Study on Large Air-Gap Bi-directional Wireless Battery Charger for Electric Vehicles Yoo, Kwang Min Department of Electrical Engineering Graduate School, Myongji University -Seoul, South Korea

 Study on Large Air-Gap Bi-directional Wireless Battery Charger for Electric Vehicles 

 by Yoo, Kwang Min

 Department of Electrical Engineering Graduate School, Myongji University Directed by professor Lee Jun Young 

ABSTRACT

 In this paper, we provide battery charging/discharging for electric vehicles, including hybrid car using a wireless power transmission technology. Because the power sources of EV and PHEV are fully or partially supplied from batteries charged from public line, on-board chargers should be mounted. Conventional on-board battery chargers for PHEV or EV have two-stage structure of input current shaper for harmonic reduction followed by DC/DC converter for output control and electrical isolation. And On-board battery charger is installed in the vehicle at all times. So It will account for constant volume of the car. It will contribute a constant fuel consumption of the vehicle by increasing the weight of the electric vehicle. Currently, the most conventional method is plug-in charging, where a copper connected cable forms the power link. There are several disadvantages to this method, which have led to the investigation of inductive charging technology. On-board chargers are burdened by the need for a cable and plug charger, galvanic isolation of the on-board electronics, the size and weight of the charger, and safety and issues with operating in rain and snow. Wireless power transfer (WPT) is an approach that provides a means to address these problems and offers the consumers a seamless and convenient alternative to charging conductively. In addition, it provides an inherent electrical isolation and reduces on-board charging cost, weight and volume. Depletion of fossil fuel reserves and current practice in generation, transmission, distribution, and utilization of energy are major worldwide concerns, for which distributed generation (DG) and harnessing of renewable energy are considered to be partial and acceptable solutions. However, the quality of power delivered by DG systems, particularly those based on wind energy and solar energy, is largely affected by the stochastic nature of their energy production. Consequently, in order to improve the power quality while meeting the demand in the most economical and efficient way, energy suppliers relied on energy storage systems, particularly for DG systems of medium power levels. Among various storage solutions such as flywheels, batteries, super-capacitors, etc., the vehicle-to-grid (V2G) concept, which uses hybrid vehicles or pure electric vehicles (EVs) to store and supply energy back to the grid, is gaining more and more popularity as hybrid.

VIEW FULL PAPER: https://www.mediafire.com/file/ex58p49wwcwl4n0/StudyonLargeAir-GapBi-directionalWirelessBattery.pdf/file

High Efficiency High Power Density Gan Based Power Supply Unit (PSU) for Data Center Application-AKASH NEEL DEY, BE THESIS Presented to the Faculty of The University of Texas at Dallas in Partial Fulfillment of the Requirements for the Degree of MASTER OF SCIENCE IN ELECTRICAL ENGINEERING

 HIGH EFFICIENCY HIGH POWER DENSITY GAN BASED POWER SUPPLY UNIT (PSU) FOR DATA CENTER APPLICATION by AKASH NEEL DEY, BE THESIS 

Presented to the Faculty of The University of Texas at Dallas in Partial Fulfillment of the Requirements for the Degree of MASTER OF SCIENCE IN ELECTRICAL ENGINEERING 

THE UNIVERSITY OF TEXAS AT DALLAS May 2020 

 ABSTRACT

 The ever growing consumption of data and its handling has resulted in huge server stations which cover prime land space and consumes huge amounts of power at low voltages causing high inefficiency. This work attempts to evaluate the design of a GaN based high efficiency and high power density server PSU. A two-stage topology is considered where an active front end rectifier converts 208VAC 3-phase supply to 380VDC. An isolated DC-DC LLC converter employing a planar integrated matrix transformer steps down the 380VDC to 48VDC for further distribution in the server rack. The rectifier switches and the primary switches in the LLC are GaN MOSFETs. The analytical loss and volume model of the converter are derived and a multi-objective design optimization for reduction in loss and volume is performed. Hence, a suitable converter design parameter is selected and a prototype design is considered.

VIEW FULL THESIS:  https://utd-ir.tdl.org/bitstream/handle/10735.1/9249/DEY-THESIS-2020.pdf?sequence=1&isAllowed=y

Fabrication and Characterization of Perovskite–Organic Additive Composites for Micro Light-Emitting Diodes-by Do Hoon Kim February 2022 - Department of Materials Science and Engineering and the Graduate School of Yonsei University in partial fulfillment of the requirements for the degree of Doctor of Philosophy

 

Fabrication and Characterization of Perovskite–Organic Additive Composites for Micro Light-Emitting Diodes

 Dissertation Submitted to the Department of Materials Science and Engineering and the Graduate School of Yonsei University in partial fulfillment of the requirements for the degree of Doctor of Philosophy 

By Do Hoon Kim --February 2022

ABSTRACT

 Development of micro light-emitting diode (LED) pixel array for ultra-high definition (UHD) displays is underway based on LED semiconductor chips, organic LEDs (OLEDs), and quantum dot LEDs (QLEDs). However, these devices have the drawbacks of high cost and complex processes as well as technical problems. Such as an increase in the cost due to the additional transfer process of semiconductor chips and an inaccuracy of mechanical positioning during repeated transfer process. Moreover, OLEDs have the advantage of being applicable to flexible and stretchable substrates, but require expensive organic materials and large-scale equipment. In case of QLEDs, these are not able to be used as a light source because of unstable electroluminescence (EL) property, thus they are used as color filters with a backplane. So, introduction of candidate of new luminescent materials is urgently needed. The perovskite has an adjustable optical band gap, which can be tuned by changing halide anions in the entire visible region. In particular, a primary advantage of the perovskite is that it can be fabricated by simple solution process at low temperatures and this enables the perovskite to be useful for low-cost and large-area micro LED applications. Furthermore, the perovskite LEDs (PeLEDs) are expected to be suitable for nextgeneration displays because they have exhibited unprecedented improvements of luminescence efficiency in a short time compared to conventional LEDs. However, despite these advantages of perovskites, in the case of CsPbI3 crystals for realizing red emission, a high-temperature post-annealing process is essential for suppressing the formation of δ- phase (tilted octahedral) crystals and promoting the formation of a stable α-phase (cubic). In general, a high-temperature process results in better crystallinity with rapid crystal growth. However, perovskite crystals become large and exhibit many surface defects resulting in a rough surface, long diffusion length of excitons, and dissociation of excitons; these factors lead to non-radiative recombination and a high leakage current. Therefore, several strategies, such as the addition of hydrophilic polymer and ligands to the perovskite precursor, have been studied to prevent the surface defects in PeLEDs. In this dissertation, it was demonstrated that functional groups of poly(2-ethyl-2- oxazoline) (PEOXA) lead to coordination bonds with the metal cations of perovskite. PEOXA can decrease formation temperature of the perovskite nanocrystals and improve phase stability as well. PEOXA added to a CsPbBr0.6I2.4 precursor solution successfully suppressed the formation of δ-phase (tilted octahedral) crystals and promoted the formation of stable α-phase (cubic) CsPbBr0.6I2.4 nanocrystals.

LINK FULL THESIS:http://www.riss.kr/search/detail/DetailView.do?p_mat_type=be54d9b8bc7cdb09&control_no=93d6f921fd53111effe0bdc3ef48d419&keyword=PEROVSKITE

SIMULATION PSPICE SINGLE-PHASE SHUNT ACTIVE POWER FiILTER WITH INDUCTIVE LOAD

                                                                  SCHEMATIC PSPICE

PROBE PSPICE

 

 

                                       PROBE TRIGGER S1 ,S2 ,S3 , S4

Ph.D. Dissertation Fast Transient and High Efficiency Voltage-Regulated PWM Buck Converters Jung-Duk Suh Department of Electrical and Computer Engineering The Graduate School Sungkyunkwan University 2019

 

Ph.D. Dissertation Fast Transient and High Efficiency Voltage-Regulated PWM Buck Converters 

Jung-Duk Suh

 Department of Electrical and Computer Engineering 

The Graduate School Sungkyunkwan University 

2019 

 Abstract Fast Transient and High Efficiency Voltage-Regulated PWM Buck Converters This dissertation proposes three pulse-width modulation (PWM) buck converter architectures; two for fast load transient and one for high efficiency. A fast load transient response for small overshoot or undershoot is very important to designing switching regulator because dynamic voltage scaling is regarded as an effective power management solution. The transient response in the conventional voltage mode converter is limited since a type-3 compensator with large capacitors is used. So, it is important to improve slow transient response problems. Also, improving the efficiency under the light load condition of switching regulators is a very important design because of many portable devices stay in standby mode. In common PWM buck converters, the switching loss is dominant in the light load. So, to improve the performance of PWM buck converters in terms of the light-load efficiency, the switching power consumption should be minimized. In this dissertation, to overcome the speed limitation of the PWM control and the light load efficiency, PWM buck converters that can improve both the load transient response and the light load efficiency are proposed. First, a DC-DC converter with active ramp tracking control (ARTC) is presented. When the difference between the output voltage and reference voltage is increased to the threshold voltage in the load transient situation, the ramp bias voltages change and generate a full duty signal to the power switches. This helps restore the output voltage to the reference voltage, improving the load transient response speed and decreasing the overshoot/undershoot at the output voltage. The proposed converter with ARTC improves the load transient response speed and decreases the overshoot/undershoot at the output voltage. This proposed buck converter with ARTC can reduce the overshoot/undershoot at the output by up to 61.1% and the recovery time up to 60.0 % for a 450-mA load current step. Second, a DC-DC converter with inductor current slope control (ICSC) is presented. In load transient period, the slope of the inductor current is increased two times by connecting the parallel inductor of same size as main inductor. It can recover the output voltage quickly and have a consistent fast response time regardless of the load current step size and output voltage. This proposed buck converter with ICSC simulated in a 65-nm CMOS technology reduces the overshoot/undershoot at the output by up to 54.4% and the recovery time up to 82.6% for a 450-mA load current step. Third, a DC-DC converter with chargerecycling gate-voltage swing control is presented. This proposed converter with charge-recycling gate-voltage swing control can improve the power efficiency by reducing the gate-driving loss at the light load. This proposed converter controls the gate-voltage swing with charge-recycling structure according to the load current and has the gate-driving loss reduced by up to 87.7% and 47.2% compared to the conventional full-swing and low-swing designs, respectively. The maximum power conversion efficiency was 90.3% when the input and output voltages are 3.3 V and 1.8 V, respectively.

LINK: http://www.riss.kr/search/detail/DetailView.do?p_mat_type=be54d9b8bc7cdb09&control_no=f17df0f4a93a1c12ffe0bdc3ef48d419&keyword=pwm%20converters

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