Light emission display, display panel, and driving method thereof

• US 20050200575A1
• Filed: 03/08/2005
• Published: 09/15/2005
• Est. Priority Date: 03/10/2004
• Status: Active Grant

• Current Assignee: Samsung Display Company Limited (Samsung Electronics Co. Ltd.)
• Original Assignee: Samsung SDI Company Limited
• Inventors: Kim, Yang-Wan, Oh, Choon-Yul
• Granted Patent: US 7,382,340 B2
• Time in Patent Office: Days
• US Class Current: 345/76
• CPC Class Codes: G09G 2300/043 Compensation electrodes or other additional electrodes in matrix displays related to distortions or compensation signals, e.g. for modifying TFT threshold voltage in column driver
• CPC Class Codes: G09G 2300/0819 used for counteracting undesired variations, e.g. feedback or autozeroing
• CPC Class Codes: G09G 2300/0852 being a dynamic memory with more than one capacitor
• CPC Class Codes: G09G 2300/0861 with additional control of the display period without amending the charge stored in a pixel memory, e.g. by means of additional select electrodes
• 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 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

Abstract

A light emission display includes data lines, scan lines, and pixel circuits. A pixel circuit of the pixel circuits includes: a light emission element; a first transistor including a control electrode and first and second electrodes, the first transistor outputting a current corresponding to a voltage between the first electrode and the control electrode; a first switch coupled between the control electrode of the first transistor and the light emission element and for receiving a first control signal; a first capacitor coupled to the first transistor; a second capacitor coupled between a first power source and the first capacitor; a second switch for coupling the first capacitor and a second power source in response to a second control signal; and a third switch for applying a data voltage to the first capacitor in response to a select signal provided by one of the scan lines.

Claims

1. A pixel circuit coupled to a first scan line for applying a first signal, a second scan line for applying a second signal, and a data line for applying a data voltage, the pixel circuit comprising:

a driving transistor including a control electrode, a first electrode coupled to a first power source, and a second electrode and for outputting a current corresponding to a voltage between the first electrode and the control electrode;

a display element coupled to the second electrode of the driving transistor and for displaying an image corresponding to the current output from the driving transistor;

a first switching transistor coupled between the control electrode of the driving transistor and the display element;

a compensation device for electrically coupling the control electrode of the driving transistor to a second power source in response to the first signal;

a storage capacitor coupled between the first power source and the compensation device; and

a second switching transistor for applying the data voltage to the compensation device in response to the second signal.

2. The pixel circuit of claim 1, further comprising a third switching transistor for interrupting an electrical connection between the display element and the second electrode of the driving transistor in response to the first signal.

3. The pixel circuit of claim 1, wherein the compensation device comprises a compensation capacitor and a third switching transistor, the compensation capacitor having a first capacitor electrode coupled to the control electrode of the driving transistor and a second capacitor electrode, the third switching transistor electrically coupling the second capacitor electrode of the compensation capacitor to the second power source in response to the first signal.

4. The pixel circuit of claim 3, wherein the electrically coupling of the second capacitor electrode of the compensation capacitor and the second power source by the third switching transistor allows the display element to display the image corresponding to the current output from the driving transistor without influences from the first power source.

5. The pixel circuit of claim 1, wherein the current output from the driving transistor for displaying the image of the display element corresponds to the data voltage and a voltage of the second power source.

6. A display device including a plurality of data lines for applying a data voltage corresponding to an image signal, a plurality of scan lines for applying a select signal, and a plurality of pixel circuits coupled to the scan lines and the data lines, wherein at least one of the pixel circuits comprises:

a display element for displaying the image signal corresponding to an applied current;

a first transistor including a control electrode, a first electrode coupled to a first power source, and a second electrode coupled to the display element, the first transistor outputting the applied current corresponding to a voltage between the first electrode and the control electrode;

a first switch coupled between the control electrode of the first transistor and the display element and for receiving a first control signal;

a first capacitor having a first capacitor electrode coupled to the control electrode of the first transistor and a second capacitor electrode;

a second capacitor coupled between the first power source and the second capacitor electrode of the first capacitor;

a second switch for electrically coupling the second capacitor electrode of the first capacitor and a second power source in response to a second control signal; and

a third switch for applying a data voltage provided by one of the data lines to the second capacitor electrode of the first capacitor in response to a first select signal provided by one of the scan lines.

7. The display device of claim 6, wherein the first control signal and the second control signal are applied to turn on the first and second switches before the first select signal is applied from the one scan line.

8. The display device of claim 6, further comprising a fourth switch for interrupting an electrical connection between the light emission element and the second electrode of the first transistor in response to a third control signal.

9. The display device of claim 8, wherein the third control signal is applied to the fourth switch during an interval in which the first and second control signals are applied to turn on the first and second switches, respectively.

10. The display device of claim 9, wherein the first and second switches comprise transistors doped to have a first type of major carriers, and the fourth switch comprises a transistor doped to have a second type of major carriers, and wherein the first type differs from the second type.

11. The display device of claim 10, wherein the first, second and third control signals are substantially the same signal.

12. The display device of claim 10, wherein the first, second, and third control signals comprise a second select signal provided by another one of the scan lines.

13. A display panel of a display device including a plurality of data lines for applying a data voltage corresponding to an image signal, a plurality of scan lines for applying a select signal, and a plurality of pixel circuits coupled to the scan lines and the data lines, wherein at least one of the pixel circuits comprises:

a display element for displaying the image signal corresponding to an applied current;

a transistor including a control electrode, a first electrode coupled to a first power source, and a second electrode coupled to the display element, the first transistor outputting the applied current corresponding to a voltage applied between the control electrode and the first electrode to the second electrode;

a first capacitor having a first capacitor electrode coupled to the control electrode of the transistor and a second capacitor electrode; and

a second capacitor coupled between the first power source and the second capacitor electrode of the first capacitor, and

wherein the at least one pixel circuit is operated in the order of

a first interval in which the second capacitor electrode of the first capacitor is coupled to a second power source to charge the first capacitor,

a second interval in which the second capacitor is charged with a data voltage provided by one of the data lines, and

a third interval in which the second electrode of the transistor and the display element are coupled to display the image signal.

14. The display panel of claim 13, wherein a voltage charged in the first capacitor substantially corresponds to a value obtained by subtracting a voltage of the second power source from a sum of a voltage of the first power source and a threshold voltage at the transistor.

15. The display panel of claim 13, wherein the second and third intervals are performed substantially at the same time.

16. The display panel of claim 13, wherein an absolute value of a value obtained by subtracting a voltage of the second power source from the sum of the data voltage and a threshold voltage at the transistor is established to be greater than an absolute value of the threshold voltage at the transistor.

17. The display panel of claim 16, wherein the voltage of the second power source is established to substantially correspond to the voltage of the first power source.

18. The display panel of claim 13, wherein the voltage applied between the control electrode and the first electrode of the transistor substantially corresponds to a value obtained by subtracting a voltage of the second power source from the sum of the data voltage and a threshold voltage at the transistor.

19. A method for driving a plurality of pixel circuits in a matrix format,

wherein at least one of the pixel circuits includes a light emission element for emitting light in correspondence to an applied current, a transistor being coupled between a first power source and the light emission element and outputting the applied current corresponding to a voltage applied to a gate of the transistor, a first capacitor having a first capacitor electrode coupled to the gate of the first transistor and a second capacitor electrode, and a second capacitor coupled between the first power source and the second capacitor electrode of the first capacitor, and

wherein the method for driving the pixel circuits comprises:

(a) charging the first capacitor with a voltage of a second power source separately formed from a threshold voltage of the transistor and a voltage of the first power source;

(b) charging the second capacitor with a voltage corresponding to a data voltage provided by one of the data lines; and

(c) driving the transistor according to the voltages charged in the first and second capacitors.

20. The method of claim 19, wherein (b) and (c) are performed substantially at the same time.

21. The method of claim 19, wherein the voltage charged in the first capacitor is substantially the same as a value obtained by subtracting the voltage of the second power source from a sum of the voltage of the first power and the threshold voltage of the transistor.

22. The method of claim 19, wherein an absolute value of a value obtained by subtracting the second voltage source from the sum of the data voltage and the threshold voltage of the transistor is established to be greater than an absolute value of the threshold voltage of the transistor.