Analysis and Modelling of Passive device degradation for a long-term electromagnetic emission study of a DC-DC converter

International audiencePast works showed that the degradation of the passive components caused by aging could induce failures of electronic system, including a harmful evolution of electromagnetic compatibility. This paper presents the impact of the accelerated thermal aging on the electromagnetic emission (EME) of a buck DC-DC converter. The experimental analysis indicates that the aging degradation of several passive components (electrolytic capacitor and powder iron inductor) is the main source of EME evolution. Based on experimental measurement and physical analysis, the empirical degradation models of related passive devices are proposed. The overall objective of this study is to predict the electromagnetic emission evolution of a buck DC-DC converter under a thermal aging, by using these passive device degradation models. 1. Introduction The consideration of the electromagnetic robustness (EMR) of integrated circuits (IC) appeared in these last years, i.e. the evolution of parasitic emission and susceptibility to electromagnetic interferences with time for electronic devices working in harsh environments. Publications such as [1] have demonstrated that the electromagnetic emission (EME) of digital circuits and I/O buffers changes with time because of the activation of intrinsic degradation mechanisms. As presented in a few works, the simulation can be utilized to predict the long-term EMC behavior. For example, in [2], the simulation results confirmed the evolution of the electromagnetic susceptibility of a phase-locked loop before and after aging stress. A switch-mode power supply (SMPS) is selected as the device under test in this study. Because of their high power efficiency, switch-mode power supplies are widely used in electronic applications [3]. However, one main drawback of SMPS is the noise delivered by the switching activity, responsible for conducted and radiated electromagnetic emission. In this way, the management of the parasitic emission of SMPS is a frequent topic in the literature on electromagnetic compatibility (EMC). Various papers dealt with the origin and the modeling of electromagnetic emission, and also the development of design guidelines to improve these issues [4] [5]. Several recent studies presented the long-term behavior of SMPS. Due to the degradation of the electrolytic capacitor which is used to filter the output voltage of SMPS, an increase of the ripple of the output voltage of SMPS was illustrated in [6] [7]. Another consequence is the increase of electromagnetic emission, as shown in [8], where the increase of the EME of a DC-DC converter after thermal stress is associated with the degradation of output filtering passive devices, not only the capacitor but also the inductor in the output side. As a following study of [8], this paper focuses o