直接开关电源的外文文献翻译.docx

直接开关电源的外文文献翻译.docx

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直接开关电源的外文文献翻译

DCswitchingpowersupplyforprotectiontechnology

Abstract:

TheDCswitchingpowersupplyprotectionsystem,protectionsystemdesignprinciplesputforwardandthewholeprotectivemeasures,analysisoftheswitchingpowersupplyofthevariousprotectionfeaturesanddesign,introducesseveralpracticalprotectionCircuit.

Keywords:

switchingpowersupply;protectioncircuit;SystemDesign

1Introduction

DCswitchingregulatorforuseinthemoreexpensivehigh-powerswitchingdevices,thecontrolcircuitisalsomorecomplex,Inaddition,theloadswitchingregulatorsaregenerallylevelwithalargenumberofhighlyintegratedelectronicsystemsinstalledonthedevice.Powertransistorsandintegrateddevicetolerance,poorthermalshocks.Thustheprotectionswitchingregulatorshouldtakeintoaccounttheregulatoritselfandloadsecurity.Manydifferenttypesofcircuitprotection,polarityprotectiondescribedhere,programprotection,overcurrentprotection,overvoltage,undervoltageprotectionandthermalprotectioncircuits.Someprotectionisusuallychosentobecombinedtoformacomprehensiveprotectionsystem.

2polarityprotection

DCswitchingregulatorsaregenerallyunregulatedinputDCpowersupply.Duetooperationerrorsorunexpectedcircumstanceswillthewrongpolaritywilldamagetheswitchingpowersupply.Polarityprotectionpurposes,istomaketheswitchingregulatoronlywhenthecorrectpolarityconnectedtotheunregulatedDCpowertowork.Usingasingledevicecanbeachievedthroughthewizardpowerpolarityprotection.SimplepolarityprotectioncircuitshowninFigure1.ToflowthroughthediodeDswitchingregulator'sinputtotalcurrent,sothiscircuitisusedinlowpowerswitchingregulatoronthemoreappropriate.Inthehighpoweroftheoccasion,putthepolarityprotectioncircuitasapartoftheprotectionprogram,cansavethepowerrequiredforpolarityprotectiondiode,powerconsumptionwillbereduced.Forconvenientoperation,easytoidentifythepolarityiscorrectornot,thediodeinFigure1,thereceivedlight.

3programprotection

Switchingpowersupplycircuitismorecomplex,basicallycanbedividedintolow-powercontrolsectionandpowerswitchpart.Switchingtransistorsarehighpower,toprotecttheswitchingtransistoristurnedonoroffthepowerwhenthesecuritymustletmodulators,amplifiersandothersmallpowercontrolcircuit.Tothisend,toensurethatthecorrectbootprocess.Theinputofswitchingregulatortypicallytakeasmallinductanceandlargecapacitanceoftheinputfilter.Momentintheboot,willflowthroughalargefiltercapacitorinrushcurrent,theinrushcurrentcanbeseveraltimesthenormalinputcurrent.Makesuchalargesurgecurrentordinarypowerswitchcontactsorrelaycontactmelting,andtoenterthefuseblows.Inaddition,theinrushcurrentcanalsodamagethecapacitor,sothatshortenedlifeexpectancy,prematuredamage.Tothisend,thebootshouldbeaccesstoalimitingresistor,throughthecurrentlimitingresistortochargethecapacitor.Inordernottoconsumetoomuchofthecurrentlimitingresistorpower,whichaffectsthenormaloperationofswitchingregulators,power-transientprocessintheend,witharelayautomaticallypickitshortsoDCpowerdirectlytotheswitchingregulatorPowersupply,showninFigure2.Suchthattheswitchingregulatorcircuittermeda"softstart"circuit.

Switchingregulatorcontrolcircuitlogiccomponentsorop-ampauxiliarypowersupplyrequired.Tothisend,theauxiliarypowersupplymustbeintheswitchcircuit.Thiscontrolcircuitcanbeusedtoensurethatthebootprocess.Normalbootprocessare:

identificationofthepolarityoftheinputpower,voltageprotection→boot→auxiliarypowersupplycircuitandthroughthecurrentlimitingresistorRoftheswitchingregulatorinputcapacitorCcharging→modulationswitchingregulatorcircuit,→shortcircuitlimitingresistorswitchingregulatorstability.

Intheswitchingregulator,thejust-machine,becausetheoutputcapacitorcapacity,ratedoutputvoltagechargetotakesometime.Duringthistime,thesamplingamplifierinputlowoutputvoltagesampling,closed-loopregulationcharacteristicsofthesystemwillforcetheswitchingtransistorconductiontimelonger,thisway,theswitchingtransistorduringthisperiodwilltendtocontinuousconductionAndeasilydamaged.Todothis,startthisperiodoftimerequired,theswitchingmodulationcircuitoutputtotheswitchingtransistorbasedrivesignalpulse-widthmodulation,toensuretheswitchtransistorgraduallybecomenormalbytheendoftheswitchstate,andthereforeshouldbeprotectedtomeettheadditionalpowerofsoftStart.

4over-currentprotection

Whentheloadshort-circuit,overload,orunforeseencircumstancessuchasthefailurecontrolcircuits,willcauseflowthroughtheregulatorintheswitchingtransistorcurrentistoolarge,thepipeincreasespowerconsumption,heat,ifthereisnoover-currentprotectiondevices,powerswitchingtransistorTheremaybedamaged.Thereforetheswitchingregulatorintheover-currentprotectioniscommonlyused.Themosteconomicandsimplemethodistofuse.Heatcapacityofthetransistorissmall,generallycannotplaynormalfuseprotection,commonlyusedisfastfuse.Thisapproachhastheadvantageofprotectioniseasy,however,needtoswitchtransistoraccordingtothespecificrequirementsofthesafetyoftheworkareatoselectthefusespecifications.Thisdisadvantageisover-currentprotectionmeasurestobringtheinconvenienceoffrequentlyreplacingthefuse.

Commonlyusedlinearregulatorcurrentlimitprotectionandcurrentendprotectionswitchingregulatorcanapply.However,accordingtothecharacteristicsofswitchingregulators,suchprotectioncannotdirectlycontroltheoutputofthecircuitswitchingtransistor,sothatover-currentprotectionmustbeconvertedtoapulseoutputinstructiontocontrolthemodulatortoprotecttheswitchingtransistor.Inordertoachieveover-currentprotectiongenerallyneedtousesamplingresistorinseriesinthecircuit,thiswillaffecttheefficiencyofpowersupply,somuchforlowpowerswitchingregulatorofoccasions.Inthehigh-powerswitchingpowersupply,takingintoaccountpowerconsumption,shouldtrytoavoidaccesstothesamplingresistor.Therefore,over-currentprotectionusuallyconvertover,undervoltageprotection.

5over-voltageprotection

Switchingregulator'sinputover-voltageprotection,includingover-voltageprotectionandoutputover-voltageprotection.SwitchingregulatorisnotusedbytheregulatedDCpowersupplysuchasbatteriesandrectifierifthevoltageistoohigh,theswitchingregulatorisnotworkingproperly,orevendamagetotheinternaldevice,therefore,necessarytousetheinputover-voltageprotectioncircuit.FormedbytransistorsandrelaysprotectioncircuitshowninFigure3.

Inthiscircuit,whentheinputDCpowervoltageishigherthanthediodebreakdownvoltageregulator,theregulatorofthebreakdown,acurrentflowsthroughtheresistorR,Vturnsonthetransistor,relay,normallyclosedcontactsbreakOpen,cutofftheinput.InwhichthevalueofsteadypressureregulatortubeVz=ESrmax-UBE.Inputpowersupplypolarityprotectioncircuitwiththecombinationoftheinputover-voltageprotection,polarityprotectionformidentificationandover-voltageprotectioncircuit.

Outputovervoltageprotectioninaswitchingpowersupplyiscrucial.Particularoutputis5V,switchingregulators,itloadsalargenumberofhighlyintegratedlogicdevices.Ifyouwork,theswitchingtransistorswitchingregulatorsuddenlydamage,theoutputpotentialtobeimmediatelyincreasedtotheunregulatedDCinputvoltagevalue,instantaneouscausegreatlosses.Commonlyusedmethodisthyristorshortcircuitprotection.Simpleover-voltageprotectioncircuitshowninFigure4.Whentheoutputvoltageistoohigh,theregulatoristhebreakdown,triggeredthyristor,theoutputshort-circuit,resultinginover-current,throughthefuseorcircuitprotectiondevicewillenterthecut,protectingtheload.Thiscircuitisequivalenttotheresponsetimeoftheopeningtimeofthyristorisabout5~10μs.Thedisadvantageisthatoperationvoltageisfixed,thetemperaturecoefficient,theactionpointofinstability.Inaddition,theregulatortherearediscreteparameters,thesamemodelbuttheover-voltagestartvalueisdifferent,makesitdifficulttodebug.Figure5istheimprovedcircuit.InwhichR1,R2isasamplingcircuit,Vzisthereferencevoltage.

Escsuddenincreaseintheoutputvoltage,thetransistorV1,V2conducting,thyristorconduction.ReferencevoltageVzbythetypeTodetermine,UBE1fortheV1oftheemitter（BE）voltagedrop.Operationvoltageofthecircuitvariable,andtheactionpointoffairlystable.Whentheregulatorto7V,itstemperaturecoefficientoftheemitterandthetransistorV1（BE）canoffsetvoltagetemperaturecoefficient,temperaturecoefficientcandropverylow.Buttheoutputis5~5.5VDCswitchingregulators,itsusualoperationvoltageis5.5~6V.Thentheregulatorwillbeinthe3.5Vvoltagebelowthevoltageregulatornearthetemperaturechangecoefficientis-20~-30mV/℃.Therefore,largetemperatureprotectioncircuitwillbetheoccasionmalfunction.Usedtodetectthevoltagecomparatorintegratedcircuitswitchingregulatoroutputvoltage,ismorecommonlyusedmethods,theuseofthecomparatoroutputchangesstatematchwiththecorrespondinglogic,constituteover-voltageprotectioncircuit,thiscircuitisbothsensitiveandStability.

6under-voltageprotection

Outputvoltagebelowthespecifiedvalue,refl