基于SEPIC电路的单级LLC谐振变换器研究

发布时间：2019-03-19 17:21

【摘要】：LED作为新一代绿色光源,具有光效高、寿命长、响应快等优点,已经广泛应用于路灯照明、汽车照明等领域。传统的LED驱动为两级式结构,两级结构具有较高的PF和较低的THD值,但是存在器件多、体积大、控制较为复杂、成本较高等缺点。单级交直流变换器因其高可靠性、高功率密度而成为研究热点。但是目前的单级结构大多工作在硬开关状态,系统开关损耗较高,无法应用在大功率LED驱动系统中。本文在拓扑集成约束条件下,通过集成Sepic电路的开关器件和LLC半桥谐振电路的开关器件,提出一种新型单级交直流变换器结构。由于集成了两级的开关器件,系统所用的器件较少,降低了系统成本并提高了系统可靠性。同时由于LLC谐振电路在系统集成后,仍具有软开关特性,系统开关损耗较低,母线电压较低,适合应用在大功率LED驱动系统中。本文首先根据SSC集成理论实现了两级变换器到单级变换器的集成变换,对单级结构进行了模态分析,得出了单周期的典型波形。并以母线电压为中间变量,对所提变换器的Sepic单元和LLC单元进行了深入分析,给出了分析过程。其次对所提系统进行了优化设计,包括前后单元典型器件的参数计算与设计,对辅助电源、驱动电路、采样电路的设计等。接下来通过扩展描述函数方法,建立了LLC谐振电路的数学模型,提出了优化的补偿方式,并根据双线性变换法提出系统的数字化控制策略。最后,在理论研究与分析的基础上,对系统进行仿真,并绘制原理图,搭建实验平台,进行实验验证。实验结果表明,所提单级结构能够可靠实现功率因数校正功能,同时系统工作在软开关状态下,稳态时效率高达92%。
[Abstract]:As a new generation of green light source, LED has many advantages, such as high light efficiency, long life and fast response. It has been widely used in street lamp lighting, automobile lighting and other fields. The traditional LED driver is a two-stage structure. The two-stage structure has the disadvantages of high PF and low THD value, but there are many devices, large volume, complicated control and high cost. Single-stage AC-DC converter has become a research hotspot because of its high reliability and high power density. However, most of the current single-stage structures work in the hard-switching state, the switching loss of the system is high, and can not be used in the high-power LED drive system. In this paper, a novel single-stage AC-DC converter is proposed by integrating the switching device of Sepic circuit and the switch device of LLC half-bridge resonant circuit under the constraint of topology integration. As a result of the integration of two-stage switching devices, the system uses fewer devices, reducing the system cost and improving the reliability of the system. At the same time, the LLC resonant circuit still has the soft-switching characteristic after the system is integrated, the system switching loss is lower, the bus voltage is lower, so it is suitable for the high-power LED drive system. In this paper, the integration transformation from two-stage converter to single-stage converter is realized according to SSC integration theory. The modal analysis of single-stage converter is carried out, and the typical waveform of single-stage converter is obtained. Taking the bus voltage as the intermediate variable, the Sepic unit and the LLC unit of the proposed converter are deeply analyzed, and the analysis process is given. Secondly, the proposed system is optimized, including the calculation and design of the parameters of the typical devices in front and back units, the design of auxiliary power supply, driving circuit, sampling circuit and so on. Then, the mathematical model of LLC resonant circuit is established by extending the description function method, and the optimized compensation method is proposed, and the digital control strategy of the system is put forward according to bilinear transformation method. Finally, on the basis of theoretical research and analysis, the system is simulated, and the schematic diagram is drawn, the experimental platform is set up, and the experimental verification is carried out. The experimental results show that the proposed single-stage structure can achieve the power factor correction function reliably. At the same time, the system works in the soft-switching state, and the steady-state efficiency is as high as 92%.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TM46

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