Infrared Diode Detector Feedback Circuit for Higher Sensitivity

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Solution Overview

Problem

Conventional infrared detecting devices require increasing the number of diodes in series to enhance detection sensitivity, leading to increased size and power consumption.

Innovation Solution

Incorporation of a positive feedback circuit and current mirror circuit to enhance detection sensitivity without increasing the number of diodes, utilizing a series-connected diode configuration with a feedback loop to amplify voltage and current changes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If the number of diodes connected in series is increased to enhance detection sensitivity, then the detection sensitivity is improved, but the device size and power supply voltage requirements increase

Engineering Contradiction:

Improvedetection sensitivityVSAvoiddevice size

Core Design Contradiction:

Measurement precisionVSLength of stationary object

Solution Approach 1:

A feedback circuit is introduced that senses the voltage across the diode string and applies feedback voltage to adjust the current through the diodes. This feedback mechanism allows the system to achieve enhanced detection sensitivity without simply increasing the number of diodes, as the feedback amplifies the effective signal response from the existing diode configuration.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The invention changes the electrical parameters (current and voltage) through active circuit control rather than changing the physical configuration (number of diodes). By adjusting the bias current and utilizing voltage amplification circuits, the system achieves higher sensitivity with the same number of diodes, thereby avoiding size increase.

Inventive Principle:

Principle #35Parameter changes

2Measurement precision

If the number of diodes connected in series is increased to enhance detection sensitivity, then the detection sensitivity is improved, but the power supply voltage requirement increases

Engineering Contradiction:

Improvedetection sensitivityVSAvoidpower supply voltage

Core Design Contradiction:

Measurement precisionVSUse of energy by moving object

Solution Approach 1:

The feedback circuit regulates the current through the diode string by sensing the voltage and adjusting the current accordingly. This allows the system to maintain optimal operating conditions with lower power supply voltage, as the feedback ensures efficient utilization of the available voltage rather than requiring higher voltage to achieve the same sensitivity.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The invention replaces the mechanical approach of adding more diodes (physical configuration change) with an electrical approach using active circuits (current control and voltage amplification). This substitution allows achieving the same sensitivity enhancement effect without the proportional increase in power supply voltage that would be required by simply adding more diodes in series.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Measurement precision

If more diodes are arranged in the temperature sensing portion, then the detection sensitivity is enhanced, but the circuit complexity increases

Engineering Contradiction:

Improvedetection sensitivityVSAvoidcircuit complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The feedback circuit provides a systematic approach to control the diode string operation, replacing the need for numerous diodes with a controlled feedback mechanism. While the feedback circuit itself adds complexity, it reduces the overall device complexity by eliminating the need for large arrays of diodes and their associated interconnections, routing, and layout complexity.

Inventive Principle:

Principle #23Feedback

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

The solution achieves enhanced detection sensitivity without increasing the number of diodes, stabilizing circuit operation and reducing power supply voltage variations.

Implementation Method 1

a temperature change rate of each of the diodes is small

Methodology Applied

Scientific EffectThermal voltage effect:

Implementation Method 2

converts infrared rays absorbed by an infrared absorber into heat

Methodology Applied

Scientific EffectAbsorption: Absorption (EM radiation)

Data Source

PatentEP4105617B1Infrared detecting element

Publication Date: 2025.12.24 MITSUBISHI ELECTRIC CORP

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AI summary

A diode (11) is provided on a substrate (1) and thermally insulated from the substrate (1). A positive feedback circuit (18) provides a positive feedback loop so that when a current of the diode (11) decreases due to a change in temperature of the diode (11), the positive feedback circuit (18) further decreases the current of the diode (11), and when the current of the diode (11) increases, the positive feedback circuit (18) further increases the current of the diode (11).