One of the key challenges for long-term reliability analysis of power electronic converters is to quickly estimate extensive junction temperature cycles of power semiconductor devices while fulfilling an accepted accuracy. To address this challenge, this paper proposes a novel three-pulse equivalent power loss profile. By contrast to the conventional methods of dividing the power loss equally, this paper discretizes the power loss profile based on the identified occurrences of maximum and minimum junction temperatures (i.e., thermal Characteristics). This proposed model decouples the conventional conflict between the thermal estimation accuracy and computational burdens.And it has the advantages of improving accuracy in terms of the maximum and minimum junction temperatures, and power-on time of thermal profiles, which are majorly concerned by today's lifetime models of power semiconductors. Moreover, the proposed method also helps to reduce computational burdens. The relevant variables of the thermal modeling methods are investigated. Finally, the effectiveness of the proposed method is verified through simulation and experiments, and the impact of its thermal estimation advantages on lifetime evaluation is analyzed further. 1 Index Terms-Error analysis, equivalent power loss profile, junction temperature estimation, power semiconductor devices, thermal characteristics
I. INTRODUCTIONWith increasingly pursuing higher efficiency and power density in power electronics, reliability has been becoming one of the major bottlenecks in this industry [1], [2], in particular of the high failure rate of power semiconductor devices [3]. To achieve a better performance, reliability evaluation has played an essential role in designs, manufacturing, and operation of today's power electronics [4], such as to reduce design margins [5], to plan maintenance schedules [6], [7] etc.