Display driver circuits for organic light emitting diode displays with skipping of blank lines, method of reducing power consumption of a display, processor control code to implement the method, and carrier for the control code

• US 8,188,949 B2
• Filed: 12/12/2008
• Issued: 05/29/2012
• Est. Priority Date: 04/25/2002
• Status: Expired due to Fees

• 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
• Primary Examiner(s): Sim, Yong H
• Application Number:
  US12/334,141
• Publication Number:
  US 20090091559A1
• Time in Patent Office: 1,264 Days
• Field of Search: 345/204, 345/76, 345/77, 345 82- 83, 315/169.3
• US Class Current: 345/83
• 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 control circuitry (506) comprises a frame memory interface (505) for reading data from a frame memory (504) for presentation on a passive matrix OLED display. A blank line identifier (507) identifies one or more substantially blank rows of pixels defined by the data in the frame memory and the control circuitry (506) 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 (505) for reducing a power supply to the display in proportion to the number of skipped lines. The invention 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;

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;

column driver circuitry comprising at least one column drive output to provide a column drive and a data input to control said column drive based on said frame memory data; and

an input configured to receive a reference drive output for scaling the controlled column drive,

the control circuitry further comprising said reference drive output, and wherein the reference drive output is configured to vary depending on the number of identified blank rows and to reduce the column drive depending upon the number of identified blank rows of pixels such that a perceived pixel brightness of a plurality of rows remains constant as the number of identified blank rows of pixels varies.

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 further comprising power supply control output for controlling the voltage of a power supply for the display.

5. Display driver control circuitry as claimed in claim 1 further comprising a controllable current generator for providing said current drive to the display.

6. 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.

7. 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.

8. 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.

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

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

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

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

13. Display driver control circuitry as claimed in claim 4 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.

14. Display driver control circuitry as claimed in claim 4 further comprising switch mode power supply circuitry for said power supply.