小功率开关电源设计毕设论文.doc

摘要 ABSTRCT With the development of power electronics technology, switching power supply is gradually replaced by a linear power supply, known as the mainstream form of todays power supply, and is widely used in electricity, electronics and other fields. This paper is a switching power supply integrated the control chip M51995AFP design a step-down switching power supply, the output voltage of 5VDC. This switching power supply is on duty through pulse width modulation control to adjust the output voltage to achieve a stable output purposes. The thesis, completed the following: (1)Need to select the switching power supply topology; (2)Based on the design of switching power supply control core M51995AFP part; (3)Design rectifier filter circuit reduces the output ripple; (4)The establishment of the switching power supply circuit model and analysis; (5)Select the model and simulation analysis to determine the system parameters. This thesis is based on the works of the various components within the control chip design reasonable auxiliary circuit, calculation and simulation analysis, system tuning parameters. Mastered the core technology of the switching power supply design, and the design process elaborate. Keywords: Switching Power Supply, Duty Cycle, Pulse Width Modulation 目录 1.绪论 - 1 - 1.1开关电源的概念和分类 - 1 - 1.1.1开关电源的概念 - 1 - 1.1.2开关电源的分类 - 3 - 1.2开关电源的发展趋势 - 3 - 2.开关电源的设计基础 - 4 - 2.1开关电源中的电力电子电路 - 4 - 2.1.1非隔离型电路 - 4 - 2.1.2隔离型电路 - 7 - 2.2软开关技术 - 9 - 2.2.1软开关的基本概念 - 9 - 2.2.2零电压开关和零电流开关 - 11 - 2.2.3常见软开关电路 - 11 - 2.3谐振式电源 - 18 - 2.3.1谐振变换电路的原理及分类 - 18 - 2.3.2谐振式电源原理 - 19 - 2.3.3谐振开关的动态过程分析 - 20 - 3.开关电源元器件的选用 - 24 - 3.1二极管 - 25 - 3.1.1开关二极管 - 25 - 3.1.2稳压二极管 - 25 - 3.1.3快速恢复及超快速恢复二极管 - 26 - 3.2开关晶体管 - 26 - 3.2.1功率开关MOSFET - 26 - 3.2.2绝缘栅双极型晶体管 - 28 - 3.3自动恢复开关 - 28 - 3.4热敏电阻 - 29 - 3.5光电耦合器 - 30 - 3.6软磁铁软体磁芯 32 - 3.6.1 磁性材料的基本特性 - 33 - 3.6.2 磁芯的选用及结构 - 33 - 4.开关电源设计 - 34 - 4.1开关电源集成控制器 - 34 - 4.1.1芯片管脚排列及说明 - 34 - 4.1.2 芯片的基本特性 - 36 - 4.1.3芯片工作原理 - 38