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In this paper, a methodology is proposed for studying the current collapse effects of Gallium Nitride (GaN) power diodes and the consequences on the dynamic on-resistance (RON). Indeed, the growing interest of GaN based, high frequency power conversion requires an accurate characterization and a deep understanding of the device’s behaviour before any development of power converters. This study can ultimately be used to model observed trap effects and, thus, improve the equivalent electrical model. Using an in-house circuit and a specific experimental setup, a current-collapse phenomenon inherent to gallium nitride semiconductor is studied on planar 650 V—6 A GaN diodes by applying high voltage stresses over a wide range of temperatures. With this method, useful data on activation energy and capture cross section of electrical defects linked to dynamic RON are extracted. Finally, the origins of such defects are discussed and attributed to carbon-related defects.

Due to the advancement in the development of semiconductors used in the power converters, the printed circuit boards (PCBs) require an in-depth study of their electromagnetic behavior. To characterize the behavior of the PCBs, the Darwin model is employed, which can take into account all the coupled effects, namely resistive, inductive, and capacitive effects, at the intermediate frequencies. Nevertheless, the study of particular structures having a geometric dimension smaller than the others can create meshing difficulties. The modeling of thin structures by the finite element method requires the optimization of the mesh. To circumvent this issue, the shell elements for both node and edge elements are applied in this work. Finally, to validate the proposed approaches, two PCBs with different geometries are studied in both time and frequency domains, where the measurements for a single PCB are provided to compare with the numerical results.

Due to the high switching speed of Gallium Nitride (GaN) transistors, parasitic inductances have significant impacts on power losses and electromagnetic interferences (EMI) in GaN-based power converters. Thus, the proper design of high-frequency converters in a simulation tool requires accurate electromagnetic (EM) modeling of the commutation loops. This work proposes an EM modeling of the parasitic inductance of a GaN-based commutation cell on a printed circuit board (PCB) using Advanced Design System (ADS®) software. Two different PCB designs of the commutation loop, lateral (single-sided) and vertical (double-sided) are characterized in terms of parasitic inductance contribution. An experimental approach based on S-parameters, the Cold FET technique and a specific calibration procedure is developed to obtain reference values for comparison with the proposed models. First, lateral and vertical PCB loop inductances are extracted. Then, the whole commutation loop inductances including the packaging of the GaN transistors are determined by developing an EM model of the device’s internal parasitic. The switching waveforms of the GaN transistors in a 1 MHz DC/DC converter are given for the different commutation loop designs. Finally, a discussion is proposed on the presented results and the development of advanced tools for high-frequency GaN-based power electronics design.

In order to better predict the high frequency switching operation of transistors in power converters, parasitic elements of these devices such as resistances, inductances and capacitances must be accurately evaluated. This paper reports on the characterization of a gallium nitride (GaN) packaged power transistor using S-parameters in order to extract the device parasitics. Because the transistor is packaged, a calibration technique is carried out using specific test fixtures designed on FR4 printed circuit board (PCB) in order to get the S-parameters in the transistor plane from the measurement. The proposed method is suitable for a wide range of power devices. In this work it is applied to an enhancement mode GaN High Electron Mobility Transistor (HEMT).The impact of junction temperature on drain and source resistances is also evaluated. According to characterization results, equation-based modeling is proposed for the non-linear parameters. The extracted parasitic elements are compared with reference values given by the device manufacturer.

The constant growth of electric consumption leads to considerable progress in power conversion. Recent studies have shown that using Gallium Nitride (GaN) as a technological building bloc permits to develop converter operating at high frequency with reduced volume and weight. Furthermore, it is conceivable the monolithic co-integration of devices towards full-GaN switching cells. Therefore, characterization of GaN power devices is needed to provide accurate models in a wide frequency band in order to design new generations of converters. An innovative modeling method for GaN High Electron Mobility Transistor (HEMT) power transistors based on the use of Scattering parameters (S-parameters) and small-signal equivalent circuit was recently developed and validated in previous studies. Meanwhile, the demand concerning GaN diodes increases, pushing forward the need for dedicated electric model. Through S-parameters, current-voltage and current-collapse measurements, this paper presents the characterization of packaged GaN diodes with the aim to establish an accurate nonlinear model. The analyzed devices are still in the development phase, but initial results are very promising and get close to commercial SiC diodes available on the market.

This work proposes the electrothermal modeling of a packaged GaN power transistor in order to evaluate by simulation its performances in a 200 W – 1 MHz DC/DC converter. The complete electrical modeling of the high frequency converter using EM-circuit co-simulations is presented. After validation of the GaN transistor switchings waveforms and estimation of power losses, the operating temperature of the device is simulated and experimentally validated.

Wide Bandgap (WBG) power devices show very good characteristics for high frequency operation in power converters, leading to a better power integration by reducing size and weight of passive components. Access parasitics such as resistances and inductances related to packaging and interconnections are important parameters to determine in order to better predict high frequency switching of WBG power devices. In order to design a 1 MHz hybrid GaN/SiC power converter, this paper reports on the characterization of packaged power devices such as Gallium Nitride (GaN) transistors and Silicon Carbide (SiC) Schottky diodes using S-parameters in order to extract the device parasitics. The method lays on a calibration procedure carried out using specific test fixtures designed on FR4 Printed Circuit Board (PCB). The proposed method has the objective to be suitable for a wide range of power devices.

Gallium Nitride (GaN) power devices developed these recent years are ideal candidates for high frequency power conversion, leading to a reduction of size, cost and weight of power converters. The design of these converters is based on simulations which require developing accurate models over a wide frequency range. This paper presents a new characterization method of GaN power transistors based on the extraction of devices small-signal parameters up to the gigahertz range using 2-port S-parameters measurements and dedicated characterization fixtures on printed circuit boards (PCB).

The influence of the electromagnetic environment of the indoor power line grid (Houses’ Power Grid) is increasingly important on the Power Line Communication transmission. The household equipment operating changes considerably the network impedance. Several procedures exist to evaluate the network impedance. Two impedance measurement techniques seem to be the most adequate and allow to characterize loads under their operating conditions. The first one uses current injection and reception probes and the second one uses capacitive coupling. With a proper pre-measurement calibration process, the proposed methods allow to measure the evolution of the impedance versus frequency of the active loads (TV screen, Fluorescent lamp…). This study deals with the analyses of these two methods in order to evaluate their advantages and disadvantages. The measurements are carried in narrowband and broadband in the frequency range of 10 kHz to 100 MHz.

Les composants de puissance à base de GaN présentent un fort potentiel pour le développement de convertisseurs statiques fonctionnant à hautes fréquences. Les principales propriétés de cette filière technologique conduisent à une réduction de la taille, du poids et du volume des convertisseurs d’énergie. La conception de ces convertisseurs hautes fréquences (HF) repose sur des simulations nécessitant des modèles de composants actifs très précis. Afin d’obtenir ces modèles, une phase de caractérisation permettant d’obtenir les différents paramètres du modèle est nécessaire. Ce travail présente une méthode de caractérisation des transistors de puissance GaN basée sur la mesure de paramètres S à l’aide de dispositifs d’adaptation sur circuit imprimé ainsi que des mesures en régime pulsé.

Ce travail de thèse s’inscrit dans le cadre de la collaboration entre l’IEMN et le L2EP sur la thématique de la montée en fréquence des convertisseurs statiques pour l’intégration de puissance. Les transistors de puissance à base de Nitrure de Gallium (GaN) offrent la possibilité de commuter de fortes puissances (au- delà d’1 kW) à hautes fréquences (au-delà d’1 MHz), permettant ainsi de réduire le volume des composants passifs des convertisseurs d’énergie. La conception des convertisseurs hautes fréquences par simulation nécessite de disposer de modèles de composants de puissance précis et valides sur une large plage de fréquence. Les techniques classiques de caractérisation et modélisation utilisées en électronique de puissance sont limitées en bande de fréquence et ne permettent pas de modéliser de façon précise tous les effets intrinsèques aux composants en hautes fréquences. L’objectif de ce travail est d’adapter les techniques utilisées dans le domaine de la caractérisation hyperfréquences pour la modélisation d’un transistor de puissance GaN. Dans le cadre de cette étude, le transistor GS66502B 650V/7.5A de type GaN HEMT sera utilisé pour la mise en place de notre méthode. La plage de fréquence visée pour la modélisation est 1 MHz – 1 GHz.

GaN transistors have been attracting much attention in recent years due to their significant benefits on the reduction of conduction and switching losses in power converters. However they suffer from current collapse effect due to trapped charges that notably impairs on-state resistance, as largely discussed in literature. This work focuses on commutation and shows that current collapse also impacts the switching waveforms of GaN transitors, notably increasing switching losses at turn-on. The influence on gate instability at turn-off is also discussed, showing that conventional double-pulse test may be misleading when measuring switching transitions. Theoretical analysis is validated by experimental measurements using a modified double-pulse test to evaluate the influence of current collapse on switching waveforms.

It is proposed a novel GaN-HEMT modelling method by using S-parameters to characterise device inter-electrode capacitances and terminal contact resistances.Afterwards, the model is implemented into virtual prototyping software. By co-simulation with electromagnetic models generated of the VP software, device switching waveforms are then obtained and they are compared with commercial ADS software and experimental measurement.

La montée en fréquence de commutation des transistors de puissance à base de Nitrure de Gallium (GaN) présente une avancée technologique conduisant à la réduction de la taille, du poids et du volume des systèmes de conversion de l’énergie. En effet, les propriétés physiques des transistors de type HEMT basés sur l’hétérostructure AlGaN/GaN présentent un fort potentiel pour le développement de convertisseurs statiques haute fréquence. Avec l’augmentation toujours croissante de la part de l’électronique de puissance dans les systèmes électriques actuels, cette filière technologique, associée à la filière du Carbure de Silicium (SiC), vise aujourd’hui à remplacer progressivement les composants de puissance à base de Silicium (Si) notamment pour des raisons de tension de claquage élevée, de robustesse vis-à-vis des conditions sévères de fonctionnement et d’intégration de puissance. La conception optimale des convertisseurs haute fréquence implique une connaissance précise du fonctionnement des composants de puissance au sein de ces systèmes. Ainsi, la conception de ces dispositifs repose sur des étapes d’analyse et de simulations menées à partir des modèles des semi-conducteurs de puissance et des éléments environnants. L’objectif de ce travail de thèse est de proposer une méthodologie de modélisation comportementale de transistors de puissance GaN en boitier basée exclusivement sur des méthodes de caractérisation non-intrusives. Les techniques de caractérisation électriques utilisées pour la modélisation de transistors fonctionnant en gammes radiofréquences, telles que la mesure des paramètres S ou les mesures courant/tension en régime pulsé, sont ici adaptées à la caractérisation du transistor de puissance GaN encapsulé. A partir des résultats de caractérisation, les différents éléments linéaires et non linéaires du modèle électrique du transistor sont obtenus et un modèle électrique complet rassemblant ces éléments est implémenté dans le logiciel de simulation ADS. Un banc de test Double Pulse est alors conçu afin de mettre en application le modèle électrique développé. Après modélisation de l’environnement du transistor, y compris du circuit imprimé, les résultats de simulation des formes d’onde de commutation sont confrontés aux résultats expérimentaux. Afin de tenir compte des effets de la température sur le fonctionnement du transistor, une méthodologie est proposée permettant d’obtenir le modèle thermique du composant à partir de mesures de puissance dissipée et d’une procédure d’optimisation. À partir du modèle obtenu, un convertisseur DC/DC utilisant le transistor GaN modélisé a été conçu et réalisé. Les résultats de simulation des formes d’onde de commutation sont confrontés aux résultats expérimentaux pour différentes températures de fonctionnement du transistor et une prédiction du fonctionnement en continu du convertisseur est réalisée.