Display driver circuits for organic light emitting diode displays with skipping of blank lines

• US 20050219163A1
• Filed: 04/22/2003
• Published: 10/06/2005
• Est. Priority Date: 04/25/2002
• Status: Active Grant

• Current Assignee: Cambridge Display Technology Limited (Sumitomo Chemical Company Limited)
• Original Assignee: Cambridge Display Technology Limited (Sumitomo Chemical Company Limited)
• Inventors: Smith, Euan C., Routley, Paul R., Goodchild, William
• Granted Patent: US 7,474,288 B2
• Time in Patent Office: Days
• US Class Current: 345/76
• CPC Class Codes: G09G 2310/0213 controlling the sequence of the scanning lines with respect to the patterns to be displayed, e.g. to save power
• CPC Class Codes: G09G 2310/04 Partial updating of the display screen
• CPC Class Codes: G09G 2320/0209 Crosstalk reduction, i.e. to reduce direct or indirect influences of signals directed to a certain pixel of the displayed image on other pixels of said image, inclusive of influences affecting pixels in different frames or fields or sub-images which constitute a same image, e.g. left and right images of a stereoscopic display
• CPC Class Codes: G09G 2330/021 Power management, e.g. power saving
• CPC Class Codes: G09G 2360/18 Use of a frame buffer in a display terminal, inclusive of the display panel
• CPC Class Codes: G09G 3/3216 using a passive matrix

Abstract

Display driver circuits are described for driving organic light-emitting diode displays, particularly passive matrix displays, with greater efficiency. Display driver circuitry includes a frame memory interface for reading data from a frame memory for presentation on a passive matrix OLED display. A blank line identifier identifies one or more substantially blank rows of pixels defined by the data in the frame memory and the control circuitry skips past these rows when the passive matrix display is addressed. When blank lines are skipped the apparent brightness of the remaining lines increases and thus preferably the control circuitry includes a power-controller for reducing a power supply to the display in proportion to the number of skipped lines. The disclosed circuitry is particularly suited to a display driver providing a controlled current drive.

Claims

1. Display driver control circuitry for a passive matrix emissive display, the display comprising a plurality of pixels arranged in rows and columns and addressed by row and column electrodes, the control circuitry being configured to address each row in turn to give the appearance of an image on the display, the control circuitry further comprising:

a frame memory interface for reading data from a frame memory for presentation on the display; and

a blank line identifier for identifying one or more substantially blank rows of pixels defined by said data;

wherein the control circuitry is further configured to skip past said one or more blank rows of pixels during said row addressing.

2. Display driver control circuitry as claimed in claim 1 wherein said control circuitry is further configured to maintain a substantially constant frame rate for the display.

3. Display driver control circuitry as claimed in claim 1 further comprising a control output to provide a control signal for controlling a power supply for the display, said control signal varying dependent upon said identifying of one or more blank rows of pixels.

4. Display driver control circuitry as claimed in claim 1 wherein the control circuitry is further configured to reduce a column drive to said pixels such that a perceived pixel brightness remains substantially constant as the number of said blank rows of pixels varies.

5. Display driver control circuitry as claimed in claim 1 further comprising at least one column output to provide a column output signal for varying a current drive to the display to vary the brightness of a pixel in a column driven by the column output.

6. Display driver control circuitry as claimed in claim 5 farther comprising a reference drive output for determining a reference level of said current drive;

and wherein said reference drive output is dependent upon said blank row identifying.

7. Display driver control circuitry as claimed in claim 5 further comprising power supply control output for controlling the voltage of a power supply for the display.

8. Display driver control circuitry as claimed in claim 7 wherein said control circuitry is configured to control said power supply control output such that said power supply voltage is always just sufficient to provide substantially a maximum required perceived display brightness as determined by said frame memory data.

9. Display driver control circuitry as claimed in claim 7 further comprising switch mode power supply circuitry for said power supply.

10. Display driver control circuitry as claimed in claim 5 further comprising a controllable current generator for providing said current drive to the display.

11. Display driver control circuitry as claimed in claim 1 wherein said blank line identifier is configured to identify said one or more blank rows of pixels using data read from said frame memory.

12. Display driver control circuitry as claimed in claim 1 wherein said blank line identifier is configured to identify said one or more blank rows of pixels by tracking data written to said frame memory.

13. Display driver control circuitry as claimed in claim 1 wherein said control circuitry is further configured to vary a line period during which a row of said display is addressed, dependent upon the brightness of pixels in said row.

14. Display driver control circuitry as claimed in claim 1 further comprising a plurality of column drivers for driving said column electrodes.

15. Display driver control circuitry as claimed in claim 1 further comprising a plurality of row drivers for driving said row electrodes.

16. Display driver control circuitry as claimed in claim 1 further comprising said frame memory.

17. Display driver control circuitry as claimed in claim 1 for an organic light emitting diode-based passive matrix display.

18. Display driver control circuitry for a passive matrix electroluminescent display, the display comprising a plurality of pixels arranged in rows and columns and addressed by row and column electrodes, the control circuitry being configured to address each row in turn to give the appearance of an image on the display, the control circuitry further comprising:

a frame memory interface for reading data from a frame memory for presentation on the display;

a blank line identifier for identifying one or more substantially blank rows of pixels defined by said data;

means to skip past said one or more blank rows of pixels during said row addressing; and

a control output to provide a control signal for controlling a power supply for the display, said control signal varying dependent upon said identifying of one or more blank rows of pixels.

19. Display driver circuitry for driving a matrix of electroluminescent display elements, the display elements being addressed by first and second pluralities of respective first and second electrodes the display driver circuitry comprising:

first display interface circuitry for interfacing to said first electrodes;

second display interface circuitry for interfacing to said second electrodes;

control circuitry coupled to said first display interface circuitry and to said second display interface circuitry and configured to control said first and second display interface circuitry to activate successive sets of said display elements by activating successive ones of said first electrodes in combination with a set of said second electrodes; and

a memory, coupled to said control circuitry, for storing display information for identifying sets of said display elements which are inactive;

wherein said control circuitry is further configured to detect a said inactive set of display elements associated with one of said first electrodes and in response to said detection to activate a subsequent said first electrode without activation of said first electrode associated with said inactive set of elements.

20. Display driver circuitry as claimed in claim 19 further comprising a control output for controlling a power supply for said matrix of display elements, and wherein said control circuitry is further configured to provide a signal on said control output to reduce said power supply in response to said detection.

21. Display driver circuitry as claimed in claim 19 configured for controlling brightness of a said display element by controlling a current supply to the element, and wherein said control circuitry is configured to provide a current control output dependent upon said detection.

22. Display driver circuitry as claimed in claim 19 wherein a frame period is defined by the period between successive activations of the same one of said first electrodes and wherein said control circuitry is configured to provide a substantially, constant frame rate.

23. Display driver circuitry for a pixellated organic light emitting diode display, the display having a plurality of first electrodes and a plurality of second electrodes for driving pixels of the display to luminesce, the display driver circuitry being configured to drive said electrodes to address lines of the display in turn and to detect and skip dark lines.

24. A method of reducing power consumption of a display having a plurality of lines, the method comprising:

reading data for presentation on said display;

detecting one or more lines of said display which when said data is presented would be substantially blank; and

driving the display sequentially with data for said lines, skipping said substantially blank lines.

25. A method as claimed u1claim 24 further comprising controlling a power supply for said display according to how many of said substantially blank lines are detected.

26. A method as claimed in claim 24 wherein the display is a pixellated organic light emitting diode display, and the brightness of a pixel of the display is varied by varying a current to the display, the method further comprising controlling a voltage output of said power supply to be not substantially more than required for a maximum apparent brightness of a displayed pixel.

27. A method as claimed in claim 24, further comprising retiming said displayed lines such that a frame rate of the display is substantially constant.

28. A method as claimed in claim 24 further comprising retiming said displayed lines such that a display period for a line varies according to the brightness of the line.

29. A method of claim 24 wherein said detecting comprises reading said plurality of display lines and counting the substantially blank lines.

30. Processor control code to, when running, implement the method of claim 24.

31. A carrier carrying the processor control code of claim 30