Abstract:
Provided are a method and apparatus for driving an electro-luminescence (EL) display panel having data electrode lines and scanning electrode lines intersecting each other at a predetermined distance and EL cells, formed at the intersections thereof. In the method and apparatus, a booting current corresponding to a magnitude change of a display data signal in the next horizontal drive time period with respect to a display data signal in the current horizontal drive time period is applied to each of the data electrode lines at the beginning of the next horizontal drive time period. Instantaneous values of the booting currents are kept constant, and the application time for the booting current is proportional to a magnitude change of each display data signal in the next horizontal drive time period with respect to the display data signal in the current horizontal drive time period.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the priority of Korean Patent Application No. 2003-23713, filed on Apr. 15, 2003, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference in its entirety. 
     FIELD OF THE INVENTION  
     The present invention relates to a method and apparatus for driving an electro-luminescence (EL) display panel, and more particularly, to a method and apparatus for driving an EL display panel having electro-luminescence cells formed at intersections between data and scanning electrode lines crossing each other at a predetermined distance. 
     BACKGROUND OF THE INVENTION  
     Referring to  FIG. 1 , a conventional EL display device includes an EL display panel  2  and a driving circuit. The driving circuit comprises a controller  21 , a scanning driving unit  6 , and a data driving unit  5 . The EL display panel  2  has a plurality of data electrode lines  3  and scanning electrode lines  4  intersecting each other at a predetermined distance. The EL display panel  2  further has electro-luminescence cells  1 , each being formed at the intersections between the data electrode lines  3  and the scanning electrode lines  4 . 
     The controller  21  receives and processes image signals S IM . The processing includes applying data control signals S DA  and scanning control signals S SC  to the data driving unit  5  and the scanning driving unit  6 , respectively. The data control signals S DA  include the display data signals and the switching control signals, while the scanning control signals S SC  are the switching control signals. 
     The data driving unit  5  connected to the signal-input terminals of the data electrode lines  3  produces data current signals, corresponding to the display data signals from the controller  21  in response to the switching control signals received from the controller  21 , and applies the data current signals to the data electrode lines  3 . Here, reference number  8  denotes current sources. 
     The scanning driving unit  6  connected to the signal-input terminals of the scanning electrode lines  4  sequentially applies scanning driving signals, in response to the switching control signals received from the controller  21 , to the scanning electrode lines  4 . 
     Referring to  FIG. 1  and  FIG. 2 , the data driving unit  5  of the EL display device of  FIG. 1  includes an interface  30 , a latch circuit  31 , digital-to-analog (D/A) converters  32 , and an output circuit  33 . 
     The latch circuit  31 , operating according to a horizontal synchronization signal H SYNC  received from the controller  21  through the interface  30 , periodically stores the display data signals D DA  received from the controller  21  through the interface  30  while periodically outputting display data signals in the current and next horizontal drive time periods, respectively. Each of the D/A converters  32  converts each of the display data signals in the current horizontal drive time period received from the latch circuit  31  into a data current signal. The output circuit  33  then applies data output signals I D1 -I Dm , corresponding to the display data signals received from the D/A converters  32 , to the corresponding data electrode lines  3 , respectively. 
     As an example of a conventional EL display device configured as above, U.S. Pat. No. 6,531,827 discloses a technology for improving driving speed by applying booting current at the beginning of each horizontal drive time period. European Laid-open Patent Publication No. 1,091,340 proposes a technology for reducing power consumption by controlling the booting current according to a change in the amount of data. A conventional driving apparatus and method using the above-cited technologies will now be described. 
     Referring to  FIGS. 1 ,  2  and  3 , the latch circuit  31  of the data driving unit  5  of  FIG. 2  generally comprises (n+1)-data registers  31   R1 - 31   Rm  and n-data latches  31   L1 - 31   Lm . The output circuit  33  of the data driving unit  5  includes digital comparators  33   C1 - 33   Cm , D/A converters  33   D1 - 33   Dm , and output current switches S 1 -S m . 
     Each of the (n+1)-data registers  31   R1 - 31   Rm  outputs a display data signal stored therein according to the horizontal synchronization signal H SYNC  and stores a display data signal D n+1  received from the controller  21  through the interface  30 . The n-data latches  31   L1 - 31   Lm  output display data signals stored therein in response to the horizontal synchronization signal H SYNC  and store the display data signals D n  received from the (n+1)-data registers  31   R1 - 31   Rm , respectively. The D/A converters  32   1 - 32   m  then convert the display data signals D n  in the current horizontal drive time period received from the n-data latches  31   L1 - 31   Lm  into data current signals I DP1 -I DPm , respectively. 
     The digital comparators  33   C1 - 33   Cm  of the output circuit  33  compare the display data signals D n  in the current horizontal drive time period received from n-data latches  31   L1-31   Lm  with the display data signals D n+1  in the next horizontal drive time period received from (n+1)-data registers  31   R1 - 31   Rm , respectively. The digital comparators  33   C1 - 33   Cm  generate booting data signals according to the comparison results. The D/A converters  33   D1 - 33   Dm  convert the booting data signals received from the digital comparators  33   C1 - 33   Cm  into analog signals and output booting current signals I B1 -I Bm , respectively. The output current switches S 1 -S m  apply data output signals I D1 -I Dm  to the data electrode lines  3 , respectively. The data output signals I D1 -I Dm  are generated by alternately selecting the output signals I B1 -I Bm  of the D/A converters  33   D1-33   Dm  of the output circuit  33  or output signals I DP1 -I DPm  of the D/A converters  32   1 - 32   m , respectively. 
     A method for driving a conventional EL display device having a data driving unit  5  as shown in  FIG. 3  will now be described with reference to  FIGS. 3 and 4 . In  FIG. 4 , reference character I DP1  is a data current signal from D/A converter  32   1 , I D1  is a data output signal applied to the data electrode line ( 3   a  of  FIG. 1 ) from the output current switch S 1  corresponding to the D/A converter  32   1 , V D1  is a data voltage signal applied to the data electrode line  3   a , and V S1 -V S6  are scanning voltage signals applied to the scanning electrode lines ( 4  of  FIG. 1 ). 
     With reference to the data output signal I D1 , a booting current corresponds to a magnitude change of a display data signal D n+1  in a next horizontal drive time period with respect to a display data signal D n  in a current horizontal drive time period. The booting current is applied to the data electrode line  3   a  at the beginning of the next horizontal drive time period. An instantaneous value of the booting current is proportional to a magnitude change of the data current signal I DP1 . In connection therewith, first and second drive periods t 1 ˜t 3  and t 3 ˜t 5  will now be representatively described. 
     The magnitude of the data current signal IDPI at the scanning time interval t 2 ˜t 3  increases over that of the data current signal I DP1  at the previous scanning time interval (not shown) during booting time interval t 1 ˜t 2  of the first horizontal drive period t 1 ˜t 3 . A positive polarity booting current, proportional to the amount by which the magnitude of the data current signal I DP1  at the scanning time interval t 2 ˜t 3  increases from the previous scanning time interval, is applied to the data electrode line  3   a.    
     Conversely, the magnitude of the data current signal I DP1  at scanning time interval t 4 ˜t 5  decreases over that of the data current signal I DP1  at the previous scanning time interval t 2 ˜t 3  during booting time interval t 3 ˜t 4  of the second horizontal drive period t 3 ˜t 5 . A negative polarity booting current, proportional to the amount by which the magnitude of the data current signal I DP1  at the scanning time interval t 4 ˜t 5  decreases from the previous scanning time interval t 2 ˜t 3 , is applied to the data electrode line  3   a.    
     Thus, the typical driving apparatus and method can improve the driving speed using the booting current. However, since the instantaneous value of booting current are proportional to the magnitude change of the data current signal I DP1 , the instantaneous value of booting current may increase significantly when the change becomes very large. This may cause crosstalk such that EL cells that are not scanned glow, as well as increase power consumption. 
     SUMMARY OF THE INVENTION 
     The present invention provides a method and apparatus for driving an electro-luminescence (EL) display panel designed to prevent occurrences of crosstalk, that is, when EL cells not scanned emit light, and reduce power dissipation, by efficiently applying a booting current for high speed operation at the beginning of a horizontal drive period. 
     According to an aspect of the present invention, there are provided a method and apparatus for driving an electro-luminescence (EL) display panel having data electrode lines and scanning electrode lines intersecting each other at a predetermined distance and EL cells, where each EL cell is formed at the intersections thereof. In the method and apparatus, a booting current, corresponding to a magnitude change of a display data signal in the next horizontal drive time period with respect to a display data signal in the current horizontal drive time period, is applied to each of the data electrode lines at the beginning of the next horizontal drive time period. Instantaneous values of the booting currents are kept constant, and the application time for the booting current is proportional to a magnitude change of each display data signal in the next horizontal drive time period with respect to the display data signal in the current horizontal drive time period. 
     The method and apparatus for driving the EL display panel make the instantaneous values of the booting currents constant by adjusting the power required for the booting currents according to the application time. Thus, since it is possible to limit excessive increases in instantaneous values of the booting currents, this invention may prevent occurrences of crosstalk caused by unscanned EL cells emitting light, while reducing power consumption. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other features and advantages of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings. 
         FIG. 1  shows the configuration of a conventional electro-luminescence (EL) display device. 
         FIG. 2  is a block diagram showing the configuration of the data driving unit shown in  FIG. 1 . 
         FIG. 3  is a detailed block diagram showing a conventional interior configuration of the data driving unit of  FIG. 2 . 
         FIG. 4  is a timing diagram for explaining a method for driving a conventional EL display device having the data driving unit of  FIG. 3 . 
         FIG. 5  is a detailed block diagram showing an interior configuration of the data driving unit of  FIG. 2  according to the present invention. 
         FIG. 6  is a timing diagram for explaining a method for driving an EL display device having the data driving unit of  FIG. 5  according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Since the basic configuration and operation of the conventional driving circuit described earlier with reference to  FIGS. 1 and 2  also apply to a driving apparatus of this invention, a detailed description thereof will not be given. 
     Referring to  FIGS. 1 ,  2 , and  5 , a latch circuit  51  of the data driving unit  5  of  FIG. 2 , according to the present invention, comprises (n+1)-data registers  51   R1 - 51   Rm  and n-data latches  51   L1 - 51   Lm . An output circuit  53  of the data driving unit according to the invention includes digital comparators  53   C1 - 53   Cm , current sources  53   S1 - 53   Sm , booting-current switches S B1 -S Bm , timing signal generators  53   T1 - 53   Tm , and output current switches S 1 -S m . 
     Each of the (n+1)-data registers  51   R1 - 51   Rm  outputs a display data signal stored therein according to horizontal synchronization signal H SYNC , and stores a display data signal D n+1  received from the controller ( 21  of  FIG. 1 ) through the interface ( 30  of  FIG. 2 ). The n-data latches  51   L1 - 51   Lm  output display data signals stored therein in response to horizontal synchronization signal H SYNC , and store the display data signals D n  received from the (n+1)-data registers  51   R1 - 51   Rm , respectively. Digital-to-analog (D/A) converters  52   1 - 52   m  then convert the display data signals D n  in the current horizontal drive time period received from the n-data latches  51   L1 - 51   Lm  into data current signals I DP1  -I DPm , respectively. 
     The digital comparators  53   C1 - 53   Cm  of the output circuit  53  compare the display data signals D n  in the current horizontal drive time period received from n-data latches  51   L1 - 51   Lm  with the display data signals D n+1  in the next horizontal drive time period received from (n+1)-data registers  51   R1 - 51   Rm , respectively. The digital comparators  53   C1 - 53   CM  generate signals indicating a magnitude change of the display data signals D n+1  with respect to display data signals D n  and generate signals indicating the amount of the change. 
     The current sources  53   S1 - 53   Sm  output booting currents having constant instantaneous values and varying polarities depending on the magnitude change in the signals. Taking a data electrode line as an example, if the magnitude of display data signal D n+1  in the next horizontal drive time period increases over that of display data signal D n  in the current horizontal drive time period, a current source corresponding to the data electrode line outputs a positive polarity booting current during the next horizontal drive time period. Conversely, if the magnitude of display data signal D n+1  in the next horizontal drive time period decreases over that of display data signal D n  in the current horizontal drive time period, the current source corresponding to the data electrode line outputs a negative polarity booting current during the next horizontal drive time period. Since the booting currents are applied to the data electrode lines ( 3  of  FIG. 1 ) at the beginning of each horizontal drive time period, it is possible to increase the speed at which the voltage is applied, i.e., driving speed for the EL cells ( 1  of  FIG. 1 ), despite the presence of parasitic capacitance at the EL cells  1 . 
     The booting-current switches S B1 -S Bm  switch the booting currents I B1 -I Bm  output from the current sources  53   S1 - 53   Sm , respectively. The timing signal generators  53   T1 - 53   Tm  control timing for operation of the booting-current switches S B1 -S Bm  according to the signals indicating the amount of change received from the digital comparators  53   C1 - 53   Cm . Specifically, the timing signal generators  53   T1 - 53   Tm  allow the booting-current switches S B1 -S Bm  to remain ON for a period proportional to the amount of magnitude change of display data signals at the beginning (t 1 ˜t 3 , t 4 ˜t 6 , t 7 ˜t 9 , t 10 ˜t 12 , t 13 ˜t 15 , or t 16 ˜t 18  of  FIG. 6 ) of each horizontal drive time period, respectively. 
     The power required for booting currents is adjusted by the amount of application time, which causes instantaneous values of the booting currents I B1 -I Bm  to be kept constant. Thus, it is possible to limit excessive increases in the instantaneous values of the booting currents I B1 -I Bm , which prevents occurrences of crosstalk, that is, unscanned EL cells emitting light, while reducing power consumption. 
     The output current switches S 1 -S m  apply data output signals I D1 -I Dm  to the data electrode lines  3 , respectively. The data output signals I D1 -I Dm  are generated by alternately selecting from the output signals I B1 -I Bm  of the booting-current switches S B1 -S Bm  and the output signals I DP1 -I DPm  of the D/A converters  52   1 - 52   m , respectively. 
     A method for driving an EL display device having the data driving unit of  FIG. 5  according to the present invention, will now be described with reference to  FIGS. 5 and 6 . In  FIG. 6 , reference character I DP1  is a data current signal from a D/A converter  52   1 , I D1  is a data output signal applied to the data electrode line ( 3   a  of  FIG. 1 ) from the output current switch S 1  corresponding to the D/A converter  52   1 , V D1  is a data voltage signal applied to the data electrode line  3   a , and V S1 -V S6  are scanning voltage signals applied to the scanning electrode lines ( 4  of  FIG. 1 ). 
     With reference to the data output signal I D1 , a booting current, corresponding to a magnitude change of a display data signal D n+1  in the next horizontal drive time period with respect to a display data signal D n  in the current horizontal drive time period, is applied to the data electrode line  3   a  at the beginning t 1 ˜t 3 , t 4 ˜t 6 , t 7 ˜t 9 , t 10 ˜t 12 , t 13 ˜t 15  or t 16 ˜t 18  of the next horizontal drive time period. This makes it possible to increase speed in which the of voltage is applied, i.e., a driving speed for the EL cells ( 1  of  FIG. 1 ), despite the presence of parasitic capacitance at the EL cells  1 . 
     While an instantaneous value I REF  of booting current is kept constant, the amount of application time t 1 ˜t 2 , t 4 ˜t 5 , t 7 ˜t 8 , t 10 ˜t 11 , t 13 ˜t 14  or t 16 ˜t 17  for the booting current is proportional to the amount of magnitude change of the data current signal I DP1 . Thus, the power required for booting current I B1  is adjusted by the amount of application time to keep an instantaneous value of the booting current I B1  constant. It is possible to limit excessive increases in the instantaneous value of the booting current I B1 , which prevents occurrences of crosstalk, that is, unscanned EL cells emitting light, while reducing power consumption. In connection therewith, first and second drive periods t 1 ˜t 3  and t 4 ˜t 7  will now be representatively described. 
     The magnitude of the data current signal I DP1  during scanning time interval t 3 ˜t 4  increases over that of the data current signal I DP1  during the previous scanning time interval (not shown) at the beginning t 1 -t 3  of the first horizontal drive period t 1 ˜t 4 . An instantaneous value +I REF  of positive polarity booting current is applied to the data electrode line  3   a . Here, the application time interval t 1 ˜t 2  is proportional to the amount by which the magnitude of the data current signal I DP1  at the scanning time interval t 3 ˜t 4  increases from previous scanning time interval. 
     Conversely, the magnitude of the data current signal I DP1  during scanning time interval t 6 ˜t 7  decreases over that of the data current signal I DP1  during the previous scanning time interval t 3 ˜t 4  at the beginning of the second horizontal drive period t 4 ˜t 7 . An instantaneous value −I REF  of negative polarity booting current is applied to the data electrode line  3   a . Here, the application time interval t 4 -t 5  is proportional to the amount by which the magnitude of the data current signal I DP1  during the scanning time interval t 6 ˜t 7  decreases from the previous scanning time interval t 3 ˜t 4 . 
     As described above, the method and apparatus for driving an EL display panel according to the present invention make it possible to keep instantaneous values of booting currents constant by adjusting the power required for the booting currents, depending on the amount of application time. Since it is possible to limit excessive increases in instantaneous values of booting currents, this invention may prevent occurrences of crosstalk, that is, when unscanned EL cells emit light, while reducing power consumption. 
     While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims.