Sensing Circuit With AC Feedback for High-Impedance Transducers

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Solution Overview

Problem

Transducers with high impedance requirements face challenges in maintaining optimal impedance levels when voltage exceeds a threshold, leading to signal distortion and undesired operational modes, particularly in amplifying circuits used for sensing systems like microphones and vibration sensors.

Innovation Solution

The proposed solution involves an impedance element connected to a predetermined voltage, switching between high and low impedance based on voltage thresholds, combined with a filter circuit that blocks DC signals while transferring AC signals, ensuring negative amplification and maintaining high impedance within a predetermined voltage range to prevent signal distortion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the voltage over the impedance element exceeds the threshold voltage, then the impedance decreases to a lower value, but this causes signal distortion and undesired operational modes in the transducer

Engineering Contradiction:

Improvetransducer operationVSAvoidsignal distortion

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The amplifier with negative gain is configured to preemptively counteract voltage excursions that would cause the impedance element to switch from high to low impedance state. By providing negative amplification with absolute value ≥ V1/Vth, the amplifier prevents the voltage over the impedance element from exceeding the threshold voltage, thereby preventing signal distortion before it occurs

Inventive Principle:

Principle #9Preliminary anti-action

Solution Approach 2:

The circuit employs feedback through the amplifier connected between the first and second output terminals. The amplifier monitors the voltage conditions and adjusts its output to maintain the voltage over the impedance element below the threshold voltage, creating a self-regulating system that prevents harmful impedance switching

Inventive Principle:

Principle #23Feedback

2Reliability

If the amplifier has high negative amplification to prevent impedance switching, then signal distortion is reduced, but the circuit complexity increases

Engineering Contradiction:

Improveimpedance stabilityVSAvoidamplifier configuration

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The amplifier is configured to perform multiple functions simultaneously: it provides signal amplification, maintains impedance stability through negative feedback, and prevents threshold voltage excursions. This multi-functionality is achieved by connecting the amplifier between the two output terminals with a gain configured to maintain voltage over the impedance element below the threshold

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The circuit merges the impedance control function with the signal amplification function into a single amplifier stage. Rather than using separate circuits for impedance control and signal processing, the invention combines these functions, reducing overall circuit complexity while maintaining reliability

Inventive Principle:

Principle #5Merging (Combining)

3Measurement precision

If the impedance element maintains high impedance to prevent signal distortion, then transducer performance is improved, but the voltage range for optimal operation is limited

Engineering Contradiction:

Improvesignal accuracyVSAvoidvoltage range

Core Design Contradiction:

Measurement precisionVSAdaptability or versatility

Solution Approach 1:

The circuit dynamically maintains the impedance element in its high impedance state through active feedback control. The amplifier continuously adjusts its output to ensure the voltage over the impedance element remains below the threshold voltage, allowing the circuit to adapt to varying signal conditions while maintaining optimal impedance

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The amplifier gain is specifically configured with negative amplification where the absolute value is ≥ V1/Vth. This parameter setting ensures that the voltage over the impedance element stays below the threshold voltage, maintaining high impedance state and optimal transducer performance across the operating range

Inventive Principle:

Principle #35Parameter changes

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 effectively reduces signal distortion and maintains high impedance within the desired voltage range, allowing for accurate signal amplification and transmission without compromising the transducer's operation, even at high signal values.

Implementation Method 1

a filter circuit blocking DC but transferring AC, the circuit connected to the amplifier output configured to feed an AC signal to the second output terminal

Methodology Applied

Scientific EffectDC blocking: Capacitance

Implementation Method 2

the impedance element having: a first impedance, when a voltage over the impedance element is below a threshold voltage and a second impedance, lower than the first impedance, when a voltage over the impedance element exceeds the threshold voltage

Methodology Applied

Scientific EffectVoltage-dependent impedance switching: Diode

Data Source

PatentUS10656006B2Sensing circuit comprising an amplifying circuit and an amplifying circuit

Publication Date: 2020.05.19 SONION NEDERLAND BV

AI summary

A sensing system with an AC feedback to the non-signal and non-biased terminal of the transducer. An impedance element, such as two anti-parallel diodes, are provided at the amplifier input, and the amplifier gain is negative and has a size sufficient to ensure that the input on the one terminal does not exceed the forward voltage of the diode.