High-Side Power Switch Current Limiting for Thermal Stress Control
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Solution Overview
Problem
Smart power switches face thermal stress and potential damage due to energy dissipation during shutdowns, particularly in high-side applications, as they struggle to manage short circuits and current overloads effectively, leading to repeated energy storage and dissipation in wire harnesses.
Innovation Solution
A high-side power switch is designed with a gate driver, voltage measurement circuit, switch monitoring circuit, current limitation circuit, and controller that dynamically adjust the gate-source voltage threshold based on measured switch voltage, enabling more robust protection mechanisms by reducing the short circuit output current tripping threshold as the source-drain voltage increases, and incorporating filtering to mitigate electromagnetic interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the power switch shuts down during overload to protect against short circuits, then protection capability is improved, but thermal stress and damage risk increase due to energy dissipation in the wire harness
Solution Approach 1:
The patent measures the startup voltage during the startup sequence and stores it as a reference value before normal operation begins. This preliminary measurement allows the system to establish a baseline for detecting voltage drops during shutdown events, enabling more accurate discrimination between normal operation and fault conditions, thereby reducing unnecessary shutdowns and associated thermal stress
Solution Approach 2:
The patent dynamically adjusts the short circuit output current tripping threshold based on the measured startup voltage. By changing the threshold parameter according to the actual voltage conditions, the system adapts its protection sensitivity, allowing it to maintain protection capability while reducing false positives that would cause repeated shutdowns and thermal stress
2Measurement precision
If the short circuit output current tripping threshold is reduced to improve protection sensitivity, then detection accuracy is improved, but false triggering increases due to electromagnetic interference and voltage fluctuations
Solution Approach 1:
The patent dynamically adjusts the tripping threshold based on the measured startup voltage. The threshold is set as a function of the startup voltage, allowing the detection sensitivity to change according to operating conditions. This prevents false triggering during voltage transients while maintaining high detection accuracy for actual fault conditions
Solution Approach 2:
The system continuously monitors the output current and compares it against the dynamically adjusted threshold. The feedback mechanism allows the system to respond to actual fault conditions while adapting to normal operating variations, reducing false triggering caused by electromagnetic interference and voltage fluctuations
3Reliability
If repeated shutdowns occur during short circuit events, then protection function is maintained, but wear and damage from energy dissipation increase
Solution Approach 1:
By measuring and storing the startup voltage before normal operation, the system establishes a reference that enables accurate fault detection. This preliminary action prevents unnecessary repeated shutdowns by accurately distinguishing between normal voltage variations and actual fault conditions, thereby extending service life while maintaining protection function
Solution Approach 2:
The dynamic adjustment of the tripping threshold based on startup voltage reduces false positive shutdown events. By adapting the threshold parameter to actual operating conditions, the system maintains effective protection while minimizing unnecessary shutdowns that would cause wear and reduce service life
Data Source
AI summary
A system and method for a high-side power switch includes a gate driver configured to be coupled to a power switch, a voltage measurement circuit configured to be coupled directly to the power switch, a switch monitoring circuit configured to be coupled to the power switch, the switch monitoring circuit configured to measure an output current of the power switch, a current limitation circuit coupled to the gate driver and the switch monitoring circuit, the current limitation circuit configured to regulate gate-source voltage of the gate driver when the output current exceeds a threshold value, and a controller coupled to the current limitation circuit and the voltage measurement circuit, the controller configured to determine a mode of operation according to a startup voltage measured by the voltage measurement circuit during a startup sequence, the controller further configured to provide the threshold value to the current limitation circuit according to the mode of operation and a switch voltage measured by the voltage measurement circuit.