Flux-Balance Control for LLC Resonant Converters with Center-Tapped Transformers

Yuan-Chih Lin, Ding-Tang Chen and Ching-Jan Chen
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Yuan-Chih Lin: Department of Electrical Engineering, National Taiwan University, Taipei, Taiwan; No. 1, Sec. 4, Roosevelt Rd., Taipei 10617, Taiwan
Ding-Tang Chen: Department of Electrical Engineering, National Taiwan University, Taipei, Taiwan; No. 1, Sec. 4, Roosevelt Rd., Taipei 10617, Taiwan
Ching-Jan Chen: Department of Electrical Engineering, National Taiwan University, Taipei, Taiwan; No. 1, Sec. 4, Roosevelt Rd., Taipei 10617, Taiwan

Energies, 2019, vol. 12, issue 17, 1-18

Abstract: LLC resonant converters with center-tapped transformers are widely used. However, these converters suffer from a flux walking issue, which causes a larger output ripple and possible transformer saturation. In this paper, a flux-balance control strategy is proposed for resolving the flux walking issue. First, the DC magnetizing current generated due to the mismatched secondary-side leakage inductances, and its effects on the voltage gain are analyzed. From the analysis, the flux-balance control strategy, which is based on the original output-voltage control loop, is proposed. Since the DC magnetizing current is not easily measured, a current sensing strategy with a current estimator is proposed, which only requires one current sensor and is easy to estimate the DC magnetizing current. Finally, a simulation scheme and a hardware prototype with rated output power 200 W, input voltage 380 V, and output voltage 20 V is constructed for verification. The simulation and experimental results show that the proposed control strategy effectively reduces the DC magnetizing current and output voltage ripple at mismatched condition.

Keywords: LLC resonant converter; center-tapped transformer; flux walking; flux-balance control loop; magnetizing current estimation (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2019
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (1)

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