Development of thermal flow simulation method for switch mode power supplies and its integration with electric circuit analysis (in the case of natural convection air cooled switch mode power supply)

This paper describes the development of a thermal flow simulation method for the design of electronic equipment. In the proposed sequence of analyses, the electric circuit analysis for estimating power loss in power semiconductor devices was integrated with the thermal analysis. The method was applied to the thermal design of a new switch mode power supply (SMPS). The analysis was carried out using a commercially available computational fluid dynamics (CFD) code. In reducing actual structural organizations of the printed circuit board (PCB) and the power semiconductor devices to simpler models, the method of experimental design (MED) was employed. Following the prescription of MED, the PCB was treated as a simple plate having the same thermal conductivity as epoxy resin, and the power semiconductor devices were modeled by hexahedral resistance network. The heat sources were a field effect transistor (FET) and a diode. Computation of power loss from the FET and the diodes is described and the accuracy of different estimation methods is discussed. The difference between measured and calculated temperature rises of the power semiconductor devices was found to be within approximately 10 K. © 2004 Wiley Periodicals, Inc. Heat Trans Asian Res, 33(8): 473–489, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20037