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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Integrated EMI Filters for Switch Mode Power Supplies

Chen, Rengang 18 January 2005 (has links)
Because of the switching action, power electronics converters are potentially large EMI noise sources to nearby equipment. EMI filters are necessary to ensure electromagnetic compatibility. Conventional discrete EMI filters usually consist of a large number of components, with different shapes, sizes and form factors. The manufacturing of these components requires different processing and packaging technologies, of which many include labor-intensive processing steps. In addition, due to the parasitics of discrete components, high-frequency attenuation of the filter is reduced and the effective filter frequency range is limited. As a result, discrete EMI filters are usually bulky, high profile, and have poor high-frequency performance. With an aim to solving these issues, this study explores the integration of EMI filters. The goal is to achieve a smaller size, lower profile, better performance and reduced fabrication time and cost via structural, functional and processing integration. The key technology for EMI filter integration is planar electromagnetic integration, which has been a topic of research over the last few years. Most of the previous applications of this technology for switch mode power supplies (SMPSs) were focused on the integration of high frequency power passive electromagnetic components, such as HF transformers, resonant/choke inductors and resonant/blocking capacitors. Almost no work has been done on the subject of EMI filter integration. Since the major function of EMI filters is to attenuate, instead of propagate, energy at the switching frequency and its harmonics, the required technology and design objectives are very different from those of other components. High-frequency modeling of the integrated structure becomes more essential since the high-frequency performance becomes the major concern. New technology and a new model need to be developed for EMI filter integration. To bridge this gap between existing technologies and what is necessary for EMI filter integration, this dissertation addresses technologies and modeling of integrated EMI filters. Suitable integration technologies are developed, which include reducing the equivalent series inductance (ESL) and equivalent parallel capacitance (EPC), and increasing, instead of reducing, the high frequency losses. Using the multi-conductor lossy transmission-line theory, a new frequency domain model of integrated LC structure is developed and verified by experimental results. Through detailed electromagnetic analysis, the equations to calculate the required model parameters are derived. With the developed frequency domain and electromagnetic model, the characteristic of integrated LC modules can be predicted using geometry and material data. With the knowledge obtained from preliminary experimental study of two integrated EMI filter prototypes, a technology is developed to cancel structural winding capacitance of filter inductors. This can be realized by simply embedding a thin conductive shield layer between the inductor windings. With the resultant equivalent circuit and structural winding capacitance model, optimal design of the shield layer is achieved so that EPC can be almost completely cancelled. Applying this technology, an improved integrated EMI filter with a much simpler structure, a much smaller size and profile, and much better HF performance is designed, constructed and verified by experiment. The completed parametric and sensitivity study shows that this is potentially a very suitable technology for mass production. The integrated RF EMI filter is studied, as well. Its frequency domain model is developed based on multi-conductor lossy transmission-line theory. With the model parameters extracted from the finite element analysis (FEA) tool and the characterized material properties, the predicted filter characteristic complies very well with that of the actual measurement. This model and modeling methodology are successfully extended to study the RF CM&DM EMI filter structure, which has not been done before. To model more complicated structures, and to study the interaction between the RF EMI filter and its peripheral circuitry, a PSpice model with frequency dependent parameters is given. Combining the structural winding capacitance cancellation and the integrated RF CM&DM EMI filter technologies, a new integrated EMI filter structure is proposed. The calculation results show that it has the merits of the two employed technologies, hence it will have the best overall performance. / Ph. D.
2

Three Dimensional Passive Integrated Electronic Ballast for Low Wattage HID Lamps

Jiang, Yan 03 April 2009 (has links)
Around 19% of global power consumption and around 3% of global oil demand is attributable to lighting. After the first incandescent lamp was invented in 1879, more and more energy efficient lighting devices, such as gas discharge lamps, and light-emitting diodes (LED), have been developed during the last century. It is estimated that over 38% of future global lighting energy demand could be avoided by the use of more efficient lamps and ballasts [1]. High intensity discharge (HID) lamps, one category of gas discharge lamp, have been widely used in both commercial and residential lighting applications due to their merits of high efficacy, long life, compact size and good color rendition [2-4]. However, HID lamps require a well-designed ballast to stabilize the negative VI characteristics. A so-called ignitor is also needed to provide high voltage to initiate the gas discharge. Stringent input harmonic current limits, such as the IEC 61000-3-2 Class C standard, are set for lighting applications. It is well-known that high-frequency electronic ballasts can greatly save energy, improve lamp performance, and reduce the ballast size and weight compared with the conventional magnetic ballast. However, a unique phenomenon called acoustic resonance could occur in HID lamps under high-frequency operation. A low-frequency square wave current driving scheme has proved to be the only effective method to avoid acoustic resonance in HID lamps. A typical electronic HID ballast consist of three stages: power factor correction (PFC), DC/DC power regulation and low-frequency DC/AC inverter. The ignitor is usually integrated in the inverter stage. The three-stage structure results in a large size and high cost, which unfortunately offsets the merit of the HID lamp, especially in low-wattage applications. In order to make HID lamps more attractive in low-wattage and indoor applications, it is critical to reduce the size, weight and cost of HID ballasts. This dissertation is aimed at developing a compact HID with an ultra-compact ballast installed inside the lamp fixture. It is a similar concept to the compact fluorescent lamp (CFL), but it is much more challenging than the CFL. Two steps are explored to achieve high power density of the HID ballast. The first step is to improve the system structure and circuit topology. Instead of a three-stage structure, a two-stage structure is proposed, which consists of a single-stage power factor correction (SSPFC) AC/DC front-end and an unregulated DC/AC inverter/ignitor stage. An SSPFC AC/DC converter is proposed as the front-end. A DCM non-isolated flyback PFC semi-stage and a DCM buck-boost DC/DC semi-stage share the semiconductor switch, driver and PWM controller, so that the component count and cost can be reduced. The proposed SSPFC AC/DC front-end converter can achieve a high power factor, low THD, low bulk capacitor voltage, and the desired power regulation with a simple control circuit. Because the number of high-frequency switches is reduced compared to that of state-of-the-art two-stage HID ballast topologies, the switching frequency can be increased without sacrificing high efficiency, so the passive component size can be reduced. The power density of the whole ballast is increased using this two-stage structure. It results in a 2.5 times power density (6 W/in3) improvement compared to the commercial product (2.4 W/in3). The power density of the converter in discrete fashion usually suffers as a result of poor three-dimensional (3D) volume utilization due to a large component count and the different form factor of different components. In the second step, integration and packaging technologies are explored to further increase the power density. A 3D passive integrated HID ballast is proposed in this dissertation. All power passive components are designed in planar shape with a uniform form factor to fully utilize the three-dimensional space. In addition, electromagnetic integration technologies are applied to achieve structural, functional and processing integration to reduce component volume and labor cost. System partitioning, integration and packaging strategies, and implementation of major power passive integration, including an integrated EMI filter, and an integrated ignitor, will be discussed in the dissertation. The proposed integrated ballast is projected to double the power density of the discrete implementation. By installing the HID ballast inside the lamp fixture, the ambient temperature for the ballast will be much higher than the conventional separately installed ballast, and combined with a reduced size, the thermal condition for the integrated ballast will be much more severe. A thermal simulation model of the integrated ballast is built in the IDEAS simulation tool, and appropriate thermal management methods are investigated using the IDEAS simulation model. Experimental verification of various thermal management methods is provided. Based on the thermal management study, a new integrated ballast with improved thermal design is proposed. / Ph. D.

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