Matthieu BELEY will defend his PhD on Dec. 10th, 2025 in the morning.
Place : Amphitheatre 203 in the W1 building of École Centrale de Lyon in Ecully
Jury :
Rapporteurs :
M. Ghislain DESPESSE, Directeur de recherche, CEA-LETI
Mme. Audrey MARTIN, Maître de conférences HDR, Université de Limoges
Examinateurs :
Anne-Sophie DESCAMPS BACQUET, Maître de conférences HDR, Université de Nantes
Yves LEMBEYE, Professeur des universités, Université Grenoble-Alpes
Christian MARTIN, Professeur des universités, Université Claude Bernard Lyon 1
Mohamed BENSETTI, Professeur des universités, Université Paris-Saclay – Centrale Supélec
Encadrement :
Arnaud BREARD, Professeur des universités, Ecole Centrale de Lyon, Directeur de thèse
Loris PACE, Maître de conférences, Ecole Centrale de Lyon, Co-encadrant de thèse
Abstract :
Power electronics plays a key role in the electrification of modern systems by enabling efficient energy transfer between various subsystems. Over the past decades, increasing the switching frequency has been a major approach to improving power density. To that extent, pushing the operating frequency into tens of megahertz enables the elimination of magnetic cores, and the related losses. Very high frequency power conversion is a promising field for increasing the power density of power converters and reducing their heterogeneity, as well as meeting specific application needs, such as wireless power transfer or plasma generation.
This research field has gained new momentum with the advent of wide-bandgap semiconductors, particularly GaN HEMTs, which are capable of switching in just a few nanoseconds. In order to overcome the switching losses, specific resonant topologies that allow for soft-switching operation are required. Among them, the single-switch Class E topology, well known in radio-frequency applications, achieves high efficiencies (>90%) at very high frequencies. Yet, it remains rarely used in power electronics applications. Indeed, current design methods are complex and do not easily generalize to designer actual needs. Moreover, the efficiency and reliability of such converters are still limited in practice.
In this context, this thesis proposes a generic and intuitive design method tailored to Class E converters operating at VHF. Based on an exhaustive analytical modeling of the circuit, this method enables the identification of an optimized design space. The exploration is driven by some performance criteria. It allows the designer to explore and compare multiple design scenarios at an early stage, well before any experimental implementation. The method is also extended to the design of isolated Class E based DC DC converters. These can be connected in series or parallel, making them suitable for a wide range of applications. To validate the proposed approach, three Class E inverter prototypes (40.68 MHz, 50 W) as well as an isolated Class E² DC-DC converter (40.68 MHz, 50 W), have been developed. The GaN transistor operates under soft-switching conditions, as assumed by the design method. A comprehensive simulation model is also introduced. It is based on high-frequency characterization of passive and active components, as well as electromagnetic modeling of the printed circuit board. The impedances of both resonant components and parasitic elements are accounted for and anticipated at the design stage. The non-linearity of parasitic capacitances of the semiconductors is also considered and fully integrated within the design method.
Keywords:
Power electronics, very high frequency, Class E, high frequency characterization, GaN HEMT, design method