Physics of Failure Models for Capacitor Degradation in Dc-dc Converters

This paper proposes a combined energy-based model with an empirical physics of failure model for degradation analysis and prognosis of electrolytic capacitors in DC-DC power converters. Electrolytic capacitors and MOSFET’s have higher failure rates than other components in DC-DC converter systems. For example, in avionics systems where the power supply drives a GPS unit, ripple currents can cause glitches in the GPS position and velocity output, and this may cause errors in the Inertial Navigation (INAV) system causing the aircraft to fly off course. We have employed a topological energy based modeling scheme based on the bond graph (BG) modeling language for building parametric models of electrical domain systems. Our current work adopts a physics of failure model (Arrhenius Law) for equivalent series resistance (ESR) increase in electrolytic capacitors subjected to electrical and thermal stresses. Experiments for capacitor degradation were conducted for collecting degradation ESR data. Parameter re-estimation for the failure model is done using the experimental data. The derived degradation model of the capacitor is reintroduced into the DC-DC converter system model to study changes in the system performance using Monte Carlo simulation methods. Stochastic simulation methods applied to the combined model help us predict how system performance deteriorates with time.