Abstract：This paper proposes a fixed-frequency LLC resonant converter adjusted by auxiliary half-bridge. The LLC half-bridge and the auxiliary half-bridge both perform isolated power conversion. The equivalent resonant parameters of half-bridge LLC are changed only by adjusting the timing of control signal without adding extra components so that the regulation of output voltage can be implemented. Compared with the traditional frequency modulation, fixed-frequency control can facilitate the optimization of magnetic components. The magnetizing inductance has less impact on the gain characteristics, and the efficiency at light load is improved. In addition, the auxiliary half-bridge only deals with a small part of the power, and the whole circuit retains the characteristics of the original LLC converter. The operation principle and steady state analysis are discussed in this paper. Finally, a prototype sample with 300 V input and 48 V/4 A output is built, and the feasibility of the proposed converter is verified by experimental results.
[1] Kundu U, Yenduri K, Sensarma P.Accurate ZVS analysis for magnetic design and efficiency improvement of full-bridge LLC resonant converter[J]. IEEE Transactions on Power Electronics, 2017, 32(3): 1703-1706. [2] 胡海兵, 王万宝, 孙文进, 等. LLC谐振变换器效率优化设计[J]. 中国电机工程学报, 2013, 33(18): 48-56. Hu Haibing, Wang Wanbao, Sun Wenjin, et al.Optimal efficiency design of LLC resonant converters[J]. Proceedings of the CSEE, 2013, 33(18): 48-56. [3] Beiranvand R, Rashidian B, Zolghadri M R, et al.A design procedure for optimizing the LLC resonant converter as a wide output range voltage source[J]. IEEE Transactions on Power Electronics, 2012, 27(8): 3749-3763. [4] Musavi F, Craciun M, Gautam D S, et al.Control strategies for wide output voltage range LLC resonant DC-DC converters in battery chargers[J]. IEEE Transactions on Vehicular Technology, 2014, 63(3): 1117-1125. [5] 辛德锋, 安昱, 郜亚秋, 等. 适用于ISOS拓扑的高压DC/DC变换器研究[J]. 电力系统保护与控制, 2017, 45(13): 64-70. Xin Defeng, An Yu, Gao Yaqiu, et al.Study on high voltage DC/DC converter based on ISOS topology[J]. Power System Protection and Control, 2017, 45(13): 64-70. [6] 张涛, 朱小平. 基于LLC变换器的电动汽车充电机设计[J]. 电气技术, 2016, 17(6): 97-100. Zhang Tao, Zhu Xiaoping.The design of EV charger based on LLC converter[J]. Electrical Engineering, 2016, 17(6): 97-100. [7] Wu Hongfei, Zhan Xiaohai, Xing Yan.Interleaved LLC resonant converter with hybrid rectifier and variable-frequency plus phase-shift control for wide output voltage range applications[J]. IEEE Transactions on Power Electronics, 2016, 32(6): 4246-4257. [8] 李浩昱, 李振伟, 赵雷, 等. 宽输入LLC谐振变换器多电平控制策略[J]. 电工技术学报, 2017, 32(4): 48-57. Li Haoyu, Li Zhenwei, Zhao Lei, et al.Multi-level control strategy of wide input LLC resonant converter[J]. Transactions of China Electrotechnical Society, 2017, 32(4): 48-57. [9] 刘和平, 陈红岩, 苗轶如, 等. 混合式LLC电路谐振与同步整流数字式控制[J]. 中国电机工程学报, 2015, 35(9): 2272-2278. Liu Heping, Chen Hongyan, Miao Yiru, et al.Hybrid LLC circuit resonant and synchronous rectifier digital control[J]. Proceedings of the CSEE, 2015, 35(9): 2272-2278. [10] Lee J S, Choi J W, Baek J I, et al.Three-switch LLC resonant converter for high efficiency adapter with universal input voltage[C]//Future Energy Electronics Conference and ECCE Asia, Kaohsiung, Taiwan, 2017: 1095-1100. [11] Wang Hongliang, Chen Yang, Fang Peng, et al.An LLC converter family with auxiliary switch for hold-up mode operation[J]. IEEE Transactions on Power Electronics, 2017, 32(6): 4291-4306. [12] 王暄, 王广柱, 孙晓伟, 等. 具有宽范围输出电压的三电平半桥LLC谐振变换器控制策略[J]. 电工技术学报, 2017, 32(21): 24-33. Wang Xuan, Wang Guangzhu, Sun Xiaowei, et al.Research on control strategy of three-level half-bridge LLC resonant converter with wide output voltage range[J]. Transactions of China Electrotechnical Society, 2017, 32(21): 24-33. [13] 吕正, 颜湘武, 孙磊. 基于变频-移相混合控制的L-LLC谐振双向DC-DC变换器[J]. 电工技术学报, 2017, 32(4): 12-24. Lü Zheng, Yan Xiangwu, Sun Lei.A L-LLC resonant bidirectional DC-DC converter based on hybrid control of variable frequency and phase shift[J]. Transactions of China Electrotechnical Society, 2017, 32(4): 12-24. [14] Jeong Y, Moon G W, Kim J K.Analysis on half-bridge LLC resonant converter by using variable inductance for high efficiency and power density server power supply[C]//Applied Power Electronics Conference and Exposition, Tampa, FL, 2017: 170-177. [15] Chen Yang, Wang Hongliang, Hu Zhiyuan, et al.LCLC resonant converter for hold up mode operation[C]//Energy Conversion Congress and Exposition, Montreal, QC, Canada, 2015: 556-562. [16] Kim D K, Moon S C, Yeon C O, et al.High-efficiency LLC resonant converter with high voltage gain using an auxiliary LC resonant circuit[J]. IEEE Transactions on Power Electronics, 2016, 31(10): 6901-6909. [17] Jeong Y, Kim J K, Lee J B, et al.An asymmetric half-bridge resonant converter having a reduced conduction loss for DC/DC power applications with a wide range of low input voltage[J]. IEEE Transactions on Power Electronics, 2017, 32(10): 7795-7804. [18] 管乐诗, 王懿杰, 王卫, 等. 基于临界模式Boost电路与LLC谐振电路的单级交直变换器[J]. 电工技术学报, 2016, 31(11): 41-50. Guan Yueshi, Wang Yijie, Wang Wei, et al.A single-stage AC-DC converter based on boundary conduction mode boost circuit and LLC resonant converter[J]. Transactions of China Electrotechnical Society, 2016, 31(11): 41-50. [19] Sun Xiaofeng, Shen Yanfeng, Zhu Yune, et al.Interleaved boost-integrated LLC resonant converter with fixed-frequency PWM control for renewable energy generation applications[J]. IEEE Transactions on Power Electronics, 2015, 30(8): 4312-4326. [20] 孙孝峰, 申彦峰, 李午英, 等. 交错并联双向Buck/ Boost集成LLC谐振型三端口直流变换器[J]. 电工技术学报, 2016, 31(14): 165-175. Sun Xiaofeng, Shen Yanfeng, Li Wuying, et al.Interleaved bidirectional Buck/Boost and LLC integrated three-Port DC Converter[J]. Transactions of China Electrotechnical Society, 2016, 31(14): 165-175. [21] Kim J W, Moon G W.A new LLC series resonant converter with a narrow switching frequency variation and reduced conduction losses[J]. IEEE Transactions on Power Electronics, 2014, 29(8): 4278-4287. [22] Wu Hongfei, Mu Tiantian, Gao Xun, et al.A secondary-side phase-shift-controlled LLC resonant converter with reduced conduction loss at normal operation for hold-up time compensation application[J]. IEEE Transactions on Power Electronics, 2015, 30(10): 5352-5357. [23] Shang Ming, Wang Haoyu.A LLC type resonant converter based on pwm voltage quadrupler rectifier with wide output voltage[C]//Applied Power Electronics Conference and Exposition, Tampa, FL, 2017: 1720-1726. [24] Li Zhiqing, Wang Haoyu.Design of a secondary side regulated LLC based integrated PEV onboard charger with full ZVS range[C]//Applied Power Electronics Conference and Exposition, Tampa, FL, 2017: 1394-1400. [25] Shakib S I, Mekhilef. A frequency adaptive phase shift modulation control based LLC series resonant converter for wide input voltage applications[J]. IEEE Transactions on Power Electronics, 2017, 32(11): 8360-8370. [26] Qian Ting.An adaptive current injection scheme for resonant capacitor of LLC resonant converters with suppressed frequency variation[J]. IEEE Transactions on Power Electronics, 2016, 31(12): 8074-8080. [27] Ahmed M, Fei C, Lee F C, et al.High-efficiency high-power-density 48/1V sigma converter voltage regulator module[C]//Applied Power Electronics Conference and Exposition, Tampa, FL, 2017: 2207-2212. [28] Sun Xiaofeng, Li Xiaohua, Shen Yanfeng, et al.Dual-bridge LLC resonant converter with fixed-frequency PWM control for wide input applications[J]. IEEE Transactions on Power Electronics, 2017, 32(1): 69-80.
2019, Vol. 34 
