Series Power Switching Circuit for Fault-Induced Overheat Shutdown
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Solution Overview
Problem
Semiconductors used in power switching applications, such as MOSFETs, can deteriorate and lead to uncontrollable overheating and potential fires due to issues like rapid oxidation, causing short-circuits and making them difficult to switch off, and existing protection methods like PCB fuses are cumbersome and risky.
Innovation Solution
An electrical power switching circuit with two semiconductor switches connected in series, where a comparator monitors and compares voltage drops across each switch, generating signals to shut down the undamaged switch if a discrepancy is detected, thereby preventing further damage and overheating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single semiconductor switch is used for power switching, then the device can control current effectively, but the device may become uncontrollable and hazardous when damaged due to short-circuit between gate and drain
Solution Approach 1:
The patent divides a single semiconductor switch into two series-connected semiconductor switches. This segmentation allows the healthy switch to interrupt current flow when one switch becomes damaged, preventing the harmful effects of uncontrollable current flow, overheating, and potential fire. The series connection ensures that if either switch opens, the entire current path is broken.
2Reliability
If PCB fuses are used to protect against overcurrent, then further damages can be avoided, but the protection method produces high temperatures and may even cause fire
Solution Approach 1:
The patent replaces the mechanical/thermal protection mechanism of PCB fuses with an electronic control system. The system uses voltage monitoring circuits to detect abnormal voltage drops across semiconductor switches and automatically controls the switches to open when damage is detected. This electronic approach avoids the high temperatures and fire risks associated with melting fuse elements.
3Reliability
If PCB fuses are used for protection, then overcurrent damage can be limited, but the protection is difficult to manage in case of updates or revisions
Solution Approach 1:
The patent replaces fixed PCB fuse elements with programmable electronic control circuits that can be updated through software or configuration changes. This allows the protection logic to be adapted when PCB designs or component specifications are revised, providing much greater flexibility and ease of management compared to physical fuse elements that would require redesign or replacement.
4Reliability
If two semiconductor switches are connected in series, then the probability of both switches being damaged is very low and current can be interrupted through the damaged switch, but the device complexity increases
Solution Approach 1:
The patent segments the power switching function into two series-connected semiconductor switches. While this increases the component count, it provides fault tolerance by allowing the healthy switch to interrupt current when one switch fails. The segmentation creates a backup mechanism where the series connection itself becomes the protection mechanism.
Solution Approach 2:
The patent implements voltage monitoring circuits that continuously measure the voltage drops across each semiconductor switch and provide feedback to the control system. When abnormal voltage drops indicate damage, the feedback triggers automatic control signals to open the switches. This feedback mechanism automates the protection function, reducing the need for complex manual management or additional protective 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 effectively reduces the risk of overheating and fire by ensuring that the undamaged switch can interrupt current through the damaged one, allowing for early detection and automatic shutdown, even if the damaged switch is unresponsive, thus enhancing safety and reliability.
Implementation Method 1
A damaged semiconductor switch is detected by monitoring and comparing the voltage drops across both switches. As long as both switches are properly working, both voltage drops are expected to be similar. A damaged semiconductor switch usually shows a higher voltage drop than an undamaged switch.
Data Source
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AI summary
The present invention relates to an electrical power switching circuit (1) comprising: a first semiconductor switch (Q1) having a first control input (C1) and a second semiconductor switch (Q2) having a second control input (C2), wherein the first semiconductor switch (Q1) and the second semiconductor switch (Q2) are connected in series; a comparator (2) configured to compare a first voltage to a second voltage and to output a first electrical signal (S1) if the first voltage exceeds the second voltage by a first predetermined threshold and to output a second electrical signal (S2) if the second voltage exceeds the first voltage by a second predetermined threshold, wherein the first voltage corresponds to a voltage drop (u1) across the first semiconductor switch (Q1) and the second voltage corresponds to a voltage drop (u2) across the second semiconductor switch (Q2); and a combiner (3) configured to combine the first signal (S1) and the second signal (S2) and to feed a combined signal (SC) to the first (C1) and second (C2) control inputs of the first (Q1) and second (Q2) semiconductor switches.