Display and a driving method thereof

• US 7,057,589 B2
• Filed: 02/20/2003
• Issued: 06/06/2006
• Est. Priority Date: 03/21/2002
• Status: Expired due to Term

• Current Assignee: Samsung Display Company Limited (Samsung Electronics Co. Ltd.)
• Original Assignee: Samsung SDI Company Limited
• Inventors: Shin, Dong-Yong, Kwon, Oh-Kyong
• Primary Examiner(s): LAO, LUN YI
• Application Number:
  US10/370,882
• Publication Number:
  US 20030179164A1
• Time in Patent Office: 1,202 Days
• Field of Search: 345 76- 82, 345 87-103, 345208-210, 345204-205, 315/169.1, 315/169.3
• US Class Current: 345/82
• CPC Class Codes: G09G 2300/0809 Several active elements per pixel in active matrix panels
• CPC Class Codes: G09G 2300/0819 used for counteracting undesired variations, e.g. feedback or autozeroing
• CPC Class Codes: G09G 2300/0842 forming a memory circuit, e.g. a dynamic memory with one capacitor
• CPC Class Codes: G09G 2310/0248 Precharge or discharge of column electrodes before or after applying exact column voltages
• CPC Class Codes: G09G 2310/0251 Precharge or discharge of pixel before applying new pixel voltage
• CPC Class Codes: G09G 2310/0262 The addressing of the pixel, in a display other than an active matrix LCD, involving the control of two or more scan electrodes or two or more data electrodes, e.g. pixel voltage dependent on signals of two data electrodes
• CPC Class Codes: G09G 2310/0297 Special arrangements with multiplexing or demultiplexing of display data in the drivers for data electrodes, in a pre-processing circuitry delivering display data to said drivers or in the matrix panel, e.g. multiplexing plural data signals to one D/A converter or demultiplexing the D/A converter output to multiple columns
• CPC Class Codes: G09G 2320/043 Preventing or counteracting the effects of ageing
• CPC Class Codes: G09G 3/3233 with pixel circuitry controlling the current through the light-emitting element
• CPC Class Codes: G09G 3/3291 in which the data driver supplies a variable data voltage for setting the current through, or the voltage across, the light-emitting elements

Abstract

In a display, capacitors are charged with first precharge voltages at the time of applying selection signals to previous scan lines. A data driver divides a plurality of data lines into a plurality of groups each of which consists of at least one data line and applies corresponding data voltages to the data lines of respective groups sequentially. The display further includes a precharge means, and such precharge means applies second precharge voltages to data lines of at least one group before selection signals for selecting scan line are applied to the scan line connected to the pixel circuits and stops application of the second precharge voltages before corresponding data voltages are applied to the respective groups. In this way, it is possible to solve the problem of poor images due to charge redistribution of the capacitors caused by previous data voltages stored in parasitic capacitors.

Claims

1. An organic electroluminescence display comprising:

a plurality of data lines transmitting data voltages;

a plurality of scan lines transmitting selection signals;

a plurality of pixel circuits provided in pixel areas defined by two adjacent data lines and two adjacent scan lines, and having first switching elements responding to the selection signals applied to the scan lines to transmit the data voltages applied to the data lines, first thin film transistors supplying currents to organic electroluminescence devices in correspondence to the data voltages inputted to gates thereof through the first switching elements, capacitors for maintaining the data voltages during a certain time, and second switching elements applying first precharge voltages to the capacitors in response to control signals while the selection signals are applied to previous scan lines;

a data driver dividing the data lines into a plurality of groups to selectively apply the data voltages to the respective groups by group unit; and

a demultiplexer applying the data voltages selectively applied from the data driver to corresponding data lines and applying second precharge voltages based on the first precharge voltages to the data lines of at least one group out of the groups before the selection signals for selecting scan lines are applied to the scan lines connected to the pixel circuits.

2. The organic electroluminescence display of claim 1, wherein the demultiplexer includes:

a plurality of third switching elements, each connected to the data line, and turned on when data voltage corresponding to the connected data line is applied; and

a plurality of fourth switching elements, each connected between signal for the second precharge voltage and data line of at least one group, and turned on before the selection signal is applied to the scan line connected to the pixel circuit and turned off when the corresponding data voltage is applied to the connected data line.

3. The organic electroluminescence display of claim 2, wherein the data driver divides the data lines into three groups to which the data voltages corresponding to first to third colors are applied, thereby outputs the data voltages corresponding to the first to the third colors sequentially, and

wherein the plurality of fourth switching elements are connected to the data lines corresponding to at least one color of the first to the third colors.

4. The organic electroluminescence display of claim 1, wherein the pixel circuits include second thin film transistors of which the gates are connected to the gates of the first thin film transistors and that are diode-connected between the first switching elements and the second switching elements, and wherein the second precharge voltage has a value equal to ‘

the first precharge voltage—

threshold voltage of the second thin film transistor’

or a value further from the data voltage.

5. The organic electroluminescence display of claim 1, wherein the control signals are selection signals applied to previous scan lines.

6. The organic electroluminescence display of claim 1, wherein the control signals are separate reset signals.

7. The organic electroluminescence display of claim 1, wherein the second precharge voltages have constant values.

8. An organic electroluminescence display comprising:

a plurality of data lines transmitting data voltages;

a plurality of scan lines transmitting selection signals;

a plurality of pixel circuits provided in pixel areas defined by two adjacent data lines and two adjacent scan lines, and having first switching elements responding to the selection signals applied to the scan lines to transmit the data voltages applied to the data lines, first thin film transistors supplying currents to organic electroluminescence devices in correspondence to the data voltages inputted to gates thereof through the first switching elements, capacitors for maintaining the data voltages during a certain time, and second switching elements applying first precharge voltages to the capacitors in response to control signals while the selection signals are applied to previous scan lines;

a data driver applying the data voltages to the data lines sequentially; and

a precharge means applying second precharge voltages to the data lines before the selection signals for selecting scan lines are applied to the scan lines and stopping the application of the second precharge voltages simultaneously when the data voltage is applied to any one of the data lines to which the precharge voltages are applied.

9. The organic electroluminescence display of claim 8, wherein the data driver includes:

a plurality of third switching elements, each connected between at least one signal line transmitting image signals representing the data voltages and the data lines, to perform switching operations when the image signals have values corresponding to the data lines; and

a shift register sequentially outputting a plurality of switching signals for driving the third switching elements, respectively,

wherein the precharge means includes a plurality of fourth switching elements connected between a second signal line for transmitting the second precharge voltages and the data lines, and turned on simultaneously before the selection signals for selecting scan lines are applied to the scan lines connected to the pixel circuits and turned off simultaneously when the data voltage is applied to any one of the connected data lines.

10. The organic electroluminescence display of claim 9, wherein the fourth switching elements are connected to at least second to last data lines of the data lines, respectively.

11. The organic electroluminescence display of claim 9, wherein, when both of two adjacent outputs of the shift register have levels for driving the third switching elements, the switching signals are changed into levels for driving the third switching elements.

12. The organic electroluminescence display of claim 8, wherein the pixel circuits include second thin film transistors of which gates are connected to the gates of the first thin film transistors and that are diode-connected between the first switching elements and the second switching elements, and wherein the second precharge voltage has a value equal to ‘

the first precharge voltage—

threshold voltage of the second thin film transistor’

or a value further from the data voltage.

13. The organic electroluminescence display of claim 8, wherein the control signals are selection signals applied to previous scan lines.

14. The organic electroluminescence display of claim 8, wherein the control signals are separate reset signals.

15. The organic electroluminescence display of claim 8, wherein the precharge voltages have constant values.

16. An organic electroluminescence display comprising:

a plurality of data lines transmitting data voltages;

a plurality of scan lines transmitting selection signals;

a plurality of pixel circuits provided in pixel areas defined by two adjacent data lines and two adjacent scan lines, and having first switching elements responding to the selection signals applied to the scan lines to transmit the data voltages applied to the data lines, first thin film transistors supplying currents to organic electroluminescence devices in correspondence to the data voltages inputted to gates thereof through the first switching elements, capacitors for maintaining the data voltages during a certain time, and second switching elements applying first precharge voltages to the capacitors in response to control signals while the selection signals are applied to previous scan lines;

a data driver applying the data voltages to the data lines sequentially; and

a precharge means applying second precharge voltages based on the first precharge voltages to the data lines before the selection signals for selecting scan lines are applied to the scan lines connected to the pixel circuits, and sequentially stopping the application of the second precharge voltages to the respective data lines before the data voltages are applied to the respective data lines.

17. The organic electroluminescence display of claim 16, wherein the data driver includes a plurality of third switching elements connected between at least one first signal line for transmitting image signals representing data voltages and the data lines, to perform switching operations when the image signals have values corresponding to the data lines;

and a shift register sequentially outputting a plurality of switching signals for driving the third switching elements, respectively,

wherein, the precharge means includes a plurality of fourth switching elements connected between a second signal line for transmitting the precharge voltages and the data lines; and

a plurality of precharge control signal generators receiving precharge control signals for driving the fourth switching elements connected to the previous data lines and the switching signals for driving the third switching elements connected to the previous data lines, and generating precharge control signals for driving the fourth switching elements connected to the present data lines.

18. The organic electroluminescence display of claim 17, wherein the precharge control signal generators are composed of AND gates receiving the switching signals for driving the third switching elements connected to the previous data lines and the precharge control signals for driving the fourth switching elements connected to the previous data lines.

19. The organic electroluminescence display of claim 17, wherein the precharge control signal generators generate precharge control signals for turning off the fourth switching elements connected to the present data lines when switching signals for turning on the third switching elements connected to next data lines are applied.

20. The organic electroluminescence display of claim 19, wherein the precharge control signal generators include OR gates receiving inverted values of switching signals for driving the third switching elements connected to next data lines and switching signals for driving the third switching elements connected to the present data lines as inputs;

and AND gates receiving outputs of the OR gates and previous precharge control signals as inputs,

wherein the outputs of the AND gates become precharge control signals.

21. The organic electroluminescence display of claim 17, wherein, when both of the two adjacent outputs of the shift register have levels for driving the third switching elements, the switching signals are changed into devels for driving the third switching elements.

22. The organic electroluminescence display of claim 17, wherein the pixel circuits include second thin film transistors of which gates are connected to the gates of the first thin film transistors and that are diode-connected between the first switching elements and the second switching elements, and wherein the second precharge voltage has a value equal to ‘

the first precharge voltage—

threshold voltage of the second thin film transistor’

or a value further from the data voltage.

23. The organic electroluminescence display of claim 17, wherein the control signals are selection signals applied to previous scan lines.

24. The organic electroluminescence display of claim 17, wherein the control signals are separate reset signals.

25. The organic electroluminescence display of claim 17, wherein the precharge voltages have constant values.

26. A method of driving an organic electroluminescence display comprising a plurality of data lines transmitting data voltages;

a plurality of scan lines transmitting selection signals; and

a plurality of pixel circuits provided in pixel areas defined by two adjacent data lines and two adjacent scan lines, and having first thin film transistors supplying currents to organic electroluminescence devices and capacitors for maintaining the data voltages during a certain time, the method comprising;

(a) precharging the capacitor of the pixel circuit connected to i-th scan line with the first precharge voltage while selection signal is applied to (i−

1)th scan line;

(b) applying second precharge voltages based on the first precharge voltages to the data lines before selection signal is applied to the i-th scan line; and

(c) stopping application of the second precharge voltage when the data voltages are applied to the data lines to which the second precharge voltages have been applied, applying corresponding data voltages to the respective groups of the data lines which consist of at least one data line.

27. The method of claim 26, wherein, in the step (b), the precharge voltages are applied to the data lines at the same time.

28. The method of claim 26, wherein, in the step (b), the second precharge voltages are applied to the data lines sequentially.

29. The method of claim 26, wherein, in the step (c), application of the second precharge voltages is stopped for all data lines before data voltages are applied to any one of groups to which the second precharge voltages have been applied.

30. The method of claim 26, wherein, in the step (C), before data voltages are sequentially applied to groups to which the second precharge voltages have been applied, applications of the second precharge voltages to the respective groups are stopped sequentially.

31. The method of claim 26, wherein the second precharge voltages have constant values.

32. The method of claim 26, wherein each of the pixel circuits includes a switching element connected between the capacitor and the first precharge voltage,

wherein, in the step (a), the switching elements are driven by selection signal applied to (i−

1)-th scan line to charge the capacitors with the first precharge voltages.

33. The method of claim 26, wherein each of the pixel circuits includes a switching element connected between the capacitor and the first precharge voltage, wherein, in the step (a), the capacitors are charged with the first precharge voltages by separate reset signals.

34. A display comprising:

a plurality of data lines transmitting data voltages representing the image signals;

a plurality of scan lines transmitting selection signals;

a plurality of pixel circuits provided in pixel areas defined by two adjacent data lines and two adjacent scan lines, and having first switching elements responding to the selection signals applied to the scan lines to transmit the data voltages applied to the data lines, capacitors for maintaining the data voltages during a certain time, and second switching elements applying first precharge voltages to the capacitors in response to control signals while the selection signals are applied to previous scan lines;

a data driver dividing the data lines into a plurality of groups to selectively apply the corresponding data voltages to the respective groups; and

a precharge means applying second precharge voltages based on the first precharge voltages to the data lines of at least one group before the selection signals for selecting scan lines are applied to the scan lines connected to the pixel circuits, and stopping the application of the second precharge voltages when the corresponding data voltages are applied to the groups.

35. The display of claim 34, wherein the second precharge voltage has a value equal to ‘

the first precharge voltage—

threshold voltage of a thin film transistor’

or a value further from the data voltage.

36. The display of claim 34, wherein the precharge voltages have constant values.

37. The display of claim 34, wherein the control signals are selection signals applied to previous scan lines.

38. The display of claim 34, wherein the control signals are separate reset signals.