Dual Overcurrent Detection Circuit for Load Switch
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Solution Overview
Problem
Traditional RCB load switches fail to accurately detect overcurrents when the voltage of the output terminal is low, leading to potential damage to power NMOSFETs due to incorrect current reflection and mistaken triggering of overcurrent protection.
Innovation Solution
The implementation of a dual overcurrent detection sub-circuit system, where a first sub-circuit detects overcurrents when the output terminal voltage is greater than or equal to a preset threshold, and a second sub-circuit detects overcurrents when the voltage is less than the threshold, ensuring accurate detection and protection across various operational states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a traditional single overcurrent detection circuit is used, then the device complexity is low, but the measurement precision of overcurrent detection deteriorates at low voltage levels
Solution Approach 1:
The overcurrent detection circuit is segmented into two independent sub-circuits: a first overcurrent detection sub-circuit for detecting overcurrents when output voltage is above the threshold, and a second overcurrent detection sub-circuit for detecting overcurrents when output voltage is below the threshold. Each sub-circuit is optimized for its specific voltage range, ensuring high detection precision across all operating conditions while maintaining reasonable overall complexity.
2Reliability
If overcurrent protection is not implemented, then the device complexity is reduced, but the reliability of the power NMOSFET deteriorates due to potential overcurrent damage
Solution Approach 1:
The protection function is segmented across two specialized sub-circuits, each designed to handle specific operating conditions (high voltage and low voltage respectively). This segmentation ensures comprehensive protection coverage without requiring an overly complex unified protection circuit, thereby improving reliability while controlling complexity.
Solution Approach 2:
A voltage detection circuit acts as an intermediary between the two overcurrent detection sub-circuits, selecting which sub-circuit should be active based on the current output voltage level. This intermediary mechanism ensures that the appropriate detection circuit is engaged for each operating condition, providing reliable protection while maintaining clear circuit organization.
3Measurement precision
If a dual overcurrent detection sub-circuit system is implemented, then the measurement precision of overcurrent detection is improved across all voltage levels, but the device complexity increases
Solution Approach 1:
The detection system is divided into two specialized sub-circuits, each optimized for a specific voltage range. This segmentation allows each sub-circuit to use simpler, more efficient detection methods tailored to its operating conditions, achieving high overall precision without requiring each individual circuit to be overly complex.
Solution Approach 2:
The system dynamically switches between the first and second overcurrent detection sub-circuits based on the output voltage level detected by the voltage detection circuit. This dynamic selection ensures that the most appropriate detection circuit is always active, maintaining high measurement precision across all operating conditions while avoiding the complexity of having both circuits continuously operational.
Data Source
AI summary
The present invention provides an overcurrent detection circuit, an overcurrent detection method, a load circuit, and a portable device. The overcurrent detection circuit comprises: a first overcurrent detection sub-circuit and a second overcurrent detection sub-circuit; wherein: the first overcurrent detection sub-circuit is configured to perform overcurrent detection for a switch circuit when a voltage of an output terminal of the switch circuit is greater than or equal to a preset threshold; and the second overcurrent detection sub-circuit is configured to perform overcurrent detection for the switch circuit when the voltage of the output terminal of the switch circuit is less than the preset threshold.