Thermal Convection Accelerometer Heating Control Circuit

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Solution Overview

Problem

Conventional thermal convection-based accelerometers have slow temperature stabilization speed due to small bandwidth in heating control circuits, leading to high power consumption and low data rates.

Innovation Solution

A closed-loop heating control circuit with linear amplification, using a heating resistor, thermocouples, amplifiers, modulators, and digital sequences to adjust heating power, avoiding the introduction of integrator poles, thereby increasing bandwidth and stabilization speed without increasing chip area or power consumption.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If an integrator is used in the heating control circuit to reduce bandwidth, then temperature stability is improved, but stabilization speed decreases

Engineering Contradiction:

Improvetemperature stabilityVSAvoidstabilization speed

Core Design Contradiction:

Stability of the object's compositionVSSpeed

Solution Approach 1:

The patent changes the control parameter from continuous analog integration to discrete digital pulse-width modulation (PWM). By using a digital modulator to generate PWM signals based on temperature error, the system achieves both stability and fast response without the bandwidth limitations of analog integrators. The digital approach allows rapid switching of the heating resistor while maintaining precise temperature control.

Inventive Principle:

Principle #35Parameter changes

2Measurement precision

If the bandwidth of the heating control circuit is reduced, then temperature control precision is improved, but data rate decreases

Engineering Contradiction:

Improvetemperature control precisionVSAvoiddata rate

Core Design Contradiction:

Measurement precisionVSProductivity

Solution Approach 1:

The patent replaces the conventional analog heating control circuit with a digital control system. The digital modulator converts temperature error signals into PWM duty cycle adjustments, which then control the heating resistor through digital switching. This substitution of digital for analog circuitry eliminates the bandwidth limitations that constrained both precision and data rate in traditional systems.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Measurement precision

If temperature stabilization time is extended, then measurement accuracy is improved, but power consumption increases

Engineering Contradiction:

Improvemeasurement accuracyVSAvoidpower consumption

Core Design Contradiction:

Measurement precisionVSUse of energy by moving object

Solution Approach 1:

The patent implements periodic temperature measurements and corresponding periodic heating control through PWM modulation. Instead of continuous heating that would waste energy, the system periodically samples temperature via the thermocouple and adjusts heating duty cycle accordingly. This periodic action maintains measurement accuracy while significantly reducing overall power consumption compared to continuous stabilization approaches.

Inventive Principle:

Principle #19Periodic action

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

Significantly improves stabilization speed of the closed-loop heating control circuit, reducing power consumption and maintaining high data rates while avoiding significant increases in chip area.

Implementation Method 1

a heating resistor configured for heating the enclosed cavity

Methodology Applied

Scientific EffectJoule heating: Joule Heating

Implementation Method 2

a temperature-control thermocouple configured for sensing a temperature in the enclosed cavity and generate a temperature voltage signal

Methodology Applied

Scientific EffectSeebeck effect: Seebeck Effect

Implementation Method 3

an amplifier coupled to the temperature-control thermocouple and configured for amplifying the temperature voltage signal to obtain an amplified temperature voltage signal

Methodology Applied

Scientific EffectElectrical amplification:

Data Source

PatentUS11293938B2Thermal convection based accelerometer and heating control method therefor

Publication Date: 2022.04.05 MEMSIC

AI summary

Thermal convection based accelerometers and heating control methods therefor are described. The heating control method includes: sensing a temperature in the enclosed cavity and generating a temperature voltage signal; amplifying the temperature voltage signal to obtain an amplified temperature voltage signal; calculating a voltage difference between the amplified temperature voltage signal and a reference voltage signal; converting the voltage difference into a digital sequence by using a modulator; obtaining a heating power adjustment factor representing the voltage difference based on the digital sequence; obtaining a heating power control parameter based on the heating power adjustment factor and an initial heating power factor; converting the heating power control parameter into a switch control signal; and turning on or off a heating control switch coupling with a heating resistor for heating the enclosed cavity in series according to the switch control signal.