PWM and PFM Hybrid Control Method for LLC Resonant Converters in High Switching Frequency Operation

High switching frequency is an effective method to improve power density for LLC resonant converters. However, conventional digital controllers, such as general-purpose digital signal processors and microprocessors, have limited frequency resolution, which induces high primary- and secondary-side cu...

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Bibliographic Details
Published inIEEE transactions on industrial electronics (1982) Vol. 64; no. 1; pp. 253 - 263
Main Authors Park, Hwa-Pyeong, Jung, Jee-Hoon
Format Journal Article
LanguageEnglish
Published New York IEEE 01.01.2017
The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Subjects
<italic xmlns:ali="http://www.niso.org/schemas/ali/1.0/" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">LLC resonant converter
Control methods
Control systems
Converters
Digital signal processing
Electric potential
Frequency control
High-frequency operation
Hybrid control
Inductance
Microprocessors
MOSFETs
Pulse duration modulation
Pulse frequency modulation
pulse frequency modulation (PFM)
Pulse width modulation
pulse width modulation (PWM)
Resonant frequency
Signal processing
Switching
Switching frequency
Voltage
Voltage control
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Summary:High switching frequency is an effective method to improve power density for LLC resonant converters. However, conventional digital controllers, such as general-purpose digital signal processors and microprocessors, have limited frequency resolution, which induces high primary- and secondary-side current variation and leads to poor output voltage regulation. In this paper, a hybrid control method combining pulse frequency modulation (PFM) and pulse width modulation is proposed to overcome the limited frequency resolution issue. The proposed hybrid control method focuses on steady-state operation, and its operating principles are introduced and analyzed. In addition, the proper magnetizing inductance and dead time duration are derived to ensure that the power mosfets achieve zero voltage switching with the proposed control method. The improved voltage regulation performance is compared with the conventional PFM control and verified through simulation and experimental results using a 240 W prototype converter operating at a switching frequency of 1 MHz.
ISSN:0278-0046
1557-9948
DOI:10.1109/TIE.2016.2599138