Dual Power Supply Paths for ASIL D Safety Systems
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Solution Overview
Problem
Modern vehicles' complex on-board electrical systems pose a risk of failure, especially for safety-relevant functions like autonomous driving, where power supply interruptions can endanger occupants and the environment, and existing safety architectures are costly and inefficient in maintaining a stable 'safe' state during faults.
Innovation Solution
A power supply system with two coupled supply paths, each connected to a safety-relevant load, using a combination of fuses and electronic circuit breakers, including MOSFETs, to ensure fault isolation and redundancy, achieving ASIL D safety level without the need for a second 12-V battery, thus reducing installation space, weight, and cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a second 12-V battery is added to provide redundant power supply for safety-relevant loads, then the reliability and safety level (ASIL D) are improved, but the device complexity, installation space, weight, and cost increase
Solution Approach 1:
The power supply system is segmented into two independent supply paths (first and second supply paths), each capable of independently powering the safety-relevant load. This segmentation allows fault isolation while avoiding the need for a second battery, as each path uses the same battery resource but with independent protection and control mechanisms.
Solution Approach 2:
Electronic circuit breakers and disconnecting elements are introduced as intermediary components between the battery and the safety-relevant load. These intermediaries provide intelligent fault detection and isolation capabilities, enabling the system to maintain safety without duplicating the entire power supply chain including the battery.
2Device complexity
If traditional fusible cut-outs are used for fault protection, then the device complexity is reduced, but the voltage stability and operational continuity during faults deteriorate due to disturbing voltage
Solution Approach 1:
Traditional mechanical fusible cut-outs are replaced with electronic circuit breakers that use electronic sensing and control mechanisms. These electronic devices can detect faults and isolate them without the mechanical interruption and voltage disturbance caused by traditional fuses, thereby maintaining voltage stability and operational continuity.
Solution Approach 2:
The electronic circuit breakers are configured to detect and respond to faults in advance, isolating them before they can cause significant voltage disturbance. This preliminary action allows the system to maintain stable operation of the safety-relevant load even when faults occur in other parts of the electrical system.
Data Source
AI summary
A power supply system for safety-relevant systems in a motor vehicle is provided that includes a first supply path and a second supply path. The first supply path includes a first connection point for a first voltage source, one or more first supply points for a safety-relevant load, and a first fuse between the first connection point and the first supply point. The second supply path is electrically coupled to the first supply path and includes a second connection point for a second voltage source, one or more second supply points for the safety-relevant load, and an electronic second fuse coupled between the second connection point and the second supply point. The safety-relevant load is capable of being electrically coupled to both the first and second supply point. Disconnecting elements are provided to isolate a fault in conformity with ASIL B.