Power Module Thermal Impedance Monitoring via Junction Temperature Delay
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Solution Overview
Problem
Existing thermal impedance monitoring methods for power modules are inadequate in identifying layer-specific degradation in power modules due to the need for precise power dissipation measurement and reliance on steady-state thermal conditions, which is challenging in power converters.
Innovation Solution
A lock-in thermography technique is applied in transient states to monitor thermal impedance by measuring the time duration between maximum and minimum junction temperatures during asymmetrical loss cycles, allowing for layer-specific degradation detection without requiring power dissipation measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If steady-state thermal conditions are used for thermal impedance monitoring, then measurement accuracy is improved, but the complexity of measurement setup and requirement for precise power dissipation measurement increases
Solution Approach 1:
The patent transitions from steady-state thermal conditions to transient thermal conditions for measurement. By utilizing the transient thermal response during normal converter operation, the method eliminates the need for precise power dissipation measurement and complex steady-state setup, while maintaining measurement accuracy through analysis of temperature evolution over time.
Solution Approach 2:
The method utilizes the converter's normal operating thermal cycles to perform self-diagnosis. The thermal impedance monitoring is conducted during regular operation without requiring separate measurement equipment or interrupting normal function, allowing the system to monitor its own thermal health using existing operational data.
2Measurement precision
If steady-state thermal conditions are required for monitoring, then thermal impedance can be measured, but normal converter operation must be interrupted
Solution Approach 1:
The patent enables continuous thermal impedance monitoring during normal converter operation. By analyzing transient thermal responses during regular switching cycles, the system maintains uninterrupted operation while continuously assessing thermal interface degradation, eliminating the need to pause or interrupt converter function for diagnostic purposes.
3Measurement precision
If precise power dissipation measurement is required for thermal impedance monitoring, then measurement accuracy is improved, but sensor complexity and measurement difficulty increase
Solution Approach 1:
The patent extracts and utilizes only the transient thermal response component from the overall thermal behavior during switching cycles. By focusing on the temperature evolution pattern rather than absolute temperature values or power dissipation magnitude, the method isolates the thermal impedance information from the complex power measurement requirements, eliminating the need for precise power sensing.
Solution Approach 2:
The transient thermal response serves as an intermediary that links converter operation to thermal impedance information. Instead of directly measuring power dissipation and thermal impedance separately, the method uses the transient temperature evolution during switching as a mediator that contains embedded thermal impedance information, simplifying the measurement chain.
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 method accurately identifies and quantifies thermal impedance degradation in power modules by analyzing time delays in temperature changes, independent of power loss estimation, reducing sensor complexity and improving accuracy.
Implementation Method 1
the semiconductor dissipates an asymmetrical loss between two half cycles of an AC frequency f of the AC current
Implementation Method 2
a power module comprising at least a semiconductor die attached to a material stack-up of layers for its thermal dissipation
Data Source
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AI summary
Thermal impedance monitoring process for a power module of a power converter used for transforming DC current to AC current, or vice-versa, where the semiconductor dissipates an asymmetrical loss between two half cycles of an AC frequency f of the AC current, said power module comprising at least a semiconductor die attached to a material stack-up of layers for its thermal dissipation and/or electrical connections, said process comprising: - sampling and measuring a signal relating to the junction temperature Tj of said semiconductor die at a frequency higher than twice said AC frequency of said AC current, - calculating a time duration Δt= tTjmax- tTjmin between a moment tTjmax, where said junction temperature of said semiconductor die is at a maximum value, and a moment tTjmin, where said junction temperature is at a minimum value, in one period of said AC current, and storing said time duration Δt in a memory, - repeating said sampling and measuring said signal and said calculating said time duration at different times tx=t0 to tm during the operating life of the power module to provide a series of time durations Δtt0 to Δttm and comparing said time durations Δtt0 to Δttm values for monitoring an evolution of said time duration Δt to determine an evolution of degradation of the thermal impedance of said power module.