Frequency Shifting for In-Cell Capacitive Touch and Display Update
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Solution Overview
Problem
Capacitive sensing in integrated displays faces challenges such as signal deterioration due to overlapping update times, leading to lower signal-to-noise ratio and visible artifacts, as the selection and update of pixels interfere with accurate charge measurement of input objects.
Innovation Solution
The method involves synchronizing the phase and frequency of capacitive sensing signals with display signals by driving a first and second capacitive sensing signal with different frequencies, and adjusting the timing of the display signal to maintain synchronization, allowing both capacitive sensing and display updating to occur in parallel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If capacitive sensing and display updating are performed in parallel, then productivity is improved, but measurement precision deteriorates due to signal interference
Solution Approach 1:
The patent implements periodic action by using frequency multiplexing where capacitive sensing signals and display update signals operate at different frequencies. The sensing signal is modulated at a first frequency while the display updates at a second frequency, allowing both operations to occur periodically without continuous interference. This enables parallel operation while maintaining measurement precision through frequency-domain separation.
Solution Approach 2:
The patent applies parameter changes by dynamically adjusting the timing and frequency parameters of the sensing and display signals. The system modifies the phase and frequency of sensing signals relative to display update cycles, and adjusts integration timing to coincide with periods of minimal display interference. This parameter optimization enables simultaneous operation while preserving charge measurement accuracy.
2Reliability
If display update timing is adjusted for synchronization, then reliability is improved, but device complexity increases
Solution Approach 1:
The patent implements feedback mechanisms where the system continuously monitors the synchronization status between sensing and display operations. Timing controllers adjust the phase and frequency of sensing signals based on feedback from display update timing, ensuring stable synchronization. This feedback loop maintains reliable operation while the control logic manages the complexity of coordinated timing.
Data Source
AI summary
Embodiments generally provide a method, input device, and processing system for frequency shifting for synchronized display updating and capacitive sensing. The method includes driving a display signal onto at least one display electrode for updating a display. The method further includes driving a first capacitive sensing signal having a first frequency onto at least one sensor electrode, wherein the first frequency is synchronized to the display signal. The method further includes driving a second capacitive sensing signal having a second frequency onto the at least one sensor electrode, wherein the first and second frequencies differ and a timing of the display signal is adjusted to maintain synchronization with the second frequency, and wherein each capacitive sensing signal and the display signal are driven in parallel for at least some period of time.