Chopper Circuit Diode Short-Circuit Protection

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Solution Overview

Problem

Conventional chopper circuits face degradation and failure of switching devices due to short-circuit faults in diodes, particularly during reverse recovery surge, leading to current flowback and leakage currents that can degrade or fail the switching devices.

Innovation Solution

A chopper circuit design that includes a reactor, direct-current output circuit, capacitor circuit, diodes, switching devices, a short-circuit detector, and a controller to manage switching device states, ensuring that when a short circuit is detected, the corresponding switching device is turned on to prevent current flowback through parasitic diodes, thereby reducing degradation and failure.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If both switching devices are turned off when a diode short-circuit fault is detected, then the circuit attempts to protect itself, but current flows back through the parasitic diode of the other switching device causing degradation or failure

Engineering Contradiction:

Improveswitching device reliabilityVSAvoidcurrent flowback and leakage current

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

Instead of turning off both switching devices when a diode short-circuit fault is detected (conventional approach), the invention turns ON the other switching device that is normally off. This inversion of the protective action prevents current flowback through the parasitic diode by providing a low-impedance path through the turned-on switching device, thereby eliminating the harmful current flowback while maintaining switching device reliability

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The invention converts the harmful current flowback condition into a beneficial situation by turning on the other switching device. This action transforms the potential damage path into a controlled current path, where the current that would have flowed through the parasitic diode is instead directed through the actively controlled switching device, preventing degradation while maintaining circuit operation

Inventive Principle:

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

2Object-affected harmful factors

If the switching device is left off to prevent current flowback, then current leakage through parasitic diode is avoided, but the circuit cannot handle voltage differences when capacitor voltage exceeds power supply voltage

Engineering Contradiction:

Improvecurrent leakage and heat generationVSAvoidcircuit adaptability to voltage conditions

Core Design Contradiction:

Object-affected harmful factorsVSAdaptability or versatility

Solution Approach 1:

The invention implements dynamic control of the switching device state based on real-time detection of diode health status and voltage conditions. When a diode short-circuit fault is detected and capacitor voltage exceeds power supply voltage, the system dynamically transitions the other switching device from off-state to on-state, adapting the circuit behavior to the specific fault condition and voltage differential, thereby preventing current leakage while maintaining adaptability

Inventive Principle:

Principle #15Dynamics

Data Source

PatentUS9812966B2Chopper circuit

Publication Date: 2017.11.07 FUJI ELECTRIC CO LTD

AI summary

A chopper circuit includes a controller that performs control of turning on a second switching device when a short circuit detector detects a short circuit of a first diode, and performs control of turning on a first switching device when the short circuit detector detects a short circuit of a second diode.