Overcurrent Protection Circuit With Dynamic Blanking Time
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Solution Overview
Problem
Overcurrent protection circuits struggle with load currents having high peak to average ratios, leading to either undetected damage or false tripping, as existing solutions either set a fixed blanking time independent of overcurrent magnitude or fail to differentiate between varying overcurrent conditions.
Innovation Solution
An overcurrent protection circuit that modulates blanking time based on the magnitude of the overcurrent, with the blanking time inversely proportional or proportional to the square of the magnitude exceeding the predefined set current, mimicking the behavior of traditional fuses and allowing small overcurrents to persist longer while large ones are quickly addressed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a fixed blanking time is used independent of overcurrent magnitude, then the circuit complexity is reduced, but the reliability deteriorates due to false tripping on peak currents and undetected damage on sustained overcurrents
Solution Approach 1:
The blanking time is made dynamic by modulating it based on the magnitude of the overcurrent condition. The circuit transitions from a fixed blanking time to a variable blanking time that adapts to the severity of the overcurrent, thereby improving detection reliability without requiring complex additional circuitry.
Solution Approach 2:
The blanking time parameter is changed based on the overcurrent magnitude. By modulating the blanking time parameter in response to different overcurrent conditions, the circuit achieves better reliability in distinguishing between transient peak currents and sustained damaging overcurrents.
2Reliability
If the blanking time is shortened to quickly address large overcurrents, then the reliability improves for severe faults, but false tripping increases on legitimate peak currents
Solution Approach 1:
Different blanking time durations are applied locally based on the magnitude of the overcurrent condition. Small overcurrents receive longer blanking times to avoid false tripping, while large overcurrents receive shorter blanking times for quick protection, achieving both goals simultaneously.
3Object-affected harmful factors
If the blanking time is lengthened to allow peak currents, then false tripping is reduced, but damage from sustained overcurrents goes undetected
Solution Approach 1:
The blanking time dynamically adjusts based on the overcurrent magnitude. For small overcurrents that may be legitimate peaks, the blanking time is extended to prevent false tripping. For large sustained overcurrents, the blanking time is shortened to ensure quick detection and protection, thus maintaining both reliability aspects.
Data Source
AI summary
An over current protection circuit arranged for providing an over current signal, the over current protection circuit includes a compare stage arranged for determining that a blanking time value is higher than a predefined reference value, an output stage arranged for outputting the over current signal based on the determination, a blanking time stage arranged for generating the blanking time value, and the blanking time stage is arranged to start generating the blanking time value upon a load current exceeding a predefined set current, the blanking time stage is further arranged to modulate the blanking time value based on a magnitude in which the load current exceeds the predefined set current.