Electro-Thermal Heater Feedback Control Without a Temperature Sensor
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Solution Overview
Problem
Existing electro-thermal devices for gas sensing and infrared emission lack precise temperature control, leading to inefficiencies in gas measurement and power consumption.
Innovation Solution
An electro-thermal device with a digital sigma-delta modulator and readout circuit that uses a closed-loop control system to maintain constant heater temperature, eliminating the need for a dedicated temperature sensor and reducing power losses by applying pulsed electrical power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional heater control circuit is used, then the device structure is simple, but the temperature control precision is insufficient
Solution Approach 1:
The heater and temperature sensor are merged into a single integrated element. The heater structure serves dual functions: generating heat and sensing temperature through its resistance changes, eliminating the need for separate temperature sensing components and achieving precise temperature control through this unified structure
Solution Approach 2:
A feedback control mechanism is implemented where the heater's resistance changes (indicating temperature changes) are continuously monitored and fed back to the control circuit. The control circuit adjusts the driving current accordingly to maintain the desired temperature, creating a closed-loop control system that ensures precise temperature regulation
2Stability of the object's composition
If continuous electrical power is applied to the heater, then the temperature stability is improved, but the power consumption increases
Solution Approach 1:
Instead of continuous power application, the system uses periodic pulsed power delivery to the heater. The control circuit applies electrical power in controlled pulses, allowing the heater temperature to stabilize through thermal inertia while significantly reducing average power consumption compared to continuous operation
Solution Approach 2:
The system maintains continuous temperature stability through feedback control that continuously monitors heater resistance and adjusts power delivery in real-time. This ensures the heater remains at the desired temperature throughout operation while optimizing power consumption through intelligent control rather than continuous full-power operation
3Measurement precision
If a dedicated temperature sensor is added, then the temperature measurement precision is improved, but the device complexity increases
Solution Approach 1:
The heater and temperature sensor are merged into a single integrated element. The heater structure serves dual functions: generating heat and sensing temperature through its resistance changes, eliminating the need for separate temperature sensing components and achieving precise temperature control through this unified structure
Solution Approach 2:
The heater element is designed to perform multiple functions simultaneously: it serves as both the heating element and the temperature sensor. By utilizing the heater's inherent resistance-temperature relationship, the system achieves temperature sensing capability without requiring additional dedicated sensor components
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 solution provides precise temperature control, enhances gas measurement sensitivity, and minimizes power consumption by using the heater as both the heating element and temperature sensor, resulting in lower thermal power losses and reduced emissions.
Implementation Method 1
a heater (11)
Implementation Method 2
The heater itself can be used as the temperature sensor. The measurement of the temperature is done by turning off the driver (50) for a short time (much shorter than the thermal time of the heater), and then measuring the resistance of the heater
Implementation Method 3
measuring the resistance of the heater
Data Source
Figure 1A
Figure 1B
Figure 2A~2B
AI summary
An electro-thermal based device comprises a heater (11), a readout circuit (14), a digital controller (16) having a first input (17) coupled to a first output (18) of the readout circuit (14), and a digital sigma-delta modulator (19) having a first input (20) coupled to an output (21) of the digital controller (16) and an output (22) coupled to the heater (11).