Method and apparatus for image based power control of drive circuitry of a display pixel

• US 20070008297A1
• Filed: 04/19/2006
• Published: 01/11/2007
• Est. Priority Date: 04/20/2005
• Status: Abandoned Application

• Current Assignee: Leadin Technology Co., Ltd.
• Original Assignee: Leadin Technology Co., Ltd.
• Inventors: Bassetti, Chester
• Application Number:
  US11/407,785
• Publication Number:
  US 20070008297A1
• Time in Patent Office: Days
• US Class Current: 345/173
• CPC Class Codes: G09G 2300/0842 forming a memory circuit, e.g. a dynamic memory with one capacitor
• CPC Class Codes: G09G 2320/0673 for control of gamma adjustment, e.g. selecting another gamma curve
• CPC Class Codes: G09G 2330/021 Power management, e.g. power saving
• CPC Class Codes: G09G 2360/16 Calculation or use of calculated indices related to luminance levels in display data
• CPC Class Codes: G09G 2360/18 Use of a frame buffer in a display terminal, inclusive of the display panel
• CPC Class Codes: G09G 3/3233 with pixel circuitry controlling the current through the light-emitting element
• 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]
• CPC Class Codes: Y02B 20/30 Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]

Abstract

An apparatus and a method for controllably reducing power and heat dissipated by OLED display circuitry are disclosed. Image dependent drive voltage adjustments are made to reduce the power generated by and the heat dissipated by the OLED pixel circuitry. That extends the life span of the components of the OLED pixel circuitry and maintains their quality by reducing or eliminating the degradation caused by heat. The apparatus and the method of the present invention selectively reduce the voltage level provided to the drain of the transistor used to drive the OLED. The drive transistor'"'"'s drain voltage level is controllably lowered during display intervals that require less than the brightest level of illumination.

Claims

1. A display comprising:

an image including one or more frames to be displayed on the display;

a plurality of pixels for displaying the image frames;

a voltage source for providing a voltage to a light emitting element of a pixel of the plurality of pixels;

a detection circuit for determining the maximum brightness level associated with an image frame; and

a control circuit for adjusting the voltage provided to the light emitting element according to the maximum brightness level determined by the detection circuit.

2. The display of claim 1, wherein the light emitting element includes an organic light emitting diode.

3. The display of claim 1, further comprising:

the voltage source is coupled to the light emitting element by a thin film transistor (TFT).

4. The display of claim 3, wherein the thin film transistor (TFT) provides a current source for the light emitting element.

5. The display of claim 3, wherein the control circuit causes voltage source to provide at least the level of voltage required to cause the thin film transistor to operate in the saturation mode.

6. The display of claim 1, wherein the display includes an active matrix of light emitting elements.

7. The display of claim 1, further comprising:

the pixel including a plurality of sub-pixels;

each of the plurality of sub-pixels including a light emitting element;

the voltage source for providing a voltage to a light emitting element of a sub-pixel of the plurality of sub-pixels; and

a second voltage source for providing a voltage to a light emitting element of another sub-pixel of the plurality of sub-pixels;

wherein,

each sub-pixel is associated with a different color;

the detection circuit for determining the maximum brightness level associated with each sub-pixel; and

the control circuit for adjusting the voltage provided to the light emitting element of each sub-pixel according to the maximum brightness level for each sub-pixel determined by the detection circuit.

8. The display of claim 1, wherein the detection circuit for determining the maximum brightness level and the control circuit for adjusting the voltage provided only for the selected frames of the image.

9. The display of claim 1, wherein the detection circuit for determining the maximum brightness level and the control circuit for adjusting the voltage provided only for the frame of the image that follows a black frame.

13. The display of claim 11, wherein the each of the three sub-pixels is associated with red, blue or green color.

10. A display comprising:

an image including one or more frames for display;

a first row of pixels;

a second row of pixels;

each pixel of the first row of pixels including a set of a plurality of sub-pixels, each of the sub-pixels of the set associated with a different color;

each pixel of the second row of pixels including a set of a plurality of sub-pixels, each of sub-pixels of the set associated with a different color;

a detection circuit for determining the maximum brightness level associated with each color for the first row;

the detection circuit for determining the maximum brightness level associated with each color for the second row; and

a control circuit for adjusting the voltage provided a light emitting elements of each sub-pixel according to the maximum brightness level for each color determined by the detection circuit.

11. The display of claim 10, wherein the display includes an active matrix of organic light emitting diodes.

12. The display of claim 10, wherein the set of the plurality of sub-pixels includes three sub-pixels.

14. A method for a display comprising:

determining the maximum brightness level for a frame of an image to be displayed; and

adjusting the voltage level provided to a pixel of the display according to the determination of the maximum brightness level.

15. The method of claim 14, wherein adjusting the voltage level including lowering the voltage level if the determined maximum brightness level for the frame is less that the determined maximum brightness level of a previous frame.

16. The method claim 14, wherein providing the voltage to the drain of a thin film transistor used for driving a light emitting element of the display.

17. The method of claim 16, wherein providing at least enough voltage level to the drain of the thin film transistor to cause the transistor to operate in the saturation mode.

18. The method of claim 17, wherein providing the voltage to the drain of the thin film transistor to cause the transistor to act as a current source for the light emitting element.

19. The method of claim 14, further comprising:

performing the determining and adjusting steps separately for a plurality of rows of pixels of the display.

20. The method of claim 14, further comprising:

performing the determining and adjusting steps only for selected frames of the image.