TMR Sensor Lead Overcurrent Protection
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Solution Overview
Problem
Magnetic sensors using TMR elements face the risk of fatal short circuits and fires due to tunnel barrier breakdowns, which existing protection circuits fail to prevent effectively, posing a safety hazard, especially in automotive applications.
Innovation Solution
An electronic circuit board design where TMR elements are connected between a power supply and ground through leads, with specific areas of the leads designed to break and shut off overcurrents upon a short circuit, eliminating the need for complex control mechanisms and enabling miniaturization and cost reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a TMR element is used as the magneto-resistive element, then high sensitivity and low power consumption are achieved, but a breakdown of the tunnel barrier causes a short circuit between power supply and ground, potentially causing fire and fatal damage
Solution Approach 1:
The patent applies preliminary action by pre-designing the lead with a weak section that will break under overcurrent conditions. This preventive measure is built into the structure before failure occurs, so that when a TMR element breakdown happens, the lead automatically breaks to interrupt the short circuit current, preventing fire and fatal damage while allowing the use of TMR elements for their high sensitivity and low power consumption benefits
Solution Approach 2:
The lead acts as an intermediary protective element between the TMR element and the power supply/ground. The weak section of the lead is designed to be the sacrificial component that breaks first during failure, serving as a mediator that protects the more critical components (power supply, surrounding circuitry) from the harmful effects of TMR element breakdown
2Reliability
If a diode or fuse is connected to protect the magneto-resistive element, then the element is protected from overcurrent, but the power supply is not protected from short circuit accidents
Solution Approach 1:
The patent extracts the protection function from separate components (diodes, fuses) and integrates it directly into the lead structure itself. The weak section of the lead becomes the built-in protective element that breaks to protect the power supply from short circuit accidents, eliminating the need for additional protection components and ensuring the power supply is protected
3Reliability
If a control circuit is added to detect failure and stop operation, then fail-safe is realized, but the device size increases and cost increases
Solution Approach 1:
The patent applies self-service by designing the lead to automatically perform the protection function without requiring external control circuits. When a TMR element failure occurs, the weak section of the lead automatically breaks due to overcurrent, interrupting the circuit and achieving fail-safe operation. This passive, self-actuating mechanism eliminates complex control circuits, reducing device size and cost while maintaining reliability
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
Effectively prevents short circuit accidents caused by TMR element failures, protecting the power supply and preventing potential fires, while allowing for the detection of external magnetic fields, thus ensuring safety and reliability in magnetic sensors and other devices.
Implementation Method 1
after a breakdown of a tunnel barrier film of the TMR element, at least a part of the lead breaks by an overcurrent due to a short circuit between the two terminals
Data Source
AI summary
An electronic circuit board includes a TMR element having two terminals connected to a power supply and a ground, respectively, at least through a lead. After a breakdown of a tunnel barrier film of the TMR element, at least a part of the lead breaks by an overcurrent due to a short circuit between the two terminals.