Abstract：The short circuit problem is a difficult issue in research on LLC converter. This paper derives the trajectory of the full-bridge LLC converter based on state-plane analysis and the characte- ristics of the trajectory performance is provided in short circuit mode. Two types of control strategy for power switches, respectively based on phase-shift frequency-boost or frequency-drop scheme, are deduced for full-bridge LLC converter under short circuit mode. By designing the trajectory of the state variables, two schemes achieve controllable short current output while maintain the advantage of ZVS. Comparing with traditional solution directly increasing switching frequency, the concept presented in this paper brings better short current limitation performance.
[1] L Bing, L Wenduo, L Yan, et al. Optimal design methodology for LLC resonant converter[C]. IEEE Applied Power Electronics Conference and Exposi- tion, 2006. [2] Yang B, Lee F C, Concannon M. Over current protec- tion methods for LLC resonant converter[C]. Applied Power Electronics Conference and Exposition, 2003: 605-609. [3] Bo Y. Topology investigation for front end DC/DC power conversion for distributed power system[D]. Blacksburg: Virginia Polytechnic Institute and State University, 2003. [4] X Xiaogao, Z Junming, Z Chen, et al. Analysis and optimization of LLC resonant converter with a novel over-current protection circuit[J]. IEEE Transactions on, Power Electronics, 2007, 22(2): 435-443. [5] F Dianbo, Lee F C, L Ya, et al. Novel multi-element resonant converters for front-end DC-DC converters [C]. IEEE Power Electronics Specialists Conference, 2008: 250-256. [6] H Daocheng, Lee F C, F Dianbo. Classification and selection methodology for multi-element resonant con- verters[C]. IEEE Applied Power Electronics Conference and Exposition (APEC), 2011: 558-565. [7] Weiyi F, Lee F C, Mattavelli P. Simplified optimal trajectory control (SOTC) for LLC resonant conver- ters[J]. IEEE Transactions on Power Electronics, 2013, 28(5): 2415-2426. [8] F Weiyi, Lee F C. Optimal trajectory control of LLC resonant converters for soft start-up[C]. IEEE Applied Power Electronics Conference and Exposition(APEC), 2013: 1445-1451. [9] F Weiyi. State trajectory analysis and control of LLC resonant converters[D]. Blacksburg: Virginia Polyte- chnic Institute and State University, 2013. [10] F Weiyi, P Mattavelli, Lee F C, et al. LLC converters with automatic resonant frequency tracking based on synchronous rectifier(SR) gate driving signals[C]. IEEE Applied Power Electronics Conference and Exposi- tion(APEC), 2011: 1-5.
2015, Vol. 30 
