最新-電容主要參數(shù)的應(yīng)用-PPT精品課件

1、電容主要參數(shù)的應(yīng)用作者:Morriss Su 2019.April討論目的1.介紹各參數(shù)代表的意義 2.利用參數(shù)預(yù)估計算所需值討論主題電容基本module介紹電容基本參數(shù)介紹如何應(yīng)用參數(shù)決定電容其它現(xiàn)象討論 一.電容基本Module介紹 1.REAL Module2.DC Module3.AC Module (Z=ESR)Frequency Vs Impedance二.基本參數(shù)介紹 1.LEAKGE CURRENT Leakage current is the residual current which flows through the capacitor after the chargi

2、ng time underrated voltage.2.Dissipation Factor It is a function of the series resistance of the capacitor and the capacitance at low frequency 3.Impedance=Z The formula for impedance is: Z=(R2+(L-1/C ) 2) R: equivalent series resistance of the capacitor L: Inductance mainly due to the leads C: capa

3、citance 4.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 square of ripple current (P=ESR lrms2)三.如何應(yīng)用參數(shù)決定電容1.Output 波形將V-ripple 分為 DC & AC實際電路與參數(shù)的關(guān)係Leak I

4、Z對DC而言可近似為Vin Vout 5V對AC而言( 設(shè) Z=ESR)未裝電容時 Vin Vout 50mV電容並聯(lián)時Voltage ripple:50mvx(RC/Load)/Rc+(RD/Load)=33mV如何選用適合的CAPVoltageRatingChose Type Frequency Life TempCalculator OutputImpedanceCheck 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(yù)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溫度Tx實際應(yīng)用下的環(huán)境溫度Iuse實際應(yīng)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-其他現(xiàn)象討論為何在高