PTC Laminar Fuse Element for High Current Protection

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Solution Overview

Problem

Existing protection devices for electrical apparatuses, such as secondary batteries, face challenges in allowing a large current flow while ensuring protection from excessive current and providing a resettable function after the cause of excessive current is eliminated.

Innovation Solution

A protection device comprising a PTC laminar element with throughholes and electrically conductive metal thin layers on its main surfaces, connected by a fuse layer on the side surface, which preferentially directs excessive current through the fuse layer to interrupt it, thereby protecting the device and allowing current flow, with the ability to reset once the cause is removed.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If a PTC component is used as a protection device, then it can be positioned compactly inside the sealing plate, but it has larger resistance and cannot pass a large amount of current

Engineering Contradiction:

Improveprotection device sizeVSAvoidcurrent carrying capacity

Core Design Contradiction:

Volume of moving objectVSReliability

Solution Approach 1:

The protection device is segmented into two functional parts: a PTC laminar element for compact positioning and a fuse layer for low-resistance current conduction. The PTC element is divided into multiple throughholes with fuse layers, allowing current to flow through multiple paths while maintaining compact size.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The protection device combines PTC composition material with electrically conductive metal thin layers and fuse layer material to create a composite structure that exhibits both PTC properties for protection and low resistance for current carrying capacity.

Inventive Principle:

Principle #40Composite materials

2Reliability

If a fuse device is used as a protection device, then it has low resistance and can pass large current, but it cannot be reset after blowing

Engineering Contradiction:

Improvecurrent carrying capacityVSAvoidreset function

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The fuse layer is designed to be sacrificial (discarded) when excessive current occurs, while the PTC laminar element remains intact and can recover (reset) after the excessive current cause is eliminated. The system recovers by allowing the PTC element to return to its low-resistance state.

Inventive Principle:

Principle #34Discarding and recovering

Solution Approach 2:

The protection device transitions between different resistance states dynamically: low resistance during normal operation allowing current flow, and high resistance when PTC activates to interrupt excessive current. This dynamic behavior enables both current carrying capacity and protection function.

Inventive Principle:

Principle #15Dynamics

3Device complexity

If a spacer is used in place of PTC device inside the sealing plate, then the structure is simplified, but protection from excessive current cannot be ensured

Engineering Contradiction:

Improveprotection device structureVSAvoidexcessive current protection

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The PTC laminar element serves multiple functions: it provides structural support like a spacer, enables compact positioning, and simultaneously provides excessive current protection through its PTC properties and fuse layer configuration.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 interrupts excessive current while allowing a large amount of current to flow and provides a resettable function, ensuring superior voltage resistance and repeated use without arc generation, with the ability to handle currents up to double the rated capacity.

Implementation Method 1

a PTC laminar element which is formed of a PTC composition and has at least one throughhole

Methodology Applied

Scientific EffectPTC (Positive Temperature Coefficient) effect: Thermistor

Implementation Method 2

a fuse layer which is positioned on a side surface defining at least one of said at least one throughhole and electrically connects the electrically conductive metal thin layers

Methodology Applied

Scientific EffectJoule heating: Joule Heating

Data Source

PatentUS10090509B2Protection element

Publication Date: 2018.10.02 LITTELFUSE JAPAN GK

AI summary

The present invention provides a protection device which includes: a PTC laminar element which is formed of an insulation resin and has at least one throughhole; electrically conductive metal thin layers which are positioned on each of main surfaces of the laminar element, and a fuse layer which is positioned on a side surface defining at least one of said at least one throughhole and electrically connects the electrically conductive metal thin layers which are positioned on each of main surfaces of the laminar element. The protection device of the present invention allows a larger amount of a current to flow therethrough and can provide a protection from an excessive current.