摘要:
LLC谐振变换器已经在开关电源领域得到了广泛应用,但现有的关于变换器软开关实现条件及死区时间设计的研究还存在明显不足.为此, 本文以\,LLC\,谐振变换器软开关工作特性为研究对象,建立了死区时间内变换器的精确等效模型,并在此基础上提出了变换器的软开关边界理论.该理论根据死区时间内电荷供给量与需求量的平衡关系,以及死区时间与谐振电流回零时间的大小关系,将变换器工作区域分为一个软开关工作区域和三个非软开关工作区域,并归纳得到了软开关边界曲线.分析了变换器在最差工况下也能实现软开关的最小死区,并推导得到了最小死区的数学表达式. 最后,结合一款\,300~W\,的样机进行了实例验证,理论设计与实验结果的吻合验证了理论分析的准确性.
Abstract:
LLC resonant converter is widely used in switched mode power supplies. However, the present research on conditions of realizing soft switching and the design of dead time has obvious shortcomings. Therefore, the soft switching of LLC resonant converter is studied, and the soft switching boundary theory is
proposed based on the precise equivalent model during the dead-time interval. According to the balance between the supplying charge during the dead-time and the required charge, together with the length relationship between the dead-time and the zero-crossing time of resonant current, the operation region of the converter can be divided into one soft switching operation region and three hard switching operation region, and the boundary curve of soft switching
is concluded. The minimum dead-time for realizing soft switching even under the worst case is analyzed, and the mathematical equation of the minimum dead-time is derived. Finally, a 300 W prototype is build, and the accuracy of the theory is verified by the accordance between the theoretical design and the experimental results.
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