Capacitive Sensing Circuit With Feedback Clamping for Distortion Control
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Solution Overview
Problem
Conventional capacitive touch sensing technologies face issues such as nonlinear distortion and sensitivity reduction due to external disturbances, requiring additional compensation circuits and consuming significant area, which degrade user experience.
Innovation Solution
A current-type capacitance detection circuit is introduced, utilizing a current mirror circuit, current-differential current-summing circuit, transconductor circuit, and clamping circuit to enhance accuracy and sensitivity by minimizing nonlinear distortion and reducing area consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional capacitive touch sensing technologies are used, then capacitance sensing can be achieved, but nonlinear distortion and sensitivity reduction occur due to external disturbances
Solution Approach 1:
The patent implements a feedback mechanism where the capacitive sensing circuit continuously monitors touch panel capacitance changes and adjusts its operation accordingly. The sensing circuit uses feedback signals to compensate for external disturbances, maintaining measurement precision by dynamically adapting to changing conditions and minimizing nonlinear distortion effects.
Solution Approach 2:
The patent introduces intermediary compensation circuits that act as mediators between the capacitive sensing elements and external disturbances. These intermediary circuits filter and condition signals to reduce the impact of external disturbances while preserving the integrity of the capacitance measurements, thereby improving reliability without sacrificing measurement precision.
2Measurement precision
If additional compensation circuits are added to reduce nonlinear distortion, then measurement precision improves, but device complexity and area consumption increase
Solution Approach 1:
The patent merges the compensation functions directly into the existing capacitive sensing circuit architecture rather than adding separate standalone compensation circuits. By integrating multiple functions into unified circuit blocks, the patent achieves nonlinear distortion reduction while minimizing the increase in device complexity and area consumption.
Solution Approach 2:
The patent designs multi-functional circuit elements that perform both sensing and compensation operations simultaneously. The capacitive sensing circuit is configured to handle multiple tasks including signal acquisition, distortion compensation, and external disturbance rejection within a single integrated structure, reducing overall device complexity while maintaining measurement precision.
3Measurement precision
If additional compensation circuits are added to minimize nonlinear distortion, then measurement precision improves, but area consumption increases
Solution Approach 1:
The patent employs a nested circuit architecture where compensation functions are embedded within the capacitive sensing circuit structure. The compensation circuits are nested inside the main sensing block, sharing common substrates and interconnects, which minimizes the additional area required while achieving nonlinear distortion reduction and improved measurement precision.
Data Source
AI summary
In certain aspects, a capacitive sensing circuit includes a current mirror circuit configured to receive two input current signals associated with two respective capacitance values and send two mirrored current signals, a current-differential current-summing circuit configured to receive the two mirrored current signals from the current mirror circuit and send a current-differential signal and a current-summing signal, a transconductor circuit including a transconductor, and the transconductor circuit is configured to receive the current-differential signal and send a feedback current, and a clamping circuit configured to receive the feedback current and minimize a difference between two voltages of two respective nodes of the current mirror circuit.