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基于数字控制方式的DC-DC转换器系统设计.docx

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基于数字控制方式的DC-DC转换器系统设计 Introduction Inrecentyears,theuseofdigitalcontrolinpowerelectronicssystemshasbecomeincreasinglypopularduetoitsflexibility,accuracyandreliability.Inthispaper,wewilldiscussthedesignofaDC-DCconvertersystemwhichisbasedondigitalcontrol.Wewillprovideanoverviewofthesystem,discussthedesignconsiderations,andshowthesimulationresults. OverviewoftheDC-DCConverterSystem TheDC-DCconvertersystemconsistsoftwomaincomponents:thepowerstageandthedigitalcontrolcircuitry.ThepowerstageconvertstheinputDCvoltagetothedesiredoutputvoltage,whilethedigitalcontrolcircuitrycontrolsthepowerstagetoregulatetheoutputvoltageandmaintainthedesiredefficiency. Thepowerstagetypicallyconsistsofaninductor,acapacitor,andapairofswitchingdevices(suchasMOSFETs).Theinductorstorestheenergyduringthefirsthalf-cycleoftheswitchingperiodandreleasesitduringthesecondhalf-cycletomaintainthedesiredoutputvoltage.Thecapacitorfilterstheoutputvoltagetoremoveanyhigh-frequencynoiseorripple.Theswitchingdevicesarecontrolledbythedigitalcontrolcircuitrytoswitchonandoffatappropriatetimestoregulatetheoutputvoltage. DesignConsiderations WhendesigningadigitalcontrolsystemforaDC-DCconverter,thereareseveralfactorstoconsider: 1.Controlalgorithm: Thecontrolalgorithmusedinthedigitalcontrolsystemdetermineshowthesystemwillrespondtochangesintheinputvoltage,outputvoltage,andload.TwocommoncontrolalgorithmsarePulseWidthModulation(PWM)andConstantOn-Time(COT). PWMisadigitalcontroltechniquethatvariesthedutycycleoftheswitchingdevicetoregulatetheoutputvoltage.Thedutycycleisproportionatetotheoutputvoltageandinverselyproportionatetotheinputvoltage.COTisadigitalcontroltechniquethatvariestheswitchingperiodinsteadofthedutycycle.Theswitchingperiodisinverselyproportionaltotheoutputvoltageanddirectlyproportionaltotheinputvoltage. 2.Samplingfrequency: Thesamplingfrequencyusedinthedigitalcontrolsystemdetermineshowoftenthesystemwillmeasuretheinputandoutputvoltagesandadjusttheswitchingdevices.Thesamplingfrequencymustbehighenoughtocaptureanyhi