Power Module Junction Temperature Modeling for Dynamic Drive Conditions
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Solution Overview
Problem
Existing methods for estimating the junction temperature of power modules, such as using NTC thermistors and thermal models, fail to accurately account for changes in input voltage and switching frequency, leading to inaccurate predictions of junction temperature and durability life, and result in reduced output power due to thermal management limitations.
Innovation Solution
A method that calculates predicted temperature change values for power semiconductor devices based on power loss, thermal resistance, and coolant flow rate, applying different time constants to reflect the influence of heat generation from both the device and neighboring devices, thereby deriving a more accurate final junction temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If NTC thermistor is used to detect junction temperature, then temperature detection is implemented, but measurement precision deteriorates because thermal impedance is significantly different from the power semiconductor device and does not compensate for voltage and frequency changes
Solution Approach 1:
The patent introduces a thermal model as an intermediary between the power semiconductor device and the temperature measurement system. This thermal model compensates for the thermal impedance mismatch by calculating junction temperature based on case temperature, power loss, and thermal resistance parameters, rather than directly measuring with an NTC thermistor that has significantly different thermal impedance characteristics
Solution Approach 2:
The patent changes the measurement parameters from direct NTC voltage detection to a calculated approach using power loss (Ploss), thermal resistance (Rth), and case temperature (Tc) parameters. The junction temperature is derived through the equation Tj = Tc + Ploss × Rth, which accounts for voltage and frequency changes that affect power loss
2Measurement precision
If thermal model is used to estimate junction temperature, then measurement precision improves by considering voltage, current, and switching frequency, but reliability deteriorates when temperature increase trend is not accurately reflected during dynamic operation
Solution Approach 1:
The patent applies different time constants to different sections of the temperature increase curve to dynamically adapt the thermal model to changing operating conditions. A first time constant is applied to the initial temperature increase section while a second time constant is applied to the saturation section, allowing the system to accurately track temperature dynamics during transient operations
Solution Approach 2:
The patent performs preliminary classification of the temperature increase curve into distinct sections (initial increase and saturation) before applying the appropriate time constant to each section. This preliminary action enables the system to select the correct time constant based on the current operating phase, improving prediction accuracy during dynamic operation
3Reliability
If conservative temperature estimation is applied to ensure device safety, then reliability improves, but productivity deteriorates due to excessive temperature derating logic reducing output power
Solution Approach 1:
The patent implements a feedback mechanism that continuously monitors the accuracy of temperature predictions by comparing estimated junction temperature with actual measurements. Based on this feedback, the system adapts the time constants and thermal model parameters to optimize both reliability and productivity, avoiding excessive derating while ensuring device safety
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
This approach improves the accuracy of junction temperature measurement, enhances the prediction of power module durability, and increases output power by accurately reflecting temperature changes under various driving conditions, reducing the impact of excessive temperature derating logic.
Implementation Method 1
the NTC detects voltage change using heat generated from the power semiconductor device when a junction temperature increases
Data Source
AI summary
A system and method for measuring a junction temperature of a power module junction temperature are provided. The method is capable of improving accuracy of temperature measurement by more accurately applying temperature change in a junction temperature rising section, capable of more accurately predicting durability life of a power module, and capable of increasing output power of the power module.