The scope of this work can be summarized by three main aspects of DC-DC power converters. The first aspect is soft switching topologies to improve conversion efficiency for On-Board Converters or Point of load (POL) converters, the second aspect is load adaptive control techniques to improve all load efficiency for battery powered DC-DC converters that are applied to mobile devices, and the third aspect is dynamic performance improvement techniques to improve load transient in voltage regulators. Topologies and control techniques for DC-DC converters are presented after reviewing loads powering requirements and steady-state and transients design challenges.

The design optimization of DC-DC converters requires the optimum selection of several parameters to achieve improved efficiency and performance. Some of these parameters are load dependent, line dependent, components dependent, and/or temperature dependent. Designing such parameters for a specific load, input and output, components, and temperature may improve single design point efficiency but will not result in maximum efficiency at different conditions, and will not guarantee improvement at that design point because of the components, temperature, and operating point variations. The ability of digital controllers to perform sophisticated algorithms makes it easy to apply adaptive control, where system parameters can be adaptively adjusted in response to system behavior in order to achieve better performance and stability. The use of adaptive control for power electronics is first applied with the Adaptive Frequency Optimization (AFO) method, which presents an auto-tuning adaptive digital controller with maximum efficiency point tracking to optimize DC-DC converter switching frequency. The AFO controller adjusts the DC-DC converter switching frequency while tracking the converter minimum input power point, under variable operating conditions, to find the optimum switching frequency that will result in minimum total loss and thus the maximum efficiency. Implementing variable switching frequencies in digital controllers introduces two main issues, namely, limit cycle oscillation and system instability. Dynamic Limit Cycle Algorithms (DLCA) is a dynamic technique tailored to improve system stability and to reduce limit cycle oscillation under variable switching frequency operation. The convergence speed and stability of AFO algorithm is further improved by presenting the analysis and design of a digital controller with adaptive auto-tuning algorithm that has a variable step size to track and detect the optimum switching frequency for a DC-DC converter. The Variable-Step-Size (VSS) algorithm is theoretically analyzed and developed based on buck DC-DC converter loss model and directed towered improving the convergence speed and accuracy of AFO adaptive loop by adjusting the converter switching frequency with variable step size. Finally, the efficiency of DC-DC converters is a function of several variables. Optimizing single variable alone may not result in maximum or global efficiency point. The issue of adjusting more than one variable at the same time is addressed by the Multivariable Adaptive digital Controller (MVAC). The MVAC is an adaptive method that continuously adjusts the DC-DC converter switching frequency and dead-time at the same time, while tracking the converter minimum input power, to find the maximum global efficiency point under variable conditions. In this research work, all adaptive methods were discussed, theoretically analyzed and its digital control algorithm along with experimental implementations were presented.

In this thesis, integrated active filter auxiliary power modules (AFAPMs) is presented in electrified vehicle applications. A topological evaluation is conducted particularly for the auxiliary power module (APM) applications in the electrified vehicles. Several primary and secondary base topologies are compared in terms of VA rating and performance. Multiple input/output topology configurations are compared with different connection configurations and control schemes. The MOSFET loss analysis is given. Based on the MOSFET loss analysis, the modular full bridge current doubler with input-series-output-parallel configuration presents better performance in terms of the switch efficiency and cost analysis. Bulk capacitor banks occupy large volume and impact the reliability in the traction inverter and HV battery charger in the vehicle applications. A capacitor-less design is relatively urgent for the next generation electrified vehicle. Active filter (AF) is one potential solution to reduce the corresponding dc-link capacitance. However, additional components are required which increases the system complicity and decreases its reliability. Hence, it would be great to integrate the AF into the LV battery charger for the vehicle applications. Based on the power switch requirements, the AFAPM is evaluated for traction inverter and HV battery charger, respectively. The evaluation result shows that the AFAPM for the HV battery charger system is a feasible and attractive solution. Furthermore, a simple and effective dual-mode dual-voltage charging system operating principle is proposed. The integrated AFAPM converter charges the LV battery when the vehicle is running and operates as an AF when the vehicle is connected to the grid and the HV battery is charging. Hence, the low-frequency second-order harmonic current is alleviated without a bulk capacitor bank or an extra AF circuit in the HV battery charger. For magnetic design, there is a trend toward integration and planarization. Two planar transformers are built for two different AFAPM prototypes. A minimized leakage inductance method is presented and implemented on a 20:1 center-tapped planar transformer. Three different integrated AFAPM converters are proposed. By applying these AFAPM converters, the required extra components to form the AF for the HV battery charger are reduced and thus the cost, size and weight for the dual-voltage charging system in the electrified vehicle applications can be reduced. Two prototypes are built. The experiments show promising results confirming the effectiveness of the proposed converters. / Dissertation / Doctor of Philosophy (PhD)

The move toward electric vehicles (EVs) has a significant impact to reduce greenhouse gas (GHG) emissions and make transportation more eco-friendly. Fast-charging stations play a crucial role in this transition, making EVs more convenient for adoption specifically when driving in long distance. However, the challenge is to create a fast-charging system that can work with the different types of EVs and their varying power needs while still being efficient and effective. In this context, this thesis embarks on this journey by introducing an innovative solution for efficient universal fast charging, spanning both low voltage and high voltage battery systems. A novel, configurable dual secondary resonant converter is proposed, which empowers the charging module to extend its output range without imposing additional demands on the resonant tank components. This solution addresses the pressing need for a wide output voltage range in fast-charging standard in the growing EV landscape. To ensure optimal performance across a broad voltage and power range, the thesis employs an analytical model for LLC resonant converters to optimize the resonant components. This strategic component selection aims to achieve the desired output voltage and power range while minimizing conduction losses. The proposed topology and design methodology are rigorously validated through the development of a 10 kW prototype. Furthermore, the study introduces a two degrees of freedom (2DoF) control scheme for the proposed LLC resonant converter with the configurable dual secondary LLC converter topology. An analytical model is formulated to guide the selection of control parameters, ensuring coverage of the desired output voltage and power range without compromising system efficiency. The steady-state analytical model is utilized for determining optimized control parameters at each operating point within the converter's output range. To enhance the charging module's power density and efficiency, a high-frequency litz-wire transformer design methodology is introduced. The transformer's core size is optimized to achieve high power density and efficiency, while the winding configuration is chosen to minimize conduction losses. Finite Element Analysis (FEA) simulations validate transformer losses and operating temperatures. The culmination of this research is the development of a 30 kW charging module prototype. This prototype features an LLC resonant converter with a configurable dual secondary and two degrees of freedom control for output voltage control. The component ratings, estimated losses, and power board design are carefully considered to create a compact and efficient charging module. Experimental testing across a universal output voltage and power range con rms the effectiveness of the proposed solution. In summary, this thesis presents a comprehensive approach to design of a module for EV fast charging application addressing voltage range, efficiency, and component optimization, resulting in the successful development of a high-performance charging module prototype. / Thesis / Doctor of Engineering (DEng)

付記する学位プログラム名: 京都大学卓越大学院プログラム「先端光・電子デバイス創成学」 / 京都大学 / 新制・課程博士 / 博士(工学) / 甲第24620号 / 工博第5126号 / 新制||工||1980(附属図書館) / 京都大学大学院工学研究科電気工学専攻 / (主査)教授 土居 伸二, 教授 小嶋 浩嗣, 准教授 薄 良彦, 教授 引原 隆士 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

The objective of the thesis is to introduce a new fuzzy logic control application, develop the associated mathematical theory and prove the concept and its advantages through comparative simulation with existing, classical, methods. A stable fuzzy logic controller for the master-slave current sharing loop of a paralleled DC-DC system is presented that exhibits a considerably improved large signal performance over the presently employed, small signal designed compensators, both in terms of system response and control effort. Because of high system complexity, the present small signal designs are unable to give a good response for large load changes and line transients. Fuzzy logic, by dealing naturally with nonlinearities, offers a superior controller type, for this type of applications. The design uses a PID expert to derive the fuzzy inference rules, and simulation results show a good parameter insensitive transient response over a wide range load-step responses, e.g., from 25% to 75% of the nominal load. Current sharing control is formulated as a tracking problem and stability is ensured through adaptation or supervisory control on a Lyapunov trajectory. The technique benefits also from the heuristic approach to the problem that overcomes the complexity in modeling such systems and, hence, offers a practical engineering tool, amenable to both analog and digital implementations. / Ph. D.

This diploma thesis deals with the design of a partially integrated charge pump in 0.25 micron technology ACMOS. The work is divided into two main parts, theoretical and practical. The theoretical section describes in detail various topologies of higher voltage generation of a charge pump and selected methods of regulating the output voltage of charge pumps. The practical part deals with the the actual design of a charge pump together with the arguments for the choice of the TPVD topology and the type of the regulation. Three regulation methods of a charge pump were implemented, tested and are dealt with: Pulse Skip, Constant frequency and PWM. There are 3 sub chapters, each describing a different regulation method, defining all the key elements of the design of such a charge pump and the results of the simulations are discussed. Conclusion of the thesis summarizes the results of the design of charge pumps, comparing them on the basis of the chosen type of output voltage regulation.

No description available.

Dans l’objectif d’une augmentation en puissance des piles à combustible pour satisfaire les besoins énergétiques des applications embarquées, une solution consiste à augmenter la taille des assemblages. Dès lors, des problèmes de disparités fluidique, thermique et électrique peuvent survenir dans le cœur des piles et conduire ainsi à l’apparition de défaut. La pile à combustible, de par sa nature de source électrique basse tension – fort courant, requiert d’être couplée au réseau électrique embarqué par l’intermédiaire d’un convertisseur statique. Ce dernier peut alors être employé pour agir de façon corrective sur la pile et aussi de corriger les défaillances qui en sont liées. Dans cette perspective, le convertisseur doit avoir en permanence un retour sur l’état de santé de la pile. Pour cela, une méthode de détection et d'identification de défaut de type noyage et d’assèchement pour une pile du type PEMFC a été approfondie. Cette méthode simple, économique en capteurs, se base sur la mesure de 3 tensions de cellule judicieusement sélectionnées et localisées sur la pile. Ainsi, l’utilisation de l’information « spatiale », qui correspond à la position de la mesure de tension dans la pile permet d’identifier les défauts. Le principe de la détection localisée nous amène alors à considérer le concept de pile segmentée qui consiste à séparer électriquement la pile en 3 parties de façon à ce que des convertisseurs associés puissent agir électriquement sur chaque segment. L’action peut être du type tout ou rien, ou contrôlée. Cette dernière offre davantage de degrés de liberté, et est moins contraignante pour la pile d’un point de vue électrique. Pour choisir comment réaliser cette action, une étude comparative de plusieurs topologies de convertisseur est effectuée. Les structures alimentées en courant répondent au mieux aux contraintes électriques d’une PEMFC et sont donc privilégiées, de même que la nécessité d’une isolation galvanique imposée par la segmentation de la pile. Au final, une topologie de BOOST isolé résonant est apparue comme étant la topologie répondant au mieux à l’ensemble des critères (plage de fonctionnement, performances énergétiques, nombre de composants). L’ensemble convertisseur global intègre ainsi trois structures unitaires qui permettent d'offrir une modularité, une action indépendante sur chaque segment et de garantir une disponibilité du système grâce à un fonctionnement dégradé. Pour cela, la stratégie de commande de l’ensemble convertisseur intègre les informations issues de la méthode de détection. La thèse se termine avec le dimensionnement complet d’un pré-prototype du convertisseur avec le choix des composants actif et passifs, et du système de refroidissement associé. / In the objective of fuel cell power increase in order to satisfy energetic requirements for embedded applications, a solution consists in increasing the size of fuel cell stack assemblies. As possible consequence, fluidic or thermal disparity problems may occur in the fuel cell core and lead to the appearance of faults. The fuel cell, which is a low voltage-high current electrical source, needs to be connected to the on-board electrical network thanks to a static converter. This latter can be used in order to perform a corrective action in the aim of reducing disparities in the stack and also correcting resulting faults. In this perspective, the converter should permanently get information about fuel cell state of health. Hence, a fault detection and identification method for PEMFC has been explored. This method which is simple and requires only few sensors is based on 3 voltage measurements judiciously selected and localized over the stack. Using “spatial” information which corresponds to the position of the sensors, allows to identify some characteristic faults. The principle of the localized fault detection leads to consider the segmentation concept for the fuel cell, which in our case is electrically split into three parts and allows an independent control of each segment by the power converter. Electrical action can be “all or nothing” or moderated ones. The latter offers more degree of freedom, and is less constraining from an electrical point of view. In order to execute the action, study of multiple power converter topologies have been done. Among the candidate topologies, current structures are preferred, as well as the necessity of a galvanic isolation required by the segmentation concept. The resonant isolated boost is the adopted structure; as it meets at best the whole criteria. Thus the global converter assembly is composed of three single structures which offer modularity, independent action on each segment, and continuity of service thanks to degraded modes. The detection method is hence implemented in the converter control strategy. This Ph.D. thesis ends with the complete sizing of a power converter pre-prototype together with technological choices for the active, passive and associated cooling components.

High-frequency dc-dc converters are nowadays widely used in a diversity of power electronic applications. High operating frequencies entail a reduction in size of the passive components, such as inductors, capacitors and power transformers. By operating the converter at higher frequencies with conventional hard-switching topologies, the transistor switching losses increase at both turn-on and turn-off. High-voltage converters in the power range of 1-10MW will therefore have excessive switching losses if the switching frequency is higher than 4 kHz. In order to achieve a high-frequency operation with moderate switching losses a number of soft-switched topologies have been studied in [Dem1]. The favourable DC-DC converter was found to be the Dual-Active Bridge when a bi-directional power flow is demanded. Additionally, the Single-Active Bridge (SAB) topology was introduced for the first time. In this thesis the two topologies are thoroughly studied. The dynamic small-signal models are presented and the dynamic behaviour of the converters is discussed in deep. Different control strategies are presented concerning the two converters and the advantages and the disadvantages of the different control strategies are stated. Critical issues as efficiency and stability are presented separately for the two converters. / QC 20101005