MOSFET Relay Overcurrent Protection Using Voltage Detection and Signal Fuse

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Solution Overview

Problem

MOSFET relays in vehicle battery circuits are prone to burning due to overcurrent, lacking a reliable protection mechanism, necessitating frequent replacements.

Innovation Solution

An apparatus and method utilizing a voltage detector and signal fuse to calculate a detection voltage value from the current flowing through the MOSFET relay, disconnecting the fuse when the voltage exceeds a threshold to prevent damage, employing an operational amplifier, comparator, and heating element to disconnect the fuse and protect the relay.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If MOSFET relay is used to replace mechanical relay, then reliability is improved (no welding, no noise), but vulnerability to overcurrent damage increases

Engineering Contradiction:

Improverelay reliabilityVSAvoidovercurrent damage susceptibility

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent implements preliminary protection action by detecting overcurrent conditions before they can damage the MOSFET relay. The voltage detector continuously monitors the voltage across the MOSFET relay, and when overcurrent is detected (voltage exceeds threshold), the controller activates the signal fuse to disconnect the circuit in advance, preventing the harmful overcurrent from reaching the MOSFET relay.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent introduces intermediary protective components between the power source and the MOSFET relay. The voltage detector acts as an intermediary sensor that monitors circuit conditions, while the signal fuse serves as an intermediary protective element that sacrifices itself to protect the MOSFET relay from overcurrent damage.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Device complexity

If no separate blocking apparatus is present, then device complexity is reduced, but loss of time increases due to frequent MOSFET relay replacements

Engineering Contradiction:

Improvecircuit complexityVSAvoidrelay replacement time

Core Design Contradiction:

Device complexityVSLoss of time

Solution Approach 1:

The patent employs a signal fuse as a disposable protective element that is intentionally designed to fail first when overcurrent occurs. The signal fuse is a low-cost component that sacrifices itself by melting and disconnecting the circuit, thereby protecting the expensive MOSFET relay from damage. This approach converts the loss from replacing expensive MOSFET relays to replacing inexpensive signal fuses.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The protective apparatus performs preliminary protection action by detecting overcurrent conditions before they can damage the MOSFET relay. The voltage detector continuously monitors the voltage across the MOSFET relay, and when overcurrent is detected (voltage exceeds threshold), the controller activates the signal fuse to disconnect the circuit in advance, preventing the harmful overcurrent from reaching the MOSFET relay.

Inventive Principle:

Principle #10Preliminary action

3Reliability

If voltage detection and fuse disconnection mechanism is added, then protection capability is improved, but device complexity increases

Engineering Contradiction:

ImproveMOSFET relay protectionVSAvoidcircuit structure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent replaces mechanical relay operation with electronic detection and control. Instead of using a mechanical relay that physically opens and closes contacts, the system uses a voltage detector to sense overcurrent conditions and an electronic controller to activate the signal fuse, substituting mechanical action with electronic sensing and control.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 MOSFET relay damage from overcurrent, allowing for easier threshold setting and reducing the need for frequent replacements by disconnecting the fuse before the relay is burned.

Implementation Method 1

a heating element connected with the fuse and generating heat by a heating signal applied from the controller

Methodology Applied

Scientific EffectJoule heating: Joule Heating

Data Source

PatentEP3413420B1Apparatus and method for protecting mosfet relay by using voltage detector and signal fuse

Publication Date: 2023.09.27 LG ENERGY SOLUTION LTD

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AI summary

The present invention relates to an apparatus and a method for protecting a MOSFET relay by using a voltage detector and a signal fuse, which calculate a detection voltage value through a voltage detector from an electrically conducted current value of a MOSFET relay provided in a battery main circuit for a vehicle and pre-block current applied to the MOSFET relay by operating a signal fuse when the calculated voltage value is more than a predetermined threshold to protect the MOSFET relay from being burned.