Variable Refresh Rate Touch Synchronization via Sub-Frame Scanning
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Solution Overview
Problem
Variable refresh rate displays in touch-sensitive devices complicate synchronization between display functions and touch/stylus sensing functions, leading to performance degradation and frame judder due to mismatch or latency between sensing data and displayed images.
Innovation Solution
Implementing a synchronization scheme that includes time-stamping sensing data, resetting sensing operations, and dividing display frames into sub-frames for touch sensing scans, allowing for synchronization with display operations and reporting data at the conclusion of scans to prevent mismatch or latency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If variable refresh rate is implemented to save power and improve performance, then power consumption is reduced and rendering time is improved, but synchronization between display and sensing functions deteriorates
Solution Approach 1:
The patent applies preliminary action by performing touch sensing scans during the extended blanking period before the display refresh resumes. This allows the sensing operation to be completed in advance, and the results can be reported after the blanking period without causing frame judder or synchronization issues. The sensing scan is performed beforehand while the display is blanked, ensuring that both variable refresh rate benefits and sensing accuracy are maintained.
2Manufacturing precision
If display refresh rate is adjusted to provide sufficient rendering time, then image fidelity is improved, but synchronization between sensing operations and display refresh deteriorates
Solution Approach 1:
The sensing scan is performed in advance during the extended blanking period, before the display refresh resumes. This preliminary sensing action ensures that the sensing data is captured during the available time window, and the results are reported after the blanking period ends, maintaining synchronization with the display frame and preventing frame judder.
Solution Approach 2:
The patent dynamically adjusts the timing of sensing operations based on the variable refresh rate. The sensing scan is flexibly scheduled to occur during the extended blanking period when the display is not refreshing, allowing the system to adapt to different refresh rates while maintaining proper synchronization between sensing and display functions.
3Use of energy by moving object
If extended blanking is used to achieve variable refresh rate, then power consumption is reduced, but frame judder occurs due to mismatch between sensing data timing and display refresh
Solution Approach 1:
The touch sensing scan is performed in advance during the extended blanking period, capturing all necessary sensing data before the display refresh resumes. By completing the sensing operation beforehand, the system ensures that touch response remains smooth and responsive without frame judder, while still benefiting from the power savings of extended blanking.
Data Source
AI summary
Various timing schemes can be used to synchronizing display functions with touch and/or stylus sensing functions for devices including a variable refresh rate (VRR) display. In a continuous-touch mode, for example, extended blanking can result in frame judder due to mismatch or latency between reporting of sensing data and the display. To minimize these issues, sensing operations can reset to re-synchronize with the display operation, and unreported data from sensing scans can be discarded or ignored. In some examples, a display frame can be divided into two sub-frames, and a system can be configured to perform a touch sensing scan during the first sub-frame of a display frame. At the conclusion of extended blanking, the sensing operations can reset to re-synchronize with the display. The touch sensing scan can be completed in one intra-frame pause and can begin at the start of the display frame.