NCP1351的原理和使用方法

如何采用固定導(dǎo)通時間控制器進(jìn)行設(shè)計HowtoDesignwithaFixedOn-TimeController

您優(yōu)化輕載能效的關(guān)鍵所在

YourKeytoOptimizingLightLoadEfficiency議程Agenda當(dāng)前水準(zhǔn)：準(zhǔn)諧振和固定頻率Stateoftheart:quasiresonantandfixedfrequency用于反激的固定導(dǎo)通時間(FON)控制介紹Introductiontothefixedontimecontrolforflybacks固定頻率、準(zhǔn)諧振和固定導(dǎo)通時間比較Fixedfrequency,quasiresonant,andfixedontimecomparison設(shè)計方法學(xué)及示例Designmethodologyandexample將您的固定頻率適配器更新為固定導(dǎo)通時間模式Updateyourfixedfrequencyadaptertofixedontime增添額外功能性的技巧與決竅Tipsandtrickstoaddadditionalfunctionality面向快速簡單的固定導(dǎo)通時間設(shè)計的資源Resourcesforquickandeasyfixedontimedesigns議程Agenda當(dāng)前水準(zhǔn)：準(zhǔn)諧振和固定頻率Stateoftheart:quasiresonantandfixedfrequency用于反激的固定導(dǎo)通時間(FON)控制介紹Introductiontothefixedontimecontrolforflybacks固定頻率、準(zhǔn)諧振和固定導(dǎo)通時間比較Fixedfrequency,quasiresonant,andfixedontimecomparison設(shè)計方法學(xué)及示例Designmethodologyandexample將您的固定頻率適配器更新為固定導(dǎo)通時間模式Updateyourfixedfrequencyadaptertofixedontime增添額外功能性的技巧與決竅

Tipsandtrickstoaddadditionalfunctionality面向快速簡單的固定導(dǎo)通時間設(shè)計的資源Resourcesforquickandeasyfixedontimedesigns準(zhǔn)諧振和固定頻率

QuasiResonantandFixedFrequency固定開關(guān)頻率FixedFsw準(zhǔn)諧振Quasiresonant頻率

Frequency固定Fixed可變Variable(開關(guān)頻率最小時功率最高(maxpoweratminFsw)輕載能效LightLoadEfficiencies正常Normal

(采用跳周期或頻率反走withskipmodeorfreqfoldback)谷底跳適問題(噪聲)

Valleyjumpingproblem(noise)MaxFswatminPout滿載能效FullLoadEfficiencies正常Normal最佳

Best工作模式

Operatingmode連續(xù)導(dǎo)電模式/非連續(xù)導(dǎo)電模式CCM/DCM邊界導(dǎo)電模式

BCM(Borderline)變壓器尺寸TransformerSize正常

Normal較大Larger電磁干擾

EMI正常

Normal較小

Smaller必須提升寬輸出負(fù)載范圍下的能效

Mustimprovetheefficiencyforawideoutputloadrange必須改善待機(jī)能耗

Mustimprovethestandby議程Agenda當(dāng)前水準(zhǔn)：準(zhǔn)諧振和固定頻率Stateoftheart:quasiresonantandfixedfrequency用于反激的固定導(dǎo)通時間(FON)控制介紹Introductiontothefixedontimecontrolforflybacks固定頻率、準(zhǔn)諧振和固定導(dǎo)通時間比較Fixedfrequency,quasiresonant,andfixedontimecomparison設(shè)計方法學(xué)及示例Designmethodologyandexample將您的固定頻率適配器更新為固定導(dǎo)通時間模式Updateyourfixedfrequencyadaptertofixedontime增添額外功能性的技巧與決竅

Tipsandtrickstoaddadditionalfunctionality面向快速簡單的固定導(dǎo)通時間設(shè)計的資源Resourcesforquickandeasyfixedontimedesigns固定導(dǎo)通時間(FOT)–工作原理

FixedOnTime(FOT)–PrincipleofOperation

峰值電流保持恒定，而開關(guān)頻率則會變化(改變關(guān)閉時間)，以提供必需的輸出功率：Thepeakcurrentisconstant,switchingfrequencychanges(Offtimegetslonger)todeliverthenecessaryoutputpower:

頻率最高時提供的功率最大

MaximumPowerisdeliveredatmaximumfrequency峰值電流保持恒定，可用用戶選擇

Constantpeakcurrent,userselectableFsw1@Pout1Fsw2@Pout2Pout1>Pout2固定導(dǎo)通時間(FOT)–工作原理

FixedOnTime(FOT)–PrincipleofOperation峰值電流通過控制器來保持恒定

thepeakcurrentiskeptconstantbythecontroller頻率發(fā)生變化以滿足上述等式thefrequencyvariestosatisfytheaboveequations缺少環(huán)路控制(短路，啟動)時，F(xiàn)sw被(Ct針對NCP1351進(jìn)行)鉗位

inlackofloopcontrol(short-circuit,startup),Fswisclamped(byCtfortheNCP1351)開關(guān)頻率由反饋回路進(jìn)行控制

TheFBloopcontrolstheswitchingfrequency固定導(dǎo)通時間(FOT)–可變開關(guān)頻率

FOT–VariableSwitchingFrequency(時序電容電壓

Timingcapacitorvoltage)LoadCt由回路控制ControlledbytheloopFsw

鉗位clamp在正常操作模式，回路固定著頻率，而非Ct！Innormaloperation,theloopfixesthefrequency,NOTCt!輕載條件下，峰值電流減小，開關(guān)頻率下降。這就限制了可聽噪聲問題。Inlightloadconditions,IpeakreducesandFswgoesdown.Thislimitsaudiblenoiseproblems.滿載條件下，開關(guān)頻率增加，直至其碰到Ct鉗位：故障

Infullloadconditions,FswincreasesuntilithitstheCtclamp:fault固定導(dǎo)通時間(FOT)–開關(guān)損耗

FOT–SwitchingLosses由于頻率可變，與開關(guān)頻率相關(guān)的損耗減少：Asthefrequencyisvariable,Fswrelatedlossesdecrease:Coss和門電荷損耗

Cossandgatechargelosses

泄漏感抗損耗

LeakageinductancelossesFOT大幅提高輕載能效

FOTdramaticallyimproveslightloadefficiency議程Agenda當(dāng)前水準(zhǔn)：準(zhǔn)諧振和固定頻率Stateoftheart:quasiresonantandfixedfrequency用于反激的固定導(dǎo)通時間(FON)控制介紹Introductiontothefixedontimecontrolforflybacks固定頻率、準(zhǔn)諧振和固定導(dǎo)通時間比較Fixedfrequency,quasiresonant,andfixedontimecomparison設(shè)計方法學(xué)及示例Designmethodologyandexample將您的固定頻率適配器更新為固定導(dǎo)通時間模式Updateyourfixedfrequencyadaptertofixedontime增添額外功能性的技巧與決竅

Tipsandtrickstoaddadditionalfunctionality面向快速簡單的固定導(dǎo)通時間設(shè)計的資源Resourcesforquickandeasyfixedontimedesigns控制拓?fù)浣Y(jié)構(gòu)比較

ControlTopologyComparison固定開關(guān)頻率FixedFsw準(zhǔn)諧振Quasiresonant固定導(dǎo)通時間Fixedontime頻率

Frequency固定Fixed可變Variable(開關(guān)頻率最小時功率最高(maxpoweratminFsw)可變Variable

(開關(guān)頻率最小時功率最高maxpoweratmaxFsw)輕載能效LightLoadEfficiencies正常Normal

(采用跳周期或頻率反走withskipmodeorfreqfoldback)谷底跳適問題(噪聲)

Valleyjumpingproblem(noise)MaxFswatminPout最佳

Best滿載能效FullLoadEfficiencies正常Normal最佳

Best正常

Normal工作模式

Operatingmode連續(xù)導(dǎo)電模式/非連續(xù)導(dǎo)電模式CCM/DCM邊界導(dǎo)電模式

BCM(Borderline)連續(xù)導(dǎo)電模式/非連續(xù)導(dǎo)電模式CCM/DCM變壓器尺寸TransformerSize正常

Normal較大Larger正常

Normal電磁干擾

EMI正常

Normal較小

Smaller正常Normal固定導(dǎo)通時間(FOT)：適合極寬輸出功率范圍，是您改善待機(jī)能耗和優(yōu)化工作能效的關(guān)鍵！??！FOT:yourkeytoimprovestandbyandoptimizeefficiencyforawideoutputpowerrange!!!議程Agenda當(dāng)前水準(zhǔn)：準(zhǔn)諧振和固定頻率

Stateoftheart:quasiresonantandfixedfrequency用于反激的固定導(dǎo)通時間(FON)控制介紹

Introductiontothefixedontimecontrolforflybacks固定頻率、準(zhǔn)諧振和固定導(dǎo)通時間比較

Fixedfrequency,quasiresonant,andfixedontimecomparison設(shè)計方法學(xué)及示例

Designmethodologyandexample新的NCP1351固定導(dǎo)通時間控制器

ThenewNCP1351FOTcontroller設(shè)計方法學(xué)

Designmethodology設(shè)計示例

Designexample將您的固定頻率適配器更新為固定導(dǎo)通時間模式

Updateyourfixedfrequencyadaptertofixedontime增添額外功能性的技巧與決竅

Tipsandtrickstoaddadditionalfunctionality面向快速簡單的固定導(dǎo)通時間設(shè)計的資源

ResourcesforquickandeasyfixedontimedesignsNCP1351是一款瞄準(zhǔn)總成本極為重要的低功率離線反激開關(guān)電源(SMPS)應(yīng)用的電流模式控制器

TheNCP1351isacurrent-modecontrollertargetinglowpoweroff-lineflybackSwitchedModePowerSupplies(SMPS)wheretotalcostisofutmostimportance準(zhǔn)固定導(dǎo)通時間，可變關(guān)閉時間QuasifixedTon,variableToff帶峰值電流壓縮的頻率反走FrequencyfoldbackwithPeakCurrentCompression短路保護(hù)(閉鎖A&C或自動恢復(fù)B&D)Shortcircuitprotection

適應(yīng)大輸出功率瞬態(tài)現(xiàn)象(打印機(jī))Accommodateslargeoutputpowertransients(printers)初級端或次級端穩(wěn)壓

Primaryorsecondarysideregulation閂鎖輸入

Latchinput低啟動電流

Lowstart-upcurrent固有的頻率抖動

Naturalfrequencyjittering帶可編程電流感測電阻的負(fù)電流感測功能

Negativecurrentsensingwithprogrammablecurrentsenseresistor擴(kuò)展的Vcc范圍：28

VExtendedVccrange:28VNCP1351XDR2G:SOIC8X=A,B,C,DOthersFeaturesOrdering&PackageInformationMarket&ApplicationsNCP1351–固定導(dǎo)通時間、可變關(guān)閉時間控制器

FixedOnTimeVariableOffTimeControllerPbO,DW適配器

Adapters離線電池充電器

Offlinebatterychargers輔助電源

Auxiliarypowersupplies簡單而緊湊的設(shè)計

Simpleandcompactdesign固有的頻率反走

Naturalfrequencyfoldback無噪聲，輕載能效提高

Noisefree&improvedefficiencyinlightload獨(dú)立于輔助繞組

Independentoftheaux.windingValuePropositionUniqueFeaturesBenefitsApplicationDataNCP1351–輸入輸出功率和功能描述

NCP1351–PinoutandFunctionDescriptionFB:在此引腳注入電流，降低頻率InjectingcurrentinthispinreducesthefrequencyCt:沒有反饋電流時設(shè)定最大開關(guān)頻率setsthemaximumswitchingfrequencyatnofeedbackcurrent

CS:感測初級端電流SensestheprimarycurrentTimer:設(shè)定故障確認(rèn)前的持續(xù)時間

SetsthetimedurationbeforefaultvalidationLatch:高于5

V的正電壓完全閂鎖控制器

Apositivevoltageabove5VfullylatchesoffthecontrollerVcc:為控制器提供高達(dá)28伏電壓

Suppliesthecontrollerupto28VDRV:驅(qū)動脈沖至功率MOSFETDrivingpulsestothepowerMOSFETNCP1351–峰值電流壓縮

NCP1351–PeakCurrentCompressionFBcurrentVdslightload60μA80μA270μA70μA40μAFAULT(A,Bversions)Ioffset

大負(fù)載時峰值電流恒定Constantpeakcurrentathighload

輕載時峰值電流下降Reducedpeakcurrentatlightload沒有飽和Nosaturation沒有可聽噪聲NoAudiblenoise峰值電流從100%降至26%Peakcurrentreductionfrom100%to26%NCP1351–負(fù)電流感測……

NCP1351–NegativeCurrentSensing…

ICSxRoffset產(chǎn)生正偏置(如1V)

ICSxRoffsetgeneratesapositiveoffset(e.g.1V)

電流流過時，Vsense為負(fù)值

Vsenseisnegativewhencurrentflows

兩路信號的和接近零時，MOSFET關(guān)閉

Whenthesumofbothsignalreaches0,MOSFETisoff0VVsense0VVCS不用擔(dān)心！Donotbeafraid!NCP1351–負(fù)電流感測……

NCP1351–NegativeCurrentSensing…想要降低感測電阻的功率耗散？WanttoreduceRsensepowerdissipation?選擇SelectVsense=0.5VRoffset=0.5/270u=1.8k

潔凈的電壓圖像：沒有開啟尖峰，更好的噪聲免疫性

Cleanvoltageimage:noturn-onspikes,betternoiseimmunity

一種微調(diào)最大感測電壓的途徑

Awaytofinetunethemaximumsensevoltage如何計算感測電阻和偏置電阻？

HowtocalculateRsenseandRoffset?

NCP1351–過載/短路保護(hù)

NCP1351–Overload/Short-CircuitProtection過載檢測僅依賴于反饋變化OverloaddetectiononlydependentofFBvariation2個選項：閂鎖或自動恢復(fù)

2options:latchedorautorecovery

過載OVERLOAD輸出電壓減小Voutdecreases反饋電流減小LessFBcurrent故障比較器切換FAULTcomparatortogglestimeV(CTIMER)5V500mVFB45kGNDVddNCP1351+-100mV+-Timer10μA5V保護(hù)模式Protectionmode(閂鎖或自動恢復(fù)latchedorautorecovery)D2VccVOUTCTIMERNCP1351–過載定時器OverloadTimer適應(yīng)大輸出功率瞬態(tài)現(xiàn)象Accommodateslargeoutputpowertransients適合于打印機(jī)應(yīng)用SuitableforprintersVout故障定時器啟動

Faulttimerstarts輸出負(fù)載Outputload最大輸出功率MaxoutputpowerVout故障定時器啟動Faulttimerstarts輸出負(fù)載Outputload最大峰值功率Maxpeakpower過載Overload過載Overload瞬態(tài)峰值功率Transientpeakpower輸出仍在穩(wěn)壓

Outputstillinregulation最大直流功率MaxDCpowerA&B版本versions

C&D版本versions

對MOSFET的BVdss降額后定義變比DefineturnratioafterderatingtheBVdssoftheMOSFET:NCP1351–設(shè)計方法學(xué)DesignMethodology(僅對非連續(xù)導(dǎo)電模式有效

validforDCMonly)

計算最大占空比

Calculatemaximumdutycycle:

在功率最大期間輸入電壓最低時選擇最大開關(guān)頻率ChoosethemaximumswitchingfrequencyFswatVin,minduringpowerpeaks.

然后通過下列公式計算初級端感抗值：Thencalculatetheprimaryinductancevalueby:kc:鉗位系數(shù)clampcoefficient＝Vclamp/VrVds,max=85%BVdss

推導(dǎo)初級端最大峰值電流

Deducethemaximumprimarypeakcurrent:

最后通過下列公式估計時序電容值

Finallyestimatethetimingcapacitorvalueby:

MOSFET、整流器、電感和緩沖器根據(jù)平均輸出功率(非峰值功率)來計算

NCP1351–設(shè)計方法學(xué)NCP1351–DesignMethodology(僅對非連續(xù)導(dǎo)電模式有效

validforDCMonly)(設(shè)計示例中將涉及連續(xù)導(dǎo)電模式designexamplewillcoverCCM)時序電容的正常值為

NormalizedvaluesforCTare:-65kHz:270pF-100kHz:180pFMOSFET,rectifiers,inductorsandsnubbersaredesignedaccordingtotheaveragedeliveredpower(notthepeak)NCP1351–設(shè)計示例

NCP1351–DesignExample

輸出電壓Outputvoltage:19V–57W

輸入電壓Inputvoltage:90–265Vrms

待機(jī)能耗(空載)Standbypower(no-load)<200mW

自動恢復(fù)過載保護(hù)Auto-recoveryoverloadprotection

閂鎖過壓保護(hù)(OVP)Latchedover-voltageprotection(OVP)

工作頻率Operatingfrequency:65kHz在輸入電壓為85Vac及滿載時，Cbulk

選擇為100Vdc的最低等級

Cbulk

selectedforminlevelof100VdcatVin=85Vac,fullloadNCP1351–設(shè)計示例

NCP1351–DesignExample

減小MOSFET最大的BVdss

DeratemaximumMOSFETBVdss:

針對最大高電壓來選擇鉗位電壓

Foramaximumbulkvoltage,selecttheclampingvoltage:

選擇鉗位系數(shù)的變比為1.6

Selectturnratioforakcof1.6:

計算最大占空比

Calculatemaximumduty-cycle:BVdssVds,max鉗位電壓VclampVbulk,max15%降額deratingNCP1351–設(shè)計示例

NCP1351–DesignExample對于通用的主設(shè)計而言，選擇K=0.8Forauniversalmainsdesign,selectK=0.8NCP1351–設(shè)計示例

NCP1351–DesignExample用它作為導(dǎo)電損耗UseitforconductionlossesNCP1351–設(shè)計示例

NCP1351–DesignExample使用200

V的二極管Usea200Vdiode通過270pF的Ct電容來選定65kHz頻率The65kHzselectionismadeviaCtcapacitorof270pF

如果我們想要VCS=0.5V而非1V

IfwewantVCS=0.5Vinsteadof1V

如果你沒有0.4歐姆電阻Ifyoudonothave0.4Ωresistor:Rsense=0.5Ω0.2x1.12=242mW0.50.50.2Ω1.8kΩNCP1351–設(shè)計示例

NCP1351–DesignExampleNCP1351–設(shè)計示例

NCP1351–DesignExamplePin@空載no-load=143mW,Vin=230VrmsPin@空載no-load=112mW,Vin=100VrmsAbove80%VINPOUT110Vac(60Hz)230Vac(50Hz)57W88.5%90.7%30W89.4%90.9%10W89.3%89%1W70.4%67.2%0.5W64.7%62%VINPOUT110Vac230Vac0.5W817mW855mW盡管負(fù)載變化，但效率仍維持在較高水平Efficiencyiskeptgooddespiteloadvariations.高于80%Above80%

Vout1mV/div.Vds200V/div.Vout1mV/div.Vds200V/div.NCP1351–設(shè)計示例

NCP1351–DesignExample5W負(fù)載，小輸出紋波5Wload,smalloutputripple空載，小輸出紋波Noload,smalloutputrippleNCP1351–設(shè)計示例

NCP1351–DesignExampleVout50mV/div.瞬態(tài)響應(yīng)，高線，低線Transientresponse,highline,lowline議程Agenda當(dāng)前水準(zhǔn)：準(zhǔn)諧振和固定頻率

Stateoftheart:quasiresonantandfixedfrequency用于反激的固定導(dǎo)通時間(FON)控制介紹

Introductiontothefixedontimecontrolforflybacks固定頻率、準(zhǔn)諧振和固定導(dǎo)通時間比較

Fixedfrequency,quasiresonant,andfixedontimecomparison設(shè)計方法學(xué)及示例

Designmethodologyandexample將您的固定頻率適配器更新為固定導(dǎo)通時間模式

Updateyourfixedfrequencyadaptertofixedontime增添額外功能性的技巧與決竅

Tipsandtrickstoaddadditionalfunctionality面向快速簡單的固定導(dǎo)通時間設(shè)計的資源

Resourcesforquickandeasyfixedontimedesigns將您的固定頻率適配器更新為固定導(dǎo)通時間模式！

UpdateYourFixedFrequencyAdaptertoFOT!提升輕載條件下的能效，但沒有紋波

Improvedefficiencyinlightloadconditionswithoutripple輕載條件下輸出紋波更少

Lessoutputrippleinlightloadconditions易于應(yīng)用過載保護(hù)(非耗散型)

EaseofOPPimplementation(nondissipative)基于定時器的保護(hù)與輔助電壓監(jiān)控對比

Timer-basedprotectionversusauxiliaryvoltagemonitoring僅用于非連續(xù)導(dǎo)電模式DCM

onlyDSS->無輔助繞組DSS->Noauxiliarywinding通用主電源

Universalmains將您的固定頻率適配器更新為固定導(dǎo)通時間模式！

UpdateYourFixedFrequencyAdaptertoFOT!

采用NCP1200的12

V/24

W適配器原理圖

12V/24WadapterschematicwithNCP1200開關(guān)頻率為65kHz

Switchingfrequency:65kHz內(nèi)部固定短路保護(hù)

Internalfixedshortcircuitprotection開關(guān)頻率65kHz

Switchingfrequency65kHz

選擇choose

Ct=270pFNCP1200的最大電流設(shè)定點為1V

MaximumcurrentsetpointofNCP1200is1V

選擇choose

VCS=1V，并計算Roffset:

無須修改感測電阻

NoneedtomodifyRsense光耦合器配置

OptocouplerconfigurationNCP1200:共發(fā)射極

commonemitter

NCP1351:共集電極

commoncollector將您的固定頻率適配器更新為固定導(dǎo)通時間模式！

UpdateYourFixedFrequencyAdaptertoFOT!2.4kΩ采用NCP1351的12V/24W適配器原理圖

12V/24WadapterschematicwithNCP1351將您的固定頻率適配器更新為固定導(dǎo)通時間模式！

UpdateYourFixedFrequencyAdaptertoFOT!將您的固定頻率適配器更新為固定導(dǎo)通時間模式！

UpdateYourFixedFrequencyAdaptertoFOT!輸入電壓為230Vrms時的效率和空載能耗

Efficiencyandno-loadpowerconsumptionatVin=230VrmsNCP1200NCP135124W85%85%17W84%85%10.7W83%84%1.5W66%75%0.7W57%70%0.5W52%65%空載Noload234mW78mW動態(tài)自供電功率耗散！DSSpowerdissipation!輸出紋波比較

OutputripplecomparisonVout1mV/div.Vds200V/div.Vout10mV/div.Vds100V/div.

NCP1200,空載

Noload

NCP1351,空載

NoloadNCP1351的輸出紋波要小10倍

Theoutputrippleis10timessmallerwithNCP1351將您的固定頻率適配器更新為固定導(dǎo)通時間模式！

UpdateYourFixedFrequencyAdaptertoFOT!議程Agenda當(dāng)前水準(zhǔn)：準(zhǔn)諧振和固定頻率

Stateoftheart:quasiresonantandfixedfrequency用于反激的固定導(dǎo)通時間(FON)控制介紹

Introductiontothefixedontimecontrolforflybacks固定頻率、準(zhǔn)諧振和固定導(dǎo)通時間比較

Fixedfrequency,quasiresonant,andfixedontimecomparison設(shè)計方法學(xué)及示例

Designmethodologyandexample將您的固定頻率適配器更新為固定導(dǎo)通時間模式

Updateyourfixedfrequencyadaptertofixedontime增添額外功能性的技巧與決竅

Tipsandtrickstoaddadditionalfunctionality面向快速簡單的固定導(dǎo)通時間設(shè)計的資源

Resourcesforquickandeasyfixedontimedesigns啟動技巧與決竅

Start-UpTip&Trick傳統(tǒng)配置

Classicalconfiguration改善的啟動耗散Improvedstartupdissipation啟動電阻可被任意連接

Thestartupresistorcaneitherbeconnected:至帶啟動電阻的大電容

TothebulkcapacitorwithRstartup至半波–對于相似的充電電流，選擇Rstartup/pi

Tothehalf-wave–forasimilarchargingcurrent,takeRstartup/pi半波提供最佳的閂鎖恢復(fù)時間

Half-wavegivesthebestlatchrecoveringtime啟動技巧與決竅

Start-UpTip&Trick輕載條件下，Vcc崩潰

Inlightloadconditions,Vcccollapses:增加Vcc電容，減小啟動電阻

IncreaseVcccapacitordegradesstartup將Vcc分解為兩個電容

SplitVccwithtwocapacitorsCvcc單獨(dú)正常啟動(D1)

CVccstarts-upnormallyalone(D1)Creser在待機(jī)時維持Vcc工作狀態(tài)

CreserkeepsVccaliveinstandby4.7μF47μF啟動電壓調(diào)節(jié)

StartupVoltageAdjustment極低的啟動電流/大啟動電阻值

Extremelylowstart-upcurrent/Highstart-upresistorsvalues啟動電阻

Start-upresistors最小啟動電壓調(diào)節(jié)Minimumvoltage

start-upadjustment工作時固定最小高電壓

Fixtheminimumbulkvoltageforoperation

門驅(qū)動技巧與決竅

GateDriveTip&Trick采用小型PNP來提高驅(qū)動能力

ImprovedrivecapabilitywithasmallPNP

更好的傳播延遲

betterpropagationdelay

改進(jìn)故障電流控制

improvescurrentcontrolinfaultNoPNPwithPNP200ns/div200ns/div過載保護(hù)

OverPowerProtection

只需數(shù)量很少的外部元件

Requireslimitednumberofexternalcomponents兼容于現(xiàn)有輔助繞組

CompatiblewithexistingAuxwinding二極管避免C3被反激充電ThediodeavoidsC3chargedbyflyback

在任意電壓條件下控制最大輸出功率

Controlthemaximumoutputpowerunderanyvoltagecondition非耗散型！

Nondissipative!頻率抖動技巧與決竅

FrequencyJitteringTip&Trick注入一些全波或半波紋波來增加固有頻率抖動

Injectsomefull-waveorhalf-waverippletoincreasethenaturalfrequencyjittering注入全波紋波至CS引腳

InjectfullwaverippleintoCSpin注入半波紋波至CS引腳

InjecthalfwaverippleintoCSpin閂鎖輸入技巧與決竅

LatchInputTip&TrickNTC參考電壓Referencevoltage與閂鎖引腳一起提供簡單的過壓保護(hù)和過溫度保護(hù)CombinedwiththelatchpingiveseasyOVPandOTPprotection.在FB引腳插入齊納二極管，造就更便宜的參考

InsertingzenerwithFBpin,createscheapreference.欠壓

BrownOut欠壓關(guān)閉BOoff欠壓導(dǎo)通BOon斜波補(bǔ)償

RampCompensation

斜坡補(bǔ)償1：正向斜坡補(bǔ)償至FB引腳，以降低峰值

Rampcompensation1:apositiverampintotheFBpinreducesthepeak斜波補(bǔ)償

RampCompensation

斜坡補(bǔ)償2：負(fù)電流在導(dǎo)通時間將Ct維持在低位

Rampcompensation2:anegativecurrentkeepsCtlowdurington接近Ct引腳ClosetotheCtpin軟啟動

SoftStart軟啟動(如果有必要)SoftStart

(ifnecessary)

在電源開啟期間通過軟啟動序列來限制應(yīng)力

Limitthestressatpower-onviaasoft-startsequence.VCSt將NCP1351與其他控制器相連接

InterfacingNCP1351withOtherControllersNCP1351怎樣能夠與其它控制器共享接地信號？(將負(fù)電流和正電流感測混合在一起)

HowNCP1351cansharegroundsignalwithothercontroller?(mixingnegativeandpositivecurrentsensing)NCP1351接地

NCP1351ground主接地

Mainground主接地Mainground12345867LauxD2D1Caux100uCstbvcc4.7uRsenseRcsNCP1351連接至其它控制器的VCC引腳

Toothercontroller

VCCpinorLp連接至其它控制的接地引腳和大電容

ToothercontrollerGNDpinandbulkcap布線建議

LayoutSuggestionsRsenseRoffset22pF為了改善噪聲免疫性，需要將元件布置在臨近控制器的位置

Toimprovethenoiseimmunity,keepcomponentsclosetothecontroller低阻抗點LowimpedancepointVcc改變最大開關(guān)頻率

ChangingtheMaximumSwitchingFrequency

保持Lp值不變KeepLpvalue

保持Rsense值不變

KeepRsense計算

CalculateCt修改偏置電阻值Roffse以設(shè)定新的峰值電流Ipeak2

ModifyRoffsetvaluetosetnewpeakcurrent計算磁芯磁通量

CalculatecorefluxB>Bsat?修改變壓器參數(shù)