电解电容寿命与纹波电流测试

1、电解电容寿命纹波电流测试E-capLifetimeTest工作原理/WorkingprincipleIk0c充b单相桥式整流电容滤波电路及稳态吋的波形分析(a)Ik0c充b单相桥式整流电容滤波电路及稳态吋的波形分析(a)电路(b)uo的波形200V5OHzC乩放02左JT单相桥式整流电容滤波电路及稳态吋的波形分柝(a)电路C乩放02左JT单相桥式整流电容滤波电路及稳态吋的波形分柝(a)电路(b)uo的波形200V5OHz当U2为正半周并且数值大于电容两端电压Uc时，二极管D1和D3管导通，D2和D4管截止，电流一路流经负载电阻RL,另一路对电容C充电。当UcU2,导致D1和D3管反向偏置而截止

2、，电容通过负载电阻RL放电，Uc按指数规律缓慢下降。ThediodeD1&D3work,D2&D4cutoff,thecurrentflowsthroughtheloadresistanceRLinaloopandchargethecapacitorCupwhenU2inthepositivehalfcircuitanditsvalueexceedingthevoltageUcwhichisparallelconnectedinthetwoterminalsofcapacitor.WhenUcexceedsU2,andcausesthediodeD1&D3cutoff,thecapacitor

3、dischargethroughtheloadresistanceRLandUcdeclineslowlyaccordingtotheprincipleofindexfunction.当U2为负半周幅值变化到恰好大于Uc时，D2和D4因加正向电压变为导通状态，U2再次对C充电，Uc上升到U2的峰值后又开始下降；下降到一定数值时D2和D4变为截止，C对RL放电，Uc按指数规律下降；放电到一定数值时D1和D3变为导通，重复上述过程。Asthesamereason,whenU2inthenegativehalfcircuitandtheamplitudeisevenchangedtoexceedUc

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

5、ecyclerepeats.测试方法/TestMethod2.1测试温升计算电容寿命/Lifetimeofcapacitorattestingtemperaturecondition计算寿命公式/FormulaforcalculatinglifetimeTQ_攻10TQ_攻10适用公司/CorporationUited适用公司/CorporationUited:FconKsC、tL、TEAPOapXd说明/Explanation：Lo：isoperatinglifeofcapacitanceSPECTo：isSPECtemperatureofcapacitorTx：iscapacitoramb

6、ientoperatingtemperatureTc：issurfacetemperatureofcapacitorcaseKc：iscoefficientfromtablebelowLx：usefullifeestimation2.2测试纹波电流计算电容寿命/Lifetimeofcapacitorattestingripplecurrentcondition计算寿命公式/FormulaforcalculatinglifetimeLx=Lo*Kt*Kr(Kt=2人(To-Tx)/10Kr=(5-厶)/5t=5*(Ix/Io)人2)适用公司/Corporationsuited:HEC、Jiang

7、haiLo:isoperatinglifeofcapacitanceSPECisSPECtemperatureofcapacitorTo:Tx:iscapacitorambientoperatingtemperatureIx:isactualvalueofripplecurrentIo:Lx:isspecifiedripplecurrentusefullifeestimation2.2.1直接测量电容纹波电流/DirectmeasureofE-capripplecurrentLDpTiirpncL.开关电路中电容纹波电流分析LDpTiirpncL.开关电路中电容纹波电流分析Cl为buck电容，

8、其充电时间受到低频交流输入影响，而放电时间则是受到开关管Q1的高频影响。即A点受到低频交流输入影响，频率为交流频率的2倍，100Hz左右，故A点处所测试出电流为电容C1的低频纹波电流(IL)；B点受到高频开关Q1的影响，频率一般为100KHz，故B点所测试出的电流为电容C1的高频纹波电流(IH)。C1isthebuckcapacitor,itschargetimeliesonthelowfrequencyVacinput,andthedischargetimeinfluencedbythehighfrequencyofswitchingMOSFETQ1.Thefrequencyofpositi

9、onA,lyingontheVacinput,isdoubled,about100Hz.AndthecurrentflowedthroughjustisthelowfrequencycurrentofC1;similarly,thefrequencyofpositionB,lyingontheQ1,isabout100KHz,andthecurrentishighfrequency.目前我司对电容纹波计算方法定义为/Thetestmethoddefinedinourcompanyatpresentis：IL:IH:LowfrequencyoperatingripplecurrentIL(low

10、Freq)(A)HighfrequencyoperatingripplecurrentIH(lowFreq)(A)F1:CoefficientforlowfrequencycompensationF:CoefficientforhighfrequencycompensationT:CoefficientfortemperaturecompensationLx:Actualcurrent2.2.2利用低通和高通滤波电路测量纹波电流/Measurementvialowpassorhighpassfilter对于输入大容量的电容，有低频(100HZ)和高频(开关频率，如100KHZ)两种电流流过，电

11、流的测量必须串一个电流检测电阻去获得，而且低频纹波电流和高频纹波电流应分别测量。Forbulkcapacitor,bothlowfrequency(100HZ)andhighfrequency(switchingfrequency,say100KHz)currentareflowing.Thecurrentshallbemeasuredwithacurrentsenseresistor.Asthelowandhighfrequencyrippleshallbemeasuredseparately.UiUoUiUo低通滤波电路低通滤波电路高通滤波电路低通滤波电路的带宽为0wc(wc=1/RC),

12、高频滤波电路带宽则为wc。Thebandwidthoflowpassfilteris0wc(wc=1/RC),andwcinhighpassfilter.在检测电阻上并接一个RC(1k5、O.luF)电路，(如下图所示)用有效值表测量O.luF两端的有效电压，即可得低频纹波电流值，此时高频成分已被滤除。AddanRC(1K5,0.1uF)acrossthesenseresistor,measurermsvoltageacross0.1uF;thiswillfilteroutthehighfrequency,leavingthe100Hzripplecurrent.低频纹波电流测试图在检测电阻上并接一个RC(O.luF、1K5)电路，(如下图所示)，用有效值表测1K5电阻两端的有效值电压，根据I=U/R即可获得高频纹波电流值，此时