This thesis presents the conducted electro-magnetic interference (EMI) prediction results for a continuous conduction mode (CCM) power factor correction (PFC) converter as well as the theoretical analysis for the noise generation and propagation mechanisms. In this thesis, multiple modeling and characterization techniques in the medium and high frequency ranges are developed for the circuit components that are important contributors to the EMI noise, so that a detailed simulation circuit for EMI prediction can be constructed. The conducted EMI noise prediction from the simulation circuit closely matches the measurement results obtained by a spectrum analyzer. Simulation time step and noise separator selection are two important issues for the noise simulation and measurement. These two issues are addressed and the solutions are proposed. The conducted EMI generation and propagation mechanisms are analyzed in a systematic way. Two loop models are proposed to explain the EMI noise behavior. The effects of the PFC inductor, the parasitic capacitance between the device and the heatsink, the rising/falling time of the MOSFET VDS voltage, and the input wires are studied to verify the validity of the loop models. / Master of Science

Due to increasing concerns on the power quality, power factor correction (PFC) has become an important issue in light-emitting diode (LED) lighting applications. A boost converter is one of the most well-known PFC topologies, due to its simple circuitry, simple control scheme and small number of passive components. Even though a boost converter is recognized as a typical PFC converter, its output voltage must be higher than its input voltage. This feature is disadvantageous because the device requires an additional buck-stage for LED lighting systems. As an alternative to the boost converter, a single-ended primary-inductor converter (SEPIC) allows output voltage to be lower or higher than the input voltage. Thus, the SEPIC converter is gaining popularity as a LED driver because it does not require additional power conversion stage. However, designing a controller to meet stability requirements and international standards is quite challenging for SEPIC converters. Additionally, if the digital controller is adopted for its built-in communication features, creating a digitally controlled SEPIC converter would be even more challenging. This thesis focuses on the state-space averaging modeling of the SEPIC PFC converter and the design of controllers based on both analog and digital controls with precise modeling. The proposed SEPIC converter incorporates RC damping circuits to avoid the instability, and thus the entire SEPIC converter becomes a 5th order system. Such a high-order system model was derived mathematically and verified with circuit simulator modeling. After verification of the circuit model, the controller was designed with analog transfer functions and converted to and the discrete domain for digital controller implementation. A 150-W single-switch bridgeless SEPIC PFC converter prototype was built accordingly to verify the design. In addition to the current loop controller design for stability, a feed-forward compensator for is introduced and derived for better waveform quality. Simulation results and experiment results are also presented to verify the complete controller with feed-forward compensation. The Texas Instruments (TI) digital signal processor (DSP) TMS320F28335 was adopted for digital controller implementation. For comparison purpose, the TI UC3854 controller was implemented to verify the analog controller design results. / Master of Science

The More-electric aircraft (MEA) concept has been raised since 1990s in order to increase fuel economy and reduce environmental impact of aircrafts. The fundamental of the concept is to replace pneumatic, hydraulic and mechanical systems in conventional aircrafts with its electrical equivalent that is lighter and more reliable. In this movement, power electronics technology plays a key role in interfacing the new types of electrical loads to the new aircraft electrical power system. One of the major tasks for power electronics circuits in MEA is to transfer aircraft variable frequency AC voltage into DC voltage, which could be conveniently utilized by different types of loads or power buses. The converters carrying out the task is commonly known as "rectifiers". This work aims at designing and constructing rectifiers that can work efficiently and reliably in more-electric aircrafts. One of the major challenge for these rectifiers comes from the complex aircraft environment. The ambient temperature could be as high as 70 ºC. Moreover, active cooling for converters may not be desirable. To deal with this, rectifiers should achieve extreme efficiency (especially at full load) so that all the components are not overheated without active cooling. This work aims at achieving extreme converter efficiency through advanced converter topologies and design. Both single-phase and three-phase rectifiers are discussed in this work. For single-phase rectifiers, this work focused on boost-type power factor correction (PFC) converters due to the promising efficiency and good PFC characteristics. The well-known two-level semi-bridgeless PFC boost rectifier, together with its interleaved and three-level counterparts, are studied and compared in this work. The operation principles of the converters are analyzed. Models and methods for converter efficiency evaluation are discussed. The efficiency evaluation of the topologies shows the advantage of three-level topologies and interleaved topologies in achieving higher efficiency and better thermal management. For three-phase rectifiers, two-level boost rectifier, three-level neutral point clamped (NPC) rectifier and Vienna rectifier are investigated. The evaluation shows the advantage of Vienna rectifier in achieving high efficiency due to reduced switching loss. Based on the evaluation of single-phase and three-phase active rectifiers, the author selected interleaved Vienna rectifier to achieve extreme efficiency and avoid overheating problem. The operation principle of the interleaved Vienna rectifier is introduced, with particular attention paid to the circulating current generated by interleaving operation. The design procedure for achieving maximum efficiency is described. Finally, a prototype of the proposed converter is constructed, which achieves 99.26% efficiency at nominal load. / Master of Science