Magnetic components for Power Electronics Operated in the Megahertz Range Using the Example of an LLC Converter

• Applicant: Professor Dr.-Ing. Joachim Böcker
• Subject Area: Electrical Energy Systems, Power Management, Power Electronics, Electrical Machines and Drives
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 467840481

Novel power electronic silicon carbide (SiC) or gallium nitride (GaN) semiconductor switches allow a considerable increase of the switching frequency due to lower switching losses, which leads to a reduction in size and costs of the magnetic components and thus of the entire converter. Currently, GaN-equipped industrial converters of ratings in the kilowatt range are operated at switching frequencies of approx. 50 to 250 kHz. It is foreseeable that switching frequencies in the megahertz range will soon be reached. At such frequencies, however, phenomena will turn up in magnetic components neglected up to now, namely the emergence of a skin effect not only in the winding but also in the core as well as resonances or standing waves within the core. Both phenomena are not welcome from the viewpoint of the conventional design of magnetic components. The project will therefore investigate which additional measures can be taken to avoid these disturbing effects as far as possible. These include the geometric shaping of the magnetic core and skilled placement of transverse and longitudinal airgaps. On the other hand, it is to be investigated whether the resonance effects in this frequency range can even be beneficially used. For example, a reactance that grows over-proportionally with frequency due to such a resonance can be used in an LLC converter to avoid the need to raise the switching frequency substantially in the crucial situation of low load and small output-input voltage ratio. This hypothesis will also be investigated in the project.

• DFG Programme: Research Grants