Junction Temperature Measurement via Tail Current Charge
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Solution Overview
Problem
Existing methods for measuring the junction temperature of semiconductor components, particularly in power electronics, are impractical due to low on-state voltage and are not precise enough for normal operational conditions.
Innovation Solution
A method that measures the quantity of charge evacuated by the tail current in GTO thyristors or IGBT transistors during the blocking phase, using a characteristic function established through successive tests at different temperatures, allowing for accurate junction temperature determination without direct voltage measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the on-state voltage measurement method is used to determine junction temperature, then the measurement can be performed during component operation, but the measurement is practically impossible to implement due to the very low on-state voltage compared to blocked voltage
Solution Approach 1:
The patent introduces the tail current as an intermediary quantity to measure junction temperature. Instead of directly measuring the difficult-to-detect on-state voltage, the method uses the tail current (which is easier to measure) as a mediator that correlates with temperature. The tail current is measured during the blocking phase, and through calibration curves, this measurement is converted to temperature information, solving the problem of measuring temperature during operation without requiring direct voltage measurement across the junction.
2Ease of operation
If leakage current measurement method is used to measure junction temperature, then the component can be measured in normal operation, but the measurement precision is insufficient for accurate temperature determination
Solution Approach 1:
The patent focuses on measuring the tail current parameter, which represents the quantity of charge evacuated by the component during blocking. This parameter changes with temperature in a characteristic way that can be captured through calibration curves. By measuring this specific parameter (tail current charge quantity) and using temperature-dependent calibration data, the method achieves both ease of measurement during normal operation and sufficient precision for accurate temperature determination.
3Measurement precision
If direct voltage measurement across junction terminals is performed, then temperature can be determined from the measured voltage, but the measurement requires specialized equipment and is not practical on real equipment
Solution Approach 1:
The patent uses the tail current as an intermediary measurement that can be obtained with standard equipment during normal operation. Instead of requiring specialized equipment to measure the small on-state voltage directly, the method measures the tail current (which is easier to detect with conventional instruments) and converts this to temperature information through calibration, thereby reducing equipment complexity while maintaining measurement capability.
4Measurement precision
If sensor implantation is used to measure junction temperature, then accurate temperature measurement is achieved, but the thermal integrity of the component is compromised
Solution Approach 1:
The patent employs the component's own electrical characteristics (tail current during blocking) as the measurement probe. The component measures itself through its inherent electrical behavior during normal operation, eliminating the need for external sensors that would be implanted into the component. This self-measurement approach maintains thermal integrity while providing accurate temperature data through the characteristic charging behavior of the junction during blocking phases.
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 provides a precise and measurable AC junction temperature without requiring sensor implantation, maintaining thermal integrity and offering increased accuracy by correlating charge quantity with temperature.
Implementation Method 1
said quantity being representative of the quantity of charge (Q tail) evacuated by the component by the tail current flowing in the electronic semiconductor component when the latter is blocked
Implementation Method 2
the step of determining the junction temperature comprises a step of implementing a characteristic function of the component previously established giving the junction temperature as a function of the quantity of charge measured
Data Source
Figure 1~2
Figure 3~5
AI summary
The method involves measuring an electrical quantity on an electronic component e.g. diode, by using a current probe (20), during a predetermined operating phase of the component. A junction temperature of the component is determined, by a junction temperature determination unit (28), from the electrical quantity. The electrical quantity represents quantity of charges evacuated by the component during a blocking to be counted from a predetermined instant at which a linear variation of current stops. An independent claim is also included for a device for measuring junction temperature of an electronic component.