Failure prediction of electrolytic capacitors in Switching-Mode Power Converters

The degradation of electrolytic capacitor is the cause of most faults of Switching-Mode Power Converters. Various tests showed that the increase of the internal Equivalent Series Resistance (ESR) of the capacitors is good indicator of their faulty state. This paper presents the equivalent model of electrolytic capacitor, analyzes several different methods of detecting the value of ESR, and proposes a new method to realize the accurate measurement of ESR. The proposed method obtains the amplitude-frequency characteristics and phase-frequency characteristics of the power systems by black-box testing. In addition, it is shown that these characteristics shifted after the deterioration of the filter capacitor. The actual value of ESR is taken out from these shifted characteristics and the equations. At the end of this paper, a series of experimental results are shown to verify the proposed prediction methodology.