High Frequency DC-DC Power Conversion for Automotive LED Driver Applications

This thesis studies high frequency dc-dc power converters for automotive LED driver applications. A high-frequency zero voltage switching (ZVS) integrated-magnetics Ćuk converter is well-suited for automotive LED-driver applications. In this converter, the input and output filter inductors and the transformer are realized on a single magnetic structure, resulting in very low input and output current ripples, thus reducing electromagnetic interference (EMI) and minimizing the required input and output filter capacitances. Active-clamp snubbers are used to mitigate the effects of the transformer leakage inductance. A prototype 1.8~MHz Ćuk converter with integrated magnetics is designed, built and tested. The prototype converter supplies 0.5 A output current to a string of 1-10 LEDs, and achieves 89.6% peak power-stage efficiency. The use of active-clamp snubbers introduces additional conduction and gate-drive losses. This thesis introduces a planar integrated magnetics structure that is designed to minimize the transformer leakage inductance and therefore eliminates the need for snubbers. The planar integrated magnetics structure is optimized using 3D finite element modeling (FEM) tools. Two 1.8 MHz-to-2.4 MHz Ćuk converter prototypes are constructed: one using Silicon MOSFETs and the other using GaN transistors. The former achieves a peak efficiency of 92.9%, while the latter achieves a peak efficiency of 93.5% and a wider ZVS range. Both prototypes maintain greater than 90% efficiency across their wide output voltage range. A new control architecture for the ZVS integrated magnetics Ćuk converter is presented. A Spice-based averaged circuit model is employed to model the converter dynamics. The duty-cycle-to-output-inductor-current transfer function is obtained and an integral compensator is designed to precisely regulate the output inductor current (LED current) over the entire output voltage range of the converter (3 V-to-50 V). To achieve high-resolution PWM dimming, new turn-off and turn-on strategies are proposed. The proposed turn-off strategy reduces the fall time of the LED current by up to 83%, and the turn-on strategy reduces the rise time by up to 43%. The controller is implemented digitally and experimental results are presented. This work also investigates resonant dc-dc converters as an alternative approach for automotive LED driver applications. The LLC resonant dc-dc converter is studied and is found that this converter suffers from high circulating currents, when designed to operate over a wide input and output voltage range. An LC3L resonant dc-dc converter is proposed. The converter exhibits minimal circulating currents. Furthermore, it is shown that when appropriately designed, the converter behaves like a current source, with its output current being independent of the output voltage. This property is particularly favorable for automotive LED driver applications. A 10 MHz LC3L resonant dc-dc converter is designed and simulated. This converter is predicted to achieve greater than 86% efficiency, and be 60% smaller in size compared to the planar integrated magnetics Ćuk converter. Further increase in the switching frequency of automotive LED drivers demands exploring new design techniques and the use of high performance semiconductor devices. This thesis presents high efficiency dc-dc converters operating at very high frequencies using custom monolithic GaN-based half-bridge power stages with integrated gate drivers. A new gate driver circuitry is introduced, which enables efficient converter operation at very high switching frequencies, while maintaining very low quiescent power consumption. While using only n-type transistors in the GaN process, the proposed gate driver emulates complementary operation commonly employed in CMOS processes. A family of monolithic GaN chips is designed to operate over switching frequencies in the range of 20-400 MHz,</p

Design optimization of contactless power transfer systems for electric vehicles using electromagnetic resonant coupling

Contactless power transfer (CPT) systems have been gaining considerable attention and have achieved tremendous technology advancements across a wide variety of utilizations in the past decade. CPT technologies offer promising advantages and open up new avenues for development of numerous real-world applications. Of particular importance is the implementation of CPT systems on the charging of electric vehicles (EV), which are considered as a sustainable alternative that will effectively address global fossil energy scarcity and climate change issues in the future. The overarching aim of this thesis is to investigate and improve the operation performance of CPT systems for contactless EV charging. Optimized high-performance CPT systems are expected to be the ultimate goal for EV wireless charging in the following century. In the CPT applications, some certain characteristic outputs and parameters such as overall system efficiency, RMS power transfer, air gap and resonant frequency are considered as key performance metrics to be addressed. These crucial metrics and properties have been emphasized throughout this thesis. The electromagnetic resonant coupling technique has been put forward and adopted for most designed prototypes in this thesis in order to optimize the overall performance of CPT systems. The research methodology development, model designs, implementations and results analysis of the thesis are undertaken from the perspective of both power electronics and electromagnetics towards achieving the main objectives of the research. With focuses on overall system efficiency, real transfer power to load, air gap, frequency, magnetic coupler design, shielding materials, inner shielding distance and misalignment characteristics, a range of studies have been conducted in the thesis based on the proposed methodology, enhanced simulation models and laboratory prototypes. A number of important contributions have been made by the thesis. The four most significant contributions are: Firstly, the originally developed methodology for the CPT research of the thesis – the research flowchart system based on the preliminary natural resonant frequency probe and anticipation method. This uniquely proposed method for this thesis has been used to effectively probe, track and narrow down the most appropriate resonant frequency range to be chosen for CPT systems to perform with, towards reaching an optimized status of electromagnetic resonant coupling in terms of CPT technology-based EV charging. Secondly, the magnetic coupler modular-based CPT designs for investigating overall system performance optimization. As a result, in the thesis, a novel small-sized CPT prototype that is based on a geometrically improved H-shaped magnetic coupler, with ferromagnetic cores, passive aluminium shielding, an SS compensation topology and electromagnetic resonant coupling, has been proposed as an optimal design solution. Thirdly, approximating a CPT system to operate in close proximity to its calculated natural resonant frequency point by tuning and controlling system operating frequency could effectively lead to an overall system performance optimization most of the time in practical applications using electromagnetic resonant coupling, whereas setting the system operating frequency exactly at its calculated natural resonant frequency to make the system maximally operate at an extreme state of magnetic resonance may only produce a partial optimization from perspective of the system parameters and outputs. Fourthly, reasonable trade-offs between performance metrics are required to be considered and evaluated in order to achieve a feasible overall CPT system optimization. Through the detailed analysis of the results, model outcome comparisons, explanations on findings, limitation discussions and holistic system evaluations, this thesis is devoted to report and provide a series of newly proposed solutions and innovatively designed CPT systems. These solutions are supported by empirical findings, conclusions and contributions, which may encourage further pursuits of system performance optimizations for high-power high-frequency CPT charging technologies applied for future EV, despite methodological limitations, experiment restrictions and external uncertainties

High frequency electromagnetic links for wireless power transfer

This thesis investigates inductive links used in wireless power transfer systems. Inductive power transfer can be used as a power delivery method for a variety of portable devices, from medical implants to electric vehicles and is gaining increased interest. The focus is on high quality factor coils and MHz operation, where accurate measurements are difficult to achieve. Fast models of all pertinent aspects of inductive power transfer systems for constant cross section coils are developed. These models are used to optimise a new coil winding pattern that aims to increase efficiency in volume constrained scenarios. Measurement systems are developed to measure coil Q factors in excess of 1,000. The prototype measurement systems are verified against models of that system, as well as finite element simulations of the coil under test. Shielding of inductive power transfer systems is then investigated. A structure typically used at GHz frequencies, the artificial magnetic conductor, is miniaturised as an alternative to conventional ferrite backed ground plane shielding. Finite element simulation shows this structure significantly improves link efficiency. The artificial magnetic conductor prototype does not result in a gain in efficiency expected, however it does display the properties expected of an artificial magnetic conductor, including increased coupling factor. Finally, an unconventional inductive power transfer system is presented where transmitter and receiver are up to 6m away from each other and of radically different size. This system provides mW level power to remote devices in a room, for example thermostats or e-ink displays. Conventional approaches to design do not consider the distortion of the magnetic field caused by metallic objects in the room. It was found that treating the system as a decoupled receiver and transmitter provides a better prediction of received power in real world environments.Open Acces

Electronics for Sensors

The aim of this Special Issue is to explore new advanced solutions in electronic systems and interfaces to be employed in sensors, describing best practices, implementations, and applications. The selected papers in particular concern photomultiplier tubes (PMTs) and silicon photomultipliers (SiPMs) interfaces and applications, techniques for monitoring radiation levels, electronics for biomedical applications, design and applications of time-to-digital converters, interfaces for image sensors, and general-purpose theory and topologies for electronic interfaces

The 1992 4th NASA SERC Symposium on VLSI Design

Papers from the fourth annual NASA Symposium on VLSI Design, co-sponsored by the IEEE, are presented. Each year this symposium is organized by the NASA Space Engineering Research Center (SERC) at the University of Idaho and is held in conjunction with a quarterly meeting of the NASA Data System Technology Working Group (DSTWG). One task of the DSTWG is to develop new electronic technologies that will meet next generation electronic data system needs. The symposium provides insights into developments in VLSI and digital systems which can be used to increase data systems performance. The NASA SERC is proud to offer, at its fourth symposium on VLSI design, presentations by an outstanding set of individuals from national laboratories, the electronics industry, and universities. These speakers share insights into next generation advances that will serve as a basis for future VLSI design

Heterogeneous Chip Multiprocessor: Data Representation, Mixed-Signal Processing Tiles, and System Design

With the emergence of big data, the need for more computationally intensive processors that can handle the increased processing demand has risen. Conventional computing paradigms based on the Von Neumann model that separates computational and memory structures have become outdated and less efficient for this increased demand. As the speed and memory density of processors have increased significantly over the years, these models of computing, which rely on a constant stream of data between the processor and memory, see less gains due to finite bandwidth and latency. Moreover, in the presence of extreme scaling, these conventional systems, implemented in submicron integrated circuits, have become even more susceptible to process variability, static leakage current, and more. In this work, alternative paradigms, predicated on distributive processing with robust data representation and mixed-signal processing tiles, are explored for constructing more efficient and scalable computing systems in application specific integrated circuits (ASICs). The focus of this dissertation work has been on heterogeneous chip multi-processor (CMP) design and optimization across different levels of abstraction. On the level of data representation, a different modality of representation based on random pulse density modulation (RPDM) coding is explored for more efficient processing using stochastic computation. On the level of circuit description, mixed-signal integrated circuits that exploit charge-based computing for energy efficient fixed point arithmetic are designed. Consequently, 8 different chips that test and showcase these circuits were fabricated in submicron CMOS processes. Finally, on the architectural level of description, a compact instruction-set processor and controller that facilitates distributive computing on System-On-Chips (SoCs) is designed. In addition to this, a robust bufferless network architecture is designed with a network simulator, and I/O cells are designed for SoCs. The culmination of this thesis work has led to the design and fabrication of a heterogeneous chip multi- processor prototype comprised of over 12,000 VVM cores, warp/dewarp processors, cache, and additional processors, which can be applied towards energy efficient large-scale data processing