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ID:39794547
大小:1.07 MB
页数:16页
时间:2019-07-11
《CHAPTER 4 The Components of the System 7. Power Supply》由会员上传分享,免费在线阅读,更多相关内容在教育资源-天天文库。
1、CHAPTER4TheComponentsoftheSystemUnitPowerSupplyApresentationofeSyst.orgPowerSupplyAllelectroniccircuitsneedapowersourcetowork.Forelectroniccircuitsmadeupoftransistorsand/orICs,thispowersourcemustbeaDCvoltageofaspecificvalue.AbatteryisacommonDCvoltagesourceforsometypesofelectronicequipmentespe
2、ciallyportableslikecellphonesandiPods.Mostnon-portableequipmentusespowersuppliesthatoperatefromtheACpowerlinebutproduceoneormoreDCoutputs.PowerSupplyCharacteristicsTheinputisthe120volt60HzACpowerline.Alternately,theinputmaybe240voltAC.ThepowersupplyconvertstheACintoDCandprovidesoneormoreDCout
3、putvoltages.Somemodernelectroniccircuitsneedtwoormoredifferentvoltages.Commonvoltagesare48,24,15,12,9,5,3.3,2.5,1.8,1.5,1.2and1volts.AgoodexampleofamodernpowersupplyistheoneinsideaPCthatfurnishes12,5,3.3and1.2volts.ComponentsofaPowerSupplyMaincircuitsinmostpowersupplies.PowerSupplyTheAClineis
4、firstpassedthroughalowpassfilteroftheformshowninfigure.ThiseliminatesnoiseontheAClinefrombotheringthepowersupplycircuitsandpreventsunwantedsignalsfromthepowersupplyfrombeingtransferredbackintotheAClinewheretheymightinterferewithotherequipment.TransformerAtransformeriscommonlyusedtosteptheinpu
5、tACvoltageleveldownorup.MostelectroniccircuitsoperatefromvoltageslowerthantheAClinevoltagesothetransformernormallystepsthevoltagedownbyitsturnsratiotoadesiredlowerlevel.Forexample,atransformerwithaturnsratioof10to1wouldconvertthe120volt60Hzinputsinewaveintoa12voltsinewave.RectifierTherectifie
6、rconvertstheACsinewaveintoapulsatingDCwave.Thereareseveralformsofrectifiersusedbutallaremadeupofdiodes.Rectifiertypesandoperationwillbecoveredlater.FilterTherectifierproducesaDCoutputbutitispulsatingratherthanaconstantsteadyvalueovertimelikethatfromabattery.Afilterisusedtoremovethepulsationsa
7、ndcreateaconstantoutput.Themostcommonfilterisalargecapacitor.RegulatorTheregulatorisacircuitthathelpsmaintainafixedorconstantoutputvoltage.ChangesintheloadortheAClinevoltagewillcausetheoutputvoltagetovary.Mostelectroniccircuitscannotwithstand
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