overloadlamp

TDK-EPChasjoinedSTMicroelectronicstodevelopareferencedesignforLEDlampballastsforuseinstreetlighting.
TDK-EPCoffersallitskeyelectroniccomponentssuchascapacitors,varistorsandinductors.
Thepowersupplyhasanoutputof130Watanoutputvoltageof48V.
LEDsareknownfortheirhighefficiencyandlongoperatinglife.
Thismakesthemincreasinglypopularforlightingtechnology,wheretheyareconsideredtobeinnovationdrivers.
Thereason:theymakeadecisivecontributiontoreducingtheenergyconsumptionoflampsforindoorandoutdooruse.
Thisappliesespeciallytostreetlighting,whereefficiency,operatinglife,maintenanceandenergyconsumptionplayakeyroleinreducingoverallcosts.
Inordertoensuremaintenance-freeoperation,thecorrespondingballastforanLEDlampmustbejustasefficientandhaveasimilarlylongoperatinglifeastheLEDsthemselves.
Two-stagereferencedesignThenewreferencedesigndevelopedbyTDK-EPCandSTMicroelectronics(Figure1)consistsoftwostages:afront-endpowerfactorcorrection(PFC)stagewiththeL6562ATcontrollerfromSTMicroelectronicsandanLLCresonantconverterbasedontheL6599ATpowerIC.
Thekeypropertiesofthedesignincludeaveryhighefficiencyofover90percent,abroadrangeofinputvoltage,i.
e.
anAClinevoltageofbetween85and305V,aswellashighreliabilityandalongoperatinglife.
Asthereliabilityormeantimebetweenfailures(MTBF)ofpowersuppliesdependsonthefailurerateoftheelectrolyticcapacitorsused,thisreferencedesigntakesaninnovativeapproach:itmakesexclusiveuseoffilmcapacitorsinsteadofelectrolyticonesforsmoothingandstorageintheDClinkcircuit.
Thedevelopershavealsoconsideredthederatingofthecomponents,thusreducingtheirloadinlinewithRecommendationMIL-HDBK-217D.
WiththeuseofthenewL6562ATandL6599ATICsfromSTMicroelectronics,thenumberofactivecomponentswasalsominimized,thusincreasingtheMTBFandsimultaneouslyoptimizingthetotalcostofthecomponents.
Thankstothehighefficiencyofthecircuit,thePFCstageneedsonlyasmallheatsink.
Thereferencedesignisadditionallyprotectedagainstoverloadandshortcircuit,open-circuitoperationateverystageandovervoltagesattheinput.
Thesystemautomaticallyrestartsafterafault.
ReferencedesignsMarch2011LampballastforLEDstreetlightingFigure1:Mainboardwithrectifier,PFCstageandresonantconverterTheuseoffilmcapacitorsassuresveryhighreliabilityandalongoperatinglife.
Applications&Cases1/EPCOSAG·ATDKGroupCompany·Edition2015·www.
epcos.
comKeypropertiesExtendedEuropeanACinputvoltagerangeof85to305Vatafrequencyof45to55HzOutputvoltageof48Vat2.
7ALongoperatinglifethankstoEPCOSfilmcapacitorsPowerharmonicstoEN61000-3-2ClassCEfficiencyatnominalloadofover90percentElectromagneticcompatibilitytoEN55022ClassB,EN55015Safety:doubleinsulationtoEN60950,SELVStage1:PFCcircuitThePFCstage,whichoperatesintransitionmode,actsasaprecontrollertosupplyenergytotheresonancestageat450V.
ThePFCpowerstageisaconventionalboostconverterconnectedtotheoutputoftherectifierbridge.
Italsoincludestheboostinductor,rectifierdiodeandoutputcapacitors.
ThePFCoutputcapacitorsareEPCOSfilmcapacitorsof5F/800V.
AMOSFETactsastheboostswitch.
TheboardisequippedwithaninputEMCfilterthatextractstheinterferencecausedbythebooststage.
ThepowerfactorcorrectionisperformedbytheL6562ATcontroller,asmallandlow-costcomponentthatoperatesoverthewidetemperaturerangerequiredforexternalapplications.
Stage2:ResonantconverterTheL6599ATcontrollerperformstheactivefunctioninthebuckconverter.
Itcomprisesallthefunctionsrequiredforthecorrectregulationoftheresonantconverter.
Ithasaconstantdutycycleof50percentandusesthefrequencyasthecontrolparameter.
Anintegratedmagneticapproachwithaseriesinductorisusedinthetransformer,thusobviatinganexternalinductorforgeneratingtheresonance.
ThechoiceforthesecondarywindingwasatransformerconfigurationwithcentertappingandSchottkypowerrectifiersofSTPS10150CGtype.
EPCOSfilmcapacitorswitharatingof4.
7F/63Varealsousedhereforsmoothing.
AsmallLCfilterthatsuppressestheRFripplecompletestheoutputpart.
Theoutputvoltageisregulatedandstabilizedviaafeedbacknetwork.
Figure2showsthecompletecircuitdiagramofthepowersupply,andthematerialsarelistedinTable1.
Figure2:CompletecircuitdiagramoftheLEDpowersupplyApplications&Cases2/EPCOSAG·ATDKGroupCompany·Edition2015·www.
epcos.
comTable1:MateriallistofTDK-EPCproductsEfficiencymeasurementTable2showstheoverallefficiencydeterminedatanAClinevoltageof230V/50Hzand115V/60Hzwithvariousloads.
Atavoltageof115Vandfullload,theoverallefficiencyis90.
96percent,risingto93.
39percentat230V.
Iftheefficiencyismeasuredat25,50,75and100percentloadtotheES-2standardandthemeanefficiencyiscalculated,theresultis91.
04percentat230Vand89.
52percentat115V.
ThismeansthattheconvertercanoperateatahighefficiencynotonlyatfullloadbutalsoatthelowerloadstypicalofstronglydimmedLEDs.
Table2:EfficienciesatvariousloadsReferenceValue,TypeDimensions(WxH);RM[mm],EIAformDescription,orderingcodesC2470nF-X29.
0x18.
0;15MKP,B32922C3474K000C3470nF-X29.
0x18.
0;15MKP,B32922C3474K000C4470nF-X29.
0x18.
0;15MKP,B32922C3474K000C55F14x31.
5;27.
5MKP,800V,B32774D8505K000C65F14x31.
5;27.
5MKP,800V,B32774D8505K000C75F14x31.
5;27.
5MKP,800V,B32774D8505K000C101F1206MLCC,50V,X7R,C3216X7R1H105KTC1310F1210MLCC,25V,X7R,C3225X7R1E106MC174.
7F7.
8x7.
8;5MKT,63V,B32529D0475M000C184.
7F7.
8x7.
8;5MKT,63V,B32529D0475M000C2015nF5x18;15MKP,1000V,B32652A0153K000C244.
7F0805MLCC,6.
3V,X5R,C2012X5R0J475KTC25470pF0805MLCC,50V,COG,C2012C0G1H471JTC3010F1210MLCC,25V,X7R,C3225X7R1E106KTC4010F2220MLCC,50V,X7R,C5750X7R1H106MRV1300VAC15x5;(DxW),7.
5Metaloxidevaristor,B72214S0301K101230V,50Hz115V,60HzTestconditionsVout[V]Iout[A]Pout[W]Pin[W]η[%]Vout[V]Iout[A]Pout[W]Pin[W]η[%]25%load47.
580.
68932.
837.
8786.
5747.
590.
68932.
837.
8786.
5850%load47.
571.
37865.
671.
6691.
4847.
581.
37865.
672.
9389.
9075%load47.
562.
00895.
5102.
9692.
7547.
562.
00195.
2105.
090.
64100%load47.
552.
708128.
8137.
693.
3847.
562.
703128.
6141.
3390.
96Meanefficiency91.
0489.
52Applications&Cases3/EPCOSAG·ATDKGroupCompany·Edition2015·www.
epcos.
com