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ID:40476956
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页数:14页
时间:2019-08-03
《Transformerless Power Supplies - Resistive and Capacitive》由会员上传分享,免费在线阅读,更多相关内容在学术论文-天天文库。
1、AN954TransformerlessPowerSupplies:ResistiveandCapacitiveAuthor:RestonConditMicrochipTechnologyInc.INTRODUCTIONThereareseveralwaystoconvertanACvoltageatawallreceptacleintotheDCvoltagerequiredbyamicrocontroller.Traditionally,thishasbeendonewithatransformerandre
2、ctifiercircuit.Therearealsoswitch-ingpowersupplysolutions,however,inapplicationsthatinvolveprovidingaDCvoltagetoonlythemicrocontrollerandafewotherlow-currentdevices,transformer-basedorswitcher-basedpowersuppliesmaynotbecosteffective.Thereasonisthatthetransfor
3、mersintransformer-basedsolutions,andtheinductor/MOSFET/controllerinswitch-basedsolutions,areexpensiveandtakeupaconsiderableamountofspace.Thisisespeciallytrueintheappliancemarket,wherethecostandsizeofthecomponentssurroundingthepowersupplymaybesignificantlyless
4、thanthecostofthepowersupplyalone.Transformerlesspowersuppliesprovidealow-costalternativetotransformer-basedandswitcher-basedpowersupplies.Thetwobasictypesoftransformerlesspowersuppliesareresistiveandcapacitive.Thisapplicationnotewilldiscussbothwithafocusonthe
5、following:1.Acircuitanalysisofthesupply.2.Theadvantagesanddisadvantagesofeachpowersupply.3.Additionalconsiderationsincludingsafetyrequirementsandtrade-offsassociatedwithhalf-bridgeversusfull-bridgerectification.Warning:Anelectrocutionhazardexistsduringexperim
6、entationwithtransformerlesscircuitsthatinterfacetowallpower.Thereisnotransformerforpower-lineisolationinthefollowingcircuits,sotheusermustbeverycarefulandassesstherisksfromline-transientsintheuser’sapplication.Anisolationtransformershouldbeusedwhenprobingthef
7、ollowingcircuits.2004MicrochipTechnologyInc.DS00954A-page1AN954CAPACITIVETRANSFORMERLESSPOWERSUPPLYAcapacitivetransformerlesspowersupplyisshowninFigure1.Thevoltageattheloadwillremainconstantsolongascurrentout(IOUT)islessthanorequaltocurrentin(IIN).IINislimit
8、edbyR1andthereactanceofC1.Note:R1limitsinrushcurrent.ThevalueofR1ischosensothatitdoesnotdissipatetoomuchpower,yetislargeenoughtolimitinrushcurrent.FIGURE1:CAPACITIVEPOWERSUPPLYLVOUTIIND1I
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