Pixel circuit and organic light emitting display using the same

• US 20060038754A1
• Filed: 07/20/2005
• Published: 02/23/2006
• Est. Priority Date: 07/28/2004
• Status: Active Grant

• Current Assignee: Samsung Display Company Limited (Samsung Electronics Co. Ltd.)
• Original Assignee: Samsung Mobile Display Company Limited (Samsung Electronics Co. Ltd.)
• Inventors: Kim, Yang Wan
• Granted Patent: US 7,508,365 B2
• Time in Patent Office: Days
• US Class Current: 345/76
• 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 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 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 pixel circuit and an organic light emitting display using the same that decrease crosstalk due to a leakage current in an off-region of a pixel switching device to an undetectable (or invisible) level, and compensate for a variation in threshold voltages within itself to provide for uniform brightness. The pixel circuit includes: a first transistor adapted to supply a current corresponding to a voltage applied to a gate thereof to an organic light emitting device; a second transistor adapted to supply a data voltage to a first electrode of the first transistor in response to a first scan signal; a third transistor adapted to connect a second electrode of the first transistor with the gate of the first transistor; and a capacitor adapted to store a voltage corresponding to the data voltage when the first scan signal is applied to the second transistor, and adapted to supply the stored voltage to the gate of the first transistor for the organic light emitting device to emit light.

Claims

1. A pixel circuit of an organic light emitting display, comprising:

a first transistor adapted to supply a current corresponding to a voltage applied to a gate of the first transistor to an organic light emitting device;

a second transistor adapted to supply a data voltage to a first electrode of the first transistor in response to a first scan signal;

a third transistor adapted to connect a second electrode of the first transistor with the gate of the first transistor; and

a capacitor adapted to store a voltage corresponding to the data voltage when the first scan signal is applied to the second transistor, and adapted to supply the stored voltage to the gate of the first transistor for the organic light emitting device to emit light.

2. The pixel circuit according to claim 1, further comprising a fourth transistor adapted to cut off a pixel voltage from being applied to the first electrode of the first transistor in response to an emission control signal.

3. The pixel circuit according to claim 2, further comprising a fifth transistor adapted to cut off an electrical connection between the second electrode of the first transistor and the organic light emitting device in response to the emission control signal.

4. The pixel circuit according to claim 3, further comprising a sixth transistor adapted to discharge the voltage stored in the capacitor in response to a second scan signal.

5. The pixel circuit according to claim 4, wherein the sixth transistor comprises a first electrode connected to the capacitor, a gate adapted to receive the second scan signal, and a second electrode connected to a scan line for transmitting the second scan signal.

6. The pixel circuit according to claim 5, wherein the first, second, third, fourth, fifth, and sixth transistors are equivalent to each other in a transistor channel type.

7. The pixel circuit according to claim 5, wherein each of the first, second, third, fourth, fifth, and sixth transistors comprises a p-type transistor.

8. The pixel circuit according to claim 5, wherein at least one of the first, second, third, fifth, and sixth transistors is different in a transistor channel type from at least another one of the first, second, third, fifth, and sixth transistors.

9. The pixel circuit according to claim 5, wherein at least one of the first, second, third, fourth, fifth, and sixth transistors comprises a p-type transistor and at least another one of the first, second, third, fourth, fifth, and sixth transistors comprises an n-type transistor.

10. The pixel circuit according to claim 4, wherein the second scan signal and the first scan signal are sequentially transmitted, and the emission control signal is transmitted with a disable level, and wherein the first and second scan signals are shifted to respectively have enable levels.

11. A pixel circuit of an organic light emitting display, comprising:

a first transistor comprising a first electrode adapted to receive a pixel voltage, a second electrode electrically connected to an organic light emitting device, and a gate;

a second transistor comprising a first electrode adapted to receive a data voltage, a second electrode connected to the first electrode of the first transistor, and a gate adapted to receive a first scan signal;

a third transistor connected between the second electrode of the first transistor and the gate of the first transistor, and for allowing the first transistor to function as a diode;

a capacitor comprising a first electrode connected to a power line for supplying the pixel voltage, and a second electrode connected to the gate of the first transistor;

a fourth transistor comprising a first electrode connected to the power line, a second electrode connected to the first electrode of the first transistor, and a gate adapted to receive an emission control signal;

a fifth transistor comprising a first electrode connected to the second electrode of the first transistor, a second electrode connected to an anode of the organic light emitting device, and a gate adapted to receive the emission control signal.

12. The pixel circuit according to claim 11, further comprising a sixth transistor comprising a first electrode connected to the second electrode of the capacitor, a second electrode, and a gate adapted to receive a second scan signal.

13. An organic light emitting display comprising:

a plurality of data lines adapted to transmit a data voltage;

a plurality of scan lines adapted to transmit a scan signal;

a plurality of organic light emitting devices adapted to display an image corresponding to the data voltage; and

a plurality of pixel circuits electrically connected to the data lines, the scan lines, and the organic light emitting devices,

wherein at least one of the pixel circuits comprises;

a first transistor adapted to supply a current to the organic light emitting device;

a second transistor adapted to supply the data voltage to a first electrode of the first transistor in response to a first scan signal;

a third transistor adapted to connect a second electrode of the first transistor with the gate of the first transistor; and

a capacitor adapted to store a voltage corresponding to the data voltage when the first scan signal is applied to the second transistor, and adapted to supply the stored voltage to the gate of the first transistor for the organic light emitting device to emit light.

14. The organic light emitting display according to claim 13, further comprising a fourth transistor adapted to cut off a pixel voltage from being applied to the first electrode of the first transistor in response to an emission control signal.

15. The organic light emitting display according to claim 14, further comprising a fifth transistor adapted to cut off an electrical connection between the second electrode of the first transistor and the organic light emitting device in response to the emission control signal.

16. The organic light emitting display according to claim 15, further comprising a sixth transistor adapted to discharge the voltage stored in the capacitor in response to a second scan signal.

17. The organic light emitting display according to claim 16, wherein the sixth transistor comprises a first electrode connected to the capacitor, a gate adapted to receive the second scan signal, and a second electrode connected to a scan line for transmitting the second scan signal.

18. The organic light emitting display according to claim 17, wherein the second scan signal and the first scan signal are sequentially transmitted, and the emission control signal is transmitted with a disable level, and wherein the first and second scan signals are shifted to respectively have enable levels.

19. The organic light emitting display according to claim 18, further comprising a scan driver adapted to supply the first and second scan signals to at least one of the plurality of scan lines and adapted to supply the emission control signal to an emission control line connected to the fourth transistor and the fifth transistor.

20. The organic light emitting display according to claim 13, further comprising a data driver adapted to supply the data voltage to at least one of the plurality of data lines.