Synchronous-Conduction-Mode Tapped-Inductor Buck Converter for Low-Power, High-Density Application

General-purpose step-down converter is essential in electronic system for processing energy from high-voltage rail to low-voltage circuits. The applications can be found at the auxiliary supplies in automobile, industrial and communication systems. Buck converter is a common circuit topology to fulfill step-down conversion, especially in low-power application since it is well-studied and straightforward. However, it suffers from low duty cycle under high step-down condition, and typically operates in continuous conduction mode (CCM) that generates large switching loss. On the other hand, as an extension of the buck converter, tapped-inductor (TI) buck converter has larger duty cycle while maintaining the structural simplicity. Therefore, the main objective of this thesis is to explore the potential of TI buck converter as a wide conversion range, high power density and high efficiency topology for low power application. To achieve high efficiency at switching frequency of MHz-level, synchronous conduction mode (SCM) is applied for turn-on losses elimination. The operation principle and power stage design of SCM TI buck is first introduced. The design of high switching frequency coupled inductor is emphasized since its size plays a critical role in power density. Loss breakdown is also provided to perform a comprehensive topological study. Secondly, detailed zero-voltage-switching (ZVS) condition of SCM TI buck is derived so that the converter does not experience redundant circulating energy. The experimental results of 15-W SCM TI buck converter prototypes are provided with 90.7% of peak power stage efficiency. The size of coupled inductor is down to 116 mm3. To enhance light-load efficiency, a variable frequency control scheme based on derived ZVS conditions is implemented with the switching frequency ranging from 2 MHz to 2.9 MHz.

Name thesis:degree_name

Master of Science

Level thesis:degree_level

masters

Discipline thesis:degree_discipline

Electrical Engineering

Department dc:contributor.department

Electrical and Computer Engineering

Grantor dc:publisher

Virginia Tech

Year dc:date.issued

2017

Author dc:creator

• Yeh, Chih-Shen

Chair dc:contributor.committeechair

• Lai, Jih-Sheng

Committee members dc:contributor.committeemember

• Koh, Kwang-Jin
• Li, Qiang

• coupled inductor
• zero-voltage switching
• non-isolated dc-dc converter
• high step-down
• high switching frequency
• low-power application

Statement dc:rights

• Creative Commons Attribution-ShareAlike 3.0 United States

Licence dc:rights.uri

• http://creativecommons.org/licenses/by-nc-sa/3.0/us/

Language dc:language.iso

en_US

Handle dc:identifier.uri

http://hdl.handle.net/10919/81722

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/81722