Relación de transformación óptima para fuente de alimentación de lámpara de descarga de barrera dieléctrica

Las lámparas excimer de descarga de barrera dieléctrica (DBD), son modeladas como cargas capacitivas y requieren de fuentes de alimentación de alto voltaje para establecer la descarga en el gas. Debido a la baja capacitancia de la lámpara, la operación de la fuente es afectada por las capacitancias parasitas de sus componentes. Con el fin de entender los efectos de las capacitancias y seleccionar un convertidor óptimo, este proyecto presenta el análisis teórico del convertidor resonante boost considerando las capacitancias de los interruptores y el impacto de la relación de transformación en la eficiencia del sistema. El convertidor óptimo es implementado y utilizado para la validación experimental.Dielectric Barrier Discharge (DBD) excimer lamps are modeled as capacitive loads and require a high voltaje power supply. Due to the low equivalent capacitance of the lamp, the operation of the power supply is highly affected by the parasitic capacitances of its components. In order to understand the effects of the parasitic capacitances and select an optimum converter, this project presents the theoretical analysis of the boost based resonant converter considering the switches capacitances and studies the impact of the transformer turns ratio in the efficiency of the system. The optimum converter is implemented and used for the experimental validation.Magíster en Ingeniería ElectrónicaMaestrí

Special Power Electronics Converters and Machine Drives with Wide Band-Gap Devices

Power electronic converters play a key role in power generation, storage, and consumption. The major portion of power losses in the converters is dissipated in the semiconductor switching devices. In recent years, new power semiconductors based on wide band-gap (WBG) devices have been increasingly developed and employed in terms of promising merits including the lower on-state resistance, lower turn-on/off energy, higher capable switching frequency, higher temperature tolerance than conventional Si devices. However, WBG devices also brought new challenges including lower fault tolerance, higher system cost, gate driver challenges, and high dv/dt and resulting increased bearing current in electric machines. This work first proposed a hybrid Si IGBTs + SiC MOSFETs five-level transistor clamped H-bridge (TCHB) inverter which required significantly fewer number of semiconductor switches and fewer isolated DC sources than the conventional cascaded H-bridge inverter. As a result, system cost was largely reduced considering the high price of WBG devices in the present market. The semiconductor switches operated at carrier frequency were configured as Silicon Carbide (SiC) devices to improve the inverter efficiency, while the switches operated at fundamental output frequency (i.e., grid frequency) were constituted by Silicon (Si) IGBT devices. Different modulation strategies and control methods were developed and compared. In other words, this proposed SiC+Si hybrid TCHB inverter provided a solution to ride through a load short-circuit fault. Another special power electronic, multiport converter, was designed for EV charging station integrated with PV power generation and battery energy storage system. The control scheme for different charging modes was carefully developed to improve stabilization including power gap balancing, peak shaving, and valley filling, and voltage sag compensation. As a result, the influence on the power grid was reduced due to the matching between daily charging demand and adequate daytime PV generation. For special machine drives, such as slotless and coreless machines with low inductance, low core losses, typical drive implementations using conventional silicon-based devices are performance limited and also produce large current and torque ripples. In this research, WBG devices were employed to increase inverter switching frequency, reduce current ripple, reduce filter size, and as a result reduce drive system cost. Two inverter drive configurations were proposed and implemented with WBG devices in order to mitigate such issues for 2-phase very low inductance machines. Two inverter topologies, i.e., a dual H-bridge inverter with maximum redundancy and survivability and a 3-leg inverter for reduced cost, were considered. Simulation and experimental results validated the drive configurations in this dissertation. An integrated AC/AC converter was developed for 2-phase motor drives. Additionally, the proposed integrated AC/AC converter was systematically compared with commonly used topologies including AC/DC/AC converter and matrix converters, in terms of the output voltage/current capability, total harmonics distortion (THD), and system cost. Furthermore, closed-loop speed controllers were developed for the three topologies, and the maximum operating range and output phase currents were investigated. The proposed integrated AC/AC converter with a single-phase input and a 2-phase output reduced the switch count to six and resulting in minimized system cost and size for low power applications. In contrast, AC/DC/AC pulse width modulation (PWM) converters contained twelve active power semiconductor switches and a common DC link. Furthermore, a modulation scheme and filters for the proposed converter were developed and modeled in detail. For the significantly increased bearing current caused by the transition from Si devices to WBG devices, advanced modeling and analysis approach was proposed by using coupled field-circuit electromagnetic finite element analysis (FEA) to model bearing voltage and current in electric machines, which took into account the influence of distributed winding conductors and frequency-dependent winding RL parameters. Possible bearing current issues in axial-flux machines, and possibilities of computation time reduction, were also discussed. Two experimental validation approaches were proposed: the time-domain analysis approach to accurately capture the time transient, the stationary testing approach to measure bearing capacitance without complex control development or loading condition limitations. In addition, two types of motors were employed for experimental validation: an inside-out N-type PMSM was used for rotating testing and stationary testing, and an N-type BLDC was used for stationary testing. Possible solutions for the increased CMV and bearing currents caused by the implementation of WGB devices were discussed and developed in simulation validation, including multi-carrier SPWM modulation and H-8 converter topology

Analysis of dynamic performance and robustness of silicon and SiC power electronics devices

The emergence of SiC power devices requires evaluation of benefits and issues of the technology in applications. This is important since SiC power devices are still not as mature as their silicon counterparts. This research, in its own capacity, highlights some of the major challenges and analyzes them through extensive experimental measurements which are performed in many different conditions seeking to emulate various applications scenarios. It is shown that fast SiC unipolar devices, inherently reduce the switching losses while maintain low conduction losses comparable with contemporary bipolar technologies. This translates into lower temperature excursions and an enhanced conversion efficiency. However, such high switching rates may trigger problems in the device utilizations. The switching rates influenced by the device input capacitance can cause significant ringing in the output, especially in SiC SBDs. Measurements show that switching rate of MOSFETs increases with increasing temperature in turn on and reduces in turn off. Hence, the peak voltage overshoot and oscillation severity of the SiC SBD increases with temperature during diode turn off. This temperature dependence reduces at the higher switching rates. So accurate analytical models are developed for predicting the switching energy in unipolar SiC SBDs and MOSFET pairs and bipolar silicon PiN and IGBT pairs. A key parameter for power devices is electrothermal robustness. SiC MOSFETs have already demonstrated such merits compared to silicon IGBTs, however not for MOSFET body diodes. This research has quantified this in comparison with the similarly rated contemporary device technologies like CoolMOS. In a power MOSFET, high switching rates coupled with the capacitance of drain and body causes a displacement current in the resistive path of P body, inducing a voltage on base of the parasitic NPN BJT which might forward bias it. This may lead to latch up and destruction if the thermal limits are surpassed. Hence, trade offs between switching energy and electrothermal robustness are explored for the silicon, SiC and superjunction power MOSFETs. Measurements show that performance of body diodes of SiC MOSFETs is the most efficient due to least reverse recovery. The minimum forward current for inducing dynamic latch up decreases with increasing voltage, switching rate and temperature for all technologies. The CoolMOS exhibited the largest latch up current followed by the SiC and silicon power MOSFETs. Another problem induced by high switching rates is the electrical coupling between complementing devices in the same phase leg which manifests as short circuits across the DC link voltage. This has been understood for silicon IGBTs with known corrective techniques, however it is seen that due to smaller Miller capacitance resulting from a smaller die area, the SiC module exhibits smaller shoot through currents in spite of higher switching rates and a lower threshold voltage. Measurements show that the shoot through current exhibits a positive temperature coefficient for both technologies the magnitude of which is higher for the silicon IGBT. The effectiveness of common techniques of mitigating shoot through is also evaluated, showing that solutions are less effective for SiC MOSFET because of the lower threshold voltages and smaller margins for a negative gate bias

Fabrication and analysis of 4H-SiC diodes

Despite the excellent electrical and thermal properties of 4H-silicon carbide (SiC) and the advancements in the field of 4H-SiC epitaxial growth, the existence of defects in the material can considerably reduce the electrical performance of the SiC power devices. Defects can result in low carrier lifetime affecting the on-state resistance of bipolar devices, such as PiN diodes, and increased leakage current affecting the reverse blocking performance of power devices, such as Schottky diodes. A commonly found surface morphological defect in available 4H-SiC substrates is the triangular defect. In this thesis, the formation mechanism of this defect and its impact on the electrical performance of the fabricated 4H-SiC PiN diodes is discussed. 4H-SiC PiN diodes were intentionally fabricated on the triangular defects and in areas with no visible morphological defects. The devices were then packaged and tested to assess the impact of these defects on the resulting on-state and reverse leakage characteristics. It was shown for the first time the impact of triangular defects on switching characteristics of 4H-SiC PiN diodes fabricated on- and off-defects. Moreover, triangular defects were characterised using methods including AFM, SEM, Photoluminescence and HRTEM. Other complex structures were observed on the triangular defect using HRTEM such as double positioning boundary (DPB), which resulted in a leakage path through the drift region of the devices and increased the leakage current. Furthermore, this thesis focuses on the fabrication and analysis of 4H-SiC power diodes for high voltage applications with particular focus on improving the performance of 4H-SiC SBDs using a novel metal-semiconductor interface treatment and 4H-SiC PiN diodes using high temperature processing techniques to improve the carrier lifetime, on-state resistance and conductivity modulation of the diode. Carrier lifetime enhancement in 4H-SiC PiN diodes in this thesis was achieved using a combined high temperature oxidation and successive argon annealing process at 1550°C for 1 hour. This resulted in an increase of nearly 45% of the reverse recovery current and approximately 40% of the carrier lifetime. The findings of this study could be potentially used for other 4H-SiC bipolar devices such as IGBTs, BJTs and thyristors. This thesis has also investigated the impact of various surface passivation treatments to improve the quality of the 4H-SiC surface and the metal-semiconductor interface using Mo/Ti, and Ni-4H-SiC Schottky diodes. The most significant outcome of this investigation was the performance of P2O5 treated Mo/SiC Schottky diodes which retained a barrier height equivalent to that of titanium, but with a leakage current lower than any Ni diode, seemingly combining the benefits of both a low- and high-SBH metal. Furthermore, P2O5 treated Mo/SiC Schottky diodes were the only diodes to undergo any significant leakage current reduction after any of the pre-treatments exhibiting exceptionally low leakage, even at 300°C. XPS and SIMS analysis on all Mo/SiC SBDs revealed that the stoichiometry of the SiC underneath the contact was enhanced using P2O5 treatment and that traces of P2O5 were found after removal of the passivation layer and post-treatment metallisation. It was also found that the Mo-4HSiC interface on the P2O5 treated sample was very sharp and uniform compared to the untreated sample where Mo-SiC interface looks uneven and cloudy. The developed novel metal-semiconductor interface treatment can be potentially used for MOS interface improvements

Feature Papers in Electronic Materials Section

This book entitled "Feature Papers in Electronic Materials Section" is a collection of selected papers recently published on the journal Materials, focusing on the latest advances in electronic materials and devices in different fields (e.g., power- and high-frequency electronics, optoelectronic devices, detectors, etc.). In the first part of the book, many articles are dedicated to wide band gap semiconductors (e.g., SiC, GaN, Ga2O3, diamond), focusing on the current relevant materials and devices technology issues. The second part of the book is a miscellaneous of other electronics materials for various applications, including two-dimensional materials for optoelectronic and high-frequency devices. Finally, some recent advances in materials and flexible sensors for bioelectronics and medical applications are presented at the end of the book