Converter Transistor Junction Temperature Estimation During Switching
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Solution Overview
Problem
Existing methods for estimating semiconductor junction temperatures in power electronics converters are inaccurate and non-real-time, leading to suboptimal operation and potential safety issues due to the inherent time lag in traditional thermistor-based measurements and the inability of indirect methods to provide reliable instantaneous temperature readings.
Innovation Solution
A method involving a power electronics converter with a controller, current sensor, temperature sensor, and junction temperature measurement module that measures the rate of change of current during a switching period to estimate junction temperature, using a look-up table to correlate this data with actual temperatures, thereby providing real-time and accurate junction temperature measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If NTC thermistor is used to measure junction temperature, then temperature measurement is possible, but time lag occurs and real-time measurement is not achieved
Solution Approach 1:
The patent replaces the physical NTC thermistor measurement system with an electrical measurement system that uses threshold voltage of the transistor during switching transitions. This substitution eliminates the thermal mass and response time limitations of physical temperature sensors, enabling instantaneous junction temperature estimation without time lag.
Solution Approach 2:
The patent introduces the threshold voltage as an intermediary parameter that correlates with junction temperature. By measuring the threshold voltage during switching transitions and using calibration data to map this voltage to temperature, the system achieves real-time temperature estimation without directly measuring temperature physically.
2Loss of time
If indirect methods are used to estimate junction temperature, then real-time estimation is possible, but measurement accuracy is insufficient
Solution Approach 1:
The patent performs preliminary calibration to establish the relationship between threshold voltage and junction temperature before actual operation. This pre-established calibration data enables accurate real-time temperature estimation during converter operation without requiring complex real-time calculations or models.
Solution Approach 2:
The patent changes the measurement parameter from direct physical temperature measurement to electrical threshold voltage measurement. This parameter transformation enables real-time measurement while maintaining accuracy through the calibrated relationship between voltage and temperature.
3Productivity
If converters are operated closer to thermal limits to increase power output, then productivity increases, but reliability decreases due to safety risks
Solution Approach 1:
The patent implements real-time feedback of junction temperature to the control system. This feedback enables the controller to monitor temperature continuously and adjust operating parameters to prevent exceeding thermal limits, allowing the converter to operate safely close to its thermal capabilities without compromising reliability.
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 real-time, accurate estimation of junction temperatures, allowing for safer and more efficient operation of power electronics converters by enabling operation closer to thermal limits and facilitating timely response to fault conditions, while also aiding in health monitoring and maintenance.
Implementation Method 1
the junction temperature measurement module measuring a threshold voltage of the transistor from the current signal and a temperature of the transistor from the temperature sensor during a switching period of the transistor
Data Source
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AI summary
The disclosure relates to estimation of junction temperatures of transistors in a power electronics converter. Example embodiments include a method of calibrating an electrical power system (300), the electrical power system (300) comprising: a power electronics converter (304) configured to convert between first and second voltage supplies, the converter (304) comprising a plurality of semiconductor switches (3031-6), each semiconductor switch (3031-6) comprising a transistor (S1-6); a controller (309) configured to provide switching signals (VGS1-6) to each of the semiconductor switches (3031-6); a current sensor (311) arranged to measure current through the converter (304) to one of the first and second voltage supplies; a temperature sensor (314) arranged to measure a temperature of one or more of the semiconductor switches (3031-6); and a junction temperature measurement module (710) configured to receive a current signal from the current sensor (311) and a temperature signal from the temperature sensor (314), the method comprising: the controller (309) providing a gate switching signal to the transistor (S1-6); the junction temperature measurement module (710) measuring a threshold voltage of the transistor (S1-6) from the current signal and a temperature of the transistor (S1-6) from the temperature sensor (314) during a switching period of the transistor (S1-6); and the junction temperature measurement module (710) updating a stored calibration defining a relationship between a rate of change of current and an estimated junction temperature (Tj1-6) of the transistor (S1-6).