Integrated Thermal Fuse and Diode Circuit Protection

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Solution Overview

Problem

Existing circuit protection devices using thermal fuses and diodes are cumbersome due to the need for separate, labor-intensive welding of discrete components, resulting in an incompact and larger volume structure.

Innovation Solution

Integration of a thermal fuse and diode into a single circuit protection device with conductive vias and insulation layers, allowing for a compact structure and simplified soldering onto a circuit board using Surface Mount Technology (SMT), eliminating the need for lead wires.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If thermal fuse and diode are used as discrete parts, then overcurrent and overvoltage protection functions are achieved, but the structure becomes incompact and volume increases

Engineering Contradiction:
Improveprotection functionVSAvoiddevice volume
Core Design Contradiction:
ReliabilityVSVolume of stationary object

Solution Approach 1:

The patent combines the thermal fuse and diode into a single integrated circuit protection device. The thermal fuse body and diode are mounted on the same substrate with their leads interconnected, forming one unified component that provides both overcurrent and overvoltage protection functions while reducing overall device volume and simplifying installation.

Inventive Principle:
Principle #5Merging (Combining)

2Reliability

If thermal fuse and diode are welded separately through lead wires, then protection function is achieved, but time consumption and labor increase

Engineering Contradiction:
Improveprotection functionVSAvoidinstallation efficiency
Core Design Contradiction:
ReliabilityVSProductivity

Solution Approach 1:

The patent combines the thermal fuse and diode into a single integrated circuit protection device. The thermal fuse body and diode are mounted on the same substrate with their leads interconnected, forming one unified component that provides both overcurrent and overvoltage protection functions while reducing overall device volume and simplifying installation.

Inventive Principle:
Principle #5Merging (Combining)

3Reliability

If thermal fuse and diode are welded separately through lead wires, then protection function is achieved, but the structure becomes complex and inconvenient to use

Engineering Contradiction:
Improveprotection functionVSAvoidinstallation convenience
Core Design Contradiction:
ReliabilityVSEase of operation

Solution Approach 1:

The patent combines the thermal fuse and diode into a single integrated circuit protection device. The thermal fuse body and diode are mounted on the same substrate with their leads interconnected, forming one unified component that provides both overcurrent and overvoltage protection functions while reducing overall device volume and simplifying installation.

Inventive Principle:
Principle #5Merging (Combining)

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 integrated solution provides a convenient, compact, and efficient circuit protection device that can be easily soldered in a single process, reducing time and labor while maintaining effective overcurrent and overvoltage protection.

Implementation Method 1

When an overcurrent flows through the circuit, the thermal fuse will be heated up and blown

Methodology Applied
Scientific EffectJoule heating: Joule Heating

Implementation Method 2

When the circuit is applied with an overvoltage, the diode will be reversely broken-down, and an electrical current will flow directly from the diode to an earth terminal

Methodology Applied
Scientific EffectReverse breakdown: Avalanche Breakdown

Data Source

PatentEP2991110B1Circuit protection device
Publication Date: 2019.01.30 LITTELFUSE ELECTRONICS (SHANGHAI) CO LTD
  • EP2991110B1 patent drawingFigure 1
  • EP2991110B1 patent drawingFigure 2

AI summary

Embodiments of the present disclosure disclose a circuit protection device comprising a thermal fuse and a diode. The thermal fuse is packaged in a first insulation layer, and the diode is packaged in a second insulation layer. A first exterior electrode pad, a second exterior electrode pad and a third exterior electrode pad are provided on a bottom surface of the first insulation layer. The first electrode surface of the diode and the first electrode end of the thermal fuse are electrically connected to the first exterior electrode pad, the second electrode end of the thermal fuse is electrically connected to the second exterior electrode pad, and the second electrode surface of the diode is electrically connected to the third exterior electrode pad. In this disclosure, the thermal fuse and the diode are integrated into one single circuit protection device, which can be soldered onto the protected circuit in one single process through SMT, thereby it is convenient to use. Further, in the present disclosure, the whole circuit protection device has a very compact structure and a smaller volume.