开关电源的软启动控制器

Thistechnicalbriefdescribesamicrocontrollerbased

Soft-StartControllercircuitforaswitchingpowersupply.

Start-upisastressfultimeforthepowerdriversectionof

aswitchingpowersupply.Becausetheoutputvoltageis

initiallyzero,thefeedbackerrorinitiallyjumpstoitsmaxi-

mum.Thelargefeedbackerrorthendrivestheloopfilter

toitslimit,whichdrivesthepowerswitchingtransistorsin

thedriversectionofthepowersupplyattheirmaximum

rating.Thisconditioncontinuesuntiltheoutputvoltageof

thepowersupplyapproachesitsnominalvalue.

Iftheloadbeingdrivenbythepowersupplyiscapacitive,

theproblemisexaggeratedduetothelargetransient

currentsrequiredtochargethecapacitiveload.In

extremeinstances,therepeatedhighstressofstart-up

canresultincatastrophicfailuresinthedriversection,

typically,thepowerMOSFETtransistorsorthepower

rectifiers.TB081Soft-StartControllerForSwitchingPowerSuppliesAuthors:JohnDayIMPLEMENTATIONKeithCurtisMicrochipTechnologyInc.HardwareOVERVIEWThehardwareforthesoft-startcircuitconsistsofthreecomponents;aPIC10F200microcontroller,a0.1uFThistechnicalbriefdescribesamicrocontrollerbasedcapacitoranda10kpull-downresistor.TherampingSoft-StartControllercircuitforaswitchingpowersupply.PWMfunctionisimplementede