NCP1351的原理和使用方法

当前水准：准谐振和固定频率Stateoftheart:quasiresonantandfixedfrequency2.用于反激的固定导通时间(FON)控制介绍Introductiontothefixedontimecontrolforflybacks3.固定频率、准谐振和固定导通时间比较Fixedfrequency,quasiresonant,andfixedontimecomparison4.设计方法学及示例Designmethodologyandexample5.将您的固定频率适配器更新为固定导通时间模式Updateyourfixedfrequencyadaptertofixedontime6.增添额外功能性的技巧与决窍Tipsandtrickstoaddadditionalfunctionality7.面向快速简单的固定导通时间设计的资源Resourcesforquickandeasyfixedontimedesigns3当前水准：准谐振和固定频率Stateoftheart:quasiresonantandfixedfrequency2.用于反激的固定导通时间(FON)控制介绍Introductiontothefixedontimecontrolforflybacks3.固定频率、准谐振和固定导通时间比较Fixedfrequency,quasiresonant,andfixedontimecomparison4.设计方法学及示例Designmethodologyandexample5.将您的固定频率适配器更新为固定导通时间模式Updateyourfixedfrequencyadaptertofixedontime6.增添额外功能性的技巧与决窍Tipsandtrickstoaddadditionalfunctionality7.面向快速简单的固定导通时间设计的资源Resourcesforquickandeasyfixedontimedesigns4(开关频率最小时功率最高(maxpoweratminFsw)轻载能效LightLoadEfficiencies正常Normal(采用跳周期或频率反走withskipmodeorfreqfoldback)谷底跳适问题(噪声)Valleyjumpingproblem(noise)MaxFswatminPout满载能效FullLoadEfficiencies正常Normal最佳Best工作模式Operatingmode连续导电模式/非连续导电模式CCM/DCM边界导电模式BCM(Borderline)变压器尺寸TransformerSize正常Normal较大Larger电磁干扰EMI正常Normal较小Smaller必须提升宽输出负载范围下的能效Mustimprovetheefficiencyforawideoutputloadrange必须改善待机能耗Mustimprovethestandby5当前水准：准谐振和固定频率Stateoftheart:quasiresonantandfixedfrequency2.用于反激的固定导通时间(FON)控制介绍Introductiontothefixedontimecontrolforflybacks3.固定频率、准谐振和固定导通时间比较Fixedfrequency,quasiresonant,andfixedontimecomparison4.设计方法学及示例Designmethodologyandexample5.将您的固定频率适配器更新为固定导通时间模式Updateyourfixedfrequencyadaptertofixedontime6.增添额外功能性的技巧与决窍Tipsandtrickstoaddadditionalfunctionality7.面向快速简单的固定导通时间设计的资源Resourcesforquickandeasyfixedontimedesigns6固定导通时间(FOT)–工作原理FixedOnTime(FOT)–PrincipleofOperation•峰值电流保持恒定，而开关频率则会变化(改变关闭时间)，以提供必需的输出功率：Thepeakcurrentisconstant,switchingfrequencychanges(Offtimegetslonger)todeliverthenecessaryoutputpower:•频率最高时提供的功率最大MaximumPowerisdeliveredatmaximumfrequency1idrain2vdrain-700m300m1.302.303.30idraininamperesPlot114.68m4.71m4.73m4.76m4.78mtimeinseconds-50.050.0150250350vdraininvoltsPlot221idrain2vdrain-700m300m1.302.303.30idraininamperesPlot114.68m4.71m4.73m4.76m4.78mtimeinseconds-50.050.0150250350vdraininvoltsPlot221idrain2vdrain-700m300m1.302.303.30idraininamperesplot114.68m4.71m4.73m4.76m4.78mtimeinseconds-50.050.0150250350vdraininvoltsplot221idrain2vdrain-700m300m1.302.303.30idraininamperesplot114.68m4.71m4.73m4.76m4.78mtimeinseconds-50.050.0150250350vdraininvoltsplot22峰值电流保持恒定，可用用户选择Constantpeakcurrent,userselectableFsw1@Pout1Fsw2@Pout2Pout1Pout27固定导通时间(FOT)–工作原理FixedOnTime(FOT)–PrincipleofOperation2,12outDCMppeakswPLIF22,12outCCMppeakvalleyswPLIIF峰值电流通过控制器来保持恒定thepeakcurrentiskeptconstantbythecontroller频率发生变化以满足上述等式thefrequencyvariestosatisfytheaboveequations缺少环路控制(短路，启动)时，Fsw被(Ct针对NCP1351进行)钳位inlackofloopcontrol(short-circuit,startup),Fswisclamped(byCtfortheNCP1351)开关频率由反馈回路进行控制TheFBloopcontrolstheswitchingfrequency8固定导通时间(FOT)–可变开关频率FOT–VariableSwitchingFrequency(时序电容电压Timingcapacitorvoltage)LoadCt由回路控制ControlledbytheloopFsw钳位clamp在正常操作模式，回路固定着频率，而非Ct！Innormaloperation,theloopfixesthefrequency,NOTCt!轻载条件下，峰值电流减小，开关频率下降。这就限制了可听噪声问题。Inlightloadconditions,IpeakreducesandFswgoesdown.Thislimitsaudiblenoiseproblems.满载条件下，开关频率增加，直至其碰到Ct钳位：故障Infullloadconditions,FswincreasesuntilithitstheCtclamp:fault9固定导通时间(FOT)–开关损耗FOT–SwitchingLosses由于频率可变，与开关频率相关的损耗减少：Asthefrequencyisvariable,Fswrelatedlossesdecrease:Coss和门电荷损耗Cossandgatechargelosses泄漏感抗损耗LeakageinductancelossesswGGSGATEFQVPswDSOSSSWITCHINGFVCP221FOT大幅提高轻载能效FOTdramaticallyimproveslightloadefficiencyswpeakleakleakFILP22110当前水准：准谐振和固定频率Stateoftheart:quasiresonantandfixedfrequency2.用于反激的固定导通时间(FON)控制介绍Introductiontothefixedontimecontrolforflybacks3.固定频率、准谐振和固定导通时间比较Fixedfrequency,quasiresonant,andfixedontimecomparison4.设计方法学及示例Designmethodologyandexample5.将您的固定频率适配器更新为固定导通时间模式Updateyourfixedfrequencyadaptertofixedontime6.增添额外功能性的技巧与决窍Tipsandtrickstoaddadditionalfunctionality7.面向快速简单的固定导通时间设计的资源Resourcesforquickandeasyfixedontimedesigns11(开关频率最小时功率最高(maxpoweratminFsw)可变Variable(开关频率最小时功率最高maxpoweratmaxFsw)轻载能效LightLoadEfficiencies正常Normal(采用跳周期或频率反走withskipmodeorfreqfoldback)谷底跳适问题(噪声)Valleyjumpingproblem(noise)MaxFswatminPout最佳Best满载能效FullLoadEfficiencies正常Normal最佳Best正常Normal工作模式Operatingmode连续导电模式/非连续导电模式CCM/DCM边界导电模式BCM(Borderline)连续导电模式/非连续导电模式CCM/DCM变压器尺寸TransformerSize正常Normal较大Larger正常Normal电磁干扰EMI正常Normal较小Smaller正常Normal固定导通时间(FOT)：适合极宽输出功率范围，是您改善待机能耗和优化工作能效的关键！！！FOT:yourkeytoimprov