| Title |
Three-Phase LLC Resonant Converter and Its Control Method |
| Authors |
Ju-Seon Park ; Min-Gyeong Kang ; Min-Su Kang ; Jae-Taek Lee ; Jae-Hyeon Sin ; Eun-Soo Kim |
| DOI |
https://doi.org/10.6113/TKPE.2026.31.4.336 |
| ISSN |
1229-2214(pISSN), 2288-6281(eISSN) |
| Keywords |
Three-Phase LLC Converter; Secondary-Side Resonant Inductor; Phase Modulation Control; Wide Voltage Gain; EV Fast Charger |
| Abstract |
This paper presents an improved three-phase LLC resonant DC?DC converter for high-power electric vehicle fast-charging systems requiring wide output voltage regulation and high efficiency. Conventional three-phase LLC converters predominantly rely on frequency modulation, which limits voltage gain extension and often requires burst-mode operation or relay-based transformer tap switching at low output voltages, thereby increasing voltage ripple, reducing reliability, and complicating system design. To address these challenges, the proposed converter relocates the resonant inductor to the secondary side, significantly enhancing the voltage gain range even with a reduced transformer turns ratio. Moreover, phase modulation operated at the maximum switching frequency enables continuous low-voltage regulation without burst-mode operation, effectively eliminating additional hardware or discontinuous control schemes. By systematically integrating frequency, input voltage, and phase modulation, the proposed control strategy achieves seamless and wide-range gain control while maintaining high efficiency. The feasibility and effectiveness of the proposed topology and control method are experimentally validated using a 20 kW prototype, which demonstrates high efficiency and stable operation across a wide output voltage range. |