Sigma-Delta Capacitance Converter for Dynamic Tracking and Resolution
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Solution Overview
Problem
Conventional capacitance sensing methods, such as charge accumulation and sigma-delta modulators, face limitations in tracking dynamic capacitance changes and providing flexible conversion time, leading to reduced accuracy and inability to simultaneously process high-resolution absolute values and fast capacitance changes.
Innovation Solution
A sigma-delta modulator-based system that continuously adjusts conversion time versus resolution, allowing for simultaneous processing of fast capacitance changes and high-precision measurements, using a switching capacitor in a feedback loop without an external switching signal generator and without an operational amplifier or separate comparator, enabling one-wire configuration for sensing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional charge accumulation or sigma-delta modulator methods are used, then capacitance sensing is achieved, but the system cannot simultaneously track dynamic capacitance changes and provide high-resolution absolute values with flexible conversion time
Solution Approach 1:
The patent implements a dynamic system where the sigma-delta modulator continuously adapts its operation based on real-time capacitance changes. The system transitions from static conversion cycles to dynamic modulation, allowing the conversion time and resolution to be flexibly adjusted according to the rate of capacitance change, thereby simultaneously achieving high measurement precision and adaptability to dynamic conditions
Solution Approach 2:
The system changes operational parameters (conversion time, sampling rate, modulation frequency) based on the detected capacitance dynamics. By varying these parameters in real-time, the system optimizes the balance between measurement resolution and tracking speed, enabling flexible adaptation to different sensing scenarios without sacrificing precision
2Measurement precision
If conventional capacitance sensing circuits with external switching signal generators and operational amplifiers are used, then capacitance measurement is achieved, but device complexity increases
Solution Approach 1:
The patent merges multiple separate components (switching signal generator, operational amplifier, comparator) into an integrated sigma-delta modulator circuit. This consolidation maintains the necessary signal conditioning and switching functions while reducing the number of external components, thereby simplifying the overall device architecture without compromising measurement precision
Solution Approach 2:
The sigma-delta modulator is designed to perform multiple functions simultaneously: it acts as the switching signal generator, the operational amplifier, and the comparator. This multi-functional design eliminates the need for separate dedicated components for each function, reducing device complexity while preserving measurement accuracy
3Reliability
If conventional capacitance sensing methods are used, then capacitance detection is achieved, but noise immunity is reduced
Solution Approach 1:
The patent implements a feedback mechanism within the sigma-delta modulator that continuously monitors the capacitance signal and adjusts the modulation process to compensate for noise. This feedback loop enhances noise immunity by filtering out high-frequency noise components while preserving the underlying capacitance information, thereby maintaining measurement precision even in noisy environments
Data Source
AI summary
Apparatuses and methods of converting a capacitance measured on a sense element to a digital value are described. One apparatus includes a modulator having a modulator capacitor, a sense element selectively coupled in a feedback loop of the modulator to operate as a switching capacitor. The apparatus also includes a first switch coupled between a voltage source and a first node of the switching capacitor and a second switch coupled between the first node of the switching capacitor and a first node of the modulator capacitor. The switching capacitor provides a charge current to the modulator capacitor via the second switch. The modulator measures a capacitance of the sense element and converts the measured capacitance to a digital code representing the capacitance.