Parallel Power Element Mismatch Detection via Emitter Voltage Signals
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Solution Overview
Problem
Power electronic modules experience failures due to crack propagation, wire-bond lift-off, delamination, and electro-thermo-lifetime mismatches, which are difficult to predict or detect, leading to inefficiencies in maintenance and operation.
Innovation Solution
A method for detecting mismatches between parallel power electronic elements by measuring emitter voltages during a common turn-off event, extracting data on local extremums, and deducing the presence or absence of mismatches using analog and logical circuits, potentially identifying the most degraded element.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If steady-state Vce measurement is used to monitor wire-bonds, then device degradation can be detected, but the method requires individual drivers, clamp circuits, and high voltage connections that increase system complexity and impose design constraints
Solution Approach 1:
The patent merges the monitoring function into a common circuit that can measure multiple parallel devices simultaneously without requiring individual drivers or clamp circuits for each device. The differential voltage measurement approach combines multiple measurement functions into a single integrated system.
Solution Approach 2:
The monitoring circuit is designed to be universal and can monitor multiple parallel power devices (IPTS, MOSFETs, Diodes) using the same circuit architecture. The circuit performs multiple functions including voltage measurement, differential comparison, and degradation detection without requiring device-specific components.
2Measurement precision
If steady-state Vce measurement is performed at high current, then device-specific voltage can be obtained, but temperature and current dependencies require calibration and corrections that increase measurement complexity
Solution Approach 1:
The patent uses differential voltage measurement that copies the voltage drop across parasitic inductors in series with each device. By measuring the difference between two such voltage drops, the method obtains device-specific information without requiring absolute voltage calibration, as the differential measurement cancels out common-mode temperature and current dependencies.
3Reliability
If clamp circuits are implemented to protect the measurement, then device protection is provided, but time-response becomes incompatible with fast switching frequencies and extreme duty-cycles
Solution Approach 1:
The patent introduces parasitic inductors (or equivalent circuit elements) as intermediaries between the power devices and the measurement circuit. These inductors naturally limit current changes and protect the measurement circuit from voltage spikes without requiring active clamp circuits, thereby maintaining fast response times compatible with high switching frequencies.
4Measurement precision
If high voltage connections are implemented for measurement, then direct device monitoring is possible, but design and safety constraints increase making the solution difficult to adopt
Solution Approach 1:
The patent replaces direct high-voltage electrical connections with a measurement approach that uses low-voltage differential measurements of voltage drops across parasitic inductors. This substitution allows monitoring of high-voltage devices through low-voltage signals, eliminating the need for complex high-voltage connection design and safety infrastructure.
Data Source
AI summary
Method for detection of a mismatch between parallel power electronic elements into a power electronic module, said method comprising: a. in response to the detection of a common turn-off of said elements, triggering a measuring period; b. during the measuring period, measuring a sequence of emitter voltages VeE of at least one of said elements; c. extract data, from the measurements, said data including the signs and/or the amplitude of local extremums of said emitter voltage VeE during the measuring period; d. deduce from the extracted data at least an existence or an absence of a mismatch between said elements.