電解電容壽命與紋波電流測(cè)試

1、電解電容壽命紋波電流測(cè)試E-capLifetimeTest工作原理/WorkingprincipleIk0c充b單相橋式整流電容濾波電路及穩(wěn)態(tài)吋的波形分析(a)Ik0c充b單相橋式整流電容濾波電路及穩(wěn)態(tài)吋的波形分析(a)電路(b)uo的波形200V5OHzC乩放02左JT單相橋式整流電容濾波電路及穩(wěn)態(tài)吋的波形分柝(a)電路C乩放02左JT單相橋式整流電容濾波電路及穩(wěn)態(tài)吋的波形分柝(a)電路(b)uo的波形200V5OHz當(dāng)U2為正半周并且數(shù)值大于電容兩端電壓Uc時(shí)，二極管D1和D3管導(dǎo)通，D2和D4管截止，電流一路流經(jīng)負(fù)載電阻RL,另一路對(duì)電容C充電。當(dāng)UcU2,導(dǎo)致D1和D3管反向偏置而截止

2、，電容通過(guò)負(fù)載電阻RL放電，Uc按指數(shù)規(guī)律緩慢下降。ThediodeD1&D3work,D2&D4cutoff,thecurrentflowsthroughtheloadresistanceRLinaloopandchargethecapacitorCupwhenU2inthepositivehalfcircuitanditsvalueexceedingthevoltageUcwhichisparallelconnectedinthetwoterminalsofcapacitor.WhenUcexceedsU2,andcausesthediodeD1&D3cutoff,thecapacitor

3、dischargethroughtheloadresistanceRLandUcdeclineslowlyaccordingtotheprincipleofindexfunction.當(dāng)U2為負(fù)半周幅值變化到恰好大于Uc時(shí)，D2和D4因加正向電壓變?yōu)閷?dǎo)通狀態(tài)，U2再次對(duì)C充電，Uc上升到U2的峰值后又開(kāi)始下降；下降到一定數(shù)值時(shí)D2和D4變?yōu)榻刂梗珻對(duì)RL放電，Uc按指數(shù)規(guī)律下降；放電到一定數(shù)值時(shí)D1和D3變?yōu)閷?dǎo)通，重復(fù)上述過(guò)程。Asthesamereason,whenU2inthenegativehalfcircuitandtheamplitudeisevenchangedtoexceedUc

4、,thediodeD2&D4workduetothepositivevoltageandU2chargecapacitorCupagain.UcstarttodeclinewhenitsvoltagerisetothepeakvalueofU2andtoacertainvalue,thediodeD2&D4cutoff,thecapacitorCdischargetoRL,Ucdeclineaccordingtotheprincipleofindexfunctionagain.Whenthedischargetoacertainvalue,thediodeD1&D3workagainandth

5、ecyclerepeats.測(cè)試方法/TestMethod2.1測(cè)試溫升計(jì)算電容壽命/Lifetimeofcapacitorattestingtemperaturecondition計(jì)算壽命公式/FormulaforcalculatinglifetimeTQ_攻10TQ_攻10適用公司/CorporationUited適用公司/CorporationUited:FconKsC、tL、TEAPOapXd說(shuō)明/Explanation：Lo：isoperatinglifeofcapacitanceSPECTo：isSPECtemperatureofcapacitorTx：iscapacitoramb

6、ientoperatingtemperatureTc：issurfacetemperatureofcapacitorcaseKc：iscoefficientfromtablebelowLx：usefullifeestimation2.2測(cè)試紋波電流計(jì)算電容壽命/Lifetimeofcapacitorattestingripplecurrentcondition計(jì)算壽命公式/FormulaforcalculatinglifetimeLx=Lo*Kt*Kr(Kt=2人(To-Tx)/10Kr=(5-厶)/5t=5*(Ix/Io)人2)適用公司/Corporationsuited:HEC、Jiang

7、haiLo:isoperatinglifeofcapacitanceSPECisSPECtemperatureofcapacitorTo:Tx:iscapacitorambientoperatingtemperatureIx:isactualvalueofripplecurrentIo:Lx:isspecifiedripplecurrentusefullifeestimation2.2.1直接測(cè)量電容紋波電流/DirectmeasureofE-capripplecurrentLDpTiirpncL.開(kāi)關(guān)電路中電容紋波電流分析LDpTiirpncL.開(kāi)關(guān)電路中電容紋波電流分析Cl為buck電容，

8、其充電時(shí)間受到低頻交流輸入影響，而放電時(shí)間則是受到開(kāi)關(guān)管Q1的高頻影響。即A點(diǎn)受到低頻交流輸入影響，頻率為交流頻率的2倍，100Hz左右，故A點(diǎn)處所測(cè)試出電流為電容C1的低頻紋波電流(IL)；B點(diǎn)受到高頻開(kāi)關(guān)Q1的影響，頻率一般為100KHz，故B點(diǎn)所測(cè)試出的電流為電容C1的高頻紋波電流(IH)。C1isthebuckcapacitor,itschargetimeliesonthelowfrequencyVacinput,andthedischargetimeinfluencedbythehighfrequencyofswitchingMOSFETQ1.Thefrequencyofpositi

9、onA,lyingontheVacinput,isdoubled,about100Hz.AndthecurrentflowedthroughjustisthelowfrequencycurrentofC1;similarly,thefrequencyofpositionB,lyingontheQ1,isabout100KHz,andthecurrentishighfrequency.目前我司對(duì)電容紋波計(jì)算方法定義為/Thetestmethoddefinedinourcompanyatpresentis：IL:IH:LowfrequencyoperatingripplecurrentIL(low

10、Freq)(A)HighfrequencyoperatingripplecurrentIH(lowFreq)(A)F1:CoefficientforlowfrequencycompensationF:CoefficientforhighfrequencycompensationT:CoefficientfortemperaturecompensationLx:Actualcurrent2.2.2利用低通和高通濾波電路測(cè)量紋波電流/Measurementvialowpassorhighpassfilter對(duì)于輸入大容量的電容，有低頻(100HZ)和高頻(開(kāi)關(guān)頻率，如100KHZ)兩種電流流過(guò)，電

11、流的測(cè)量必須串一個(gè)電流檢測(cè)電阻去獲得，而且低頻紋波電流和高頻紋波電流應(yīng)分別測(cè)量。Forbulkcapacitor,bothlowfrequency(100HZ)andhighfrequency(switchingfrequency,say100KHz)currentareflowing.Thecurrentshallbemeasuredwithacurrentsenseresistor.Asthelowandhighfrequencyrippleshallbemeasuredseparately.UiUoUiUo低通濾波電路低通濾波電路高通濾波電路低通濾波電路的帶寬為0wc(wc=1/RC),

12、高頻濾波電路帶寬則為wc。Thebandwidthoflowpassfilteris0wc(wc=1/RC),andwcinhighpassfilter.在檢測(cè)電阻上并接一個(gè)RC(1k5、O.luF)電路，(如下圖所示)用有效值表測(cè)量O.luF兩端的有效電壓，即可得低頻紋波電流值，此時(shí)高頻成分已被濾除。AddanRC(1K5,0.1uF)acrossthesenseresistor,measurermsvoltageacross0.1uF;thiswillfilteroutthehighfrequency,leavingthe100Hzripplecurrent.低頻紋波電流測(cè)試圖在檢測(cè)電阻上并接一個(gè)RC(O.luF、1K5)電路，(如下圖所示)，用有效值表測(cè)1K5電阻兩端的有效值電壓，根據(jù)I=U/R即可獲得高頻紋波電流值，此時(shí)