摘要
为了解决变频控制的桥臂共用型四开关Buck-BoostLLC级联变换器磁性元件设计和优化困难的问题,提出一种二次侧为特殊全桥整流结构的级联式四开关Buck-Boost LLC变换器。通过控制二次侧开关管的交叠导通时间以拓宽变换器的电压增益。该变换器可根据不同的输入电压范围工作在交叠模式和整流模式;在不改变变换器参数的条件下将增益显著提高,能够适应更宽范围的输入电压,同时保持了变换器较高的工作效率。在两种工作模式的基础上,采用移相控制使变换器所有开关管实现零电压导通(ZVS),二极管实现零电流关断(ZCS)。结合状态平面轨迹分析法,对定频控制的级联式四开关Buck-Boost LLC变换器进行模态分析,并推导两种工作模式下的输入-输出表达式和开关管的软开关实现条件。最后,通过研制一台70~280 V输入、240 W/28 V输出的实验样机,验证了理论分析的正确性。
In new energy resource and electric vehicle fields,DC-DC converters are required to have more advantages,such as wide gain range,isolation,and high efficiency.Therefore,a cascaded four-switch Buck-Boost LLC converter with power switch integration is selected by discussing the advantages and disadvantages of various DC-DC converters.The cascaded converter has a four-switch Buck-Boost converter in the pre-stage and a half-bridge LLC resonant converter in the post-stage.Since designing and optimizing the magnetic components of the cascaded converter controlled by variable frequency is difficult,a special full bridge rectifier structure on the transformer’s secondary side is proposed.The cascaded converter with a special full bridge rectifier structure can widen the input voltage range under fixed frequency control and realize the wide gain range,isolation,high efficiency,and parameter optimization.The low-side switching devices of the special full bridge rectifier structure on the transformer’s secondary side are switches.The simultaneous on-time of the low-side switches is called the overlapping turn-on time.The gain of the cascaded converter can be improved by controlling the overlapping turn-on time.Therefore,the gain range can be widened,and the efficiency is optimized under fixed frequency control.The gain of the converter that the parameters are unchanged is increased significantly so that the cascaded converter could be adapted to a wider input voltage range and maintain higher efficiency simultaneously.When the input voltage is less than or equal to the threshold input voltage,the cascaded converter adjusts the overlapping turn-on time to stabilize the output voltage.This mode is called overlapping mode.When the input voltage exceeds the threshold input voltage,the overlapping turn-on time is zero,and the cascaded converter performs pulse width modulation on the input leg on the primary side to stabilize the output voltage.This mode is called rectification mode.Based on the two modes,the phase shift cont
作者
周国华
邱森林
张小兵
Zhou Guohua;Qiu Senlin;Zhang Xiaobing(School of Electrical Engineering Southwest Jiaotong University,Chengdu 611756 China)
出处
《电工技术学报》
EI
CSCD
北大核心
2024年第4期1103-1115,共13页
Transactions of China Electrotechnical Society
基金
国家自然科学基金资助项目(62271417,61771405)。
