High-Side MOSFET Protection via Gate-Source Derivative Detection
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Solution Overview
Problem
Current methods for protecting high-side MOSFET transistors in powertrain ECUs from high energy events, such as short circuits or battery faults, are either cost-prohibitive due to the need for sense resistors and voltage monitoring circuits or fail to detect events during the transistor's switching period due to the nature of MOSFETs.
Innovation Solution
Monitoring the derivative of the gate-to-source voltage with respect to time and using a timer block to detect high energy events after an initial blank time, allowing for early detection and protection of the transistor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a sense resistor and voltage monitoring circuit are used to detect high energy events, then detection accuracy is improved, but cost and weight increase
Solution Approach 1:
The invention extracts the detection function from complex external circuits (sense resistors and voltage monitoring circuits) and integrates it into the microcontroller unit by utilizing existing internal ADC resources. The ADC samples voltage at the transistor gate, source, and drain nodes, and software calculates energy events, eliminating the need for separate sense resistors and monitoring circuits while maintaining detection accuracy.
Solution Approach 2:
The ADC resource in the microcontroller is made multi-functional by using it for both normal operational voltage measurements and high energy event detection. The same ADC hardware and sampling infrastructure serve dual purposes: monitoring transistor operation during normal switching and detecting abnormal high energy conditions, thereby eliminating dedicated detection hardware.
2Device complexity
If drain to source node voltage is monitored to detect high energy events, then cost is reduced, but detection capability during switching period is lost
Solution Approach 1:
The detection approach is segmented into multiple voltage node measurements (gate, source, and drain nodes) rather than relying on a single drain-to-source measurement. By sampling voltages at multiple nodes independently and calculating energy based on these segmented measurements, the system can detect high energy events during the switching period when drain-to-source voltage alone would be insufficient.
Solution Approach 2:
The system performs preliminary sampling of voltage at the gate, source, and drain nodes during the switching period before a high energy event fully manifests. By continuously monitoring these nodes and calculating instantaneous power dissipation in real-time during switching transitions, the system can detect emerging high energy events early, enabling protective action before damage occurs.
3Reliability
If real-time voltage monitoring is performed during switching period, then detection capability is improved, but processing complexity increases
Solution Approach 1:
The system implements feedback by continuously sampling voltage at the transistor nodes, calculating instantaneous power dissipation, comparing it against predefined thresholds, and triggering protective responses when high energy events are detected. This closed-loop feedback mechanism enables real-time detection during switching while keeping processing manageable through algorithmic efficiency and threshold-based decision logic.
Data Source
AI summary
A method and apparatus for detecting a high energy event in a transistor includes performing the steps of: monitoring a gate to source voltage of a transistor during transistor start up, continuously determining a derivative of the monitored gate to source voltage with respect to time, and detecting a high energy event when the derivative of the gate to source voltage exceeds a predetermined threshold.