Analysis and Reduction of Conducted EMI in Power Electronic Modules

Abstract

The phenomena causing the production and spreading of unwanted electromagnetic emissions arising from electrical or electronic devices, apparatuses and systems have been widely investigated over the last decades and reported in the relevant scientific literature. As a consequence of this, nowadays, the electromagnetic compatibility techniques, which limit the undesirable effects of these emissions, are very popular and of ever-increasing importance both in environmental and industrial contexts. The present thesis focuses on conducted electromagnetic emissions generated by power electronic modules making use of active devices operating with high switching frequency, which today are commonly utilized in a lot of sectors: aerospace, commercial, industrial, residential, telecommunication, transportation, utility systems. The onerous operating conditions of such modules, caused by high values of voltages and electric currents and very short switching times of active devices, make essential, in order to reach an efficient and economic use of materials and components, as well as a reliable and durable use of devices themselves, to carry out an accurate preliminary analysis of the mechanisms resulting in unwanted electromagnetic couplings between the various module components. Indeed, due to the unavoidable presence of parasitic inductances and capacitances and of extremely steep waveforms, electrical signals frequently originate inside the modules with high peak values and exasperated temporal dynamics, which strongly restrict the field of application of the modules themselves. For the sake of concreteness, the analysis of above described phenomena has been worked out on a power electronic module prototype made kindly available by STMicroelectronics, one of the world-leading companies in such field. After a first phase during of which have been individuated and computed the values of the most critical parasitic elements, by means of a theoretical investigation supported by suitable software tools, attention has been paid to how to reduce such values and improve the overall performance of the module. In this connection, some useful techniques to reduce significantly the undesirable emissions have been individuate and successfully applied to the prototype, so obtaining an optimized module from the electromagnetic emission point of view.