Stable driving scheme for active matrix displays

• US 9,842,544 B2
• Filed: 03/17/2017
• Issued: 12/12/2017
• Est. Priority Date: 04/19/2006
• Status: Active Grant

• Current Assignee: IGNIS Innovation Incorporated
• Original Assignee: IGNIS Innovation Incorporated
• Inventors: Nathan, Arokia, Chaji, Gholamreza
• Primary Examiner(s): Pervan, Michael
• Application Number:
  US15/462,529
• Publication Number:
  US 20170193915A1
• Time in Patent Office: 270 Days
• Field of Search: 3151691-1694, 345 76- 84, 345 87-104, 345204, 345208-210
• CPC Class Codes: G09G 2300/0814 used for selection purposes, e.g. logical AND for partial update
• 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 2300/0866 by means of changes in the pixel supply voltage
• CPC Class Codes: G09G 2310/0254 Control of polarity reversal in general, other than for liquid crystal displays
• CPC Class Codes: G09G 2310/0256 with the purpose of reversing the voltage across a light emitting or modulating element within a pixel
• CPC Class Codes: G09G 2320/0233 Improving the luminance or brightness uniformity across the screen
• CPC Class Codes: G09G 2320/043 Preventing or counteracting the effects of ageing
• CPC Class Codes: G09G 3/3208 organic, e.g. using organic light-emitting diodes [OLED]
• 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

Abstract

A method and system for operating a pixel array having at least one pixel circuit is provided. The method includes repeating an operation cycle defining a frame period for a pixel circuit, including at each frame period, programming the pixel circuit, driving the pixel circuit, and relaxing a stress effect on the pixel circuit, prior to a next frame period. The system includes a pixel array including a plurality of pixel circuits and a plurality of lines for operation of the plurality of pixel circuits. Each of the pixel circuits includes a light emitting device, a storage capacitor, and a drive circuit connected to the light emitting device and the storage capacitor. The system includes a drive for operating the plurality of lines to repeat an operation cycle having a frame period so that each of the operation cycle comprises a programming cycle, a driving cycle and a relaxing cycle for relaxing a stress on a pixel circuit, prior to a next frame period.

Claims

1. A method of operating a pixel array having pixel circuits arranged in rows and columns, each pixel circuit including a drive transistor and a light emitting device, and driven by repeating an operation cycle defining a frame period for each pixel circuit, the method comprising:

setting a data line of a first column at a first voltage;

providing the first voltage to a first pixel circuit in the first column during a first operation cycle of a frame period of the first pixel circuit by activating a first select line coupled to the first pixel circuit; and

providing the first voltage to a second pixel circuit in the first column during a second operation cycle of a frame period of the second pixel circuit which overlaps in time the first operation cycle of the frame period of the first pixel by activating a second select line coupled to the second pixel circuit.

2. The method of claim 1, wherein the first operation cycle comprises a first programming operation cycle and wherein the second operation cycle comprises a first relaxing operation cycle.

3. The method of claim 1, wherein the first voltage is sufficient to cause, during the first operation cycle of the frame period of the first pixel circuit, the drive transistor of the first pixel circuit to turn on and the light emitting device of the first pixel to remain off.

4. The method of claim 1, wherein the first voltage is sufficient to cause, during the second operation cycle of the frame period of the second pixel circuit, the drive transistor of the second pixel circuit to turn off and the light emitting device of the second pixel to turn off.

5. The method of claim 1, wherein the first voltage is sufficient to cause, during the second operation cycle of the frame period of the second pixel circuit, negative biasing of the transistor of the second pixel circuit.

6. The method of claim 1, further comprising:

during the first operation cycle of the frame period of the first pixel circuit,

adjusting a first controllable power supply line for the first pixel circuit to a first supply voltage, the first supply voltage opposite in polarity to that of the first voltage; and

during the second operation cycle of the frame period of the second pixel circuit, adjusting a second controllable power supply line for the second pixel circuit to a second supply voltage, the second supply voltage corresponding to a voltage used to drive the light emitting device of the second pixel circuit.

7. The method of claim 1, further comprising:

setting the data line at a second voltage during a second operation cycle of the frame period of the first pixel circuit, the second voltage comprising at least a programming voltage for the first pixel circuit, and

ensuring the second select line is deactivated during a second operation cycle of the frame period of the first pixel circuit isolating the second pixel circuit from the second voltage.

8. The method of claim 1, further comprising:

deactivating the second select line at the end of the second operation cycle of the frame period of the second pixel circuit.

9. The method of claim 1, wherein the first voltage is smaller than VT0+V_OLED0 where V_T0 is a threshold voltage of the drive transistor of the first pixel circuit in an unstressed state and V_OLED0 is and on voltage of the light-emitting device of the first pixel circuit in an unstressed state.