Publication Date

2018

Document Type

Dissertation

Committee Members

Marian K. Kazimierczuk (Advisor), Kuldip Rattan (Committee Member), Xiaodong (Frank) Zhang (Committee Member), Saiyu Ren (Committee Member), Yan Zhuang (Committee Member)

Degree Name

Doctor of Philosophy (PhD)

Abstract

Energy efficient, wide-bandwidth, and well-regulated dc-dc power converters are in great demand in today's emerging technologies in areas such as medical, communication, aerospace, and automotive industries. In addition to design and selection of the converter components, a robust closed-loop modeling is very essential for reliable power-electronic systems. Two closed-loop control techniques for power converters exist: voltage-mode control and current-mode control. The principles of voltage-mode control have been explored in great depths by researchers over the last two decades. However, the dynamic modeling of current-mode controlled dc-dc power converters has many uncharted areas that needs careful attention. Two main methods exist under the category of current-mode control: peak current-mode control and average current-mode control. Both of these control strategies are very attractive in applications that require fast control speeds, improved voltage regulation, and improved power supply noise rejection ratio. In recent technological advancements, where high noise immunity and tight regulation are desired, the average current-mode control has proven to be a superior choice, when compared to other control techniques for power converters. In this dissertation, a complete systematic theoretical framework for analysis, design, characterization, and measurements of the dc-dc converters with average current-mode control is introduced. To overcome the drawbacks of the traditional average current-mode control method, a new, true-averaged current-mode control technique is proposed. The new technique is implemented on the basic converter topologies namely, buck, boost, and buck-boost. The dynamic small-signal models of the converter power-stages are developed using the circuit-averaging technique. The inner-current loop of the power converters is designed and their frequency-domain, time-domain, and pole-zero domain characteristics are exploited. Subsequently, the outer-voltage loop is designed in the presence of current-controlled power stage and the overall converter performance is evaluated against dynamically-varying operating conditions. A laboratory prototype of a buck-boost converter for 12 V to 5 V at 25 W operating at 200 kHz was designed, built, and measured. The theoretically predicted results were validated both through simulations and experiments. The techniques to measure the small-signal open-loop and closed-loop transfer functions are also provided. Excellent agreement between the theoretical and experimental results were observed.

Page Count

319

Department or Program

Ph.D. in Engineering

Year Degree Awarded

2018

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