FET Power Feed Switching for Short-Circuit Overcurrent Protection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing power feeding control apparatuses for vehicles fail to prevent overcurrent during the transition period when switching from off to on, leading to abnormal temperature and potential breakdown of the FET due to short-circuit conditions.
Innovation Solution
A power feeding control apparatus with an N-channel type FET, a first determination circuit to check the control voltage, a second determination circuit to check the drain-source voltage, and a switching circuit that switches the FET off when both thresholds are met, ensuring the FET is switched back off during high current transitions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the FET is switched from off to on during the transition period, then the FET can conduct electric current, but the resistance value between drain and source is large causing drain-source voltage to be greater than or equal to a predetermined voltage which may trigger erroneous switching off
Solution Approach 1:
The patent employs feedback control by continuously monitoring the drain-source voltage and comparing it with a predetermined threshold voltage. When the drain-source voltage exceeds the threshold during the transition period, the system detects this condition and prevents erroneous switching off by maintaining the gate-source voltage above the threshold, thus ensuring reliable FET operation during transient states
Solution Approach 2:
The patent introduces an intermediary control mechanism that mediates between the switching signal and the FET gate. By adding a voltage holding circuit that maintains the gate-source voltage during the transition period, the system prevents direct erroneous switching off while the FET is transitioning, thus resolving the contradiction between reliability and control complexity
2Productivity
If the FET is switched on when the load is short-circuited, then power feeding is enabled, but an overcurrent continues to flow during the transition period causing the FET temperature to rise to abnormal levels which may cause breakdown
Solution Approach 1:
The patent applies preliminary action by detecting the short-circuit condition before the FET is fully switched on. The system monitors the drain-source voltage and identifies when the load is short-circuited (drain-source voltage equals power supply voltage). Upon detection, the system prevents the FET from being switched on during the transition period, thereby avoiding overcurrent flow and abnormal temperature rise before they can occur
Solution Approach 2:
The patent implements preliminary anti-action by introducing a protective control mechanism that counteracts the potential overcurrent damage before it occurs. The system uses voltage comparison circuits to detect short-circuit conditions and generates a protective signal that prevents the FET switching on during hazardous conditions, thus eliminating the harmful overcurrent effect before it can cause damage
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 overcurrent flow during the transition period, reducing the risk of FET breakdown and maintaining normal operating temperatures by ensuring the FET is switched off when large electric currents are detected.
Implementation Method 1
an N-channel type FET that is provided in an electric current path along which an electric current flows from a DC power supply to a load
Implementation Method 2
a first determination circuit that determines whether or not a control voltage between a gate and the source of the FET is greater than or equal to a first threshold value; a second determination circuit that determines whether or not a drain-source voltage between the drain and the source of the FET is greater than or equal to a second threshold value
Data Source
AI summary
A drain and a source of an N-channel type FET included in a power feeding control apparatus are provided on an electric current path along which an electric current flows from a DC power supply to a load, the drain being a part of the FET into which the electric current is input and the source being a part of the FET from which the electric current is output. A driving circuit switches the FET off when a first determination circuit determines that a control voltage between a gate and the source of the FET is greater than or equal to a first threshold value, and a second determination circuit determines that a drain-source voltage between the drain and the source of the FET is greater than or equal to a second threshold value.