Half Bridge Converter Protection via Current Derivative Sensing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Wide Band Gap (WBG) power semiconductor devices, such as SiC and GaN, have reduced robustness against short-circuit faults due to higher current density, necessitating rapid and accurate detection and intervention to prevent damage.
Innovation Solution
A system and method for protecting power semiconductors in a half bridge converter that senses current derivatives to rapidly lower gate voltage during short-circuit events, using current derivative sensing means and amplifiers to control the switch and extend the switch's ability to withstand short-circuits, with filtering to reject spurious signals and ensure reliable detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If Wide Band Gap semiconductors are used to achieve faster switching capabilities, then switching losses are reduced and switching frequency is increased, but robustness against short-circuit faults is significantly reduced
Solution Approach 1:
The protection system performs preliminary detection by continuously monitoring current derivatives before a short-circuit can cause damage. The system prepares protection action in advance by detecting abnormal current trends (increasing derivatives) and triggering gate voltage reduction before the fault fully develops, thus preventing damage while allowing high switching speeds
Solution Approach 2:
The system implements feedback control by continuously sensing current derivatives and using this information to dynamically adjust gate voltage. When abnormal current increase is detected through derivative sensing, the system provides feedback to reduce gate voltage, creating a closed-loop protection mechanism that responds to actual operating conditions
2Loss of time
If traditional short-circuit detection methods are used, then detection time is sufficient for Silicon devices, but the propagation delay prevents adequate protection for Wide Band Gap devices with limited short-circuit withstand time
Solution Approach 1:
The system replaces traditional mechanical/electronic detection methods with derivative-based sensing that directly measures the rate of current change. This substitution enables ultra-fast detection by capturing the dynamic behavior of current rather than relying on threshold comparisons, reducing detection time to match the nanosecond-scale requirements of WBG devices
Solution Approach 2:
The system changes the detection parameter from absolute current thresholds to current derivatives (rate of change). This parameter transformation enables earlier detection of short-circuit conditions by identifying abnormal current trends before they reach dangerous levels, effectively reducing the detection time window required for protection
3Measurement precision
If multiple sensing means and filtering are implemented to ensure reliable detection, then detection accuracy is improved, but system complexity increases
Solution Approach 1:
The system segments the detection function into multiple specialized sensing means, each dedicated to detecting current derivatives for specific switches. This segmentation allows each sensor to be optimized for its specific function, improving detection precision while organizing complexity into modular, manageable units that can be independently configured
Data Source
AI summary
A current going through the first power semiconductor is sensed by a first and a second current derivative sensing means, the current going through the second semiconductor is sensed by a third and a fourth current derivative sensing means, when the current going through the first power semiconductor increases, the first current derivative means providing a positive voltage and the second current derivative means providing an opposite negative voltage, when the current going through the second power semiconductor increases, the third current derivative means providing a positive voltage and the fourth current derivative means providing an opposite voltage and the system reduces the voltage on the gate of the first power semiconductor if the first and third current derivative means provide voltages of same sign and reduces the voltage on the gate of the second power semiconductor if the second and fourth current derivative means provide voltages of same sign.