System and method for fast compensation programming of pixels in a display

Patent metadata

Field	Value
Publication number	US-9370075-B2
Application number	US-201213481789-A
Country	US
Kind code	B2
Filing date	May 26, 2012
Priority date	Dec 9, 2008
Publication date	Jun 14, 2016
Grant date	Jun 14, 2016

Abstract

Circuits for programming a circuit with decreased programming time are provided. Such circuits include a storage device such as a capacitor for storing display information and for ensuring a driving device such as a driving transistor drives a light emitting device according to the display information. To increase programming time, the pixel circuits may be pre-charged or a biasing current may be applied to charge and/or discharge a data line and/or the driving device. Aspects of the present disclosure allow for the biasing current to drain partially through the storage device to allow the portion of the biasing current applied to the driving device to remain small while the data line discharges. Furthermore, the present disclosure provides display architectures and operation schemes for display arranged in segments each including a plurality of pixel circuits.

First claim

What is claimed is:

1. A pixel circuit comprising:
a driving transistor for conveying a driving current through a light emitting device during an emission cycle, the driving current being conveyed according to programming information;
a capacitor coupled in series between a gate terminal of the driving transistor and a line conveying compensation signals; and
a switching transistor coupled between the gate terminal of the driving transistor and a terminal of the driving transistor other than the gate terminal,
wherein the capacitor and the driving transistor are coupled via the switching transistor such that while the switching transistor is turned on, a compensation current is conveyed through the driving transistor, the switching transistor, and across the storage capacitor while the gate terminal of the driving transistor adjusts according to the compensation current.

2. The pixel circuit according to claim 1 , wherein the line conveying compensation signals is a line providing a changing voltage having a substantially constant time derivative such that the compensation current generated across the capacitor has a substantially constant value.

3. The pixel circuit according to claim 1 , further comprising:
a second switching transistor connected in series between the gate terminal of the drive transistor and the capacitor such that the gate terminal of the driving transistor is selectively connected to the capacitor, and
a second capacitor coupled to the gate terminal of the driving transistor for being charged according to the programming information during a programming cycle preceding the emission cycle, such that the driving transistor conveys the driving current according to a charge on the second capacitor.

4. The pixel circuit according to claim 3 , wherein the switching transistor is coupled to the gate terminal of the driving transistor through the second switching transistor, the switching transistor being directly connected to the capacitor.

5. The pixel circuit according to claim 4 , wherein the pixel circuit is further configured to reset the capacitor by discharging voltage on the capacitor, via the switching transistor, while the second switching transistor is turned off to thereby isolate the gate terminal of the driving transistor from the capacitor during the reset.

6. The pixel circuit according to claim 5 , wherein the second switching transistor is coupled to a capacitance associated with the light emitting device during the reset, and the discharge of the capacitor is carried out by discharging the capacitor to the capacitance associated with the light emitting device.

7. The pixel circuit according to claim 3 , further comprising a third switching transistor connected in series with the switching transistor and operated according to select line that also operates the switching transistor such that the switching transistor is coupled to the gate terminal of the driving transistor through the third switching transistor, thereby isolating the gate terminal of the driving transistor from the current path through the light emitting device by both the switching transistor and the third switching transistor.

8. The pixel circuit according to claim 3 , wherein the line conveying compensation signals is a data line providing a programming voltage according to the programming information during the programming cycle, and wherein the second switching transistor is operated by a second select line and the switching transistor is operated by a first select line such that the switching transistor and the second switching transistor are both turned on while the compensation current is conveyed through the driving transistor and such that the second switching transistor is turned on and the switching transistor is turned off while the programming voltage is applied to the data line to set the voltage of the gate terminal of the driving transistor based on the programming voltage.

9. The pixel circuit according to claim 8 , further comprising an emission transistor operated according to an emission select line for selectively coupling the driving transistor to the light emitting device during the emission cycle, the emission transistor being configured to prevent the light emitting device from emitting light during the programming cycle or while the gate terminal of the driving transistor adjusts according to the compensation current.

10. The pixel circuit according to claim 1 , wherein the capacitor is a storage capacitor for being charged according to programming information during a programming cycle preceding the emission cycle, such that the driving transistor conveys the driving current according to a charge on the storage capacitor.

11. The pixel circuit according to claim 1 , wherein the calibration current is drained through the capacitor to a current source drawing a reference current, the reference current including the compensation current and a data line discharge current.

12. The pixel circuit according to claim 1 , wherein the line conveying compensation signals is a data line configured to provide:
a programming voltage to charge the capacitor according to the programming information, and
a reference current to simultaneously drain the compensation current through the capacitor and discharge the data line.

13. The pixel circuit according to claim 12 , wherein the data line is further configured to apply a reference voltage during the emission cycle to thereby reference the capacitor to the reference voltage.

14. The pixel circuit according to claim 1 , wherein the line conveying compensation signals is configured to provide a reference current to the capacitor and a terminal of the driving transistor not connected to the switching transistor is connected to a data line configured to provide a programming voltage simultaneously with the reference current such that the programming voltage is conveyed through the drive transistor and the switching transistor to the capacitor simultaneously with the reference current being conveyed through the driving transistor and the switching transistor and across the capacitor.

15. The pixel circuit according to claim 1 , further comprising an emission transistor operated according to an emission select line for selectively coupling the driving transistor to the light emitting device during the emission cycle, the emission transistor being configured to prevent the light emitting device from emitting light during a programming cycle.

16. The pixel circuit according to claim 1 , wherein a first terminal of the capacitor, a first terminal of the switching transistor, and a gate terminal of the driving transistor are connected at a node, the node being charged, during a pre-charge cycle, while the switching transistor is turned on, with a voltage given by the difference of a supply line voltage and a threshold voltage of the driving transistor.

17. The pixel circuit according to claim 1 , wherein the light emitting device is an organic light emitting diode, and wherein the driving transistor is a p-type thin film transistor.

18. A system for driving a display, the system comprising:
a pixel circuit including:
a driving transistor for driving a light emitting device to emit light according to programming information during an emission cycle;
a capacitor coupled in series between a gate terminal of the driving transistor and a line conveying compensation signals; and
a switching transistor coupled between the gate terminal of the driving transistor and a terminal of the driving transistor other than the gat

Assignees

• Chaji Gholamreza
• Lai Jackson Chi Sun
• Azizi Yaser
• Ma Maran Ran
• Nathan Arokia
• Ignis Innovation Inc

Inventors

• Chaji Gholamreza
• Lai Jackson Chi Sun
• Azizi Yaser
• Ma Maran Ran
• Nathan Arokia

Classifications

• G09G2310/0262

  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 title

• G09G3/3233 Primary

  with pixel circuitry controlling the current through the light-emitting element · CPC title

• G09G3/3291

  in which the data driver supplies a variable data voltage for setting the current through, or the voltage across, the light-emitting elements · CPC title

• G09G2300/0465

  Improved aperture ratio, e.g. by size reduction of the pixel circuit, e.g. for improving the pixel density or the maximum displayable luminance or brightness · CPC title

• G09G2330/023

  using energy recovery or conservation · CPC title