Patent Publication Number: US-7710352-B2

Title: Plasma display panel comprising energy recovery circuit and driving method thereof

Description:
This Non-provisional application claims priority under 35 U.S.C. § 119(a) on Patent Application No. 10-2005-0007755 filed in Korea on Jan. 27, 2005, the entire contents of which are hereby incorporated by reference. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a plasma display panel comprising an energy recovery circuit and a driving method thereof, and more particularly, to a plasma display panel capable of removing a peak voltage of a scan electrode and a driving method thereof. 
   2. Description of the Background Art 
   In a general plasma display panel, ultraviolet rays of 147 nm emitted by discharging a He—Xe gas mixture or a Ne—Xe gas mixture excite phosphors. Images of characters or graphics are displayed on the plasma display panel by the excited phosphors. 
     FIG. 1  shows a structure of a related art plasma display panel. 
   As shown in  FIG. 1 , a plasma display panel  30  comprises a scan electrode  12 A and a sustain electrode  12 B formed on a front substrate  10  and a data electrode  20  formed on a rear substrate  18 . 
   The scan electrode  12 A and the sustain electrode  12 B each comprise a transparent electrode and a bus electrode. The transparent electrode is formed of indium-tin-oxide (ITO) and the bus electrode is formed of a metal capable of reducing a resistance of the transparent electrode. 
   An upper dielectric layer  14  and a protective layer  16  are stacked on the front substrate  10  on which the scan electrode  12 A and the sustain electrode  12 B are formed. 
   Wall charges generated by a plasma discharge of the plasma display panel  30  are accumulated on the upper dielectric layer  14 . The protective layer  16  prevents a damage of the upper dielectric layer  14  caused by sputtering generated by the plasma discharge, and also increases a secondary electron emission coefficient. The protective layer  16  is generally formed of MgO. 
   A lower dielectric layer  22  and a barrier rib  24  are formed on the rear substrate  18  on which the data electrode  20  is formed. A phosphor layer  26  is coated on the surfaces of the lower dielectric layer  22  and the barrier rib  24 . 
   The data electrode  20  is formed to intersect the scan electrode  12 A and the sustain electrode  12 B. The barrier rib  24  is formed in parallel with the data electrode  20 . The barrier rib  24  prevents the ultraviolet rays and visible light emitted by the plasma discharge from being radiated to adjacent discharge cells. 
   The ultraviolet rays generated by the plasma discharge excite the phosphor layer  26  to generate any one of red, green or blue light. A He—Xe gas mixture or a Ne—Xe gas mixture is injected into a discharge space of the discharge cell between the front and rear substrates  10  and  18  and the barrier rib  24 . 
     FIG. 2  shows a driving waveform of a related art plasma display panel. 
   As shown in  FIG. 2 , the related art plasma display panel is driven by dividing each of a plurality of subfields into a reset period for initializing the whole screen, an address period for selecting cells to be discharged, a sustain period for maintaining discharges of the selected cells, and an erase period for erasing wall charges in the discharged cells. 
   In the reset period, a rising pulse Ramp-up is simultaneously applied to all scan electrodes Y during a set-up period SU to generate a dark discharge within discharge cells of the whole screen. By the discharge performed during the set-up period SU, positive wall charges are accumulated on address electrodes X and sustain electrodes Z, while negative wall charges are accumulated on the scan electrodes Y. 
   A falling pulse Ramp-down is applied to the discharge cells during a set-down period SD. The falling pulse Ramp-down which falls from a positive voltage less than a peak voltage of the rising pulse Ramp-up to a ground voltage or a certain negative voltage partially removes wall charges excessively formed in the cells. As a result, wall charges required for performing a stable address discharge uniformly remains in the cells. 
   In the address period, a scan pulse Sp is sequentially applied to the scan electrodes Y and at the same time, a data pulse Dp is applied to the address electrodes X in synchronous with the scan pulse Sp. A data voltage Vd of the data pulse Dp is commonly 65 V. 
   While the voltage difference between the scan pulse Sp and the data pulse Dp is added to the wall charges produced during the reset period, the address discharge is generated within the discharge cells to which the data pulse Dp is applied. Wall charges required for a sustain discharge generated by supplying a sustain voltage Vs are formed within the cells selected by the address discharge. 
   A bias voltage Zdc is supplied to the sustain electrodes Z during the set-down period SD and the address period to decrease the voltage difference between the sustain electrodes Z and the scan electrodes Y. Accordingly, the supply of the bias voltage Zdc prevents misdischarge between the sustain electrodes Z and the scan electrodes Y. 
   In the sustain period, a sustain pulse SUSp is alternately applied to the scan electrodes Y and the sustain electrodes Z. While the wall voltages within the cells selected by the address discharge are added to the sustain pulse SUSp, a sustain discharge, that is, a display discharge is generated between the scan electrodes Y and the sustain electrodes Z whenever the sustain pulse SUSp is applied. 
   In the erase period, after completing the sustain discharge, an erase pulse Ramp-ers having a narrow pulse width and a low voltage is supplied to the sustain electrodes Z to remove the wall charges remaining in the cells of the whole screen. 
     FIG. 3  is a related art energy recovery circuit diagram of the plasma display panel. 
   As shown in  FIG. 3 , when the plasma display panel is driven according to the driving waveform of  FIG. 2 , the sustain pulse SUSp is formed by an energy recovery circuit. When the plasma display panel is normally driven, charges corresponding to 0.5 Vs are charged to a capacitor C of the energy recovery circuit. When a first switch Q 1  is turned on in a charged state of the capacitor C, a voltage of the scan electrode Y rises up to a sustain voltage Vs by LC resonance between the plasma display panel and an inductor L. When a second switch Q 2  is turned on, a voltage of the scan electrode Y is maintained with the sustain voltage Vs. When a third switch Q 3  is turned on, a voltage of the scan electrode Y falls to a ground voltage GND by LC resonance between the plasma display panel and the inductor L. Afterwards, when a fourth switch Q 4  is turned on, a voltage of the scan electrode Y is maintained with the ground voltage GND. 
     FIG. 4  shows a voltage waveform of the scan electrode shown according to an operation of the energy recovery circuit of  FIG. 3  when initially driving the plasma display panel. 
   As shown in  FIG. 4 , when the plasma display panel is initially driven by the supply of a power supply, charges corresponding to 0.5 Vs are not charged to the capacitor C of the energy recovery circuit. Afterwards, the charges corresponding to 0.5 Vs are charged to the capacitor C by continuously performing turn-on and turn-off operations of the first to fourth switches Q 1  to Q 4  in order. 
   In a period indicated by a reference numeral {circle around ( 1 )} of  FIG. 4 , when the first switch Q 1  is turned on in a state that the charges corresponding to 0.5 Vs are not charged to the capacitor C, a voltage of the scan electrode Y rises up to a voltage less than the sustain voltage Vs. 
   Next, in a period indicated by a reference numeral {circle around ( 2 )} of  FIG. 4 , when the second switch Q 2  is turned on, the sustain voltage Vs is applied to the scan electrode Y. Here, since the voltage difference between the sustain voltage and the voltage of the scan electrode Y is large, a large current flows to the energy recovery circuit. As a result, a peak voltage of the scan electrode Y is generated. When the peak voltage generated in the scan electrode Y is larger than a breakdown voltage of the switches or diodes constituting the energy recovery circuit, problems in normal operations of the switches or the diodes are generated. 
   SUMMARY OF THE INVENTION 
   Accordingly, an object of the present invention is to solve at least the problems and disadvantages of the related art. 
   The present invention provides a plasma display panel capable of removing a peak voltage generated in a scan electrode by more rapidly charging a capacitor of an energy recovery circuit when initially driving a plasma display panel, and a driving method thereof. 
   According to an aspect of the present invention, there is provided a plasma display panel comprising an energy charging part for supplying a predetermined voltage, an energy supply and recovery part for receiving an energy of the predetermined voltage from the energy charging part, and a pulse forming part for supplying the energy of the predetermined voltage supplied from the energy supply and recovery part to the plasma display panel, for maintaining a sustain voltage of the plasma display panel and for recovering the energy of the predetermined voltage to the energy supply and recovery part. 
   It is preferable that the predetermined voltage equals a voltage corresponding to a voltage of a data pulse. 
   It is preferable that an address voltage supply part generates the predetermined voltage. 
   It is preferable that when initially driving the plasma display panel, a voltage of a scan electrode increases substantially to two times the predetermined voltage. 
   It is preferable that the energy charging part comprises a diode for preventing an inverse current. 
   It is preferable that the energy charging part comprises a resistor which is connected in series between the diode and an energy charging power supply source. 
   It is preferable that the energy supply and recovery part comprises a capacitor. 
   According to another aspect of the present invention, there is provided a method of driving a plasma display panel comprising supplying a predetermined voltage to an energy supply and recovery part, supplying an energy of the predetermined voltage charged to the energy supply and recovery part to the plasma display panel, maintaining a sustain voltage of the plasma display panel, and recovering the energy of the predetermined voltage to the energy supply and recovery part. 
   It is preferable that the predetermined voltage equals a voltage corresponding to a voltage of a data pulse. 
   It is preferable that an address voltage supply part generates the predetermined voltage. 
   It is preferable that a voltage of a scan electrode increases substantially to two times the predetermined voltage when initially driving the plasma display panel. 
   It is preferable that the predetermined voltage is supplied through a diode for preventing an inverse current. 
   It is preferable that the predetermined voltage is supplied through a resistor which is connected in series between the diode and an energy charging power supply source. 
   It is preferable that the energy supply and recovery part comprises a capacitor. 
   According to still another aspect of the present invention, there is provided a plasma display panel comprising an address voltage supply part for supplying an address voltage, an energy supply and recovery part for receiving an energy of the address voltage from the address voltage supply part, and a pulse forming part for supplying the energy of the address voltage supplied from the energy supply and recovery part to the plasma display panel, for maintaining a sustain voltage of the plasma display panel, and for recovering the energy of the address voltage to the energy supply and recovery part. 
   It is preferable that the address voltage equals a voltage corresponding to a voltage of a data pulse. 
   It is preferable that when initially driving the plasma display panel, a voltage of a scan electrode increases substantially to two times the address voltage. 
   It is preferable that the address voltage supply part comprises a diode for preventing an inverse current. 
   It is preferable that the address voltage supply part comprises a resistor which is connected in series between the diode and an address voltage supply source. 
   It is preferable that the energy supply and recovery part comprises a capacitor. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompany drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention. In the drawings: 
       FIG. 1  shows a structure of a related art plasma display panel; 
       FIG. 2  shows a driving waveform of a related art plasma display panel; 
       FIG. 3  shows a related art energy recovery circuit diagram of the plasma display panel; 
       FIG. 4  shows a voltage waveform of the scan electrode showing according to an operation of the energy recovery circuit of  FIG. 3  when initially driving the plasma display panel; 
       FIG. 5  shows an energy recovery circuit diagram of a plasma display panel according to an embodiment of the present invention; 
       FIG. 6  shows a switch timing chart of the energy recovery circuit of  FIG. 5  and a voltage of a scan electrode according to the switch timing; and 
       FIG. 7  is a flow chart showing a driving method of the plasma display panel according to the embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
   Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings. 
   Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the attached drawings. 
     FIG. 5  shows an energy recovery circuit diagram of a plasma display panel according to an embodiment of the present invention. 
   As shown in  FIG. 5 , an energy recovery circuit diagram of a plasma display panel according to an embodiment of the present invention comprises an energy charging part  510 , an energy supply and recovery part  520  and a pulse forming part  530 . 
   When the plasma display panel is initially driven by the supply of a power supply, the energy charging part  510  supplies a predetermined voltage supplied from an energy charge power supply source Vsource to the energy supply and recovery part  520 . The predetermined voltage may equal a voltage Va corresponding to a voltage of a data pulse. 
   Since a sustain voltage Vs ranges from 180V to 200 V and the voltage Va of the data pulse ranges from 60V to 65 V, an address voltage supply part can be used as a voltage supply source for supplying the closest voltage to a voltage of 0.5 Vs. Since the predetermined voltage supplied from the energy charging part  510  equals the voltage Va corresponding to the voltage of the data pulse, it is unnecessary to add a separate power supply source. 
   When the plasma display panel is initially driven, the energy charging part  510  supplies an energy of the predetermined voltage to the energy supply and recovery part  520 . 
   The pulse forming part  530  supplies the energy of the predetermined voltage supplied from the energy supply and recovery part  520  to the plasma display panel through resonance between an inductor L and the plasma display panel. A voltage of the panel is maintained with the sustain voltage Vs. Then, the energy of the supplied predetermined voltage is recovered to the energy supply and recovery part  520  through the resonance between the inductor L and the panel. 
   When a voltage of the energy supply and recovery part  520  is more than the predetermined voltage, a reverse-blocking diode Dc included in the energy charging part  510  prevents an inverse current. A cathode end of the reverse-blocking diode Dc is connected to the energy supply and recovery part  520  and an anode end is connected to the energy charge power supply source Vsource. A resistor R may be connected between the energy charge power supply source Vsource and the reverse-blocking diode Dc. The resistor R prevents a rapid increase in a voltage. 
   When the plasma display panel is initially driven, a voltage of a scan electrode Y (refer to  FIG. 6 ) increases substantially to two times the predetermined voltage. The energy supply and recovery part  520  comprises a capacitor. 
     FIG. 6  shows a switch timing chart of the energy recovery circuit of  FIG. 5  and a voltage of a scan electrode according to the switch timing. 
   As shown in  FIG. 6 , when the power supply is supplied to the plasma display panel, the sustain voltage Vs and the voltage Va of the data pulse are supplied in a period indicated by a reference numeral ⊚ of  FIG. 6 . As a result, the energy charge power supply source Vsource supplies the predetermined voltage (corresponding to the voltage Va of the data pulse) to the capacitor C of the energy supply and recovery part  520 . Then, the energy supply and recovery part  520  is charged to an energy of the predetermined voltage (Va). 
   In a period indicated by a reference numeral {circle around ( 1 )} of  FIG. 6 , when the first switch Q 1  is turned on, the energy of the predetermined voltage supplied to the energy supply and recovery part  520  is supplied to the plasma display panel. Moreover, a voltage of the scan electrode Y increases to two times the predetermined voltage (=2Va) by the resonance between the inductor L and the panel. 
   Next, in a period indicated by a reference numeral {circle around ( 2 )} of  FIG. 6 , when the second switch Q 2  is turned on, the voltage of the scan electrode Y increases to the sustain voltage Vs. Since the voltage of the scan electrode Y increases from the voltage of 2Va to the sustain voltage Vs, a change in the voltages of the scan electrode Y is less than a change in the voltages of the scan electrode Y in the related art energy recovery circuit. 
   In the energy recovery circuit according to the embodiment of the present invention, when the plasma display panel is initially driven, a voltage of the capacitor C of the energy supply and recovery part  520  is Va in the period ⊚ and the voltage of the scan electrode Y is 2Va in the period {circle around ( 1 )}. In other words, since, a change in the voltages of the scan electrode Y is relatively small in the period {circle around ( 2 )}, the peak voltage of the scan electrode Y is low. 
   Since the likelihood of an abnormal operation of the switches or the diode decreases due to the low peak voltage of the scan electrode Y, the reliability of the energy recovery circuit increases. 
   Next, when a third switch Q 3  is turned on in the period {circle around ( 3 )}, the energy of the predetermined voltage supplied to the plasma display panel is recovered to the energy supply and recovery part  520  by the resonance between the inductor L and the panel. Moreover, the voltage of the scan electrode Y falls to the ground voltage. 
   When a fourth switch Q 4  is turned on in a period {circle around ( 4 )}, the voltage of the scan electrode Y is maintained with the ground voltage. 
   Accordingly, since when the plasma display panel is initially driven, the capacitor of the energy recovery circuit is charged more rapidly to remove the peak voltage of the scan electrode Y, the plasma display panel can be driven stably. 
     FIG. 7  is a flow chart showing a driving method of the plasma display panel according to the embodiment of the present invention. 
   As shown in  FIG. 7 , the energy charging part  510  supplies the predetermined voltage supplied from the energy charge power supply source Vsource to the energy supply and recovery part  520  in S 710 . The predetermined voltage may equal the voltage Va corresponding to the voltage of the data pulse. An address voltage supply part may be used as a power supply source of the voltage Va. 
   The pulse forming part  530  supplies an energy of the predetermined voltage supplied from the energy supply and recovery part  520  to the plasma display panel through resonance between an inductor L and the panel in S 720 . A voltage of the panel is maintained with the sustain voltage Vs in S 730 . Then, the energy of the supplied predetermined voltage is recovered to the energy supply and recovery part  520  through the resonance between the inductor L and the panel in S 740 . 
   When the voltage of the energy supply and recovery part  520  is more than the predetermined voltage, the reverse-blocking diode Dc included in the energy charging part  510  prevents an inverse current. The cathode end of the reverse-blocking diode Dc is connected to the energy supply and recovery part  520  and the anode end is connected to the energy charge power supply source Vsource. The resistor R may be connected between the energy charge power supply source Vsource and the reverse-blocking diode Dc. 
   When the plasma display panel is initially driven, the voltage of the scan electrode Y increases substantially to two times the predetermined voltage. The energy supply and recovery part  520  comprises the capacitor. 
   As described above, since when a plasma display panel according to the embodiment of the present invention is initially driven, an energy charging part supplies a predetermined voltage to an energy supply and recovery part, a peak voltage of a scan electrode can be removed. Moreover, abnormal operations of switches or diodes of an energy recovery circuit can be prevented. As a result, reliability of the energy recovery circuit increases. 
   It will be apparent to those skilled in the art that various modifications and variation can be made in the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.