SSCB Snubber Circuit for Inductive Surge Protection

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Solution Overview

Problem

Solid state circuit breakers (SSCBs) face challenges with voltage surges from inductive loads, which can cause damage to the SSCB due to inductive discharge spikes during switch-off, and existing snubber solutions often require large and expensive components.

Innovation Solution

A snubber circuit comprising a series-connected capacitor and transient voltage suppressor (TVS) is introduced across the switches of the SSCB, allowing the TVS to dissipate some of the energy and the capacitor to store and slowly dissipate the remaining energy, thereby reducing the stress on the SSCB switches.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If a solid state circuit breaker is used to replace electromechanical switches, then response time is improved and size is reduced, but the device becomes vulnerable to damage from inductive discharge spikes

Engineering Contradiction:

Improveresponse timeVSAvoiddevice durability

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

The patent applies beforehand cushioning by placing a snubber circuit across the solid state switches to preemptively protect them from inductive discharge spikes. The snubber circuit, comprising a capacitor and transient voltage suppressor, is positioned to catch and dissipate voltage surges before they can damage the semiconductor devices, thus resolving the contradiction between fast response time and device durability.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

2Reliability

If traditional snubber circuits are used to protect SSCB switches, then device protection is improved, but component size and cost increase

Engineering Contradiction:

Improveswitch protectionVSAvoidsnubber component size

Core Design Contradiction:

ReliabilityVSWeight of stationary object

Solution Approach 1:

The patent applies parameter changes by selecting specific component values for the capacitor and transient voltage suppressor that optimize protection effectiveness while minimizing size and cost. The capacitor value is chosen to be sufficient to handle the inductive discharge energy, and the TVS is selected with appropriate breakdown voltage and power rating, achieving switch protection with compact, cost-effective components rather than oversized traditional snubber circuits.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If higher-rated components are used to withstand inductive discharge spikes, then device protection is improved, but cost increases

Engineering Contradiction:

Improveenergy dissipation capabilityVSAvoidcomponent cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent applies segmentation by dividing the energy dissipation function between two specialized components: a capacitor that handles the bulk energy storage and a transient voltage suppressor that clamps the voltage to safe levels. This segmentation allows each component to be rated for a portion of the total energy rather than requiring a single component to handle the entire inductive discharge spike, reducing overall component cost while maintaining protection effectiveness.

Inventive Principle:

Principle #1Segmentation

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

This solution effectively mitigates the risk of damage to SSCB switches during inductive load disconnection, allowing for the use of lower-rated, less expensive components while maintaining the benefits of SSCBs, such as small size, low weight, and fast response times.

Implementation Method 1

MOSFETS are limited as regards the amount of energy that can be dissipated during avalanche mode

Methodology Applied

Scientific EffectAvalanche breakdown: Avalanche Breakdown

Implementation Method 2

A snubber circuit comprising a series-connected capacitor and transient voltage suppressor (TVS) is introduced across the switches of the SSCB

Methodology Applied

Scientific EffectCapacitance: Capacitance

Data Source

PatentUS12334295B2Solid state circuit breaker snubber

Publication Date: 2025.06.17 HAMILTON SUNDSTRAND CORP

AI summary

A snubber circuit for a solid state circuit breaker (SSCB), the snubber circuit comprising a series connected capacitor and transient voltage suppressor, TVS, connected across switches of the SSCB, and a bidirectional solid state circuit breaker comprising: a main SSCB circuit configured to be connected between a power supply and a load, and comprising first and second semiconductor switches connected in series, and a snubber circuit as described above having a first end connected to a first end of the first semiconductor switch and a second end connected to a second end of the second semiconductor switch.