Differential Sensing Circuit for Touch Noise Compensation
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Solution Overview
Problem
The increasing parasitic capacitance between display electrodes and touch-panel electrodes in modern mobile devices leads to output saturation problems, which existing compensation methods, such as large compensation capacitors or current sources, fail to address effectively, causing noise and interference from display driving signals that affect touch control performance.
Innovation Solution
A sensing circuit with signal compensation using a differential amplifying circuit, comprising a first and second sensing device, and differential compensation to reduce noise and interference, where the differential amplifying circuit generates output signals based on common-mode voltage, first sensing signals, and second sensing signals, effectively canceling common-mode noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If display panels are made thinner to meet market demand, then the form factor is improved, but parasitic capacitance between display electrodes and touch-panel electrodes increases significantly
Solution Approach 1:
The patent converts the harmful parasitic capacitance into a useful compensation signal. By sampling the voltage across the parasitic capacitance during the charging phase and using it to pre-charge or pre-discharge the sensing capacitor during the sensing phase, the previously harmful parasitic effect becomes a beneficial compensation mechanism that eliminates output saturation and improves measurement accuracy.
2Reliability
If large compensation capacitors or voltage are used to solve output saturation, then the saturation problem is addressed, but noise is generated and interference from display driving signals cannot be canceled
Solution Approach 1:
The patent introduces an intermediary compensation mechanism using the parasitic capacitance itself as a compensation element. Instead of adding large external capacitors or voltage sources that generate noise, the system uses the existing parasitic capacitance and its sampled voltage as a mediator to compensate for the saturation effect, thereby eliminating the need for noisy large-signal compensation methods.
Solution Approach 2:
The patent implements a feedback mechanism by sampling the voltage across the parasitic capacitance during the charging phase and feeding this information back to compensate during the sensing phase. This feedback loop allows the system to dynamically adjust for the saturation effect caused by parasitic capacitance without introducing additional noise or interference.
3Reliability
If conventional compensation methods are used, then output saturation is addressed, but touch control performance is affected due to inability to cancel display driving signal interference
Solution Approach 1:
The patent converts the harmful interference from display driving signals into a useful compensation reference. By sampling the voltage across the parasitic capacitance that is coupled to the display electrodes, the system captures the interference signal and uses it to compensate for the saturation effect, thereby transforming the harmful interference into a beneficial reference for improving touch control measurement precision.
Data Source
AI summary
The present invention relates to a sensing circuit with signal compensation, which comprises a first sensing element, a second sensing element and a differential amplifying circuit, the differential amplifying circuit generates an output signal through a differential compensation according to a common mode voltage, a first sensing signal and a second sensing signal. Hereby, reducing the noise of the sensing circuit is achieved, and the interference of the display driving signal may be effectively improved.