Delay Balancing Loop for Calibration-Free Capacitance Sensing

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Solution Overview

Problem

Existing time and frequency-based capacitance sensing methods are affected by environmental parameters, requiring calibration processes that increase power consumption and chip area, and lack simplicity and ease of setup.

Innovation Solution

A delay balancing loop circuit comprising delay cells, management units, feedback control, and output calculation units, which adjusts delay times to accurately measure capacitance without predetermined calibration, using a closed-loop system with low power consumption and minimal area.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If predetermined calibration signals are used to correct oscillation frequency, then measurement accuracy is improved, but power consumption and chip area increase

Engineering Contradiction:

Improvecapacitance measurement accuracyVSAvoidpower consumption

Core Design Contradiction:

Measurement precisionVSUse of energy by moving object

Solution Approach 1:

The system uses self-service by automatically performing calibration through the feedback control unit that continuously adjusts the reference oscillator frequency to match the sensing oscillator frequency. The delay balancing loop autonomously compensates for environmental variations without requiring external calibration signals or manual intervention, thereby eliminating the need for separate calibration circuits and reducing overall power consumption.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The invention implements a feedback control mechanism where the feedback control unit monitors the frequency difference between the sensing oscillator and reference oscillator, and automatically adjusts the reference oscillator frequency to maintain synchronization. This closed-loop feedback system eliminates the need for predetermined calibration signals while maintaining measurement accuracy, thus reducing power consumption and chip area.

Inventive Principle:

Principle #23Feedback

2Measurement precision

If predetermined calibration signals are used to correct oscillation frequency, then measurement accuracy is improved, but device complexity increases

Engineering Contradiction:

Improvecapacitance measurement accuracyVSAvoidcircuit complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The invention merges the calibration function with the normal measurement operation by integrating the feedback control unit and delay balancing loop into the existing oscillator circuit. The reference oscillator serves dual purposes: as a frequency reference during measurement and as a calibration source. This consolidation eliminates the need for separate calibration circuits and predetermined calibration signals, thereby reducing device complexity while maintaining measurement accuracy.

Inventive Principle:

Principle #5Merging (Combining)

3Ease of manufacture

If two ring oscillators are used in closed-loop system, then calibration process is eliminated, but chip area and power consumption increase

Engineering Contradiction:

Improveease of setupVSAvoidchip area

Core Design Contradiction:

Ease of manufactureVSArea of stationary object

Solution Approach 1:

The reference oscillator is designed to serve multiple functions: it provides the frequency reference for capacitance measurement, acts as a calibration source through the feedback control mechanism, and enables automatic temperature compensation. This multi-functionality eliminates the need for separate calibration circuits and predetermined calibration signals, thereby reducing chip area while maintaining ease of setup and eliminating manual calibration requirements.

Inventive Principle:

Principle #6Universality (Multi-functionality)

4Ease of manufacture

If two ring oscillators are used in closed-loop system, then calibration process is eliminated, but power consumption increases

Engineering Contradiction:

Improveease of setupVSAvoidpower consumption

Core Design Contradiction:

Ease of manufactureVSUse of energy by moving object

Solution Approach 1:

The system achieves self-service by automatically performing frequency calibration through the feedback control unit that continuously monitors and adjusts the reference oscillator frequency. This autonomous operation eliminates the need for external calibration signals and manual setup procedures, thereby simplifying the manufacturing process and reducing power consumption compared to systems requiring separate calibration circuits or periodic calibration operations.

Inventive Principle:

Principle #25Self-service

Data Source

PatentUS20250300646A1Delay balancing loop for measurement of capacitance and delay balancing loop method thereof

Publication Date: 2025.09.25 SILICON CRAFT TECH

AI summary

Delay balancing loop for measurement of capacitance and delay balancing loop method thereof is a circuit design by using time-based capacitance sensing method which leads to low power and small area requiring for Radio Frequency Identification (RFID) products. The circuit includes delay cells for sensing sensor's capacitance and for using as a reference capacitance, delay management unit, feedback control unit and output calculation unit.