Three-Phase LLC Series Resonant DC/DC Converter Using SiC MOSFETs to Realize High-Voltage and High-Frequency Operation

• Published in: IEEE transactions on industrial electronics (1982) 2016-04, Vol.63 (4), p.2103-2110
• Main Authors: Nakakohara, Yusuke, Otake, Hirotaka, Evans, Tristan M., Yoshida, Tomohiko, Tsuruya, Mamoru, Nakahara, Ken
• Format: Article
• Language: English
• Subjects: Circuit faults; current balancing transformers; LLC resonant converter; MOSFET; Power conversion; SiC MOSFETs; Silicon; Silicon carbide; Switches; three phase; zero current switching (ZCS); Zero voltage switching; zero voltage switching (ZVS)
• ISSN: 0278-0046; 1557-9948
• DOI: 10.1109/TIE.2015.2499721

SiC MOSFETs are applied to constitute a three-phase, 5-kW LLC series resonant dc/dc converter with isolation transformers. A switching frequency of around 200 kHz for the transistors successfully reduces the volume of these isolation transformers, whereas insulated-gate bipolar transistors (IGBTs) are not capable of achieving such a high switching speed. The high-voltage tolerance of SiC MOSFETs, 1200 V, enables increasing the input voltage up to 600 V. High-voltage tolerance, on the other hand, is not compatible with low on-resistance for Si MOSFETs. A three-phase circuit topology is used to achieve up to 5 kW of power capacity for the converter and reduce per-phase current at the same time. Current-balancing transformers among these three phases effectively suppress a maximum peak current from arising in the circuit, a technique that miniaturizes the input and output capacitances. The conversion efficiency of the converter reaches 97.6% at 5-kW operation.