System and driving method for light emitting device display

• US 9,877,371 B2
• Filed: 12/02/2013
• Issued: 01/23/2018
• Est. Priority Date: 04/18/2008
• Status: Active Grant

• Current Assignee: IGNIS Innovation Incorporated
• Original Assignee: IGNIS Innovations Inc.
• Inventors: Nathan, Arokia, Chaji, Gholamreza, Alexander, Stefan
• Primary Examiner(s): HORNER, JONATHAN R
• Application Number:
  US14/094,175
• Publication Number:
  US 20140085359A1
• Time in Patent Office: 1,513 Days
• Field of Search: 345698, 345211, 345 55, 345 82- 83
• 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 2300/0819 used for counteracting undesired variations, e.g. feedback or autozeroing
• CPC Class Codes: G09G 2300/0852 being a dynamic memory with more than 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 2310/0262 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 2320/0252 Improving the response speed
• CPC Class Codes: G09G 2320/043 Preventing or counteracting the effects of ageing
• CPC Class Codes: G09G 2320/045 Compensation of drifts in the characteristics of light emitting or modulating elements
• 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 3/3258 with pixel circuitry controlling the voltage across the light-emitting element
• CPC Class Codes: G09G 3/3283 in which the data driver supplies a variable data current for setting the current through, or the voltage across, the light-emitting elements
• 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
• CPC Class Codes: H05B 45/48 having LEDs organised in strings and incorporating parallel shunting devices
• CPC Class Codes: H05B 45/60 Circuit arrangements for operating LEDs comprising organic material, e.g. for operating organic light-emitting diodes [OLED] or polymer light-emitting diodes [PLED]

Abstract

A light emitting device display, its pixel circuit and its driving technique is provided. The pixel includes a light emitting device and a plurality of transistors. A bias current and programming voltage data are provided to the pixel circuit in accordance with a driving scheme so that the current through the driving transistor to the light emitting device is adjusted.

Claims

1. A method of operating a pixel circuit in a programming cycle, during which the pixel circuit receives a programming voltage according to display data, and operating the pixel circuit in a driving cycle different from the programming cycle, during which the pixel circuit emits light according to the programming voltage, the pixel circuit including:

a light emitting device for being driven to emit light during the driving cycle;

a driving transistor having a gate terminal and also having first and second terminals coupled in series with the light emitting device, for driving said light emitting device to emit light during the driving cycle;

a single storage capacitor having first and second terminals, the first terminal of said storage capacitor being coupled to one of said first and second terminals of said driving transistor, and the second terminal of said storage capacitor being coupled to said gate of said driving transistor, for storing a voltage related to the programming voltage during the programming cycle;

a first switch transistor having a gate terminal, a first terminal and a second terminal, the gate terminal of the first switch transistor being coupled to a select line, said first terminal of said first switch transistor being coupled to the first terminal of said storage capacitor, the said second terminal of said first switch transistor being coupled to a first signal line;

a second switch transistor having a gate terminal, a first terminal and a second terminal, said first terminal of said second switch transistor being coupled to said second terminal of said storage capacitor, said second terminal of said second switch transistor being coupled to a second signal line; and

an emission control transistor having a gate terminal, a first terminal and a second terminal, the gate terminal of the emission control transistor being coupled to an emission select line, said second terminal of said emission control transistor being coupled to the second terminal of said storage capacitor, said first terminal of said emission control transistor being coupled to a reference voltage; and

wherein the method comprises;

applying, during the programming cycle while the first and second switch transistors are turned on at the same time while the emission control transistor is turned off, the programming voltage dependent on the display data for said pixel circuit on said signal line; and

enabling, during the driving cycle, an emission mode of the pixel circuit by applying an emission signal on said emission select line so as to turn on the emission control transistor while the first and second switch transistors are turned off.

2. The method of claim 1 wherein the pixel circuit further comprises a third switch transistor having a gate terminal, a first terminal and a second terminal, said first terminal of said third switch transistor being coupled to said first terminal of said storage capacitor and said second terminal of said third switch transistor being coupled to the gate of the driving transistor;

and

wherein the third transistor is turned off during the programming cycle and turned on during the driving cycle.

3. The method of claim 2 wherein, said first terminal of said third switch transistor is coupled to said first terminal of said second switch transistor and said second terminal of said third switch transistor is coupled to said first terminal of said first switch transistor.

4. The method of claim 1 wherein the driving transistor has a first terminal and a second terminal, and

wherein the second terminal of said emission control transistor, coupled to the second terminal of said storage capacitor, is also coupled to one of the first and second terminals of the driving transistor.

5. A method of operating a pixel circuit in a programming cycle and operating the pixel circuit in a driving cycle different from the programming cycle, during which the pixel circuit emits light according to a programming voltage, the pixel circuit including:

a light emitting device for being driven to emit light during the driving cycle;

a driving transistor having a gate terminal and also having first and second terminals coupled in series with the light emitting device, for driving said light emitting device to emit light during the driving cycle;

a storage capacitor having first and second terminals, the first terminal of said storage capacitor being coupled to one of said first and second terminals of said driving transistor, and the second terminal of said storage capacitor being coupled to said gate of said driving transistor, for storing a voltage related to the programming voltage during the programming cycle;

a first switch transistor having a gate terminal, a first terminal and a second terminal, the gate terminal of the first switch transistor being coupled to a select line, said first terminal of said first switch transistor being coupled to the first terminal of said storage capacitor, the said second terminal of said first switch transistor being coupled to a first signal line;

a second switch transistor having a gate terminal, a first terminal and a second terminal, said first terminal of said second switch transistor being coupled to a second signal line and said second terminal of said second switch transistor being coupled to said second terminal of said storage capacitor; and

an emission control transistor having a gate terminal, a first terminal and a second terminal, the gate terminal of the emission control transistor being coupled to an emission select line, said second terminal of said emission control transistor being coupled to the first terminal of said storage capacitor, said first terminal of said emission control transistor being coupled to a reference voltage; and

wherein the method comprises;

applying, during the programming cycle while the first and second switch transistors are turned on at the same time while the emission control transistor is turned off, the programming voltage dependent on the display data for said pixel circuit on said second signal line; and

enabling, during the driving cycle, an emission mode of the pixel circuit by applying an emission signal on the emission select line so as to turn on the emission control transistor while the first and second switch transistors are turned off.

6. The method of claim 5 wherein the pixel circuit further comprises a third switch transistor having a gate terminal, a first terminal and a second terminal, one of said first and second terminals of said third switch transistor being coupled to said first terminal of said storage capacitor and the other of the first and second terminals of said third switch transistor being coupled to the gate of the driving transistor;

and

wherein the third switch transistor is turned off during the programming cycle and turned on during the driving cycle.

7. The method of claim 6 wherein, said first terminal of said third switch transistor is coupled to said first terminal of said second switch transistor and said second terminal of said third switch transistor is coupled to said first terminal of said first switch transistor.

8. The method of claim 5 wherein the driving transistor has a first terminal and a second terminal, and

wherein the one of said first and second terminals of said emission control transistor coupled to the first terminal of said storage capacitor is also coupled to one of the first and second terminals of the driving transistor.

9. A pixel circuit comprising:

a light emitting device for being driven to emit light during the driving cycle;

a driving transistor having a gate terminal and also having first and second terminals coupled in series with the light emitting device, for driving said light emitting device to emit light during the driving cycle;

a single storage capacitor having first and second terminals, the first terminal of said storage capacitor being coupled to one of said first and second terminals of said driving transistor, and the second terminal of said storage capacitor being coupled to said gate of said driving transistor, for storing a voltage related to the programming voltage during the programming cycle;

a first switch transistor having a gate terminal, a first terminal and a second terminal, the gate terminal of the first switch transistor being coupled to a select line, said first terminal of said first switch transistor being coupled to the first terminal of said storage capacitor, said second terminal of said first switch transistor being coupled to a first signal line;

a second switch transistor having a gate terminal, a first terminal and a second terminal, said first terminal of said second switch transistor being coupled to said second terminal of said storage capacitor, said second terminal of said second switch transistor being coupled to a second signal line;

an emission control transistor having a gate terminal, a first terminal and a second terminal, the gate terminal of the emission control transistor being coupled to an emission select line, said second terminal of said emission control transistor being coupled to the second terminal of said storage capacitor, said first terminal of said emission control transistor being coupled to a reference voltage and

a controller configured to operate said pixel circuit in a programming cycle, during which the pixel circuit receives a programming voltage according to display data, and a driving cycle different from the programming cycle, during which the pixel circuit emits light according to the programming voltage,

wherein the pixel circuit is configured to receive the programming voltage dependent on the display data for said pixel circuit on said signal line during the programming cycle while the first and second switch transistors are turned on at the same time while the emission control transistor is turned off; and

wherein the pixel circuit is configured to emit light during the driving cycle wherein an emission signal is applied on an emission select line so as to turn on the emission control transistor while the first and second switch transistors are turned off.

10. The pixel circuit of claim 9 further comprising a third switch transistor having a gate terminal, a first terminal and a second terminal, one of said first and second terminals of said third switch transistor being coupled to said second terminal of said storage capacitor and the other of the first and second terminals of said third switch transistor being coupled to the gate of the driving transistor.

11. The pixel circuit of claim 10 wherein the third switch transistor is turned off during the programming cycle and turned on during the driving cycle.

12. The pixel circuit of claim 9 wherein the driving transistor has a first terminal and a second terminal, and

wherein the one of said first and second terminals of said emission control transistor coupled to the first terminal of said storage capacitor is also coupled to one of the first and second terminals of the driving transistor.