Implementation and Study of Constant-Frequency LLC Resonant Converter

  • Shi-Yi Lin
  • Shih-Kuen Changchien
  • Chien-Ming Hong
  • Yi-Nung Chung
Conference paper
Part of the Lecture Notes in Electrical Engineering book series (LNEE, volume 234)


This chapter presents an LLC resonant converter with constant frequency. Since LLC resonant converters possess the advantages of high efficiency and low electromagnetic interference, they are widely used in many applications. However, the EMI filter design becomes more complex because of the variable-frequency operation of LLC resonant converter. Therefore, in this chapter, a circuit configuration of a buck converter cascade an LLC resonant converter, buck-fed LLC resonant converter, is proposed to complete constant-frequency operation and simplify the EMI filter design. The buck converter is applied in the proposed converter as the input source for the LLC resonant converter. In addition, by adjusting the output voltage of the buck converter, the output regulation and constant-frequency operation of the proposed converter can be achieved. Finally, a prototype of the buck-fed LLC resonant converter with input voltage 380–400 V and output 24 V/10 A is implemented. The experimental results demonstrate the feasibility of the proposed converter.


Constant frequency EMI filter LLC resonant converter Cascade Buck-fed LLC resonant converter 


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Copyright information

© Springer Science+Business Media New York 2013

Authors and Affiliations

  • Shi-Yi Lin
    • 1
  • Shih-Kuen Changchien
    • 2
  • Chien-Ming Hong
    • 3
  • Yi-Nung Chung
    • 1
  1. 1.Department of Electrical EngineeringNational Changhua University of EducationChanghuaTaiwan
  2. 2.Department of Automation Engineering and Institute of Mechatronoptic SystemsChienkuo Technology UniversityChanghuaTaiwan
  3. 3.Department of Electrical EngineeringChienkuo Technology UniversityChanghuaTaiwan

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