IGBT Junction Temperature Measurement Using Auxiliary Emitter Voltage Drop
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Solution Overview
Problem
Existing methods for measuring the junction temperature of IGBT devices are bulky, costly, and not well-suited for online measurement, especially at high frequencies required in power applications, and often require direct access or additional components, making them impractical for timely and accurate estimation.
Innovation Solution
A method and apparatus that measure the junction temperature of IGBT devices by analyzing the emitter voltage drop between the main and auxiliary emitters during switching operations, using parasitic inductances to determine the junction temperature and collector current through direct measurement of electrical characteristics, allowing for simultaneous estimation of both parameters at the same time instance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If thermocouple is mounted inside the packaged IGBT device or close thereto, then junction temperature measurement accuracy is improved, but device complexity and implementation cost increase
Solution Approach 1:
The IGBT device itself is used to generate the measurement signal through its inherent switching operation. The gate-emitter voltage waveform naturally contains temperature-dependent characteristics that can be extracted without external sensors, making the device self-measuring
Solution Approach 2:
The mechanical/physical thermocouple mounting approach is replaced with an electrical measurement method. Instead of physically attaching a thermocouple to the device, the invention uses electrical signal analysis of the gate-emitter voltage waveform to determine temperature
2Measurement precision
If additional components are closely arranged at the IGBT device for measurement, then measurement accuracy is improved, but ease of operation and installation deteriorate
Solution Approach 1:
The measurement system utilizes the existing gate drive circuitry and gate-emitter voltage signal that are already present in the IGBT device operation. No additional measurement components need to be installed, making the system easy to implement while maintaining high measurement accuracy
Solution Approach 2:
The gate-emitter voltage signal serves dual purposes: it controls the IGBT switching operation and simultaneously provides the measurement signal for temperature determination and current estimation, eliminating the need for separate measurement components
3Measurement precision
If conventional current measurement sensors are used, then load current measurement accuracy is improved, but device complexity and cost increase
Solution Approach 1:
Conventional current sensors (Rogowski coils, current transformers) are replaced with an electrical measurement method that extracts current information from the gate-emitter voltage waveform characteristics, eliminating bulky mechanical sensors
Solution Approach 2:
The IGBT device's own gate-emitter voltage signal is used to extract both temperature and current information, making the device self-measuring for multiple parameters without external sensors
4Measurement precision
If direct access to the device is required for measurement, then measurement accuracy is improved, but ease of operation deteriorates
Solution Approach 1:
The gate-emitter voltage signal performs multiple functions: it controls the IGBT switching and simultaneously provides measurement information for temperature and current. This eliminates the need for direct physical access to internal device components while maintaining measurement accuracy
Solution Approach 2:
The measurement system uses signals that are already generated during normal device operation, enabling online measurement without requiring the device to be opened or accessed directly
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
Enables accurate and timely estimation of junction temperature and collector current, facilitating predictive maintenance, temperature protection, and reducing measurement uncertainties, while being suitable for high-frequency operations in power applications.
Implementation Method 1
Due to the bonding wires and the terminal fittings, the internal connections of the IGBT device cause parasitic inductances between the main emitter terminal and the auxiliary emitter terminal of the IGBT device
Data Source
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AI summary
The present invention relates to a method for determining an actual junction temperature (Tj) and/or an actual collector current (Ic) of an IGBT device (2), wherein the IGBT device (2) has a main emitter (EM) and an auxiliary emitter (EA), comprising the steps of: - measuring the characteristics of an emitter voltage drop (VEE') as a difference between a main emitter voltage (VE) at the main emitter (EM) and an auxiliary emitter voltage (VE') at the auxiliary emitter (EA) during a switching operation of the IGBT device (2); and - determining the junction temperature and/or the collector current (Ic) based on the characteristics of the emitter voltage drop (VEE').