Increasing the power density of the DC-DC converters requires the size and weight of the magnetic components, such as inductors and transformers, to be reduced. In this thesis, the losses in nanocrystalline inductor cores are characterised and analysed, including the traditional core loss and the gap loss caused by the air gap fringing flux. The loss calculations will form a basis for the design and optimisation of high power inductors for DC-DC converters for EV applications. This thesis first characterises experimentally the core losses in four nanocrystalline cores over a range of operating conditions that are representative of those encontered in typical high power converter applications, including non-sinusoidal waveforms and DC bias conditions. The core losses are assessed by the measured B-H loops and are characterised as a function of DC flux density, showing that for a fixed AC induction level, the losses can vary by almost an order of magnitude as the DC bias increases and the duty ratio moves away from 0.5. The results provide a more complete picture of the core loss variations with both DC and AC magnetisations than is available in manufactures’ data sheets. An electromagnetic finite element (FE) model is used to examine the gap loss that occurs in finely laminated nanocrystalline cores under high frequency operation. The loss is significant in the design example, contributing to almost half of the total inductor loss, and the gap loss is highly concentrated in the region of the air gap. The dependence of the gap loss on key inductor design parameters and operating condtions is also explored. An empirical equation is derived to provide a design-oriented basis for estimating gap losses. Thermal finite element analysis is used to estimate the temperature rise and identify the hot spot in a nanocrystalline inductor encapsulated in an alumimium case. The temperature distribution in the core largely corresponds to the non-uniform distribution of the gap loss. The thermal FEA can also be used to evaluate different thermal management methods to optimise the design for a more compact component. The FE modelling of gap loss and the thermal predictions are validated experimentally on a foil-wound Finemet inductor, showing good agreement between the predictions and measurements under various operating conditions.

In this paper we describe an approach to generating low-order models of spiral inductors that accurately capture the dependence on both frequency and geometry (width and spacing) parameters. The approach is based on adapting a multiparameter Krylov-subspace based moment matching method to reducing an integral equation for the three dimensional electromagnetic behavior of the spiral inductor. The approach is demonstrated on a typical on-chip rectangular inductor. / Singapore-MIT Alliance (SMA)

Au cours de la dernière décennie, le grand public a pris conscience de l’impact économique, social et environnemental de la pollution dû à l’usage des énergies fossiles. Non seulement du fait de la raréfaction des énergies fossiles mais aussi la limitation de leur usage et de leur impact sur l’environnement est important, ce qui amène à remplacer ces sources traditionnelles par des sources d’énergie alternatives, propres et renouvelables. Depuis ces dernières années l’industrie automobile montre un intérêt croissant pour la conception de véhicules électriques hybrides. Cependant la transition vers un parc de voitures plus électriques est limitée par le coût encore élevé, l’autonomie et le temps de recharge électrique long. Un système distribué de transfert de puissance par induction (IPT) peut être une solution pour rallonger l’autonomie des véhicules électriques (EV’s) en permettant la recharge tout en roulant, grâce à des séries d’inducteurs couplés, réduisant aussi la taille de la batterie nécessaire et donc son coût. Le concept de transfert de puissance sans fil a été introduit il y a plus de 20 ans. Aujourd’hui les avancées technologiques et les hauts rendements des composants rendent cette solution viable pour les applications transport. Ce travail de thèse concerne donc le design et le contrôle d’un système de recharge efficace par induction d’une batterie à bord d’un véhicule sujet dans ce cas à des désalignements entre inducteurs. Un état de l’art sur le principe de transfert de puissance par induction est effectué et une structure DD-BP est proposée afin d’avoir un bon rendement pour le transfert de puissance et une moindre sensibilité en présence de désalignement et au mouvement, un inducteur étant sous la route, l’autre à bord du véhicule. Pour cela les dimensionnements de ces inducteurs et les analyses de l’impact des structures des inducteurs sont effectués par simulation à éléments finis des champs magnétiques produits et échangés. De plus, un modèle circuit équivalent et un modèle mathématique ont été établis incluant des circuits compensateurs. L’ensemble du système IPT a été séparé en deux parties, l’une alternative (AC), l’autre continue (DC). La simulation du modèle électrique (PSIM) et mathématique (MATLAB) montrent une bonne correspondance, à l’aide du modèle mathématique une étude complète a été possible en fonction des fréquences, des courants et des désalignements selon les 3 axes. La structure IPT spécifique pour cette application EV montre la faisabilité et l’efficacité de la recharge de la batterie en mouvement, en fixant une fréquence, malgré un assez grand entrefer (distance z entre la route et le châssis) et des variations de couplage (désalignement x ou y). Ce bon comportement est obtenu par le design des inducteurs et le bon contrôle des convertisseurs de recharge de la batterie (double buck-boost). / During the last decades, public awareness of the environmental, economic and social consequences of using fossil fuels has considerably grown. Moreover, not only the supply of fossil resources is limited, but also the environmental impact represents a relevant issue, so leading to an increased consideration of clean and renewable alternatives to traditional technologies. During recent years, the automotive industry has shown a growing interest in electric and hybrid electric vehicles. However, the transition to all-electric transportation is now limited by the high cost of the vehicles, the limited range and the long recharging time. Distributed IPT (inductive power transfer) systems can be the solution to the range restrictions of EVs by charging the vehicle while driving thanks to, a set of loosely coupled coils, so also reducing required battery size as well as overall cost of the vehicle. The concept of wireless power transfer via magnetic induction was introduced two decades ago. Nowadays, this technology is becoming more efficient and more suitable for new applications. This dissertation made an effort to address the requirements of IPT EV battery charging system with high efficiency and good tolerance to misalignment. A survey of a typical IPT for EV application has been reported, while a concentrated DD-BP solution has been proposed in order to enhance the IPT charging system capability of transferring power to a stationary EV with good efficiency and good tolerance to movement. The current trend in EV battery charging application is represented by the lamped coil system, whose different structures have been reviewed. Moreover, this thesis presented the design of a charging pad magnetic structure, called Double D pad combined with a Bipolar secondary pad, in order to enhance coupling performance. A finite element magnetic analysis has been performed in order to obtain the electric parameters of the proposed magnetic coupler. Furthermore, a mathematical model has been developed by considering the different sides of the system. The mathematical model allows to accurately predict the behavior of inductive coils and coreless transformer. A set of simulation has been carried out in order to compare the analytical and simulated results. The proposed EV IPT system has shown the feasibility of using fixed frequency, single pick up system to transfer power efficiently across a large air gap, with variable coupling. This result has been reached by means of proper design of the charging pad magnetics, of tuning network and of a pick-control based on a buck boost converter topology.

Hydrogen has been identified by the European Commission to be a competitive alternative to fossil fuels within the transport sector in the medium to long perspective. Because of this, an increased understanding is required of the electrical power train present within such vehicles. An integral aspect of these systems is the interface converter, which is located between the fuel cell and the rest of the power train. During the design process of high-powered fuel cell interface converters used in transport applications, it is important to achieve designs of low losses, size and cost. One of the most important parts to achieve these goals is the inductor present within the converter; this is generally the bulkiest part of the converter. To analyse how the inductor’s properties are affected by the converter topology, three different topologies have been analysed: the conventional single-phase boost converter and two versions a two-phase interleaved boost converter, where one uses two single inductors and the other an inversely coupled inductor. These three cases’ steady-state properties have then been characterised and used to select designs minimising either the self-inductance or the flux levels induced in the inductor, while maintaining a permissible input current ripple and continuous conduction mode throughout the converter’s operational region. Finally, a preliminary design framework has been developed for both the single and coupled inductors, where initially the so-called geometrical constant method and then a multiobjective optimisation method using evolutionary algorithms was used to design each inductor. Provided the optimisation framework was fed appropriate bounds and constraints, it was able to outperform the geometrical method. For the case of an inductor operating under a high DC bias, it was found that it is better to premiere a core material with a high saturation flux density over a reduction in the losses. Moreover, the inductor’s dimensions are reduced by using an inversely coupled core irrespective if the switching frequency was the same or halved compared to the test case of the conventional boost converter inductor. Irrespective of the switching frequency, a coupling factor of 0.55 is deemed to provide the best overall performance and most robust design at the price of a slightly worse transient response compared to using a stronger coupling. / Vätgas har blivit identifierat av den Europeiska kommissionen till att vara ett konkurrenskraftigt alternativ till fossila bränslen inom transportsektorn i ett mellan- till långtidsperspektiv. På grund av det krävs en bättre förståelse av det elektriska drivsystemet som används inom dessa fordon. En viktig del av ett sådant drivsystem är gränssnittsomvandlaren som är placerad emellan bränslecellen och de resterande delarna av drivsystemet. Under designprocessen av gränssnittsomvandlare till kraftfulla bränsleceller, ämnade till att användas inom transportapplikationer, är det viktigt att uppnå designer med låga förluster, storlek och kostnad. En av de viktigaste delarna till att uppnå dessa målsättningar är induktansen; detta är generellt den största delen av omriktaren. Som metod till att analysera hur induktorns egenskaper påverkas av omriktarens topologi, har tre olika topologier analyserats: den konventionella boost omriktaren och två versioner av en två-fas interleaved boost omriktare, där en använder två induktanser och den andra en omvänt kopplad induktans. Dessa tre olika falls egenskaper under stabilt tillstånd karakteriserades och sedan användes för att välja designer som antingen minimerade själv-induktansen eller järnkärnans magnetiska flöde, medan ett godkänt rippel och kontinuerlig ledningsläge säkerhetsställdes för hela omriktarens operativa region. Slutgiltigen formulerades en reluktansbaserad dimensionerings metod för varje fall av induktor, där initialt den såkallade geometriska konstant metoden och sedan en multiobjektiv heuristisk optimerings metod, som baserades på evolutionära algoritmer, användes för att designa induktanserna. Förutsatt optimerings algoritmen fick ta del av korrekta gränser och begränsningar, utklassade den geometriska metoden. För induktanser utsatta för stora DC-komponenter i strömmen, är det bättre att premiera material med en hög mättningsgrad för den magnetisk flödestäthet över låga järnförluster. Utöver det är induktorns dimensioner reducerade genom att använda en omvänt kopplad induktor oavsett om samma eller en halverad switch frekvens användes jämfört med testfallet av den konventionella boost omvandlarens induktans. Oavsett switch frekvensen, en kopplings faktor på 0.55 ansågs ge den bästa prestandan samt mest robusta designen, till priset av ett någorlunda sämre transitenrespons jämfört med en starkare kopplingsfaktor.

A high-precision mixed-signal mismatch measurement technique for metal-oxide metal (MoM) capacitors as well as the design of a 13-GHz 5-bit 360-degree phase shifter are presented. This thesis presents a high-precision, mixed-signal mismatch measurement technique for metal-oxide–metal capacitors. The proposed technique incorporates a switched-capacitor op amp within the measurement circuit to significantly improve the measurement precision while relaxing the resolution requirement on the backend analog-to-digital converter (ADC). The proposed technique is also robust against multiple types of errors. A detailed analysis is presented to quantify the sensitivity improvement of the proposed technique over the conventional one. In addition, this thesis proposes a multiplexing technique to measure a large number of capacitors in a single chip and a new layout to improve matching. A prototype fabricated in 180 nm CMOS technology demonstrates the ability to sense capacitor mismatch standard deviation as low as 0.045% with excellent repeatability, all without the need of a high-resolution ADC. The 13-GHz 5-bit 360-degree phase shifter consists of 2 stages. The first stage utilizes a delay line for 4-bit 180-degree phase shift. A second stage provides 1-bit 180-degree phase shift. The phase shifter includes gain tuning so as to allow a gain variation of less than 1 dB. The design has been fabricated in 180 nm CMOS technology and measurement results show a complete 360◦ phase shift with an average step size of 10.7◦ at 13-GHz. After calibration the phase shifter presented an output gain S21 of 0.5 dB with a gain variation of less than 1 dB across all codes at 13-GHz. The remaining s-parameter testing showed a S22 and S11 below -11 dB and a S12 below -49 dB at 13 GHz.