基于准谐振双Buck电路的高频LED驱动技术

发布时间：2018-04-05 12:01

本文选题：高频　切入点：双Buck电路　出处：《哈尔滨工业大学》2017年硕士论文

【摘要】：传统的LED驱动电路为两级式结构,前级为功率因数校正电路,后级为直流变换电路,其主要优点在于能够对每一级电路进行单独设计,设计过程更为简单,控制也更为精确。为进一步提高效率及功率密度,本文提出一种适用于工作在较高频率的基于准谐振双Buck电路的LED驱动系统,准谐振双Buck电路开关器件工作在软开关状态,系统具有较高的效率和功率密度。主要研究内容包括:本文分析了双Buck电路的工作原理,得到了其工作在准谐振状态的条件约束,提出了优化的参数设计方法。为进一步降低系统通态损耗并提高开关频率,本文采用了Ga N system公司的Ga N器件,针对所选器件,提出优化的驱动电路设计方法。同时针对平面磁性元件中的绕组损耗,寄生电容和漏感等参数难于预测的问题,本文分析了磁性元件的结构、磁性元件的匝数和层数、绕组厚度和宽度等对上述寄生参数的影响,提出了平面磁性元件的精确设计方法,并结合Maxwell仿真软件,采用有限元仿真验证了其准确性。本文提出了准谐振双Buck电路优化的数字化控制方法。开关管的开通和关断时刻分别由零电压检测环节和峰值电流检测环节确定,实现了开关器件的自适应零电压开通,同时有效控制了开关器件的峰值电流,提高了系统的稳定性。同时,本文提出通过采样输入平均电流的方法来对输出电流进行精确调节,实现了LED驱动系统的闭环控制。由于状态空间平均法忽略了电路中寄生参数,具有一定的局限性,因此本文采用电路平均法,对工作在断续模式下的非理想Buck电路进行建模,建立了其小信号模型,得到了系统开环传递函数,并采用滞后环节对系统进行了补偿,同时根据相应的差分算法,提出了优化的数字补偿策略,提高了系统的鲁棒性。最后设计并搭建了一台满载60W、工作频率500k Hz的样机进行实验验证,实验测得额定功率时系统功率因数大于0.98,THD小于5%,效率达到92.9%,验证了理论分析的正确性。
[Abstract]:The traditional LED drive circuit is a two-stage structure, the former stage is a power factor correction circuit, and the latter stage is a DC converter circuit. Its main advantage is that it can be designed separately for each stage of the circuit, and the design process is simpler and the control is more accurate.In order to further improve efficiency and power density, this paper presents a kind of LED drive system based on quasi resonant double Buck circuit, which works at high frequency. The switching device of quasi resonant double Buck circuit works in soft switching state.The system has high efficiency and power density.The main research contents are as follows: this paper analyzes the working principle of double Buck circuit, obtains the condition constraint of its working in quasi-resonant state, and puts forward an optimized parameter design method.In order to further reduce the on-state loss of the system and increase the switching frequency, the gan device of gan system Company is used in this paper. For the selected device, an optimized driving circuit design method is proposed.At the same time, the structure of magnetic element, the number of turns and layers of magnetic element are analyzed in order to solve the problem that the winding loss, parasitic capacitance and leakage inductance are difficult to predict in plane magnetic element.The influence of winding thickness and width on the parasitic parameters is discussed. A precise design method of planar magnetic element is proposed. The accuracy of the method is verified by finite element simulation with Maxwell simulation software.In this paper, a digital control method for quasi resonant double Buck circuit optimization is proposed.The switch on and off time are determined by the zero voltage detection link and the peak current detection link respectively. The adaptive zero voltage switching on of the switch device is realized, and the peak current of the switch device is effectively controlled, and the stability of the system is improved.At the same time, the method of sampling the average input current is proposed to adjust the output current accurately, and the closed-loop control of the LED drive system is realized.Because the state space averaging method neglects the parasitic parameters of the circuit and has some limitations, this paper uses the circuit averaging method to model the non-ideal Buck circuit working in intermittent mode, and establishes its small signal model.The open loop transfer function of the system is obtained, and the delay link is used to compensate the system. At the same time, according to the corresponding difference algorithm, an optimized digital compensation strategy is proposed to improve the robustness of the system.Finally, a prototype with full load of 60W and working frequency of 500kHz is designed and built for experimental verification. When the rated power is measured, the power factor of the system is greater than 0.98m THD less than 5, and the efficiency reaches 92.90.The correctness of the theoretical analysis is verified.
【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】：2017
【分类号】：TM46

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