Variable refresh rate display synchronization

Patent metadata

Field	Value
Publication number	US-10019968-B2
Application number	US-201615271085-A
Country	US
Kind code	B2
Filing date	Sep 20, 2016
Priority date	Dec 31, 2015
Publication date	Jul 10, 2018
Grant date	Jul 10, 2018

Abstract

Systems and methods for synchronizing a video source and display circuitry using a dynamic tearing effect (TE) signal are provided. In one embodiment, an electronic display device includes: variable refresh rate circuitry that, when no new frame data is provided to the electronic display device, extends a vertical blanking period and reduces a refresh rate of the electronic display device. A tearing effect signal is generated, which is selectively set to a first logical level at a first period of time and a second logical level at a second period of time. The tearing effect signal is provided to the host electronic device that provides frame data to the electronic display device and upon receipt of new frame data, an un-extended vertical blanking period is returned to and the frame data at the next frame boundary is displayed.

First claim

We claim:

1. An electronic device with a display, comprising:
variable refresh rate circuitry that enables the display to refresh a display panel at variable rates, the variable refresh rate circuitry configured to: when no new frame data is provided to the display, extend a vertical blanking period and reduce a refresh rate of the display until receipt of new frame data; and
tearing effect correction circuitry that reduces artifacts caused by reading part of a first frame and part of a second frame onto the display at a common time, the tearing effect correction circuitry configured to:
generate a tearing effect signal that indicates when data is permitted to be provided to the display from a source of video data, wherein the tearing effect signal is selectively set to a first logical level at a first period of time and a second logical level at a second period of time, wherein the tearing effect signal accounts for extension of the vertical blanking period, by transitioning between the first logical level and the second logical level based on the vertical blanking period;
provide the tearing effect signal to the source of the video data that provides frame data to the electronic device; and
upon the receipt of the new frame data, return to an un-extended vertical blanking period and display the frame data at the next frame boundary.

2. The electronic device of claim 1 , wherein:
the tearing effect signal indicates that data is not permitted to be provided to the display when set to LOW; and
the tearing effect signal indicates that data is permitted to be provided to the display when set to HIGH.

3. The electronic device of claim 1 , wherein:
the tearing effect signal is set to the first logical level when scanning operations are performed by the electronic device and set to the second logical level when scanning operations are not being performed on the electronic device.

4. The electronic device of claim 3 , wherein data read operations are implemented by the electronic device when the scanning operations are performed.

5. The electronic device of claim 1 , wherein:
the tearing effect signal that is set to the first logical level and the second logical level based upon corresponding first logical level and second logical level settings of a vertical blanking signal indicative of the vertical blanking period.

6. The electronic device of claim 5 , wherein:
the tearing effect signal comprises a leading offset with respect to the vertical blanking signal.

7. The electronic device of claim 5 , wherein:
the tearing effect signal comprises a lagging offset with respect to the vertical blanking signal.

8. The electronic device of claim 5 , wherein:
when the vertical blanking period is extended, a frame sync signal is incorporated into the tearing effect signal, providing a plurality of rising edges in the tearing effect signal during the vertical blanking period that is extended.

9. The electronic device of claim 8 , wherein the frame sync signal comprises a 240 Hz frame sync signal.

10. A method of operating an electronic device with a display, comprising:
when no new frame data is provided to the display, extending a vertical blanking period and reducing a refresh rate of the electronic device until receipt of new frame data;
generating a tearing effect signal that is selectively set to a first logical level at a first period of time and a second logical level at a second period of time, wherein the tearing effect signal accounts for extension of the vertical blanking period, by transitioning between the first logical level and the second logical level based on the vertical blanking period, wherein the tearing effect signal provides an indication that data may be provided from a host electronic device, which sources video data, to the display whenever the tearing effect signal is set to the second logical level;
providing the tearing effect signal to the host electronic device that provides frame data to the display;
receiving the new data from the host electronic device based upon the tearing effect signal provided to the host electronic device; and
upon the receipt of the new frame data, returning to an un-extended vertical blanking period and displaying the frame data at the next frame boundary.

11. The method of claim 10 , further comprising:
setting the tearing effect signal to the first logical level when scanning operations are performed by the display; and
setting to the second logical level when scanning operations are not being performed on the display.

12. The method of claim 11 , further comprising:
implementing data read operations when the scanning operations are performed.

13. The method of claim 11 , further comprising:
providing the tearing effect signal via a timing controller of the electronic device.

14. The method of claim 10 , further comprising:
setting the tearing effect signal to the first logical level and the second logical level based upon a vertical blanking signal indicative of the vertical blanking period.

15. The method of claim 14 , further comprising:
implementing a data write operation when the tearing effect signal is set to the second logical level, but not the first logical level.

16. The method of claim 14 , further comprising:
setting the tearing effect signal by mirroring the vertical blanking signal.

17. A tangible, non-transitory, machine-readable storage medium storing one or more programs that are executable by one or more processors of an electronic device with a display, the one or more programs including instructions to:
when no new frame data is provided to the display, extend a vertical blanking period and reduce a refresh rate of the display until receipt of new frame data;
generate a tearing effect signal that is selectively set to a first logical level at a first period of time and a second logical level at a second period of time, wherein the tearing effect signal provides an indication that data may be provided from a host electronic device to the display whenever the tearing effect signal is set to the second logical level, wherein the tearing effect signal accounts for extension of the vertical blanking period, by transitioning between the first logical level and the second logical level based on the vertical blanking period;
provide the tearing effect signal to the host electronic device that provides frame data to the display;
receive the new data from the host electronic device based upon the tearing effect signal provided to the host electronic device; and
upon the receipt of the new frame data, return to an un-extended vertical blanking period and displaying the frame data at next frame boundary.

18. The machine-readable storage medium of claim 17 , further comprising instructions to:
set the tearing effect signal to the first logical level when scanning operations are performed by the display; and
set to the second logical level when scanning operations are not being performed on the display.

19. The machine-readable storage medium of claim 17 , further comprising instructions to:
set the tearing effect signal to either the first logical level or the second logical level, by mirroring a vertical blanking signal indicative of the vertical blanking period.

20. The machine-readable storage medium of claim 17 , further comprising instructions to:
perform data write operations when the tearing effect signal is set to the second logical level, but not the first logical level.

Assignees

• Apple Inc

Inventors

• Bi Yafei
• Spence Arthur L
• Heppolette Vanessa C
• Tamari Eran
• Decesare Josh P

Classifications

• G09G5/18

  Timing circuits for raster scan displays (specially adapted for television H04N {; synchronisation between the display unit and other display units, videodisc player G09G5/12}) · CPC title

• G09G5/39 Primary

  Control of the bit-mapped memory · CPC title

• G09G2310/04

  Partial updating of the display screen · CPC title

• G09G5/001

  Arbitration of resources in a display system, e.g. control of access to frame buffer by video controller and/or main processor · CPC title

• G09G2360/18

  Use of a frame buffer in a display terminal, inclusive of the display panel · CPC title