Switch-mode power supplies (SMPS's) not only convert energy, they also consume it. Typical operational efficiencies are approximately 25 to 60% for linear power supplies, and approximately 50-90% for switching power supplies. This means that products whose end-use electronics are dc, such as televisions and DVD players, could consume 50% less power when operating if the power supply were upgraded from 40% efficiency to 80% efficiency. Savings can occur not only from using SMPS's instead of linear power supplies, but also from specifying highly efficient switching power supplies. In many cases, efficiencies are still lagging to keep costs down, since the power consumption is considered to be relatively low (40W-700W range). Over time, however, efficiency improvement strategies will pay back based on the cost of energy. Therefore three common flyback converter topologies have been studied through this thesis in the Low (15W), Medium (40W), and High (150W) Power levels. Efficiency analysis on the three power level topologies showed that the greatest opportunity for efficiency improvement existed in the 40W (medium power) topology. Efficiency improvement and measurement approaches are investigated and an optimized medium-power flyback converter is proposed and implemented resulting in an efficiency improvement from 57.8% to 83.6%. / Graduation date: 2004

A gate driver IC with programmable driving strength to reduce electromagnetic interference (EMI) in SMPS is presented in this thesis. The design builds on previous segmented gate driver designs that have been used to improve light load efficiency. The presented solution is to dynamically adjust the output resistance Rout at the arrival of each gate pulse to minimize EMI while maintaining low switching loss. Dynamically adjusting Rout is not possible with conventional gate driver designs. Thus, a segmented gate driver is designed and fabricated in the AMS 0.35μm 40V HVCMOS process. Unlike traditional snubber circuits, the proposed method does not require extra discrete components that dissipate energy. Experimental results indicate up to a 7dBμV improvement in peak Conducted EMI (CEMI) between 20 MHz and 30 MHz and a 150μV/m improvement in peak Radiated EMI (REMI) between 88 MHz and 216 MHz.

A gate driver IC with programmable driving strength to reduce electromagnetic interference (EMI) in SMPS is presented in this thesis. The design builds on previous segmented gate driver designs that have been used to improve light load efficiency. The presented solution is to dynamically adjust the output resistance Rout at the arrival of each gate pulse to minimize EMI while maintaining low switching loss. Dynamically adjusting Rout is not possible with conventional gate driver designs. Thus, a segmented gate driver is designed and fabricated in the AMS 0.35μm 40V HVCMOS process. Unlike traditional snubber circuits, the proposed method does not require extra discrete components that dissipate energy. Experimental results indicate up to a 7dBμV improvement in peak Conducted EMI (CEMI) between 20 MHz and 30 MHz and a 150μV/m improvement in peak Radiated EMI (REMI) between 88 MHz and 216 MHz.

en Español:Se propone un modelo de FC basado en ecuaciones electroquímicas para predicción del exceso de oxígeno y de la temperatura de la pila, permitiendo además una conexión circuital con la carga. Así mismo, se presenta una técnica de modelado basada en Fuzzy, orientada a la emulación, obteniendo gran precisión con carga computacional reducida. Usando este último modelo se diseña e implementa un emulador. Estos modelos y el sistema de emulación fueron validados usando un sistema experimental.Adicionalmente, diferentes topologías de sistemas de potencia basados en FC se proponen y analizan, obteniendo un criterio de selección dependiendo de la aplicación. Así mismo, se presentan criterios de control para una operación segura y eficiente del sistema. Finalmente, se proponen una metodología para la caracterización de los puntos óptimos de operación, y una estructura de control para operar en esas condiciones óptimas, siendo validados en un sistema experimental representativo del estado del arte. / in English:A new FC modeling approach based on electrochemical equations for thermal and oxygen excess ration prediction with a circuit-based load connection is introduced. A fuzzy-based modeling technique is also proposed for emulation purposes, it reproducing the fuel cell dynamics with a high accuracy and a short computational time. The implementation of a fuel cell emulation system, based on this model, is described and analyzed. The models and the emulation system are experimentally validated by using a benchmark fuel cell system.Different topologies for fuel cell-auxiliary storage devices interaction are also proposed and analyzed, thus giving an architecture selection criterion based on the load profile. Controllers, dynamic constrains and control objectives are designed for a safe and efficient fuel cell operation. Finally, a methodology for the identification of the fuel cell optimal operation conditions has been proposed, and a control strategy for operating in that optimal profile is introduced and validated.

No description available.

<p>This master thesis aim to design and evaluate a high power 3-phase DC/AC and AC/AC converter. The purpose is to use it for an electric motor in an aircraft possibly driving electric actuators, a propeller in an UAV or a small vehicle. Factors such as power loss and weight are of importance and will be estimated using known models supplied by various manufacturers of components. Different topologies of semiconductors suitable for this purpose are examined and presented. Extensive resources have been put to properly select the most suitable switching device according to their power loss and weight.</p><p>The need for filters and protective circuits will be estimated according to regulations of common military avionic standards and will be included in the resulting estimation along with simulations to evaluate their need and importance. Snubber circuits will be presented and their specific ability to reduce voltage transients and switching losses will be examined along with some simulations to illustrate their performance. In the final part an estimation of efficiency and weight of higher and lower power models of the same inverter has been made using the same procedure as presented in this paper. Engineering rules have been formed from these estimations to simply be able to calculate the proportions of a future converter of arbitrary rated power.</p>

Thesis (Ph. D.)--University of Missouri-Columbia, 1999. / Typescript. Vita. Includes bibliographical references (leaves 55-56). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 1999. / Typescript. Vita. Includes bibliographical references (leaves 55-56). Also available on the Internet.

Thesis (Ph. D.)--School of Electrical and Computer Engineering, Georgia Institute of Technology, 2004. Directed by Abhijit Chatterjee. / Vita. Includes bibliographical references (leaves 127-145).

Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2002. / Includes bibliographical references (leaves 95-97). Also available in electronic version. Access restricted to campus users.