MOSFET Gate-Source Fuse Circuit Against Parasitic Turn-On
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Solution Overview
Problem
Semiconductor switching elements, particularly MOSFETs, face the risk of unintentional reactivation due to voltage potential differences caused by self-inductances during switching off, leading to potential overload and failure in motor vehicle on-board networks.
Innovation Solution
A circuit device with a fuse unit, including a bipolar transistor and diodes, is used to equalize the gate and source voltage potentials after disconnection, preventing unintentional reactivation by ensuring both connections have the same potential, thus preventing the semiconductor switch from switching on again.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a MOSFET is used for switching in motor vehicle on-board networks, then switching times and switching capacity are improved, but the risk of unintentional reactivation due to voltage potential differences increases
Solution Approach 1:
The fuse unit is configured to proactively equalize voltage potentials between gate and source terminals before unintentional reactivation can occur. By detecting voltage potential differences that could lead to parasitic turn-on and immediately counteracting them through controlled electrical connection, the system prevents the harmful effect before it manifests.
Solution Approach 2:
The fuse unit acts as an intermediary mechanism between the gate and source terminals. It selectively connects these terminals to equalize voltage potentials when dangerous potential differences arise, serving as a protective mediator that prevents direct harmful interactions between the terminals while allowing normal operation when potentials are safe.
2Productivity
If self-inductances in the circuit are present, then the MOSFET can switch off the current path, but voltage potential differences arise that cause unintentional reactivation
Solution Approach 1:
The fuse unit converts the harmful voltage potential differences generated by self-inductances into a beneficial protective mechanism. By detecting these potential differences and using them to trigger the fuse element's protective action, the previously harmful voltage spikes become the signal that activates the protection system, turning the problem into its own solution.
3Reliability
If a fuse unit is added to prevent unintentional reactivation, then reliability is improved, but device complexity increases
Solution Approach 1:
The fuse unit merges multiple protective functions into a single integrated circuit element. By combining voltage detection, comparison, and protective connection capabilities within one fuse unit structure, the design achieves comprehensive protection without proportionally increasing complexity. The merged structure efficiently handles multiple aspects of overvoltage protection simultaneously.
Solution Approach 2:
The fuse unit serves multiple functions: it detects voltage potential differences, compares them against safe thresholds, and executes protective equalization actions. This multi-functional design allows a single component to address various aspects of MOSFET protection, reducing the need for separate dedicated circuits for each protective function.
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 solution effectively prevents MOSFETs from unintentionally switching on due to negative source voltage potentials, thereby protecting the semiconductor switching element from damage and ensuring reliable disconnection.
Implementation Method 1
The fuse element is configured to establish an electrical connection between the gate terminal and the source terminal when a voltage threshold is reached
Data Source
Figure 1
AI summary
A circuit apparatus (2) and a method for safely disconnecting a semiconductor switching element (4), in particular a MOSFET, are specified, wherein the semiconductor switching element (4) has a gate terminal (G), a source terminal (S) and a drain terminal (D), wherein, during operation of the semiconductor switching element (4), a current path (6) between the drain terminal (D) and the source terminal (S) can be disconnected in a reversible manner by means of the gate terminal (G) and the gate terminal (G) has a gate voltage potential (UG) and the source terminal (S) has a source voltage potential (Us). A fuse unit (12) is arranged between the gate terminal (G) and the source terminal (S), said fuse unit being configured and designed to electrically connect the gate terminal (G) to the source terminal (S) depending on a (voltage) potential difference (AU) between the gate voltage potential (UG) and the source voltage potential (Us) after the current path (6) has been disconnected, with the result that the gate voltage potential (UG) and the source voltage potential (Us) are matched.