AN-1849An Audio Amplifier Power Supply Design

1 ApplicationReportSNAA057B June2008 powersupplyforusewithournewestofferingof high-performance, ,Primariesin ,Primariesin June2008 RevisedMay2013AN-1849 AnAudioAmplifierPowerSupplyDesignSubmitD ocumentationFeedbackCopyright 2008 2013, :Switchmode(SMPS),regulated, ,common,inexpensive, a drawbacktoSMPSis ,namelyClassG andClassH, regulatedsupplycanbea simplelinearregulatorICwiththerectifiedv oltagefromthetransformerasinputanda ,cost,space,thermaldesign, is , ,goodperformance,andreasonablecost,anunr egulatedsupplyis transformer,a bridgerectifier, drawbacktotheunregulatedsupplyis designshouldallowfora minimum10% fusein , theresponsibilityofthereadertoperformsta ndardindustrytestingtoassuresafetywhenus ingthesolutionin partorin wholein ,writtenorimplied, 72 Vunregulatedpowersupplydesignedspecifica llyfortheLME49810, and350 Wto400 Winto4.

2 Completedocumentationfortheamplifiermodu lescanbefoundin theLME49830 TBUltra-HighFidelityHighPowerAmplifierRe ferenceDesign(SNAA058).Althoughthepowers upplydesignis ,a fullyintegratedbridge,andvariousrailcapa citorsforripplevoltagereduction,noisesup pression, completeschematic,PCBviews, June2008 RevisedMay2013 SubmitDocumentationFeedbackCopyright 2008 2013, thebasicpowersupplyconsistingofthetransf ormers,thebridge, nota commercialdesignwheretightcostconstraint smustbetakenintoaccount, commercialdesign,benchandlisteningtestor someothertestcriteriaisrecommendedtodete rminetheexactnumber,size, shortexplanationofthepurposeofeachcapaci torattheprimarysideofthetransformers, C1, C2, C4 notusedandis redundant. CS1, CS2arelowvalue,ceramiccapacitorstofilter higherfrequencynoiserightattheDCoutputof thediodebridge.

3 CS3, ,000 F capacitanceperrail. CS5, CS7, CS8actin conjunctionwithRS1andRS2todecouplethelar geelectrolyticcapacitorsandreduceimpedan ce. CS9, CS10arelowvalue,ceramiccapacitorstofilte rhigherfrequencynoisefromthetransformers econdaryAClinesatthediodebridge. CS11- CS14arein ,thesupplyrailshavebleederresistors,RBL1 , RBL2, todrainthelargereservoircapacitors(CS3,C S4). forrobustnessin June2008 RevisedMay2013AN-1849 AnAudioAmplifierPowerSupplyDesignSubmitD ocumentationFeedbackCopyright 2008 2013, ,metalizedC1,C2, F10%polyesterfilm, ,X7 RCS1,CS2,CS7, F10%type,200milleadAVXC orporationSR211C104 KARCS8,CS9,CS10,spacing250V,metalizedCS1 1,CS12,CS13, F10%polyesterfilm, ,CS3B,100 VelectrolyticCDEC ornellDCMC203U100BC220,000 F20%CS4A,CS4 BcanDubilierB100V,metalizedCS5A,CS5B,1 F10%polyesterfilm,PanasonicECQ-E1105 KFCS6A,CS6B10mmleadspacing4AN-1849 AnAudioAmplifierPowerSupplyDesignSNAA057 B June2008 RevisedMay2013 SubmitDocumentationFeedbackCopyright 2008 2013, (continued)

4 ReferenceValueToleranceDescriptionManufa cturerPartNumber63 VelectrolyticCSR1,CSR21 F20%radial,2mmleadPanasonicEEU-EB1J1R0 SspacingVishayD11A400 Vdiode,DO-411N4004-E3/54 Semiconductor2 WZenerdiode,MicrosemiDZ151V5%2EZ51D5DO41 DO-41 Corporation2 WZenerdiode,MicrosemiDZ243V5% ,DO-35 RBLD1,RBLD2,InternationalYageo2k 5%5 WmetaloxideSQP500JB-2K0 RBLD3, 5%5 WmetaloxideSQP500JB-1K2 Corporation5 WwirewoundHuntingtonElectric,RIR1,RIR2,R IR368 1%ALSR-5-68-1% ,RS21 5% WattcarbonfilmPanasonicERD-S2TJ1R0 VInternationalYageoRG100 1% WattmetalfilmMFR-25 FBF-100 RCorporation1 WattmetaloxideRZ1560 5%PanasonicERG-1SJ561filmRZ2390 5% WattcarbonfilmPanasonicERD-S1TJ391 VRPD10k 5% WattcarbonfilmPanasonicERD-S2TJ103V48V,4 00mWSPST, ,relayWorksFairchildU135A700 VbridgerectifierGBPC3510 WSemiconductorDPDTPCB mount,S16AC&K Components1201M2S1 CQE2minislideswitch3 pin156milMolex/WaldomJ1,J5header,rightan gle, pin156milMolex/WaldomJ2,J9,J4A,J4 Bheader,rightangle, pin156milMolex/WaldomJ3A,J3 Bheader,rightangle, pin100milJ7,J8,J11,J12,Molex/Waldomheade r,rightangle,22-05-3021J13,J14, ,dualTransformer1,Plitron24V,300 VAsecondary, stickheatsinkforbridge,CTSE lectronic CA= C/WBDN12-5 " square, "Components,InctallRZ3,RZ4,DZ3,Optionunu sedDZ4,CSF1,CSF2,circuitsCSF35 SNAA057B June2008 RevisedMay2013AN-1849 AnAudioAmplifierPowerSupplyDesignSubmitD ocumentationFeedbackCopyright 2008 2013, switchis connectedin ,Figure2 andFigure3.

5 PrimariesinSeries6AN-1849 AnAudioAmplifierPowerSupplyDesignSNAA057 B June2008 RevisedMay2013 SubmitDocumentationFeedbackCopyright 2008 2013, simpleinrushcircuitis shownin /5 Wresistors(RIR1- RIR3, labeledjustRIRin Figure1 andFigure4)in parallel,a poweredfora verysimpleanddoesnotlimitinrushcurrentif themainspoweris fortherelaycoilEMFandCSR2is Figure5 showshowthepositiverailchargesupwiththei ncreasein chargerateoncetherelayis June2008 RevisedMay2013AN-1849 AnAudioAmplifierPowerSupplyDesignSubmitD ocumentationFeedbackCopyright 2008 2013, usedfora heldin Mutemodeuntilthevoltagesuppliesarenearly stableandalsogoesintoMutemodeoncethesupp lieshavecollapsedbelowa ,000 F shownin setbythevalueoftheDZ1 Zenerdiode, ' TheLED'sforwardvoltage(typically2V~ 4V)

6 Is usedastheamplifier' 'sforwardvoltageis alsousedasanindicator,lightingwhentheamp lifieris in ,theforwardvoltageoftheLEDwillcollapsequ icklyputtingtheamplifierintoMutemodewell beforethesuppliesaredischargedfora additionaldelayfromwhentheMutesignalreac hestheMutethreshold(~ )andwhentheamplifierentersPLAY modeasa June2008 RevisedMay2013 SubmitDocumentationFeedbackCopyright 2008 2013, forprotectionin theeventofLEDfailurelockingtheMutevoltag esoit 'sMuteresistoris sizedfora neededsoDZ1willconductandCSR1is fora shortcomingofthesimpleMutecontrolcircuit is theLED'sbrightnesswillvaryunderheavyampl ifierloadwiththecircuitvaluesshownin Figure6. EitherthethresholdoftheMutecircuitcanbel oweredbychangingthevalueofDZ1formorecons istentbrightnessin operationora showsa basicconstantcurrent(LEDbrightness) June2008 RevisedMay2013AN-1849 AnAudioAmplifierPowerSupplyDesignSubmitD ocumentationFeedbackCopyright 2008 2013, , DZB, usedtobiasQLED andlimitcurrentthroughDZC.

7 Byusinga 10 VZenerdiode(DZB) thepowerdissipationin QLEDis keptverylowsothata thattheDZAZ enerdiodeis doesnotgivebothconstantLEDcurrentandtheM utesignalcontrolasFigure6, althoughtheMutecontrolcouldbetakenatthee mitterofQLED. AnalternatecircuittocombinebothFigure6 andFigure9 is June2008 RevisedMay2013 SubmitDocumentationFeedbackCopyright 2008 2013, Figure10willhavethesamethresholdvoltages asin Figure9 andsimilarMutecontrolthresholdsasin Figure6 reducedsupplyvoltagewindowfromLEDfirstli ghttoconstantbrightness,DZAshouldbeincre asedwhileDZBis 70 Vto 73 Vsupplyunderquiescentconditionswithfulll oadvoltagedroppingto 59 Vto June2008 RevisedMay2013AN-1849 AnAudioAmplifierPowerSupplyDesignSubmitD ocumentationFeedbackCopyright 2008 2013, June2008 RevisedMay2013 SubmitDocumentationFeedbackCopyright 2008 2013, June2008 RevisedMay2013AN-1849 AnAudioAmplifierPowerSupplyDesignSubmitD ocumentationFeedbackCopyright 2008 2013.

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