Two-Order Fitting Model-Based Digital Synchronous Rectifier Control for SiC Bidirectional LLC Converter
Li Haoran1, Cui Chaohui1, Wang Shengdong2, Zhang Zhiliang3, Hu Cungang1
1. School of Electrical Engineering and Automation Anhui University Hefei 230039 China; 2. The 55th Research Institute of CETC Nanjing 210016 China; 3. College of Automation Engineering Nanjing University of Aeronautics and Astronautics Nanjing 211106 China
Abstract Conventional LLC synchronous rectifier (SR) typically senses high-frequency signals, easily affected by high dv/dt resulting in duty cycle loss and high conduction loss. The SR method with a given duty cycle cannot track load variations and causes high conduction loss in a wide load range. A two-order fitting model-based digital synchronous rectifier control is proposed for the bidirectional SiC LLC converter, which tracks load variations and switching frequency to calculate the SR on-time online. The turn-on instants between the primary and secondary switching devices are identical, while the calculated SR on-time determines the SR turn-off instants. The proposed control achieves low conduction loss and has high immunity to high switching noise without sensing high-frequency signals. When the resonant inductor and output load have 10% tolerances, the maximum tolerance for the SR on-time is only 2.73%. A prototype of a 6.6kW SiC bidirectional LLC charger was built. Compared with the conventional LLC SR control, the efficiency improvement is up to 0.36% at 6.6kW in the forward mode, and 0.29% at 3.3kW in the reverse mode.
Li Haoran,Cui Chaohui,Wang Shengdong等. Two-Order Fitting Model-Based Digital Synchronous Rectifier Control for SiC Bidirectional LLC Converter[J]. Transactions of China Electrotechnical Society, 2022, 37(24): 6191-6203.
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2022, Vol. 37 
