Driver Circuit Current Sensing for Fast Switch Turn-Off

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Solution Overview

Problem

Modern semiconductor switches, particularly IGBTs, experience turn-off overvoltages due to high switching speeds, which occur too quickly for conventional driver circuits to effectively countermeasure, potentially leading to damage or destruction.

Innovation Solution

A driver circuit and method that measure the collector current or gate current during the turn-off process to determine the magnitude of current change, allowing for earlier detection of excessive turn-off voltages and implementing control measures to reduce current change, thereby providing sufficient reaction time for countermeasures.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If faster switching speed is used in semiconductor switches, then switching losses are reduced, but turn-off overvoltages increase and reaction time for countermeasures decreases

Engineering Contradiction:

Improveswitching lossesVSAvoidservice life of semiconductor switch

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

The driver circuit measures the time derivative of the collector current (dIc/dt) during the turn-off process to detect excessive turn-off overvoltages before they cause damage. This preliminary detection enables the driver circuit to initiate countermeasures such as temporarily re-switching the semiconductor switch, preventing damage while maintaining fast switching speeds and reducing switching losses.

Inventive Principle:

Principle #10Preliminary action

2Measurement precision

If conventional measurement methods (dUce/dt) are used, then detection is possible, but reaction time is insufficient for modern fast semiconductor switches

Engineering Contradiction:

Improvedetection capabilityVSAvoidreaction time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The patent replaces the conventional voltage-based measurement method (dUce/dt) with a current-based measurement method (dIc/dt). This substitution provides earlier and more accurate detection of excessive turn-off overvoltages during the turn-off process, enabling the driver circuit to initiate countermeasures within the remaining time after measurement, thus providing sufficient reaction time for modern fast semiconductor switches.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Reliability

If switch-off is delayed as a general countermeasure, then damage is prevented, but switching losses increase significantly

Engineering Contradiction:

Improveprotection of semiconductor switchVSAvoidswitching losses

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The driver circuit continuously monitors the time derivative of the collector current (dIc/dt) during the turn-off process and provides feedback when excessive turn-off overvoltages are detected. This feedback mechanism enables the driver circuit to initiate targeted countermeasures such as temporary re-switching, protecting the semiconductor switch from damage while maintaining fast switching speeds and avoiding significant increases in switching losses.

Inventive Principle:

Principle #23Feedback

Data Source

PatentEP4264832B1Driver switch and method for controlling a semiconductor circuit

Publication Date: 2025.10.15 SIEMENS AG

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AI summary

The invention relates to a driver circuit and a method for controlling a semiconductor switch, wherein, during the course of a switch-off process of the semiconductor switch, either the level of the gate current during a period after the start of the switch-off process or a timespan from the start of the switch-off process to achieving a definable threshold value of the collector-emitter voltage, is measured and, according to the measurement result, a temporary reactivation of the semiconductor switch is controlled.