Current Mirror Gate Leakage Measurement for SiC MOSFETs
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Solution Overview
Problem
Existing methods for measuring gate leakage current in SiC MOSFETs are inefficient and prone to errors due to fluctuations in gate leakage current and dependence on duty cycle, making real-time monitoring challenging.
Innovation Solution
An apparatus utilizing a current mirror connected to the gate of a MOSFET, with a sensing resistor on the output current path, allows for direct measurement of gate leakage current, independent of duty cycle, and includes a bypass switch and discharging circuit to improve switching speed and sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a sensing resistor is used to directly measure gate leakage current, then measurement precision is improved, but the method is only suitable for MOSFETs close to end of life when leakage current reaches extreme values
Solution Approach 1:
The patent introduces a current mirror as an intermediary device that copies the gate leakage current to a separate measurement path. This allows the sensing resistor to measure the mirrored current instead of the original gate leakage current directly, enabling accurate measurement across different MOSFET conditions without being limited to end-of-life devices only
2Measurement precision
If capacitors are employed to collect charge from leakage current, then leakage current can be indirectly determined, but measurement convenience deteriorates due to calibration requirements and duty cycle considerations
Solution Approach 1:
The patent replaces the capacitor-based charge collection method with a current mirror-based direct current measurement system. This substitution eliminates the need for calibration and duty cycle considerations, as the current mirror provides a direct proportional relationship between the gate leakage current and the measurement signal, significantly improving ease of operation
3Ease of operation
If voltage across gate resistor is measured to indirectly determine leakage current, then measurement can be performed, but measurement precision worsens due to various drawbacks in the method
Solution Approach 1:
The patent uses a current mirror as an intermediary to transfer the gate leakage current to a dedicated measurement path with a sensing resistor. This provides a direct current measurement through the sensing resistor, eliminating the indirect voltage measurement across the gate resistor and significantly improving measurement precision while maintaining ease of operation
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
The apparatus provides high sensitivity and rapid measurement of gate leakage current, reducing measurement time and improving accuracy by maintaining a nearly constant voltage across the current mirror, regardless of the gate leakage current magnitude.
Implementation Method 1
An apparatus utilizing a current mirror connected to the gate of a MOSFET, with a sensing resistor on the output current path, allows for direct measurement of gate leakage current
Implementation Method 2
The sensing resistor is located on an output current path of the current mirror
Data Source
AI summary
An apparatus for measuring a gate leakage current of a MOSFET. The apparatus includes a current mirror adapted to be connected to a gate of a MOSFET, a gate driver adapted to generate a driving signal for the MOSFET, and a sensing resistor connected to the current mirror. An input current path of the current mirror is adapted to receive a gate leakage current of the MOSFET. The current mirror provides a high sensitivity of the measurement because the voltage across the current mirror is nearly constant, which therefore caters for different situations no matter if the gate leakage current is high or low.