GaN Transistor Fault Triggered Diode Emulation Mode
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Solution Overview
Problem
Wide bandgap transistors like GaN lack an inherent body diode, leading to third quadrant operation when turned off, resulting in high power dissipation and potential damage due to unintended current flow, which complicates thermal shutdown protocols.
Innovation Solution
Implementing a fault triggered diode emulation mode that controls the transistor to allow current flow in one direction and restrict it in the opposite direction, preventing third quadrant mode and reducing power dissipation during over-temperature faults.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If wide bandgap transistors are used for high voltage power switching, then power conversion capability is improved, but third quadrant operation causes high power dissipation and potential damage
Solution Approach 1:
The patent applies inversion by detecting third quadrant operation conditions (negative voltage and positive current) and responding with an inverted control action - enabling the transistor instead of leaving it off. This counterintuitive approach allows the transistor to conduct current in the reverse direction through its channel rather than through the body diode, significantly reducing power dissipation during fault conditions.
Solution Approach 2:
The patent changes the operating parameters of the transistor by transitioning it from an off state to an on state during third quadrant conditions. By modifying the gate voltage parameter, the transistor's channel conductivity changes, enabling it to handle reverse current with much lower resistance and thus reducing power dissipation from P=I²R.
2Reliability
If the transistor is turned off during fault conditions, then current flow is restricted, but third quadrant operation causes unintended current flow and potential damage
Solution Approach 1:
The patent implements feedback by continuously monitoring the voltage and current parameters of the transistor to detect third quadrant operation conditions. When negative voltage and positive current are detected simultaneously, the control circuit responds by enabling the transistor, creating a closed-loop control system that adapts to fault conditions and prevents harmful effects.
Solution Approach 2:
The patent converts the harmful third quadrant operation into a beneficial state by enabling the transistor to deliberately conduct current in the reverse direction. What would normally be a damaging unintended current flow becomes a controlled and managed current path through the transistor channel, transforming a harmful effect into a protected operating mode.
3Reliability
If diode emulation mode is enabled during faults, then current flow direction is controlled, but device complexity increases
Solution Approach 1:
The patent applies universality by using the same transistor to perform multiple functions - both its normal switching operation and its diode emulation function during faults. The transistor's ability to conduct current in both directions when enabled allows it to serve as both a power switch and a controlled diode, eliminating the need for separate diode components and reducing overall device complexity.
Data Source
AI summary
Methods, systems, and apparatus to facilitate a fault triggered diode emulation mode of a transistor. An example apparatus includes a driver to output a control signal to a gate terminal of a transistor of a power converter; and a diode emulation control circuit to, in response to determining a fault corresponding to the transistor, enable the transistor when current flows in a direction from a source terminal of the transistor to a drain terminal of the transistor.