Boost Chopper Circuit Sacrificial Switching Protection

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Solution Overview

Problem

Existing boost chopper circuits face issues with capacitor failure due to excessive voltage application, as series resonant current becomes uncontrollable when a switch has a short-circuit fault, leading to voltages exceeding capacitor withstand voltages.

Innovation Solution

Incorporating a switching device circuit with a lower withstand voltage than the capacitor circuit, using semiconductors other than wide band gap semiconductors for the switching devices, and employing backflow prevention diodes constructed of wide band gap semiconductors to redirect series resonant current away from capacitors, thereby preventing capacitor failure.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a boost chopper circuit uses high-withstand-voltage capacitors, then capacitor reliability improves, but switching device vulnerability increases

Engineering Contradiction:

Improvecapacitor reliabilityVSAvoidswitching device vulnerability to overvoltage

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent intentionally uses switching devices with lower withstand voltage than the capacitors, making the switching devices the sacrificial components that fail first under overvoltage conditions. This disposable approach protects the more expensive and harder to replace capacitors from damage.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The circuit design pre-establishes a protective mechanism where the lower-withstand-voltage switching devices act as a first line of defense, absorbing or limiting overvoltage stress before it can reach the capacitors. This beforehand cushioning prevents capacitor failure by design.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

2Reliability

If switching devices are designed with lower withstand voltage, then capacitor protection improves, but circuit component cost increases

Engineering Contradiction:

Improvecapacitor protectionVSAvoidcircuit component cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent accepts the cost increase of using lower-withstand-voltage switching devices as a necessary investment to protect the capacitors. The switching devices are designed to be replaceable and sacrificial, while the capacitors remain as permanent, high-value components.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The patent converts the potential harm of overvoltage damage to capacitors into a beneficial protective mechanism, where the lower-withstand-voltage switching devices intentionally fail first, transforming a vulnerability into a protection strategy.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Productivity

If wide band gap semiconductors are used for switching devices, then switching performance improves, but capacitor failure risk increases

Engineering Contradiction:

Improveswitching performanceVSAvoidcapacitor failure risk

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent changes the key parameter of withstand voltage from being higher than capacitors (as with wide band gap semiconductors) to being lower than capacitors. This parameter change maintains switching performance while fundamentally altering the failure mode to protect capacitors.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent applies different quality characteristics to different components: switching devices are designed with lower withstand voltage for protection purposes, while capacitors maintain high withstand voltage for stability. This local differentiation of qualities optimizes the overall system reliability.

Inventive Principle:

Principle #3Local quality

Data Source

PatentUS10164523B2Boost chopper circuit

Publication Date: 2018.12.25 FUJI ELECTRIC CO LTD

AI summary

In a boost chopper circuit, a withstand voltage of at least one device of a switching device circuit is lower than a withstand voltage of a capacitor circuit connected in series to a backflow prevention diode circuit between opposite ends of the switching device circuit.