Infrared Light Source Thermal Control via Periodic Modulation
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Solution Overview
Problem
Existing gas sensors face challenges with the operation and control of infrared light sources, including overheating, limited operational life, and the need for robust power supplies due to varying internal resistances, which leads to increased costs and complexity.
Innovation Solution
A control system that adjusts the power input to the light source with a frequency shorter than the thermal time constant of the light source, gas, or detector, using pulse width modulation and feedback signals to optimize energy delivery and extend the operational life of the light source.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If conventional control methodologies are used for infrared light sources, then the light source can operate, but overheating occurs resulting in decreased operational life
Solution Approach 1:
The patent applies periodic modulation of the light source at a frequency shorter than the thermal time constant, creating cyclic heating and cooling periods that prevent excessive temperature accumulation and extend operational life
Solution Approach 2:
The patent changes the operational parameters by modulating the light source frequency to be shorter than the thermal time constant, transforming the thermal management approach from continuous operation to periodic cycles that control peak temperatures
2Reliability
If robust power supplies are designed to handle cold resistance conditions, then all sensors can start under all temperature conditions, but the power supply becomes larger and more expensive
Solution Approach 1:
The periodic modulation approach allows gradual warm-up of the light source, enabling soft-start operation that reduces inrush current and allows use of smaller, less robust power supplies while maintaining reliable startup across temperature conditions
Solution Approach 2:
The control system performs preliminary gradual heating through periodic modulation before full operation, preventing thermal shock and excessive current draws that would require oversized power supply components
3Speed
If the light source is modulated at higher frequencies, then the light output response improves, but thermal effects reduce the lifetime of the device
Solution Approach 1:
The patent optimizes the modulation frequency parameter to be shorter than the thermal time constant but not excessively high, finding an optimal balance between response speed and thermal management that extends device lifetime while maintaining fast response
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 approach reduces overheating, prolongs the operational life of the light source, allows for smaller and less robust power supplies, and provides cost savings while maintaining efficient energy delivery.
Implementation Method 1
controlling power input to the light source such that the time period of the control frequency is shorter than the thermal time constant of the light source
Implementation Method 2
the use of a photoacoustic gas sensor to convert the optical energy of an amplitude modulated light source into acoustic energy when the light mechanically and thermally excites the gaseous species of interest
Implementation Method 3
A gas sensor includes a light source, a power source in operative connection with the light source
Data Source
AI summary
A gas sensor includes a light source, a power source in operative connection with the light source and a control system in operative connection with the light source and the power supply. The control system is adapted to control power input from the power source to the light source such that the time period of the control frequency is shorter than the thermal time constant of at least one of (i) the infrared light source, (ii) the gas within the sensor, or (iii) a detector of the sensor. The time period of the control frequency can, for example, be no greater than ⅓ of the thermal time constant, no greater than 1/10 of the thermal time constant, or even no greater than 1/20 of the thermal time constant. A feedback signal can be provided to the control system assist in achieving control.