This work describes the design of audio amplifiers operating in switching mode. The first part describes basic principles of the power stage switching concept. There is described differences between classes of amplifiers according to technology. The second larger part includes design and construction of the switching amplifiers. Design is implemented, including the preamplifier and power supply. Power supply works in switching mode. The measured parameters of the proposed facility are given in the last part.

The aim of the Master´s thesis is proposing and implementation of computer controlled optical radiation source. The theoretical part describes the photometric, the radiometric quantities, applied components such as LED, the microcontroller and possible methods for the LED brightness control. The development of the device is described from the selection of the individual LEDs to the end of the device assembling and programing. On the several LEDs were made properties measurement. A circuit with microcontroller was designed and then was fabricated. The device was programmed for communication and control from the PC. The entire electronic is fitted in the metal frame of the construction box and finally the device functionality is tested.

No description available.

A dominating source for the radiated acoustic noise from a train at low speeds is the traction motor. This noise originates from electromagnetic forces acting on the structure resulting in vibrations on the surface and thus radiated noise. It is often perceived as annoying due to its tonal nature. To achieve a desirable acoustic behavior, and also to meet legal requirements, it is of great importance to thoroughly understand the generation of noise of electromagnetic origin in the motor and also to be able to control it to a low level. In this work, experimental tests have been performed on a traction motor operated from pulse width modulated (PWM) converter. A PWM converter outputs a quasi-sinusoidal voltage created from switched voltage pulses of different widths. The resulting main vibrations at PWM operation and their causes have been analyzed. It is concluded that an appropriate selection of the PWM switching frequency, that is the rate at which the voltage is switched, is a powerful tool to influence the noise of electromagnetic origin. Changing the switching frequency shifts the frequencies of the exciting electromagnetic forces. Further experimental investigations show that the trend is that the resulting sound power level decreases with increasing switching frequency and eventually the sound power level reaches an almost constant level. The underlying physical phenomena for the reduced sound power level is different for different frequency ranges. It is proposed that the traction motor, similar to a thin walled cylindrical structure, shows a constant vibration over force response above a certain frequency. This is investigated using numerical simulations of simplified models. Above this certain frequency, where the area of high modal density is dominating, the noise reducing effect of further increasing the switching frequency is limited. / <p>QC 20180109</p>

The emergence of silicon-carbide (SiC) devices has been a 'game changer' in the field of power electronics. With desirable material properties such as low-loss characteristics, high blocking voltage, and high junction temperature operation, they are expected to drastically increase the power density of power electronics systems. Recent state-of-the-art designs show the power density over 17 ; however, certain factors limit the power density to increase beyond this limit. In this dissertation, three key factors are selected to increase the power density of SiC-based grid-connected three-phase converters. Throughout this dissertation, the techniques and strategies to increase the power density of SiC three-phase converters were investigated. Firstly, a magnetic integration method was introduced for the coupled inductors in the interleaved three-phase converters. Due to limited current-capacity compared to the silicon insulated-gate bipolar transistors (Si-IGBTs), discrete SiC devices or SiC modules, operate in parallel to handle a large current. When three-phase inverters are paralleled, interleaving can be used, and coupled inductors are employed to limit the circulating current. In Chapter 2, the conventional integration method was extended to integrate three coupled inductors into two; one for differential-mode circulating current and the other for common-mode circulating current. By comparing with prior research work, a 20% reduction in size and weight is demonstrated. From Chapter 3 to Chapter 5, a full-SiC uninterruptible power supply (UPS) was investigated. With the high switching frequency and fast switching dynamics of SiC devices, strategies on electromagnetic inference become more important, compared to Si-IGBT based inverters. Chapter 3 focuses on a common-mode equivalent circuit model for a topology and pulse width modulation (PWM) scheme selection, to set a noise mitigation strategy in the design phase. A three terminal common-mode electromagnetic interference (EMI) model is proposed, which predicts the impact of the dc-dc stage and a large battery-rack on the output CM noise. Based on the model, severe deterioration of noise by the dc-dc stage and battery-rack can be predicted. Special attention was paid on the selection of the dc-dc stage's topology and the PWM scheme to minimize the impact. With the mitigation strategy, a maximum 16 dB reduction on CM EMI can be achieved for a wide frequency range. In Chapter 4, an active PWM scheme for a full-SiC three-level back-to-back converter was proposed. The PWM scheme targets the size reduction of two key components: dc-link capacitors and a common-mode EMI filter. The increase in switching frequency calls for a large common-mode EMI filter, and dc-link capacitors in the three-level topology may take a considerable portion in the total volume. To reduce the common-mode noise emission, different combinations of the voltage vectors are investigated to generate center-aligned single pulse common-mode voltage. By such an alignment of common-mode voltage with different vector combinations, noise cancellation between the rectifier and the inverter can be maximally utilized, while the balancing of neutral point voltage can be achieved by the transition between the combinations. Also, to reduce the size of the dc-link capacitor for the three-level back-to-back converter, a compensation algorithm for neutral point voltage unbalance was developed for both differential-mode voltage and the common-mode voltage of the ac-ac stage. The experimental results show a 4 dB reduction on CM EMI, which leads to a 30% reduction on the required CM inductance value. When a 10% variation of neutral point voltage can be handled, the dc-link capacitance can be reduced by 56%. In Chapter 5, a 20 kW full-SiC UPS prototype was built to demonstrate a possible size-reduction with the proposed PWM scheme, as well as a selection of topologies and PWM schemes based on the model. The power density and efficiency are compared with the state-of-the-art Si-IGBT based UPSs. Chapter 6 seeks to improve power density by a change in a modulation method. Triangular conduction mode (TCM) operation of the three-level full-SiC inverter was investigated. The switching loss of SiC devices is reported to be concentrated on the turn-on instant. With zero-voltage turn-on of all switches, the switching frequency of a three-level three-phase SiC inverter can be drastically increased, compared to the hard-switching operation. This contributes to the size-reduction of the filter inductors and EMI filters. Based on the design to achieve a 99% peak efficiency, a comparison was made with a full-SiC three-level inverter, operating in continuous conduction mode (CCM), to verify the benefit of the soft switching scheme on the power density. A design procedure for an LCL filter of paralleled TCM inverters was developed. With 3.5 times high switching frequency, the total weight of the filter stage of the TCM inverter can be reduced by 15%, compared to that of the CCM inverter. Throughout this dissertation, techniques for size reduction of key components are introduced, including coupled inductors in parallel inverters, an EMI filter, dc-link capacitors, and the main boost inductor. From Chapter 2 to 5, the physical size or required value of these key components could be reduced by 20% to 56% by different schemes such as magnetic integration, EMI mitigation strategy through modeling, and an active PWM scheme. An optimization result for a full-SiC UPS showed a 40% decrease in the total volume, compared to the state-of-the-art Si-IGBT solution. Soft-switching modulation for SiC-based three-phase inverters can bring a significant increase in the switching frequency and has the potential to enhance power-density notably. A three-level three-phase full-SiC 40 kW PV inverter with TCM operation contributed to a 15% reduction on the filter weight. / Doctor of Philosophy / The power density of a power electronics system is regarded as an indicator of technological advances. The higher the power density of the power supply, the more power it can generate with the given volume and weight. The size requirement on power electronics has been driven towards tighter limits, as the dependency on electric energy increases with the electrification of transportation and the emergence of grid-connected renewable energy sources. However, the efficiency of a power electronics system is an essential factor and is regarded as a trade-off with the power density. The size of power electronics systems is largely impacted by its magnetic components for filtering, as well as its cooling system, such as a heatsink. Once the switching frequency of power semiconductors is increased to lower the burden on filtering, more loss is generated from filters and semiconductors, thus enlarging the size of the cooling system. Therefore, considering the efficiency has to be maintained at a reasonable value, the power density of Si-based converters appears to be saturated. With the emergence of wide-bandgap devices such as silicon carbide (SiC) or gallium nitride (GaN), the switching frequency of power devices can be significantly increased. This is a result of superior material properties, compared to Si-based power semiconductors. For grid-connected applications, SiC devices are adopted, due to the limitations of voltage ratings in GaN devices. Before commercial SiC devices were available, the power density of SiC- based three-phase inverters was expected to go over 20 𝑘𝑊 𝑑𝑚3 ⁄ . However, the state-of-the art designs shows the power density around 3 ~ 4 𝑘𝑊 𝑑𝑚3 ⁄ , and at most 17 𝑘𝑊 𝑑𝑚3 ⁄ . The SiC devices could increase the power density, but they have not reached the level expected. The adoption of SiC devices with faster switching was not a panacea for power density improvement. This dissertation starts with an analysis of the factors that prevent power density improvement of SiC-based, grid-connected, three-phase inverters. Three factors were identified: a limited increase in the switching frequency, large high-frequency noise generation to be filtered, and smaller but still significant magnetic components. Using a generic design procedure for three-phase inverters, each chapter seeks to frame a strategy and develop techniques to enhance the power density. For smaller magnetic components, a magnetic integration scheme is proposed for paralleled ac-dc converters. To reduce the size of the noise filter, an accurate modeling approach was taken to predict the noise phenomena during the design phase. Also, a modulation scheme to minimize the noise generation of the ac-ac stage is proposed. The validity of the proposed technique was verified by a full-SiC three-phase uninterruptible power supply with optimized hardware design. Lastly, the benefit of soft-switching modulation, which leads to a significant increase in switching frequency, was analyzed. The hardware optimization procedure was developed and compared to hard-switched three-phase inverters.

Η παρούσα διπλωματική εργασία πραγματεύεται τη μελέτη, το σχεδιασμό, την πρσοομοίωση και την κατασκευή κυκλώματος για την οδήγηση και τον έλεγχο στροφών κινητήρα τύπου DC Brushless.Η εργασία αυτή εκπονήθηκε στο εργαστήριο Ηλεκτρομηχανικής Μετατροπής Ενέργειας του τμήματος Ηλεκτρολόγων Μηχανικών και Τεχνολογίας Ηλεκτρονικών Υπολογιστών. Σκοπός της παρούσας εργασίας είναι η μελέτη και η κατασκευή κυκλώματος τριφασικού αντιστροφέα ισχύος για να επιτύχουμε οδήγηση και έλεγχο κινητήρα τύπου DC Brushless. Ο κινητήρας αυτού του τύπου είναι Σύγχρονος κινητήρας Μόνιμου Μαγνήτη. Για το λόγο αυτό το πρώτο πράγμα που μελετήθηκε στην παρούσα εργασία είναι κάποιες θεμελιώδεις ιδιότητες του μαγνητικού πεδίου, καθώς και τα χαρακτηριστικά των μαγνητικών υλικών που χρησιμοποιούνται σε τέτοιους τύπους κινητήρων. Στην συνέχεια αναλύονται οι κινητήρων Brushless DC ως προς την κατασκευή τους καθώς και τη λειτουργία τους. Παρατίθενται οι εξισώσεις που περιγράφουν τη λειτουργία τους και οι χαρακτηριστικές ροπής-ταχύτητας και επιπλέον γίνεται σύγκριση αυτών με κινητήρες άλλων τύπων. Ακολουθεί η περιγραφή της προσομοίωσης του συστήματος η οποία πραγματοποιήθηκε στο πρόγραμμα προσομοίωσης ηλεκτρικών κυκλωμάτων Simulink του Matlab. Αναλύεται η λογική στην οποία βασιστήκαμε για την προσομοίωση και παρατίθενται οι κυματομορφές της τάσης και του ρεύματος σε διάφορα σημεία του κυκλώματος. Έπειτα γίνεται μια θεωρητική ανάλυση του κυκλώματος του αντιστροφέα που κατασκευάστηκε καθώς και όλων των άλλων κυκλωμάτων και στοιχείων που απαιτήθηκαν για τη λειτουργία της διάταξης. Επιπλέον περιγράφεται η μέθοδος παλμοδότησης που χρησιμοποιήθηκε για την έναυση/σβέση των διακοπτικών στοιχείων ισχύος. Τέλος γίνεται αναλυτική παράθεση του τελικού κυκλώματος που κατασκευάστηκε. Προχωράμε με την περιγραφή των ιδιοτήτων και δυνατοτήτων του μικροελεγκτή που χρησιμοποιήθηκε στην πλακέτα μας, καθώς επίσης και με τη λογική που ακολουθήθηκε κατά τον προγραμματισμό του. Τέλος παραθέτονται τα αποτελέσματα των πειραμάτων και τα παλμογραφήματα που ελήφθησαν κατά τη διεξαγωγή τους. Γίνεται σχολιασμός των αποτελεσμάτων αυτών και αξιολόγηση της κατασκευής. / This thesis is focused in the study and development of a Drive System for a DC Brushless motor. This work was conducted in the Laboratory of Electromechanical Energy Conversion, at the department of Electrical and Computer Engineering, in the University of Patras, Greece. DC Brushless motors, have been used in the last years they are used in a number of applications. They combine all the benefits of a DC motor, such as their operation simplicity and their linear characteristics, avoiding the brushes and the necessary excitation of DC motors, making them a suitable choice for low and medium power applications. The main purpose of this project is the Study and Construction of a Three-Phase Voltage Source Inverter for the control of the performance of a DC Brushless Motor by the implementation of a Scalar control. This thesis began with the simulation of the motor, since it is necessary for the understanding of its dynamic behavior. Then an analysis on the design and construction of the required circuit boards is done. Finally the used microcontroller (dsPIC family) was studied thoroughly, before writing the necessary code(C & assembly) for open and closed loop control. Finally, measurements were taken for the open loop control system. Conclusions were made as far as the behavior of the motor and ways to optimize the control were discussed.

<div> Recent advancements of health monitoring sensing technologies are enabling plethora of new applications in a variety of biomedical areas. In this work, we present a new sensing technology that enables a fully autonomous monitoring of urinary tract infection (UTI). UTI is the second most common infection in the human body caused by bacterial pathogens, and costs millions of dollars each year to the patients and the health care industry. UTI is easily treatable using antibiotics if identified in early stages. However, when early stage identification is missed, UTI can be a major source of serious complications such as ascending infections, loss of kidney function, bacteremia, and sepsis. Unfortunately, the limitations of existing UTI monitoring technologies such as high cost, time-intensive sample preparation, and relatively high false alarm rate prohibit reliable detection of UTI in early stages. The problem becomes more serious in certain patient groups such as infants and geriatric patients suffering from neurodegenerative diseases, who have difficulties in realizing the symptoms and communicating the symptoms with their caregivers. In addition to the aforementioned difficulties, the fact that UTI is often asymptomatic makes early stage identifications quite challenging, and the reliable monitoring and detection of UTI in early stages remain as a serious problem.</div><div> To address these issues, we propose a diaper-embedded, self-powered, and fully autonomous UTI monitoring sensor module that enables autonomous monitoring and detection of UTI in early stages with minimal effort. The sensor module consists of a paper-based colorimetric nitrite sensor, urine-activated batteries, a boost dc-dc converter, a low-power sensor interface utilizing pulse width modulation, a Bluetooth low energy module for wireless transmission, and a software performing calibration at run-time. </div><div> To further optimize the sensor module, a new fully integrated DC-DC converter with low-profile and low ripple is developed. The proposed DC-DC converter maintains an extremely low level of output voltage ripples in the face of different battery output voltages, which is crucial for realizing low-noise sensor interfaces. Since the DC-DC converter is a part of a module embedded into a diaper, it is highly desirable for the DC-DC converter to have a small physical form factor in both area and height. To address this issue, the proposed DC-DC converter adopts a new charge recycling technique that enables a fully integrated design without utilizing any off-chip components. In addition, the DC-DC converter utilizes sub-module sharing techniques – multiple modules share a voltage buffer and a recycle capacitor to reduce power consumption and save chip area. The DC-DC converter provides a regulated voltage of 1.2V and achieves a maximum efficiency of 80% with a 300ohm load resistance. The output voltage ripple is in the range of 19.6mV to 26.6mV for an input voltage ranging from 0.66 to 0.86V.<br></div>

Near-field wireless power transfer (WPT) technology facilitates the energy autonomy of heterogeneous systems, significantly augmenting complementary metal-oxide-semiconductor field-effect-transistor (CMOS) technology. In low-power wearable devices, existing power conditioning integrated circuits do not maximize the power factor (PF) for rectification and power conversion efficiency (PCE) due to multiple conversion. Additionally, there is no core power management for the entire power flow. The majority of the research focuses on active rectifiers, which reduce the turn-on voltage for rectification. Certain studies target the output voltage regulation via feedback to the transmitter or direct battery charging without power maximization. Firstly, this study investigates a high-power factor WPT front-end circuit that is namely the mono-periodic switching rectifier (MPSR) and implemented in a 0.18µm 1.8V/5V CMOS process. Integrated phase synchronizers are used to align the waveshape of a wirelessly-coupled sinusoidal voltage source in a receiving coil to the corresponding conducting current. Using this approach, the PF can be increased from roughly 0.6 to unity without requiring any wireless or wired feedback to the transmitter. The proposed MPSR can also provide AC-DC rectification, and step up and down the sinusoidal voltage source's peak amplitude using a pulse-width modulator. Measured voltage conversion ratios range between 0.73X and 2X, and the PF can be boosted up to unity. Secondly, the wireless power system-on-chip (WPower-SoC) is proposed and implemented in a 0.18µm 1.8V/3.3V CMOS process. The WPower-SoC integrating power management can provide rectification, output voltage regulation, and battery charging. Additionally, the implementation of feedforward envelope detection (FED) can reduce the variation in a wireless power link and improve load transient responses. Simulated results demonstrate that 5% of the output voltage regulation is improved when an output load changes. Moreover, the FED reduces approximately 40% of the transient response time. Overshoot and undershoot voltages are decreased by 23% and 26.5%, respectively. The measured output voltage regulates at 3.42V and can supply output power up to 342mW. A temperature sensor as part of the power management core remains active when the WPT receivers enter sleep mode to prolong the battery usage time. In the final part of this study, a nano-watt high-accuracy temperature sensing core is implemented in a 0.18µm 1.8V/3.3V CMOS process that can self-compensate the temperature shift without the need for additional compensating techniques that consume extra power.

De nombreux systèmes utilisent des convertisseurs électroniques de puissance fonctionnant en modulation de largeur d'impulsions (MLI) comme organe de réglage ou de commande. On peut en particulier citer les entraînements à vitesse variable, les alimentations à découpage ou les filtres actifs. L'objectif du travail est de contribuer à l'étude en temps discret du fonctionnement de ces systèmes lorsqu'ils sont munis d'une commande numérique dont la période d'échantillonnage est synchronisée sur la période de modulation de largeur d'impulsions. Pour cela nous avons développé une méthode originale qui consiste à écrire les équations différentielles qui décrivent la dynamique du système en remplaçant sur chaque période de modulation les fonctions binaires qui représentent les états successifs (ON ou OFF) des semi-conducteurs de puissance par un développement limité en série de Fourier. En introduisant de manière judicieuse dans les équations différentielles du système, des termes harmoniques des fonctions binaires qui décrivent les états des interrupteurs, cette manière de procéder nous a permis de décomposer l'étude en deux étapes : · dans une première étape en limitant le développement en série de Fourier des fonctions binaires décrivant les états des interrupteurs à leur premier terme (c'est-à-dire à leurs valeurs moyennes) nous avons construit un modèle discret d'ordre zéro qui rend compte de l'effet moyen de la découpe MLI, · dans une deuxième étape nous avons construit un modèle dynamique approché de l'écart existant entre le modèle d'ordre zéro et le modèle détaillé du système. Ce modèle fournit une bonne estimation des ondulations induites par la découpe MLI dans les grandeurs du système. Pour le cas des entraînements par moteurs synchrones à aimants permanents alimentés par onduleurs de tension nous avons ainsi pu mettre en évidence que l'étude de la stabilité des boucles des courants du moteur à partir du modèle d'ordre zéro reste valable en présence des ondulations dues à la MLI pour autant qu'on utilise une MLI symétrique avec rafraîchissement des références une fois par période. / Nowadays, a large number of systems are using Pulse Width Modulation (PWM) Power Electronic Converters as control part. These systems can, for example, be variable-speed drives, switching power supplies or active filters. The goal of this work is to contribute to the study of operation of this type of system when they are equipped with a digital control part of which the sampling period is synchronized on the modulation one. After having shown how the equations of these systems can be written down and indicated how their evolution in closed loop operation can be described by using iterative maps, we have tried to develop an approach which allows simplifying this study. The iterative map method has been used in order to take into account the “sequential “character of these systems, i.e. the fact that the control signals are sequences of events which correspond to the changes of the state of the converter semiconductor switches. Therefore we have developed an original method which consists in replacing on each modulation period, in the differential equations describing the system dynamics, the binary functions representing the successive ON or OFF states of the power semiconductors, by a limited Fourier series development of these functions. This method has allowed splitting the study of these systems into two steps: • in the first step a “zero order” model was built. This first model, which provides the average effect of the PWM pulse pattern, has been obtained by limiting the Fourier series development of the binary functions describing the states of the converter switches, to their first term, the one corresponding to their average values on the PWM period, • in the second step we have introduced an approached dynamic model characterising the error between the zero order model and the exact model of the system. This model was built by considering a well chosen number of harmonic terms of the binary functions describing the ON-OFF states of the switches in the differential equations of the system. By combining the error model and the zero order model we have been able to estimate in which measure the ripples induced by the PWM modulation affect the results of the system stability study made by using the zero order model. For the case of Permanent Magnets Synchronous Motors fed by Voltage Source Inverters we have shown that the study of the stability of the motor currents loops made with the zero order model remains valid in the presence of ripples induced by the PWM, as long as a symmetrical modulation is used, with references which are refreshed one time on each switching period.

An efficient Light Emitting Diode (LED) lamp driver circuit is proposed for retrofitting the conventionally used incandescent lamps with existing TRIAC dimmer. The dimming feature in a wide range of firing angle from 30¢X to 130¢X can be accomplished by means of double pulse-width modulation (DPWM) and analog current regulation. The LED lamp driver adopts a flyback converter with an auxiliary active power MOSFET for synchronous switch and an associated inductor for zero voltage switching (ZVS), leading to lower switching loss and thus achieving a higher circuit efficiency. In the thesis, the mode operation of the driver circuit is analyzed and the design equations are derived accordingly. A laboratory circuit is designed for an 50 W LED lamp which is composed of 45 high-brightness white LEDs in series. Experiments are carried out to test the circuit performances with two dimming schemes. The experimental results indicate that the driver can achieve a circuit efficiency of 95 % at the rated output. When the LED lamp is dimmed, the circuit efficiency with DPWM is higher than that with the analog current regulation. On the other hand, the LED lamp dimmed by analog current regulation has a higher efficiency but a less color shift by DPWM.