621 Angewandte Physik
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IGBT modules with anti-parallel FWDs are widely used in inductive load switching power applications, such as motor drive applications. Nowadays there is a continuous effort to increase the efficiency of such systems by decreasing their switching losses. This paper addresses the problems arising in the turn-on process of an IGBT working in hard-switching conditions. A method is proposed which achieves – contrary to most other approaches – a high switching speed and, at the same time, a low peak reverse-recovery current. This is done by applying an improved gate current waveform that is briefly lowered during the turn-on process. The proposed method achieves low switching losses. Its effectiveness is demonstrated by experimental results with IGBT modules for 600V and 1200V.
Die vorliegende Erfindung betrifft ein Transmission Line Pulssystem zum Erzeugen eines elektrischen Pulses, sowie ein diesbezügliches Verfahren. Dabei umfasst das Transmission Line Pulssystem: eine Transmission Line, eine Energieversorgungsquelle zum Aufladen der Transmission Line und einen Entladungsschalter zum Auslösen einer Entladung der aufgeladenen Transmission Line, dadurch gekennzeichnet, dass die Transmission Line eine Vielzahl von Einzelsegmenten umfasst, wobei jedes Einzelsegment über ein zugehöriges Einstellglied mit einem gemeinsamen Massepotential elektrisch verbunden ist, und wobei zumindest eines der Einstellglieder einen Einstellkondensator und einen Einstellschalter aufweist.
This paper addresses the turn-on switching process of insulated-gate bipolar transistor (IGBT) modules with anti-parallel free-wheeling diodes (FWD) used in inductive load switching power applications. An increase in efficiency, i.e. decrease in switching losses, calls for a fast switching process of the IGBT, but this commonly implies high values of the reverse-recovery current overshoot. To overcome this undesired behaviour, a solution was proposed which achieves an independent control of the collector current slope and peak reverse recovery current by applying a gate current that is briefly turned negative during the turn-on process. The feasibility of this approach has already been shown, however, a sophisticated control method is required for applying it in applications with varying currents, temperature and device parameters. In this paper a solution based on an adaptive, iterative closed-loop ontrol is proposed. Its effectiveness is demonstrated by experimental results from a 1200 V/200A IGBT power module for different load currents and reverse-recovery current overshoots.
Die vorliegende Erfindung betrifft eine Schaltungsanordnung mit einer Bootstrap-Schaltung, die zumindest eine Hauptkapazität aufweist, von der die erste Seite mit einem ersten Zweig der Schaltungsanordnung und die zweite Seite mit einem auf veränderlichem Potential liegenden zweiten Zweig der Schaltungsanordnung verbunden ist. Die vorgeschlagene Schaltungsanordnung zeichnet sich dadurch aus, dass die Bootstrap-Schaltung parallel zur Hauptkapazität wenigstens eine weitere Kapazität aufweist, die über eine zweite Versorgungsspannung auf eine höhere Spannung aufladbar ist als die Hauptkapazität und über wenigstens ein Schaltelement zur Unterstützung der Hauptkapazität zuschaltbar ist. Bei der vorgeschlagenen Schaltungsanordnung kann in Abhängigkeit von der Dimensionierung der Bootstrap-Kapazitäten eine sehr viel kleinere Fläche mit höherem oder gleich bleibenden Spannungseinbruch oder eine nicht so starke Flächenreduzierung mit kleinerem Spannungseinbruch verglichen mit einer herkömmlichen Bootstrap-Schaltung erzielt werden.
Stress is becoming an important topic in modern life. The influence of stress results in a higher rate of health disorders such as burnout, heart problems, obesity, asthma, diabetes, depressions and many others. Furthermore individual’s behavior and capabilities could be directly affected leading to altered cognition, inappropriate decision making and problem solving skills. In a dynamic and unpredictable environment, such as automotive, this can result in a higher risk for accidents. Different papers faced the estimation as well as prediction of drivers’ stress level during driving. Another important question is not only the stress level of the driver himself, but also the influence on and of a group of other drivers in the near area. This paper proposes a system, which determines a group of drivers in a near area as clusters and it derives the individual stress level. This information will be analyzed to generate a stress map, which represents a graphical view about road section with a higher stress influence. Aggregated data can be used to generate navigation routes with a lower stress influence to decrease stress influenced driving as well as improve road safety.
The current paper discusses the optimal choice of a filter time constant for filtering the steady state flux reference in an energy efficient control strategy for changing load torques. It is shown that by appropriately choosing the filter time constant as a fraction of the rotor time constant the instantaneous power losses after a load torque step can be significantly reduced compared to the standard case. The analysis for the appropriate choice of the filter time constant is based on a numerical study for three different induction motors with different rated powers.
This paper describes the design and outcomes of an experimental study that addresses stock-and-flow-failure from a cognitive perspective. It is based on the assumption that holistic (global) and analytic (local) processing are important cognitive mechanisms underlying the ability to infer the behavior of dynamic systems. In a stock-and-flow task that is structurally equivalent to the department store task, we varied the format in which participants are primed to think about an environmental system, in particular whether they are primed to concentrate on lower-level (local) or higher-level (global) system elements. 148 psychology, geography and business students participated in our study. Students’ answers support our hypothesis that global processing increases participants’ ability to infer the overall system behavior. The beneficial influence of global presentation is even stronger when data are presented numerically rather than in the form of a graph. Our results suggest presenting complex dynamic systems in a way that facilitates global processing. This is particularly important as policy-designers and decision makers deal with complex issues in their everyday and professional life.
A 20 V, 8 MHz resonant DCDC converter with predictive control for 1 ns resolution soft-switching
(2015)
Fast switching power supplies allow to reduce the size and cost of external passive components. However, the capacitive switching losses of the power stage will increase and become the dominant part of the total losses. Therefore, resonant topologies are the known key to reduce the losses of the power stage. A power switch with an additional resonant circuit can be turned on under soft-switching conditions, ideally with zero-voltage-switching (ZVS). As conventional resonant converts are only efficient for a constant load, this paper presents a predictive regulation loop to approach soft-switching conditions under varying load and component tolerances. A sample and hold based detection circuit is utilized to control the turn-on of the power switch by a digital regulation. The proposed design was fabricated in a 180 nm high-voltage BiCMOS technology. The efficiency of the converter was measured to be increased by up to 16 % vs. worst case timing and by 13 % compared to a conventional hard-switching buck converter at 20 V input voltage and at approximately 8 MHz switching frequency.
A generic, knowledge-based method for automatic topology selection of analog circuits in a predefined analog reuse library is presented in this paper on the OTA (Operational Transconductance Amplifier) example. Analog circuits of a given circuit class are classified in a topology tree, where each node represents a specific topology. Child nodes evolve from their parent nodes by an enhancement of the parent node’s topological structure. Topology selection is performed by a depth first-search in the topology tree starting at the root node, thus checking topologies of increasing complexity. The decisions at each node are based on solving equations or – if this is not possible – on simulations. The search ends at the first (and thus the simplest) topology which can meet the specification after an adequate circuit sizing. The advantages of the generic, tree based topology selection method presented in this paper are shown in comparison to a pool selection method and to heuristic approaches. The selection is based on an accomplished chip investigation.