Pixel circuit for an active matrix organic light-emitting diode display

• US 20050067971A1
• Filed: 09/29/2004
• Published: 03/31/2005
• Est. Priority Date: 09/29/2003
• Status: Active Grant

• Current Assignee: Transpacific Infinity LLC
• Original Assignee: Transpacific IP Group Limited
• Inventors: Kane, Michael Gillis
• Granted Patent: US 7,310,077 B2
• Time in Patent Office: Days
• US Class Current: 315/169.300
• 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 2310/0248 Precharge or discharge of column electrodes before or after applying exact column voltages
• CPC Class Codes: G09G 3/3233 with pixel circuitry controlling the current through the light-emitting element
• 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

Abstract

A pixel circuit for an OLED element comprises first, second, third and fourth transistors wherein controllable conduction paths of the first and second transistors are connected for receiving a data signal current, and the control electrodes thereof are connected for receiving a select signal for being enabled thereby. The third and/or fourth transistors are connected for establishing a current in the OLED element responsive to the data signal current and the select signal. Capacitance may be provided by at least one of the transistors or by additional capacitance.

Claims

1. A pixel circuit for an OLED element comprising:

an OLED element;

first and second transistors of a first polarity, each of said first and second transistors having a controllable conduction path and a control electrode for controlling the conduction of said controllable conduction path,

wherein one end of the controllable conduction paths of said first and second transistors are connected together for receiving a data signal current, and

wherein the control electrodes of said first and second transistors are connected to each other for receiving a select signal for being enabled thereby;

third and fourth transistors each having a controllable conduction path and a control electrode for controlling the conduction of said controllable conduction path, at least one of said third and fourth transistors exhibiting a capacitance between its control electrode and its conduction path,

wherein one end of the controllable conduction paths of said third and fourth transistors are connected together and to an OLED element;

wherein the control electrodes of said third and fourth transistors are connected to each other and to the other end of the controllable conduction path of said first transistor; and

wherein the other end of the controllable conduction path of said third transistor is connected to the other end of the controllable conduction path of said second transistor;

whereby a current is established in the OLED element responsive to the data signal current when said first and second transistors are enabled by the select signal.

2. The pixel circuit of claim 1 further comprising a capacitance coupled between the one end of the controllable conduction path of said fourth transistor and the control electrode thereof.

3. The pixel circuit of claim 1 wherein said third and fourth transistors are of the first polarity.

4. The pixel circuit of claim 1 wherein the one ends of the controllable conduction paths of said third and fourth transistors are connected to the anode of the OLED element, and wherein a cathode of the OLED element and the other end of the controllable conduction path of said fourth transistor are coupled for receiving a potential therebetween.

5. The pixel circuit of claim 1 in combination with a plurality of like pixel circuits as set forth in claim 2-1 arranged in rows and columns to define a display having a plurality of OLED pixel elements.

6. The display of claim 5 further comprising row conductors associated with pixel circuits in each row of said display and column conductors associated with pixel circuits in each column of said display.

7. The display of claim 6 wherein said column conductors apply the data signal current and said row conductors apply the select signal.

8. The pixel circuit of claim 1 embodied in an amorphous-silicon circuit, in a poly-silicon circuit, or in a single-crystal silicon circuit.

16. The pixel circuit of claim 12 in combination with a plurality of like pixel circuits as set forth in claim 2-1 arranged in rows and columns to define a display having a plurality of OLED pixel elements.

17. The display of claim 16 further comprising row conductors associated with pixel circuits in each row of said display and column conductors associated with pixel circuits in each column of said display.

18. The display of claim 17 wherein said column conductors apply the data signal current and said row conductors apply the select signal.

24. The pixel circuit of claim 20 in combination with a plurality of like pixel circuits as set forth in claim 4-1 arranged in rows and columns to define a display having a plurality of OLED pixel elements.

25. The display of claim 24 further comprising row conductors associated with pixel circuits in each row of said display and column conductors associated with pixel circuits in each column of said display.

26. The display of claim 25 wherein said column conductors apply the data signal current and said row conductors apply the select signal.

9. A pixel circuit for an OLED element comprising:

an OLED element;

first and second transistors of a first polarity, each of said first and second transistors having a controllable conduction path and a control electrode for controlling the conduction of said controllable conduction path,

wherein one end of the controllable conduction path of said first transistor is connected for receiving a data signal current, and

wherein the control electrodes of said first and second transistors are connected to each other for receiving a select signal for being enabled thereby;

third and fourth transistors, each of said third and fourth transistors having a controllable conduction path and a control electrode for controlling the conduction of said controllable conduction path, at least said third transistor exhibiting a capacitance between its control electrode and its conduction path,

wherein one end of the controllable conduction paths of said third and fourth transistors are connected together and to one end of the controllable conduction path of said second transistor;

wherein the control electrode of said third transistor is connected to the other end of the controllable conduction path of said first transistor;

wherein the control electrode of said fourth transistor is connected to the control electrodes of said first and second transistors for receiving the select signal for being enabled thereby;

wherein the other end of the controllable conduction path of said fourth transistor is connected to the OLED element; and

wherein the other end of the controllable conduction path of said second transistor is coupled for receiving the data signal current,

whereby a current is established in the OLED element responsive to the data signal current when said first, second and third transistors are enabled by the select signal.

10. The pixel circuit of claim 9 wherein the other end of the controllable conduction path of said second transistor is connected either to the one end or to the other end of the controllable conduction path of said first transistor.

11. The pixel circuit of claim 9 embodied in a poly-silicon circuit or in a single-crystal silicon circuit.

12. A pixel circuit for an OLED element comprising:

an OLED element;

first and second transistors of a first polarity, each of said first and second transistors having a controllable conduction path and a control electrode for controlling the conduction of said controllable conduction path,

wherein one end of the controllable conduction paths of said first and second transistors are connected together for receiving a data signal current, and

wherein the control electrodes of said first and second transistors are connected to each other for receiving a select signal for being enabled thereby;

third and fourth transistors, each of said third and fourth transistors having a controllable conduction path and a control electrode for controlling the conduction of said controllable conduction path, at least said third transistor exhibiting a capacitance between its control electrode and its conduction path,

wherein one end of the controllable conduction paths of said third and fourth transistors are connected together and to the other end of the controllable conduction path of said second transistor;

wherein the control electrode of said third transistor is connected to the other end of the controllable conduction path of said first transistor;

wherein the control electrode of said fourth transistor is connected to the control electrodes of said first and second transistors for receiving the select signal for being enabled thereby; and

wherein the other end of the controllable conduction path of said fourth transistor is connected to the OLED element;

whereby a current is established in the OLED element responsive to the data signal current when said first, second and third transistors are enabled by the select signal.

13. The pixel circuit of claim 12 further comprising a capacitance coupled between the other end of the controllable conduction path of said third transistor and the control electrode thereof.

14. The pixel circuit of claim 12 wherein said third and fourth transistors are of a second polarity opposite to the first polarity.

15. The pixel circuit of claim 12 wherein the other end of the controllable conduction path of said fourth transistor is connected to an anode of the OLED element, and wherein a cathode of the OLED element and the other end of the controllable conduction path of said third transistor are coupled for receiving a potential therebetween.

19. The pixel circuit of claim 12 embodied in a poly-silicon circuit or in a single-crystal silicon circuit.

20. A pixel circuit for an OLED element comprising:

an OLED element;

first and second transistors of a first polarity, each of said first and second transistors having a controllable conduction path and a control electrode for controlling the conduction of said controllable conduction path,

wherein one end of the controllable conduction path of said first transistor is connected for receiving a data signal current,

wherein the other end of the controllable conduction path of said first transistor is connected to one end of the controllable conduction path of said second transistor; and

wherein the control electrodes of said first and second transistors are connected to each other for receiving a select signal for being enabled thereby;

third and fourth transistors, each of said third and fourth transistors having a controllable conduction path and a control electrode for controlling the conduction of said controllable conduction path, at least said third transistor exhibiting a capacitance between its control electrode and its conduction path,

wherein one end of the controllable conduction paths of said third and fourth transistors are connected together and to the other end of the controllable conduction path of said second transistor;

wherein the control electrode of said third transistor is connected to the other end of the controllable conduction path of said first transistor;

wherein the control electrode of said fourth transistor is connected to the control electrodes of said first and second transistors for receiving the select signal for being enabled thereby; and

wherein the other end of the controllable conduction path of said fourth transistor is connected to the OLED element;

whereby a current is established in the OLED element responsive to the data signal current when said first, second and third transistors are enabled by the select signal.

21. The pixel circuit of claim 20 further comprising a capacitance coupled between the other end of the controllable conduction path of said third transistor and the control electrode thereof.

22. The pixel circuit of claim 20 wherein said third and fourth transistors are of a second polarity opposite to the first polarity.

23. The pixel circuit of claim 20 wherein the other end of the controllable conduction paths of said fourth transistor is connected to an anode of the OLED element, and wherein a cathode of the OLED element and the other end of the controllable conduction path of said third transistor are coupled for receiving a potential therebetween.

27. The pixel circuit of claim 20 embodied in a poly-silicon circuit or in a single-crystal silicon circuit.