Mission profiles and hygrothermal conditions: Its effects on the reliability of a soft switching converter

摘要

Reliability predictions are routinely performed according to mission profiles, in photovoltaic applications including at least irradiance and temperature. This paper is aimed at assessing the necessity of including humidity meteorological data in the mission profile. A DC/DC soft-switching converter rated at 1 kW, and aimed at PV applications is selected as case study. Its reliability is predicted using FIDES guide, using seasonal mission profiles for eight different sites with climates ranging from tropical-humid to hot and dry. The prediction results are contrasted, assuming that the most failure-prone converters are those at the highest temperature. The results corroborate that the thermal stress factor has a large impact on the increase in the failure rate of semiconductor devices. Nevertheless, humidity also has a noticeable impact on the failure rate, contributing with 30% in the transistors, with 6% in the diodes, and in minor proportion in the passive devices. The impact of humidity is larger when it occurs simultaneously with sustained, high temperatures, and it was found that neglecting humidity might underestimate the failure rate by as much as 35% in hot, humid sites. Therefore, detailed humidity meteorological data should be included in the mission profile.