Abstract:
A sustain driving apparatus and method for a plasma display panel that is adaptive for reducing power consumption as well as stabilizing a driving waveform. In the apparatus, a voltage source has a half of the voltage required for a sustain driving of the plasma display panel. An energy recovering circuit is connected between the voltage source and the panel. The energy recovering circuit configures an LC resonance circuit by a switching to recover a power of the panel, thereby applying said sustain driving voltage to the panel.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    This invention relates to a technique of driving a plasma display panel, and more particularly to a sustain driving apparatus and method for a plasma display panel that is adaptive for reducing power consumption as well as stabilizing a driving waveform.  
           [0003]    2. Description of the Related Art  
           [0004]    Generally, a plasma display panel (PDP) is a picture display device using a gas discharge, and is advantageous to a large screen. The PDP has provided an enhanced picture quality owing to the recent improvement of circuit technique and panel structure.  
           [0005]    Recently, there has been developed various flat panel devices that are capable of reducing a heavy weight and a large bulk, which are drawbacks of the cathode ray tube (CRT). Such flat panel display devices include a liquid crystal display (LCD), a field emission display (FED), a plasma display panel (PDP) and an electro-luminescence display (ELD), etc.  
           [0006]    The PDP of these flat panel display devices allow an ultraviolet ray generated upon discharge of an inactive mixture gas, such as He+Xe, Ne+Xe or He+Xe+Ne, etc., to radiate a phosphorous material to thereby display a picture. The PDP has been used for a high-resolution television, a monitor and an internal or external advertising display because it has a rapid response speed and is suitable for displaying a large-area picture.  
           [0007]    The PDP is largely classified into an alternating current (AC) type in which electrodes are covered with a dielectric material and a discharge is caused with the aid of wall charges accumulated onto the dielectric material, and a direct current (DC) type in which a discharge is caused between electrodes opposed in the longitudinal direction. The AC-type PDP employs a surface discharge occurring at the surface of the dielectric material with which the electrodes are coated. A sustaining pulse for sustaining a cell discharge of the AC-type PDP has a high voltage of hundreds of volts (V) and a frequency of hundreds of KHz.  
           [0008]    When the sustaining pulse is applied to the PDP for the purpose of causing a charge/discharge, a capacitive load of the panel does not cause an energy waste, but a lot of energy loss occurs at the PDP because a direct current (DC) power source is used to generate a sustaining pulse. Particularly, if an excessive current flows in the cell upon discharge, then an energy loss is increased. In order to recover an energy generated unnecessarily within the panel, that is, a reactive power, a driving circuit of the PDP includes an energy recovering circuit.  
           [0009]    Referring to FIG. 1, a conventional energy recovering circuit of the PDP includes first and third switches S 11  and S 13  connected, in parallel, between an inductor L and an external capacitor Cs, a second switch S 12  for applying a sustain voltage Vs to a panel capacitor Cp, and a fourth switch S 14  for applying a ground voltage GND to the panel capacitor Cp.  
           [0010]    First and second diodes D 11  and D 12  for limiting a reverse current are connected between the first and third switches S 11  and S 13 . The panel capacitor Cp is an equivalent expression of a capacitance value of the panel.  
           [0011]    [0011]FIG. 2 is a timing diagram and a waveform diagram representing an ON/OFF timing of switches shown in FIG. 1 and an output waveform of the panel capacitor shown in FIG. 1.  
           [0012]    An operation of the energy recovering circuit shown in FIG. 1 will be described in conjunction with FIG. 2.  
           [0013]    First, prior to a time t 1 , it is assumed that a voltage charged in the panel capacitor Cp should be 0 volt and a voltage equal to Vs/2 should be charged in the external capacitor Cs.  
           [0014]    At a time t 1 , the first switch S 11  is turned on and keeps the ON state. Then, a voltage stored in the external capacitor Cs is applied, via the first switch S 11  and the first diode D 11 , to the inductor L. At this time, the inductor L constructs a serial LC resonance circuit along with the panel capacitor Cp. Accordingly, the panel capacitor Cp begins to be charged into a resonant waveform by a resonant waveform applied, via the inductor L, to the panel capacitor Cp, and is charged until a sustaining potential Vs.  
           [0015]    At a time t 2 , the first switch Sw 1  is turned off and is kept in the OFF state while the second switch S 12  is turned on and is kept in the OFF state. Then, a sustaining voltage Vs from the sustaining voltage source Vs is applied, via the second switch S 12 , to the panel capacitor Cp. Accordingly, a voltage of the panel capacitor Cp remains at a sustaining level Vs at the t 2  time.  
           [0016]    At a time t 3 , the second switch S 12  is turned off and is kept in the OFF state while the third switch S 13  is turned on and is kept in the ON state. Then, a voltage of the panel capacitor Cp is recovered into the external capacitor Cs by way of the inductor L, the second diode D 12  and the third switch S 13 .  
           [0017]    At a time t 4 , the third switch S 13  is turned off and is kept in the OFF state while the fourth switch Sw 4  is turned on and is kept in the ON state. Accordingly, a ground voltage GND is applied to the panel capacitor Cp to maintain the panel capacitor Cp at the ground voltage GND.  
           [0018]    The conventional energy recovering circuit shown in FIG. 1 has a disadvantage in that it requires a high voltage source Vs of hundreds of volts so as to maintain the panel at the sustain level, thereby increasing power consumption of the driving circuit. Furthermore, the energy recovering circuit of FIG. 1 has a disadvantage in that it has a high cost because switching devices having a high voltage-resisting property are used as the switches S 11  to S 14  implemented by a semiconductor device such as a field effect transistor (FET) such as it can provide a stable operation at a high voltage.  
           [0019]    In order to overcome the above problems of the energy recovering circuit of the PDP, there has been suggested a low-voltage driving energy recovering apparatus in which a voltage equal to ½ of the sustaining voltage is used for a driving voltage source.  
           [0020]    Referring to FIG. 3, the low-voltage driving energy recovering apparatus includes a first switch S 21  connected to an ½ sustaining voltage source Vs/2, an external capacitor Cs between the first switch S 21  and a ground voltage source GND, a second switch S 22  connected between a first node N 1  provided between the first switch S 21  and the external capacitor Cs and the inductor L, and a third switch S 23  connected between a second node N 2  provided between the inductor L and a panel capacitor Cp and the ground voltage source GND.  
           [0021]    Herein, the panel capacitor Cp is an equivalent expression of a capacitance value of the PDP.  
           [0022]    An operation of the low-voltage driving energy recovering apparatus will be described in conjunction with FIG. 4 below. In FIG. 4, a waveform Vn 2  represents a voltage of the second node N 2  that is an output node.  
           [0023]    At a time T 1 , the first and third switches S 21  and S 23  keep an ON state while the second switch S 22  keeps an OFF state. Accordingly, at a time T 21 , the external capacitor Cs charges a voltage into Vs/2, and the panel capacitor Cp maintains a ground voltage GND.  
           [0024]    At a time T 2 , the first and third switches S 21  and S 23  are turned off while the second switch S 22  is turned on. Accordingly, at a time T 2 , the panel capacitor Cp constructs a serial resonance circuit along with the inductor L to charge a voltage passing through the inductor L until the sustain level Vs.  
           [0025]    Such a low-voltage driving energy recovering apparatus has an advantage in that it can reduce a driving voltage to ½ in comparison with the energy recovering circuit shown in FIG. 1 and reduce switching devices to three. However, the low-voltage driving energy recovering apparatus has problems in that it fails to constantly keep a potential of the discharge voltage capable of causing a stable discharge because a driving voltage is generated only by the resonant waveform and it fails to provide a stable driving waveform because a frequency of the resonant waveform is changed depending upon a load variation in the panel capacitor Cp.  
         SUMMARY OF THE INVENTION  
         [0026]    Accordingly, it is an object of the present invention to provide a sustain driving apparatus and method for a plasma display panel that is adaptive for reducing power consumption as well as stabilizing a driving waveform.  
           [0027]    A further object of the present invention is to provide a sustain driving apparatus and method for a plasma display panel wherein positive and negative sustaining voltages are supplied to any one of sustain electrode pairs to unify a printed circuit board.  
           [0028]    In order to achieve these and other objects of the invention, a sustain driving apparatus for a plasma display panel according to one aspect of the present invention includes a voltage source having a half of the voltage required for a sustain driving of the plasma display panel; and an energy recovering circuit connected between the voltage source and the panel, said circuit configuring an LC resonance circuit by a switching to recover a power of the panel, thereby applying said sustain driving voltage to the panel.  
           [0029]    In the sustain driving apparatus, the energy recovering circuit includes an inductor connected, in serial, to the panel to configure a serial resonance circuit; a charge path formed between the voltage source and the panel including the inductor; a discharge path formed between the voltage source and the panel including the inductor; and a charge capacitor connected to the voltage source to thereby charge the panel into a voltage higher than said voltage of the voltage source using the charged voltage.  
           [0030]    Said charge path includes a first switch connected between the voltage source and a first node positioned between the charge capacitor and the inductor; and a second switch connected between the voltage source and a second node positioned between the inductor and the panel.  
           [0031]    Said discharge path includes a third switch connected between the voltage source and the first node; and a fourth switch connected between the second node and the ground voltage source.  
           [0032]    The sustain driving apparatus further includes a first diode connected between the first node and the inductor; a second diode connected between the third switch and the inductor; and a third diode connected between the voltage source and the charge capacitor.  
           [0033]    The sustain driving apparatus further includes a fourth diode connected between the voltage source and a third node positioned between the first and third switches.  
           [0034]    The energy recovering circuit includes a discharge path formed between the voltage source and the panel and including a first inductor; a charge path formed between the voltage source and the panel in such a manner to be separated from the discharge path and including a second inductor; and a charge capacitor connected to the voltage source to thereby charge the panel into a voltage higher than said voltage of the voltage source using the charged voltage.  
           [0035]    Herein, said charge path includes a first switch connected between the voltage source and a first node positioned between the charge capacitor and the second inductor; and a second switch connected to the charge capacitor and connected between the voltage source and a second node positioned between the second inductor and the panel.  
           [0036]    Said discharge path includes a third switch connected between the voltage source and the first inductor; and a fourth switch connected between a third node positioned between the first inductor and the panel and a ground voltage source.  
           [0037]    The sustain driving apparatus further includes a first diode connected between the voltage source and a fourth node positioned between the first and third switches.  
           [0038]    A sustain driving apparatus for a plasma display panel according to another aspect of the present invention, said apparatus alternately applying a sustain pulse having a sustain voltage value to a scan electrode and a sustain electrode, includes a voltage source having a half of the voltage required for a sustain driving of the plasma display panel; a boosting circuit connected to the voltage source, said circuit boosting a ½ sustain voltage from the voltage source to generate said sustain voltage; and a sustain capacitor connected to the boosting circuit and charged with said sustain voltage from the boosting circuit to supply a constant sustain voltage to the panel.  
           [0039]    In the sustain driving apparatus, the boosting circuit includes a first diode connected between the voltage source and the sustain capacitor; and a first switch and a charge capacitor connected between the voltage source and the sustain capacitor and connected, in parallel, to the first diode.  
           [0040]    Herein, said charge capacitor is charged with an ½ sustain voltage by a current path formed between the voltage source and the ground voltage level and thereafter is charged with a sustain voltage made by an addition of an ½ sustain voltage coupled to the negative terminal thereof by turning-on of the first switch and the previously charged ½ sustain voltage.  
           [0041]    Said sustain capacitor supplies said sustain voltage such that, when the sustain voltage having been charged in the charge capacitor is applied to the panel, the panel can provide a stable maintenance of said sustain voltage.  
           [0042]    The sustain driving apparatus further includes an inductor connected between the boosting circuit and the panel to configure a serial resonance circuit.  
           [0043]    The sustain driving apparatus further includes a second diode connected between the boosting circuit and the sustain capacitor to prevent a flow of reverse current.  
           [0044]    The sustain driving apparatus further includes a second switch connected between the boosting circuit and the panel to supply the panel to the sustain voltage; and a third switch connected between the boosting circuit and the ground voltage level to charge said ½ sustain voltage into the charge capacitor.  
           [0045]    The sustain driving apparatus further includes a third diode connected between the boosting circuit and the third switch to prevent a flow of reverse current.  
           [0046]    The sustain driving apparatus further includes a first inductor connected between the panel and the voltage source to discharge the panel; and a second inductor connected between the boosting circuit and the panel to charge the panel.  
           [0047]    Herein, a inductance value of the first inductor is smaller than that of the second inductor.  
           [0048]    A sustain driving apparatus for a plasma display panel according to still another aspect of the present invention includes a voltage source having a half of the voltage required for a sustain driving of the plasma display panel; an energy recovering circuit connected between the voltage source and the panel, said circuit configuring an LC resonance circuit by a switching to recover a power of the panel, thereby applying said sustain driving voltage to the panel; a charge capacitor connected to the voltage source to charge the panel into a voltage higher than said voltage of the voltage source using the charged voltage; and a separating diode for shutting off a reverse current into the voltage source and for applying said voltage having the ½ value to the energy recovering circuit and the charge capacitor separately.  
           [0049]    In the sustain driving apparatus, the energy recovering circuit includes an inductor connected, in serial, to the panel to configure a serial resonance circuit; a charge path formed between the voltage source and the panel and including the inductor; and a discharge path formed between the voltage source and the panel and including the inductor.  
           [0050]    Herein, said charge path includes a first switch connected between the voltage source and the inductor; and a second switch connected, in parallel, to the first switch and the inductor between the voltage source and the panel.  
           [0051]    Said discharge path includes a third switch connected, in parallel, to the first switch between the voltage source and the inductor; and a fourth switch connected between the panel and a ground voltage source.  
           [0052]    The sustain driving apparatus further includes a first diode connected between the first switch and the inductor; and a second diode connected between the third switch and the inductor.  
           [0053]    Herein, said charge capacitor is connected between a first node positioned between the first switch and the first diode and a second node positioned between the voltage source and the second switch.  
           [0054]    The separating diode includes a first separating diode connected between the energy recovering circuit and the voltage source; and a second separating diode connected, in parallel, to the energy recovering circuit including the third diode between the voltage source and the second node positioned between the charge capacitor and the second switch.  
           [0055]    The energy recovering circuit includes a discharge path formed between the voltage source and the panel and including a first inductor; and a charge path formed between the voltage source and the panel in such a manner to be separated from the discharge path and including a second inductor.  
           [0056]    Herein, said charge path includes a first switch connected between the voltage source and the second inductor; and a second switch connected to the charge capacitor and connected, in parallel, to the first switch and the second inductor between the voltage source and the panel.  
           [0057]    Said discharge path includes a third switch connected between the voltage source and the first inductor; and a fourth switch connected between the first node positioned between the first inductor and the panel and a ground voltage source.  
           [0058]    The sustain driving apparatus further includes a first diode connected between the first switch and the second inductor; and a second diode connected between the third switch and the first inductor.  
           [0059]    Herein, said charge capacitor is connected between a second node positioned between the first switch and the first diode and a third node positioned between the voltage source and the second switch.  
           [0060]    The separating diode includes a first separating diode connected between the voltage source and a fourth node positioned between the first and third switches; and a second separating diode connected between the voltage source and the third node.  
           [0061]    A sustain driving apparatus for a plasma display panel according to still another aspect of the present invention includes a display panel having pixel cells provided at intersections between first and second sustain electrodes for causing a sustain discharge and address electrodes, said pixel cells being arranged in a matrix type; a positive voltage source; a negative voltage source; a first recovering circuit connected between a positive voltage source and the display panel to charge a positive voltage from the positive voltage source into the display panel and recover the charged positive voltage; and a second recovering circuit connected between the negative voltage source and the first recovering circuit to charge a negative voltage from the negative voltage source into the display panel and recover the charged negative voltage.  
           [0062]    Herein, any one of the first and second sustain electrodes of the display panel is connected to a ground voltage source, and the remaining one thereof is connected to the first recovering circuit.  
           [0063]    Said positive voltage source supplies the first recovering circuit with a positive voltage equal to a half of a sustain pulse for said sustain discharge, and said negative voltage source supplies the second recovering circuit with a negative voltage equal to a half of a sustain pulse for said sustain discharge.  
           [0064]    The sustain driving apparatus further includes a switching device connected between the ground voltage source and the display panel to switch a ground voltage from the ground voltage source into the display panel.  
           [0065]    The first recovering circuit includes a first energy-recovering capacitor connected, in parallel, to the positive voltage source to charge a positive energy upon charging/discharging of the display panel; a first switching circuit connected between the first energy-recovering capacitor and the display panel to form a charge/recovery path for said positive voltage; a first charging capacitor connected between the display panel and the first switching circuit to sustain said positive sustain pulse charged in the display panel using a positive voltage from the first energy-recovering capacitor; and an inductor connected between the first charging capacitor and the display panel.  
           [0066]    Herein, the first switching circuit includes a first switch connected between the positive voltage source and the inductor; a second switch connected between the first switch and the inductor to switch a signal path of the first charging capacitor and the inductor; and a third switch connected between the second switch and the display panel to switch a voltage charged in the first charging capacitor into the display panel.  
           [0067]    The first switching circuit further includes a first diode connected between the second switch and the first charging capacitor; and a second diode connected between the second switch and the inductor.  
           [0068]    The second recovering circuit includes a second energy-recovering capacitor connected, in parallel, to the negative voltage source to charge a negative energy upon charging/discharging of the display panel; a second switching circuit connected between the second energy-recovering capacitor and the display panel to form a charge/recovery path for said negative voltage; a second charging capacitor connected between the display panel and the second switching circuit to sustain said negative sustain pulse charged in the display panel using a negative voltage from the second energy-recovering capacitor; and an inductor connected between the second charging capacitor and the display panel.  
           [0069]    The second switching circuit includes a fourth switch connected between the negative voltage source and the inductor; a fifth switch connected between the fourth switch and the inductor to switch a signal path of the second charging capacitor and the inductor; and a sixth switch connected between the fifth switch and the display panel to switch a voltage charged in the second charging capacitor into the display panel.  
           [0070]    The second switching circuit further includes a third diode connected between the fifth switch and the second charging capacitor; and a fourth diode connected between the fifth switch and the inductor.  
           [0071]    A method of driving a plasma display panel according to still another aspect of the present invention, said panel having an ½ sustain voltage source, includes the steps of boosting a ½ sustain voltage value of the voltage source to generate a sustain voltage; supplying the panel with said boosted sustain voltage; charging the boosted sustain voltage into a sustain capacitor; and supplying said sustain voltage from the sustain capacitor such that, when the boosted sustain voltage is supplied to the panel, said sustain voltage is constantly maintained to permit a stable driving.  
           [0072]    A method of driving a plasma display panel according to still another aspect of the present invention includes the steps of generating a positive voltage supplied to the plasma display panel; generating a negative voltage supplied to the panel; charging said positive voltage into the panel and recovering the charged positive voltage; and charging said negative voltage into the panel and recovering the charged negative voltage. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0073]    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:  
         [0074]    [0074]FIG. 1 is a circuit diagram of a conventional energy recovering apparatus of a plasma display panel;  
         [0075]    [0075]FIG. 2 is a timing diagram and a waveform diagram representing a waveform according to an ON/OFF timing of each switch shown in FIG. 1;  
         [0076]    [0076]FIG. 3 is a circuit diagram of a conventional low-voltage driving energy recovering apparatus of a plasma display panel;  
         [0077]    [0077]FIG. 4 is a timing diagram and a waveform diagram representing a waveform according to an ON/OFF timing of each switch shown in FIG. 3;  
         [0078]    [0078]FIG. 5 is a circuit diagram of a sustain driving apparatus of a plasma display panel according to a first embodiment of the present invention;  
         [0079]    [0079]FIG. 6 is a timing diagram and a waveform diagram representing a waveform according to an ON/OFF timing of each switch shown in FIG. 5;  
         [0080]    [0080]FIG. 7 is a waveform diagram representing an output waveform of the sustain driving apparatus of the plasma display panel according to the present invention and a voltage loaded on the third node N 33 ;  
         [0081]    [0081]FIG. 8 is a circuit diagram of a sustain driving apparatus of a plasma display panel according to a second embodiment of the present invention;  
         [0082]    [0082]FIG. 9 is a circuit diagram of a sustain driving apparatus of a plasma display panel according to a third embodiment of the present invention;  
         [0083]    [0083]FIG. 10 is a timing diagram and a waveform diagram representing a waveform according to an ON/OFF timing of each switch shown in FIG. 9;  
         [0084]    [0084]FIG. 11 is a circuit diagram of a sustain driving apparatus of a plasma display panel according to a fourth embodiment of the present invention;  
         [0085]    [0085]FIG. 12 is a timing diagram and a waveform diagram representing a waveform according to an ON/OFF timing of each switch shown in FIG. 11;  
         [0086]    [0086]FIG. 13 is a graph representing a driving waveform of a sustain driving apparatus of a plasma display panel according to an experiment for the apparatus of FIG. 11;  
         [0087]    [0087]FIG. 14 is a circuit diagram of a sustain driving apparatus of a plasma display panel according to a fifth embodiment of the present invention;  
         [0088]    [0088]FIG. 15 is a timing diagram and a waveform diagram representing a waveform according to an ON/OFF timing of each switch shown in FIG. 14;  
         [0089]    [0089]FIG. 16 is a circuit diagram of a sustain driving apparatus of a plasma display panel according to a sixth embodiment of the present invention;  
         [0090]    [0090]FIG. 17 is a timing diagram and a waveform diagram representing a waveform according to an ON/OFF timing of each switch shown in FIG. 16;  
         [0091]    [0091]FIG. 18 is a circuit diagram of a sustain driving apparatus of a plasma display panel according to a seventh embodiment of the present invention;  
         [0092]    [0092]FIG. 19 is a timing diagram and a waveform diagram representing a waveform according to an ON/OFF timing of each switch shown in FIG. 18;  
         [0093]    [0093]FIG. 20 is a circuit diagram of a sustain driving apparatus of a plasma display panel according to an eighth embodiment of the present invention;  
         [0094]    [0094]FIG. 21 is a timing diagram and a waveform diagram representing a waveform according to an ON/OFF timing of each switch shown in FIG. 20;  
         [0095]    [0095]FIG. 22 is a circuit diagram of a sustain driving apparatus of a plasma display panel according to a ninth embodiment of the present invention;  
         [0096]    [0096]FIG. 23 is a timing diagram and a waveform diagram representing a waveform according to an ON/OFF timing of each switch shown in FIG. 22; and  
         [0097]    [0097]FIG. 24 is a waveform diagram of a voltage waveform applied to the panel capacitor by the sustain driving apparatus of the plasma display panel shown in FIG. 22. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0098]    Referring to FIG. 5, there is shown a sustain driving apparatus of a plasma display panel according to the first embodiment of the present invention.  
         [0099]    The sustain driving apparatus includes an ½ sustain voltage source Vs/2, first and second switches S 31  and S 33  connected to the ½ sustain voltage source Vs/2, second and fourth switches S 32  and S 34  connected, in parallel, to a first electrode of the panel capacitor Cp; and an inductor L connected between a first node N 31  positioned between the first and third switches S 31  and S 33  and a second node N 32  positioned between the second and fourth switches S 32  and S 34 , a first diode D 31  connected between a first terminal of the first switch S 31  and the first node N 31 , a second diode D 32  connected between the first node N 31  and the first terminal of the third switch S 33 , a third diode D 33  connected between the first switch S 31  and the second switch S 32 , and a charge capacitor Cc connected between a third node N 33  positioned between the first switch S 31  and the first diode D 31  and a fourth node N 34  positioned between the third diode D 33  and the second switch S 32 .  
         [0100]    The ½ sustain voltage source Vs/2 is connected, via a fifth node N 35 , to the second terminal of the first switch S 31  and the second terminal of the second switch S 32 . The panel capacitor Cp is an equivalent expression of a capacitance value of the PDP.  
         [0101]    The first to fourth switches S 31  to S 34  are implemented by semiconductor switching devices such as MOS FET, IGBT and BJT, etc.  
         [0102]    The first to third diodes D 31 , D 32  and D 33  play a role to form a current path only in a constant direction. In other words, the first diode D 31  shuts off a reverse current flowing from the panel capacitor Cp into the first switch S 31  while the second diode D 32  shuts off a reverse current flowing from the ½ sustain voltage source Vs/2 into the inductor L. Further, the third diode D 33  shuts off a reverse current flowing from the fourth node N 34  into the ½ sustain voltage source Vs/2. The third diode D 33  forces a Vs voltage charged by the charge capacitor Cc not to make an affect to the ½ sustain voltage source Vs/2.  
         [0103]    The charge capacitor Cc charges a voltage from the ½ sustain voltage source Vs/2. The voltage Vs/2 charged in the charge capacitor Cs is added to a voltage supplied from the ½ sustain voltage source Vs/2 to apply the added voltage to the panel capacitor Cp.  
         [0104]    An operation of the sustain driving apparatus of the PDP according to the first embodiment of the present invention will be described in conjunction with FIG. 6 and FIG. 7 below.  
         [0105]    Herein, a waveform VN 32  in FIG. 6 represents a voltage of the second node N 32  that is an output node. FIG. 7 represents an output waveform of the sustain driving apparatus of the PDP according to the first embodiment of the present invention and a voltage loaded on the third node N 33 .  
         [0106]    First, in a T 4  interval, the fourth switch S 34  keeps an ON state while the first to third switches S 31  to S 33  keep an OFF state. Accordingly, the first terminal of the charge capacitor Cc is connected, via the fourth node N 34  and the third diode D 33 , to the ½ sustain voltage source Vs/2 while the second terminal thereof is connected, via the third node N 33 , the first diode D 31 , the first node N 31 , the inductor L, the second node N 32  and the fourth switch S 34 , to the ground voltage source GND. As a result, the ½ sustain voltage Vs/2 from the ½ sustain voltage source Vs/2 is charged into the charge capacitor Cc. Further, in the T 4  interval, the panel capacitor Cp charges a ground voltage GND from the ground voltage source GND through the fourth switch S 34 .  
         [0107]    Then, in a T 1  interval, the fourth switch S 34  is turned off; the first switch S 31  is turned on; and the second and third switches S 32  and S 33  are maintained at an OFF state. As the first switch S 31  is turned on, a supply voltage from the ½ sustain voltage source Vs/2 charges the panel capacitor Cp via the first switch S 31 , the first diode D 31  and the inductor L. During the T 1  interval, the panel capacitor Cp configures an LC serial resonance circuit along with the inductor L to be charged until a sustain voltage Vs. At this time, the third node N 33  remains at an ½ sustain voltage with the aid of turning-on of the first switch S 31 . A resonant pulse rises into more than the ½ sustain voltage Vs/2 by the LC serial resonance circuit at the second node N 32 , but is blocked by the first diode D 31  to maintain the ½ sustain voltage Vs/2. As a result, the panel capacitor Cp is supplied with the sustain voltage Vs that is made by a combination of the ½ sustain voltage Vs/2 at the second node N 32  and a voltage charged in the charge capacitor Cc.  
         [0108]    Thereafter, in a T 2  interval, the first switch S 31  is kept at an ON state and the second switch S 32  is turned on. Further, the third and fourth switches S 33  and S 34  is kept at an OFF state. At this time, the panel capacitor Cp is supplied, via the third and second nodes N 33  and N 32 , with a voltage that is made by a combination of a voltage from the ½ sustain voltage source Vs/2 and a voltage of the charge capacitor Cd to thereby maintain the sustain voltage Vs. During the T 2  interval, the charge capacitor Cc remains at the ½ sustain voltage Vs/2 by a voltage supplied via the first switch S 31  because the first switch S 31  has been kept at an ON state. To this end, a turning-off time of the first switch S 31  becomes equal to that of the second switch S 32 . The third diode D 33  shuts off a current path such that a current of the charge capacitor Cc does not flow through the ½ sustain voltage source Vs/2.  
         [0109]    In a T 3  interval, the third switch S 33  is turned on. In the T 3  interval, the first and second switches S 31  and S 32  are turned off and the fourth switch S 34  is kept at an OFF state. Accordingly, the panel capacitor Cp is discharged, and a voltage component of a reactive power discharged from the panel capacitor Cp is recovered and charged, via the inductor L, the second diode D 32  and the third switch S 33 , into the charge capacitor Cc. At this time, the inductor L configures a resonance circuit along with the panel capacitor Cp. Accordingly, a voltage of the panel-capacitor Cp drops into the ground voltage GND.  
         [0110]    In the sustain driving apparatus of the PDP according to the first embodiment of the present invention, the sustain pulse supplied to the panel capacitor Cp is generated with repeating the T 1  to T 4  intervals periodically.  
         [0111]    In the sustain driving apparatus of the PDP according to the first embodiment of the present invention, the charge capacitor is directly connected to the ½ sustain voltage to thereby apply an addition of the ½ sustain voltage and the charge capacitor voltage to the panel. Accordingly, the sustain driving apparatus of the PDP according to the first embodiment of the present invention can lower the sustain voltage to ½ in comparison to the conventional sustain driving apparatus of the PDP to thereby reduce power consumption to that extent, and supplies a stable sustain voltage in the discharge sustain period using the boosted voltage to thereby stabilize a driving waveform. Furthermore, the sustain driving apparatus of the PDP according to the first embodiment of the present invention reduce the sustain voltage to ½ in comparison to the conventional sustain driving apparatus of the PDP to thereby lower resisting voltages of the switching devices from 200 volts in the prior art into 100 volts, so that the switching devices can be configured by low-voltage switching devices to reduce a cost.  
         [0112]    Referring to FIG. 8, a sustain driving apparatus of a PDP according to a second embodiment of the present invention further includes a fourth diode D 34  connected between the ½ sustain voltage source Vs/2 and the fourth node N 34  in comparison to the sustain driving apparatus of the PDP according to the first embodiment shown in FIG. 5.  
         [0113]    Since elements other than the fourth diode D 34  in the sustain driving apparatus of the PDP according to the second embodiment are identical to those of the sustain driving apparatus of the PDP according to the first embodiment, configuration and operation explanations as to those element will be omitted.  
         [0114]    In the sustain driving apparatus of the PDP according to the second embodiment, a supply voltage from a ½ sustain voltage source Vs/2 is applied, via a fourth diode D 34 , to a charge capacitor Cc, an inductor L and a panel capacitor Cp, thereby separating the ½ sustain voltage source Vs/2 from the sustain driving apparatus. Accordingly, the sustain driving apparatus of the PDP according to the second embodiment of the present invention can provide more stable voltage supply and driving.  
         [0115]    Referring to FIG. 9, there is shown a sustain driving apparatus of a plasma display panel according to a third embodiment of the present invention.  
         [0116]    The sustain driving apparatus includes an ½ sustain voltage source Vs/2, first and second switches S 41  and S 43  connected to the ½ sustain voltage source Vs/2, second and fourth switches S 42  and S 44  connected, in parallel, to a first electrode of the panel capacitor Cp; and an inductor L connected between a first node N 41  positioned between the first and third switches S 41  and S 43  and a second node N 42  positioned between the second and fourth switches S 42  and S 44 , a first diode D 41  connected between a first terminal of the first switch S 41  and the first node N 41 , a second diode D 42  connected between the first node N 41  and the first terminal of the third switch S 43 , a third diode D 43  connected between the first switch S 41  and the second switch S 42 , a fifth switch S 45  connected between a third node N 43  positioned between the second switch S 42  and the third diode D 43  and a ground voltage source GND, a charge capacitor Cc connected between the fifth switch S 55  and the third node N 43 , and a connection line SL for electrically coupling a fourth node N 44  between the first switch S 41  and the first diode D 41  and a fifth node N 45  between the fifth switch S 45  and the charge capacitor Cc.  
         [0117]    Herein, the panel capacitor Cp is an equivalent expression of a capacitance value of the PDP. Each switch S 41  to S 45  is implemented by a semiconductor switching device such as MOS FET, IGBT or BJT, etc.  
         [0118]    The first to third diodes D 41 , D 42  and D 43  play a role to form a current path only in a constant direction. In other words, the first diode D 41  shuts off a reverse current flowing from the panel capacitor Cp into the first switch S 41  while the second diode D 42  shuts off a reverse current flowing from the ½ sustain voltage source Vs/2 into the inductor L. Further, the third diode D 43  shuts off a reverse current flowing from the third node N 43  into the ½ sustain voltage source Vs/2. The third diode D 43  forces a Vs voltage charged by the charge capacitor Cc to make no affect to the ½ sustain voltage source Vs/2.  
         [0119]    The charge capacitor Cc charges a voltage from the  1 / 2  sustain voltage source Vs/2. The voltage Vs/2 charged in the charge capacitor Cs is added to a voltage supplied from the ½ sustain voltage source Vs/2 to apply the added voltage to the panel capacitor Cp.  
         [0120]    An operation of the sustain driving apparatus of the PDP according to the third embodiment of the present invention will be described in conjunction with FIG. 10 below.  
         [0121]    Herein, a waveform VN 42  in FIG. 10 represents a voltage at the second node N 42  that is an output node.  
         [0122]    First, in a T 4  interval, the fourth and fifth switches S 44  and S 45  keep an ON state while the first to third switches S 41  to S 43  keep an OFF state. Accordingly, the first terminal of the charge capacitor Cc is connected, via the third node N 43  and the third diode D 43 , to the ½ sustain voltage source Vs/2 while the second terminal thereof is connected, via the fifth node N 45  and the fifth switch S 45 , to the ground voltage source GND. As a result, the  1 / 2  sustain voltage Vs/2 from the ½ sustain voltage source Vs/2 is charged into the charge capacitor Cc. Further, in the T 4  interval, the panel capacitor Cp charges a ground voltage GND from the ground voltage source GND through the fourth switch S 44 . Meanwhile, as the fifth switch S 45  keeps an ON state in the T 4  interval, it allows a voltage at the second node N 42  to drop into a ground level along with the fourth switch S 44 , thereby providing a stable charging of the ½ sustain voltage Vs/2 into the charge capacitor Cd.  
         [0123]    Then, in a T 1  interval, the fourth and fifth switches S 44  and S 45  is turned off and the first switch S 41  is turned on. As the first switch S 41  is turned on, a supply voltage from the ½ sustain voltage source Vs/2 charges the panel capacitor Cp via the first switch S 41 , the fourth node N 44 , the first diode D 41 , the first node N 41  and the inductor L. During the T 1  interval, the panel capacitor Cp configures an LC serial resonance circuit along with the inductor L to be charged until a sustain voltage Vs. At this time, the third node N 33  remains at an ½ sustain voltage with the aid of turning-on of the first switch S 41 . A resonant pulse rises into more than the ½ sustain voltage Vs/2 by the LC serial resonance circuit at the second node N 42 , but is blocked by the first diode D 41  to maintain the ½ sustain voltage Vs/2. As a result, an addition of the ½ sustain voltage Vs/2 at the second node N 32  and a voltage charged in the charge capacitor Cc becomes the sustain voltage Vs.  
         [0124]    Thereafter, in a T 2  interval, the second switch S 42  is turned on and the first switch S 41  keeps an ON state. Further, the third and fourth switches S 43  and S 44  is kept at an OFF state. At this time, the panel capacitor Cp is supplied, via the second and third nodes N 42  and N 43 , with a boosted voltage that is made by an addition of a voltage from the ½ sustain voltage source Vs/2 and a voltage of the charge capacitor Cp to thereby maintain the sustain voltage Vs. During the T 2  interval, the charge capacitor Cc remains at the ½ sustain voltage Vs/2 by a voltage supplied via the first switch S 41  because the first switch S 41  has been kept at an ON state. To this end, a turning-off time of the first switch S 41  becomes equal to that of the second switch S 42 . The third diode D 43  shuts off a current path such that a current of the charge capacitor Cc does not flow through the ½ sustain voltage source Vs/2.  
         [0125]    In a T 3  interval, the third and fifth switches S 43  and S 45  are turned on while the fourth switch S 44  keeps an OFF state. In this case, the fifth switch S 45  may be turned on in the above T 3  interval or only in a T 4  interval. Accordingly, the panel capacitor Cp is discharged, and a voltage component of a reactive power discharged from the panel capacitor Cp is recovered and charged, via the inductor L, the second diode D 42  and the third switch S 43 , into the charge capacitor Cc. At this time, the inductor L configures a resonance circuit along with the panel capacitor Cp. Accordingly, a voltage of the panel capacitor Cp drops into the ground voltage GND.  
         [0126]    In the sustain driving apparatus of the PDP according to the third embodiment of the present invention, the sustain pulse supplied to the panel capacitor Cp is generated with repeating the T 1  to T 4  intervals periodically.  
         [0127]    In the sustain driving apparatus of the PDP according to the third embodiment of the present invention, the charge capacitor is directly connected to the ½ sustain voltage to thereby apply an addition of the ½ sustain voltage and the charge capacitor voltage to the panel. Accordingly, the sustain driving apparatus of the PDP according to the third embodiment of the present invention can lower the sustain voltage to ½ in comparison to the conventional sustain driving apparatus of the PDP to thereby reduce power consumption to that extent, and supplies a stable sustain voltage in the discharge sustain period using the boosted voltage to thereby stabilize a driving waveform. Furthermore, the sustain driving apparatus of the PDP according to the third embodiment of the present invention reduce the sustain voltage to ½ in comparison to the conventional sustain driving apparatus of the PDP to thereby lower resisting voltages of the switching devices from 200 volts in the prior art into 100 volts, so that the switching devices can be configured by low-voltage switching devices to reduce a cost.  
         [0128]    Referring to FIG. 11, there is shown a sustain driving apparatus of a plasma display panel according to a fourth embodiment of the present invention.  
         [0129]    The sustain driving apparatus includes an ½ sustain voltage source Vs/2, a fourth diode D 54  and an inductor L connected between the ½ sustain voltage source Vs/2 and the panel capacitor Cp, first and second switches S 51  and S 53  connected, in parallel, to a first node N 1  between the fourth diode D 54  and the inductor L, a first diode D 51  connected between the first switch S 51  and the first node N 51 , a second diode D 52  connected between the first node N 51  and the third switch S 53 , a charge capacitor Cc and a third diode D 53  connected between a second node N 52  positioned between the first switch S 51  and the first diode D 51  and the ½ sustain voltage source Vs/2, a sustain capacitor Cs connected between the third node N 53  positioned between the charge capacitor Cc and the third diode D 53  and a ground voltage source GND, a fifth diode D 55  connected between the sustain capacitor Cs and the third node N 53 , a second switch S 52  connected between a fourth node N 54  positioned between the inductor L and the panel capacitor Cp and a node positioned between the fifth diode D 55  and the sustain capacitor Cs, and a fourth switch S 54  connected between the fourth node N 54  and the ground voltage source GND.  
         [0130]    Herein, the panel capacitor Cp is an equivalent expression of a capacitance value of the PDP, and the first terminal of the panel capacitor is connected to the fourth node N 54  while the second terminal thereof is connected to the ground voltage source GND. Each switch S 41  to S 45  is implemented by a semiconductor switching device such as MOS FET, IGBT or BJT, etc.  
         [0131]    The first to third diodes D 51  to D 53  play a role to shut off a reverse current. The first terminal of the fourth diode D 54  is connected to the ½ sustain voltage source Vs/2 while the second terminal thereof is connected to the first and third terminals S 51  and S 53 . Such a fourth diode D 54  applies a supply voltage from the ½ sustain voltage source Vs/2 separately from the sustain driving apparatus upon failure of the ½ sustain voltage source, to thereby permit more stable voltage supply and driving. The fifth diode D 55  prevents a Vs voltage charged in the charge capacitor Cc from being flown into the ½ sustain voltage source Vs/2.  
         [0132]    The charge capacitor Cc is supplied with a ½ sustain voltage Vs/2 from the ½ sustain voltage source Vs/2 to be charged into the sustain voltage Vs with the aid of a boosting circuit. The sustain capacitor Cs is charged by a sustain voltage Vs applied from the charge capacitor Cs. The sustain voltage Vs charged in the sustain capacitor Cs plays a role to provide a stable sustaining of the sustain voltage Vs when the sustain voltage Vs of the charge capacitor Cs is applied to the panel capacitor Cp. In other words, a sustain voltage Vs applied to the panel capacitor Cp from the charge capacitor Cc provides a stable sustaining of the sustain voltage Vs by the sustain capacitor Cs.  
         [0133]    An operation of the sustain driving apparatus of the PDP according to the fourth embodiment of the present invention will be described in conjunction with FIG. 12 below.  
         [0134]    Herein, a waveform Vout in FIG. 12 represents an output voltage at the fourth node N 54 .  
         [0135]    First, in a T 4  interval, the fourth switch S 54  is turned on. As the fourth switch S 54  is turned on, a current path extended, via the ½ sustain voltage source Vs/2, the third diode D 53 , the charge capacitor Cc, the first diode D 51 , the inductor L and the fourth switch S 54 , into the ground voltage source GND is formed. At this time, an ½ sustain voltage Vs/2 is charged into the charge capacitor Cp. Further, the panel capacitor Cp is connected, via the fourth switch S 54 , to the ground voltage source GND to charge a ground voltage.  
         [0136]    Then, in a T 1  interval, the first switch S 51  is turned on while the fourth switch S 54  is turned off. As the first switch S 51  is turned on, a current path extended, via the ½ sustain voltage source Vs/2, the fourth diode D 54 , the first switch S 51 , the charge capacitor Cc, the fifth diode D 55  and the sustain capacitor Cs, into the ground voltage source GND. At this time, a boosted voltage added to the ½ sustain voltage Vs/2 charged in the charge capacitor Cc in the T 4  interval charges the sustain voltage Vs into the sustain capacitor Cs via the fifth diode D 55 . More specifically, the ½ sustain voltage Vs/2 charged in the charge capacitor Cc in the T 4  interval is coupled with the ground voltage source GND to be charged to that extent. Accordingly, a reference voltage level becomes the ½ sustain voltage Vs/2 charged in the charge capacitor Cc in the T 4  interval rather than the ground voltage GND when the ½ sustain voltage Vs/2 is applied to the charge capacitor Cc in the T 1  interval. A boosted voltage made by an addition of the ½ sustain voltage Vs/2 charged in the T 1  interval and the ½ sustain voltage Vs/2 previously charged in the charge capacitor Cc is charged, via the fifth diode D 55 , into the sustain capacitor Cs.  
         [0137]    Further, if the first switch S 51  is turned on in the T 1  interval, then a current path extended, via the ½ sustain voltage source Vs/2, the fourth diode D 54 , the first switch S 51 , the inductor L and the panel capacitor Cp, into the ground voltage source GND is formed. At this time, the panel capacitor Cp configures an LC serial resonance circuit along with the inductor L to be charged until the sustain voltage Vs.  
         [0138]    In a T 2  interval, the second switch S 52  is turned on while the first switch S 51  keeps an ON state. As the second switch S 52  is turned on, a current path extending, via the ½ sustain voltage source Vs/2, the fourth diode D 54 , the first switch S 51 , the charge capacitor Cc, the fifth diode D 55 , the second switch S 52  and the panel capacitor Cp, into the ground voltage source GND is formed. Accordingly, the panel capacitor Cp is supplied, via the fifth diode D 55  and the second switch S 52 , with a boosted voltage made by an addition of a voltage from the ½ sustain voltage source Vs/2 and a voltage of the charge capacitor Cc, thereby maintaining the sustain voltage Vs.  
         [0139]    In the T 2  interval, the third diode D 53  blocks the current path such that a current of the charge capacitor Cc does not flow through the ½ sustain voltage source Vs/2. Further, the third node N 53  between the third diode D 53  and the charge capacitor Cc is loaded with a voltage changing from the ½ sustain voltage Vs/2 until the sustain voltage Vs. Accordingly, when the above-mentioned voltage is applied, via the second switch S 52 , to the panel capacitor Cp, an application of the sustain voltage Vs does not raise a problem, but an application of a voltage lower than the sustain voltage Vs may fail to supply a sufficient power. Therefore, if an insufficient voltage is applied from the charge capacitor Cc to the panel capacitor Cp, then a voltage having been charged in the charge capacitor Cd is charged into the sustain capacitor Cs to add a voltage having been charged in the sustain capacitor Cs, thereby supplying a sufficient power. At this time, the fifth diode D 55  prevents the sustain voltage Vs charged in the sustain capacitor Cs from being flown into the charge capacitor Cc. Accordingly, it becomes possible to maintain a stable sustain voltage with the aid of the sustain capacitor Cs even though the ½ sustain voltage source Vs/2 has been used.  
         [0140]    In a T 3  interval, the third switch S 53  is turned on while the first and second switches S 51  and S 52  are turned off. Accordingly, the panel capacitor Cp is discharged, and a voltage component of a reactive power discharged from the panel capacitor Cp is vanished by the inductor L, the second diode D 52  and the third switch S 53 . At this time, the fourth diode D 4  shuts off a flow of the discharge current into the ½ sustain voltage source V/e.  
         [0141]    In the sustain driving apparatus of the PDP according to the fourth embodiment of the present invention, the sustain pulse supplied to the panel capacitor Cp is generated with repeating the T 1  to T 4  intervals periodically.  
         [0142]    [0142]FIG. 13 is a graph representing a driving waveform of the sustain driving apparatus of the plasma display panel according to an experiment for the apparatus of FIG. 12.  
         [0143]    As shown in FIG. 13, since the sustain voltage is approximately 180V, the charge capacitor Cp is loaded with a voltage changing from 90V until 180V. Accordingly, since a sufficient power cannot be supplied by a voltage lower than 180V, the circuit is attached with the sustain capacitor Cs capable of charging the sustain voltage Vs to supply an always constant sustain voltage Vs as seen from {circle over (2)} in the graph. Herein, a waveform {circle over (1/)} represents a finally output waveform; a waveform {circle over (2)} represents a waveform of a voltage loaded at a Vs position of FIG. 11, which is constantly kept at a sustain voltage Vs by the sustain capacitor Cs; and a waveform {circle over (3)} represents a waveform of voltage loaded on the third node N 53  between the third diode D 53  and the charge capacitor Cc.  
         [0144]    The sustain driving apparatus of the PDP according to the fourth embodiment of the present invention can conduct a driving with lowering the sustain discharge voltage into an half without any characteristic change of the sustain discharge, and always constantly maintain the sustain voltage at the circuit even upon application of the ½ sustain voltage to permit a stable driving.  
         [0145]    Referring to FIG. 14, there is shown a sustain driving apparatus of a plasma display panel according to a fifth embodiment of the present invention.  
         [0146]    The sustain driving apparatus includes an ½ sustain voltage source Vs/2, a fourth diode  5 D 4  and an inductor L connected between the ½ sustain voltage source Vs/2 and a panel capacitor Cp, first and second switches  5 S 1  and  5 S 3  connected, in parallel, to a first node  5 N 1  between the fourth diode  5 D 4  and the inductor L, a first diode  5 D 1  connected between the first switch  5 S 1  and the first node  5 N 1 , a second diode  5 D 2  connected between the first node  5 N 1  and the third switch  5 S 3 , a charge capacitor Cc and a third diode  5 D 3  connected between a second node  5 N 2  positioned between the first switch  5 S 1  and the first diode  5 D 1  and the ½ sustain voltage source Vs/2, a second switch  5 S 2  connected between a third node  5 N 3  positioned between the charge capacitor Cc and the third diode  5 D 3  and a fourth node  5 N 4  positioned between the inductor L and the panel capacitor Cp, and a fourth switch  5 S 4  connected between the fourth node  5 N 4  and the ground voltage source GND.  
         [0147]    Herein, the panel capacitor Cp is an equivalent expression of a capacitance value of the PDP, and the first terminal of the panel capacitor is connected to the fourth node  5 N 4  while the second terminal thereof is connected to the ground voltage source GND. Each switch  5 S 1  to  5 S 4  is implemented by a semiconductor switching device such as MOS FET, IGBT or BJT, etc.  
         [0148]    The first to third diodes  5 D 1  to  5 D 3  play a role to shut off a reverse current. The first terminal of the fourth diode  5 D 4  is connected to the ½ sustain voltage source Vs/2 while the second terminal thereof is connected to the first and third switches  5 S 1  and  5 S 3 . Such a fourth diode  5 D 4  applies a supply voltage from the ½ sustain voltage source Vs/2 separately from the sustain driving apparatus upon failure of the ½ sustain voltage source, to thereby permit more stable voltage supply and driving.  
         [0149]    The charge capacitor Cc charges a voltage by the ½ sustain voltage source Vs/2. The voltage Vs/2 charged in the charge capacitor Cc is added to a voltage supplied from the ½ sustain voltage source Vs/2 to apply the sustain voltage Vs to the panel capacitor Cp.  
         [0150]    An operation of the sustain driving apparatus of the PDP according to the fifth embodiment of the present invention will be described in conjunction with FIG. 15 below.  
         [0151]    Herein, a waveform Vout in FIG. 15 represents an output voltage at the fourth node  5 N 4 .  
         [0152]    First, in a T 4  interval, the fourth switch  5 S 4  keeps an ON state while the first to third switches  5 S 1  to  5 S 3  keep an OFF state. At this time, the charge capacitor Cc is connected, via the third node  5 N 3  and the third diode  5 D 3 , to the ½ sustain voltage source Vs/2. Accordingly, an ½ sustain voltage Vs/2 is charged into the charge capacitor Cc. In other words, since the fourth switch  5 S 4  is turned on to thereby drop the second node  5 N 2 , via the first diode  5 D 1  and the inductor L, into the ground level GND, the (−) terminal of the charge capacitor Cc is connected to the ground voltage source GND. Therefore, the charge capacitor Cc charges an ½ sustain voltage Vs/2 applied to the (+) terminal thereof by way of the third node  5 N 3  connected to the third node  5 N 3 . Further, in the T 1  interval, the panel capacitor Cp is connected, via the fourth switch  5 S 4 , to the ground voltage source GND to charge a ground voltage GND.  
         [0153]    Then, in a T 1  interval, the fourth switch  5 S 4  is turned off; the first switch  5 S 1  is turned on; and the second and third switches  5 S 2  and  5 S 3  are maintained at an OFF state. As the first switch  5 S 1  is turned on, a supply voltage from the ½ sustain voltage source Vs/2 charges the panel capacitor Cp via the fourth diode  5 D 4 , the first diode  5 D 1  and the inductor L. During the T 1  interval, the panel capacitor Cp configures an LC serial resonance circuit along with the inductor L to be charged until a sustain voltage Vs. At this time, the second node  5 N 2  remains at an ½ sustain voltage with the aid of turning-on of the first switch  5 S 1 . A resonant pulse rises into more than the ½ sustain voltage Vs/2 by the LC serial resonance circuit at the fourth node  5 N 4 , but is blocked by the first diode  5 D 1  to maintain the ½ sustain voltage Vs/2. As a result, in the T 1  interval, the ½ sustain voltage Vs/2 at the fourth  5 N 4  is added to the ½ sustain voltage previously charged in the charge capacitor Cc to thereby obtain a desired sustain voltage Vs.  
         [0154]    Thereafter, in a T 2  interval, the second switch  5 S 2  is turned on while the first switch  5 S 1  keeps an ON state. Further, the third and fourth switches  5 S 3  and  5 S 4  is kept at an OFF state. At this time, the panel capacitor Cp is supplied, via the third and fourth nodes  5 N 3  and  5 N 4 , with a boosted voltage that is made by an addition of a voltage from the ½ sustain voltage source Vs/2 and a voltage of the charge capacitor Cc to thereby maintain the sustain voltage Vs. During the T 2  interval, the charge capacitor Cc remains at the ½ sustain voltage Vs/2 by a voltage supplied via the first switch  5 S 1  because the first switch  5 S 1  has been kept at an ON state. To this end, a turning-off time of the first switch  5 S 1  becomes equal to that of the second switch  5 S 2 . The third diode  5 D 3  shuts off a current path such that a current of the charge capacitor Cc does not flow through the ½ sustain voltage source Vs/2.  
         [0155]    In a T 3  interval, the third switch  5 S 3  is turned on. In the T 3  interval, the first and second switches  5 S 1  and  5 S 2  are turned off and the fourth switch  5 S 4  is kept at an OFF state. Accordingly, the panel capacitor Cp is discharged, and a voltage component of a reactive power discharged from the panel capacitor Cp is vanished by the inductor L, the second diode  5 D 2  and the third switch  5 S 3 . At this time, the fourth diode  5 D 4  prevents the discharge current from being flown into the ½ sustain voltage source Vs/2.  
         [0156]    In the sustain driving apparatus of the PDP according to the fifth embodiment of the present invention, the sustain pulse supplied to the panel capacitor Cp is generated with repeating the T 1  to T 4  intervals periodically.  
         [0157]    In the sustain driving apparatus of the PDP according to the fifth embodiment of the present invention, the charge capacitor is directly connected to the ½ sustain voltage to thereby apply an addition of the ½ sustain voltage and the charge capacitor voltage to the panel. Further, a charge path of the charge capacitor is driven separately from a charge/discharge path of the panel. Accordingly, the sustain driving apparatus of the PDP according to the fifth embodiment of the present invention can lower the sustain voltage to ½ in comparison to the conventional sustain driving apparatus of the PDP to thereby reduce power consumption to that extent, and supplies a stable sustain voltage in the discharge sustain period using the boosted voltage to thereby stabilize a driving waveform.  
         [0158]    Referring to FIG. 16, there is shown a sustain driving apparatus of a plasma display panel according to a sixth embodiment of the present invention.  
         [0159]    The sustain driving apparatus includes an ½ sustain voltage source Vs/2, a first inductor L 1  connected between the ½ sustain voltage source Vs/2 and a fourth node  6 N 4  connected to a first terminal of the panel capacitor Cp, a fourth diode  6 D 4  connected between the first inductor L 1  and the ½ sustain voltage source Vs/2, a second diode  6 D 2  connected between the fourth diode  6 D 4  and the first inductor L 1 , first and third switches  6 S 1  and  6 S 3  connected, in parallel, to a first node  6 N 1  between the fourth diode  6 D 4  and the second diode  6 D 2 , a second inductor L 2  connected between the first switch  6 S 1  and the fourth node  6 N 4 , a first diode  6 D 1  connected between the first switch  6 S 1  and the second inductor L 2 , a third diode  6 D 3  and a second switch  6 S 2  connected between a node positioned between the second inductor L 2  and the fourth node  6 N 4  and the first node  6 N 1 , a charge capacitor Cc connected between a second node  6 N 2  positioned between the second switch  6 S 2  and the third diode  6 D 3  and a third node  6 N 3  positioned between the first switch  6 S 1  and the second inductor L 2 , and a fourth switch  6 S 4  connected between a node positioned between the first inductor L 1  and the fourth node  6 N 4  and a ground voltage source GND.  
         [0160]    Herein, the panel capacitor Cp is an equivalent expression of a capacitance value of the PDP, and the first terminal of the panel capacitor is connected to the fourth node  6 N 4  while the second terminal thereof is connected to the ground voltage source GND. Each switch  6 S 1  to  6 S 4  is implemented by a semiconductor switching device such as MOS FET, IGBT or BJT, etc.  
         [0161]    The first diode  6 D 1  shuts off a reverse current flowing from the panel capacitor Cp into the third node  6 N 3  while the second diode  6 D 2  shuts off a reverse current flowing from the first node  6 N 1  into the first inductor L 1 . Further, the third diode  6 D 3  shuts off a reverse current flowing from the second node  6 N 2  into the first node  6 N 1  while the fourth diode  6 D 4  plays a role to provide a stable application of a supply voltage from the ½ sustain voltage source Vs/2 into the charge capacitor Cc.  
         [0162]    An inductance of the first inductor L 1  is set largely enough to enhance a recovery efficiency of reactive power upon the panel discharge, whereas an inductance of the second inductor L 2  is set at a small value such that a rising time of a driving waveform upon the panel charge becomes fast.  
         [0163]    The charge capacitor Cc charges a voltage by the ½ sustain voltage source Vs/2. The voltage Vs/2 charged in the charge capacitor Cc is added to a voltage supplied from the ½ sustain voltage source Vs/2 to apply the sustain voltage Vs to the panel capacitor Cp.  
         [0164]    An operation of the sustain driving apparatus of the PDP according to the sixth embodiment of the present invention will be described in conjunction with FIG. 17 below.  
         [0165]    Herein, a waveform Vout in FIG. 17 represents an output voltage at the fourth node  6 N 4 .  
         [0166]    First, in a T 4  interval, the fourth switch  6 S 4  keeps an ON state while the first to third switches  6 S 1  to  6 S 3  keep an OFF state. One terminal of the charge capacitor Cc is connected, via the fourth and third diodes  6 D 4  and  6 D 3 , to the ½ sustain voltage source Vs/2 while other terminal thereof is connected, via the third node  6 N 3 , the second inductor L 2 , the fourth node  6 N 4  and the fourth switch  6 S 4 , to the ground voltage source GND. Accordingly, the charge capacitor Cc charges a voltage supplied via the fourth and third diodes  6 D 4  and  6 D 3  into the ½ sustain voltage Vs/2. Further, in the T 4  interval, the panel capacitor Cp is connected, via the fourth switch  6 S 4 , to the ground voltage source GND to charge a ground voltage GND.  
         [0167]    Meanwhile, the charge capacitor Cc has no problem related to the a voltage charge because the fourth switch  6 S 4  is charged even in any turned-on interval of a sub-field operation period other than the discharge sustain period.  
         [0168]    Then, in a T 1  interval, the fourth switch  6 S 4  is turned off; the first switch  6 S 1  is turned on; and the second and third switches  6 S 2  and  6 S 3  are maintained at an OFF state. As the first switch  6 S 1  is turned on, a supply voltage from the ½ sustain voltage source Vs/2 is charged into the panel capacitor Cp via the fourth diode  6 D 4 , the first switch  6 S 1 , the first diode  6 D 1  and the second inductor L 2 . During the T 1  interval, the panel capacitor Cp configures an LC serial resonance circuit along with the inductor L 2  to be charged until a sustain voltage Vs. At the same time, the charge capacitor Cc allows a reverse current from the panel capacitor Cp to be blocked by the first diode  6 D 1  and allows the ½ sustain voltage Vs/2 to be maintained by a voltage supplied from the ½ sustain voltage source Vs/2 by way of the third diode  6 D 3 .  
         [0169]    Thereafter, in a T 2  interval, the second switch  6 S 2  is turned on while the first switch  6 S 1  keeps an ON state. Further, the third and fourth switches  6 S 3  and  6 S 4  is kept at an OFF state. At this time, the panel capacitor Cp is supplied, via the second switch  6 S 2  and the fourth node  6 N 4 , with a boosted voltage that is made by an addition of a voltage from the ½ sustain voltage source Vs/2 and a voltage of the charge capacitor Cc to thereby maintain the sustain voltage Vs. During the T 2  interval, the charge capacitor Cc remains at the ½ sustain voltage Vs/2 by a voltage supplied via the first switch  6 S 1  because the first switch  6 S 1  has been kept at an ON state. To this end, a turning-off time of the first switch  6 S 1  becomes equal to that of the second switch  6 S 2 . The third diode  6 D 3  shuts off a current path such that a current of the charge capacitor Cc does not flow through the ½ sustain voltage source Vs/2.  
         [0170]    In a T 3  interval, the third switch  6 S 3  is turned on. In the T 3  interval, the first and second switches  6 S 1  and  6 S 2  are turned off and the fourth switch  6 S 4  is kept at an OFF state. Accordingly, the panel capacitor Cp is discharged, and a voltage component of a reactive power discharged from the panel capacitor Cp is vanished by the first inductor L 1 , the second diode  6 D 2 , the third switch  6 S 3 , the third diode  6 D 3  and the charge capacitor Cc.  
         [0171]    In the sustain driving apparatus of the PDP according to the sixth embodiment of the present invention, the sustain pulse supplied to the panel capacitor Cp is generated with repeating the T 1  to T 4  intervals periodically.  
         [0172]    In the sustain driving apparatus of the PDP according to the sixth embodiment of the present invention, the charge capacitor is directly connected to the ½ sustain voltage to thereby apply an addition of the ½ sustain voltage and the charge capacitor voltage to the panel. Accordingly, the sustain driving apparatus of the PDP according to the sixth embodiment of the present invention can lower the sustain voltage to ½ in comparison to the conventional sustain driving apparatus of the PDP to thereby reduce power consumption to that extent, and supplies a stable sustain voltage in the discharge sustain period using the boosted voltage to thereby stabilize a driving waveform. Furthermore, the sustain driving apparatus of the PDP according to the sixth embodiment of the present invention reduce the sustain voltage to ½ in comparison to the conventional sustain driving apparatus of the PDP to thereby lower resisting voltages of the switching devices from 200 volts in the prior art into 100 volts, so that the switching devices can be configured by low-voltage switching devices to reduce a cost.  
         [0173]    Referring to FIG. 18, there is shown a sustain driving apparatus of a plasma display panel according to a seventh embodiment of the present invention.  
         [0174]    The sustain driving apparatus includes an ½ sustain voltage source Vs/2, a first inductor L 1  connected between the ½ sustain voltage source Vs/2 and a fourth node  7 N 4  connected to a first terminal of the panel capacitor Cp, a fourth diode  7 D 4  connected between the first inductor L 1  and the ½ sustain voltage source Vs/2, a second diode  7 D 2  connected between the fourth diode  7 D 4  and the first inductor L 1 , first and third switches  7 S 1  and  7 S 3  connected, in parallel, to a first node  7 N 1  between the fourth diode  7 D 4  and the second diode  7 D 2 , a second inductor L 2  connected between the first switch  7 S 1  and the fourth node  7 N 4 , a first diode  7 D 1  connected between the first switch  7 S 1  and the second inductor L 2 , a third diode  7 D 3 , a fifth diode  7 D 5  and a sustain capacitor Cs connected between a fifth node  7 N 5  positioned between the ½ sustain voltage source Vs/2 and the fourth diode  7 D 4  and a ground voltage source GND, a second switch  7 S 2  connected between a sixth node  7 N 6  positioned between the sustain capacitor Cs and the fifth diode  7 D 5  and a node positioned between the second inductor L 2  and the fourth node  7 N 4 , a charge capacitor Cc connected between a second node  7 N 2  positioned between the third diode  7 D 3  and the fifth diode  7 D 5  and a third node  7 N 3  positioned between the first switch  7 S 1  and the first diode  7 D 1 , and a fourth switch  7 S 4  connected between a node positioned between the first inductor L 1  and the fourth node  7 N 4  and a ground voltage source GND.  
         [0175]    Herein, the panel capacitor Cp is an equivalent expression of a capacitance value of the PDP, and the first terminal of the panel capacitor is connected to the fourth node  7 N 4  while the second terminal thereof is connected to the ground voltage source GND. Each switch  7 S 1  to  7 S 4  is implemented by a semiconductor switching device such as MOS FET, IGBT or BJT, etc.  
         [0176]    The first diode  7 D 1  shuts off a reverse current flowing from the panel capacitor Cp into the third node  7 N 3  while the second diode  7 D 2  shuts off a reverse current flowing from the first node  7 N 1  into the first inductor L 1 . Further, the third diode  7 D 3  shuts off a reverse current flowing from the second node  7 N 2  into the ½ sustain voltage source Vs/2 while the fourth diode  7 D 4  plays a role to provide a stable application of a supply voltage from the ½ sustain voltage source Vs/2 into the charge capacitor Cc. The fifth diode  7 D 5  shuts off a reverse current flowing from the sustain capacitor Cs into the second node  7 N 2 .  
         [0177]    An inductance of the first inductor L 1  is set largely enough to enhance a recovery efficiency of reactive power upon the panel discharge, whereas an inductance of the second inductor L 2  is set at a small value such that a rising time of a driving waveform upon the panel charge becomes fast.  
         [0178]    The charge capacitor Cc is supplied with the ½ sustain voltage Vs/2 from the ½ sustain voltage source Vs/2 to be charged into a sustain voltage Vs by means of a boosting circuit. The sustain capacitor Cs is charged by the sustain voltage Vs supplied from the charge capacitor Cs. At this time, the sustain voltage Vs charged in the sustain capacitor Cs plays a role to provide a stable sustaining of a sustain voltage Vs when the sustain voltage Vs of the charge capacitor Cc is applied to the panel capacitor Cp. In other words, the sustain voltage Vs applied to the panel capacitor Cp from the charge capacitor Cc provides a stable sustaining of the sustain voltage Vs by means of the sustain capacitor Cs.  
         [0179]    An operation of the sustain driving apparatus of the PDP according to the seventh embodiment of the present invention will be described in conjunction with FIG. 19 below.  
         [0180]    Herein, a waveform Vout in FIG. 19 represents an output voltage at the fourth node  7 N 4 .  
         [0181]    First, in a T 4  interval, the fourth switch  7 S 4  is turned on. As the fourth switch  7 S 4  is turned on, a current path extended from the ½ sustain voltage source Vs/2, via the third diode  7 D 3 , the charge capacitor Cc, the first diode  7 D 1 , the second inductor L 2  and the fourth switch  7 S 4 , into the ground voltage source GND is formed. At this time, an ½ sustain voltage Vs/2 is charged into the charge capacitor Cp. Further, as the fourth switch  7 S 4  is turned on, the panel capacitor Cp is connected, via the fourth switch  7 S 4 , to the ground voltage source GND to charge a ground voltage GND.  
         [0182]    Then, in a T 1  interval, the first switch  7 S 1  is turned on. As the first switch  7 S 1  is turned on, a current path extended from the ½ sustain voltage source Vs/2, via the fourth diode  7 D 4 , the first switch  7 S 1 , the first diode  7 D 1 , the second inductor L 2  and the panel capacitor Cp, into the ground voltage source GND is formed. Accordingly, the panel capacitor Cp configures an LC serial resonance circuit along with the inductor L to be charged until the sustain voltage Vs.  
         [0183]    Further, if the first switch  7 S 1  is turned on in the T 1  interval, then a current path extended, via the ½ sustain voltage source Vs/2, the third diode  7 D 3 , the fifth diode  7 D 5  and the sustain capacitor Cs, into the ground voltage source GND is formed. Accordingly, a boosted voltage added to the ½ sustain voltage Vs/2 charged in the charge capacitor Cc in the T 4  interval is charged into the sustain capacitor Cs via the fifth diode  7 D 5 . More specifically, a reference voltage level becomes the ½ sustain voltage Vs/2 charged in the charge capacitor Cc rather than the ground voltage GND when the ½ sustain voltage Vs/2 is applied to the charge capacitor Cc due to the ½ sustain voltage Vs/2 charged in the charge capacitor Cc in the T 4  interval. Accordingly, a boosted voltage made by an addition of the ½ sustain voltage Vs/2 charged in the charge capacitor Cc in the T 1  interval and the ½ sustain voltage Vs/2 previously charged in the charge capacitor Cc is charged, via the fifth diode  7 D 5 , into the sustain capacitor Cs.  
         [0184]    In a T 2  interval, the second switch  7 S 2  is turned on while the first switch  7 S 1  keeps an ON state. As the second switch  7 S 2  is turned on, a current path extending, via the ½ sustain voltage source Vs/2, the fourth diode  7 D 4 , the first switch  7 S 1 , the charge capacitor Cc, the fifth diode  7 D 5 , the second switch  7 S 2  and the panel capacitor Cp, into the ground voltage source GND is formed. Accordingly, the panel capacitor Cp is supplied, via the fifth diode  7 D 5  and the second switch  7 S 2 , with a boosted voltage made by an addition of a voltage from the ½ sustain voltage source Vs/2 and a voltage of the charge capacitor Cc, thereby maintaining the sustain voltage Vs. The third diode  7 D 3  blocks the current path such that a current of the charge capacitor Cc does not flow through the ½ sustain voltage source Vs/2.  
         [0185]    At this time, the second node  7 N 2  between the third diode  7 D 3  and the charge capacitor Cc is loaded with a voltage changing from the ½ sustain voltage Vs/2 until the sustain voltage Vs. Accordingly, when the above-mentioned voltage is applied, via the second switch  7 S 2 , to the panel capacitor Cp, an application of the sustain voltage Vs does not raise a problem, but an application of a voltage lower than the sustain voltage Vs may fail to supply a sufficient power. Therefore, if an insufficient voltage is applied from the charge capacitor Cc to the panel capacitor Cp, then a voltage having been charged in the charge capacitor Cc is charged into the sustain capacitor Cs to add a voltage having been charged in the sustain capacitor Cs, thereby supplying a sufficient power. At this time, the fifth diode  7 D 5  prevents the sustain voltage Vs charged in the sustain capacitor Cs from being flown into the charge capacitor Cc. Accordingly, it becomes possible to maintain a stable sustain voltage with the aid of the sustain capacitor Cs even though the ½ sustain voltage source Vs/2 has been used.  
         [0186]    In a T 3  interval, the third switch  7 S 3  is turned on. Accordingly, the panel capacitor Cp is discharged, and a voltage component of a reactive power discharged from the panel capacitor Cp is vanished by the first inductor L 1 , the second diode  7 D 2  and the third switch  7 S 3 . At this time, the fourth diode  7 D 4  shuts off a flow of the discharge current into the ½ sustain voltage source Vs/2.  
         [0187]    In the sustain driving apparatus of the PDP according to the seventh embodiment of the present invention, the sustain pulse supplied to the panel capacitor Cp is generated with repeating the T 1  to T 4  intervals periodically.  
         [0188]    The sustain driving apparatus of the PDP according to the seventh embodiment of the present invention can conduct a driving with lowering the sustain discharge voltage into an half without any characteristic change of the sustain discharge, and always constantly maintain the sustain voltage at the circuit even upon application of the ½ sustain voltage to permit a stable driving.  
         [0189]    Referring to FIG. 20, there is shown a sustain driving apparatus of a plasma display panel according to an eighth embodiment of the present invention.  
         [0190]    The sustain driving apparatus includes an ½ sustain voltage source Vs/2, a first inductor L 1  connected between the ½ sustain voltage source Vs/2 and a fourth node  8 N 4  connected to a first terminal of the panel capacitor Cp, a fourth diode  8 D 4  connected between the first inductor L 1  and the ½ sustain voltage source Vs/2, a second diode  8 D 2  connected between the fourth diode  8 D 4  and the first inductor L 1 , first and third switches  8 S 1  and  8 S 3  connected, in parallel, to a first node  8 N 1  between the fourth diode  8 D 4  and the second diode  8 D 2 , a second inductor L 2  connected between the first switch  8 S 1  and the fourth node  8 N 4 , a first diode  8 D 1  connected between the first switch  8 S 1  and the second inductor L 2 , a third diode  8 D 3  and a second switch  8 S 2  connected between a fifth node  8 N 5  positioned between the ½ sustain voltage source Vs/2 and the fourth diode  8 D 4  and a node positioned between the second inductor L 2  and the fourth node  8 N 4 , a charge capacitor Cc connected between a second node  8 N 2  positioned between the third diode  8 D 3  and the second switch  8 S 2  and a third node  8 N 3  positioned between the first switch  8 S 1  and the first diode  8 D 1 , and a fourth switch  8 S 4  connected between a node positioned between the first inductor L 1  and the fourth node  8 N 4  and a ground voltage source GND.  
         [0191]    Herein, the panel capacitor Cp is an equivalent expression of a capacitance value of the PDP, and the first terminal of the panel capacitor is connected to the fourth node  8 N 4  while the second terminal thereof is connected to the ground voltage source GND. Each switch  8 S 1  to  8 S 4  is implemented by a semiconductor switching device such as MOS FET, IGBT or BJT, etc.  
         [0192]    The first diode  8 D 1  shuts off a reverse current flowing from the panel capacitor Cp into the third node  8 N 3  while the second diode  8 D 2  shuts off a reverse current flowing from the first node  8 N 1  into the first inductor L 1 . Further, the third diode  8 D 3  shuts off a reverse current flowing from the second node  8 N 2  into the ½ sustain voltage source Vs/2 while the fourth diode  8 D 4  plays a role to provide a stable application of a supply voltage from the ½ sustain voltage source Vs/2 into the charge capacitor Cc.  
         [0193]    An inductance of the first inductor L 1  is set largely enough to enhance a recovery efficiency of reactive power upon the panel discharge, whereas an inductance of the second inductor L 2  is set at a small value such that a rising time of a driving waveform upon the panel charge becomes fast.  
         [0194]    The charge capacitor Cc is supplied with the ½ sustain voltage Vs/2 from the ½ sustain voltage source Vs/2 to be charged into a sustain voltage Vs by means of a boosting circuit.  
         [0195]    An operation of the sustain driving apparatus of the PDP according to the eighth embodiment of the present invention will be described in conjunction with FIG. 21 below.  
         [0196]    Herein, a waveform Vout in FIG. 21 represents an output voltage at the fourth node  8 N 4 .  
         [0197]    First, in a T 4  interval, the fourth switch  8 S 4  keeps an ON state while the first to third switches  8 S 1  to  8 S 3  keep an OFF state. One terminal of the charge capacitor Cc is connected, via the third diode  8 D 3 , to the ½ sustain voltage source Vs/2 while other terminal thereof is connected, via the third node  8 N 3 , the first diode  8 D 1 , the second inductor L 2 , the sixth node  8 N 6 , the fourth node  8 N 4  and the fourth switch  8 S 4 , to the ground voltage source GND. Accordingly, the charge capacitor Cc charges a voltage supplied via the third diode  8 D 3  into the ½ sustain voltage Vs/2. Further, in the T 4  interval, the panel capacitor Cp is connected, via the fourth switch  8 S 4 , to the ground voltage source GND to charge a ground voltage GND.  
         [0198]    Meanwhile, the charge capacitor Cc has no problem related to the a voltage charge because the fourth switch  8 S 4  is charged even in any turned-on interval of a sub-field operation period other than the discharge sustain period.  
         [0199]    Then, in a T 1  interval, the fourth switch  8 S 4  is turned off; the first switch  8 S 1  is turned on; and the second and third switches  8 S 2  and  8 S 3  are maintained at an OFF state. As the first switch  8 S 1  is turned on, a supply voltage from the ½ sustain voltage source Vs/2 is charged into the panel capacitor Cp via the fourth diode  8 D 4 , the first switch  8 S 1 , the first diode  8 D 1  and the second inductor L 2 . During the T 1  interval, the panel capacitor Cp configures an LC serial resonance circuit along with the inductor L 2  to be charged until a sustain voltage Vs. At the same time, the charge capacitor Cc allows a reverse current from the panel capacitor Cp to be blocked by the first diode  8 D 1  and allows the ½ sustain voltage Vs/2 to be maintained by a voltage supplied from the ½ sustain voltage source Vs/2 by way of the third diode  8 D 3 .  
         [0200]    Thereafter, in a T 2  interval, the second switch  8 S 2  is turned on while the first switch  8 S 1  keeps an ON state. Further, the third and fourth switches  8 S 3  and  8 S 4  are kept at an OFF state. At this time, the panel capacitor Cp is supplied, via the second switch  8 S 2  and the fourth node  8 N 4 , with a boosted voltage that is made by an addition of a voltage from the ½ sustain voltage source Vs/2 and a voltage of the charge capacitor Cc to thereby maintain the sustain voltage Vs. During the T 2  interval, the charge capacitor Cc remains at the ½ sustain voltage Vs/2 by a voltage supplied via the first switch  6 S 1  because the first switch  8 S 1  has been closed. To this end, a turning-off time of the first switch  8 S 1  becomes equal to that of the second switch  8 S 2 . The third diode  8 D 3  shuts off a current path such that a current of the charge capacitor Cc does not flow through the ½ sustain voltage source Vs/2.  
         [0201]    In a T 3  interval, the third switch  8 S 3  is turned on. In the T 3  interval, the first and second switches  8 S 1  and  8 S 2  are turned off and the fourth switch  8 S 4  is kept at an OFF state. Accordingly, the panel capacitor Cp is discharged, and a voltage component of a reactive power discharged from the panel capacitor Cp is vanished by the first inductor L 1 , the second diode  8 D 2  and the third switch  8 S 3 .  
         [0202]    In the sustain driving apparatus of the PDP according to the eighth embodiment of the present invention, the sustain pulse supplied to the panel capacitor Cp is generated with repeating the T 1  to T 4  intervals periodically.  
         [0203]    In the sustain driving apparatus of the PDP according to the eighth embodiment of the present invention, the charge capacitor is directly connected to the ½ sustain voltage to thereby apply an addition of the ½ sustain voltage and the charge capacitor voltage to the panel. Further, the charge path of the charge capacitor is driven separately from the charge/discharge path of the panel. Accordingly, the sustain driving apparatus of the PDP according to the eighth embodiment of the present invention can lower the sustain voltage to ½ in comparison to the conventional sustain driving apparatus of the PDP to thereby reduce power consumption to that extent, and supplies a stable sustain voltage in the discharge sustain period using the boosted voltage to thereby stabilize a driving waveform.  
         [0204]    Referring to FIG. 22, a sustain driving apparatus of a PDP according to a ninth embodiment of the present invention includes a panel capacitor Cp, and an energy recovering device  50  connected to the panel capacitor Cp to apply an alternating current (AC) sustain pulse to the panel capacitor Cp.  
         [0205]    The panel capacitor Cp is an equivalent expression of a capacitance formed between a first electrode Y and a second electrode Z. In this case, any one of the first and second electrodes Y and Z is connected to the energy recovering device  50  while the remaining one thereof is connected to a ground voltage source GND. Hereinafter, it is assumed that the energy recovering device  50  should apply the AC sustain pulse to the first electrode Y.  
         [0206]    The energy recovering device  50  is arranged on a single of printed circuit board (not shown) to apply positive and negative AC sustain pulses to the first electrode Y. The energy recovering device  50  recovers a voltage between the first electrode Y and the second electrode Z to use the recovered voltage as a driving voltage upon the next discharge.  
         [0207]    To this end, the energy recovering device  50  includes first and second switches  9 S 1  and  9 S 2  connected in parallel to each other with having a first node  9 N 1  therebetween, a positive sustain pulse voltage part  52  connected to the first switch  9 S 1 , a negative sustain voltage part  54  connected to the second switch  9 S 2 , third and fourth switches  9 S 3  and  9 S 4  connected in parallel to each other with having a second node  9 N 2  connected to the panel capacitor Cp, an inductor L 1  connected between the second node  9 N 2  and the third node  9 N 3 , fifth and sixth switches  9 S 5  and  9 S 6  connected in parallel to each other with having a third node  9 N 3  therebetween, a first charging capacitor Ca connected between the third switch  9 S 3  and the fifth switch  9 S 5  to charge a positive sustain voltage, a second charging capacitor Cb connected between the fourth switch  9 S 4  and the fifth switch  9 S 5 , and a seventh switch  9 S 7  connected between the panel capacitor Cp and the ground voltage source GND.  
         [0208]    The first and second switches  9 S 1  and  9 S 2  are alternately switched to thereby switch a positive sustain voltage +Vs/2 and a negative sustain voltage −Vs/2 into the first and second capacitors Ca and Cb.  
         [0209]    The positive sustain voltage part  52  includes an ½ sustain voltage source Vs/2 connected between the first switch  9 S 1  and the ground voltage source GND, and a first energy-recovering capacitor Cs+ connected, in parallel, to the ½ sustain voltage source Vs/2 between the ½ sustain voltage source Vs/2 and the ground voltage source GND. The ½ sustain voltage source Vs/2 supplies a ½ sustain voltage Vs/2 to the panel capacitor Cp. The first energy-recovering capacitor Cs+ recovers and charges a voltage charged in the panel capacitor Cp upon the sustain discharge and re-applies the charged voltage to the panel capacitor Cp. At this time, a voltage +Vs/2 equal to a half of the ½ sustain voltage source Vs/2 is charged in the first energy-recovering capacitor Cs+.  
         [0210]    The negative sustain voltage part  54  includes a −½ sustain voltage source −Vs/2 connected between the second switch  9 S 2  and the ground voltage source GND, and a second energy-recovering capacitor Cs− connected, in parallel, to the −½ sustain voltage source −Vs/2 between the −½ sustain voltage source −Vs/2 and the ground voltage source GND. The −½ sustain voltage source −Vs/2 supplies a −½ sustain voltage −Vs/2 to the panel capacitor Cp. The second energy-recovering capacitor Cs− recovers and charges a voltage charged in the panel capacitor Cp upon the sustain discharge and re-applies the charged voltage to the panel capacitor Cp. At this time, a voltage −Vs/2 equal to a half of the −½ sustain voltage source −Vs/2 is charged in the second energy-recovering capacitor Cs−.  
         [0211]    The fifth switch  9 S 5  is connected between the fourth node  9 N 4  coupled with the first node  9 N 1  and the third node  9 N 3  to switch a voltage at the first node  9 N 1  into the first charging capacitor Ca. At this time, the first diode  9 D 1  is connected between the fifth switch  9 S 5  and the third node  9 N 3  while the second diode  9 D 2  is connected between the fifth switch  9 S 5  and the first charging capacitor Ca.  
         [0212]    The first charging capacitor Ca charges a positive voltage +Vs/2 at the first node  9 N 1  in response to a switching of the fifth switch  9 S 5 . The positive voltage +Vs/2 charged in the first charging capacitor Ca is added to a positive voltage Vs/2 charged in the first energy-recovering capacitor Cs+ to obtain a positive sustain voltage +Vs, and the positive sustain voltage +Vs is applied to the panel capacitor Cp. Meanwhile, the first and second diodes  9 D 1  and  9 D 2  play a role to form a current path only in a constant direction. Particularly, the second diode  9 D 2  plays a role to block the positive sustain voltage +Vs made by the first charging capacitor Ca in such a manner to make no effect to the first energy-recovering capacitor Cs+.  
         [0213]    The sixth switch  9 S 6  is connected between the fifth node  9 N 5  coupled with the first node  9 N 1  and the third node  9 N 3  to switch a voltage at the first node  9 N 1  into the second charging capacitor Cb. At this time, the third diode  9 D 3  is connected between the sixth switch  9 S 6  and the third node  9 N 3  while the fourth diode  9 D 4  is connected between the sixth switch  9 S 6  and the second charging capacitor Cb.  
         [0214]    The second charging capacitor Cb charges a negative voltage −Vs/2 at the first node  9 N 1  in response to a switching of the sixth switch  9 S 6 . The negative voltage −Vs/2 charged in the second charging capacitor Cb is added to a negative voltage −Vs/2 charged in the second energy-recovering capacitor Cs− to obtain a negative sustain voltage −Vs, and the negative sustain voltage −Vs is applied to the panel capacitor Cp. Meanwhile, the third and fourth diodes  9 D 3  and  9 D 4  play a role to form a current path only in a constant direction. Particularly, the fourth diode  9 D 4  plays a role to block the negative sustain voltage −Vs made by the second charging capacitor Cb in such a manner to make no effect to the second energy-recovering capacitor Cs−.  
         [0215]    The third switch  9 S 3  applies a positive sustain voltage +Vs charged in the first charging capacitor Ca to the panel capacitor Cp, thereby preventing the positive sustain voltage +Vs applied to the panel capacitor Cp from dropping into less than the sustain voltage Vs.  
         [0216]    The fourth switch  9 S 4  applies a negative sustain voltage −Vs charged in the second charging capacitor Cb to the panel capacitor Cp, thereby preventing the negative sustain voltage −Vs applied to the panel capacitor from rising into more than the sustain voltage −Vs. Herein the third and fourth switches  9 S 3  and  9 S 4  employ a field effect transistor (FET) having a resisting voltage of Vs.  
         [0217]    The inductor L 1  forms a resonance circuit along with the panel capacitor Cp. The seventh switch  9 S 7  connects the panel capacitor Cp to the ground voltage source GND in response to it&#39;s switching.  
         [0218]    [0218]FIG. 23 is a timing diagram and a waveform diagram representing ON/OFF timings of the switches shown in FIG. 22 and an output waveform of the panel capacitor, respectively.  
         [0219]    An operation of the sustain driving apparatus of the PDP according to the ninth embodiment of the present invention will be described in conjunction with FIG. 22 below.  
         [0220]    First, it is assumed that a voltage charged between the first electrode Y and the second electrode Z, that is, a voltage charged in the panel capacitor Cp before a T 1  interval should be 0 volt. Further, it is assumed that voltages Vs/2 and −Vs/2 should be charged in the first and second energy-recovering capacitors Cs+ and Cs− and the first and second charging capacitors Ca and Cb, respectively.  
         [0221]    In the T 1  interval, the first and fifth switches  9 S 1  and  9 S 5  are turned on while the second to fourth switches  9 S 2  to  9 S 4  and the sixth switch  9 S 6  are turned off. Further, the seventh switches  9 S 7  are turned off at an ON state. As the first switch  9 S 1  is turned on, a current path extending from the first energy-recovering capacitor Cs+, into the first switch  9 S 1 , the first node  9 N 1 , the fourth node  9 N 4 , the fifth switch  9 S 5 , the first diode  9 D 1 , the third node  9 N 3 , the inductor L 1 , the second node  9 N 2  and the panel capacitor Cp is formed. At this time, the inductor L 1 , the panel capacitor Cp and the first charging capacitor Ca form an LC serial resonance circuit.  
         [0222]    Since a positive voltage Vs/2 has been charged in the first energy-recovering capacitor Cs+ and the first charging capacitor Ca, a current charge/discharge of the inductor L in the LC serial resonance circuit raises a voltage of the panel capacitor Cp until a voltage Vs that is a sum of a voltage of the first energy-recovering capacitor Cs+ and a voltage of the first charging capacitor Ca. At this time, the third node  9 N 3  maintains the ½ sustain voltage Vs/2 by a turning-on of the fifth switch  9 S 5 . Further, a resonant pulse rises into more than the ½ sustain voltage Vs/2 with the aid of the LC serial resonance circuit, but is blocked by the first diode  9 D 1  to maintain the ½ sustain voltage Vs/2. Accordingly, the ½ sustain voltage Vs/2 at the second node  9 N 2  is added to the ½ sustain voltage Vs/2 previously charged in the sixth node  9 N 6  that is the (+) terminal of the first charging capacitor Ca, to thereby obtain a desired sustain voltage Vs.  
         [0223]    Since a voltage of the panel capacitor has risen until the positive sustain voltage +Vs in the T 1  interval, a driving power supplied from the exterior so as to cause the sustain discharge is minimized into Vs/2.  
         [0224]    In the T 2  interval, the third switch  9 S 3  is turned on; the first and fifth switches  9 S 1  and  9 S 5  keep an ON state; and the second, fourth, sixth and seventh switches  9 S 2 ,  9 S 4 ,  9 S 6  and  9 S 7  keep an OFF state. If the third switch  9 S 3  is turned on, then a boosted voltage +Vs made by an addition of a voltage from the positive sustain voltage source Vs/2 and a voltage of the first charging capacitor Ca is applied, via the sixth and second nodes  9 N 6  and  9 N 2 , to the panel capacitor Cp, thereby allowing the panel capacitor Cp to maintain the positive sustain voltage Vs. During the T 2  interval, the first capacitor Ca remains at the ½ sustain voltage Vs/2 by a voltage supplied via the fifth switch  9 S 5  because the fifth switch  9 S 5  has kept an ON state. To this end, a turning-off time of the fifth switch  9 S 5  becomes equal to that of the third switch  9 S 3 . The second diode  9 D 2  shuts off a current path such that a current of the first charging capacitor Ca does not flow through the positive sustain voltage source Vs/2.  
         [0225]    In a T 3  interval, the third and fifth switches  9 S 3  and  9 S 5  are turned off while the sixth switch  9 S 6  is turned on. Further, the first switch  9 S 1  keeps an ON state while the second, fourth and seventh switches  9 S 2 ,  9 S 4  and  9 S 7  keeps an OFF state. Accordingly, a current path extending from the panel capacitor Cp, via the inductor L 1 , the sixth switch  9 S 6  and the first switch  9 S 1 , into the first energy-recovering capacitor Cs+ is formed to recover the voltage charged in the panel capacitor Cp into the first energy-recovering capacitor Cs+, thereby allowing the panel capacitor Cp to drop into a ground level. In other words, the panel capacitor Cp is discharged, and a voltage component of a reactive power discharged from the panel capacitor Cp is recovered through the inductor L 1 , the third diode  9 D 3 , the sixth switch  9 S 6  and the first switch  9 S 1  and is charged in the first energy-recovering capacitor Cs+.  
         [0226]    Subsequently, in a T 4  interval, the first switch  9 S 1  is turned off while the seventh switch  9 S 7  is turned on. Further, the second to fifth switches  9 S 2  to  9 S 5  keep an OFF state while the sixth switch  9 S 6  keeps an ON state. At this time, the sixth switch  9 S 6  can be in an OFF state when the seventh switch  9 S 7  is in an ON state. Accordingly, if the seventh switch  9 S 7  is turned on, then a current path extending from the panel capacitor Cp into the ground voltage source GND is formed, thereby allowing a voltage of the panel capacitor Cp to be in a ground voltage state.  
         [0227]    Then, in a T 5  interval, the second and sixth switches  9 S 2  and  9 S 6  are turned on while the first, third to fifth switches  9 S 1 ,  9 S 3 ,  9 S 4  and  9 S 5  are turned off. Accordingly, the second switch  9 S 2  is turned on to thereby form a current path extending from the second energy-recovering capacitor Cs−, via the second switch  9 S 2 , the first node  9 N 1 , the fifth node  9 N 5 , the sixth switch  9 S 6 , the third diode  9 D 3 , the third node  9 N 3 , the inductor L 1  and the second node  9 N 2 , into the panel capacitor Cp. At this time, the inductor L 1 , the panel capacitor Cp and the second charging capacitor Cb forms an LC serial resonance circuit. Since a negative voltage −Vs/2 has been charged in the second energy-recovering capacitor Cs− and the second charging capacitor Cb, a voltage of the panel capacitor Cp is raised until a sum −Vs of a voltage of the second energy-recovering capacitor Cs− and a voltage of the second charging capacitor Cb by a current charge/discharge of the inductor L 1  in the LC serial resonance circuit. At this time, the third node  9 N 3  keeps a negative ½ sustain voltage −Vs/2 by a turning-on of the sixth switch  9 S 6 . Further, at the second node  9 N 2 , a resonant pulse rises into more than the negative ½ sustain voltage −Vs/2 by the LC serial resonance circuit, but is blocked by the third diode  9 D 3  to keep the negative ½ sustain voltage −Vs/2. Accordingly, the negative ½ sustain voltage −Vs/2 at the second node  9 N 2  is added to the negative ½ sustain voltage −Vs/2 previously charged in the seventh node  9 N 7  that is the (−) terminal of the second charging capacitor Cb to thereby obtain a desired negative sustain voltage −Vs.  
         [0228]    In a T 5  interval, since a voltage of the panel capacitor Cp has risen until the negative sustain voltage −Vs, a driving power supplied from the exterior so as to cause a sustain discharge is minimized into −Vs/2.  
         [0229]    In a T 6  interval, the fourth switch  9 S 4  is turned on; the second and sixth switches  9 S 2  and  9 S 6  keep an ON state; and the first, third, fifth and seventh switches  9 S 1 ,  9 S 3 ,  9 S 5  and  9 S 7  keep an OFF state. If the fourth switch  9 S 4  is turned on in this manner, then a boosted voltage −Vs made by an addition of a voltage from the negative sustain voltage source −Vs/2 and a voltage of the second charging capacitor Cb is applied, via the seventh and second nodes  9 N 7  and  9 N 2 , to the panel capacitor Cp to thereby maintain the negative sustain voltage −Vs. During the T 6  interval, since the second capacitor Cb has kept an ON state, it maintains the negative ½ sustain voltage −Vs/2 by a voltage supplied via the sixth switch  9 S 6 . To this end, a turning-off time of the sixth switch  9 S 6  becomes equal to that of the fourth switch  9 S 4 . The fourth diode  9 D 4  shuts off a current path such that a current of the second charging capacitor Cb does not flow through the negative sustain voltage source −Vs/2.  
         [0230]    In a T 7  interval, the fourth and sixth switches  9 S 4  and  9 S 6  are turned off while the fifth switch  9 S 5  is turned on. Further, the second switch  9 S 2  keeps an ON state while the first, third and seventh switches  9 S 1 ,  9 S 3  and  9 S 7  keep an OFF state. Accordingly, a current path extending from the panel capacitor Cp, via the inductor L 1 , the fifth switch  9 S 5  and the second switch  9 S 2 , into the second energy-recovering capacitor Cs− is formed to recover a voltage charged in the panel capacitor Cp into the second energy-recovering capacitor Cs−, thereby dropping the panel capacitor Cp into a ground level. In other words, the panel capacitor Cp is discharged, and a voltage component of a reactive power discharged from the panel capacitor Cp is recovered via the inductor L 1 , the first diode  9 D 1 , the fifth switch  9 S 5  and the second switch  9 S 2  and is charged into the second energy-recovering capacitor Cs−.  
         [0231]    Consequently, in a T 8  interval, the second and fifth switches  9 S 2  and  9 S 5  are turned off while the seventh switch  9 S 7  is turned on. Further, the first, third, fourth and sixth switches  9 S 1 ,  9 S 3 ,  9 S 4  and  0 S 6  keep an OFF state. Accordingly, if the seventh switch  9 S 7  is turned on, then a current path extending from the panel capacitor Cp into the ground voltage source GND is formed to thereby allow a voltage of the panel capacitor Cp to be in a ground voltage state.  
         [0232]    The sustain driving apparatus of the PDP according to the ninth embodiment of the present invention applies the AC sustain pulse, which is obtained with periodically repeating an operation procedure during the above-mentioned T 1  to T 8  interval, to the first electrode Y as shown in FIG. 24. Further, since the second electrode Z does not require a separate driving circuit, it is connected, via a heatproof panel (not shown) or a frame, only to the ground voltage source. Accordingly, the panel capacitor Cp is supplied with an AC driving pulse as shown in FIG. 24.  
         [0233]    The sustain driving apparatus of the PDP according to the ninth embodiment of the present invention simultaneously generates a positive sustain pulse and a negative sustain pulse using the positive ½ voltage source and the negative ½ voltage source provided on a single of printed circuit board, and applies the generated AC sustain pulse to any one of sustain electrode pairs and the reference voltage to the remaining one thereof. Accordingly, the sustain driving apparatus of the PDP according to the ninth embodiment of the present invention applies the AC sustain pulse only to any one of sustain electrode pairs, so that it becomes a configuration of the unified printed circuit board of one sustain driving apparatus. Furthermore, the driving apparatus of the PDP according to the ninth embodiment of the present invention reduces the sustain voltage Vs to ½ in comparison with the conventional sustain driving apparatus of the PDP to lower resisting voltages of switching devices from the twice sustain voltage 2Vs into the sustain voltage Vs, thereby configuring the switching devices by low-voltage switching devices to reduce a cost.  
         [0234]    As described above, in the sustain driving apparatus of the PDP according to the present invention, the charge capacitor is directly connected to the ½ sustain voltage to thereby apply an addition of the ½ sustain voltage and the charge capacitor voltage to the panel. Further, the charge path of the charge capacitor is driven separately from the charge/discharge path of the panel. Accordingly, the sustain driving apparatus of the PDP according to the present invention can lower the sustain voltage to ½ in comparison to the conventional sustain driving apparatus of the PDP to thereby reduce power consumption to that extent, and supplies a stable sustain voltage in the discharge sustain period using the boosted voltage to thereby stabilize a driving waveform.  
         [0235]    Furthermore, the sustain driving apparatus of the PDP according to the present invention simultaneously generates a positive sustain pulse and a negative sustain pulse using the positive ½ voltage source and the negative ½ voltage source provided on a single of printed circuit board, and applies the generated AC sustain pulse to any one of sustain electrode pairs and the reference voltage to the remaining one thereof. Accordingly, the sustain driving apparatus of the PDP according to the ninth embodiment of the present invention applies the AC sustain pulse only to any one of sustain electrode pairs, so that it becomes a configuration of the unified printed circuit board of one sustain driving apparatus. Furthermore, the driving apparatus of the PDP according to the ninth embodiment of the present invention reduces the sustain voltage Vs to ½ in comparison with the conventional sustain driving apparatus of the PDP to lower resisting voltages of switching devices from the twice sustain voltage 2Vs into the sustain voltage Vs, thereby configuring the switching devices by low-voltage switching devices to reduce a cost.  
         [0236]    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.