20 research outputs found
Design and evaluation of a very high frequency dc/dc converter
Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2007.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Includes bibliographical references (p. 139-143).This thesis presents a resonant boost topology suitable for very high frequency (VHF, 30-300 MHz) dc-dc power conversion. The proposed design is a fixed frequency, fixed duty ratio resonant converter featuring low device stress, high efficiency over a wide load range, and excellent transient performance. A 110 MHz, 23 W experimental converter has been built and evaluated. The input voltage range is 8-16 V (14.4 V nominal), and the selectable output voltage is between 22-34 V (33 V nominal). The converter achieves higher than 87% efficiency at nominal input and output voltages, and maintains efficiency above 80% for loads as small as 5% of full load. Furthermore, efficiency is high over the input and output voltage range. In addition, a resonant gate drive scheme suitable for VHF operation is presented, which provides rapid startup and low-loss operation. The converter regulates the output using high-bandwidth on-off hysteretic control, which enables fast transient response and efficient light load operation. The low energy storage requirements of the converter allow the use of coreless inductors, thereby eliminating magnetic core loss and introducing the possibility of integration. The target application of the converter is the automotive industry, but the design presented here can be used in a broad range of applications where size, cost, and weight are important, as well as high efficiency and fast transient response.by Robert C.N. Pilawa-Podgurski.M.Eng
Architectures and circuits for low-voltage energy conversion and applications in renewable energy and power management
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2012.Cataloged from PDF version of thesis.Includes bibliographical references (p. 337-343).In this thesis we seek to develop smaller, less expensive, and more efficient power electronics. We also investigate emerging applications where the proper implementation of these new types of power converters can have a significant impact on the overall system performance. We have developed a new two-stage dc-dc converter architecture suitable for low-voltage CMOS power delivery. The architecture, which combines the benefits of switched-capacitor and inductor-based converters, achieves both large voltage step-down and high switching frequency, while maintaining good efficiency. We explore the benefits of a new soft-charging technique that drastically reduces the major loss mechanism in switched-capacitor converters, and we show experimental results from a 5-to-1 V, 0.8 W integrated dc-dc converter developed in 180 nm CMOS technology. The use of power electronics to increase system performance in a portable thermophotovoltaic power generator is also investigated in this thesis. We show that mechanical non-idealities in a MEMS fabricated energy conversion device can be mitigated with the help of low-voltage distributed maximum power point tracking (MPPT) dc-dc converters. As part of this work, we explore low power control and sensing architectures, and present experimental results of a 300 mW integrated MPPT developed in 0.35 um CMOS with all power, sensing and control circuitry on chip. The final piece of this thesis investigates the implementation of distributed power electronics in solar photovoltaic applications. We explore the benefits of small, intelligent power converters integrated directly into the solar panel junction box to enhance overall energy capture in real-world scenarios. To this end, we developed a low-cost, high efficiency (>98%) power converter that enables intelligent control and energy conversion at the sub-panel level. Experimental field measurements show that the solution can provide up to a 35% increase in panel output power during partial shading conditions compared to current state-of-the-art solutions.by Robert C. N. Pilawa-Podgurski.Ph.D
Merged Two-Stage Power Converter With Soft Charging Switched-Capacitor Stage in 180 nm CMOS
In this paper, we introduce a merged two-stage dc-dc power converter for low-voltage power delivery. By separating the transformation and regulation function of a dc-dc power converter into two stages, both large voltage transformation and high switching frequency can be achieved. We show how the switched-capacitor stage can operate under soft charging conditions by suitable control and integration (merging) of the two stages. This mode of operation enables improved efficiency and/or power density in the switched-capacitor stage. A 5-to-1 V, 0.8 W integrated dc-dc converter has been developed in 180 nm CMOS. The converter achieves a peak efficiency of 81%, with a regulation stage switching frequency of 10 MHz.Interconnect Focus Center (United States. Defense Advanced Research Projects Agency and Semiconductor Research Corporation
Submodule Integrated Distributed Maximum Power Point Tracking for Solar Photovoltaic Applications
This paper explores the benefits of distributed power electronics in solar photovoltaic applications through the use of submodule integrated maximum power point trackers (MPPT). We propose a system architecture that provides a substantial increase in captured energy during partial shading conditions, while at the same time enabling significant overall cost reductions. This is achieved through direct integration of miniature MPPT power converters into existing junction boxes. We describe the design and implementation of a high-efficiency (>;98%) synchronous buck MPPT converter, along with digital control techniques that ensure both local and global maximum power extraction. Through detailed experimental measurements under real-world conditions, we verify the increase in energy capture and quantify the benefits of the architecture.National Science Foundation (U.S.) (Grant 0925147
Modular Switched-Capacitor DC-DC Converters Tied with Lithium-Ion Batteries for use in Battery Electric Vehicles
Abstract-This paper presents a modular switched-capacitor (SC) dc-dc converter based electric drive system for battery electric vehicles. In such a system, modularized lithium-ion battery cell tied MOSFET SC converters are used instead of the more conventional IGBT boost converter. Following the drive train architecture, the modeling approach for each electrical component, including the battery set, dc-dc and dc-ac converters, ac machines, and their control is discussed. Emphasis is given on state of the art lithium-ion battery models and SC converter design. System level performance is analyzed based on simulation results across drive cycles. Hardware including a three-cell lithium-ion battery tied SC converter module is built and tested. Application notes such as economic and spacing constraints are addressed
Submodule Integrated Distributed Maximum Power Point Tracking for Solar Photovoltaic Applications
Analysis and Design of a High Power Density Flying-Capacitor Multilevel Boost Converter for High Step-Up Conversion
Active Voltage Balancing in Flying Capacitor Multi-Level Converters With Valley Current Detection and Constant Effective Duty Cycle Control
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On the Role of Switch Output Capacitance on Passive Balancing within the Flying Capacitor Multilevel Converter
The Flying Capacitor Multi-Level (FCML) converteris heralded as enabling the utilization of low-voltageswitches within a high-voltage converter by evenly distributingthe voltage stress on a series string of switches through the useof “flying” capacitors. However, this advantage of the converterrequires that the flying capacitors do not deviate too far fromtheir ideal voltage distribution regardless of transients, loaddisturbances, or other parasitics to ensure the switches are notovervolted among other concerns. Previous works have identifiedcertain theoretic combinations of duty cycle and level countwhere the flying capacitor voltages do not naturally balanceand instead diverge. Although seemingly problematic, in practicethis behavior is not observed in practical implementations. Toresolve this discrepancy between FCML theory and experiment,we analyze the impact of switch output capacitance on theflying capacitor voltage balancing dynamics, and illustrate thiscapacitance has a naturally balancing effect