Method and system for driving a pixel circuit in an active matrix display

• US 8,223,177 B2
• Filed: 07/06/2006
• Issued: 07/17/2012
• Est. Priority Date: 07/06/2005
• Status: Active Grant

• Current Assignee: IGNIS Innovation Incorporated
• Original Assignee: IGNIS Innovation Incorporated
• Inventors: Nathan, Arokia, Jafarabadiashtiani, Shahin, Chaji, G. Reza
• Primary Examiner(s): Shalwala, Bipin
• Assistant Examiner(s): Spar, Ilana
• Application Number:
  US11/481,489
• Publication Number:
  US 20070008253A1
• Time in Patent Office: 2,203 Days
• Field of Search: 345204-206, 345690-693, 345/210, 345214-215, 345 76- 78, 345 82- 83
• US Class Current: 345/691
• 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 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 2320/0223 Compensation for problems related to R-C delay and attenuation in electrodes of matrix panels, e.g. in gate electrodes or on-substrate video signal electrodes
• CPC Class Codes: G09G 2320/0252 Improving the response speed
• CPC Class Codes: G09G 2320/0295 by monitoring each display pixel
• 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

A method and system for driving a pixel circuit in an active matrix display is provided. The system implements a feedback driving scheme to enhance programming speed of the pixel circuit. The system includes a column driver for driving the pixel circuit with feedback. A controller controls a signal on a programming signal line during a programming cycle. For example, the driver may include a model for reducing the settling time of a pixel current. During the programming mode, an accelerating pulse may be provided to accelerate the programming of the pixel circuit.

Claims

1. A system for driving a pixel circuit in an active matrix display, comprising:

a pair of switching transistors for connecting a pixel circuit to a data line and a feedback line during a programming cycle;

a driver for driving the data line during the programming cycle,

a select line connected to the gates of said switching transistors for turning on said switching transistors during said programming cycle and turning off said switching transistors at the end of said programming cycle,

said driver including;

a feedback mechanism for producing a data signal on the data line based on a difference between a feedback signal on the feedback line from the pixel circuit and a programming signal on a programming signal line, and

a controller for enhancing the programming speed of the pixel circuit, the controller providing the programming signal on the programming signal line, the programming signal comprising;

a primary pulse for boosting the charging of a capacitance of the feedback line and a subsequent pulse with programming data to drive the data line based on the data signal during a single programming cycle.

2. A system as claimed in claim 1, wherein the second driver further comprises a module for reducing the settling time of a pixel circuit, the module including a lead compensator coupled between an output of the feedback mechanism and the data line.

3. A system as claimed in claim 2, wherein the feedback mechanism includes a differential amplifier for receiving the programming signal on the programming signal line at a first input and receiving the feedback signal on the feedback line at a second input.

4. A system as claimed in claim 3, wherein the differential amplifier includes an Op-Amp.

5. A system as claimed in claim 3, wherein the differential amplifier includes a trans-conductance differential amplifier.

6. A system as claimed in claim 3, wherein the lead compensator includes a voltage amplifier for amplifying the output of the differential amplifier, and a transistor and a capacitor connected in series between the output of the differential amplifier and the programming signal line.

7. A system as claimed in claim 3, wherein the pixel circuit includes:

a first switching transistor connected to the data line, the data line being connected to the output of the lead compensator; and

a second switching transistor connected to the feedback line, the feedback line being connected to the second input of the differential amplifier,

the first switching transistor and the second switching transistor being selected by a common select signal.

8. A system as claimed in claim 1, wherein the pixel circuit is driven by voltage, current or optical feedback through the second driver.

9. A system as claimed in claim 1, wherein the pixel circuit is a voltage or current programmed pixel circuit.

10. A system as claimed in claim 1, wherein the pixel circuit is arranged in row and column to form the display, the second driver being arranged in each column and being shared by the pixel circuit in the column.

11. A system as claimed in claim 1, wherein the display is an Active-Matrix Organic Light Emitting Diode (AMOLED) display.

18. A system as claimed in claim 6, wherein the transistor includes at least one of amorphous, nano/micro crystalline, poly, organic material, n-type material, p-type material, and CMOS silicon.

19. A system as claimed in claim 1, wherein the pixel circuit includes a plurality of transistors including at least one of amorphous, nano/micro crystalline, poly, organic material, n-type material, p-type material, and CMOS silicon.

12. A method of enhancing the programming speed of a pixel circuit in an active matrix display during a programming cycle, the method comprising:

connecting a pixel circuit to a data line for receiving data and a feedback line for providing a feedback signal from the pixel circuit, said pixel circuit including a pair of switching transistor for connecting the pixel circuit t said data and a feedback lines during a programming cycle;

supplying a select signal to the gates of said switching transistors for turning on said switching transistors during a single programming cycle and turning off said switching transistors at the end of said single programming cycle, and

providing a programming signal on said data line while said switching transistors are turned on, the programming signal comprising a primary pulse for boosting the charging of a capacitance of the feedback line, and a subsequent pulse with programming data to drive the data line based on a difference between the feedback signal on the feedback line and the subsequent pulse.

13. A method as claimed in claim 12, wherein the step of connecting comprises:

setting a select signal to connect the pixel circuit to the data line and the feedback line.

14. A method as claimed in claim 12, further comprising the step of:

after the programming cycle, resetting the select line to disconnect the pixel circuit from the data line and the feedback line.

15. A method as claimed in claim 12, wherein the pixel circuit is arranged in column and row to form a display, a driver for implementing the step of driving being shared by the pixel circuit in each column.

16. A method as claimed in claim 12, wherein the pixel circuit is driven by voltage, current or optical feedback through a driver for implementing the step of driving.

17. A method as claimed in claim 12, wherein the pixel circuit is a voltage or current programmed pixel circuit.

20. A method as claimed in claim 12, wherein the pixel circuit includes a plurality of transistors including at least one of amorphous, nano/micro crystalline, poly, organic material, n-type material, p-type material, and CMOS silicon.

21. A method as claimed in claim 12, wherein the feedback mechanism comprises a

module for reducing the settling time of a pixel circuit, the module includes a lead compensator provided between the output of the feedback mechanism and the data line.

22. A method of driving a pixel circuit in an active matrix display, the pixel circuit including:

a pair of switching transistors for connecting a pixel circuit to a data line and a feedback line during a programming cycle;

a second driver for driving the data line during the programming cycle using a feedback signal on the feedback line and a signal on a programming signal line; and

a select line connected to the gates of said switching transistors for turning on said switching transistors during said programming cycle and turning off said switching transistors at the end of said programming cycle,

the method comprising;

at a first operation in the programming cycle, said driver connecting the pixel circuit to the data line and the feedback line to provide a data signal on the data line to boost the charging of a capacitance of the feedback line; and

at a second operation in the same programming cycle, subsequent to the first operation in the programming cycle, the second driver providing the data signal on the data line based on a difference between a pulse with programming data on the programming signal line and the feedback signal on the feedback line.

23. A method according to claim 22, wherein after the programming cycle, the first driver resetting the select line to disconnect the pixel circuit from the data line and the feedback line.

24. A method according to claim 22, wherein the second driver comprises a feedback mechanism for producing the data signal on the data line based on a difference between the feedback signal on the feedback line from the pixel circuit and the signal on the programming signal line.

25. A method according to claim 24, the feedback mechanism comprising a module for reducing the settling time of a pixel current, the module including a lead compensator provided between an output of the feedback mechanism and the data line.