Dual-Switch Heater Control for Overtemperature Fire Shutdown
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Solution Overview
Problem
Existing fluid heating systems in motor vehicles face a fire risk due to continuous operation of a power transistor failure, particularly when water boils and evaporates, which is not compliant with safety standards like ISO 26262.
Innovation Solution
A control device with a first and second electronic switch, a microcontroller, and a logic control module that monitors fluid temperatures, using sensors and comparators to open the switches if temperatures exceed thresholds or differ significantly, ensuring safety redundancy and preventing fires.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single electronic switch controls the heating element, then the device complexity is reduced, but the reliability deteriorates due to undetected failures causing continuous operation
Solution Approach 1:
The control device is segmented into two independent control paths: a primary control path using a microcontroller and first electronic switch, and a secondary safety path using a logic control module and second electronic switch. This segmentation allows independent monitoring and control, so that if one path fails, the other can detect the failure and shut down the heating element, thus improving reliability without excessive complexity increase.
Solution Approach 2:
A digital coupling link acts as an intermediary between the microcontroller and logic control module, enabling communication of temperature data and control signals. This intermediary allows the two independent control paths to coordinate their actions, with the logic control module receiving temperature information and independently making shutdown decisions based on its own temperature sensor, ensuring redundant safety monitoring.
2Measurement precision
If temperature monitoring is simplified to a single sensor, then the measurement precision is reduced, but the device complexity is lowered
Solution Approach 1:
Different quality levels of temperature monitoring are applied to different control paths: the microcontroller uses a first temperature sensor for primary control, while the logic control module uses a second temperature sensor for independent safety verification. This local differentiation ensures that each control path has sufficient measurement capability for its specific function, with the dual-sensor approach providing cross-validation that enhances overall measurement reliability.
Solution Approach 2:
The logic control module continuously monitors temperature through its own sensor in advance, independently of the microcontroller's monitoring. This preliminary and independent temperature measurement allows the safety path to detect overheating conditions even before the primary control system responds, enabling proactive safety intervention and failure detection.
3Speed
If a single control path is used, then the response speed is faster, but the reliability deteriorates due to lack of failure detection
Solution Approach 1:
The logic control module performs periodic temperature monitoring and independent evaluation at predetermined intervals, separate from the microcontroller's control cycle. This periodic independent monitoring ensures that even if the primary control system fails to detect a fault, the safety path will eventually detect it through its own measurements and trigger a shutdown, providing reliable failure detection while maintaining acceptable response speeds.
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 system reliably detects transistor failures, preventing fires and ensuring the safety of the heating system and vehicle occupants by shutting off the heating element when unsafe conditions are detected.
Implementation Method 1
a sensor for measuring a first temperature and a microcontroller associated with the first electronic switch, the microcontroller being configured to open or close the first switch according to the value of the first temperature measured, a sensor for measuring a second temperature
Implementation Method 2
an electric heating element configured to heat said fluid
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
The invention concerns a control device comprising: a first electronic switch (2) suitable for being connected to an electric heating element (101) and a second electronic switch (3) suitable for being connected to an electric heating element (101), a sensor for measuring a first temperature (T1) and a microcontroller (4) associated with the first electronic switch (2), the microcontroller (4) being configured to open or close the first switch (2) depending on the first measured temperature value (T1), a sensor for measuring a second temperature (T2) and a logic control module (5) associated with the second electronic switch (3) and comprising a comparator (6) arranged to compare the second measured temperature (T2) with a threshold, the module (5) being configured to open or close the second switch (3) depending on the result of the comparison.