Touch Driver Current Subtraction for Higher-SNR Touch Sensing
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Solution Overview
Problem
Existing touch drivers face challenges in maintaining a high signal-to-noise ratio (SNR) due to noise accumulation during differential touch signal processing, which degrades the sensitivity of touch sensors.
Innovation Solution
A touch driver design incorporating current conveyor circuits, common current subtractor circuits, integrator circuits, and analog-to-digital converter circuits to generate and process touch data, effectively reducing noise by subtracting mean currents from individual touch electrode currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If differential profile conversion is used to remove noise from touch signals, then noise removal is achieved, but noise accumulates on the single profile causing SNR degradation
Solution Approach 1:
The patent extracts and removes the common-mode noise component from touch signals by calculating the average of multiple differential profiles and subtracting it from individual profiles. This separates the useful touch signal from the accumulated noise, maintaining high SNR while effectively removing noise.
Solution Approach 2:
Instead of converting multiple differential profiles into a single profile (which causes noise accumulation), the patent maintains multiple separate profile segments and processes them independently. Each profile segment preserves its signal integrity, and the final result is obtained by combining these segmented profiles, preventing noise accumulation.
2Device complexity
If multiple differential profiles are converted into a single profile to simplify processing, then processing complexity is reduced, but noise accumulates and SNR decreases
Solution Approach 1:
The patent implements a dynamic processing approach where the number of profiles to be processed and combined can be adjusted based on touch detection requirements. The system dynamically selects optimal profile combinations and processing depth, maintaining low complexity while preserving SNR by adapting the processing pipeline to actual needs rather than using a fixed single-profile conversion.
3Object-affected harmful factors
If noise profile subtraction is performed on individual touch electrodes, then noise removal is achieved, but the process becomes complex and time-consuming
Solution Approach 1:
The patent performs preliminary noise characterization during idle periods or between touch events by analyzing environmental noise patterns and storing these as reference profiles. When actual touch detection occurs, the pre-computed noise profiles are directly applied for subtraction, eliminating the need for real-time noise analysis and significantly reducing processing time while maintaining effective noise removal.
Data Source
AI summary
A touch driver includes: a plurality of current conveyors connected to a plurality of touch electrodes, the plurality of current conveyor circuits configured to (i) receive a plurality of first currents from the plurality of touch electrodes, and (ii) generate a plurality of second currents having opposite directions to the plurality of first currents; a common current subtractor circuit configured to (i) receive the plurality of first currents and the plurality of second currents from the plurality of current conveyor circuits, and (ii) generate a plurality of output currents that are a sum of (a) a mean current of the plurality of second currents and (b) the plurality of first currents; a plurality of integrator circuits configured to generate a plurality of output voltages by integrating the plurality of output currents; and an analog-to-digital converter configured to convert the plurality of output voltages into digital signals corresponding to touch data.