Two-step thermoelectric modeling for junction temperature prediction of LED lamps

Abstract

It is very crucial to guarantee a lower junction temperature effectively for the application of Light Emitting Diode (LED) products, and also extremely useful to obtain the junction temperature accurately. In this paper, a predicted method for junction temperature of LED lamp is proposed. Numerical stimulation combined with experimental validation is carried out to evaluate the junction temperature of HP-LED lamp, with a goal to explore a novel method called two-step thermoelectric modeling. In the first step, a thermoelectric model of LED lamp is established, and then the traditional method of computational fluid dynamics (CFD) is employed for the thermal simulation on lamp level; In the second step, a detailed model of LED package is established as the second thermoelectric modeling. During the simulating process, the bottom face of LED package is regarded as a common interface to transfer the boundary condition between two isolated thermoelectric models. The results calculated from above two-step thermoelectric simulation are combined by the Interpolation Algorithm, by which a more precise junction temperature of LED lamp can be achieved. Furthermore, T3ster transient temperature analyzer is utilized to obtain the power parameters for thermoelectric modeling, and to get thermal resistance for actual junction temperature calculation with the help of thermocouple. The results show that the two-step modeling method not only can simplify the modeling process for different LED package applying different heat sink structure, but also can receive a much more precise junction temperature comparing with the traditional CFD method. The proposed method is respected to be utilized on the fast reliability assessment of LED lamp based on the relationship between junction temperature and lifetime of LED package in the future.