最新-电容主要参数的应用-PPT精品课件.ppt

1、電容主要參數的應用電容主要參數的應用作者作者:Morriss Su 2019.April討論目的討論目的1.介紹各參數代表的意義 2.利用參數預估計算所需值討論主題討論主題n電容基本module介紹n電容基本參數介紹n如何應用參數決定電容n其它現象討論 一一.電容基本電容基本Module介紹介紹 1.REAL Module CR21 R21 L2.DC Module CR21 R21 L M ohm21 CR21 R21 L M ohm213.AC Module(Z=ESR)CR21 R21 Lm ohm21Frequency Vs Impedance二二.基本參數介紹基本參數介紹 1.LEA

2、KGE CURRENT Leakage current is the residual current which flows through the capacitor after the charging time underrated voltage.n2.Dissipation Factor It is a function of the series resistance of the capacitor and the capacitance at low frequency n3.Impedance=Zn The formula for impedance is:Z=(R2+(L

3、-1/C)2)n R:equivalent series resistance of the capacitor L:Inductance mainly due to the leads C:capacitance n4.Maximun current ripple&Voltage rippleThe maximum value of the ripple current or ripple voltage which can be applied to the capacitor is only limited by the thermal effect.The ESR and to the

4、 square of ripple current(P=ESR lrms2)三三.如何應用參數決定電容如何應用參數決定電容n1.Output 波形波形將將V-ripple 分為分為 DC&AC實際電路與參數的關係實際電路與參數的關係 CR21 R21 L CR21 R21 L LL Lo oa ad dTest pinLeak IZ對對DC而言而言5m ohm21A AA Au uA Au uA A5 5V V D DC CM ohm21M ohm21L Lo oa ad dTest pin可近似為可近似為5m ohm215 5V V D DC CA AA AL Lo oa ad dTest

5、pinVin Vout 5V對對AC而言而言(設設 Z=ESR)n未裝電容時n 5m ohm21L Lo oa ad dTest pin5 50 0 o oh hm m50mVVin Vout 50mV電容並聯時電容並聯時Voltage ripple:50mvx(RC/Load)/Rc+(RD/Load)=33mV5m ohm21L Lo oa ad dTest pin50mV5 50 0 o oh hm m100 ohm21如何選用適合的如何選用適合的CAPVoltageRatingChose Type Frequency Life TempCalculator OutputImpedanc

6、eCheck V Ripplein SPECCalculator I Ripple in SPECTest thermal calculatorLife timeDimensions123例:Output 5V 20A5/20=0.25=250m選擇小於10倍ESR的兩個6.3V 58m的CAP例:5V V Ripple 為50mV(在C上測到)則Cape的 I Ripple為50mV/58m=0.862mA4代號意義單位L2實際使用下電容器預估壽命值小時L1廠商保證之壽命值小時T0電容器之額定最高工作温度Tx實際應用下的環境温度Iuse實際應用下的漣波電流mAIstd型錄上的額定漣波電流(r.m.s)mAK加速因子-KIstdIuseTxTLL2551002*2*12其他現象討論其他現象討論n為何在高溫時Ripple會較好?n為何同樣的濾波電容前級較後級Ripple Current 高?n為何電容要越接近Output端越好?作者作者:Morriss Su