稳压电源中英文翻译

英文原文PAGE1NCswitchingpowersupplyAbstractThissystembasedon51SCMcontrolunit,usedforLM2576-wildnumericalcontrolaswitchingpowersupplyoffuzzydigitalcontroltechnology,adjustloadR1,R2proportiontochangeoccupiesemptiescomparedtomaketheoutputstability,andcanbethroughthebuttons,digitaldisplaytorealizeoutputvoltagenumericalcontrol.Inaddition,thesystemtoinputpressure,flow,inputoutputflow,switchtubeoverheataswellastheprotectioncircuit,ensurethatthesystemisstableandreliable.Keywords:thenumericalcontrolswitchpowersupply，LM2576-wildmicrocontrollerThefirstchaptertasksandrequirements(a)ThetaskDesignandconstructionofaswitchingpowersupply,itsstructurediagramshownasshowninfigure1(b)Requirements1,basicrequirements(1)Basicspecifications:inputvoltage:+10V/DC(fluctuatingrange8to12V)Outputvoltage:+2.5V/DC~+6.5V/DC(2)Thebasictechnicalindex:Theoutputofsubsectionpowershift,and8from+2.5Vto6.5V+,andevery0.5Vincrease.Namely(2.5,3,3.5,4,4.5,5,5.5,6)Efficiency:70%(p<+2.5V/DC,1Atestingaccurate)Maximumoutputcurrent:2A;Voltageadjustmentrate:2%orless;Currentadjustrate:2%orless(3)Canbearbitrarytunedtotherequirementsoftheoutputvoltage,andwithacertainwayofthedisplay.(4)canbearbitrarythroughthekeyboardcontrolopen/closetheoutputvoltage.2.Playapart(1)Haveover-voltageprotection,inputvoltageprotectionmovement,thereare15Vovercurrentprotection,morethan3Aoutputcurrentprotectionmovement(2)Improveefficiency:80%(p<circuitto+2.5V/DC,2Atestingaccurate)(3)Theripple:1%orless(+2.5V/DC,2A20MHzoscilloscopetestingaccurate)(4)Pressfromlowtohighorfromhightoloworderautomaticallychangetheoutputvoltage,eachfile2~3seconds,betweentimeandspaceinthetest.ThesecondchapterschemecomparisonandselectionPlan1:thedivisioncomponents,suchasSelf-excitationswitchingpowersupply,thecircuitprinciplediagramisasfollows:TheinputvoltageforAC220v,50Hzacalternatingcurrent,afterfiltering,againbyrectifierbridgeafterrectifyingintoadc,throughthecontrolcircuitswitchtubeconductionandglobemakehighfrequencytransformerofalowvoltagemeasurementproducehigh-frequencyvoltage,smallpowerbyhigh-frequencytransformercouplingtosecondtest,thenthroughrectifierfilter,getdcvoltageoutput.Inordertomaketheoutputvoltagestability,withtheTL431samplingerror,theopticalcouplingamplifier,throughthePWMtocontrolswitchtubeconductionanddeadline(i.e.occupiesemptiescompared),makestheoutputvoltageremainstable.Fromtheforegoing,thisschemecircuitismorecomplex,difficult,sodon'tdebuggingfeasible.Plan2：DC-DCtransformtheBUCKtypewithA/Dconverter,andconstantlytestingpoweroutputvoltage,dependingonthepowersupplyoutputvoltageandofthedifferenceofthesetvalue,useofPWMmodulePWMwavesinoutput,directcontrolofthepowersupply.ARMextendedbuttons,digitaldisplaytorealizethenumericalcontroloutputvoltage.Thisschemeissimple,butallthecircuitbydivisioncomponents,interference;AndPWMmodulesingle-chipmicrocomputercontrolprogramiscomplicated,consider52andA/Dprogrambetweenfactors,willcausetheoutputofthePWMdelay,distortion,sothattheoutputvoltageisnotquitestable,andsoon.Plan3:thespecialchippowerLM2576-suchaswild,itstypicalcircuitareasfollows:LM2576seriesofstabilizerwhicharemonolithicintegratedcircuit,canprovidethebuckswitchingvoltageregulators(buck)allsortsoffunctions,candrive3Aload,haveexcellentlinearandloadadjustmentability,andLM2576stabilizerinteriorcontainsfrequencycompensationdeviceandAfixedfrequencyasits,thenumberoftheexternalcomponentscanbeminimized,andeasytouse.Thisscheme,220V/50HzacvoltageafterrectifyingcircuitandDC/DCvoltagechipLM2576wildtransformationforstable-DCvoltage,andthenthroughtheadjustmentoftherelationshipofscaleandR2R1toadjustLM2576chipoftheinputoutputvoltagestabilitythanempty.Anexternalcircuitcomponentsnumberless,andtheprogramissimple,andtheoutputvoltagestabilityisgood.Throughvariousprogram,feasibility,complexity,systemindexcomparativeadvantagesanddisadvantagesofeachscheme,comprehensive,weusethethirdplan.Inthethirdchapterofthesystemhardwaredesign(a)Thedesignofthewholesystem1.ThedesignthoughtSystemtomonolithicintegratedcircuitAT89S52,LM2576-forthecorepart,andthewildthroughthemonolithicintegratedcircuittooutputvoltagegather,comparison,operations,andtheoutputvoltagecontrol,automaticregulationsystemstructurediagramshownasshowninfigure1.220V/50HzacvoltageafterrectifyingcircuitandDC/DCvoltagechipLM2576wildtransformationforstable-5~12VDCvoltageoutput,theoutputvoltagethroughsamplingcircuitbysampling,A/DconversionchipADC0804afterconvertingto52afterprocessing,controlsimulationelectronswitchtochoose4051respectivelytheninepotentiometerR2,changeR1andR2ratiovalues,whichchangeLM2576-ofthewildchipPWMpulseofempty,MOStubesworkthantoswitchstatein,theinputof15VDCvoltage"chopped"fortheandofthesamefrequencyPWMwavespulsewave,pulsewavethroughtherectifierfiltercircuitoutputfor5~12VDCvoltage.Becauseofthisthetopicrequesthavenineoutputsteppingdemand,socantuneinadvanceeachvoltageresistance,throughthecorrespondingkeychoiceoutputvoltage,directlytotheanalogswitch4067chooseresistance,theycangettooutputvoltage.Atthesametime,todetectthevoltage,currentvaluethroughthedisplayLCD1062real-timedisplay.Ifworkingcurrentistoobig,theflowdetectioncircuitwillbesenttothetestingresultsofsingle-chipmicrocomputer,SCMcontrolrelaythroughtheacbranchrealizeover-currentprotectionsysteminfault,aftertheoperationissetbytheresetbuttontomaycausethesystemtoresumenormalwork.2.Theblockdiagramofthewholesystem(b)Unitcircuitfunctionandtheanalysisoftheoperation1.MinimumAT89S52SCMsystemMinimumsystemincludingcrystaloscillatorcircuitandresetswitchandpowersupplyparts.Figure2fortheminimumAT89S52SCMsystem.2.Rectifiercircuit.Thewaverectifiercircuitismadeupoftwohalfwaveofrectifiercircuit.Becauseinthenexttwo,addonmiensinputvoltageoftheoppositepolarity,therefore,toadynamicbalance,ineverysignalcycle,theC1andC2experience2timescharger,dischargeprocess,currentwillappeartwocurrentpulsewithpolarity.SoinadditiontotheVosawtoothwaveonthewavyfrequency,improvetheabilityofdoublefiltering,thusreduceripplevoltage.3.PowersupplycircuitThedcpowerbypowersupply,filtering,protection,suchasvoltage,fourbasicmodules.(1)ThepowertransformerUSESastep-downtransformer,thepowergridvoltage220Vtransformintoneedacvoltage.TheacvoltageAfterrectifying,mayobtainelectronicequipmentneeddcvoltage.(2)Userectifiercircuitbridgerectifiercircuitsingle-phase,50HzacalternatingcurrenttransformationfordirectioninvariablebutstillhasthepulsesizestraightFlowelectricity.Itsadvantageishighvoltageripplevoltage,small,theutilizationrateoftransformerhigh.ThisdesignbyAbridgepileofbridgerectifier,RS808domaximumcurrentcanreach8A,cooperatewiththedesignofthelargefiltercapacitance,sothepoweroftheinstantaneouslargecurrentpowersupplycharacteristics,lownoise,goodreactionspeed,outputripplesmall.（3）Filtercircuitusingcapacitancefiltercircuit,willthepulsationoftherectifiercircuitoutputfilter,getmostofthecomponentsissmoothdctheelectricity.Thiscircuitadopts4700uF/50VlargecapacitanceC3,C4tomaketheoutputvoltagemoresmooth,thepowersupplycharacteristicsmoment,suitablefortaketheperceptualload,suchasmotorstart-up.C3,C4everyparallelconnectiona0.1uF/63VCBBcapacitance,filtertohighfrequencyinterference,makeinputtointegratedcircuitsL11,L12ofdcasfaraspossiblethesmoothandpure.（4）ByLM317outputvoltagecircuitispower,LM337outputnegativesupply.LM317andLM337areusedinternalheatLoad,containsovercurrentprotection,hotoffandsafetyworkingareaforperfectprotectioncircuit,thatpowercansavethefuse,andsoeasylossdevice.Regulatingcircuit:tomeettheneedsofthedifferentapplicationsituationandthevoltageissettocanbeadjusted.ThecalculationoftheoutputvoltageVo=1.25x(1+Rf/R),adjustableresistanceinuseprecisioncanberesistorandguaranteethepreciseoutputvoltagecanbeadjusted.Ifthisarticlechoosesfor5kofRfΩ,Rfor270Ωcombination,canrespectivelyon1.25V~24V1.25V~24Vachievecontinuousadjustablebetween.（5）Protectioncircuitforlinearpowersupplyheat,sothepowerlargeraddenoughradiator.Duetothehighperformanceintegratedcircuit,whichcansimplifythecircuitstructure,highlightingtheimportantpartinthepowertransformation.Throughthecommissioningandtesting,goodperformance.ThewholecircuitThepowernotonlycanbeusedalone,alsocanbeinotherelectronicequipmentusedinvoltageorcurrentstabilizationsourceuse.4.LM2576-voltagecircuitwildWorkingprinciple:Assumethattheswitchtransistors,diodesareidealcomponents,inductanceandcapacitanceisidealcomponents,theoutputvoltageripplevoltageoutputvoltageandtheratioofthesmalltoallowoversight.AccordingtothecurrentcycletobegininILinductanceisstartingfromscratch,canbedividedintocurrentcontinuousworkingmodeandinductanceinductivecurrentisdiscontinuousworkpatterns.Duetothecontinuousworkmodeinductancecurrentconverter,haveverygoodcontrolcharacteristic;Inductivecurrentisdiscontinuousworkmode,puttheelectric,inductanceandcapacitanceeasytoproducetheoscillation,thusaffectingtheoutputvoltageripple;Andthesameoccupiesemptiescompared,outputvoltageindiscretemodelunderthemodeofworkthanthebig,highefficiency.Tosumup,themostidealsituationisincriticalcondition,stabilizerwhichworksoweusetwokindsofmethods:(1)Theincreaseoftheinductanceinductiveenergystorage,increase,andextendthedischargeoftime(2)ImprovetheworkandreducethefrequencyswitchtimeMaketransistorincurrentcontinuousstate.5.ThewholewaveoutputrectifiercircuitparameteranalysisOutputfilterbyfree-wheelingdioderectifiercircuit,inductanceandcapacitancecomposition.Considerfree-wheelingdiodeintubebyPMOStransistorconduction,whenenergyconsumption,andworkinthestate,soweusedthelowpowerconsumption,highcurrent,high-speedScottydiodesIN5817,thecharacteristicsasfollows:Maximumpeakreversevoltage:40VThebiggestreverseRMSvoltage:28VThebiggestdcvoltage:40VblockThebiggestpositiveaveragerectifiercurrent:1AThebiggestpositivepressuredrop:0.6V(1A)BUCKconverterprinciplebyanalysisshowsthatinordertomakeworkininductivecurrentcircuitcontinuousmode,andtheripplevoltageSoasfaraspossible,shouldbemadegreatinductancewechoosefor8mHinductanceCapacitorsmainlyisthe"absorb"ripplewithasmooth,theroleofthevoltagewaveform.Capacitanceandinductanceisequivalenttoalowpassfilteringfilter,thecut-offfrequencydefinedasConsideringthecapacitanceequivalentseriesresistancelosses,wechoosethecapacitancefor1000uF.Atthistimethecut-offfrequencyofabout562Hzac,visibletodozensofkHzPWMwaveshaveverygoodfilteringeffect.6.Inputover-voltageprotectionWhentheinputvoltageinthenormalrange,theinputsamplingvoltagecomparator,lessthanthebenchmarkvoltageoutputlowlevel;Whentheinputpressure,inputvoltageisgreaterthanthebenchmarksamplingcomparisonoutputvoltage,highlevel,ARMproduceexternalinterruption,warning,blockade,makePMOStransistortubePWMsignal,inordertoprotectthecircuitdamage.7.Over-currentprotectionUsuallywithhallcurrentsensordetectionofcurrentdirectlyPMOStransistor,andthenwithsettingtheIdthresholdvalue,comparedwithcomparisontocontroltheoutputofthedriversignalshutoff;Orbyindirectmethod,theflowtestvoltagewhenthevoltagedroptheVsdPMOStransistor,becausethepressuredropcontainsshort-circuitcurrentinformationflow,whentheVsdincreasing,andbasicallyforlinearrelationshipbetweentheflowoftesting,whentheVsdandwithsettingthethresholdvalueisusedinthecomparison,thecomparatoroutputcontrolpowercircuitoftheshutoff.8.LCDdisplaycircuitChapter5systemcommissioning1.ThesoftwaredebuggingThedesignofthesoftwareismoresimple,onlythekeysandLCDdisplaytwomodules.Throughthekeycontroloutputvoltageandthechangeofthecommissioning,abegantodiscoverthatstepissometimes0.5v,sometimesbecome1v,thenaddthedelay,eliminatebuttonsditherprogramcan.2.HardwaredebuggingFirstofall,pointsmoduledebugging.First,thendebuggingpowermoduleLM2576-and4067wildvoltageanalogswitchmodule,firstwithhighandlowleveldirectlyelected4067,usingamillimeterstomeasuretheoutputvoltageiscorrect,afterrightinwith4067single-chipmicrocomputercontrol,observationoutputvoltage,withascrewdriverfine-tuningnineR2resistance,changeandanumberofR2R1toadjustoutputvoltage.Throughthesepreliminarycommissioning,theoutputvoltagetendtobenormal.3.Themachinecommissioning1)theoutputvoltagecanonlyto5.62v,highestcan'tcarryitupagain.Reason:analogswitchofthe4067workingvoltageandchoosetoosmall.Thesolution:themicrocontrolleroutputand4067atransistor,indirecttransistorisinstate,whentransistorswitchwhenclosed,4067thevoltagebylargevoltagechoose,sothat,oncethesingle-chipmicrocomputerchoosethe4067,theworkingvoltageincrease.2)Keyspressed,foundthestepvoltageissometimes0.5v,sometimesis1v.Reason:usuallywekeyspressed,therewillbedelayjittereffect.Solution:intheprogramandbuttonincasetimedelayjitterprogram.3)whentheSCMP1mouthdirectlyelectedin4067theoutput,measuredusingamultimediaP1mouthoutputlevel,foundthattotalforthelowlevel,willsingle-chipmicrocomputerand4067connectionsdisconnected,usingamultimediaafterinthemouthoutputlevel,foundtheP1normal.Reason:52chipiswithaeraseprogramafterboardofthesmallestsystemdirectlyintothegeneraleffect,choose4067outputlevelwillbedown.Thesolution:thepresstheresetbutton52singlechipcan.PAGE14Chapter6systemtests1.Thetestprojectcircuit2.TestinginstrumentsThreeandahalfdigitalmultimedia(MASTECHmy61)Dcpowersupply(MOTECHLPS-305)Digitaloscilloscopes(TektronixTDS1002)3.Testresults1)intheinputvoltagefor15V,respectivelyfor200ohmload,150ohm,100ohm,outputvoltageaccuracyofthetest2)intheinputvoltagefor15V,loadresistancefornominalresistance(i.e.currentfor500mA),outputripplevoltageandefficiencytest3)theinputvoltagechangecircumstances,outputvoltagerippleandefficiency,precisiontestingFromthetablethreecansee,calibrationconstantinputvoltage,thehigherthevoltage,theripplevoltage,thegreatertheinputcurrentissmaller,thelowertheefficiency.

【reference】[1]GaoJiXiang.Analogelectroniccircuitdesign[M].Beijingelectronicindustrypress,2007[2]ZhouZhiGuang.Microcontrollertechnologyandapplication[M].Hunanzhongnanuniversitypress,2005[3]YanShi.Digitalelectronictechnologybase【M】highereducationpress.Beijing.2004[4]PengJieHua.The"curriculumdesignofelectronictechnology[M].Beijingguidanceofhighereducationpress,1999[5]HuangYouQuan.LiGuiPing.BasedonthedesignofmanyChinesecharactersAT89S52display【J】.Electronicdesignengineering,2008中文译文PAGE30数控开关稳压电源摘要 本系统基于51单片机为控制单元，采用LM2576-ADJ数控开关稳压电源中的模糊数字控制技术，调整负载R1,R2比例来改变占空比使输出稳定，并且可通过按键、数码显示实现输出电压数控。此外，系统加以输入过压、输入过流、输出过流、开关管过热等保护电路，保证系统稳定可靠地工作。关键字：数控开关电源LM2576-ADJ单片机第一章任务与要求（一）任务设计并制作一个开关电源，其结构框图如图1所示图1

电路框图

（二）要求1、基本要求(1)基本规格：输入电压：+10V/DC

(波动范围8~12V)输出电压：+2.5V/DC~+6.5V/DC(2)基本技术指标：输出电压分8档，从+2.5V到+6.5V，每0.5V递增。即(2.5,3,3.5,4,4.5,5，5.5,6)效率：≥70%

(以+2.5V/DC,1A测试为准)最大输出电流：2A；

电压调整率：≤2%；

电流调整率：≤2%(3)可任意调到要求的一档输出电压，并用一定的方式显示出来。(4)可任意通过键盘控制打开/关闭输出电压。2、发挥部分(1)有过压保护，输入电压15V保护动作，有过流保护，输出电流大于3A保护动作(2)提高电路效率：≥80%

(以+2.5V/DC,2A测试为准)

(3)纹波：≤1%

(以+2.5V/DC,2A，20MHz示波器测试为准)(4)按从低到高或从高到低顺序自动改变输出电压，每档间隔2~3秒，测试时空载。第二章方案比较与选择方案1：采用分立元件，例如自激式开关稳压电源，电路原理图如下：输入电压为AC220v，50Hz的交流电，经过滤波，再由整流桥整流后变为直流，通过控制电路中开关管的导通和截止使高频变压器的一次测产生低压高频电压，经由小功率高频变压器藕合到二次测，再经整流滤波，得到直流电压输出。为了使输出电压稳定，用了TL431取样，将误差经光耦合放大，通过PWM来控制开关管的导通与截止时间（即占空比），使得输出电压保持稳定。 由上可见，这种方案电路比较复杂，调试难度大，所以不可行。方案2：开关变换电路开关变换电路输出滤波整流电路采样电路AT89S52A/D处理PWM按键显示PMOS驱动电路20V输入5～12V输出过压、过流、短路、过热外部中断A/D转换DC-DC变换采用BUCK型变换器，用A/D不断检测电源的输出电压，根据电源输出电压与设定值之差，利用片内PWM模块输出PWM波，直接控制电源的工作。ARM扩展按键、数码显示功能实现数控输出电压。 此方案电路虽简单，但均由分立元件组成，受干扰大；并且PWM模块中单片机52控制程序复杂，考虑与A/D程序切换等因素，会造成输出的PWM波形延迟、失真，这样致使输出电压不够稳定等等。方案3：采用电源专用芯片如LM2576-ADJ，其典型电路如下：LM2576系列的稳压器是单片集成电路，能提供降压开关稳压器（buck）的各种功能，能驱动3A的负载，有优异的线性和负载调整能力，并且LM2576稳压器内部含有频率补偿器和一个固定频率正当其，能将外部元件的数目减到最少，使用简便。本方案中，220V/50Hz交流电压经过整流电路和DC/DC稳压芯片LM2576-ADJ变换为稳定的直流电压，然后通过调整R1和R2的比例关系来调整LM2576芯片的输入占空比来稳定输出电压。外部电路元件数量较少，程序也比较简单，并且输出电压稳定性也比较好。通过对各种方案可行性、复杂程度、系统指标等方面的比较，综合各方案的优缺点，我们采用第三种方案。第三章系统硬件设计（一）系统的总体设计1. 设计思想系统以单片机AT89S52、LM2576-ADJ为核心部件，通过单片机对输出电压进行采集、比较、运算，从而对输出电压进行自动调节控制，系统结构框图如图1所示。220V/50Hz交流电压经过整流电路和DC/DC稳压芯片LM2576-ADJ变换为稳定的直流电压5～12V输出，输出电压通过取样电路采样，经A/D转换芯片ADC0804转换后送给52处理后，控制模拟电子开关4051来分别选通9个电位器R2，改变R1和R2比例值，从而改变LM2576-ADJ芯片的PWM脉冲的占空比，使MOS管工作于开关状态，将输入的15V直流电压“斩波”为与PWM波频率相同的脉冲波，脉冲波通过整流滤波电路输出为5～12V的直流电压。因为此题目要求有9个输出步进需求，所以可以事先调好每个电压对应的电阻值，通过按键选择输出电压，直接送给模拟开关4067选通电阻，就可以得到要输出的电压。同时将检测到的电压、电流值通过显示器LCD1062实时显示。若工作电流太大时,过流检测电路将检测结果送至单片机,单片机通过控制继电器切断交流支路实现过流保护,系统在故障后通过操作设置的复位键可以使系统恢复正常工作。2. 系统总体框图LM2576-ADJ稳压电路LM2576-ADJ稳压电路输出滤波整流电路LCD显示电路AT89S52LCD控制PWM按键显示选通模拟电子开关4052，控制电位器R2220V/50Hz交流电压输入5～12V输出过压、过流、短路外部中断整流电路图1系统总体框图（二）单元电路功能以及工作原理的分析AT89S52单片机最小系统最小系统包括晶体振荡电路、复位开关和电源部分。图2为AT89S52单片机的最小系统。图2AT89S52最小系统图整流电路图3整流桥电路全波整流电路是由两个半波整流电路组成。由于加在上、下两整流管的输入交流电压极性相反，因此，达到动态平衡后，在每一个信号周期内，C1和C2经历2次充、放电过程，电流会出现两个同极性电流脉冲。因此叠加在Vo上的锯齿波状波动频率加倍，提高了滤波能力，从而减小纹波电压。电源电路图4电源电路本直流电源由电源、滤波、保护、稳压等四个基本模块组成。（1）电源变压器采用降压变压器，将电网交流电压220V变换成需要的交流电压。此交流电压经过整流后,可获得电子设备所需要的直流电压。（2）整流电路利用单相桥式整流电路,把50Hz的交流电变换为方向不变但大小仍有脉动的直流电。其优点是电压较高、纹波电压较小,变压器的利用率高。本设计用桥堆RS808做全桥整流,最大电流可达8A,配合本设计的大滤波电容,使得本电源的瞬时大电流的供电特性好、噪声小、反应速度快、输出纹波小。（3）滤波电路采用电容滤波电路,将整流电路输出的脉动成分大部分滤除,得到比较平滑的直流电。本电路采用4700μF/50V的大电容C3、C4使输出电压更加平滑,电源瞬间特性好,适合带感性负载，如电机的启动。C3、C4各并联了一只0.1μF/63V的CBB电容，滤去高频干扰,使输入到集成电路L11、L12的直流电尽可能的平滑和纯净。（4）稳压电路由LM317输出正电源,LM337输出负电源。LM317和LM337均使用了内部热过载,包含过流保护、热关断和安全工作区补偿等完善的保护电路,使得电源可以省去保险丝等易损耗器件。调节电路:为适应不同应用场合的需要而将电压设置为可调。输出电压的计算Uo=1.25×(1+Rf/R),可调电阻选用精密可调电阻,保证输出电压的精确可调。如本文选用的Rf为5kΩ、R为270Ω的组合,可以分别对1.25V～24V-1.25V～-24V之间实现连续可调。（5）保护电路因为线性电源发热量较大，所以本电源中加了足够的散热器。由于采用高性能的集成电路,从而简化了电路的结构,突出了电源变换问题中的关键部分。通过调试与检测,电路整体性能良好。本电源不仅可以单独使用,还可以置于其他电子设备中用作稳压或稳流源使用。LM2576-ADJ稳压电路原理框图如下：图5LM2576-ADJ构成的DC/DC转换电路工作原理：假定开关晶体管、二极管均是理想元件，电感、电容是理想元件，输出电压中的纹波电压与输出电压的比值小到允许忽略。三极管工作在开关状态，如下：图6想情况下变化器原理导通（开关S位置在A）电流is流过电感线圈，在电感线圈未饱和前，电流线性增加，在负载R上流过电流Io,两端输出电压Vo，极性上正下负。当is>Io时，电容在充电。这时续流二极管承受反向电压截止（开关S位置在B）由导通到截止，线圈L中的磁场改变线圈L两端的电压极性，以保持其电流iL不变。负载R两端电压仍是上正下负。iL<Io时，电压处在放电状态，有利于维持Io、Vo不变。这时二极管D1，承受正向偏压为电流iL构成通路。按电感电流IL在周期开始时是否从零开始，可分为电感电流连续工作模式和电感电流不连续工作模式。由于电感电流连续工作模式下，变换器有很好的控制特性；电感电流不连续工作模式下，电感放完电，电感与电容容易产生振荡，从而影响输出电压的纹波；又相同的占空比，输出电压在不连续模式工作模式下比大，效率高。综上所述，最理想的情况是稳压器工作于临界状态，所以我们采用两种方法：①增大电感值，增加电感储能，延长放电时间 ②提高开关工作频率，减小开关断开的时间使三极管工作在电流连续状态。 输出整波整流电路参数分析输出滤波整流电路由续流二极管、电感和电容组成。考虑续流二极管在PMOS管截止时导通，消耗能量，又工作于高速状态，所以我们采用了低功耗、大电流、超高速的肖特基二极管IN5817，其特性如下：最大峰值反向电压：40V最大反向有效值电压：28V最大直流阻断电压：40V最大正向平均整流电流：1A最大正向压降：0.6V（1A）由BUCK变换器原理分析可知，为了使电路工作在电感电流连续模式下，又纹波电压所以电感应该尽可能取得大，我们选择的电感为8mH 电容主要是“吸收”纹波，具有平滑电压波形的作用。电容与电感相当于一个低通滤波滤器，其截止频率定义为考虑到电容上等效串联电阻的损耗，我们选择的电容为1000uF。此时截止频率约为562Hz，可见对于几十kHz的PWM波有很好的滤波效果。输入过压保护 当输入电压在正常范围，输入采样电压小于基准电压，比较器输出低电平；当输入过压，输入采样电压大于基准电压，比较器输出高电平，ARM产生外部中断，发出警报，封锁PWM信号，使PMOS管截止，从而保护电路损坏。图7输入过压保护电路过流