开关电源闭环控制电路的设计分析

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1、DesigningStableControlLoopsByDanMitchellandBobMammanoABSTRACTTheobjectiveofthistopicistoprovidethedesignerwithapracticalreviewofloopcompensationtechniquesappliedtoswitchingpowersupplyfeedbackcontrol.Atop-downsystemapproachistakenstartingwithbasicfeedbackcontr

2、olconceptsandleadingtostep-by-stepdesignprocedures,initiallyappliedtoasimplebuckregulatorandthenexpandedtoothertopologiesandcontrolalgorithms.SampledesignsaredemonstratedwithMathcadsimulationstoillustrategainandphasemarginsandtheirimpactonperformanceanalysis.

3、I.INTRODUCTIONStabletInsuringstabilityofaproposedpowersupplyPerturbationSystemsolutionisoftenoneofthemorechallengingResponseaspectsofthedesignprocess.NothingismoredisconcertingthantohaveyourlovinglycraftedbreadboardbreakintowildoscillationsjustasitUnstabletis

4、beingdemonstratedtothebossorcustomer,SystemPerturbationbutinsuringagainstthisunfortunateeventtakesResponsesomeanalysiswhichmanydesignersviewasformidable.PathstakenbydesignengineersoftenFig.1.Definitionofstability.emphasizeeithercut-and-tryempiricaltestinginAn

5、otherwayofvisualizingstabilityisshownthelaboratoryorcomputersimulationslookinginFig.2.Whilethisgraphicallyillustratesthefornumericalsolutionsbasedoncomplexconceptofsystemstability,italsopointsoutthatmathematicalmodels.Whilebothofthesewemustmakeafurtherdistinc

6、tionbetweenapproacheshaveaplaceincircuitdesign,abasiclarge-signalandsmall-signalstability.Whileunderstandingoffeedbacktheorywillusuallysmall-signalstabilityisanimportantandallowthedefinitionofanacceptablenecessarycriterion,asystemcouldsatisfythiscompensationn

7、etworkwithaminimumofrequirementandyetstillbecomeunstablewithacomputationaleffort.large-signalperturbation.ItisimportantthatdesignersrememberthatallthegainandphaseII.STABILITYDEFINEDcalculationswemightperformareonlytoinsureFig.1givesaquickillustrationofatleast

8、onesmall-signalstability.Thesecalculationsaredefinitionofstability.Initssimplestterms,abasedupon–andonlyapplicableto-linearsystemisstableif,whensubjectedtoasystems,andaswitchingregulatori