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2016年四川省TI杯大学生电子设计竞赛A题：降压型直流开关稳压电源2016年7月28日I摘要随着开关电源技术的迅速发展，DC-DC降压性开关电源已在通信、计算机以及消费类电子产品等领域得到了广泛应用，是当今电子信息产业飞速发展不可缺少的一种电源。近年来，电池供电便携式设备的需求越来越大，对DC-DC开关电源的需求也日益增大，同时对其性能要求也是越来越高。在当前背景下，高频化、小体积化、轻质量化、高效率化、低成本化、安全可靠性乃至绿色化都成了为DC-DC开关电源未来必须追求的发展方向。本设计的降压型直流开关稳压电源采用TI公司的降压控制器LM5117芯片和CSD18532KCSMOS场效应管为核心器件，本着当前降压型直流开关稳压电源的发展方向，此电源设计正是一款效率、质量、电压调整率、负载调整率、纹波均满足设计要求，额定输入电压为16V，额定输出电压为5V，最大输出电流为3A的DC-DC开关电源电路。同时就有负载识别实时输出恒定电压，过流保护的功能。AbstractWiththerapiddevelopmentoftheswitchingpowersupplytechnology,theDC-DCswitchingpowersupplyinthefieldofcommunications,computerandconsumerelectronicsproductshavebeenwidelyusedanditisaindispensablepowersource.Inrecentyears,thedemandforbattery-poweredportabledevicesisgrowing,increasingthedemandforDC-DCswitchingpowersupply,whileitsperformancerequirementsaregettinghigherandhigher.Inthiscontext,thehighfrequency,smallsize,highefficiency,lowcost,safetyandreliabilityaswellasgreenbecametheDC-DCswitchingpowersupplymustpursuethedirectionofdevelopment.Thisdesigntypeofstep-downdcswitchingpowersupplyadoptsLM5117step-downcontrollerchipandCSD18532KCSMOSfieldeffecttubeofTIcompanyasthecorecomponents.Inlinewiththecurrentdevelopmentdirectionoftypestep-downDCswitchingpowersupply,theswitchingpowersupplydesignisaefficiency,quality,voltageregulation,loadregulation,rippleallmeetthedesignrequirements,theratedinputvoltageof16v,ratedoutputvoltageof5v,themaximumoutputcurrentof3aDC-DCswitchingpowersupplycircuit.Thereisloadidentificationreal-timeoutputconstantvoltageatthesametime,thefunctionofover-currentprotection.II目录1系统方案...................................................................11.1方案一................................................................................................................................11.2方案二................................................................................................................................12系统理论分析与计算.........................................................22.1DC-DC变换方法...............................................................................................................22.2稳压控制方法....................................................................................................................22.3降低纹波方法....................................................................................................................23电路与程序设计.............................................................33.1系统总设计.........................................................................................................................33.1.1系统总框图..............................................................................................................33.2主回路设计与器件选择.....................................................................................................33.2.1主回路设计..............................................................................................................33.2.2主要器件的选择......................................................................................................33.3可变电压输出设计.............................................................................................................43.4程序的设计.........................................................................................................................43.4.1程序功能描述与设计思路......................................................................................43.4.2程序流程图..............................................................................................................44测试方案与测试结果.........................................................54.1测试方案.............................................................................................................................54.2测试条件与仪器................................................................................................................54.3测试结果及分析................................................................................................................64.3.1测试结果(数据).......................................................................................................64.3.2测试分析与结论......................................................................................................6参考文献.....................................................................6附录1：电路原理图...........................................................8附录2：DC-DC相关计算........................................................9附录3：源程序..............................................................101降压型直流开关稳压电源（A题）【本科组】1系统方案本设计以LM5117降压控制器和CSD18532KCSNMOSFET场效应管为核心器件，搭建一个DC-DC同步整流降压拓扑变换电路。实现5V固定电压输出，最大3A电流输出，纹波小于50mV，效率高于85%。搭建DC-DC直流稳压器，并引入负载电阻测试功能，能识别电阻的大小来控制输出电压。1.1方案一本方案采用纯硬件的方式来识别电阻大小以及控制输出电压。测电阻时，采用将外接负载识别电阻作为运放的反馈电阻，通过电阻值的变化调节输出电压。通过后级运放输出的高低电平信号来控制LM5117的反馈引脚FB（0.8V参考电压，低于0.8V出电压上升，高于0.8V，输出电压降低）。通过调节几个运放之间的放大倍数，从而实现输出电压与负载电阻的关系。本设计采用纯硬件方式，电路略微复杂，可靠性容易受运放影响，且在调试上会比较困难，识别控制精度较低。1.2方案二本方案采用DC-DC加MCU的方式，使用德州仪器（TI）高性能超低功耗处理器MSP430F5438A为核心控制。将外接负载识别电阻与参考电阻R串联分压后，用单片机内部ADC采集负载识别电阻两端电压大小，从而计算出该电阻阻值，之后配置外部DAC输出相应的电压值用于作为参考电压。将参考电压与LM5117输出的反馈电压用比较器进行