SiC MOSFET Junction Temperature Estimation With Aging Compensation
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Solution Overview
Problem
Existing methods for junction temperature measurement in SiC MOSFETs are challenged by the impact of device aging on temperature-sensitive electrical parameters, requiring frequent recalibration and lacking real-time accuracy.
Innovation Solution
A circuit design that captures and transforms switching transients in SiC MOSFETs, utilizing rise and fall times to estimate junction temperature and compensate for aging effects, integrated into existing gate driver ICs with minimal disruption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If temperature-sensitive electrical parameters are used for junction temperature measurement, then cost-effectiveness and ease of integration are improved, but measurement precision deteriorates due to aging effects requiring frequent recalibration
Solution Approach 1:
The patent applies preliminary action by performing aging compensation through switching transient analysis before temperature measurement is affected by aging drift. The system characterizes aging effects in advance by analyzing changes in switching transient parameters (rise time, fall time) and uses this characterization to compensate for subsequent temperature measurements, thereby maintaining measurement precision without frequent recalibration
Solution Approach 2:
The patent introduces switching transient parameters as an intermediary between the temperature-sensitive electrical parameters and the actual temperature measurement. By using rise time and fall time of switching transients as intermediate indicators, the system can detect and compensate for aging effects, thereby improving the reliability of temperature measurements without sacrificing the ease of integration of TSEP methods
2Measurement precision
If device aging is accounted for in temperature measurement, then measurement precision is improved, but device complexity increases due to additional compensation mechanisms
Solution Approach 1:
The patent applies self-service by enabling the MOSFET device to measure its own aging effects through self-characterization of switching transient parameters. The device uses its inherent switching behavior (rise time, fall time) to detect aging drift and automatically compensates for it, eliminating the need for external complex compensation circuits or additional sensor components
Solution Approach 2:
The patent utilizes parameter changes in switching transient characteristics (rise time, fall time, oscillation frequency) as aging progresses. By monitoring these parameter changes and correlating them with aging drift, the system can dynamically adjust temperature measurement calculations to maintain precision without adding physical complexity to the device structure
3Measurement precision
If switching transients are captured for temperature estimation, then measurement precision is improved, but loss of time increases due to transient capture requirements
Solution Approach 1:
The patent applies periodic action by capturing switching transients at regular intervals during normal device operation rather than continuously. The system measures transient parameters (rise time, fall time) periodically and uses these samples to update aging compensation, thereby achieving accurate temperature estimation without requiring constant measurement that would cause excessive time loss
Solution Approach 2:
The patent uses partial action by capturing only the critical portions of switching transients that contain aging information. Instead of analyzing the entire switching cycle, the system focuses on specific parameters like rise time and fall time that are most sensitive to aging effects, reducing the time required for transient capture while maintaining measurement precision
Data Source
AI summary
An apparatus and method are provided for estimating junction temperature in a metal-oxide-semiconductor field-effect transistor (MOSFET), such as a silicon carbide (SiC) MOSFET, by capturing switching transients in a source path. A measurement circuit detects a voltage across a stray inductive element during a turn-on or turn-off phase and converts the transient into a pulse having a width proportional to a rise time or fall time. A processor determines junction temperature based on the pulse width and stored correlations between transient durations and temperature. An auxiliary switch circuit may temporarily insert a gate resistance to facilitate transient capture. Aging effects are compensated by analyzing temperature-dependent variations in rise and fall times to adjust temperature estimation over the device lifetime. The system can be integrated into gate driver circuitry for real-time monitoring without substantial disruption to normal converter operation.