Gate Driver Stage Using Intermediate Gate Voltage for SiC MOSFET Stability
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Solution Overview
Problem
SiC MOSFETs in vehicle inverters experience instability due to threshold voltage increase over time and parasitic switching-on, which can lead to unintended switching and increased power losses.
Innovation Solution
A gate driver stage comprising a first and second power transistor, with a node connected to the gate terminal of a normally-off power transistor, utilizing a third voltage terminal with a voltage value between the first and second voltage values to stabilize the threshold voltage and prevent parasitic switching-on.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If SiC MOSFETs are switched between positive and negative gate voltages, then switching capability is improved, but threshold voltage instability and parasitic switching-on occur over time
Solution Approach 1:
The gate driver stage applies a third voltage value (between the first and second voltage values) to the gate terminal before the actual switching operation. This preliminary voltage application prepares the MOSFET by filling interface states with electrons, thereby stabilizing the threshold voltage before positive or negative switching voltages are applied, preventing both threshold voltage drift and parasitic switching-on
Solution Approach 2:
A third voltage value serves as an intermediary between the positive first voltage value and the negative second voltage value. This intermediate voltage level is applied to the gate terminal to stabilize the MOSFET's threshold voltage by charge compensation, allowing the MOSFET to switch between positive and negative voltages without experiencing threshold voltage instability or parasitic switching-on
2Reliability
If SiC MOSFETs are turned off at 0 V, then threshold voltage stability is improved, but parasitic switching-on occurs unintentionally
Solution Approach 1:
The gate driver stage applies different voltage values to the gate terminal depending on the specific operating condition. When turning off the MOSFET, instead of applying 0 V which causes parasitic switching-on, a third voltage value (negative but greater than the second voltage value) is applied locally at the gate terminal to maintain stability without triggering parasitic effects
Data Source
AI summary
A gate driver stage. The gate driver stage has a first power transistor including a first drain terminal and a first source terminal, with a second power transistor including a second drain terminal and a second source terminal. The first source terminal is electrically conductively connected to the second drain terminal and the first drain terminal is electrically conductively connected to a first voltage terminal. The second source terminal is electrically conductively connected to a second voltage terminal. The first voltage terminal has a first voltage value and the second voltage terminal has a second voltage value, the second voltage value being smaller than the first voltage value. A node is arranged between the first power transistor and the second power transistor, and is electrically conductively connected to a third gate terminal of a normally-off power transistor, and the third gate terminal can be controlled via the node.