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Die Steigerung der Energieeffizienz ist eine gesellschaftliche Notwendigkeit und bildet neben dem Umstieg auf erneuerbare Energien den entscheidenden Hebel zur Realisierung der Energiewende und Minderung der CO2-Emissionen in Deutschland. Kleine und mittlere Unternehmen (KMU) nehmen in diesem Zusammenhang eine besondere Stellung ein: Aktuelle Studien deuten auf geringere Steigerungsraten der Energieeffizienz gegenüber Großunternehmen hin, die zumeist mit unterschiedlichen materiellen und personalen Voraussetzungen erklärt werden.
Das Forschungsprojekt "Entscheidungen für Energieeffizienz" widmete sich vor diesem Hintergrund der Situation produzierender KMU in Baden-Württemberg. Mit dem Ziel, ein verbessertes Verständnis über die Energieeffizienz-Entscheidungen der KMU zu gewinnen, wurde der Frage nachgegangen, wie der Umgang mit Energie in der täglichen Praxis in KMU organisiert wird, wie über Energieeffizienz entschieden wird und welche Treiber und Hemmnisse sich dabei ergeben.
Zur Beantwortung der Fragen wurde ein Ansatz verfolgt, der kulturelle Einflüsse mitberücksichtigt. Forschungsstrategisch kam ein Mixed-Methods-Ansatz zur Anwendung, der durch die Kombination von qualitativen Daten (Einzelfallstudien) und quantitativen Daten (Fragebogenerhebung) methodisch umgesetzt wurde.
Der vorliegende Beitrag zeigte die Anwendung eines Extended Kalman Filters für die Beurteilung des Verschleißzustandes von Rollenketten. Anders als in den üblicherweise eingesetzten signalbasierten Verfahren wurde damit ein modellbasierter Ansatz gewählt. Der Einsatz des Extended Kalman Filters ermöglicht die Schätzung von Parametern eines reduzierten Kettenmodells, das die Dynamik der einzigen Messgröße, nämlich des Drehmoments des antreibenden Motors näherungsweise nachbildet. Im Beitrag wurde dieses Verfahren auf Messdaten aus vier Dauerversuchen an Rollenketten eingesetzt und gezeigt, dass mit steigendem Verschleiß eine Änderung ausgewählter Modellparameter erfolgt.
Diese Vorgehensweise ist ein erster Ansatz, der durch weitere Forschungsarbeiten noch verbessert werden muss. In zukünftigen Forschungsarbeiten wird zusätzlich zur Parameterschätzung eine Prädiktion durchgeführt, um einen Schätzwert für die Restlebensdauer zu erhalten. Hierzu gibt es Ansätze in der Literatur, die auf das konkrete Problem angepasst werden müssen. Zudem muss die Modellierungssystematik so erweitert werden, dass Wissen über das Prozessverhalten in die Modellierung mit eingebracht wird, um die Aussagekraft der Ergebnisse sowie die Robustheit des Verfahrens bezüglich Betriebsparametern, Umgebungsbedingungen und Exemplarstreuungen zu verbessern.
Drei Stufen geben Sicherheit
(2018)
GaN-Transistoren bieten ein enormes Potenzial für kompakte Leistungselektronik, indem sie die Größe von passiven Bauelementen verringern. Allerdings bringt das schnelle Schalten Herausforderungen für den Gate-Treiber mit sich. Ein vollständig integrierter Treiber mit drei Spannungsstufen hilft, diese zu lösen.
The level shifter and the floating gate supply for high-side transistors are a major challenge in high-voltage DCDC converters. This paper presents a high speed and power-efficient level shifter for voltages of up to 50V, suitable for both PMOS and NMOS power FETs. A switching node falling edge detection allows both, a sensitive and safe signal detection. This enables a robust operation during steep dv / dt transitions and a power consumption as low as 4.1 pJ per switching cycle, which is a reduction of more than 40% compared to prior art. An active clamping circuit prevents common mode displacement currents into the high-side supply. The level shifter is implemented in a 180nm BiCMOS technology. Measurements confirm a 50V 120MHz high-speed operation of the level shifter with a rising / falling propagation delay of 1.45 ns / 1.3 ns, respectively. The dv / dt robustness has been confirmed by measurements for transitions up to 6V/ ns.
A wide-bandwidth galvanically isolated current sensing circuit with an integrated Rogowski coil in 180nm CMOS is presented. Exploiting the high-frequency properties of an optimized on-chip Rogowski coil, currents can be measured up to a bandwidth of 75 MHz. The analog sensor front-end comprises a two-stage integrator, which allows a chopper frequency below signal bandwidth, resulting in 2.2 mVrms output noise. An additional integrated Hall sensor extends the measurement range towards DC.
Due to their superior fast-switching performance, GaN transistors show enormous potential to enable compact power electronics in applications like renewable energy, electrical cars and home appliances by shrinking down the size of passives. However, fast switching poses challenges for the gate driver. Since GaN transistors have a low threshold voltage Vt of ~1V, an unintended driver turn-on can occur in case of a unipolar gate control as shown for a typical half-bridge in Fig. 24.2.1 (top left). This is due to coupling via the gate-drain capacitance (Miller coupling), when the low-side driver turns on, causing a peak current into the gate. This is usually tackled by applying a negative gate voltage to enhance the safety margin towards Vt, resulting in a bipolar gate-driving scheme. In many power-electronics applications GaN transistors operate in reverse conduction, carrying the inductor current during the dead time t, when the high-side and low-side switch are off (as illustrated at a high-side switch in Fig. 24.2.1, bottom left). As there is no real body diode as in silicon devices, the GaN transistor turns on in reverse operation with a voltage drop VF across the drain-source terminals (quasi-body diode behavior). As a negative gate voltage adds to VF, 63% higher reverse-conduction losses were measured for a typical GaN switch in bipolar gate-drive operation. This drawback is addressed by a three-level gate voltage (positive, 0V, negative), which at the same time provides robustness against unintended turn-on similar to the bipolar gate driver, proven in [1] for a discrete driver.
This paper presents a fully integrated gate driver in a 180-nm bipolar CMOS DMOS (BCD) technology with 1.5-A max. gate current, suitable for normally OFF gallium nitride (GaN) power switches, including gate-injection transistors (GIT). Full-bridge driver architecture provides a bipolar and three-level gate drive voltage for a robust and efficient GaN switching. The concept of high voltage energy storing (HVES), which comprises an on-chip resonant LC tank, enables a very area-efficient buffer capacitor integration and superior gatedriving speed. It reduces the component count and the influence of parasitic gate-loop inductance. Theory and calculations confirm the benefits of HVES compared to other capacitor implementation methods. The proposed gate driver delivers a gate charge of up to 11.6 nC, sufficient to drive most types of currently available GaN power transistors. Consequently, HVES enables to utilize the fast switching capabilities of GaN for advanced and compact power electronics.
Based on a survey among customers of seven German municipal utilities, we estimate hierarchical multiple regression models to identify consumer motivations for participating in P2P electricity trading and develop implications for marketing strategies for this currently relatively unknown product. Our results show a low importance of socio-demographics in explaining differences between consumer groups, but high influence of attitudes, knowledge and likelihood to purchase related products. The most valuable target groups for P2P electricity trading marketing strategies of municipal utilities first and foremost should aim at are innovators, especially prosumers. They are well-informed about and open minded concerning electricity sharing and highly environmentally aware. They ask for transparency and are willing to purchase related products. They are attracted by the ability to share generation and consumption and to a lesser extent by economic reasons. Our results indicate that the marketing efforts should to a special degree take peer effects into account, as they are found to wield great influence on general openness towards and purchase intention for P2P electricity products. Finally, municipal utilities should build on the high level of satisfaction and trust of consumers and use P2P electricity trading as measure to keep and win customers willing to change their supplier.
A novel gate driving approach to balance the transient current of parallel-connected GaN-HEMTs
(2018)
To enable higher current handling capability of GaN-based DC/DC converters, devices have to be used in parallel. However, their switching times differ, especially if their threshold voltages are not identical, which causes unbalanced device current. This paper focuses on the homogeneous distribution of turn-on switching losses of GaN-HEMTs connected in parallel. By applying a new gate driver concept, the transient current is distributed evenly. The effectiveness of this concept is demonstrated by double pulse measurements, for switching currents up to 45A and a voltage of 400V. A uniform current distribution is achieved, including a reduction of the turn-on losses by 50% compared to a conventional setup.
The hotspot detection has received much attention in the recent years due to a substantial mismatch between lithography wavelength and semiconductor technology feature size. This mismatch causes diffraction when transferring the layout from design onto a silicon wafer. As a result, open or short circuits (i.e. lithography hotspots) are more likely to be produced. Additionally, increasing numbers of semiconductors devices on a wafer required more time for the lithography hotspot detection analysis. In this work, we propose a fast and accurate solution based on novel artificial neural network (ANN) architecture for precise lithography hotspot detection using a convolution neural network (CNN) adopting a state of-the-art technique. The experimental results showed that the proposed model gained accuracy improvement over current state-of-theart approaches. The final code has been made publicly available.
