Patent Publication Number: US-7911420-B2

Title: Plasma display apparatus and method of driving the same

Description:
This non-provisional application claims priority under 35 U.S.C. §119(a) on Patent Application No. 10-2006-0119393 filed in Republic of Korea on Nov. 29, 2006 the entire contents of which are hereby incorporated by reference 
     BACKGROUND 
     1. Field 
     This document relates to a display apparatus, and more specifically, to a plasma display apparatus and a method of driving the same. 
     2. Related Art 
     A plasma display panel (“PDP”) apparatus comprises a PDP and a driver for driving the PDP. 
     The PDP comprises a front panel and a rear panel. Barrier ribs are formed on the rear panel to define unit discharge cells. An inert gas that contains a main discharge gas, such as Ne, He, or a mixture of Ne and He, and Xe is injected in each of the unit discharge cells. 
     When a high frequency voltage is applied to the unit discharge cells to create an electric discharge, vacuum ultra violet rays that are generated from the inert gas excite a phosphor formed between the barrier ribs. At this time, the excited phosphor emits light. 
     The PDP comprises a scan electrode Y, a sustain electrode Z, and a data electrode X. The driver is connected to the electrodes to apply voltages to the electrodes. 
     Meanwhile, driving efficiency can be lowered due to various factors when the voltages are applied from the driver to the electrodes. Accordingly, studies have been in progress to optimize driving conditions of the PDP apparatus. 
     SUMMARY 
     In one aspect, a plasma display apparatus comprises a plasma display panel comprising a first scan electrode, a second scan electrode, and a sustain electrode and a scan driver, wherein the scan driver supplies the first scan electrode with a first scan signal, supplies the first scan electrode and the second electrode with a first signal for emitting light, and then supplies the second scan electrode with a second scan signal that falls down from a scan reference voltage, and supplies the first scan electrode with a voltage that is different from the scan reference voltage while the second scan signal is supplied. 
     The sustain driver may supply the sustain electrode with a second signal for emitting light in the sustain electrode after the supply of the first signal and before the supply of the second scan signal. 
     The scan driver and the sustain driver may alternately supply the first signal and the second signal more than once and less than three times. 
     The plasma display apparatus may further comprise a sustain driver, and the sustain driver may supply the sustain electrode with a ground voltage while the scan driver supplies the first signal. 
     The plasma display apparatus may further comprise a sustain driver, and the sustain driver may supply the sustain electrode with a sustian signal after the supply of a sustain signal to the first scan electrode and the second scan electrode. 
     The scan driver may supply the second scan electrode with a signal that gradually falls down to a first voltage after the supply of the first signal. 
     The scan driver may supply the second scan electrode with a set-down signal that gradually falls down to a second voltage that is higher than the first voltage before supplying the first scan signal. 
     The voltage that may different from the scan reference voltage is a ground voltage. 
     The voltage that is different from the scan reference voltage may be a negative voltage. 
     When the negative voltage is supplied, a voltage that is lower than the sustain voltage may be supplied to the sustain electrode. 
     In another aspect, a method of a plasma display apparatus comprising a first scan electrode, a second scan electrode, and a sustain electrode, comprises supplying the first scan electrode with a first scan signal, supplying the second scan electrode with a second scan signal that falls down from a scan reference voltage after the supply of the first scan electrode and the second scan electrode with a first signal for emitting light and supplying the first scan electrode with a voltage that is different from the scan reference voltage while the second scan signal is supplied. 
     A second signal for emitting light in the sustain electrode may be supplied to the sustain electrode after the supply of the first signal and before the supply of the second scan signal. 
     The first signal and the second signal may be alternately supplied more than once and less than three times. 
     A ground voltage may be supplied to the sustain electrode while the first signal is supplied. 
     After the second scan signal was supplied, a sustain signal may be supplied to the first scan electrode and the second scan electrode, and a sustain signal may be supplied to the sustain electrode. 
     A signal that gradually falls down to a first voltage may be supplied to the second scan electrode after the first signal was supplied. 
     A set-down signal that gradually falls down to a second voltage that is higher than the first voltage may be supplied to the first scan electrode and the second scan electrode before the first scan signal is supplied. 
     The voltage that is different from the scan reference voltage may be a ground voltage. 
     The voltage that is different from the scan reference voltage may be a negative voltage. 
     When the negative voltage is supplied, a voltage that is lower than the sustain voltage may be supplied to the sustain electrode. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The implementation of this document will be described in detail with reference to the following drawings in which like numerals refer to like elements: 
         FIG. 1  is a view illustrating a PDP apparatus according to an exemplary embodiment of the present invention; 
         FIG. 2  is a view illustrating a PDP according to an exemplary embodiment of the present invention; 
         FIG. 3  is a view illustrating a method of driving a PDP apparatus according to an exemplary embodiment of the present invention; 
         FIGS. 4   a  and  4   b  are first waveforms of a PDP apparatus according to a first exemplary embodiment of the present invention; 
         FIG. 5  is a second waveform of a PDP apparatus according to a second exemplary embodiment of the present invention; 
         FIG. 6  is a third waveform of a PDP apparatus according to a third exemplary embodiment of the present invention; and 
         FIG. 7  is a fourth waveform of a PDP apparatus according to a fourth exemplary embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, an implementation of this document will be described in detail with reference to the attached drawings. 
     Referring to  FIG. 1 , a PDP apparatus comprise a PDP  200 , drivers, for example, a data driver  120 , a scan driver  130 , and a sustain driver  140 , for driving electrodes disposed on the PDP  200 , a controller for controlling the drivers, and a driving voltage generator  150  for generating driving voltages required for the drivers. 
     The driver  120  supplies data to data electrodes X 1  to Xm, the scan driver  130  drives scan electrodes Y 1  to Yn, and the sustain driver  140  drives sustain electrodes Z. 
     Referring to  FIG. 2 , the PDP  200  comprises a front panel  210  and a rear panel  220 . 
     The front panel  210  comprises a front substrate  211 , and a scan electrode  212  and a sustain electrode  213  are disposed on the front substrate  211 . The rear panel  220  comprises a rear substrate  221 , and a data electrode  223  that crosses the scan electrode  212  and the sustain electrode  221  is disposed on the rear substrate  221 . 
     The scan electrode  212 , Y may comprise a transparent electrode  212   a  formed of a transparent ITO material and a bus electrode  212   b  formed of a metal material. The sustain electrode  213  may comprise a transparent electrode  213   a  formed of a transparent ITO material and a bus electrode  213   b  formed of a metal material. The scan electrode  212  and the sustain electrode  213  may comprise the bus electrode  212   b  alone and the bus electrode  213   b  alone, respectively. 
     An upper dielectric layer  214  restricts discharge currents of the scan electrode  212  and the sustain electrode  213  and insulates the electrodes from each other. A protection layer  215  is disposed on the upper dielectric layer  204  by coating an MgO layer on the upper dielectric layer  204 . 
     A lower dielectric layer  225  covers the data electrode  223  to insulate one data electrode from another. A barrier rib  222  is formed in a stripe type or well type to define a discharge cell. A phosphor, for example, R phosphor, G phosphor, or G phosphor, is coated for emitting visible light between two barrier ribs  222  that are adjacent to each other. 
     In a PDP apparatus according to an exemplary embodiment of the present invention, one frame is divided into a plurality of sub-frames to drive the PDP apparatus, as shown in  FIG. 3 . Each subfield comprises a reset period for initializing all cells, an address period for selecting a cell to be discharged, and a sustain period for realizing a gray level according to the number of discharges. 
     For example, when an image is displayed with 256 gray levels, a frame period (e.g. 16.67 ms) that corresponds to 1/60 sec is divided into a plurality of sub-fields, for example, eight sub-fields SF 1  to SF 8 . As described above, each of the eight sub-fields SF 1  to SF 8  comprises a reset period RP, an address period AP, and a sustain period SP. The reset period RP and the address period AP are the same for each sub-field, while the sustain period SP and the number of sustain signals assigned during the sustain period SP may vary for each sub-field. As an example, the sub-field is increased in the ratio of 2n (n=0, 1, 2, 3, 4, 5, 6, and 7) to display gray levels. 
     The scan driver  130  supplies scan electrodes Y 1  to Yn with a reset signal during a reset period under control of the controller  110  to initialize the state of wall charges in all the discharge cells formed during the previous sub-field. The reset signal comprises a gradually rising set-up signal and a gradually falling set-down signal. 
     The scan driver  130  supplies the scan electrodes Y 1  to Yn with a scan signal (Scan) that falls down up to a scan voltage −Vs during an address period under control of the controller  110 . 
     The scan driver  130  supplies the scan electrodes Y 1  to Yn with a sustain signal that rises up to a sustain voltage Vs during a sustain period under control of the controller  110 . 
     A data signal is reverse-gamma corrected, error-diffused, and mapped to each sub-field by a reverse-gamma correction circuit (not shown), an error diffusion circuit (not shown), and a sub-field mapping circuit (not shown), respectively, and then the data signal is supplied to the data driver  120 . The data driver  120  samples and latches the data signal in response to a timing control signal CTRX of the controller  110 , and then supplies the sampled and latched data signal to the data electrodes X 1  to Xm. A cell to be turned on/off, for example, in which a sustain discharge is generated during a sustain period, is selected depending on the data signal. 
     The sustain driver  140  supplies a bias voltage to the sustain electrode Z during at least one of the set-down period and address period. In addition, the sustain driver  140  supplies the sustain electrode Z with a sustain signal that rises up to a sustain voltage Vs during the sustain period. 
     The controller  110  receives horizontal/vertical synchronization signals and a clock signal, generates timing control signals CRTX, CTRY, and CTRZ for controlling the operation timing and synchronization of each driver  120 ,  130 , and  140  during the reset period, address period, and sustain period, and supplies the timing control signals CTRX, CTRY, and CTRZ to a corresponding one of the drivers  120 ,  130 , and  140  in order to control the drivers  120 ,  130 , and  140 . 
     The data control signal CTRX includes a sampling clock signal for sampling data, a latch control signal, and a switch control signal for controlling on/off time of a sustain driving circuit and a driving switching element. The scan control signal CTRY comprises a switch control signal for controlling on/off time of a sustain driving circuit and a driving switching element in the scan driver  130 , and the sustain control signal CTRZ comprises a switch control signal for controlling on/off time of a sustain driving circuit and a driving switching element in the sustain driver  140 . 
     The driving voltage generator  150  generates driving voltages such as a set-up voltage Vsetup, a scan reference voltage Vsc, a scan voltage −Vy, a sustain voltage Vs, and a data voltage Va. The driving voltages may vary depending on the composition of the discharge gas or structure of the discharge cell. 
     Referring to  FIG. 4   a , one sub-field SF comprises a reset period RP, an address period AP, and a sustain period SP. 
     During a set-up period SU of the reset period RP, a set-up signal Su that rises up to the set-up voltage Vsetup is supplied to the first scan electrode Y 1  and the second scan electrode Y 2  by the scan driver  130  shown in  FIG. 1 . The first scan electrode Y 1  and the second scan electrode Y 2  may be located adjacent to each other, or not. A dark discharge is caused by the set-up signal Su in the entire discharge cells. 
     During a set-down period SD of the reset period RP, a set-down signal Sd that gradually falls down to a second voltage V 2  is simultaneously supplied to the first scan electrode Y 1  and the second scan electrode Y 2  by the scan driver  130  shown in  FIG. 1 . The set-down signal Sd causes an erase discharge in the discharge cell to remove wall discharges that are excessively generated by the set-up discharge and make the wall discharges distributed uniformly. 
     The scan driver  130  supplies a first scan signal Scan 1  to the first scan electrode Y 1 , supplies the first scan electrode Y 1  and the second scan electrode Y 2  with a first signal S 1  for emitting light, and then supplies a scan signal Scan 2  to the second scan electrode Y 2 . The first signal S 1  rises from a ground voltage to the sustain voltage Vs. 
     When a data signal (data) is supplied to the data electrode X in synchronization with the first scan signal Scan 1 , address discharges occur in the discharge cells that correspond to the first scan electrode Y 1 . Accordingly, when the first signal S 1  that rises up to the sustain voltage Vs is supplied, light is emitted in the discharge cells where the address discharges are generated. 
     After the first signal S 1  was supplied, the scan driver  130  supplies the first scan electrode Y 1  and the second scan electrode Y 2  with a sustain signal Ys 2  that rises up to the sustain voltage V 2  during the sustain period SP. 
     The scan driver  130  supplies the scan reference voltage Vsc to the second scan electrode Y 2  while the first scan signal Scan 1  is supplied to the first scan electrode Y 1 . 
     The sustain driver  140  supplies the bias voltage Vzb to the sustain electrode Z while the first scan signal Scan 1  is supplied to the first scan electrode Y 1 . The bias voltage Vzb decreases the number of discharges that occur between the first scan electrode Y 1  and the sustain electrode Z during the address period AP. 
     The sustain driver  140  may supply the sustain electrode Z with the second signal S 2  after the scan driver  130  supplies the first signal S 1  with the first scan electrode Y 1  and before the second scan signal Scan 2  is supplied to the second scan electrode Y 2 . Accordingly, the discharge cells that correspond to the first scan electrode Y 1  emits light again. 
     Referring to  FIG. 4   b , the first signal S 1  and the second signal S 2  may be alternately supplied more than one time and less than three times to the first and second scan electrodes Y 1  and Y 2  and the sustain electrode Z by the scan driver  130  and the sustain driver  140 . 
     As shown in  FIGS. 4   a  and  4   b , the scan driver  130  supplies the second scan signal Scan 2  to the second scan electrode Y 2  after having supplied the first signal S 1  to the first scan electrode Y 1  and second scan electrode Y 2 . The scan driver  130  may supply the first scan electrode Y 1  with some voltage Vn that is different from the scan reference voltage Vsc, while the second scan signal Scan 2  is supplied to the second scan electrode Y 2 . The voltage Vn may be a ground voltage. 
     The data driver  120  supplies the data electrode X with a data signal (data) that synchronizes with the second scan signal Scan 2 , while the second scan signal Scan 2  is supplied to the second scan electrode Y 2 . Accordingly, address discharges occur in the discharge cells that correspond to the second scan electrode Scan 2 . 
     The sustain driver  140  supplies the bias voltage Vzb to the sustain electrode Z while the second scan signal Scan 2  is supplied. The bias voltage Vzb may be substantially identical to the sustain voltage. 
     After the address period AP, the sustain signal Ys 2  and a sustain signal Zs 2  that rise up to the sustain voltage Vs are alternately supplied to the first and second scan electrodes Y 1  and Y 2 , and the sustain electrode Z by the scan driver  130  and the sustain driver  140 . 
     When the first scan signal Scan 1  is supplied to the first scan electrode Y 1  before the second scan signal Scan 2  is supplied to the second scan electrode Y 2 , the loss of wall charges and priming particles after the supplying of the first scan signal Scan 1  further increases in the first scan electrode Y 1  than in the second scan electrode Y 2 . Therefore, if the first signal S 1  is supplied between when the first scan signal Scan 1  is supplied and when the second scan signal Scan 2  is supplied, the loss of wall charges and priming particles in the first scan electrode Y 1  could be compensated. Accordingly, the sustain discharges can occur stably in the discharge cells supplied with the first and second scan signals Scan 1  and Scan 2 . 
     When the first scan signal Scan 1  is supplied to the first scan electrode Y 1  before the second scan signal Scan 2  is supplied to the second scan electrode Y 2 , the loss of wall charges caused during the reset period RP before the supplying of the first scan signal Scan 2  further increases in the second scan electrode Y 2  than in the first scan electrode Y 1 . As such, the first signal S 1  is supplied to the second scan electrode Y 2  before the second scan signal Scan 2  is supplied, and therefore, the loss of wall charges caused in the second scan electrode Y 2  can be compensated. 
     Referring to  FIG. 5 , when the scan driver  130  supplies the first signal S 1  to the first scan electrode Y 1  and the second scan electrode Y 2  during the address period AP, the sustain driver  140  may supply the sustain electrode Z with a ground voltage GND. The driving waveforms of signals during the reset period RP in  FIG. 5  are similar to those in  FIGS. 4   a  and  4   b , and therefore, their detailed descriptions will be omitted. 
     When the first scan signal Scan 1  and data signal (data) are supplied, address discharges occur in the discharge cells that correspond to the first scan electrode Y 1  but does not occur in the discharge cells that correspond to the second scan electrode Y 2 . 
     After the first scan signal Scan 1  has been supplied to the first scan electrode Y 1  and before the second scan signal Scan 2  is supplied to the second scan electrode Y 2 , the first signal S 1  is supplied to the first scan electrode Y 1  and the second scan electrode Y 2 , and the second signal S 2  is not supplied to the sustain electrode Z. Therefore, sustain discharges occur in only the discharge cells that correspond to the first scan electrode Y 1  and caused the address discharges but not in the discharge cells that correspond to the second scan electrode Y 2 . 
     After the first signal S 1  was supplied to the first scan electrode Y 1  and the second scan electrode Y 2 , the second scan signal Scan 2  is supplied to the second scan electrode Y 2 . 
     And then, sustain signals Ysf 2  and Ys 2 , and Zsf 1  and Zs 2  are alternately supplied to the first and second scan electrodes Y 1  and Y 2 , and the sustain electrode Z, respectively. 
     During the address period AP, the first signal S 1  is supplied only to the first scan electrode Y 1  and the second scan electrode Y 2  and the sustain discharges occur only in the discharge cells that correspond to the first scan electrode Y 1 , and therefore, the sustain discharges do not occur in the discharge cells that correspond to the first scan electrode Y 1  by the sustain signal Ysf 2  that is firstly supplied to the first scan electrode Y 1 . 
     In addition, since sustain discharges did not occur in the discharge cells that correspond to the second scan electrode Y 2 , sustain discharges can be generated in the discharge cells that correspond to the second scan electrode Y 2  by the first sustain signal Ysf 2  which is applied to the second scan electrode Y 2 . 
     Accordingly, since a single sustain discharge occurs in the discharge cells corresponding to the first scan electrode Y 1  and the second scan electrode Y 2  for the address period and a part of the sustain period during which the first sustain signal Ysf 2  is supplied, variations in brightness of the light emitting from the discharge cells that correspond to the first and second scan electrodes Y 1  and Y 2  do not occur. 
     Accordingly, the driving waveforms shown in  FIG. 5  can compensate the loss of wall charges and priming particles as well as reduce the variations in brightness. 
     The driving waveforms of signals during the set-up period SU in  FIG. 6  are similar to those in  FIGS. 4   a  and  4   b , and therefore, their detailed descriptions will be omitted. 
     During a set-down period SD, the scan driver  130  supplies the first scan electrode Y 1  with the first set-down signal Sd 1  that falls down to the third voltage V 3 , and supplies the second scan electrode Y 2  with the second set-down signal Sd 2  that falls down to the second voltage V 2  which is higher than the third voltage V 2 . 
     The scan driver  130  supplies the first scan electrode Y 1  with the first scan signal Scan 1 , supplies the second scan electrode Scan 2  with the scan reference voltage Vsc, and supplies the first signal S 1  to the first scan electrode Y 1  and the second scan electrode Y 2 . 
     After having supplied the first signal S 1  to the second scan electrode Y 2 , the scan driver  130  supplies the second scan electrode Y 2  with a signal Sf that gradually falls from the ground voltage to the first voltage V 1  which is lower than the second voltage V 2 . At this time, the first voltage V 1  may be substantially equal to the third voltage V 3 . 
     That is, the scan driver  130  supplies the second scan electrode Y 2  with the second set-down signal Sd 2  that gradually falls down to the second voltage V 2  which is higher than the first voltage V 1 . The signal Sf that is supplied to the second scan electrode Y 2  causes a weak erase discharge in the discharge cells corresponding to the second scan electrode Y 2 . The wall charges that are formed in the discharge cells corresponding to the second scan electrode Y 2  are partially removed by the set-up discharges occurring during the set-up period SU. 
     In other words, the amount of wall charges to be removed by the first set-down signal Sd 1  is larger than the amount of wall charges to be removed by the second set-down signal Sd 2 . Since the wall charges of the second scan electrode Y 2  is removed by the signal Sf, the amount of wall charges formed in the first and second scan electrodes Y 1  and Y 2  may be controlled. That is, the amount of wall charges may be controlled in the first and second scan electrodes Y 1  and Y 2  by adjusting the levels of the first to the third voltages V 1 , V 2 , and V 3 . 
     During the address period, the ground voltage GND is supplied to the sustain electrode Z while the sustain voltage Vs is supplied to the first scan electrode Y 1  and the second scan electrode Y 2 , and therefore, variations in brightness can be reduced as described above with reference to  FIG. 5 . 
     In addition to the compensation to loss of wall charges and decrease in brightness variation, the amount of wall charges can be adjusted to be suitable for the characteristics of various PDPs. 
     The driving waveforms of signals during the set-up period SU in  FIG. 7  are similar to those in  FIGS. 4   a  and  4   b , and therefore, their detailed descriptions will be omitted. 
     The driving waveforms of signals shown in  FIG. 5  are different from those shown in  FIG. 7 , in that the first scan reference voltage −Vsc 1  that is supplied to the first scan electrode Y 1  after the first signal S 1  and second signal S 2  have been supplied to the first scan electrode Y 1  and the second scan electrode Y 2  is a negative voltage, and the level of the first scan reference voltage −Vsc is dissimilar to that of the second scan reference voltage −Vsc 2 . Accordingly, the driving waveforms of signals shown in  FIG. 7  can adjust variations in address discharge of the discharge cells that correspond to the first and second scan electrodes Y 1  and Y 2 , which can be caused when the scan signals have the different supplying order. 
     The bias voltage Vzb that is supplied to the sustain electrode Z when the first and second scan signals Scan 1  and Scan 2  are supplied may be lower than the sustain voltage Vs. When the bias voltage Vzb equal to the sustain voltage Vs is supplied after the supplying of the first signal S 1  and the second signal S 2 , there can occur sustain discharges, and therefore, the contrast of the PDP can be deteriorated. Accordingly, it can be possible to prevent the deterioration of the contrast of the PDP by supplying the bias voltage Vzb that is lower than the sustain voltage Vs. 
     The foregoing embodiments and advantages are merely exemplary and are not to be construed as limiting the present invention. The present teaching can be readily applied to other types of apparatuses. The description of the foregoing embodiments is intended to be illustrative, and not to limit the scope of the claims. Many alternatives, modifications, and variations will be apparent to those skilled in the art. In the claims, means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents but also equivalent structures. Moreover, unless the term “means” is explicitly recited in a limitation of the claims, such limitation is not intended to be interpreted under 35 USC 112(6).