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Despite the high prevalence of central nervous system (CNS) involvement in relapsing pediatric acute lymphoblastic leukemia (ALL), our understanding of CNS invasion is still vague. As lymphoblasts have to overcome the physiological blood-CNS barriers to enter the CNS, we investigated the cellular interactions of lymphoblasts with the choroid plexus (CP) epithelium of the blood-cerebrospinal fluid...
A dc-based low-voltage power supply offers many advantages over the historically grown ac voltage infrastructure. The paper shows the potentials for cost reduction, efficiency enhancement and equipment miniaturization through new cognitive power electronics, but also discusses the obstacles to a faster market penetration of dc microgrids. These include aspects of grid control, grid stability, security...
This paper presents a procedure to acquire precise measurement data of the output characteristics with a custom-made setup. In comparison to datasheets and common curve tracer measurements, the measurement range is extended and the accuracy improved. After deriving the theoretical minimal switching energy for semiconductor switches in a half-bridge configuration, possible operating points of the latest...
DC microgrids can offer many advantages for an installation in commercial applications like data centers or in private homes. In this paper, future expansion of such grids towards a bipolar architecture (e.g. ±380 VDC) is evaluated. The focus lies on various fault situations, their effects on the grid and possible solutions to maintain grid safety. For this purpose, a laboratory scale bipolar test...
This paper presents a novel procedure to determine the internal gate-source voltage inside a multi-chip power module using the example of a SiC half bridge module. Based on the lumped elements of the gate circuit calculated by a quasi-static electromagnetic simulation, each field-effect transistor is represented by a single, voltage dependent capacitor. The procedure is validated by clamped inductive...
The extension of a segregated DC microgrid with different voltage levels to a fully bidirectional grid is surveyed in this paper. The approach offers efficient implementation of small sources of regenerative energies and distributed energy storage systems as well as the possibility to even include electric vehicles as sources with high capacity. Furthermore, energy stored in any part of the grid,...
DC microgrids have become widely adapted in recent years, with 380 V being the most common voltage choice in applications like data centers and central offices around the world. For future developments with an increasing power demand, adding a second line conductor to a DC microgrid can provide means to increase overall energy efficiency. This paper evaluates fault situations in such a bipolar ±380...
This paper presents a 600 V, 55 mS GaN cascode with slew rate control. The time constants of cascodes which determine the switching speed are analyzed, discussed and verified by time domain simulations. Clamped inductive switching measurements of commercial and a custom-built GaN cascodes prove the applicability of the switching speed control mechanisms with additional passive components. The gathered...
380 VDC distribution grids have reached maturity for the power supply of data centers and central offices over recent years. New developments in this field are tending towards integrating more distributed energy resources like photovoltaics and wind turbines. Also, high-capacity battery storage systems based on lithium-ion cells are on the rise to increase self-reliance and reduce operating cost....
Die Produktlebenszyklen werden durch den steigenden Wettbewerbsdruck stetig kürzer. Dies veranlasst Unternehmen, Produktinnovationen in immer geringeren Zeitabständen auf den Markt zu bringen und Produktentwicklungszeiten zu verkürzen. Zusätzlich wirken sich erhöhte Anforderungen bezüglich Produktzuverlässigkeit und -lebensdauer erschwerend aus. Um dieser Herausforderung zu begegnen ist eine enge...
Zur Realisierung einer wettbewerbsfähigen Montage müssen Lösungen gefunden und verglichen werden, mit denen die Herstellung von leistungselektronischen Baugruppen möglich ist. Das Spektrum der Möglichkeiten erstreckt sich hierbei von der reinen manuellen Montage bis hin zur Vollautomatisierung. Durch gezielte Einflussnahme auf das Produkt oder die verwendeten Bauelemente können jedoch auch Resultate...
Multi-resonant converters like the CLLLC topology are known for their outstanding efficiency and high power density. Little information has however been published about the influences of secondary side diode junction capacitances on the output characteristics of the resonant converter. This paper presents a detailed analysis of these influences in the inductive working range and reviews practical...
This paper focuses on the magnetic design of a multi-coil system for an inductive power transfer (IPT) system for charging electric vehicles with a small air gap between transmitter and receiver coils. Thus, external stray fields can be reduced and the expense of material decreases compared to systems using a large air gap. The magnetic design of the multi-coil system is optimized for the given package...
In this paper a 3.7 kW On-board charger (OBC) for electric or plug-in hybrid vehicles is proposed. With regard to standardization, cost reduction and to increase the volume of produced devices, the OBC is derived from a fully modular circuit and control structure. The two-stage circuit arrangement consists of an isolated full bridge ZVS resonant converter and an interleaved boost converter for power...
In this paper, the efficiency limits of power electronic converters are investigated from a semiconductor point of view. The approach is presented on the example of a hard switching half bridge while taking Si, SiC and GaN devices into account. Beside parasitic effects of the semiconductors itself, further converter non-idealities and limits from a thermal point of view are discussed. All in all,...
Droop Control has been a well-established control technique both in AC and DC power distribution grids for many years, because it provides a simple way to equally distribute the load current between remote power sources. With the increasing demand for low voltage DC microgrids supplying high-reliability equipment, like servers in data centers, to work both grid-tied and autonomously without a connection...
This paper describes the application of a distributed DC microgrid in a commercial environment as well as the current state of the art and standardization efforts. The introduced grid features various sources and loads being interconnected with a 380 VDC bus. Here, focus lies on the implementation of a DC fast charge station for electro mobility into a DC grid as well as to elaborate the advantages...
One of the most important physical parameters for state estimation in battery based Energy Storage Systems (ESS) is the temperature. This physical quantity does not only strongly influence state estimation for battery management systems, but also significantly affects lifetime and return on investment finally. Thus, monitoring the cell temperature is essential when high performance and efficiency...
This paper describes a DC-link discharge device that is smaller and cheaper than conventional resistor or PTC-based solutions. The basic idea is to use the switching element (IGBT, Mosfet), that is usually controlling the PTC or resistor, in a linear mode and decrease the maximum power by shifting the discharge curve from an uncontrolled square voltage dependent curve to a roughly constant power characteristic...
Overview, comparison and evaluation of common DC micro grid design considerations. The focus of this paper is to explore the main differences and advantages/disadvantages of various topologies and control strategies for DC micro grids. The requirements of various application areas can strongly influence the individual system design. Control strategies, single- or two-phase designs, earthing concepts,...
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