Power MOSFET Leakage Measurement With Temperature Extrapolation
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Solution Overview
Problem
Power MOSFETs often leak current even at a gate-to-source voltage (Vgs) of 0 V, which is difficult to measure accurately due to small leakage currents and measurement errors, and predictions of leakage current at higher temperatures are inaccurate.
Innovation Solution
A test system that applies a predetermined or variable Vgs to power MOSFETs to increase leakage current to measurable levels, using a controller to measure and predict leakage current at Vgs=0 V, and extrapolate to higher temperatures based on prior data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a voltage of 0 V is applied to the gate terminal of the power MOSFET to measure leakage current, then the leakage current reflects the actual off-state condition, but the leakage current is too small to measure accurately due to measurement errors and noise
Solution Approach 1:
The system applies a predetermined non-zero voltage to the gate terminal before measuring leakage current to increase the current to measurable levels. This preliminary action of applying voltage enhances the leakage current signal strength, making it detectable above measurement noise and error thresholds while still representing the off-state condition.
Solution Approach 2:
The system changes the gate-to-source voltage parameter from 0 V to a predetermined non-zero voltage during measurement. This parameter change increases the leakage current magnitude to a level that can be accurately measured, overcoming the limitation of measurement noise and error that plagues 0 V measurements.
2Measurement precision
If a non-zero voltage is applied to the gate terminal to increase leakage current for measurement, then the leakage current becomes measurable, but the measurement no longer accurately represents the Vgs=0 V off-state condition
Solution Approach 1:
The system uses feedback by measuring leakage current at a non-zero voltage, then using that measurement to predict the leakage current at Vgs=0 V through a relationship model. The feedback loop compares the measured current with the predicted current to ensure accuracy and reliability of the off-state representation.
Solution Approach 2:
The system introduces an intermediary prediction model that translates measurements taken at non-zero voltage into accurate predictions for Vgs=0 V conditions. This intermediary relationship allows indirect measurement while maintaining accuracy, bridging the gap between measurable conditions and the target off-state condition.
3Productivity
If leakage current is measured at room temperature, then the measurement process is simple and quick, but the prediction of leakage current at higher operating temperatures is inaccurate
Solution Approach 1:
The system performs preliminary measurements at room temperature to establish baseline leakage current characteristics. This preliminary action at the convenient room temperature enables quick measurements, and the data is then used to predict performance at higher operating temperatures through temperature-dependent relationship models.
Solution Approach 2:
The system accounts for parameter changes in leakage current as a function of temperature. By measuring at room temperature and applying temperature compensation models, the system predicts leakage current at higher operating temperatures, maintaining accuracy despite the temperature difference.
Data Source
AI summary
A system for determining the leakage current of a field effect transistor over temperature includes a metal oxide semiconductor field effect transistor (MOSFET) having first and second current terminals and a control terminal, wherein the first current terminal is coupled to a current measurement device. A switch is coupled to the control terminal and to a voltage source. The switch is configured to apply a voltage between a control terminal and a current terminal of the (MOSFET) responsive to a first signal, and apply approximately zero volts to the control terminal of the (MOSFET) responsive to a second signal.