Experimental characterization of DELPHI Compact Thermal Model for surface-mounted soft magnetic composite inductor

Abstract

The latest low-profile high-power inductors, used in DC-DC converter to power an assortment of applications, are going endlessly smaller and submitted to larger amount of current. This surface-mounted magnetic component is commonly constructed using a wound copper coil which is over-moulded in a Soft Magnetic Composite (SMC) based on an iron-resin material mixture. The performances of that high-power density device are closely depending on the coupled interaction of magnetic phenomenon, joule effect and thermal behaviour, which are difficult to apprehend at board level simulation. In order to better characterize the behaviour of high-power inductor devices, a set of coupled electromagnetic and thermal simulations were performed on the case of an industrial demonstration electronic board. Further, the influence of surrounding active electronic components upon the acceptable temperature rise of the inductor parts has been investigated. The numerical simulations were completed by electrical characterizations and thermal measurements of the test vehicle for various operating conditions with the purpose to establish a more realistic thermal model of the inductor device. The agreement of the fine detailed model with experiment results is quite relevant: the divergence is lower than 10%. Moreover, the present study highlights the electromagnetic phenomena encountered by SMC inductor devices and their influence on the temperatures of the iron-based core and copper-based coil. This analysis confirms the conservative assumption that the magnetic and electrical losses can be uniformly applied to the core and coil volumes. The approach proposed in 2013, for the generation of a relevant Compact Thermal Model dedicated to SMC inductor devices, according with DELPHI methodology, remains valid.