Squib Driver High-Side Protection for Battery Short Faults
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Solution Overview
Problem
Airbag safety systems face challenges in protecting squib loop drivers from faults such as short circuits to ground, shorted loads, and battery voltage, which can lead to improper deployment and damage to the drivers.
Innovation Solution
The implementation of protection circuits, including comparators and delay timers, within the squib driver circuit to detect voltage and current limits, and generate signals to disable the power transistors in case of faults, allowing controlled deployment and preventing driver damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the squib driver attempts deployment function continuously, then the deployment reliability is improved, but the drivers may be damaged by system faults such as short circuits
Solution Approach 1:
The protection circuit performs preliminary detection of fault conditions (short circuits to ground, shorted loads, battery voltage) before the deployment function is activated. By detecting these harmful conditions in advance and disabling the power transistors beforehand, the circuit prevents driver damage while allowing normal deployment attempts to proceed.
Solution Approach 2:
The protection circuit applies counter-action by detecting fault conditions and generating disable signals to prevent the harmful effect of short circuits from damaging the drivers. The comparator and delay timer work together to counteract potential damage by terminating the deployment function when faults are detected.
2Reliability
If protection circuits with comparators and delay timers are added, then driver protection is improved, but the device complexity increases
Solution Approach 1:
The protection circuit integrates multiple functions (voltage comparison, timing delay, signal generation) into a unified circuit block that works together with the existing squib driver. The comparator, delay timer, and logic gates are combined to form a cohesive protection mechanism that adds functionality without requiring entirely separate systems.
3Reliability
If the deployment function is terminated early due to fault detection, then driver damage is prevented, but the deployment time is reduced
Solution Approach 1:
The protection circuit continuously monitors the squib loop conditions during the deployment attempt and provides feedback to the control logic. The delay timer allows the deployment to proceed for a predetermined time before termination, ensuring that normal deployments are not prematurely interrupted while still providing protection against persistent faults.
Data Source
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AI summary
A squib driver circuit for deployment of an active safety restraint in a vehicle. The squib driver circuit may include a high side protection circuit. The high side protection circuit may include a comparator circuit to compare the input voltage to a reference voltage and activate a timer in response to the input voltage exceeding the reference voltage, the timer generating a disable signal to disable the high side driver after a predetermined period of time The high side protection circuit may disable the high side driver after a short is detected and elapse of the predetermined period of time. The squib driver circuit may be formed on a single chip.