Switching device

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Solution Overview

Problem

Semiconductor power devices, particularly those using SiC, face thermal destruction due to continuous overcurrent flow, which existing technologies struggle to prevent effectively.

Innovation Solution

A switching device with a variable resistance portion made of a conductive barium titanate-based compound is integrated into the SiC semiconductor layer, increasing resistance value under high-temperature conditions to limit overcurrent density, thereby preventing thermal destruction. This structure includes a high-resistance portion closer to the SiC semiconductor layer, which efficiently transfers heat and reduces overcurrent density.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If a conventional SiC semiconductor device is used, then high power switching capability is achieved, but thermal destruction occurs due to continuous overcurrent flow

Engineering Contradiction:

Improvepower switching capabilityVSAvoidresistance to thermal destruction

Core Design Contradiction:

PowerVSReliability

Solution Approach 1:

The patent applies parameter changes by utilizing the temperature-dependent resistance characteristic of barium titanate-based compounds. The variable resistance portion changes its electrical resistance parameter in response to temperature changes, increasing resistance under overcurrent conditions to limit current density and prevent thermal destruction, while maintaining low resistance during normal operation to preserve high power switching capability

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs composite materials by integrating a barium titanate-based compound (which exhibits variable resistance with temperature) into the SiC semiconductor device structure. This composite structure combines the high power capability of SiC with the overcurrent protection特性 of the barium titanate compound, achieving both high power switching and thermal destruction prevention

Inventive Principle:

Principle #40Composite materials

2Reliability

If resistance is increased to limit overcurrent, then thermal destruction is prevented, but normal current flow is impeded

Engineering Contradiction:

Improveprotection against thermal destructionVSAvoidcurrent flow capability

Core Design Contradiction:

ReliabilityVSPower

Solution Approach 1:

The patent applies dynamics by using a variable resistance portion whose resistance value dynamically changes with temperature. During normal operation at low temperature, the resistance remains low to allow full current flow capability. When overcurrent causes temperature rise, the resistance automatically increases to limit current density, providing dynamic adaptation rather than static resistance

Inventive Principle:

Principle #15Dynamics

3Reliability

If a variable resistance portion is added to limit overcurrent, then thermal destruction is prevented, but device complexity increases

Engineering Contradiction:

Improveprotection against thermal destructionVSAvoidstructure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent applies merging by integrating the variable resistance portion directly into the semiconductor device structure, combining the protection function with the existing device components. The barium titanate-based compound is incorporated as part of the electrode structure or as an integrated layer, merging the overcurrent protection function with the power switching function in a unified structure rather than adding separate protection components

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 solution effectively reduces overcurrent density and prevents thermal destruction by increasing the resistance value of the variable resistance portion, extending the time to thermal destruction and improving short-circuit resistance in SiC semiconductor devices.

Implementation Method 1

the first electrode has a variable resistance portion made of a material whose resistance value increases under a prescribed high-temperature condition for limiting current density of overcurrent

Methodology Applied

Scientific EffectVariable resistance effect: Electrical Resistance

Implementation Method 2

a variable resistance portion made of a material whose resistance value increases under a prescribed high-temperature condition

Methodology Applied

Scientific EffectJoule heating: Joule Heating

Implementation Method 3

This structure includes a high-resistance portion closer to the SiC semiconductor layer, which efficiently transfers heat and reduces overcurrent density

Methodology Applied

Scientific EffectHeat conduction: Conduction (thermal)

Data Source

PatentUS11784580B2Switching device

Publication Date: 2023.10.10 ROHM CO LTD

AI summary

A switching device according to the present invention is a switching device for switching a load by on-off control of voltage, and includes an SiC semiconductor layer where a current path is formed by on-control of the voltage, a first electrode arranged to be in contact with the SiC semiconductor layer, and a second electrode arranged to be in contact with the SiC semiconductor layer for conducting with the first electrode due to the formation of the current path, while the first electrode has a variable resistance portion made of a material whose resistance value increases under a prescribed high-temperature condition for limiting current density of overcurrent to not more than a prescribed value when the overcurrent flows to the current path.