Characterizing EMI-filters’ Deviations caused by the Capacitors Ageing based on Complex Impedance Analysis

EMI (electromagnetic interference) filters are widely used in electronic devices and systems. They have considerable effects on the Electromagnetic Compatibility (EMC) performance of circuits. However, after long-term operation, the filters can exhibit severe degradation due to the intrinsic ageing mechanism and external thermal and electrical stresses. To be specific, the performance of the internal capacitors, typically represented by their capacitance value and equivalent series resistance, will largely deviate. These issues weaken the filters’ functionality, the service life as well as their EMC compliance. However, other parasitic parameters, like parasitic inductance, dielectrics insulation which are necessary for evaluating the performance, are usually neglected. In this study, the deviations of the EMI filters cause by the ageing of the capacitors are analyzed based on complex impedance analysis. The ageing characteristics of the filters with respect to the capacitor’s deviations, where nearly all parasitic parameters were taken into account, are identified by conducting an electrical overstress accelerated ageing test.