电路分析与电子线路综合训练题DOC43页Word格式文档下载.docx
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2018年《电路分析与电子线路》综合训练组队共同讨论完成综合训练题目3-4题,以书面形式撰写报告,需要详细的讨论过程和仿真的结果。
请同学们自学“数值分析软件(如MATLAB等)及电路仿真软件(如Multisim或Pspice等)”。
提交书面报告时间:
6月20日前。
Project1
PowerSupplies
Objective:
Thisprojectwillshowsomeofthebasicprinciplesofpowersuppliesusingfullwaverectifier,Zenerdiode,andfixed-voltageregulatorcircuits.
Components:
BridgeRectifier(50PIV,1A),Zenerdiode(10Vat500mW),7805regulator
Introduction:
Mostofthedirectcurrent(DC)powerusedinelectronicdevicesisderivedbyconverting60Hz,115Valternatingcurrent(AC)powertodirectcurrentpower.ThisACtoDCconversionusuallyinvolvesastep-downtransformer,rectifier,filter,andaregulator.Thestep-downtransformerisusedtodecreasetheAClinevoltagefrom115VRMStoanRMSvalueneartheDCvoltageneeded.Theoutputofthestep-downtransformeristhenfedintoadioderectifiercircuitthatonlyoutputspositivehalvesoftheinputsinusoid.AfilteristhenusedtosmooththerectifieroutputtoachieveanearlyconstantDCvoltagelevel.Aregulatorcanbeaddedafterthefiltertoensureaconstantoutputvoltageinspiteofchangesinloadcurrentandinputvoltages.
Twodifferenttypesofvoltageregulatorswillbeusedinthisproject.ThefirstinvolvesaZenerdiodecircuitandthesecondinvolvesavoltageregulatorcircuit.AZenerdiodecanbeusedasavoltageregulatorwhenthediodeisreversebiasedandoperatedinthebreakdownregion.Tomaintainvoltageregulation,theZenerdiodemustbeoperatedinthebreakdownregionatacurrentgreaterthanthe"
knee"
current(IZK).ForcurrentsgreaterthanIZK,theZenerdiodecharacteristiccurveisnearlyverticalandthevoltageacrossthediodechangesverylittle.Ofcoursethereisamaximumcurrentthediodecantolerate,sogoodregulationisprovidedwhenthediodeisreversebiasedwithcurrentsbetweenIZKandIZMAX.Zenerdiodesareavailablewithawidevarietyofbreakdownvoltages.Anothertypeofvoltageregulatorisavailablewiththe7800seriesregulators.Thisseriesoffixed-voltageregulatorsisnumbered78xx,wherexxcorrespondstothevalueoftheoutputvoltage.Outputvoltagesfrom5to24voltsareavailable.Theseregulatorsareeasytouseandworkverywell.
Design:
1.FindapproximationsfortheDCvoltagelevelandACpeaktopeakripplevoltageforthebridgerectifierandfiltercircuitofFigure1-1.
2.FortheZenerdioderegulatorcircuitofFigure1-2assumethattheZenerdiodewillregulateat10Voveracurrentrangeof5mAto25mA.AssumingthatthecurrentflowingthroughRisalwaysbetween5mAand25mAandtheZenerdiodeisregulatingat10V,findtheminimumvaluesofRandRLrequired.Youmayassumetheforwarddiodedropforthetwodiodesis≈1V.
LabProcedure:
1.ConstructthebridgerectifiercircuitofFigure1-1withoutthecapacitor.UsetheVariacwiththestep-downtransformerfortheinputvoltagetothebridgerectifier.WiththetransformerpluggedintotheVariac,adjusttheVariacuntilthesecondaryvoltagefromthetransformerequals12VRMS.BECAREFULnottoshortthesecondaryterminals!
Observethesecondarywaveformontheoscilloscope.PuttheoscilloscopeonDCcouplingandobservetheloadvoltagewaveformVL.Rememberthatboththeinputsourceandtheloadcannotshareacommongroundterminal.
2.Removepowerfromthecircuit.InsertthecapacitorasshowninFigure1-1beingsuretoobservethecorrectpolarity.Energizethecircuit.WiththeoscilloscopeonDCcoupling
observeVL.MeasuretheDCvoltagelevelusingthedigitalvoltmeter.WiththeoscilloscopeonACcouplingobservetheripplevoltageVR.Comparethesemeasuredvalueswiththecalculatedvalues.
3.Observetheeffectofloadingonthecircuitbychangingtheloadresistorfrom1kΩ
to500Ω.MeasuretheDCvoltagelevelwiththedigitalvoltmeter.ObservetheripplevoltagewiththeoscilloscopesetonACcoupling.Comparethesevalueswiththepreviouslyrecordedvalues.
4.RecordtheZenerdiodecharacteristiccurvefromthedigitalcurvetracer.Notethevalueofthebreakdownvoltageinthebreakdownregion.Alsonotethevalueofthe"
currentIZK.
5.AfterverifyingyourdesignedvaluesforRandRLwiththeinstructor,constructtheZenerdioderegulatorcircuitofFigure1-2.MeasuretheDCvoltagelevelwiththedigitalvoltmeterfortheminimumvalueofRLalongwithseveralvaluesaboveandbelowtheminimumvalue.BecarefulnottooverloadtheZenerdiode.Commentonthecircuit'
soperationforthesedifferentloadresistances.
6.Constructthe7805regulatorcircuitofFigure1-3beingcarefultoobservethecorrectpinconfigurationoftheregulator.MeasuretheloadvoltageforRLequalto300Ω,200Ω,and100Ω.Calculatethecurrentforeachofthesecases.Doesthevalueoftheloadresistoraffecttheout