Nicola Delmonte

Three-dimensional finite-element thermal simulation of GaN-based HEMTs.

The aim of this paper is to show and discuss results of three-dimensional finite-element thermal simulation of GaN HEMT structures. HEMTs differing by geometry, substrate material, passivation, and cooling strategy are simulated and compared in order to give a picture of the complex interplay of factors that must be reckoned with for proper thermal modeling and management.

Thermal characterization and modeling of power hybrid converters for distributed power systems

We have developed and experimentally validated a 3D model for thermal analysis and reliability-conscious design of hybrid power converters, using the commercial finite-element solver COMSOL™. The model was tuned using an accurate packaged MOSFET model and a specially-designed test board for multi-point temperature measurements. Measured and modeled temperatures showed good agreement for various dissipated power levels. A simplified version of the packaged MOSFET was then used in a bridge configuration to build a thermal model of the converter. After thermal studies, we performed preliminary finite-element analysis of the thermally-induced stress distributions.

Thermal modeling of planar transformer for switching power converters

Abstract This paper presents thermal simulations for reliability-oriented design of planar transformers for medium-power, high-frequency DC–DC converters. The modeling approach is based on accurate 3D finite-element thermal simulation of the transformer structure; inputs to the finite-element thermal model are the magnetic and electrical power losses extracted by experimental characterization of a planar transformer test-bench we designed and assembled. The simulation results are compared with those of infra-red thermal measurements. The simulations allowed to evaluate the effect of frequency and output current on the temperature distribution inside the transformer, thus setting limits for reliable operation, and to analyze alternative designs aimed at improving thermal management and, consequently the transformer reliability.

Power converters for future LHC experiments

The paper describes power switching converters suitable for possible power supply distribution networks for the upgraded detectors at the High Luminosity LHC collider. The proposed topologies have been selected by considering their tolerance to the highly hostile environment where the converters will operate as well as their limited electromagnetic noise emission. The analysis focuses on the description of the power supplies for noble liquid calorimeters, such as the Atlas LAr calorimeters, though several outcomes of this research can be applied to other detectors of the future LHC experiments. Experimental results carried on demonstrators are provided.

Developments on DC/DC converters for the LHC experiment upgrades

Prototypes of DC/DC power and Point of Load (PoL) converters were designed and built with the aim of satisfying the foreseen working parameters of the High Luminosity (HL) LHC experiments, using both Silicon (Si) MOSFETs and/or more recent devices substantiated of better power performance, like Silicon Carbide (SiC) and Gallium Nitride (GaN) transistors. Optimization of their design, based on the comparison between the simulated and measured thermal, electrical and mechanical performance, is in progress, and many improvements with respect to the previous versions are under implementation. We discuss in this paper the results of the last modifications. In addition, many tens of discrete component samples, chosen among the devices commercially available in the three different technologies (Si, SiC and GaN), were electrically characterized and tested under γ-rays, neutron, proton and heavy ion radiation, also using a combined run method. We have also planned to test some commercial DC/DCs under the extreme conditions of radiation and magnetic field expected in the upgrades of the LHC experiments. Here we show the first results on few samples.

Reliability oriented design of power supplies for high energy physics applications

Abstract The paper describes the design of switching converters suitable for power supply application in the LHC proton accelerator, in operation since 2010 at the European Organization for Nuclear Research (CERN) in Geneva (Switzerland). Experiments running at LHC must reliably operate in a harsh environment, due to radiation, high magnetic fields, and stringent thermal constraints. The followed approach takes into account the very tight reliability requirements during all the design stages, from the choice of circuit topologies and radiation hard power components, to the thermal layout and material optimization. Results carried out on prototypes are reported.

Power supply distribution system for calorimeters at the LHC beyond the nominal luminosity

This paper investigates the use of switching converters for the power supply distribution to calorimeters in the ATLAS experiment when the Large Hadron Collider (LHC) will be upgraded beyond the nominal luminosity. Due to the highly hostile environment the converters must operate in, all the main aspects are considered in the investigation, from the selection of the switching converter topologies to the thermal analysis of components and PCBs, with attention to reliability issues of power devices subject to ionizing radiations. The analysis focuses on the particular, but crucial, case of the power supplies for calorimeters, though several outcomes of the research can profitably be applied to other detectors like muon chambers.

Thermal modeling and design of power converters with tight thermal constraints

Abstract The aim of this paper is to show and discuss results of 3D finite-element simulations for thermal management design with tight constraints taking care of reliability aspects of hybrid power converters. A procedure to obtain simplified but accurate device models has been shown together with experimental validation. The simplified models have been used for converter module modeling. The same procedure has been applied to analyze the thermo-fluid dynamic problem of a whole converter comprising of three modules, inner air and enclosure.

Review of Oscillating Water Column Converters

Ocean waves are a huge largely unexploited energy resource, and the potential for extracting energy from waves is great. Research in this area is driven by the need to meet renewable-energy targets, but it is relatively immature compared to other renewable-energy technologies. This review introduces some device types that represent the state of the art of oscillating water column technology, a kind of wave energy converter (WEC). Unlike other works in literature, typically limited to specific aspects of WECs, in this paper, a system-wide perspective will be pursued, from the sea waves to the grid connection.

Heat management for power converters in sealed enclosures: A numerical study

This paper compares four assembly solutions for power converters operating in sealed enclosures with tight temperature specifications. The specific application of interest is one of the DC/DC converters of a power supply system to be used in high-energy-physics experiments: the sealed case must not significantly alter the temperature of the surrounding components (detectors and their electronics). The comparison is made using 3D Finite Element thermal modeling. The standard FR4 board solution is shown not to be viable under these tight temperature specs; we therefore explore alternative assemblies for the stack connecting the active devices to the heat-sink.