Current Gate Driver for WBG Transistors With Two-Stage Gate Current
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Solution Overview
Problem
Wide bandgap semiconductor transistors, such as GaN and SiC, face issues with current collapse and threshold voltage shift due to gate leakage current, requiring a different driver design that addresses high gate current consumption and inefficient energy dissipation.
Innovation Solution
A current gate driver with a turn-on and turn-off circuit that transitions between two constant driving currents, initially providing a high current for rapid activation and then switching to a lower current for sustained operation, using resistors and transistors to manage gate current effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a voltage gate driver is used to drive the gate terminal, then the FET can be turned on and off, but gate leakage current causes current collapse and threshold voltage shift
Solution Approach 1:
The patent changes the driving parameter from voltage to current. The gate driver circuit provides a controlled current source that charges the gate capacitance, thereby changing the gate voltage. This current-mode driving approach allows precise control of gate charge while preventing excessive gate leakage current that causes current collapse and threshold voltage shift.
Solution Approach 2:
The patent implements a feedback mechanism where the gate driver monitors the gate voltage or current and adjusts the driving current accordingly. This feedback control ensures that the gate is charged to the required voltage level without exceeding the maximum gate charge capacity, thereby preventing current collapse phenomena while maintaining reliable switching operation.
2Reliability
If enhancement mode HEMTs are used, then better Figures of Merit are achieved, but gate leakage current injection causes current collapse and threshold voltage shift
Solution Approach 1:
The patent applies current-mode driving with controlled charge delivery to enhancement mode HEMTs, changing how the gate is excited. By providing a controlled current that charges the gate capacitance to the required voltage without excessive overcharge, the patent prevents gate leakage current injection that leads to current collapse, thereby maintaining the high Figures of Merit of enhancement mode devices.
3Reliability
If GITs are used to solve current collapse, then over-voltage ruggedness is improved, but excessive gate current is drawn making it difficult to drive
Solution Approach 1:
The patent applies current-mode driving with precise current control to GITs. By providing a controlled current source that charges the gate capacitance, the patent maintains the self-clamping over-voltage protection of GITs while reducing the excessive gate current consumption. The controlled current ensures that the gate is charged efficiently without drawing excessive current that would be difficult to drive.
Data Source
AI summary
A gate driver has a turn-on circuit and a turn-off circuit. The turn-on circuit pulls up a gate terminal of a wide bandgap (WBG) semiconductor transistor and turns on the WBG semiconductor transistor in response to a first status of an on-off control signal. The turn-off circuit pulls down the gate terminal of the WBG semiconductor transistor and turns off the WBG semiconductor transistor in response to a second status of the on-off control signal. When the on-off control signal transits to the first status, the turn-on circuit drives the gate terminal of the WBG semiconductor transistor at a first constant driving current, and later switches to a second constant driving current. The second constant driving current is lower than the first constant driving current.