Touch Sensor Drive Signal Pulse Count for SNR and Power
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Solution Overview
Problem
Existing touch screen technologies face challenges in maintaining a high signal-to-noise ratio (SNR) while operating at desired frame rates and minimizing power consumption, particularly when using active styluses that require a specific number of pulses in drive signals.
Innovation Solution
The approach involves sending drive signals with an increased number of pulses to specific drive lines within a touch window area and a lower number of pulses to other areas, allowing for improved SNR without reducing frame rate or increasing power consumption, and dynamically adjusting the touch window based on object movement predictions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the number of pulses in drive signals is increased to improve SNR, then signal-to-noise ratio improves, but power consumption increases and frame rate decreases
Solution Approach 1:
The patent applies local quality by sending drive signals with different numbers of pulses to different drive lines based on their specific needs. Drive lines within the touch window area receive a first number of pulses (higher for better SNR), while drive lines outside the touch window receive a second number of pulses (lower to save power). This localized differentiation resolves the contradiction by optimizing SNR only where needed rather than uniformly across the entire touch sensor.
Solution Approach 2:
The patent segments the drive lines into two groups: those within the touch window area and those outside it. This segmentation allows independent control of pulse numbers for each group, enabling the system to maintain high SNR in the critical touch detection area while reducing power consumption in non-critical areas, thus resolving the power-SNR tradeoff.
2Measurement precision
If the number of pulses in drive signals is increased to support active stylus operation, then active stylus detection improves, but frame rate decreases
Solution Approach 1:
The patent applies local quality by providing enhanced drive signals (first number of pulses) only to drive lines within the touch window area where active stylus detection is critical, while using reduced drive signals (second number of pulses) for drive lines outside this area. This localized enhancement maintains high frame rates overall while ensuring sufficient pulse count for accurate active stylus detection in the relevant region.
3Measurement precision
If drive signals with uniform high pulse count are sent to all drive lines, then SNR is maximized, but power consumption increases
Solution Approach 1:
The patent implements local quality by differentiating the pulse count in drive signals based on spatial location. Drive lines within the touch window receive a higher number of pulses to maximize SNR where touch detection is needed, while drive lines outside the touch window receive fewer pulses to minimize power consumption in areas where detection is less critical. This resolves the contradiction by applying high SNR optimization locally rather than globally.
Solution Approach 2:
The patent applies partial action by providing the enhanced number of pulses (first number) only partially - specifically to drive lines within the touch window area - rather than excessively applying it to all drive lines. This partial application achieves sufficient SNR in critical areas while avoiding the power consumption penalty of universal high-pulse signaling.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method enhances the SNR ratio, supports active stylus operation, maintains high frame rates, and reduces power consumption, enabling accurate detection of touch and proximity inputs while allowing for error correction and additional sensor metrics.
Implementation Method 1
When an object touches or comes within proximity of the surface of the capacitive touch screen, a change in capacitance may occur within the touch screen at the location of the touch or proximity.
Data Source
AI summary
In one embodiment, a method includes detecting a touch of an object on a device. The method also includes predicting an area of the device that the detected touch will move to. The method further includes sending a first set of drive signals to one or more drive lines within the predicted area, the first set of drive signals each having a first number of pulses. The method further includes sending a second set of drive signals to one or more drive lines outside the predicted area, the second set of drive signals each having a second number of pulses. Furthermore, the first number of pulses is greater than the second number of pulses.