This paper addresses the critical issues in parallelising GaN FETs for high-current switches in low-voltage power converter applications, such as light e-mobility, humanoid robotics and battery chargers. While parallel connection enhances power handling and efficiency, it introduces significant challenges like unequal current sharing due to device parameter variations and asymmetrical layouts in static and dynamic conditions. The paper investigates these constraints using a dual approach of LTSpice simulations and experimental validation. An experimental board composed of four switching legs with independently controlled gate voltage and time delay for each parallel device is developed, allowing accurate emulation of various parameter spread conditions. These combined simulations and experimental analyses comprehensively investigate the behaviour of GaN transistors in parallel configurations under real-world operating conditions. It aims to demonstrate the feasibility of high-current GaN FET power boards and increase the knowledge of designing GaN FET modules by considering both transistor parametric spread and layout optimisation.

The paper deals with the reverse conduction during the dead time of low-voltage GaN FETs in inverters for motor control applications. The current variation caused by the sinusoidal modulation in an AC motor drive leads to a different dead time losses mechanism when compared to the DC-DC converter application, which is worth investigating. The reverse conduction is correlated with both current variation and GaN technology in inverter legs applications. Furthermore, the GaN FET device’s reverse conduction is compared to equivalent low-voltage MOSFET devices, considering the different static and dynamic characteristics. This work aims to provide inverter designers with an investigation and a guideline on the dead time selection and its limits in an inverter leg for motor control with the last generation of GaN FET devices.

In this paper, an LCC-S compensated wireless power transfer system regulated by a variable inductor is presented. The inductance variation is performed by exploiting the magnetic material saturation of the inductor core, regulating the DC bias. The magnetic design of the controlled variable inductor is proposed. A low-cost auxiliary circuit for the regulation of the bias current is proposed, and the performance is evaluated. The effect of the inductance variation on the output power regulation and conversion efficiency are evaluated through an experimental setup.

This paper deals with an isolated full-bridge circuit designed to distribute the auxiliary power supplies needed in power converters. The proposed circuit features soft-switching operation. The provided galvanic isolation limits the disturbances propagation in the critical circuits of power converters, such as gate drivers and control circuits. Soft switching allows the reduction of EMI and increases the converter efficiency. Compared to a classic flyback converter solution, the circuit is based on a high frequency AC power distribution. In every point to be supplied, an additional transformer followed by a rectifier with an output filter and a regulator circuit satisfy the requests of the load. The circuit has been widely applied in various power converters such as inverters, PFCs and DC-DC full bridge converters for battery chargers, showing insulation benefits, noise rejection characteristics, improved reliability with adequate efficiency.

Nowadays, the light-emitting diode (LED) bulb is one of the preferred choice in lighting system design. Electrical models of the LED lamps have to consider their nonlinear behavior involving current distortion on the mains. With this purpose, an equivalent electrical circuit emulating the current drawn by a LED Bulbs is carried out. In this work, different lamps have been tested under variable supply voltage. The comparison between the simulations performed by means of PSpice and the experimental measurements has highlighted that linear interpolation for the amplitude of each harmonic current, as function of the voltage on the main, provides a good estimation of the total current waveform.

Super junction (SJ) MOSFET is a well-established device in high-density and high frequency power conversion. Soft-switching techniques are usually adopted at high frequency to reduce the power losses into the power devices. However, new challenging issues appear always when the paradigm changes. In fact, unexpected heating and efficiency reduction due to Coss related phenomena are key issues to be faced when SJ MOSFETs are adopted in high-frequency soft-switching applications. The phenomenon appears when large voltage transients are applied to the drain-source terminals as in the case of soft-switching applications. This paper provides analysis of the electrical hysteresis, and proposes an equivalent circuit that may model such a behavior in case of SJ MOSFETs. The loss model of Coss has been validated by comparing the measurements with the simulation runs performed by means of the Simulink package.

This paper presents an analytical model of the impedance between two coils supported by ferrite shield. The new model is not restricted to round coils and applies to more complex winding geometries, as specified by the Wireless Power Consortium. The mutual inductance is derived by solving Maxwell's equations and using Bessel function of the first kind. The model results are compared with experimental data as a function of the vertical displacement between the coils. In addition, a wireless power transfer system is modeled to calculate system efficiency by adopting the above coils impedance model. Experimental results run on 5W wireless power transfer system at several displacement steps are compared against simulation data.

The aim of this work is the development of an improved model for the analysis of the transient thermal behavior of MOSFET power devices in UIS conditions. The proposed modeling technique allows to achieve a higher accuracy for the estimation of the temperature of the power semiconductor if compared with classical models. The epitaxial thickness of the device is taken now into account in a bi-dimensional domain, thus accounting both for the heat flux generation and propagation on the plane (valid assumption, but only for low voltage devices) but also along the other dimensions. The new developed model presents more accurate results than the ones previously presented and doesn't make use of empirical correction factors. The mathematical process to build up the model is developed, and a comparison is carried out between the measured temperatures on the device and the estimation by the model. The results are shown and the good fitting of the simulation runs with the experimental measurements demonstrates the correctness of the proposed approach.

MOTIVATION: Atherosclerosis is a disease that is present in almost all humans, typically beginning in early adolescence. It is a human disease broadly investigated, that is amenable to quantitative analysis. Oxidized low-density lipoproteins (LDLs) and their autoantibodies are involved in the development of atherosclerosis in animal models, but their role in humans is still not clear. Computer models may represent a virtual environment to perform experiments not possible in human volunteers that can provide a useful instrument for monitoring both the evolution of atherosclerotic lesions and to quantify the efficacy of treatments, including vaccines, oriented to reduce the LDLs and their oxidized fraction. RESULTS: We report the application of an agent-based model to model both the immune response to atherogenesis and the atheromatous plaque progression in a generic artery wall. The level of oxidized LDLs, the immune humoral response with production of autoantibodies, the macrophages activity and the formation of foam cells are in good agreement with available clinical data, including the formation of atheromatous plaques in patients affected by hypercholesterolemia. AVAILABILITY: The model is available at http://www.immunogrid.eu/atherogenesis/