Design Optimizations of LLC Resonant Converters with Planar Matrix Transformers

LLC resonant converters have been a popular choice for DC-DC converters due to their high efficiency, high power density, and hold-up capability in power supplies for communication systems, datacenters, consumer electronics, and automobiles. With the rapid development of wide-bandgap devices and novel magnetic materials, the push for higher switching frequencies to achieve higher power densities at lower costs is gaining traction. To demonstrate high efficiency and high power density, the Center for Power Electronics Systems (CPES) at Virginia Tech designed an 800W, 1MHz 400V/12V LLC converter for future datacenters, which could achieve a peak efficiency of 97.6% and a power density of 900 W/in3. However, with the ever-increasing demand for online services, the performance of power delivery must also be simultaneously improved to keep pace with the demand. The focus of this thesis is improving the performance of CPES’ previous 400V/12V LLC converter by investigating different aspects of its design and operation. Ultimately, design guidelines are proposed, and improvements are demonstrated to effectively achieve higher efficiency and higher power density than the previous CPES converter. Multiple aspects of the LLC converter’s design and structure are investigated to further improve its performance, and three main areas are the focus of this thesis. The output-side termination design of the planar transformer is investigated and modeled, and design guidelines for filter capacitor selection are provided for optimal efficiency. Next, the existing shielding technique for matrix transformers, which helps reduce common-mode (CM) noise without compromising on efficiency, is investigated for asymmetry and current-sharing issues, and modifications have been proposed to improve its efficiency. Thirdly, the LLC converter’s switching frequency is optimized to improve its performance over the previous CPES converter. Finally, the hardware results with the proposed improvements are demonstrated, and the converter’s performance is compared with the previous CPES converter as well as other recent proposed solutions.

Name thesis:degree_name

M.S.

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

2021

Author dc:creator

• Prakash, Pranav Raj

Chair dc:contributor.committeechair

• Li, Qiang

Committee members dc:contributor.committeemember

• Dong, Dong
• Southward, Steve C.

• LLC resonant converter
• Termination
• Planar Matrix Transformer
• Shielding

Statement dc:rights

• Creative Commons Attribution 4.0 International

Licence dc:rights.uri

• http://creativecommons.org/licenses/by/4.0/

Language dc:language.iso

en

Handle dc:identifier.uri

http://hdl.handle.net/10919/108057

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/108057