JP2004233651A - Method of driving electroluminescence display panel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of driving an electroluminescence display panel on which data electrode lines and scanning electrode lines are formed crossing each other at specified intervals and also electroluminescence cells are formed in their intersection areas. <P>SOLUTION: Included are precharging, scanning, and repetition stages. In the precharging period, data signal applied to all the data electrode lines are cut off, a 1st potential is applied to all the scanning electrode lines, and all the data electrode lines are electrically connected to one another by switching. In the scanning stage, a 2nd potential which is lower than the 1st potential is applied to all the scanning electrode lines and data signals are applied to the data electrode lines, so that electroluminescence display cells whose scanning electrode liens are selected illuminate. In the repetition stage, the precharging and scanning stages are repeated for the remaining scanning electrode lines. Consequently, since a relatively high potential is applied to all the scanning electrode lines in the precharging period and a voltage is reversely applied to all electroluminescence cells, a crosstalk through data electrode lines in the precharging period is prevented. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a driving method of an electroluminescent display panel, and more particularly, a data electrode line and a scanning electrode line are formed to intersect with each other at a predetermined interval, and an electroluminescent display cell is formed in the intersection area. And a method for driving the electroluminescent display panel.
[0002]
[Prior art]
Referring to FIG. 1, a general electroluminescent display device includes an electroluminescent display panel 2 and a driving device. The drive device includes a control unit 21, a scan drive unit 6, and a data drive unit 5. Here, the switch 25 and the voltage holding circuit 22 are included in the electroluminescent display panel 2 or included in the driving device.
[0003]
The data electrode lines 3 and the scan electrode lines 4 are formed on the electroluminescent display panel 2 so as to intersect with each other at a predetermined interval, and the electroluminescent display cell 1 is formed in the intersection area.
[0004]
The control unit 21 processes the input video signal and inputs a display data signal and a switching control signal to the data driving unit 5, and inputs a switching control signal to the scan driving unit 6 and the switch 25. The scan driver 6 operates according to the switching control signal from the controller 21 to drive the scan electrode lines 4. The data driver 5 operating according to the switching control signal from the controller 21 drives the data electrode lines 3 according to the display data signal from the controller 21.
[0005]
The switch 25 operates according to a switching control signal from the control unit 21 to electrically connect or disconnect all the data electrode lines 3 to each other. The voltage holding circuit 22 composed of a parallel circuit of the capacitor 24 and the Zener diode 23 determines the lower limit voltage of the data electrode line 3 as the breakdown voltage of the Zener diode 23.
[0006]
With reference to FIG. 1 and FIG. 2, a method of driving the electroluminescent display panel 2 normally, for example, a driving method of Japanese Patent Application Laid-Open No. 2002-108284 will be described as follows. S _PC in Figure 2, the data driver 5 from the control unit 21, a scan driver 6, and shows the pre-charge signal input to the switch 25. S _Sn indicates a scan drive signal applied from the scan driver 6 to the n-th scan electrode line, for example, the scan electrode line 4a. S _{Sn + 1} indicates a scan drive signal applied from the scan driver 6 to the (n + 1) th scan electrode line, for example, the scan electrode line 4b. V _{Dn + 1} indicates a voltage waveform applied to any one data electrode line.
[0007]
Each of the horizontal driving times a and b includes a precharge stage c and scanning stages t2 to t3 and t4 to t5.
[0008]
In the precharge stages t1 to t2 of the n-th horizontal driving time a, data signals applied to all data electrode lines 3 are cut off. The scanning switches 10a,. . . , 10c, the first potential, which is a high potential that does not cause the electroluminescent cell to emit light, is applied to all other scan electrode lines outside the n-th scan electrode line, and the first potential is applied to the n-th scan electrode line. A ground potential as a lower second potential is applied. Then, all data electrode lines 3 are connected to the voltage holding circuit 2 by the operation of the switch 25. As a result, the electric charge charged in the parasitic capacitance of the (n-1) th scan electrode line that has been emitted during the scan time of the previous horizontal drive time is discharged to the voltage set by the voltage holding circuit 22. Becomes uniform.
[0009]
During t2 to t3 of the n-th horizontal driving time a, all the data electrode lines 3 are electrically separated from each other by the operation of the switch 25, and a display data signal is applied to the data electrode lines 3 to select the n-th scan electrode line. The electroluminescent display cell emits light. Since the potentials of all the data electrode lines are set higher than the ground potential during the precharge periods t1 to t2, the voltage is applied to the selected electroluminescent display cell more quickly, so that the brightness increases.
[0010]
The above operation principle is also applied to the (n + 1) th horizontal drive time b.
[0011]
The internal operation of the scan driver 6 of FIG. 1 for realizing the driving method of FIG. 2 will now be described with reference to FIGS. 1 to 3B. In FIGS. 3A and _{3B, S TP} is applied from the control unit 21 of the signal input to the data input terminal D of the 1D-type _{flip-flop, S PC} to a clock terminal CLK of all D-type flip-flop from the control unit 21 a signal, the signal S _S1 applied to the first scan electrode line 4a, S _{S 2} is the signal applied to the second scan electrode lines 4b, S _Sn is applied to the n-th scan electrode lines 4c Respectively.
[0012]
A voltage of a logic high state to a data terminal D of the 1D-type flip-flop is applied at a first horizontal synchronizing the time t1 before and after the time of the initial operation, the pulse of the precharge signal S _PC is applied at a first horizontal synchronizing time t1 . As a result, only the signal _SS1 applied to the first scan electrode line 4a is in a logic low state during the first horizontal driving time a, and the signals applied to the remaining scan electrode lines 4b and 4c are in a logic high state. Here, the precharge operation is performed in precharge stages t1 and t2, and the scanning operation is performed in t2 and t3.
[0013]
Then, the signal _{S PC} the pulse is applied at a second horizontal synchronization time point t3. Accordingly, only the signal S _S2 applied to the second scan electrode lines 4b in the second horizontal driving time b becomes a logic low state, the signal applied remaining scan electrode lines 4a, and 4c becomes a logic high state. Here, the precharge operation is performed from t3 to t4, and the scanning operation is performed from t4 to t5.
[0014]
According to the conventional method of driving an electroluminescent display panel described above, when the electroluminescent cell connected to the n-scan electrode line is selected and emits light, the parasitic capacitance of the data electrode line 3 is added to the electroluminescent cell. The charge of the driving voltage is stored. Then, when the (n + 1) th scan electrode line is selected, the charge stored during the period of the (n) scan electrode line is discharged by the switch 25 during the precharge period. This discharge has an exponential curve due to the time constant of the wiring resistance and the parasitic capacitance of the data electrode line. At this time, a voltage that discharges according to an exponential curve is applied to the electroluminescent cell connected to the (n + 1) -th scan electrode line, so that the cell emits light either instantaneously or. There is a problem that this light emission appears as crosstalk.
[0015]
[Patent Document 1]
JP-A-2002-108284
[Problems to be solved by the invention]
SUMMARY OF THE INVENTION It is an object of the present invention to provide a method of driving an electroluminescent display panel in which precharge is performed at an early stage of a horizontal driving time and crosstalk through data electrode lines is prevented.
[0017]
[Means for Solving the Problems]
According to an aspect of the present invention, there is provided a driving method of an electroluminescent display panel in which a data electrode line and a scanning electrode line are formed to intersect with each other at a predetermined interval, and an electroluminescent display cell is formed in the intersection area. The method includes the steps of precharging, scanning and repeating. In the precharging step, data signals applied to the data electrode lines are cut off, a first potential is applied to the scan electrode lines, and the data electrode lines are electrically connected to each other by switching. In the scanning step, a second potential lower than the first potential is applied to a certain scan electrode line, and a data signal is applied to the data electrode line, so that a selected electroluminescent display cell of the scan electrode line emits light. In the repetition step, the precharge and scanning steps are repeatedly performed on the remaining scan electrode lines.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described in detail.
[0019]
7A to 7C, the same reference numerals as those in FIG. 1 indicate the same functional objects. A method of driving the electroluminescent display panel 2 according to the present invention will be described with reference to FIGS. 4 and 7A to 7C. S _PC in Figure 4 shows a precharge signal input from the control unit 21 the data driver 5, the scan driving unit 6 and the switch 25. S _Sn indicates a scan drive signal applied from the scan driver 6 to the n-th scan electrode line, for example, the scan electrode line 4a. S _{Sn + 1} indicates a scan drive signal applied from the scan driver 6 to the (n + 1) th scan electrode line, for example, the scan electrode line 4b. V _{Dn + 1} indicates a voltage waveform applied to any one data electrode line.
[0020]
Each of the horizontal driving times a and b includes a precharge stage c and scanning stages t2 to t3 and t4 to t5.
[0021]
In the precharge stages t1 to t2 of the n-th horizontal driving time a, data signals applied to all data electrode lines 3 are cut off. The scanning switches 10a,. . . , 10c, the first potential, which is a high potential at which the electroluminescent cell does not emit light, is applied to all the scan electrode lines 4 (see FIG. 7B). Then, all data electrode lines 3 are connected to the voltage holding circuit 22 by the operation of the switch 25 (see FIG. 7B). As a result, the charges charged in the parasitic capacitance of the (n-1) th scan electrode line emitted during the previous scanning period of the horizontal driving time are discharged to the voltage set by the voltage holding circuit 22. The potential of the electrode line becomes uniform. At this time, the first potential is applied to all the scan electrode lines 4 and the reverse voltage is applied to all the electroluminescent cells 1, so that crosstalk through the data electrode lines 3 is prevented.
[0022]
In the scan stages t2 to t3 of the n-th horizontal drive time a, the ground potential as the second potential lower than the first potential is applied to the n-th scan electrode line by the operation of the n-th scan switch, for example, the scan switch 10a or 10b. Is done. At the same time, the data electrode lines 3 are electrically separated from each other by the operation of the switch 25, and a display data signal is applied to the data electrode lines 4 to emit light from the selected electroluminescent display cell of the nth scan electrode line. (See FIG. 7A or 7C). Since the potentials of all the data electrode lines are set higher than the ground potential in the precharge stages t1 to t2, the voltage is applied to the selected electroluminescent display cell more quickly, so that the brightness increases.
[0023]
The above operation principle is also applied to the (n + 1) th horizontal drive time b.
[0024]
Referring to FIGS. 4 to 5B and FIGS. 7A to 7C, the internal operation of the scan driver 6 of FIGS. 7A to 7C for realizing the driving method of FIG. 4 will be described as follows. _{S TP} in FIGS. 5A and 5B, application of a signal input from the control unit 21 to the data input terminal D of the 1D-type _{flip-flop, S PC} from the control unit 21 to the clock terminal CLK of all D-type flip-flop _SQ1 is the signal of the inverted output terminal / Q of the first D-type flip-flop (in the figure, a horizontal line is drawn above Q), and _SQ2 is the inverted output of the second D-type flip-flop. The signal at the terminal / Q, S _S1 applies a signal applied to the first scan electrode line 4a, S _S2 applies a signal applied to the second scan electrode line 4b, and S _Sn applies an signal to the n-th scan electrode line 4c. Respectively.
[0025]
Voltage of a logic high state to a data terminal D of the 1D-type flip-flop in the first horizontal synchronization behavior early time point t1 around time is applied, the signal S _PC the pulse is applied at a first horizontal synchronizing time t1. As a result, the signal S _Q1 of the inverted output terminal / Q of the first D-type flip-flop becomes a logic low state in the first horizontal drive time a, and the signals S _Q2 , S of the inverted output terminal / Q of the remaining D-type flip-flops become logic low. _Qn goes to a logic high state. Also, the signal _SS1 applied to the first scan electrode line 4a is in a logic low state only during the scan time t2 to t3, and the signals applied to the remaining scan electrode lines 4b and 4c are in a logic high state. Here, the precharge operation is performed between t1 and t2 (see FIG. 7B), and the scanning operation is performed between t2 and t3 (see FIG. 7A or 7C).
[0026]
Then, the signal _{S PC} the pulse is applied at a second horizontal synchronization time point t3. As a result, the signal S _Q2 of the inverted output terminal / Q of the second D-type flip-flop becomes a logic low state in the second horizontal drive time b, and the signals S _Q1 , S of the inverted output terminal / Q of the remaining D-type flip-flops become logic low. _Qn goes to a logic high state. Also, the signal S _S2 applied to the second scan electrode line 4b is in a logic low state only during the scan time t4 to t5, and the signals applied to the remaining scan electrode lines 4a and 4c are in a logic high state. Here, the precharge operation is performed between t3 and t4 (see FIG. 7B), and the scanning operation is performed between t4 and t5 (see FIG. 7A or 7C).
[0027]
FIG. 6 shows an internal configuration of the data driving unit 5 of FIGS. 7A to 7C for realizing the driving method of FIG. Referring to FIGS. 6 and 7A to 7C, the data driver 5 includes an interface 30, a latch 31, a digital-analog converter 32, a driving circuit 33, and an output unit 34.
[0028]
The interface 30 interfaces the display data signal from the control unit 21 and inputs it to the latch 31, and interfaces the timing control signal from the control unit 21 to input it to the latch 31, the digital-analog conversion unit 32 and the drive circuit 33. . The display data signal from the interface 30 is input to the digital-analog converter 32 after being temporarily held by the latch 31. The digital-analog conversion unit 32 operated by the timing control signal from the interface 30 converts the display data signal from the latch 31 into an analog signal and inputs the analog signal to the drive circuit 33.
[0029]
The drive circuit 33 operated by the timing control signal from the interface 30 drives the current source 8 by the display data signal from the digital-analog converter 32 to generate a display data signal by the current. The output unit 34 outputs a display data signal from the drive circuit 33 to the data electrode line 3.
[0030]
The present invention is not limited to the above embodiments, but can be modified and improved by those skilled in the art within the spirit and scope of the invention defined in the appended claims.
[0031]
【The invention's effect】
As described above, according to the method of driving an electroluminescent display panel according to the present invention, a relatively high potential is applied to every scan electrode line during a precharge period, and a reverse voltage is applied to every electroluminescent cell. Therefore, crosstalk through the data electrode line during the precharge period is prevented.
[Brief description of the drawings]
FIG. 1 is a view illustrating a configuration of a general electroluminescent display device.
FIG. 2 is a timing diagram illustrating a method of normally driving the electroluminescent display panel of FIG. 1;
FIG. 3A is a circuit diagram illustrating an internal configuration of a scan driver of FIG. 1 that implements the drive method of FIG. 2;
FIG. 3B is a voltage waveform diagram showing the signal of FIG. 3A.
FIG. 4 is a timing diagram illustrating a method of driving the electroluminescent display panel of FIG. 1 according to an embodiment of the present invention.
5A is a circuit diagram showing an internal configuration of a scan driver of FIGS. 7A to 7C for realizing the driving method of FIG. 4;
FIG. 5B is a voltage waveform diagram showing the signal of FIG. 5A.
FIG. 6 is a circuit diagram showing an internal configuration of a data driver of FIGS. 7A to 7C for realizing the driving method of FIG. 4;
FIG. 7A is a diagram illustrating a switching state of the first scan electrode line while the scan step of FIG. 4 is performed.
7B is a diagram illustrating a switching state during a precharge step of FIG. 4 performed after the scan step of FIG. 7A.
FIG. 7C
FIG. 7B is a diagram illustrating a switching state during a scan step of FIG. 4 performed on a second scan electrode line after the precharge step of FIG. 7B.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 electroluminescent element 2 electroluminescent display panel 3 data electrode line 4 scan electrode line 5 data drive unit 6 scan drive unit 8 current sources 10 a and 10 c scan switch 21 control unit 22 voltage holding circuit 25 charging switch

Claims (2)

A data electrode line and a scan electrode line are formed to intersect with each other at a predetermined interval, and a method of driving an electroluminescent display panel in which an electroluminescent display cell is formed in the intersection area.
Blocking a data signal applied to all the data electrode lines, applying a first potential to the scan electrode lines, and electrically connecting the data electrode lines to each other by switching;
Applying a second potential lower than the first potential to a certain scan electrode line, applying a data signal to the data electrode line, and causing a selected electroluminescent display cell of the scan electrode line to emit light;
Repeating the precharging and scanning steps for the remaining scan electrode lines. In the precharge step,
2. The method according to claim 1, wherein the data electrode lines are commonly connected to a cathode of the Zener diode, and the second potential is applied to an anode of the Zener diode.

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