Reliability Assessment of a Redundant 12V On-board Power Supply Using Solid-state Safety Relays

The first part of this paper presents a new fault-tolerant and redundant on-board power supply concept for the supply of safety-relevant electronic control units (ECU). Solid-state mosfet-based safety switches guarantee the protection of the battery cells. Likewise, these switches are deployed to isolate and tolerate electrical system faults. Fault-tolerant and redundant power supply systems are necessary to meet the requirements of the functional safety for automated driving. ISO 26262 provides methods and metrics to ensure the functional safety of electronic systems in vehicles. These include different fault metrics for a quantitative evaluation. To determine these metrics, FMEDAs and FTAs are usually applied. Additionally, ISO 26262 mentions Markov models as a further, but less widespread, quantitative evaluation method. The Markovian approach allows the calculation of probabilistic ratios and the evaluation of any system state. Therefore, in the second part of this paper, a Markov model is developed considering a safety function of the presented power supply concept. Using this Markov model, we assess the impact of the failure rates and the diagnostic coverages of the safety function on the system reliability.