 1  are coupled to a first X sustaining circuit  1102 , and all second sustaining electrodes X 2  are coupled to a second X sustaining circuit  1104 . The phase shift controller  1106  is coupled to the first X sustaining circuit  1102  and the second X sustaining circuit  1104 . Only one reset circuit  1105  is coupled to the first X sustaining circuit  1002  and the second X sustaining circuit  1004 . 
     Please refer to FIGS. 12A and 12B. FIG. 12A shows a part of the conventional X sustaining circuit  824  in FIG. 8, and FIG. 12B shows a part of the first X sustaining circuit  1002  of FIG. 10 in the present invention. In FIG. 12A, the conventional X sustaining circuit  824  must use at least  4  transistors Q 1 , Q 2 , Q 3 , and Q 4 , which are controlled by control signals S 1 , S 2 , S 3 , and S 4  to provide the currents to all the sustaining electrodes X. In the present invention, the sustaining electrodes X are divided into two groups, only two transistors Q 1 ′ and Q 2 ′, controlled by the control signals S 1 ′, S 2 ′, are used to drive the first sustaining electrode X 1  because the number of the first sustaining electrode X 1  is reduced. The total transistors of the first X sustaining circuit  1002  and the second X sustaining circuit  1004  are the same as that in the conventional X sustaining circuit  824  although two sustaining circuits are used in the present invention. Therefore, the number of the transistors for driving the sustaining electrode X will not be increased. 
     Please refer to FIG. 13, it shows the enlargement of the waveforms in FIG.  9 . The scanning signals IN_Y 1  and IN_Y 2 , the sustaining signals IN_X 1  and IN_X 2 , the current signals IX 1 , IX 2 , IY 1 , IY 2  are further explained below. 
     The sustain period P 3  is further divided into several periods. During a period T 1 , a sustaining voltage is provided to the first sustaining electrode X 1 , for example, the voltage of the first sustaining electrode X 1  is raised from 0V to a high voltage of 180V. At the same time, the second sustaining electrode X 2 , the first scanning electrode Y 1 , and the second scanning electrode Y 2  are maintained at constant voltages. The second sustaining electrode X 2  is maintained at a first voltage, such as a low voltage of 0V. The first scanning electrode Y 1  and the second scanning electrode Y 2  are maintained at a scanning voltage, such as a high voltage of 180V. 
     During a period T 2 , the voltages of the first scanning electrode Y 1  and the second scanning electrode Y 2  are reduced from the scanning voltage to a second voltage. The second voltage is a low voltage, for example, the voltages of these electrodes are reduced from 180V to 0V. The first sustaining electrode X 1  and the second electrode X 2  are maintained at the sustaining voltage and the first voltage, respectively. After this period T 2 , the plasma between the first scanning electrode Y 1  and the first sustaining electrode X 1  is triggered and a first discharge current  926  is produced because the voltage difference between the first scanning electrode Y 1  and the first sustaining electrode X 1  is larger than a threshold voltage. 
     During a period T 3 , a sustaining voltage is provided to the second sustaining electrode X 2 . The voltage of the second sustaining electrode X 2  is increased from 0V to 180V. At the same time, the first scanning electrode Y 1  and the second scanning electrode Y 2  are remained at the second voltage (0V). The first sustaining electrode X 1  still maintains at the sustaining voltage (180V). After the period T 3 , the plasma between the second scanning electrode Y 2  and the second sustaining electrode X 2  is triggered and the second discharge current  936  is produced. The second discharge current  936  is produced after the first discharge current  926  is produced for a delay time D 1 . The first and second discharge currents are not occurred at the same time, so the instant power consumption of the PDP may be reduced. 
     Generally, the first discharge current  926  appears after a delay of 0.5˜1ì s from the end of the period T 2  and the second discharge current  936  appears after a delay of 0.5˜1ì s from the end of the period T 3  in FIG.  13 . 
     Then, during a period T 4 , the voltage of the first sustaining electrode X 1  is reduced from the sustaining voltage to a third voltage. The third voltage is a low voltage, such as 0V. At the same time, the first scanning electrode Y 1  and the second scanning electrode Y 2  are maintained at the second voltage (0V), and the second sustaining electrode X 2  is maintained at the sustaining voltage (180V) during the period T 4 . Similarly, during a period T 5 , the voltages of the first scanning electrode Y 1  and the second scanning electrode Y 2  are increased to the scanning voltage, such as 180V. The first sustaining electrode X 1  and the second sustaining electrode X 2  are maintained at the third voltage and the sustaining voltage during the period T 5 , respectively. During a period T 6 , the voltage of the second sustaining electrode X 2  is reduced to a fourth voltage. The fourth voltage is a low voltage, the voltage of the second sustaining electrode X 2  is reduced from the high voltage of 180V to the low voltage of 0V. The first sustaining electrode X 1  is maintained at the third voltage (0V), the first scanning electrode Y 1  and the second scanning electrode Y 2  are remained at the scanning voltage (180V) during the period T 6 . Therefore, a third discharge current  928  having an opposite phase to the first discharge current  926  is produced on the first sustaining electrode X 1 . A fourth discharge current  938  with an opposite phase to the second discharge current  936  is also produced on the second sustaining electrode X 2 . A delay time D 2  is happened during the third discharge current  928  and fourth discharge current  938 . 
     Please refer to FIG. 14, it shows another sustain discharge waveform according to the second embodiment in the present invention. During the period T 1 ′, T 2 ′ and T 3 ′, the variation of the voltages of the first sustaining electrode X 1 , the second sustaining electrode X 2 , the first scanning electrode Y 1  and the second scanning electrode Y 2  are the same as that during the first, second, third periods T 1 , T 2 , and T 3  in FIG.  13 . In the periods T 4 ′, T 5 ′, and T 6 ′, the voltage variations of these electrodes are different. During the period T 4 ′, the first sustaining electrode is maintained at the sustaining voltage (180V), but the voltage of the second sustaining electrode X 2  is reduced to a low voltage such as 0V. At the same time, the first scanning electrode Y 1  and the second scanning electrode Y 2  are maintained at the low voltage of 0V. 
     Next, during a period T 5 ′, the first scanning electrode Y 1  and the second scanning electrode Y 2  are increased to the scanning voltage (180V). At the same period, the voltages of the first sustaining electrode X 1  and the second sustaining electrode X 2  are maintained at the sustaining voltage (180V) and the low voltage (0V), respectively. Similarly, during a period T 6 ′, the first sustaining electrode X 1  is decreased to the low voltage such as 0V. The voltages applied to the second sustaining electrode X 2 , the first scanning electrode Y 1  and the second scanning electrode Y 2  maintain at constant values (0V, 180V, 180V) during the period T 6 ′. Therefore, the third discharge current  928 , having an opposite phase to the first discharge current  926 , is produced on the second sustaining electrode X 2 . And the fourth discharge current  938  with the opposite phase to the second discharge current  936  is produced on the first sustaining electrode X 1 . 
     All scanning electrodes Y are connected to one scanning IC  1008  or  1108  as shown in FIG. 10 or FIG.  11 . However, it will not limit the scope of the present invention. In FIG. 15, it shows block diagram of another driving circuit for the PDP. These scanning electrodes are divided into two groups, including a first scanning electrode Y 1  and a second scanning electrode Y 2 , and coupled to different scanning ICs. The first scanning electrode Y 1  is coupled to the scanning IC  1508 , and the second scanning electrode Y 2  is coupled to the scanning IC  1518 . The sustain Y driving circuit  1512  includes a reset/scan circuit  1514 , a sustaining circuit  1516 , and a multiplexer  1510 . The Y driving circuit  1522  includes a reset/scan circuit  1524 , a sustaining circuit  1526 , and a multiplexer  1520 . The scanning IC  1508  and  1518  are coupled to the multiplexer  1510 ,  1520 , respectively. The first sustaining electrode X 1  is coupled to the X sustaining circuit  1502  and the second sustaining electrode X 2  is coupled to the X sustaining circuit  1504 . The phase shift controller  1506  is coupled to the X sustaining circuit  1502 , X sustaining circuit  1504 , the sustain Y driving circuit  1512  and Y driving circuit  1522 . The scanning IC  1508  and the scanning IC  1518  output the third discharge sustaining pulse and the fourth discharge sustaining pulse. The phases of the third sustain discharge and the fourth sustain discharge can be the same or different. 
     Based on the scope of the present invention, the sustaining electrode X can be divided into N set, and N&gt;2. As long as the phases of the discharge sustaining pulses applied to the N set electrodes are different, the purpose of the present invention is achieved. 
     From the above description, the driving method and circuit of the sustaining electrode in the present invention can reduce the voltage notch effectively, increase the operation margin, and reduce the electromagnetic interference of the PDP. And the purpose in the present invention is achieved with a simple circuit. 
     Once given the above disclosure, many other features, modifications, and improvements will become apparent to the skilled artisan. Such other features, modifications, and improvements are, therefore, considered to be a part of this invention, the scope of which is to be determined by the following claims.