Power Semiconductor Junction Temperature Estimation via Online Calibration
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Solution Overview
Problem
Existing methods for estimating the junction temperature and health of power semi-conductors, such as IGBTs, Diodes, and MOSFETs, face challenges due to the sensitivity and variability of thermal models with mounting and operating conditions, as well as the difficulty in calibrating monitoring models using on-line voltage, current, and temperature data.
Innovation Solution
A calibration method that detects stable on-line operating conditions and measures parameters such as voltage, current, and casing temperature to estimate the junction temperature of power semi-conductors. This method minimizes errors between electrical and thermal models using on-line data, allowing for continuous monitoring and degradation assessment during normal operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If thermal model-based temperature estimation is used, then temperature estimate is provided for all operating conditions, but the model requires accurate power loss measurement and thermal impedance data which are difficult to establish a-priori and become unreliable with ageing
Solution Approach 1:
The patent replaces thermal model-based temperature estimation with an electrical measurement method using voltage as a temperature-sensitive parameter. Instead of relying on thermal impedance and power loss calculations, the method uses the temperature coefficient of voltage (dV/dT) measured during normal operation to directly determine junction temperature, eliminating the need for complex thermal modeling and ageing-prone thermal impedance data.
Solution Approach 2:
The method uses the semi-conductor's own electrical characteristics (voltage and current measurements during normal operation) to determine its temperature and health status. The semi-conductor device serves its own monitoring needs by providing the measurement data itself, without requiring external thermal sensors or complex thermal models, enabling continuous monitoring throughout the device lifespan.
2Ease of operation
If voltage-based temperature estimation using TSEP is used, then measurement is performed at low-speed between commutations and applies to all semi-conductor types, but estimation is not possible for all operating points due to ZTC current regions and parasitic elements influence
Solution Approach 1:
The patent addresses ZTC (zero temperature coefficient) current regions by changing the measurement approach: instead of relying on voltage temperature coefficient at problematic current points, the method uses voltage measurements at multiple current points and applies calibration to determine temperature. This allows temperature estimation across all operating points including previously inaccessible ZTC regions.
Solution Approach 2:
The method implements on-line calibration using feedback from voltage and current measurements during normal operation. By continuously monitoring the semi-conductor's electrical characteristics and comparing them against calibrated reference data, the system compensates for parasitic element influences and adapts to ageing effects, maintaining measurement accuracy across all operating conditions.
3Measurement precision
If on-line calibration with voltage, current and temperature data is performed, then parasitic elements are compensated and device ageing is detected, but calibration is particularly difficult due to dependence of voltage on load current
Solution Approach 1:
The patent performs calibration measurements during normal operation at specific current points before using the calibrated data for temperature estimation. By pre-establishing the relationship between voltage, current, and temperature at known operating conditions, the system creates a reference framework that simplifies subsequent temperature measurements and compensation calculations, reducing the complexity of ongoing calibration operations.
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
The method provides accurate and continuous estimation of junction temperature and health monitoring of power semi-conductors, enabling early detection of degradation and improving the reliability of power converters.
Implementation Method 1
Temperature estimation based on a voltage Von as a Temperature Sensitive Electrical Parameter (TSEP) is attractive because it applies to both IGBTs, diodes, and MOSFETs
Data Source
AI summary
The present disclosure relates to a method for estimating parameters of a junction of a power semi-conductor element comprising: •—Detecting at least one stable on-line operating condition through measurements (2, 3, 4) of Von, Ion, Tc on a semi-conductor module (1) where Ion is a current for which the on-state voltage Von of the semi-conductor is sensitive to the temperature and Tc is the temperature of the casing of said semi-conductor element; •—Measuring and storing at least one parameter set Von, Ion, Tc of said at least one stable operating condition; •—in a calculating unit (52), providing calculations for minimizing the error between a junction temperature estimation Tj of an electrical model Tj=F(Von, Ion, θelec) comprising a first set of unknown parameters θelec and another junction temperature estimation Tjmod of a loss/thermal model Tj=G(Ion, Tc, θ mod) comprising a second set of unknown parameters θ mod and obtaining at least one set of parameters θelec and at least one parameter θ mod providing minimization of said error; •—providing the calculated value of Tj with at least one of the calculated parameters sets θelec and/or θ mod and the measured Von, Ion, Tc; •—Storing the at least one parameters set θelec and/or θ mod and/or Tj.