Pixel driver circuit

• US 20070182671A1
• Filed: 09/23/2004
• Published: 08/09/2007
• Est. Priority Date: 09/23/2003
• Status: Active Grant

• Current Assignee: IGNIS Innovation Incorporated
• Original Assignee: IGNIS Innovation Incorporated
• Inventors: Servati, Peyman, Nathan, Arokia, Jafarabadiashtiani, Shahin, Sakariya, Kapil
• Granted Patent: US 8,502,751 B2
• Time in Patent Office: Days
• US Class Current: 345/76
• CPC Class Codes: G09G 2300/0417 Special arrangements specific to the use of low carrier mobility technology
• 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 2320/0646 Modulation of illumination source brightness and image signal correlated to each other
• CPC Class Codes: G09G 3/3241 the current through the light-emitting element being set using a data current provided by the data driver, e.g. by using a two-transistor current mirror
• CPC Class Codes: G09G 3/325 the data current flowing through the driving transistor during a setting phase, e.g. by using a switch for connecting the driving transistor to the data driver
• CPC Class Codes: G09G 3/3266 Details of drivers for scan electrodes
• CPC Class Codes: G09G 3/3283 in which the data driver supplies a variable data current for setting the current through, or the voltage across, the light-emitting elements
• CPC Class Codes: H05B 45/10 Controlling the intensity of the light
• CPC Class Codes: H05B 45/60 Circuit arrangements for operating LEDs comprising organic material, e.g. for operating organic light-emitting diodes [OLED] or polymer light-emitting diodes [PLED]
• CPC Class Codes: Y02B 20/30 Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]

Abstract

A pixel circuit for use in a display comprising a plurality of pixels is provided. The load-balanced current mirror pixel circuit can compensate for device degradation and/or mismatch, and changing environmental factors like temperature and mechanical strain. The pixel circuit comprises a pixel drive circuit comprising, switching circuitry, a current mirror having a reference transistor and a drive transistor, the reference transistor and the drive transistor each having a first and second node and a gate, the gate of the reference transistor being connected to the gate of the drive transistor; and a capacitor connected between the gate of the reference transistor and a ground potential, and a load connected between the current mirror and a ground potential, the load having a first load element and a second load element, the first load element being connected to the first node of the reference transistor and the second load element being connected to the first node of the drive transistor.

Claims

1. A pixel circuit for use in a display comprising a plurality of pixels, the pixel circuit comprising:

a pixel drive circuit comprising;

switching circuitry;

a current mirror having a reference transistor and a drive transistor, the reference transistor and the drive transistor each having a first and second node and a gate, the gate of the reference transistor being connected to the gate of the drive transistor; and

a capacitor connected between the gate of the reference transistor and a ground potential; and

a load connected , between the current mirror and a ground potential, the load having a first load element and a second load element, the first load element being connected to the first node of the reference transistor and the second load element being connected to the first node of the drive transistor.

2. The pixel circuit according to claim 1, wherein the first node of the reference transistor is connected to a first potential and a light emitting diode is connected between the first node of the drive transistor and the ground potential.

3. The pixel circuit according to claim 1, wherein a first light emitting diode is connected between the node of the drive transistor and a ground potential and a second light emitting transistor is connected between the node of the reference transistor and a ground potential.

4. The pixel circuit according to claim 3, wherein the node of the drive transistor and the node of the reference transistor are connected.

5. The pixel circuit according to claim 1, wherein the node of the drive transistor and the node of the reference transistor are connected and a light emitting diode is connected between the node of the drive transistor and a ground potential.

6. The pixel circuit according to claim 1, wherein the switching circuitry comprises:

a feedback transistor having a gate connected to a first select line, a first node connected to a data line and a second node connected to the second node of the reference transistor; and

a switch transistor having a gate connected to a second select line, a first node connected to the data line and a second node connected to the gate of the reference transistor.

7. The pixel circuit according to claim 1, wherein the switching circuitry comprises:

a switch transistor having a gate connected to a first select line, a first node connected to the data line and a second node connected to the gate of the reference transistor; and

a feedback transistor having a gate connected to a second select line, a first node connected to the gate of the reference transistor and a second node connected to the second node of the reference transistor.

8. The pixel circuit according to claim 1, wherein the switching circuitry comprises:

a switch transistor having a gate connected to a first select line, a first node connected to a data line and a second node connected to '"'"'the second node of the reference transistor;

a feedback transistor having a gate connected to a second select line, a first node connected to the second node of the reference transistor and a second node connected to the gate of the reference transistor.

9. The pixel circuit according to claim 1 wherein the transistors are thin film transistors.

10. The pixel circuit according to claim 9 wherein the thin film transistors are amorphous silicon.

11. The pixel circuit according to claim 9 wherein the thin film transistors are polycrystalline silicon.

12. The pixel circuit according to claim 11 wherein the polycrystalline silicon is p-type.

13. The pixel circuit according to claim 9 wherein the thin film transistors are organic.

14. The pixel circuit according to claim 13 wherein the organic is p-type.

15. A pixel circuit for use in a display comprising a plurality of pixels, the pixel circuit comprising:

a pixel drive circuit comprising;

switching circuitry;

a current mirror having a reference transistor and a drive transistor, the reference transistor and the drive transistor each having a first and second node and a gate, the gate of the reference transistor being connected to the gate of the drive transistor, the second node of the reference and drive transistors connected to a ground potential; and

a capacitor connected between the gate of the reference transistor and a ground potential; and

a load connected between the current mirror and a potential.

16. The pixel circuit according to claim 15 wherein, the load comprises a first and second load element connected between the current mirror and the potential.

17. The pixel circuit according to claim 16 wherein the first and second load elements are light emitting diodes.

18. The pixel circuit according to claim 17 wherein the potential is V_DD.

19. The pixel circuit according to claim 16 wherein the first load element is connected to a first potential and the second load element is connected to V_DD.

20. The pixel circuit according to claim 15 wherein the first load element is a transistor having a gate, a first node and a second node, the gate being connected to a third select line, the first node being connected to the second node of the reference transistor and the second node connected to V_DD, the second load element being a light emitting diode connected between the second node of the drive transistor and V_DD.

21. The pixel circuit according to claim 15 wherein the first load element is a transistor having a gate, a first node and a second node, the gate being connected to a third select line, the first node being connected to the second node of the reference transistor and the second node connected to a second potential, the second load element being a light emitting diode connected between the second node of the drive transistor and V_DD.

22. The pixel circuit according to claim 15 wherein the transistors are thin film transistors.

23. The pixel circuit according to claim 22 wherein the thin film transistors are amorphous silicon.

24. The pixel circuit according to claim 22 wherein the thin film transistors are polycrystalline silicon.

25. The pixel circuit according to claim 24 wherein the polycrystalline silicon is p-type.

26. The pixel circuit according to claim 22 wherein the thin film transistors are organic.

27. The pixel circuit according to claim 26 wherein the organic is p-type.