Touch Sensing Circuit SNR Enhancement via Differential Comparing Unit
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Solution Overview
Problem
Capacitive touch screens face challenges in accurately detecting touch inputs, particularly in improving the Signal to Noise Ratio (SNR) and accurately identifying small capacitance variations such as hovering, which affects the precision of touch detection.
Innovation Solution
A touch sensing device with a sensing circuit that includes multiple electrodes and output channels, utilizing a comparing unit with capacitors and constant current sources to enhance the SNR by differentiating between self-capacitance and capacitance changes caused by touch inputs, and amplifying signals to improve detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional capacitive touch sensing is used, then the device can detect touch inputs, but the Signal to Noise Ratio (SNR) is insufficient and small capacitance variations cannot be accurately detected
Solution Approach 1:
The sensing circuit divides the electrode array into multiple groups (first group, second group, third group, fourth group) and processes signals from different groups through separate pathways. This segmentation allows independent optimization of each channel and enables differential processing to eliminate common-mode noise, thereby improving SNR and detection accuracy.
Solution Approach 2:
The patent introduces a comparing unit as an intermediary component that receives signals from multiple output channels and performs differential comparison. This comparing unit acts as a mediator to extract genuine touch signals from noise by comparing voltage differences between adjacent electrodes, enhancing the detection of small capacitance variations while suppressing noise.
2Productivity
If multiple output channels are used to sense capacitance variations, then more electrodes can be monitored, but the complexity of the sensing circuit increases
Solution Approach 1:
The patent merges multiple sensing channels into a unified comparing unit that processes signals from first, second, third, and fourth output channels simultaneously. By combining the processing function into a single comparing unit with multiple input nodes, the circuit achieves multi-touch detection capability while avoiding the complexity of having separate processing circuits for each channel.
Solution Approach 2:
The comparing unit is designed as a universal component that can handle signals from multiple output channels through its multiple input nodes. This multi-functional design allows the same comparing unit to process different electrode group signals, enabling scalable multi-touch detection without proportionally increasing circuit complexity.
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
The solution significantly enhances the accuracy of touch detection and small capacitance variation recognition, improving the overall precision of touch input recognition and reducing noise interference.
Implementation Method 1
senses a variation of capacitance of the plurality of electrodes from the plurality of output channels
Data Source
AI summary
Disclosed is a device for sensing touch. The device for sensing touch includes: a plurality of electrodes; and a sensing circuit connected with the plurality of electrodes by a plurality of output channels, which is provided so as to correspond to the plurality of electrodes, respectively, and configured to sense a variation of capacitance of the plurality of electrodes from the plurality of output channels, in which the sensing circuit simultaneously senses output data output from a first output channel, a second output channel, a third output channel, and a fourth output channel among the plurality of output channels, the second output channel is adjacent to the first output channel, and the fourth output channel is adjacent to the third output channel, and the first to fourth output channels are connected to an input terminal of a comparing unit including a first input node and a second input node.