Method and system for programming and driving active matrix light emitting device pixel having a controllable supply voltage

• US 9,153,172 B2
• Filed: 01/18/2013
• Issued: 10/06/2015
• Est. Priority Date: 12/07/2004
• Status: Active Grant

• Current Assignee: IGNIS Innovation Incorporated
• Original Assignee: IGNIS Innovation Incorporated
• Inventors: Nathan, Arokia, Chaji, Gholamreza, Servati, Peyman
• Primary Examiner(s): Pham, Long D
• Application Number:
  US13/744,843
• Publication Number:
  US 20130162507A1
• Time in Patent Office: 991 Days
• Field of Search: 345/80
• US Class Current: 1/1
• CPC Class Codes: G09G 2300/0465 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 Class Codes: G09G 2300/0842 forming a memory circuit, e.g. a dynamic memory with one capacitor
• CPC Class Codes: G09G 2300/0852 being a dynamic memory with more than one capacitor
• 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 2310/06 Details of flat display driving waveforms
• CPC Class Codes: G09G 2310/061 for resetting or blanking
• 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
• CPC Class Codes: G09G 3/3258 with pixel circuitry controlling the voltage across the light-emitting element
• CPC Class Codes: G09G 3/3696 Generation of voltages supplied to electrode drivers

Abstract

Method and system for programming and driving active matrix light emitting device pixel is provided. The pixel is a voltage programmed pixel circuit, and has a light emitting device, a driving transistor and a storage capacitor. The pixel has a programming cycle having a plurality of operating cycles, and a driving cycle. During the programming cycle, the voltage of the connection between the OLED and the driving transistor is controlled so that the desired gate-source voltage of a driving transistor is stored in a storage capacitor.

Claims

1. A display system, comprising:

a substrate;

a plurality of pixel circuits arranged on the substrate in rows and columns, each of the pixel circuits including a capacitor, a switch transistor connected to a signal line for transferring programming data to be stored in the capacitor as a corresponding voltage, and a driving transistor connected to a light emitting device for emitting light according to the voltage stored in the capacitor, the driving transistor having a terminal connected to a voltage supply line;

a plurality of signal lines on the substrate, each connected to corresponding ones of the pixel circuits;

a plurality of voltage supply lines each arranged on the substrate to intersect perpendicularly the plurality of signal lines; and

a top electrode on the pixel circuits, wherein, in each of the pixel circuits, a gate of the driving transistor is connected directly to the switch transistor, a drain of the driving transistor is connected to a first of the plurality of voltage supply lines, and where, during a programming cycle that includes transferring the programming data from the signal line to the capacitor, the first voltage supply line is adjusted to adjust a voltage of the gate of the driving transistor to cause a gate-source voltage of the driving transistor to be stored in the capacitor as the gate of the driving transistor remains connected to the signal line through the switch transistor.

2. The display system of claim 1, further comprising a driver for driving each of the voltage supply lines to a voltage that is controllable by the driver from a compensation voltage to at least an operating voltage.

3. The display system of claim 2, wherein the compensation voltage is a negative voltage and the operating voltage of the first voltage supply line is a positive voltage.

4. The display system of claim 1, wherein the number of voltage supply lines corresponds to the number of rows of pixel circuits, the voltage supply lines being arranged in rows relative to the substrate.

5. The display system of claim 1, further comprising a plurality of select lines, each connected to a corresponding gate of the switch transistor of each of the pixel circuits, the select lines being arranged on the substrate parallel with the voltage supply lines.

6. The display system of claim 5, wherein the number of select lines corresponds to the number of rows of pixel circuits, the select lines being arranged in rows relative to the substrate, and the signal lines being arranged in columns relative to the voltage supply and select lines.

7. The display system of claim 5, wherein, in each of the pixel circuits, a gate of the switch transistor is connected to a corresponding one of the select lines, a first terminal of the switch transistor is connected to a corresponding one of the signal lines, a second terminal of the switch transistor is connected to a node to which a gate of the driving transistor is connected, the capacitor is coupled to the node, a first terminal of the light emitting device is connected to a second terminal of the driving transistor, a second terminal of the light emitting device is connected to a potential, a first terminal of the driving transistor is connected to a corresponding one of the voltage supply lines.

8. The display system of claim 1, wherein the top electrode is transparent to permit light from each of the light emitting devices in the pixel circuits to pass through the top electrode, each of the light emitting devices being arranged over corresponding ones of the pixel circuits between the substrate and the top electrode.

9. The display system of claim 8, wherein the top electrode is a continuous layer connected to a ground potential.

10. The display system of claim 1, wherein the substrate is transparent to permit light from each of the light emitting devices in the pixel circuits to pass through the substrate, each of the light emitting devices being arranged on the substrate adjacent to corresponding ones of the pixel circuits between the transparent substrate and the top electrode.

11. The display system of claim 1, wherein all of the pixel circuits are fabricated together, and all of the light emitting devices are fabricated together separate from fabrication of the pixel circuits, and each of the light emitting devices is connected to corresponding ones of the drive transistors of the pixel circuits by a via disposed on the substrate.

12. The display system of claim 1, wherein, in each of the pixel circuits, the light emitting device does not overlap the switch transistor or the driving transistor on the substrate.

13. A display system, comprising:

a substrate;

a plurality of pixel circuits arranged on the substrate in rows and columns, each of the pixel circuits including a capacitor, a switch transistor connected to a signal line for transferring programming data to be stored in the capacitor as a corresponding voltage, and a driving transistor connected to a light emitting device for emitting light according to the voltage stored in the capacitor, the driving transistor having a drain terminal connected to a voltage supply line;

a plurality of signal lines on the substrate, each connected to corresponding ones of the pixel circuits;

a plurality of voltage supply lines each arranged on the substrate to intersect perpendicularly the plurality of signal lines; and

a top electrode on the pixel circuits, where, during a programming cycle that includes transferring the programming data from the signal line to a first terminal of the capacitor, a voltage between the light emitting device and the driving transistor is controlled by adjusting the voltage supply line to reset a second terminal of the capacitor while light emitting device remains off and to adjust a gate voltage of the driving transistor.