昆明理工大学自动化专业英语翻译PPT课件

机电或自动化专业英语,教材：王军教授、宋舒教授主编的由重庆大学出版社出版的自动化专业英语,基本目标：基本能够比较顺利、准确地阅读机电专业方面的英文书刊、文献、技术资料，在这方面具备一定的翻译和沟通、表达、交流能力。,SpecializedEnglishforElectromechanization(Electro-Mechanism),Howtospeak“专业英语”inEnglish？Andhowabout“机电专业英语”?,Content,ElectronicTechnology,BipolarJunctionTransistorsUJTThyristorsandSCRsOperationalAmplifiersFlip-FlopsDigitalSystemDecodingFiltercircuit,Content,ElectronicTechnology,Direct-currentRegulationPhaseControlUnijuncityTransistorPulseTriggering,ControlTheory,IntroductiontoControlSystem,Content,ControlTheory,PerformanceSpecificationsofControlSystemSecond-OrderSystemsDigitalControlSystemStateEquation,Content,ComputerTechnology,TheApplicationofComputer,ElectricDrive,DCMotors,BipolarJunctionTransistor,WordsandTerms,Transistortrnzist:电子晶体管Bipolarbaipul:有两极的,双极的Polaritypulriti:极性Negativenegtiv:负的,阴性的semiconductorsemikndkt:半导体crystalkristl:结晶，晶体，晶粒,BipolarJunctionTransistor,WordsandTerms,symbolsimbl:符号,记号,象征emitterimit:发射极collectorklect:集电极formulaf:mjul:公式,规则,客套语reverseriv:s:相反的,倒转的,颠倒的biasedbaist:结果偏倚的,数有偏的,BipolarJunctionTransistor,Text,Today,industrialelectronicsystemsemploy,severaldevicesthataredescribedbythetermtransistor.,BipolarJunctionTransistor,Text,Eachtypeoftransistorhasdifferentcharacteristicsandoperationalconditionsthatareusedtodistinguishitfromothers.,每种晶体管都有区别于其它种类的特征和工作环境。,BipolarJunctionTransistor,Text,Inthefirstpartofthisdiscussion,weareconcernedwiththebipolarjunctiontransistor.Structurally,thistransistorisdescribedasbipolarbecauseithastwodifferentcurrent-carrierpolarities.,首先探讨双极型晶体管。从结构上看，这种晶体管被称为双极是因为它具有两种不同的电流载流子电极。,BipolarJunctionTransistor,Text,Holesarepositivecurrentcarriers,whereaselectronsarenegativecurrentcarriers.,空穴是正的载流子，电子是负的电流载流子。,BipolarJunctionTransistor,Text,Twodistinctkindsofsemiconductorcrystalsareconnectedtogetherbyacommonelement.,两种截然不同的半导体晶体通过公共元件连接在一起。,BipolarJunctionTransistor,Text,Thestructureofthisdeviceissimilartothatoftwodiodesconnectedbacktoback,withonecrystalbeingcommontobothjunctions.Thecentermaterialisusuallymadethinnerthanthetwooutsidepieces.,该器件的结构类似于背靠背连接的两个二极管的结构，一个晶体同时属于两个结。其中间的材料通常比两个外边的作得窄些。,BipolarJunctionTransistor,Text,IntheoperationofasinglePNdiodejunction,forwardbiasingcausesconductionandreversebiasingcausesnonconduction.,单个PN二结的工作情况是：正向偏置促使其导通，反向偏置导致其截止。,BipolarJunctionTransistor,Text,Inatransistor,thisruledoesnotapplydirectlybecausetwojunctionsareinvolved.,因为晶体管包含两个结，该规则不能直接应用,Forexample,whentheemitter-basejunctionisforwardbiased,itcausesalargeamountofIEtoenterthebaseregion.,例如，其发射-基极处于正向偏置时，它会促使大量的IE进入基区。,BipolarJunctionTransistor,Text,Reversebiasingofthebase-collectorjunctionwouldordinarilyrestrictthiscurrent.,而基-集电极的反向偏置会限制该电流。,Butduetothethinbasestructure,IEwillimmediatelyenterintothecollectorcurrentICoroutputcurrent.,但因基区窄，IE会很快进入集极电流IC或输出电流.,BipolarJunctionTransistor,Text,Forwardbiasingoftheemitter-basejunctionthereforealtersorreducesthereversebiasingeffectofthebase-collectorjunctioninnormaltransistoroperation.,因而，在一般的晶体管工作中，发射-基结的正向偏置会改变或减少基-集结反向偏置的影响。,BipolarJunctionTransistor,Text,Atransistorisprimarilyclassifiedasacurrent-operatingdevice.ThismeansthattheoutputorcollectorICwilloccuronlywhentheemitter-baseisforwardbiasedandproducingbasecurrent.,晶体管被划分为基本电流型器件。这意味着仅仅当发射-基结处于正偏且有基极电流IB时才会有其输出或集电极电流IC,BipolarJunctionTransistor,Text,Whenthebasecurrentceases,collectorcurrentstopsandthetransistorbecomenonconductive.Thisconditioniscalledcutoff.,当基极电流消失时，集电极电流停止，晶体管处于非导通状态。这种情况就称为截止。,BipolarJunctionTransistor,Text,Ontheotherhand,ifanexcessiveamountofbasecurrentoccurs,thetransistorisdrivenintosaturation.Whenthisconditionoccurs,afurtherincreaseinIBwillnotcauseacorrespondingchangeinIC.,相反，如果基极电流过大，晶体管处于饱和状态。在这种情况下，再增加IB不会引起IC的相应变化。,BipolarJunctionTransistor,Text,Whenamplitudecontrolisbeingachieved,atransistorisrarelyoperatesinthesaturationregion.Whenatransistorisusedasaswitch,itusuallyoperatesinthesaturationregion.,进行幅值控制时晶体管几乎不会处于饱和区。而当它作为开关使用时，经常工作在饱和区。,UJTThyristorsandSCRs,WordsandTerms,unijunctionju:nidkn:单结emitterimit:发射极collectorklect:集电极formulaf:mjul:公式,规则,客套语reverseriv:s:相反的,倒转的,颠倒的biasedbaist:结果偏倚的,数有偏的,UJTThyristorsandSCRs,Text,Thyristorsshouldnotbeconfusedwithbipolarjunctiontransistorsorfield-effecttransistors.,不应将晶闸管与双结型晶体管（bipolarjunctiontransistors，BJTs）或场效应管（field-effecttransistors，FETs）混淆起来.,UJTThyristorsandSCRs,Text,BJTsandFETsarebothcapableofperformingswitchingoperations.Asarule,thesedevicesarenotasefficientasthyristoranddonothavethepower-handlingcapability.,BJTs与FETs都能够完成开关操作。按照惯例，这些器件并没有晶闸管那么有效率且不具备功率（电力）处理能力。,UJTThyristorsandSCRs,Text,Thyristorsareusedaspowercontroldevices,whereastransistorsareprimarilyusedinamplifyingapplications.,晶闸管通常用作电力控制器件，而晶体管主要用于信号放大。,UJTThyristorsandSCRs,Text,Avarietyofunidirectionalthyristorsisnowbeingusedinindustrialelectronicapplications.Oneofthefirsttobedevelopedwasthesilicon-controlledrectifier(SCR).Thetermthyristorwasderivedformthewordsthyratron-transistor.,工业电子应用系统目前使用了很多种单向晶闸管。可控硅整流器（silicon-controlledrectifier,SCR）就是最初开发出的三极管之一。术语晶闸管“thyristor”源自于单词“thyratron-transistor”。,UJTThyristorsandSCRs,Text,AnSCRisclassifiedasareverseblockingtriodethyristor.Thismeansthatthedevicehasconductibilityinonlyonedirection.Whenitsanodeandcathodearereversebiased,thedevicewillnotconduct.,SCR被归类为反向阻断晶闸管。这意味着该器件仅在一个方向上导通。当其阳极、负极处于反偏时，它不导通。,UJTThyristorsandSCRs,Text,Thesilicon-controlledswitch(SCS)andtheprogrammableunijunctiontransistor(PUT)aretwootherthyristorsofthisclassification.,可控硅开关(silicon-controlledswitch,SCS)和可编程单结晶体管(programmableunijunctiontransistor,PUT)是该类的另外两种晶闸管。,OperationalAmplifiers,WordsandTerms,op-amp(operationalamplifiers)upmpn.运算放大器triangletraigln.三角形differentialamplifier差动放大器impedanceimpi:dnsn.阻抗push-pulla.推挽（式)的polaritypulritin.极性,OperationalAmplifiers,WordsandTerms,common-moderejectionratio(CMRR)n.共模抑制比率substantialsbstnla.大的，大量的，物资的mi:djta.中间的single-endeda.单端的，单向的emitter-followamplifiern.射极跟随放大器complementary-symmetrya.互补对称的,OperationalAmplifiers,WordsandTerms,couplekplv.耦合，结合reversalriv:slv.反向，反转，换相resistancerizistnsn.电阻constant-currentsourcen.恒流源dual-polaritydju(:)lpulritin.双极（性）invertinv:tv.反向，反转,OperationalAmplifiers,Text,Theinternalconstructionofanop-ampisquitecomplexandusuallycontainsalargenumberofdiscretecomponents.,运算放大器的内部结构非常复杂，它通常包含大量的分离元件。,OperationalAmplifiers,Text,Apersonworkingwithanop-ampdoesnotordinarilyneedtobeconcernedwithitsinternalconstruction.Itishelpful,however,tohavesomegeneralunderstandingofwhattheinternalcircuitryaccomplishes.,使用运算放大器工作的人一般并不需要关心其内部结构。然而，了解其内部电路所具备功能的一般常识是很有帮助地。,OperationalAmplifiers,Text,Thispermitstheusertoseehowthedeviceperformsandindicatessomeofitslimitationsasafunctioningunit.,这就让用户明白该器件是怎样工作的，当然也显示出其作为一个功能单元的一些局限。,OperationalAmplifiers,Text,Thefirststageorinputofanop-ampisusuallyadifferentialamplifier.Thisamplifierhastwoinputs,whicharelabeledV1andV2.,运算放大器的输入或者其第一级通常是一个差分放大器。该放大器有两个分别标为V1、V2的输入端。,OperationalAmplifiers,Text,Itprovideshighgainofthesignaldifferencesuppliedtothetwoinputsandlowgainforcommonsignalsappliedtobothinputssimultaneously.,它对同时施加在两个输入端的差分、共模信号分别提供高、低增益。,OperationalAmplifiers,Text,Theinputimpedanceishightoanyappliedsignal.Theoutputoftheamplifierisgenerallytwosignalsofequalamplitudeand180ooutofphase.Thiscouldbedescribedasapush-pullinputandoutput.,对于任意信号，输入阻抗均很大。它一般输出幅值相同而相位相差180o的两路信号。这可称为推拉式输入输出。,Flip-Flops,WordsandTerms,flip-flopflipflpn.双稳态多谐振荡器，触发器memorymemrin.存储器manipulatemnipjuleitv.操纵，处置clockpulse时钟脉冲modification.mdifikeinn.修改，改变，改进型,Flip-Flops,WordsandTerms,toggletgln.反复电路mechanismmeknizmn.机械装置，机构electromechanicali.lektrumiknikl机电的photoelectrical.futuilektrikla.光电的,Flip-Flops,WordsandTerms,acousticalku:stikla.听觉的，声学的togglefilp-flopn.反转触发器presetpri:setv.a.预调（的），预置（的）sequentialsikwenla.连续的，有序的，结果的,Flip-Flops,WordsandTerms,versatilev:staila.通用的，多用途的，易变的countern.计数器endlessa.不断的，环状的pulsegenerator脉冲发生器numericaln(j)u:merikla.数字的，数值的,Flip-Flops,WordsandTerms,rippleripln.脉动，波动ICchipn.集成电路芯片,Flip-Flops,Text,Flip-flopsarecommonlyusedtogeneratesignals,shapewaves,andachievedivision.,触发器通常用于产生信号、整形波形、实现分频。,Inadditiontotheseoperations,aflip-flopmayalsobeusedasamemorydevice.,除此之外，它也可用作存储器件。,Flip-Flops,Text,Inthiscapacity,itcanbemadetoholdanoutputstateevenwhentheinputiscompletelyremoved.Itcanalsobemadetochangeitsoutputwhenanappropriateinputsignaloccurs.,至于这方面，甚至当输入信号完全去除时它都能保持输出状态。当出现合适的输入信号时，也可用它来改变其输出状态。,Flip-Flops,Text,Inmanydigitalsystemapplications,flip-flopsmustbesetandclearedatspecifictimeswithrespecttootheroperationcircuits.,许多数字应用系统在特定时刻参照其其它运算电路须要求对触发器进行置位、清零。,Thistypeofoperationcanbeachievedbymanipulatingflip-flopsinstepwithaclockpulse.,这类操作可通过逐步控制触发器实现。,Flip-Flops,Text,Inthiscase,theappropriateRSinputsandclockpulsemustallbepresentinordertocauseastatechange.AdeviceofthistypeiscalledanRStriggeredflip-floporsimplyanRSTflip-flop.,在这种情况下，须要有合适的RS输入信号和时钟脉冲以改变触发器的状态。这种器件就称为RS触发的触发器或者简称为RST触发器。,Flip-Flops,Text,Oneofthemostversatileandimportantlogicdevicesofdigitalsystemisthecounter.Thisdevice,asageneralrule,canbeemployedtocountawidevarityofobjectsinanumberofdifferentdigitalsystemapplications.,计数器是数字系统的最通用、重要的逻辑器件之一。作为惯例，它可对许多不同数字应用系统中的大量物体进行计数。,Flip-Flops,Text,Whilethisdevicemaybecalledupontocountanendlessnumberofobjects,itessentiallycountsonlyonething,electronicpulses.,尽管可以说该器件能对数不清的物体进行计数，本质上，它仅仅对一种物体进行了计数，即电脉冲。,Flip-Flops,Text,Thesepulsesmaybeproducedelectronicallybyaclockmechanism,electromechanically,photoelectrically,acoustically,orbyanumberofotherprocesses.Thebasicoperationofthecounter,however,iscompletelyindependentofthepulsegenerator.,这些脉冲可由机电式、电子光学式、声音式或许多其它形式的脉冲机构产生。然而，计数器的基本工作完全独立于这些脉冲产生器。,Flip-Flops,Text,Acommonapplicationofthedigitalcounterisusedtocountnumericalinformationinbinaryform.,数字计数器的一个普通应用就是对二进制形式的数字信息进行计数。,Flip-Flops,Text,Thistypeofdevicesimplyemploysanumberofflip-flopsconnectedsothattheQoutputofthefirstdevicedrivesthetriggerorclockinputofthenextdevice.Eachflip-flopthereforehasadivide-by-2function.,这类器件仅仅使用了大量的触发器，这些触发器顺次连接起来以便于第一个触发器的输出驱动下一个触发器的触发引脚或者时钟输入。每个触发器因此具有2分频功能。,DigitalSystemDecoding,WordsandTerms,displaydevicen.显示装置decodedi:kudv.译码fluidflu:idn.流体，液analogn.模拟量abruptlybrptliad.突然的，陡峭的decimaldesiml十进制,DigitalSystemDecoding,WordsandTerms,stripstripn.条，带punchedcard穿孔卡片magnetictapemgnetikteipn.磁带interfaceintfeisn.接口，界面，连接处sensitivity.sensitivtin.灵敏度,DigitalSystemDecoding,WordsandTerms,accuracykjursin.准确度，精确度，精度liquid-crystallikwidkristln.液晶decoderdi:kudn.译码器energizeendaizv.通电，激励，供以能量groundingn.接地,DigitalSystemDecoding,WordsandTerms,segmentsegmntn.段，部分，环节manualmnjula.手控的，手动的distinctdistikta.性质（种类）不同的discretediskri:ta.分离的，不连续的necessitatensesiteit需要，以为条件flat-package平（扁）的外壳或部件,FilterCircuit,WordsandTerms,filtercircuitfilts:kitn.滤波电路smoothsmu:n.平滑的，平稳的indexindeksn.指标，指数，索引variation.vrieinn.变量，变化，变种ripplefactorriplfkt脉动系数,FilterCircuit,WordsandTerms,rmsvalue均方根指，有效值capacitorkpsitn.电容器intervalintvln.时间间隔，周期periodpiridn.时期，期间dischargev.释放，排除，放电impn.毫安,FilterCircuit,WordsandTerms,microfaradmaikrufrdn.微法kilohmkilumn.千欧foregoingf:guia.上述的chokecoiltukkiln.阻尼线圈,FilterCircuit,Text,Formanyapplications,asmoothdcoutputvoltagewiththeacrippleremovedisrequired.,许多应用系统需要一个去除交流脉动的光滑直流电压。,Circuitsusedremovedacvatiationsofrectifieddirectcuurentarefiltercircuits.,去除整流后直流电流中交流脉动的电路就称为滤波电路。,FilterCircuit,Text,TheoutputofarectifierhasadcvalueandacripplevalueasshowninFigure1.30.,如图1.3所示，整流器的输出包括直流成分和交流脉动成分。,FilterCircuit,Text,Togainarelativeindexoftheamountofacvariation,theripplefactoroftheoutputwaveformofarectifiercanbedeterminedby,为了获得整流器输出波形中交流变化量的相对大小，其脉动系数可表示为：,FilterCircuit,Text,Wherer=ripplefactor,Vr(rms)=rmsvalueoftheaccomponent,Vdc=averagevalueoftherectifieddcvoltage.,式中，r、Vr(rms)、Vdc分别表示纹波系数、交流部分的均方根值、整流后的直流电压平均值。,FilterCircuit,Text,Adifferentvalueoffiltercapacitorwouldresultinachangeintherateofdischarge.,滤波器的电容大小不一样会导致其放电率的变化。,IfCdischargedaverysmallamount,thevalueofVdcwouldbeclosertothevalueofVmax.,如果C放电量非常小，Vdc的值更接近Vmax。,FilterCircuit,Text,Withlightloads(highresistance),thecapacitorfilterwillsupplyahighdcvoltagewithlittleripple.,负载轻（大电阻）的电容滤波器能提供很小波动的高直流电压。,FilterCircuit,Text,However,withaheavy(lowresistance)loadconnected,thedcvoltagelevelwilldropduetoagreaterripple.,然而，若负载重（小电阻），较大脉动导致了直流电压的降低。,FilterCircuit,Text,Theincreasedrippleiscausedbythelowerresist-ancedischargepathforthefiltercapacitor.,增加的脉动是由和滤波电容形成放电通路的较小的电阻引起的。,TheeffectofaheavierloadonthefiltercapacitorisshowninFigure1.31(D).,电容滤波器带重负载的效果如图1.31(D)所示。,Direct-currentRegulation,WordsandTerms,regulation.regjuleinn.调节，调整ratedreitida.额定的zenerdiodedaiud稳压二极管breakdownvoltage击穿电压voltageregulation电压调节器,Direct-currentRegulation,WordsandTerms,oppositepzita.相对的，相应的，相反地shuntntn.分路、分流器innovation.inveinn.改革，革新fixedfiksta.固定的，不变的extraekstra.额外的，附加的,Direct-currentRegulation,WordsandTerms,representative.reprizenttiva.典型的，代表的short-circuitprotection短路保护thermal:mla.热的，由热造成的indestructible.indistrktbla.牢不可破的,Direct-currentRegulation,Text,Theconceptofvoltageregulationcanbeunderstoodbyreferingtotheformula,参照公式,可以最好地理解概念：电压调整。,Direct-currentRegulation,Text,whereVR=voltageregulationinpercent,VNL=no-loadterminalvoltage,andVFL=ratedfull-loadterminalvoltage,式中，VR、VNL、VFL分别表示百分比表示的电压调整、空载下的终止电压、额定负载下的终止电压,Direct-currentRegulation,Text,Outputvoltageiscomparedwithareferencevoltagebyahigh-gainerroramplifier.,Operationofthethree-terminalregulatorisbasedontheappliedinputvoltageanddevelopedoutputvoltage.,三端调整器的工作基于输入电压与输出电压。,高增益误差放大器将输入电压与参考电压进行比较。,Direct-currentRegulation,Text,Anydifferenceinvoltagewillbesensedbytheerroramplifier.,误差放大器感知两个电压的任何变化。,Theoutputoftheerroramplifierthencontrolsconductionoftheseries-passtransistor.,其输出控制串联三极管的传导。,Direct-currentRegulation,Text,Thistransistorrespondsasavariableresistor.,它和负载电流的变化相反，以维持其输出电压在一个恒定的值。,Itchangesinverselywiththeloadcurrenttomaintaintheoutputvoltageataconstantvalue.,该三极管在这里作为可变电阻使用。,Direct-currentRegulation,Text,Anincreaseinoutputvoltagewouldcauseacorres-pondingincreaseintheconductionoftheseries-passtransistor.,输出电压的增大会导致串联三极管传导的相应增加。,Direct-currentRegulation,Text,Thisinturnwouldcausemorevoltagedropacrosstheseriesresistor,whichwouldlowertheoutputvoltage.,相应地，降落在串联电阻上的电压会增大，从而降低输出电压。,Direct-currentRegulation,Text,Adecreaseinoutputvoltagewouldcauselessconductionofthepasstransistor.,输出电压的减小会导致串联三极管传导的相应降低.,Direct-currentRegulation,Text,Reducedcurrentthroughtheseriesresistorwillcauselessvoltagedrop.Theoutputvoltagewouldthereforeincreaseinvaluetocompensateforthedecreaseinvoltage.,减少的电流降低了串联电阻上的电压，因而提高了输出电压,PhaseControl,WordsandTerms,Sinewavesainweiv正弦波alter:ltv.改变，改动laglgv.滞后phasorfeizn.移相器，相位器，相位计anglegln.角single-legsigllegn.单相,PhaseControl,WordsandTerms,alternate:lt:nita.交替的，轮流的regardlessof不管，不顾,PhaseControl,Text,Shiftingthephaseofgate-cathodeacvoltagewithrespecttotheanode-cathodevoltagecanbeusedtocontroltheconductionofanSCR.,参照阳极电压，移动门极交流电压的相位可以控制SCR的导通。,PhaseControl,Text,Inphase-controlapplications,theshapeandamplitudeofthegatevoltageremainunchangedwhileitsphaseisshiftedwithrespecttotime.,在相位控制应用中，参照时间移动相位时门电压的形状、大小保持不变。,Capacitorsandinductorsarecommonlyusedtoachievethistypeofcontrol.,通常利用电容、电感实现这种控制。,PhaseControl,Text,PhaseshiftingofanacsinewaveusuallyinvolvesanLRoranLCcomponentcombination.,正弦交流波的相位移动经常包括LR或者LC组件。,Thesecomponentsareusedtoalterthecurrentandvoltagerelationshipofthecircuit.,利用这些组件改变电路的电流与电压之间的关系。,PhaseControl,Text,InanLRcombination,inductancecausesthecurrenttolagbehindthevoltagebyasmuchas90.,在LR组件中，电感上的电流滞后其电压90。,Alteringtheresistivecomponentofthiscombinationcausesatotalcircuitimpedance(Z)change,whichinturnproducesaphasechange.,改变该组件中的电阻会导致整个电路阻抗的变化，其相位相应地发生了变化。,PhaseControl,Text,AnRCnetwork,bycomparison,causesthecurrenttoleadthecoltagebyasmuchas90.,比较而言，RC网络中电容上的电流超前其电压90。,AdjustingthevalueofRinthistypeofcircuitchangesthetotalimpedance,whichinturncausesaphasechange.,调解R的大小从而改变整个阻抗，其相位相应地发生了变化。,PhaseControl,Text,Acommonwaytoshowthephaserelationshipofaccurrentandvoltageistorepresentthesevaluesbylinescalledphasor.,显示交流电中电流、电压相位关系的通用方法是用称为相图的线表示。,PhaseControl,Text,Thelinelengthofaphasorisusedtoshowitsvalue,whileitsdirectionisusedtoshowphaserelationships.,相图的线长代表了大小，方向代表了其相位关系。,UnijuncityTransistorPulseTriggering,WordsandTerms,photocellfutseln.光电管，光电池thermocouple:mu.kpln.温差电偶，热电偶ceramicsirmika.陶瓷的fusingfju:zin.熔断，熔融aluminumlju:minmn.铝arrowaun.箭头,UnijuncityTransistorPulseTriggering,WordsandTerms,slantsla:ntv.倾斜leakagecurrentli:kidkrnt漏电流curvek:vn.曲线，特性曲线valleyvoltage谷点电压oscillation.sileinn.振荡injectindektv.注入，射入,UnijuncityTransistorPulseTriggering,WordsandTerms,fractionalfrknla.部分的，分数的，小数的intrinsicintrinsika.内在的，本质的standoffratiostndfreiiun.（单结管内）分压比etai:tn.希腊字母H,UnijuncityTransistorPulseTriggering,WordsandTerms,slightlyad.轻微地，稍微relaxationoscillator.ri:lkseinsileit驰张振荡sawtoothwaves:tu:weiv锯齿波spikedpulsespaikedpls尖峰脉冲,UnijuncityTransistorPulseTriggering,Text,PulsetriggeringofanSCRcanbeaccomplishiedwithaunijunctiontransistororUJT.,SCR的脉冲触发可借助于单结晶体管（unijunctiontransistor,UJT）实现。,Thisdeviceiscommonlydescribedasavoltage-controlleddiode.,这种设备通常称为电压控制二极管。,UnijuncityTransistorPulseTriggering,Text,WhenusedtotriggeranSCRintoconduction,UJTscanbedesignedtorespondtolow-levelsignalsfromotherinputs.,触发SCR时，UJTs常用来响应来自于其它输入端的低级别信号。,UnijuncityTransistorPulseTriggering,Text,Theoutputofphotocells,thermocouples,andothertransducerscanbeusedtoenergizetheinputofaUJT,whichinturnwilltriggertheconductionofanSCR.,光电管、热电偶以及其它变换器的输出可激活UJT的输入，相应地触发SCR，让其处于导通状态。,UnijuncityTransistorPulseTriggering,Text,Throughthistypeofcircuitry,itispossibletocontrolalargeSCRcurrentwithanextremelysma