Sigma-Delta Capacitance Conversion with Feedback Switching Capacitor

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Solution Overview

Problem

Conventional capacitance sensing methods, such as charge-accumulation circuits, face limitations in tracking dynamic capacitance changes and require multiple stages (reset, integrate, measure) which reduces accuracy and flexibility, and are not suitable for single-wire configurations or dynamic full-scale range adjustments.

Innovation Solution

A sigma-delta modulator-based system that continuously converts capacitance to a digital code, using a switching capacitor in a feedback loop without an external switching signal generator, allowing adjustments in conversion time and enabling simultaneous tracking of fast capacitance changes and high-precision measurements.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If conventional charge-accumulation circuits are used for capacitance sensing, then the measurement process can be completed, but the system requires multiple stages (reset, integrate, measure) which reduces accuracy and flexibility

Engineering Contradiction:

Improvecapacitance measurement accuracyVSAvoidmulti-stage circuit structure

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent combines the reset, integrate, and measure stages into a single continuous sigma-delta modulation process. The modulator continuously converts capacitance to digital code without discrete stage transitions, eliminating the accuracy losses and flexibility limitations inherent in multi-stage architectures while maintaining complete measurement functionality.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The sigma-delta modulator operates continuously rather than in discrete stages, providing ongoing capacitance conversion and tracking. This continuous operation enables the system to adapt measurement parameters dynamically and track capacitance changes in real-time, improving both accuracy and flexibility compared to sequential stage-based approaches.

Inventive Principle:

Principle #20Continuity of useful action

2Speed

If conventional capacitance sensing methods are used, then basic measurement can be achieved, but the system cannot track dynamic capacitance changes effectively

Engineering Contradiction:

Improvedynamic capacitance tracking speedVSAvoidcapacitance measurement accuracy

Core Design Contradiction:

SpeedVSMeasurement precision

Solution Approach 1:

The patent implements a dynamic measurement system where the sigma-delta modulator continuously adapts to changing capacitance values. The system can adjust measurement parameters on-the-fly and track capacitance variations in real-time, simultaneously maintaining high speed response and measurement precision that static multi-stage circuits cannot achieve.

Inventive Principle:

Principle #15Dynamics

3Adaptability or versatility

If conventional methods are used, then capacitance measurement can be performed, but the system requires external switching signal generators and cannot support single-wire configurations

Engineering Contradiction:

Improvesingle-wire configuration capabilityVSAvoidexternal switching signal generator requirement

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The sigma-delta modulator generates its own switching signals internally, eliminating the need for external switching signal generators. This self-contained operation enables single-wire configurations where the same line can both excite the capacitor and sense the capacitance, significantly improving system adaptability and reducing external component requirements.

Inventive Principle:

Principle #25Self-service

4Adaptability or versatility

If conventional charge-accumulation circuits are used, then capacitance measurement can be completed, but the conversion time cannot be adjusted flexibly

Engineering Contradiction:

Improveconversion time adjustabilityVSAvoidmeasurement conversion time

Core Design Contradiction:

Adaptability or versatilityVSLoss of time

Solution Approach 1:

The sigma-delta modulator allows dynamic adjustment of conversion time and measurement parameters during operation. The continuous modulation process can be configured with different sampling rates and integration periods, enabling flexible conversion time adaptation without the fixed timing constraints of conventional multi-stage charge-accumulation circuits.

Inventive Principle:

Principle #15Dynamics

Data Source

PatentUS8547114B2Capacitance to code converter with sigma-delta modulator

Publication Date: 2013.10.01 INFINEON TECHNOLOGIES AMERICAS CORP

AI summary

An apparatus and method for converting a capacitance measured on a sensor element to a digital code. The apparatus may include a switching capacitor as a sensor element of a sensing device, and a sigma-delta modulator coupled to the sensor element to convert a capacitance measured on the sensor element to a digital code. The switching capacitor is in a feedback loop of the sigma-delta modulator. The method may include measuring a capacitance on a sensor element of a sensing device using a sigma-delta modulator, and converting the capacitance measured on the sensor element to a digital code.