Dynamic Overcurrent Threshold Switching for Instantaneous Load Current
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Solution Overview
Problem
Conventional overcurrent protection circuits struggle to simultaneously secure instantaneous current and provide suitable overcurrent protection for loads with varying current requirements, particularly in in-vehicle ICs that need to comply with ISO26262 standards.
Innovation Solution
An overcurrent protection circuit with a threshold generator that switches between two set values for the overcurrent detection threshold based on a mask period and a reference value, allowing for dynamic adjustment of the protection threshold to accommodate different load conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single overcurrent set value is used in conventional overcurrent protection circuits, then overcurrent protection is provided, but instantaneous current required by capacitive loads cannot be secured
Solution Approach 1:
The overcurrent detection threshold is made dynamic by switching between a first set value (higher threshold) and a second set value (lower threshold) based on operational conditions. The threshold generator selectively outputs one of the two set values according to a threshold control signal, allowing the protection circuit to adapt its sensitivity to match different operational phases - permitting high instantaneous current during startup while providing strict protection during normal operation.
Solution Approach 2:
The detection threshold parameter is changed between two discrete values (first set value and second set value) depending on the operational state. During startup or transient conditions, the higher first set value allows large instantaneous currents without false tripping. During steady-state operation, the lower second set value provides appropriate overcurrent protection. This parameter switching resolves the contradiction between protection sensitivity and instantaneous current capability.
2Reliability
If the overcurrent detection threshold is set low for protection, then overcurrent protection is improved, but false tripping occurs during normal operation of capacitive loads requiring large instantaneous current
Solution Approach 1:
The detection threshold dynamically adapts to operational conditions through selective switching between two set values. During startup phases when capacitive loads draw high instantaneous current, the higher first set value prevents false tripping while maintaining protection capability. During normal operation, the lower second set value provides accurate overcurrent detection. This dynamic adjustment eliminates false tripping while preserving detection precision.
Solution Approach 2:
The system prepares two pre-configured threshold values (first set value and second set value) in advance, each optimized for different operational phases. The threshold generator is pre-configured to select the appropriate threshold based on the operational state, so that when capacitive load startup occurs, the higher threshold is already in place to prevent false tripping, and when normal operation begins, the lower threshold is ready for accurate protection.
3Device complexity
If a fixed overcurrent set value is used, then circuit design is simplified, but the circuit cannot accommodate varying current requirements of different loads
Solution Approach 1:
Rather than designing completely separate protection circuits for different load types, the invention implements a dynamic threshold selection mechanism within a single protection circuit. The threshold generator switches between two set values based on operational conditions, allowing the same circuit to accommodate both capacitive loads requiring high instantaneous current and resistive loads requiring strict protection, thereby maintaining load compatibility while controlling circuit complexity.
Solution Approach 2:
The overcurrent protection circuit achieves multi-functionality by incorporating a threshold generator that can select between two different set values. This single circuit structure can serve multiple load types with different current characteristics - capacitive loads during startup, resistive loads during normal operation, and various intermediate conditions - eliminating the need for multiple specialized protection circuits while enhancing overall adaptability.
Data Source
AI summary
In order both to accommodate instantaneous current as well as overcurrent protection in accordance with the load, an overcurrent protection circuit has: a threshold value generation unit that, in accordance with a threshold value control signal, switches between setting an overcurrent detection threshold value to a first set value (∝ Iref) and a second set value (∝ Iset) lower than the first set value; an overcurrent detection unit that compares a sense signal in accordance with the current being monitored and the overcurrent detection value and generates an overcurrent protection signal; a reference value generation unit that generates a reference value (∝ Iset) in accordance with the seconds set value; a comparison unit that compares the sense signal and the reference value, and generates a comparison signal; and a threshold value control unit that monitors the comparison signal, and generates a threshold value control signal.