Jörg Krupar

Adaptive dv/dt and di/dt control for isolated gate power devices

This paper describes an adaptive gate control technique and a driver concept for isolated gate power devices. The proposed technique modulates the gate current of the power devices to control dv/dt and di/dt during a switching transition. It uses different time intervals, which are adjusted successively. Delays of the driver and the control section are compensated and therefore the proposed technique is applicable to control fast switching transients. To detect the di/dt during switching, a feedback path is implemented using parasitic inductances in the power section of the converter. By application of this method, we achieved the following properties: low propagation delays, reduced voltage overshoots, improved EMI and reduced switching power losses. The proposed method is applicable to converters with half-bridge, full-bridge and three-phase bridge configuration.

Design of Generalized Hysteresis Controllers for DC–DC Switching Power Converters

This paper proposes a novel uniform controller design approach for switching power converters. The procedure allows the deriving of both clock-driven and event-driven switching laws for controlling the stationary converter operation. A generic control scheme is introduced, which generalizes the concept of hysteresis control and executes a mode change, whenever the augmented state trajectory intersects with a switching plane in the state-time space. In contrast to previous approaches, the switching planes are systematically computed by means of results on periodic control systems. Consequently, desired loop properties such as orbital stability of a limit cycle and a fast transient response are guaranteed at least in a local neighborhood around a nominal set point. All results apply to a large class of switching converters and impose no restrictions on the number of energy storage devices or switches.

A performance estimation method for chaotic spread spectrum clock processes

The design of spread spectrum clock generators usually is an iterative procedure. In the design loop efficient performance criteria are required to select an optimal generator. Usually the PDS is used to rate the EMI performance. However the use of PDS results in a very high calculation effort and speeds down the design loop. In contrast to classical EMI rating by use of the PDS we propose the use of simple statistical characteristics. We investigate the dependence between the EMI performance of the clock process, the statistical characteristics and different maps used for chaotic clock generation.

EMI performance of spread spectrum clock signals with respect to the IF bandwidth of the EMC standard

Spread spectrum clock signals are used in electronic devices to reduce the electromagnetic interference (EMI). In this paper we investigate clock signals with frequency or time interval modulation, by short length sequences of arbitrary waveform. The paper focuses on the viewpoints: 1) analyzing the EMI performance with regard to the IF bandwidth, defined by the EMC standard; and 2) considering application-specific restrictions of clock signal parameters such as frequency range or minimum on and off time. As an application example a DC-DC-converter is treated. The results are compared with modulating sequences generated by chaotic maps.

Minimizing charge injection errors in high-precision, high-speed SC-circuits

In high precision circuits much effort is spent in compensating charge injection effects and usually, the resulting errors are determined by simulation only. However, little attention is paid on a detailed analysis of the charge flow although even simple and basic calculations can provide useful insight. In this paper we consider as example a switched capacitor sample-and-hold-circuit that is frequently used in high-resolution, high-speed analog-to-digital converters. As result of our detailed analysis we obtain analytical expressions that are used to derive rules for increasing the precision of the circuit without reducing its operation speed significantly.

Analysis of Discretely Controlled Continuous Systems by means of Embedded Maps

Discretely controlled continuous systems are characterised by their interacting continuous and discrete dynamics, where the continuous subsystem usually represents the system to be controlled and the discrete part describes the controller that switches the continuous system among different operation modes. This paper analyses systems where a perpetual switching of the operation mode has to occur in order to maintain the systems state in a prescribed operating region. It is shown how the analysis of the overall hybrid system can be simplified by using an embedded map that determines the behaviour at the switching instants.

EMI Tuning of Hybrid Systems by Periodic Patterns

Hybrid systems are known to be potential sources of electromagnetic interference due to their principle of recurrently switching voltages and currents. In this paper, we demonstrate different periodic modulation techniques and propose corresponding electromagnetic compatibility optimization methods. A systematic way to optimize finite length modulation sequences is proposed. We prepare mathematical expressions of performance indexes as a base for optimization algorithms. The performance of the different waveform generation methods is verified using a dc-dc converter example. It points out that the optimized waveforms are a powerful tool to shape the power spectrum

Analysis of hybrid systems by means of embedded return maps

The behavioural analysis of hybrid systems is to a large extend an open problem. In this paper it is shown how the construction of an embedded map can be used to determine the characteristics of the output signal of a hybrid system. The method is demonstrated with two DC-DC converter examples.

Electronic power management for bicycles

This paper discusses the power management of an electronic light- and tachometer system for bicycles. The system uses a conventional hub dynamo as energy source. An accumulator battery is charged via a microprocessor controlled AC-DC converter. We develop a circuit model of the hub dynamo. In order to maximize the output power load matching is performed. A simulation analysis as well as measuring results show that the presented solution is more efficient than classical power supply arrangements and offers the basis for new features. We develop a suitable AC-DC converter topology and show its practical performance

Ereignisgesteuerte kontinuierliche Systeme – Eigenschaften und Entwurfsprobleme (Discretely Controlled Continuous Systems – Properties and Design Problems)

Der Beitrag behandelt die Klasse der ereignisgesteuerten kontinuierlichen Systeme, einer wichtigen Unterklasse der hybriden dynamischen Systeme. An Beispielen wird gezeigt, dass derartige Systeme in vielen Anwendungen in Form eines Regelkreises aus einer kontinuierlichen Strecke und einem diskreten Regler auftreten. Die Systemfunktion wird durch diskrete Stelleingriffe des Reglers erzielt, die zwischen den verschiedenen Betriebsmodi der Strecke umschalten und damit eine Änderung der Streckendynamik bewirken. Es werden ein allgemeines, modulares Modell vorgeschlagen, wichtige Eigenschaften dieser Systemklasse hervorgehoben und relevante Analyse- und Entwurfsaufgaben abgeleitet. This publication focusses on discretely controlled continuous systems, an important subclass of hybrid systems. Such systems usually appear as a control loop composed of a continuous plant and a discrete-event controller. To attain a specified function, the controller perpetually switches the plant among its different modes of operation and thereby influences the continuous dynamics. The paper proposes a general hybrid model and demonstrates its application by three examples. Furthermore essential properties of this class are mentioned to emphasize the need for new analysis and design approaches.