Delta-Sigma Touch Sensing Circuit for More Channels and Less Noise
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Solution Overview
Problem
Existing touch sensing signal processing circuits face challenges in accommodating an increasing number of channels due to increased part requirements, area constraints, and difficulty in routing, while also struggling with high power consumption and signal noise ratio.
Innovation Solution
The implementation of a delta-sigma analog to digital conversion method, combined with a pre-amplification circuit that compares touch sensing signals to touch driving signals and outputs a sensing current, and a delta-sigma ADC that generates a sampling voltage and tunes it using a digital signal, reduces the number of parts and area needed, allowing for more channels and improved signal-to-noise ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the number of channels is increased to accommodate more sensing nodes, then the touch sensing coverage is improved, but the number of parts and mounting area increase
Solution Approach 1:
The patent merges multiple channel processing functions into a single integrated structure. The pre-amplifier and offset capacitance tuning circuit are combined such that the tuning capacitor is shared across multiple channels, reducing the total number of discrete parts. The multiplexer consolidates multiple input signals into a single processing path, allowing multiple sensing nodes to be handled by fewer physical components.
Solution Approach 2:
The offset capacitance tuning circuit is designed to serve multiple channels universally. The same tuning capacitor and control logic are reused across different channels rather than having dedicated tuning circuits for each channel. This multi-functional design reduces the overall part count while maintaining the ability to tune each channel independently.
2Reliability
If the feedback capacitor size is increased to prevent saturation, then the signal processing capability is improved, but the mounting area increases
Solution Approach 1:
The feedback capacitor is integrated into the multiplexer structure rather than being a separate discrete component for each channel. This consolidation allows the feedback capacitor to serve multiple channels while occupying minimal space. The unified design reduces the total mounting area required for signal processing components.
3Measurement precision
If a high-speed sample and hold circuit is used to satisfy the multiplexer requirements, then the conversion accuracy is improved, but the current consumption and chip size increase
Solution Approach 1:
The sample and hold circuit operates periodically rather than continuously, synchronized with the multiplexer switching. This periodic operation allows the circuit to achieve high conversion accuracy only when needed, reducing average current consumption. The circuit holds the sampled value during the conversion process rather than requiring continuous high-speed sampling.
4Measurement precision
If the number of sensing nodes is increased to improve display resolution, then the touch sensing precision is improved, but the device complexity and routing difficulty increase
Solution Approach 1:
The touch sensing panel is divided into multiple sensing nodes arranged in a matrix pattern, with each node independently detectable. This segmentation allows high-resolution touch sensing across the display area while maintaining manageable complexity through systematic organization. The multiplexer sequentially accesses these segmented nodes, reducing the need for complex simultaneous processing circuits.
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 configuration enables a touch sensing signal processing circuit to accommodate a larger number of channels with reduced parts and power consumption, while enhancing signal-to-noise ratio and achieving high-resolution analog-to-digital conversion.
Implementation Method 1
a pre-amplification circuit configured to compare a touch sensing signal corresponding to a change in capacitance of a sensing node for touch sensing and a touch driving signal for driving the touch sensing and to output a sensing current corresponding to a result of the comparison
Implementation Method 2
a delta-sigma analog to digital converter (ADC) configured to generate a sampling voltage obtained by sampling the sensing current, output a digital signal corresponding to the sampling voltage, and tune the sampling voltage by using the digital signal
Data Source
AI summary
The present disclosure discloses a touch sensing signal processing circuit which senses a change in capacitance of a sensing node for touch sensing and provides a logic signal corresponding to the touch sensing. The touch sensing signal processing circuit of the present disclosure is configured using a delta-sigma analog to digital converter. Auto-tuning may be performed by delta-sigma analog conversion.