Variable frame refresh rate

• US 9,495,926 B2
• Filed: 12/01/2014
• Issued: 11/15/2016
• Est. Priority Date: 12/01/2014
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Hartley, David A., Tripathi, Brijesh, Holland, Peter F., Spence, Arthur L., Schumacher, Axel B.
• Primary Examiner(s): He, Yingchun
• Application Number:
  US14/557,001
• Publication Number:
  US 20160155399A1
• Time in Patent Office: 715 Days
• Field of Search: None
• US Class Current: 1/1
• CPC Class Codes: G06T 1/20 Processor architectures; Processor configuration, e.g. pipelining
• CPC Class Codes: G06T 1/60 Memory management
• CPC Class Codes: G09G 2320/0266 Reduction of sub-frame artefacts
• CPC Class Codes: G09G 2330/021 Power management, e.g. power saving
• CPC Class Codes: G09G 2340/0435 Change or adaptation of the frame rate of the video stream
• CPC Class Codes: G09G 3/3614 Control of polarity reversal in general
• CPC Class Codes: G09G 3/3696 Generation of voltages supplied to electrode drivers

Abstract

Systems, apparatuses, and methods for preventing charge accumulation on a display panel of a display. A display pipeline is configured to drive a display using a variable frame refresh rate. The display may also be driven by a polarity inversion cadence to alternate the polarity on the display panel on back-to-back frames. In some cases, the frame refresh rate cadence, as specified in frame packets which contain configuration data for processing corresponding frames, can cause a charge accumulation on the display panel if an odd number of frames are displayed at a first frame refresh rate before switching to a second frame refresh rate. Accordingly, in these cases, the display pipeline may override the frame refresh rate setting for a given frame to cause an even number of frames to be displayed at the first frame refresh rate.

Claims

1. A system comprising:

a display device capable of accumulating charge based on a polarity of a displayed frame; and

a display pipeline coupled to the display device, wherein the display pipeline is configured to;

receive a first indication that a current frame refresh rate is changing to a new frame refresh rate for a given frame to be driven to a display device, wherein the new frame refresh rate is different from the current frame refresh rate; and

delay changing the current frame refresh rate for one additional current frame time in response to receiving a second indication that a consecutive number of frames being driven at the current frame refresh rate prior to the given frame is odd.

2. The system as recited in claim 1, wherein a voltage polarity of the display device alternates on consecutive frames.

3. The system as recited in claim 1, wherein the display pipeline is further configured to:

override the new frame refresh rate for the given frame and specify the current frame refresh rate for the given frame; and

specify the new frame refresh rate for one or more frames following the given frame.

4. The system as recited in claim 1, wherein the current frame refresh rate is greater than the new frame refresh rate.

5. The system as recited in claim 4, wherein a period of the new frame refresh rate is an integer multiple of a period of the current frame refresh rate.

6. The system as recited in claim 1, wherein the display pipeline is further configured to repeat a previous frame at the current frame refresh rate and delay the given frame so that the given frame is displayed at the new frame refresh rate.

7. The system as recited in claim 1, wherein the display device comprises a liquid crystal display (LCD).

8. A computing system comprising:

a memory configured to store frame data;

a display device; and

a display pipeline configured to;

receive a first indication that a current frame refresh rate is changing to a new frame refresh rate for a given frame to be driven to the display device, wherein the new frame refresh rate is different from the current frame refresh rate; and

delay changing the current frame refresh rate for one additional current frame time in response to receiving a second indication that a consecutive number of frames being driven at the current frame refresh rate prior to the given frame is odd.

9. The computing system as recited in claim 8, wherein a voltage polarity of the display device alternates on consecutive frames.

10. The computing system as recited in claim 8, wherein the display pipeline is further configured to:

override the new frame refresh rate for the given frame and specify the current frame refresh rate for the given frame; and

specify the new frame refresh rate for one or more frames following the given frame.

11. The computing system as recited in claim 8, wherein the current frame refresh rate is greater than the new frame refresh rate.

12. The computing system as recited in claim 11, wherein a period of the new frame refresh rate is an integer multiple of a period of the current frame refresh rate.

13. The computing system as recited in claim 8, wherein the display pipeline is further configured to repeat a previous frame at the current frame refresh rate and delay the given frame so that the given frame is displayed at the new frame refresh rate.

14. The computing system as recited in claim 8, wherein the display device is a liquid crystal display (LCD).

15. A method comprising:

receiving, at a display pipeline, a first indication that a current frame refresh rate is changing to a new frame refresh rate for a given frame to be driven to a display device, wherein the new frame refresh rate is different from the current frame refresh rate; and

delaying changing the current frame refresh rate for one additional current frame time in response to receiving a second indication that a consecutive number of frames being driven at the current frame refresh rate prior to the given frame is odd.

16. The method as recited in claim 15, wherein a voltage polarity of the display device alternates on consecutive frames.

17. The method as recited in claim 15, further comprising:

overriding the new frame refresh rate for the given frame and specify the current frame refresh rate for the given frame; and

specifying the new frame refresh rate for one or more frames following the given frame.

18. The method as recited in claim 15, wherein the current frame refresh rate is greater than the new frame refresh rate.

19. The method as recited in claim 18, wherein a period of the new frame refresh rate is an integer multiple of a period of the current frame refresh rate.

20. The method as recited in claim 15, wherein the display device is a liquid crystal display (LCD).