On-Line Diagnosis of Supply Voltage Stabilizing Capacitors in Automotive Electronic Systems

The electronic systems for future highly automated driving functions must have significantly higher reliability than today. A key to higher reliability is meaningful diagnostics to identify degraded components so they can be replaced before failure. An accurate diagnosis is very challenging due to the high variability of components that can fail. Nevertheless, in some important cases, typical circuits and a systematic procedure for diagnosis can be found. To stabilize the supply voltage and to protect the sensitive electronic systems from power supply disturbances, typical input circuits with large electrolytic capacitors are used. Degraded capacitors cannot protect the electronic systems anymore and, e.g., voltage drops or spikes might lead to system resets. Up to now, there is no practically applicable method for identifying degraded stabilizing capacitors in vehicles. This paper proposes a rule-based approach for detecting the capacitance and the equivalent series resistance of voltage stabilization electrolytic capacitors. This approach can be easily integrated into power distribution units of vehicles. The switching on voltage and current pulses are used as stimulation signals. The capacitor parameters can be estimated with an accuracy of approximately 10 %.