Dual-Threshold Overcurrent Detection Circuit for Wire Harness Protection
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Solution Overview
Problem
Conventional switch circuits with overcurrent detection functions struggle to differentiate between rush currents and actual overcurrents when multiple load elements are activated at arbitrary time points, leading to potential misclassification of rush currents as overcurrents.
Innovation Solution
A switch circuit with a dual-threshold overcurrent detection system, featuring a first and second overcurrent threshold, where the second threshold is lower than the first, and corresponding time periods for each, to distinguish between rush currents and overcurrents, with a control circuit deactivating the switching element upon detection of an overcurrent.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single overcurrent threshold is used for detection, then the detection simplicity is maintained, but rush currents are misclassified as overcurrents when multiple load elements are activated
Solution Approach 1:
The single overcurrent threshold is segmented into multiple thresholds (first overcurrent threshold and second overcurrent threshold) with different values. The first threshold is set higher to avoid misdetecting rush currents, while the second threshold is set lower to ensure accurate overcurrent detection. This segmentation allows the system to distinguish between temporary rush currents and sustained overcurrent conditions.
Solution Approach 2:
The detection system dynamically switches between different thresholds based on operational conditions. When a rush current is detected (current exceeds first threshold), the system temporarily adjusts the detection threshold to prevent false positives. This dynamic adaptation enables accurate detection across varying operational states without requiring complex circuit redesign.
2Reliability
If the overcurrent threshold is set high to avoid detecting rush currents, then false detection is reduced, but actual overcurrents may be missed
Solution Approach 1:
The threshold segmentation creates a hierarchical detection structure where the first (higher) threshold filters out rush currents and the second (lower) threshold captures actual overcurrents. This multi-level approach ensures both high reliability by avoiding false positives and high sensitivity by maintaining a lower detection threshold for sustained currents.
Solution Approach 2:
The first overcurrent threshold acts as an intermediary filter between the raw current signal and the final overcurrent determination. It mediates by temporarily raising the detection bar during rush current events, allowing the system to then use the lower second threshold with confidence that rush currents will not trigger false alarms.
3Adaptability or versatility
If multiple load elements are connected to a single wire harness, then system integration is simplified, but rush current detection becomes unreliable
Solution Approach 1:
The detection system dynamically adapts to the activation patterns of multiple load elements by automatically adjusting thresholds based on detected current profiles. When activation causes a rush current pattern, the system dynamically raises the first threshold temporarily, then returns to the lower second threshold for ongoing monitoring. This dynamic behavior maintains accurate detection across arbitrary activation sequences.
Solution Approach 2:
The system changes detection parameters (threshold values) based on the operational context of multiple load elements. By switching between different threshold parameters depending on the detected current pattern, the system maintains measurement accuracy regardless of which load elements are activated and when, enabling reliable operation with integrated wire harness configurations.
Data Source
AI summary
A first overcurrent detecting circuit outputs a first time-up signal when a time period, in which an electric current flowing into the wire harness is greater than the first threshold, reaches a first duration time, which corresponds to a first threshold. A second overcurrent detecting circuit outputs a second time-up signal when a time period, in which an electric current flowing into the wire harness is greater than the second threshold, reaches a second duration time, which corresponds to a second threshold. The second threshold is less than the first threshold. The second duration time is longer than the first duration time. A determination circuit determines that an overcurrent flows into the wire harness and cause a control circuit to deactivate the switching element when inputting at least one of the first and second time-up signals.