Thermal Coupling and Network Modeling for Planar Transformers

With the application of wide band gap devices in power electronics, planar transformers are preferred to further reduce the profile and manufacture cost. As a critical factor affecting the reliability, the temperature of the planar transformer is unevenly distributed and should be considered in the design phase. In this regard, a detailed thermal model enabling the temperature prediction for both the core and windings is imperative. In this paper, a thermal impedance network of the planar core is proposed considering the thermal coupling of the ambient, the core and the printed circuit board (PCB) windings. With the time-efficient computational fluid dynamics (CFD) simulation, the parameters of the network are extracted and the matrix-based model is obtained. Moreover, the model can be well coupled with the electric circuit model to perform the multi-physics optimization and simulation of the planar transformer. Finally, the proposed model is verified by both simulation and experiment results on a MHz prototype.