詳解電容在電源中所起到的作用
2019/7/1 12:46:11??????點擊：
作(zuo)(zuo)為無源元件之一的電容，其作(zuo)(zuo)用(yong)不外乎以下幾(ji)種：
1、應用于(yu)電(dian)源電(dian)路(lu)，實現旁(pang)路(lu)、去(qu)藕、濾(lv)波和儲能方(fang)面(mian)電(dian)容(rong)的作用，下面(mian)分類詳述(shu)之：
1)濾波(bo)
濾(lv)波是(shi)電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)(rong)的(de)(de)作用中很重(zhong)要的(de)(de)一(yi)部分。幾乎所有(you)的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)源電(dian)(dian)(dian)(dian)(dian)(dian)路中都(dou)會用到。從理論上(即假設電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)(rong)為(wei)純(chun)電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)(rong))說(shuo)，電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)(rong)越(yue)(yue)大(da)，阻(zu)(zu)抗越(yue)(yue)小(xiao)(xiao)，通(tong)(tong)(tong)過(guo)的(de)(de)頻(pin)率(lv)也(ye)越(yue)(yue)高(gao)。但實際上超(chao)過(guo)1uF的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)(rong)大(da)多為(wei)電(dian)(dian)(dian)(dian)(dian)(dian)解電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)(rong)，有(you)很大(da)的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)感成份(fen)，所以(yi)頻(pin)率(lv)高(gao)后反而阻(zu)(zu)抗會增大(da)。有(you)時(shi)會看到有(you)一(yi)個(ge)電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)(rong)量較(jiao)大(da)電(dian)(dian)(dian)(dian)(dian)(dian)解電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)(rong)并聯了一(yi)個(ge)小(xiao)(xiao)電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)(rong)，這時(shi)大(da)電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)(rong)通(tong)(tong)(tong)低(di)頻(pin)，小(xiao)(xiao)電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)(rong)通(tong)(tong)(tong)高(gao)頻(pin)。電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)(rong)的(de)(de)作用就是(shi)通(tong)(tong)(tong)高(gao)阻(zu)(zu)低(di)，通(tong)(tong)(tong)高(gao)頻(pin)阻(zu)(zu)低(di)頻(pin)。電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)(rong)越(yue)(yue)大(da)低(di)頻(pin)越(yue)(yue)容(rong)(rong)(rong)(rong)(rong)(rong)(rong)易通(tong)(tong)(tong)過(guo)，電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)(rong)越(yue)(yue)大(da)高(gao)頻(pin)越(yue)(yue)容(rong)(rong)(rong)(rong)(rong)(rong)(rong)易通(tong)(tong)(tong)過(guo)。具體用在濾(lv)波中,大(da)電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)(rong)(1000uF)濾(lv)低(di)頻(pin)，小(xiao)(xiao)電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)(rong)(20pF)濾(lv)高(gao)頻(pin)。
曾有網友將(jiang)濾波(bo)電(dian)容 比(bi)作“水塘”。由于電(dian)容的(de)兩(liang)端(duan)電(dian)壓(ya)不會突變(bian)，由此可知，信號頻率越(yue)高則衰減越(yue)大，可很形(xing)象的(de)說電(dian)容像個水塘，不會因幾滴水的(de)加(jia)入或蒸發而引起(qi)水量的(de)變(bian)化。 它(ta)把電(dian)壓(ya)的(de)變(bian)動轉化為電(dian)流的(de)變(bian)化，頻率越(yue)高，峰(feng)值(zhi)電(dian)流就越(yue)大，從而緩沖了(le)電(dian)壓(ya)。濾波(bo)就是(shi)充電(dian)，放電(dian)的(de)過程。
2)旁路(lu)
旁(pang)(pang)路(lu)電(dian)(dian)容是(shi)為(wei)本地(di)(di)(di)器(qi)(qi)件(jian)提(ti)供能(neng)量的(de)儲能(neng)器(qi)(qi)件(jian)，它能(neng)使(shi)穩(wen)壓器(qi)(qi)的(de)輸出均勻(yun)化，降低負載需求。就像(xiang)小型可充電(dian)(dian)電(dian)(dian)池一樣，旁(pang)(pang)路(lu)電(dian)(dian)容能(neng)夠(gou)被充電(dian)(dian)，并(bing)向器(qi)(qi)件(jian)進行(xing)放 電(dian)(dian)。為(wei)盡量減少阻抗(kang)，旁(pang)(pang)路(lu)電(dian)(dian)容要盡量靠近負載器(qi)(qi)件(jian)的(de)供電(dian)(dian)電(dian)(dian)源管腳和地(di)(di)(di)管腳。這能(neng)夠(gou)很好(hao)地(di)(di)(di)防止輸入值過大(da)而(er)導致的(de)地(di)(di)(di)電(dian)(dian)位抬(tai)高和噪聲。地(di)(di)(di)彈是(shi)地(di)(di)(di)連接處在通過大(da) 電(dian)(dian)流毛刺時的(de)電(dian)(dian)壓降。
3)去藕
去藕(ou)，又(you)稱解藕(ou)。從電(dian)(dian)(dian)(dian)路(lu)(lu)(lu)來說，總是(shi)(shi)可以區(qu)分為驅動的(de)(de)(de)(de)(de)源(yuan)和被驅動的(de)(de)(de)(de)(de)負載。如果負載電(dian)(dian)(dian)(dian)容(rong)(rong)(rong)比較(jiao)大(da)，驅動電(dian)(dian)(dian)(dian)路(lu)(lu)(lu)要把電(dian)(dian)(dian)(dian)容(rong)(rong)(rong)充電(dian)(dian)(dian)(dian)、放電(dian)(dian)(dian)(dian)，才能完成(cheng)信(xin)(xin)號(hao)的(de)(de)(de)(de)(de)跳變(bian)，在上(shang) 升沿(yan)比較(jiao)陡峭的(de)(de)(de)(de)(de)時候，電(dian)(dian)(dian)(dian)流(liu)(liu)比較(jiao)大(da)，這(zhe)樣驅動的(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)流(liu)(liu)就(jiu)會吸收很大(da)的(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)源(yuan)電(dian)(dian)(dian)(dian)流(liu)(liu)，由于電(dian)(dian)(dian)(dian)路(lu)(lu)(lu)中(zhong)的(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)感，電(dian)(dian)(dian)(dian)阻(特別(bie)是(shi)(shi)芯片管腳上(shang)的(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)感，會產生反彈)，這(zhe)種(zhong)電(dian)(dian)(dian)(dian)流(liu)(liu)相對 于正(zheng)常情況來說實際上(shang)就(jiu)是(shi)(shi)一(yi)種(zhong)噪聲，會影響前級的(de)(de)(de)(de)(de)正(zheng)常工作。這(zhe)就(jiu)是(shi)(shi)耦(ou)(ou)(ou)合(he)(he)(he)。去藕(ou)電(dian)(dian)(dian)(dian)容(rong)(rong)(rong)就(jiu)是(shi)(shi)起到(dao)一(yi)個電(dian)(dian)(dian)(dian)池的(de)(de)(de)(de)(de)作用，滿足驅動電(dian)(dian)(dian)(dian)路(lu)(lu)(lu)電(dian)(dian)(dian)(dian)流(liu)(liu)的(de)(de)(de)(de)(de)變(bian)化，避免相互間的(de)(de)(de)(de)(de)耦(ou)(ou)(ou)合(he)(he)(he)干(gan)(gan)擾。將(jiang)旁(pang)路(lu)(lu)(lu)電(dian)(dian)(dian)(dian)容(rong)(rong)(rong)和去藕(ou)電(dian)(dian)(dian)(dian)容(rong)(rong)(rong)結(jie)合(he)(he)(he)起來將(jiang)更容(rong)(rong)(rong)易理解。旁(pang)路(lu)(lu)(lu)電(dian)(dian)(dian)(dian)容(rong)(rong)(rong)實際也是(shi)(shi)去藕(ou)合(he)(he)(he)的(de)(de)(de)(de)(de)，只是(shi)(shi)旁(pang)路(lu)(lu)(lu)電(dian)(dian)(dian)(dian)容(rong)(rong)(rong)一(yi)般是(shi)(shi)指高(gao)頻(pin)(pin)旁(pang)路(lu)(lu)(lu)，也就(jiu)是(shi)(shi)給高(gao)頻(pin)(pin)的(de)(de)(de)(de)(de)開關噪聲提高(gao)一(yi)條低阻抗泄防(fang) 途徑。高(gao)頻(pin)(pin)旁(pang)路(lu)(lu)(lu)電(dian)(dian)(dian)(dian)容(rong)(rong)(rong)一(yi)般比較(jiao)小，根據諧振頻(pin)(pin)率(lv)一(yi)般是(shi)(shi)0.1u，0.01u等，而去耦(ou)(ou)(ou)合(he)(he)(he)電(dian)(dian)(dian)(dian)容(rong)(rong)(rong)一(yi)般比較(jiao)大(da)，是(shi)(shi)10uF或(huo)者(zhe)更大(da)，依據電(dian)(dian)(dian)(dian)路(lu)(lu)(lu)中(zhong)分布參數，以及驅動 電(dian)(dian)(dian)(dian)流(liu)(liu)的(de)(de)(de)(de)(de)變(bian)化大(da)小來確定(ding)。旁(pang)路(lu)(lu)(lu)是(shi)(shi)把輸入信(xin)(xin)號(hao)中(zhong)的(de)(de)(de)(de)(de)干(gan)(gan)擾作為濾(lv)除對象，而去耦(ou)(ou)(ou)是(shi)(shi)把輸出信(xin)(xin)號(hao)的(de)(de)(de)(de)(de)干(gan)(gan)擾作為濾(lv)除對象，防(fang)止干(gan)(gan)擾信(xin)(xin)號(hao)返(fan)回(hui)電(dian)(dian)(dian)(dian)源(yuan)。這(zhe)應該是(shi)(shi)他們(men)的(de)(de)(de)(de)(de)本質區(qu)別(bie)。
4)儲能(neng)
儲能型電(dian)(dian)(dian)容(rong)(rong)器通過整流器收集(ji)電(dian)(dian)(dian)荷，并將存(cun)儲的(de)(de)能量通過變換器引線(xian)傳送(song)至電(dian)(dian)(dian)源(yuan)的(de)(de)輸出端。電(dian)(dian)(dian)壓額定值(zhi)為40～450VDC、電(dian)(dian)(dian)容(rong)(rong)值(zhi)在(zai)220～150 000uF之間的(de)(de)鋁電(dian)(dian)(dian)解電(dian)(dian)(dian)容(rong)(rong)器(如EPCOS公司的(de)(de) B43504或(huo)B43505)是較為常用(yong)(yong)的(de)(de)。根據不同的(de)(de)電(dian)(dian)(dian)源(yuan)要求，器件(jian)有時(shi)會采用(yong)(yong)串聯(lian)、并聯(lian)或(huo)其(qi)組合的(de)(de)形式， 對于功率級超過10KW的(de)(de)電(dian)(dian)(dian)源(yuan)，通常采用(yong)(yong)體積較大(da)的(de)(de)罐形螺旋端子電(dian)(dian)(dian)容(rong)(rong)器。
2、應用于信號電路(lu)，主要完成耦(ou)合、振(zhen)蕩/同步及時間常(chang)數的(de)作用：
1)耦合
舉個例子(zi)來講，晶體管(guan)放大器發射極有(you)一個自(zi)給偏壓(ya)電(dian)(dian)阻，它同時(shi)又(you)使(shi)信(xin)號產生(sheng)壓(ya)降反饋(kui)到(dao)輸(shu)入端形成了輸(shu)入輸(shu)出信(xin)號耦(ou)合(he)，這(zhe)個電(dian)(dian)阻就是產生(sheng)了耦(ou)合(he)的元(yuan)件，如果在這(zhe)個電(dian)(dian)阻兩端并聯一個電(dian)(dian)容，由于適當容量的電(dian)(dian)容器對交流信(xin)號較小(xiao)的阻抗,這(zhe)樣(yang)就減小(xiao)了電(dian)(dian)阻產生(sheng)的耦(ou)合(he)效應，故(gu)稱此電(dian)(dian)容為(wei)去(qu)耦(ou)電(dian)(dian)容。
2)振蕩/同步(bu)
包括RC、LC振蕩器及晶體(ti)的負載電容(rong)都屬于這一范疇。
3)時間常(chang)數
這就是常見的(de)(de) R、C 串聯構成的(de)(de)積分電路。當輸(shu)(shu)入信號電壓(ya)加在輸(shu)(shu)入端時，電容(C)上的(de)(de)電壓(ya)逐漸(jian)上升(sheng)(sheng)。而其(qi)充電電流則隨著電壓(ya)的(de)(de)上升(sheng)(sheng)而減(jian)小。電流通過電阻(R)、電容(C)的(de)(de)特性通過下面的(de)(de)公(gong)式描述：
i = (V/R)e-(t/CR)
我們知道了(le)電容的作用(yong)以后(hou)下面來談談電容在使用(yong)中的注意事(shi)項
A. 什么是好電容。
1.電(dian)容(rong)容(rong)量越大越好。
很多人在(zai)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)的(de)(de)(de)(de)(de)(de)(de)替換中往往愛用大(da)(da)容(rong)(rong)(rong)(rong)量的(de)(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)。我們知道雖然電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)越(yue)(yue)大(da)(da)，為IC提供(gong)的(de)(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)流補(bu)償(chang)的(de)(de)(de)(de)(de)(de)(de)能(neng)(neng)力(li)(li)越(yue)(yue)強。且不說電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)容(rong)(rong)(rong)(rong)量的(de)(de)(de)(de)(de)(de)(de)增(zeng)(zeng)大(da)(da)帶來的(de)(de)(de)(de)(de)(de)(de)體積變大(da)(da)，增(zeng)(zeng)加成本的(de)(de)(de)(de)(de)(de)(de)同時還影響空氣(qi)流動和散熱。關鍵在(zai)于電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)上存在(zai)寄(ji)生(sheng)(sheng)電(dian)(dian)(dian)(dian)(dian)感，電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)放電(dian)(dian)(dian)(dian)(dian)回(hui)(hui)路會(hui)在(zai)某個頻點上發生(sheng)(sheng)諧振(zhen)。在(zai)諧振(zhen)點，電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)的(de)(de)(de)(de)(de)(de)(de)阻抗小(xiao)。因此放電(dian)(dian)(dian)(dian)(dian)回(hui)(hui)路的(de)(de)(de)(de)(de)(de)(de)阻抗最(zui)小(xiao)，補(bu)充能(neng)(neng)量的(de)(de)(de)(de)(de)(de)(de)效果也(ye)最(zui)好。但當(dang)頻率超過(guo)諧振(zhen)點時，放電(dian)(dian)(dian)(dian)(dian)回(hui)(hui)路的(de)(de)(de)(de)(de)(de)(de)阻抗開(kai)始增(zeng)(zeng)加，電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)提供(gong)電(dian)(dian)(dian)(dian)(dian)流能(neng)(neng)力(li)(li)便開(kai)始下降(jiang)。電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)的(de)(de)(de)(de)(de)(de)(de)容(rong)(rong)(rong)(rong)值(zhi)越(yue)(yue)大(da)(da)，諧振(zhen)頻率越(yue)(yue)低(di)，電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)能(neng)(neng)有(you)效補(bu)償(chang)電(dian)(dian)(dian)(dian)(dian)流的(de)(de)(de)(de)(de)(de)(de)頻率范圍也(ye)越(yue)(yue)小(xiao)。從保(bao)證電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)提供(gong)高頻電(dian)(dian)(dian)(dian)(dian)流的(de)(de)(de)(de)(de)(de)(de)能(neng)(neng)力(li)(li)的(de)(de)(de)(de)(de)(de)(de)角度(du)來說，電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)越(yue)(yue)大(da)(da)越(yue)(yue)好的(de)(de)(de)(de)(de)(de)(de)觀點是錯誤的(de)(de)(de)(de)(de)(de)(de)，一般的(de)(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)路設(she)計中都有(you)一個參考(kao)值(zhi)的(de)(de)(de)(de)(de)(de)(de)。
2.同樣容量的電容，并(bing)聯越(yue)多的小電容越(yue)好
耐壓值、耐溫(wen)值、容(rong)(rong)(rong)值、ESR(等(deng)效電阻(zu))等(deng)是電容(rong)(rong)(rong)的幾個(ge)重要(yao)參數，對于ESR自然是越(yue)低越(yue)好。ESR與電容(rong)(rong)(rong)的容(rong)(rong)(rong)量(liang)、頻(pin)率(lv)、電壓、溫(wen)度等(deng)都有關系。當電壓固定(ding)時候，容(rong)(rong)(rong)量(liang)越(yue)大，ESR越(yue)低。在(zai)板卡設計中(zhong)采用多(duo)個(ge)小(xiao)電容(rong)(rong)(rong)并(bing)連(lian)多(duo)是出(chu)與PCB空間的限制(zhi)，這(zhe)樣(yang)有的人就認為，越(yue)多(duo)的并(bing)聯小(xiao)電阻(zu)，ESR越(yue)低，效果(guo)(guo)越(yue)好。理論上是如此(ci)，但是要(yao)考慮到電容(rong)(rong)(rong)接腳焊點(dian)的阻(zu)抗(kang)，采用多(duo)個(ge)小(xiao)電容(rong)(rong)(rong)并(bing)聯，效果(guo)(guo)并(bing)不一定(ding)突出(chu)。
3.ESR越低，效果越好。
結(jie)合我們(men)上面的(de)提高(gao)的(de)供電(dian)(dian)電(dian)(dian)路來說(shuo)，對于輸(shu)入電(dian)(dian)容(rong)(rong)來說(shuo)，輸(shu)入電(dian)(dian)容(rong)(rong)的(de)容(rong)(rong)量(liang)要(yao)(yao)大(da)一(yi)點(dian)(dian)。相(xiang)對容(rong)(rong)量(liang)的(de)要(yao)(yao)求，對ESR的(de)要(yao)(yao)求可(ke)以(yi)適當(dang)的(de)降低(di)。因為(wei)輸(shu)入電(dian)(dian)容(rong)(rong)主要(yao)(yao)是(shi)耐壓(ya)，其次是(shi)吸收(shou)MOSFET的(de)開(kai)關脈沖。對于輸(shu)出(chu)電(dian)(dian)容(rong)(rong)來說(shuo)，耐壓(ya)的(de)要(yao)(yao)求和容(rong)(rong)量(liang)可(ke)以(yi)適當(dang)的(de)降低(di)一(yi)點(dian)(dian)。ESR的(de)要(yao)(yao)求則高(gao)一(yi)點(dian)(dian)，因為(wei)這(zhe)里(li)要(yao)(yao)保證的(de)是(shi)足夠的(de)電(dian)(dian)流通過量(liang)。但這(zhe)里(li)要(yao)(yao)注意的(de)是(shi)ESR并不是(shi)越低(di)越好，低(di)ESR電(dian)(dian)容(rong)(rong)會引起(qi)開(kai)關電(dian)(dian)路振蕩。而消振電(dian)(dian)路復雜同時會導致成本的(de)增加(jia)。板(ban)卡設計中，這(zhe)里(li)一(yi)般有一(yi)個參考值，此作為(wei)元件選用參數(shu)，避免消振電(dian)(dian)路而導致成本的(de)增加(jia)。
4.好電容代表著(zhu)高品質。
“唯電(dian)容論”曾經盛(sheng)極一(yi)時，一(yi)些(xie)廠(chang)商和媒體(ti)也(ye)刻(ke)意(yi)(yi)的(de)(de)(de)把這(zhe)個(ge)事情做成一(yi)個(ge)賣點(dian)。在(zai)板卡(ka)設計(ji)中(zhong)，電(dian)路設計(ji)水平(ping)是關鍵。和有的(de)(de)(de)廠(chang)商可以用兩相供電(dian)做出(chu)比一(yi)些(xie)廠(chang)商采用四相供電(dian)更穩定的(de)(de)(de)產(chan)(chan)品一(yi)樣，一(yi)味(wei)的(de)(de)(de)采用高價電(dian)容，不一(yi)定能做出(chu)好產(chan)(chan)品。衡量一(yi)個(ge)產(chan)(chan)品，一(yi)定要全方(fang)位多角度(du)的(de)(de)(de)去(qu)考慮(lv)，切不可把電(dian)容的(de)(de)(de)作用有意(yi)(yi)無意(yi)(yi)的(de)(de)(de)夸大(da)。
B. 電(dian)容爆漿之(zhi)面(mian)面(mian)談(tan)
爆漿(jiang)的種類：
分兩類(lei)，輸(shu)(shu)入電容爆漿和輸(shu)(shu)出電容爆漿。
對于(yu)(yu)輸(shu)入(ru)電(dian)(dian)(dian)容來說，就(jiu)是我是說的(de)C1，C1對由電(dian)(dian)(dian)源(yuan)接收到的(de)電(dian)(dian)(dian)流進行過(guo)(guo)(guo)濾。輸(shu)入(ru)電(dian)(dian)(dian)容爆(bao)(bao)漿和電(dian)(dian)(dian)源(yuan)輸(shu)入(ru)電(dian)(dian)(dian)流的(de)品質(zhi)有關(guan)。過(guo)(guo)(guo)多的(de)毛刺電(dian)(dian)(dian)壓(ya)，峰值電(dian)(dian)(dian)壓(ya)過(guo)(guo)(guo)高，電(dian)(dian)(dian)流不穩定等都使電(dian)(dian)(dian)容過(guo)(guo)(guo)于(yu)(yu)充放電(dian)(dian)(dian)過(guo)(guo)(guo)于(yu)(yu)頻繁，長時間處于(yu)(yu)這類工(gong)作環境下的(de)電(dian)(dian)(dian)容，內部溫度升高很快。超過(guo)(guo)(guo)泄爆(bao)(bao)口的(de)承受極(ji)限就(jiu)會發生爆(bao)(bao)漿。
對于輸出(chu)電(dian)容(rong)來說，就我說的(de)C2，對經電(dian)源模塊調整后的(de)電(dian)流(liu)進行濾波。此處電(dian)流(liu)經過一次過濾，比較平穩(wen)，發(fa)生爆(bao)漿的(de)可能性相(xiang)對來說小了(le)不少。但如果環境溫(wen)度過高(gao)，電(dian)容(rong)同樣容(rong)易發(fa)生爆(bao)漿。爆(bao)，報也(ye)。采(cai)用垃(la)圾(ji)東(dong)西(xi)自然(ran)要爆(bao)，報應啊。欲知(zhi)(zhi)過去因者(zhe)(zhe)，見(jian)其(qi)現在果;欲知(zhi)(zhi)未來果者(zhe)(zhe)，見(jian)其(qi)現在因。
電解電容爆(bao)漿的原因：
電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)爆漿(jiang)的(de)(de)(de)(de)(de)原(yuan)因有很多(duo)，比如(ru)電(dian)(dian)(dian)(dian)(dian)流大(da)(da)于允許(xu)的(de)(de)(de)(de)(de)穩(wen)波(bo)電(dian)(dian)(dian)(dian)(dian)流、使(shi)(shi)用電(dian)(dian)(dian)(dian)(dian)壓(ya)超(chao)出工作電(dian)(dian)(dian)(dian)(dian)壓(ya)、逆向(xiang)電(dian)(dian)(dian)(dian)(dian)壓(ya)、頻繁的(de)(de)(de)(de)(de)充放(fang)電(dian)(dian)(dian)(dian)(dian)等。但(dan)是(shi)(shi)最(zui)直接(jie)的(de)(de)(de)(de)(de)原(yuan)因就(jiu)是(shi)(shi)高(gao)溫(wen)(wen)(wen)。我們(men)知道(dao)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)有一個重(zhong)要(yao)的(de)(de)(de)(de)(de)參數就(jiu)是(shi)(shi)耐溫(wen)(wen)(wen)值，指(zhi)的(de)(de)(de)(de)(de)就(jiu)是(shi)(shi)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)內部(bu)電(dian)(dian)(dian)(dian)(dian)解(jie)(jie)液(ye)的(de)(de)(de)(de)(de)沸點。當電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)的(de)(de)(de)(de)(de)內部(bu)溫(wen)(wen)(wen)度(du)(du)達到電(dian)(dian)(dian)(dian)(dian)解(jie)(jie)液(ye)的(de)(de)(de)(de)(de)沸點時(shi)，電(dian)(dian)(dian)(dian)(dian)解(jie)(jie)液(ye)開始沸騰，電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)內部(bu)的(de)(de)(de)(de)(de)壓(ya)力升(sheng)高(gao)，當壓(ya)力超(chao)過(guo)(guo)泄爆口的(de)(de)(de)(de)(de)承受極限就(jiu)發生(sheng)了(le)(le)爆漿(jiang)。所以說(shuo)溫(wen)(wen)(wen)度(du)(du)是(shi)(shi)導(dao)致電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)爆漿(jiang)的(de)(de)(de)(de)(de)直接(jie)原(yuan)因。電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)設(she)計使(shi)(shi)用壽命(ming)(ming)大(da)(da)約為2萬小時(shi)，受環境(jing)(jing)溫(wen)(wen)(wen)度(du)(du)的(de)(de)(de)(de)(de)影響也很大(da)(da)。電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)的(de)(de)(de)(de)(de)使(shi)(shi)用壽命(ming)(ming)隨溫(wen)(wen)(wen)度(du)(du)的(de)(de)(de)(de)(de)增加而(er)減小，實驗證(zheng)明環境(jing)(jing)溫(wen)(wen)(wen)度(du)(du)每升(sheng)高(gao)10℃，電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)的(de)(de)(de)(de)(de)壽命(ming)(ming)就(jiu)會(hui)減半。主要(yao)原(yuan)因就(jiu)是(shi)(shi)溫(wen)(wen)(wen)度(du)(du)加速化(hua)學(xue)反(fan)應(ying)而(er)使(shi)(shi)介質(zhi)隨時(shi)間退化(hua)失效，這樣電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)壽命(ming)(ming)終結。為了(le)(le)保證(zheng)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)的(de)(de)(de)(de)(de)穩(wen)定性，電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)在插板前(qian)要(yao)經過(guo)(guo)長時(shi)間的(de)(de)(de)(de)(de)高(gao)溫(wen)(wen)(wen)環境(jing)(jing)的(de)(de)(de)(de)(de)測試(shi)。即使(shi)(shi)是(shi)(shi)在100℃，高(gao)品(pin)質(zhi)的(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)也可(ke)以工作幾千個小時(shi)。同時(shi)，我們(men)提(ti)到的(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)的(de)(de)(de)(de)(de)壽命(ming)(ming)是(shi)(shi)指(zhi)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)在使(shi)(shi)用過(guo)(guo)程中，電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)容(rong)(rong)(rong)(rong)(rong)(rong)量不會(hui)超(chao)過(guo)(guo)標(biao)準范圍變化(hua)的(de)(de)(de)(de)(de)10%。電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)壽命(ming)(ming)指(zhi)的(de)(de)(de)(de)(de)是(shi)(shi)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)容(rong)(rong)(rong)(rong)(rong)(rong)量的(de)(de)(de)(de)(de)問題，而(er)不是(shi)(shi)設(she)計壽命(ming)(ming)到達之后(hou)就(jiu)發生(sheng)爆漿(jiang)。只(zhi)是(shi)(shi)無法保證(zheng)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)的(de)(de)(de)(de)(de)設(she)計的(de)(de)(de)(de)(de)容(rong)(rong)(rong)(rong)(rong)(rong)量標(biao)準。
所(suo)以，短(duan)時期內，正常使(shi)(shi)用的板卡(ka)電(dian)容(rong)(rong)就發生爆漿的情況(kuang)(kuang)，這就是電(dian)容(rong)(rong)品質(zhi)問題。另外(wai)，不(bu)正常的使(shi)(shi)用情況(kuang)(kuang)也(ye)有可能發生電(dian)容(rong)(rong)爆漿的情況(kuang)(kuang)。比(bi)如熱插拔電(dian)腦配件也(ye)會(hui)導(dao)致板卡(ka)局部電(dian)路電(dian)流(liu)、電(dian)壓(ya)的劇烈變化(hua)，從(cong)而引(yin)發電(dian)容(rong)(rong)使(shi)(shi)用故障。
1、應用于(yu)電(dian)源電(dian)路(lu)，實現旁(pang)路(lu)、去(qu)藕、濾(lv)波和儲能方(fang)面(mian)電(dian)容(rong)的作用，下面(mian)分類詳述(shu)之：
1)濾波(bo)
濾(lv)波是(shi)電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)(rong)的(de)(de)作用中很重(zhong)要的(de)(de)一(yi)部分。幾乎所有(you)的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)源電(dian)(dian)(dian)(dian)(dian)(dian)路中都(dou)會用到。從理論上(即假設電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)(rong)為(wei)純(chun)電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)(rong))說(shuo)，電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)(rong)越(yue)(yue)大(da)，阻(zu)(zu)抗越(yue)(yue)小(xiao)(xiao)，通(tong)(tong)(tong)過(guo)的(de)(de)頻(pin)率(lv)也(ye)越(yue)(yue)高(gao)。但實際上超(chao)過(guo)1uF的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)(rong)大(da)多為(wei)電(dian)(dian)(dian)(dian)(dian)(dian)解電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)(rong)，有(you)很大(da)的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)感成份(fen)，所以(yi)頻(pin)率(lv)高(gao)后反而阻(zu)(zu)抗會增大(da)。有(you)時(shi)會看到有(you)一(yi)個(ge)電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)(rong)量較(jiao)大(da)電(dian)(dian)(dian)(dian)(dian)(dian)解電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)(rong)并聯了一(yi)個(ge)小(xiao)(xiao)電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)(rong)，這時(shi)大(da)電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)(rong)通(tong)(tong)(tong)低(di)頻(pin)，小(xiao)(xiao)電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)(rong)通(tong)(tong)(tong)高(gao)頻(pin)。電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)(rong)的(de)(de)作用就是(shi)通(tong)(tong)(tong)高(gao)阻(zu)(zu)低(di)，通(tong)(tong)(tong)高(gao)頻(pin)阻(zu)(zu)低(di)頻(pin)。電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)(rong)越(yue)(yue)大(da)低(di)頻(pin)越(yue)(yue)容(rong)(rong)(rong)(rong)(rong)(rong)(rong)易通(tong)(tong)(tong)過(guo)，電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)(rong)越(yue)(yue)大(da)高(gao)頻(pin)越(yue)(yue)容(rong)(rong)(rong)(rong)(rong)(rong)(rong)易通(tong)(tong)(tong)過(guo)。具體用在濾(lv)波中,大(da)電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)(rong)(1000uF)濾(lv)低(di)頻(pin)，小(xiao)(xiao)電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)(rong)(20pF)濾(lv)高(gao)頻(pin)。
曾有網友將(jiang)濾波(bo)電(dian)容 比(bi)作“水塘”。由于電(dian)容的(de)兩(liang)端(duan)電(dian)壓(ya)不會突變(bian)，由此可知，信號頻率越(yue)高則衰減越(yue)大，可很形(xing)象的(de)說電(dian)容像個水塘，不會因幾滴水的(de)加(jia)入或蒸發而引起(qi)水量的(de)變(bian)化。 它(ta)把電(dian)壓(ya)的(de)變(bian)動轉化為電(dian)流的(de)變(bian)化，頻率越(yue)高，峰(feng)值(zhi)電(dian)流就越(yue)大，從而緩沖了(le)電(dian)壓(ya)。濾波(bo)就是(shi)充電(dian)，放電(dian)的(de)過程。
2)旁路(lu)
旁(pang)(pang)路(lu)電(dian)(dian)容是(shi)為(wei)本地(di)(di)(di)器(qi)(qi)件(jian)提(ti)供能(neng)量的(de)儲能(neng)器(qi)(qi)件(jian)，它能(neng)使(shi)穩(wen)壓器(qi)(qi)的(de)輸出均勻(yun)化，降低負載需求。就像(xiang)小型可充電(dian)(dian)電(dian)(dian)池一樣，旁(pang)(pang)路(lu)電(dian)(dian)容能(neng)夠(gou)被充電(dian)(dian)，并(bing)向器(qi)(qi)件(jian)進行(xing)放 電(dian)(dian)。為(wei)盡量減少阻抗(kang)，旁(pang)(pang)路(lu)電(dian)(dian)容要盡量靠近負載器(qi)(qi)件(jian)的(de)供電(dian)(dian)電(dian)(dian)源管腳和地(di)(di)(di)管腳。這能(neng)夠(gou)很好(hao)地(di)(di)(di)防止輸入值過大(da)而(er)導致的(de)地(di)(di)(di)電(dian)(dian)位抬(tai)高和噪聲。地(di)(di)(di)彈是(shi)地(di)(di)(di)連接處在通過大(da) 電(dian)(dian)流毛刺時的(de)電(dian)(dian)壓降。
3)去藕
去藕(ou)，又(you)稱解藕(ou)。從電(dian)(dian)(dian)(dian)路(lu)(lu)(lu)來說，總是(shi)(shi)可以區(qu)分為驅動的(de)(de)(de)(de)(de)源(yuan)和被驅動的(de)(de)(de)(de)(de)負載。如果負載電(dian)(dian)(dian)(dian)容(rong)(rong)(rong)比較(jiao)大(da)，驅動電(dian)(dian)(dian)(dian)路(lu)(lu)(lu)要把電(dian)(dian)(dian)(dian)容(rong)(rong)(rong)充電(dian)(dian)(dian)(dian)、放電(dian)(dian)(dian)(dian)，才能完成(cheng)信(xin)(xin)號(hao)的(de)(de)(de)(de)(de)跳變(bian)，在上(shang) 升沿(yan)比較(jiao)陡峭的(de)(de)(de)(de)(de)時候，電(dian)(dian)(dian)(dian)流(liu)(liu)比較(jiao)大(da)，這(zhe)樣驅動的(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)流(liu)(liu)就(jiu)會吸收很大(da)的(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)源(yuan)電(dian)(dian)(dian)(dian)流(liu)(liu)，由于電(dian)(dian)(dian)(dian)路(lu)(lu)(lu)中(zhong)的(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)感，電(dian)(dian)(dian)(dian)阻(特別(bie)是(shi)(shi)芯片管腳上(shang)的(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)感，會產生反彈)，這(zhe)種(zhong)電(dian)(dian)(dian)(dian)流(liu)(liu)相對 于正(zheng)常情況來說實際上(shang)就(jiu)是(shi)(shi)一(yi)種(zhong)噪聲，會影響前級的(de)(de)(de)(de)(de)正(zheng)常工作。這(zhe)就(jiu)是(shi)(shi)耦(ou)(ou)(ou)合(he)(he)(he)。去藕(ou)電(dian)(dian)(dian)(dian)容(rong)(rong)(rong)就(jiu)是(shi)(shi)起到(dao)一(yi)個電(dian)(dian)(dian)(dian)池的(de)(de)(de)(de)(de)作用，滿足驅動電(dian)(dian)(dian)(dian)路(lu)(lu)(lu)電(dian)(dian)(dian)(dian)流(liu)(liu)的(de)(de)(de)(de)(de)變(bian)化，避免相互間的(de)(de)(de)(de)(de)耦(ou)(ou)(ou)合(he)(he)(he)干(gan)(gan)擾。將(jiang)旁(pang)路(lu)(lu)(lu)電(dian)(dian)(dian)(dian)容(rong)(rong)(rong)和去藕(ou)電(dian)(dian)(dian)(dian)容(rong)(rong)(rong)結(jie)合(he)(he)(he)起來將(jiang)更容(rong)(rong)(rong)易理解。旁(pang)路(lu)(lu)(lu)電(dian)(dian)(dian)(dian)容(rong)(rong)(rong)實際也是(shi)(shi)去藕(ou)合(he)(he)(he)的(de)(de)(de)(de)(de)，只是(shi)(shi)旁(pang)路(lu)(lu)(lu)電(dian)(dian)(dian)(dian)容(rong)(rong)(rong)一(yi)般是(shi)(shi)指高(gao)頻(pin)(pin)旁(pang)路(lu)(lu)(lu)，也就(jiu)是(shi)(shi)給高(gao)頻(pin)(pin)的(de)(de)(de)(de)(de)開關噪聲提高(gao)一(yi)條低阻抗泄防(fang) 途徑。高(gao)頻(pin)(pin)旁(pang)路(lu)(lu)(lu)電(dian)(dian)(dian)(dian)容(rong)(rong)(rong)一(yi)般比較(jiao)小，根據諧振頻(pin)(pin)率(lv)一(yi)般是(shi)(shi)0.1u，0.01u等，而去耦(ou)(ou)(ou)合(he)(he)(he)電(dian)(dian)(dian)(dian)容(rong)(rong)(rong)一(yi)般比較(jiao)大(da)，是(shi)(shi)10uF或(huo)者(zhe)更大(da)，依據電(dian)(dian)(dian)(dian)路(lu)(lu)(lu)中(zhong)分布參數，以及驅動 電(dian)(dian)(dian)(dian)流(liu)(liu)的(de)(de)(de)(de)(de)變(bian)化大(da)小來確定(ding)。旁(pang)路(lu)(lu)(lu)是(shi)(shi)把輸入信(xin)(xin)號(hao)中(zhong)的(de)(de)(de)(de)(de)干(gan)(gan)擾作為濾(lv)除對象，而去耦(ou)(ou)(ou)是(shi)(shi)把輸出信(xin)(xin)號(hao)的(de)(de)(de)(de)(de)干(gan)(gan)擾作為濾(lv)除對象，防(fang)止干(gan)(gan)擾信(xin)(xin)號(hao)返(fan)回(hui)電(dian)(dian)(dian)(dian)源(yuan)。這(zhe)應該是(shi)(shi)他們(men)的(de)(de)(de)(de)(de)本質區(qu)別(bie)。
4)儲能(neng)
儲能型電(dian)(dian)(dian)容(rong)(rong)器通過整流器收集(ji)電(dian)(dian)(dian)荷，并將存(cun)儲的(de)(de)能量通過變換器引線(xian)傳送(song)至電(dian)(dian)(dian)源(yuan)的(de)(de)輸出端。電(dian)(dian)(dian)壓額定值(zhi)為40～450VDC、電(dian)(dian)(dian)容(rong)(rong)值(zhi)在(zai)220～150 000uF之間的(de)(de)鋁電(dian)(dian)(dian)解電(dian)(dian)(dian)容(rong)(rong)器(如EPCOS公司的(de)(de) B43504或(huo)B43505)是較為常用(yong)(yong)的(de)(de)。根據不同的(de)(de)電(dian)(dian)(dian)源(yuan)要求，器件(jian)有時(shi)會采用(yong)(yong)串聯(lian)、并聯(lian)或(huo)其(qi)組合的(de)(de)形式， 對于功率級超過10KW的(de)(de)電(dian)(dian)(dian)源(yuan)，通常采用(yong)(yong)體積較大(da)的(de)(de)罐形螺旋端子電(dian)(dian)(dian)容(rong)(rong)器。
2、應用于信號電路(lu)，主要完成耦(ou)合、振(zhen)蕩/同步及時間常(chang)數的(de)作用：
1)耦合
舉個例子(zi)來講，晶體管(guan)放大器發射極有(you)一個自(zi)給偏壓(ya)電(dian)(dian)阻，它同時(shi)又(you)使(shi)信(xin)號產生(sheng)壓(ya)降反饋(kui)到(dao)輸(shu)入端形成了輸(shu)入輸(shu)出信(xin)號耦(ou)合(he)，這(zhe)個電(dian)(dian)阻就是產生(sheng)了耦(ou)合(he)的元(yuan)件，如果在這(zhe)個電(dian)(dian)阻兩端并聯一個電(dian)(dian)容，由于適當容量的電(dian)(dian)容器對交流信(xin)號較小(xiao)的阻抗,這(zhe)樣(yang)就減小(xiao)了電(dian)(dian)阻產生(sheng)的耦(ou)合(he)效應，故(gu)稱此電(dian)(dian)容為(wei)去(qu)耦(ou)電(dian)(dian)容。
2)振蕩/同步(bu)
包括RC、LC振蕩器及晶體(ti)的負載電容(rong)都屬于這一范疇。
3)時間常(chang)數
這就是常見的(de)(de) R、C 串聯構成的(de)(de)積分電路。當輸(shu)(shu)入信號電壓(ya)加在輸(shu)(shu)入端時，電容(C)上的(de)(de)電壓(ya)逐漸(jian)上升(sheng)(sheng)。而其(qi)充電電流則隨著電壓(ya)的(de)(de)上升(sheng)(sheng)而減(jian)小。電流通過電阻(R)、電容(C)的(de)(de)特性通過下面的(de)(de)公(gong)式描述：
i = (V/R)e-(t/CR)
我們知道了(le)電容的作用(yong)以后(hou)下面來談談電容在使用(yong)中的注意事(shi)項
A. 什么是好電容。
1.電(dian)容(rong)容(rong)量越大越好。
很多人在(zai)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)的(de)(de)(de)(de)(de)(de)(de)替換中往往愛用大(da)(da)容(rong)(rong)(rong)(rong)量的(de)(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)。我們知道雖然電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)越(yue)(yue)大(da)(da)，為IC提供(gong)的(de)(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)流補(bu)償(chang)的(de)(de)(de)(de)(de)(de)(de)能(neng)(neng)力(li)(li)越(yue)(yue)強。且不說電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)容(rong)(rong)(rong)(rong)量的(de)(de)(de)(de)(de)(de)(de)增(zeng)(zeng)大(da)(da)帶來的(de)(de)(de)(de)(de)(de)(de)體積變大(da)(da)，增(zeng)(zeng)加成本的(de)(de)(de)(de)(de)(de)(de)同時還影響空氣(qi)流動和散熱。關鍵在(zai)于電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)上存在(zai)寄(ji)生(sheng)(sheng)電(dian)(dian)(dian)(dian)(dian)感，電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)放電(dian)(dian)(dian)(dian)(dian)回(hui)(hui)路會(hui)在(zai)某個頻點上發生(sheng)(sheng)諧振(zhen)。在(zai)諧振(zhen)點，電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)的(de)(de)(de)(de)(de)(de)(de)阻抗小(xiao)。因此放電(dian)(dian)(dian)(dian)(dian)回(hui)(hui)路的(de)(de)(de)(de)(de)(de)(de)阻抗最(zui)小(xiao)，補(bu)充能(neng)(neng)量的(de)(de)(de)(de)(de)(de)(de)效果也(ye)最(zui)好。但當(dang)頻率超過(guo)諧振(zhen)點時，放電(dian)(dian)(dian)(dian)(dian)回(hui)(hui)路的(de)(de)(de)(de)(de)(de)(de)阻抗開(kai)始增(zeng)(zeng)加，電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)提供(gong)電(dian)(dian)(dian)(dian)(dian)流能(neng)(neng)力(li)(li)便開(kai)始下降(jiang)。電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)的(de)(de)(de)(de)(de)(de)(de)容(rong)(rong)(rong)(rong)值(zhi)越(yue)(yue)大(da)(da)，諧振(zhen)頻率越(yue)(yue)低(di)，電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)能(neng)(neng)有(you)效補(bu)償(chang)電(dian)(dian)(dian)(dian)(dian)流的(de)(de)(de)(de)(de)(de)(de)頻率范圍也(ye)越(yue)(yue)小(xiao)。從保(bao)證電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)提供(gong)高頻電(dian)(dian)(dian)(dian)(dian)流的(de)(de)(de)(de)(de)(de)(de)能(neng)(neng)力(li)(li)的(de)(de)(de)(de)(de)(de)(de)角度(du)來說，電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)越(yue)(yue)大(da)(da)越(yue)(yue)好的(de)(de)(de)(de)(de)(de)(de)觀點是錯誤的(de)(de)(de)(de)(de)(de)(de)，一般的(de)(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)路設(she)計中都有(you)一個參考(kao)值(zhi)的(de)(de)(de)(de)(de)(de)(de)。
2.同樣容量的電容，并(bing)聯越(yue)多的小電容越(yue)好
耐壓值、耐溫(wen)值、容(rong)(rong)(rong)值、ESR(等(deng)效電阻(zu))等(deng)是電容(rong)(rong)(rong)的幾個(ge)重要(yao)參數，對于ESR自然是越(yue)低越(yue)好。ESR與電容(rong)(rong)(rong)的容(rong)(rong)(rong)量(liang)、頻(pin)率(lv)、電壓、溫(wen)度等(deng)都有關系。當電壓固定(ding)時候，容(rong)(rong)(rong)量(liang)越(yue)大，ESR越(yue)低。在(zai)板卡設計中(zhong)采用多(duo)個(ge)小(xiao)電容(rong)(rong)(rong)并(bing)連(lian)多(duo)是出(chu)與PCB空間的限制(zhi)，這(zhe)樣(yang)有的人就認為，越(yue)多(duo)的并(bing)聯小(xiao)電阻(zu)，ESR越(yue)低，效果(guo)(guo)越(yue)好。理論上是如此(ci)，但是要(yao)考慮到電容(rong)(rong)(rong)接腳焊點(dian)的阻(zu)抗(kang)，采用多(duo)個(ge)小(xiao)電容(rong)(rong)(rong)并(bing)聯，效果(guo)(guo)并(bing)不一定(ding)突出(chu)。
3.ESR越低，效果越好。
結(jie)合我們(men)上面的(de)提高(gao)的(de)供電(dian)(dian)電(dian)(dian)路來說(shuo)，對于輸(shu)入電(dian)(dian)容(rong)(rong)來說(shuo)，輸(shu)入電(dian)(dian)容(rong)(rong)的(de)容(rong)(rong)量(liang)要(yao)(yao)大(da)一(yi)點(dian)(dian)。相(xiang)對容(rong)(rong)量(liang)的(de)要(yao)(yao)求，對ESR的(de)要(yao)(yao)求可(ke)以(yi)適當(dang)的(de)降低(di)。因為(wei)輸(shu)入電(dian)(dian)容(rong)(rong)主要(yao)(yao)是(shi)耐壓(ya)，其次是(shi)吸收(shou)MOSFET的(de)開(kai)關脈沖。對于輸(shu)出(chu)電(dian)(dian)容(rong)(rong)來說(shuo)，耐壓(ya)的(de)要(yao)(yao)求和容(rong)(rong)量(liang)可(ke)以(yi)適當(dang)的(de)降低(di)一(yi)點(dian)(dian)。ESR的(de)要(yao)(yao)求則高(gao)一(yi)點(dian)(dian)，因為(wei)這(zhe)里(li)要(yao)(yao)保證的(de)是(shi)足夠的(de)電(dian)(dian)流通過量(liang)。但這(zhe)里(li)要(yao)(yao)注意的(de)是(shi)ESR并不是(shi)越低(di)越好，低(di)ESR電(dian)(dian)容(rong)(rong)會引起(qi)開(kai)關電(dian)(dian)路振蕩。而消振電(dian)(dian)路復雜同時會導致成本的(de)增加(jia)。板(ban)卡設計中，這(zhe)里(li)一(yi)般有一(yi)個參考值，此作為(wei)元件選用參數(shu)，避免消振電(dian)(dian)路而導致成本的(de)增加(jia)。
4.好電容代表著(zhu)高品質。
“唯電(dian)容論”曾經盛(sheng)極一(yi)時，一(yi)些(xie)廠(chang)商和媒體(ti)也(ye)刻(ke)意(yi)(yi)的(de)(de)(de)把這(zhe)個(ge)事情做成一(yi)個(ge)賣點(dian)。在(zai)板卡(ka)設計(ji)中(zhong)，電(dian)路設計(ji)水平(ping)是關鍵。和有的(de)(de)(de)廠(chang)商可以用兩相供電(dian)做出(chu)比一(yi)些(xie)廠(chang)商采用四相供電(dian)更穩定的(de)(de)(de)產(chan)(chan)品一(yi)樣，一(yi)味(wei)的(de)(de)(de)采用高價電(dian)容，不一(yi)定能做出(chu)好產(chan)(chan)品。衡量一(yi)個(ge)產(chan)(chan)品，一(yi)定要全方(fang)位多角度(du)的(de)(de)(de)去(qu)考慮(lv)，切不可把電(dian)容的(de)(de)(de)作用有意(yi)(yi)無意(yi)(yi)的(de)(de)(de)夸大(da)。
B. 電(dian)容爆漿之(zhi)面(mian)面(mian)談(tan)
爆漿(jiang)的種類：
分兩類(lei)，輸(shu)(shu)入電容爆漿和輸(shu)(shu)出電容爆漿。
對于(yu)(yu)輸(shu)入(ru)電(dian)(dian)(dian)容來說，就(jiu)是我是說的(de)C1，C1對由電(dian)(dian)(dian)源(yuan)接收到的(de)電(dian)(dian)(dian)流進行過(guo)(guo)(guo)濾。輸(shu)入(ru)電(dian)(dian)(dian)容爆(bao)(bao)漿和電(dian)(dian)(dian)源(yuan)輸(shu)入(ru)電(dian)(dian)(dian)流的(de)品質(zhi)有關(guan)。過(guo)(guo)(guo)多的(de)毛刺電(dian)(dian)(dian)壓(ya)，峰值電(dian)(dian)(dian)壓(ya)過(guo)(guo)(guo)高，電(dian)(dian)(dian)流不穩定等都使電(dian)(dian)(dian)容過(guo)(guo)(guo)于(yu)(yu)充放電(dian)(dian)(dian)過(guo)(guo)(guo)于(yu)(yu)頻繁，長時間處于(yu)(yu)這類工(gong)作環境下的(de)電(dian)(dian)(dian)容，內部溫度升高很快。超過(guo)(guo)(guo)泄爆(bao)(bao)口的(de)承受極(ji)限就(jiu)會發生爆(bao)(bao)漿。
對于輸出(chu)電(dian)容(rong)來說，就我說的(de)C2，對經電(dian)源模塊調整后的(de)電(dian)流(liu)進行濾波。此處電(dian)流(liu)經過一次過濾，比較平穩(wen)，發(fa)生爆(bao)漿的(de)可能性相(xiang)對來說小了(le)不少。但如果環境溫(wen)度過高(gao)，電(dian)容(rong)同樣容(rong)易發(fa)生爆(bao)漿。爆(bao)，報也(ye)。采(cai)用垃(la)圾(ji)東(dong)西(xi)自然(ran)要爆(bao)，報應啊。欲知(zhi)(zhi)過去因者(zhe)(zhe)，見(jian)其(qi)現在果;欲知(zhi)(zhi)未來果者(zhe)(zhe)，見(jian)其(qi)現在因。
電解電容爆(bao)漿的原因：
電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)爆漿(jiang)的(de)(de)(de)(de)(de)原(yuan)因有很多(duo)，比如(ru)電(dian)(dian)(dian)(dian)(dian)流大(da)(da)于允許(xu)的(de)(de)(de)(de)(de)穩(wen)波(bo)電(dian)(dian)(dian)(dian)(dian)流、使(shi)(shi)用電(dian)(dian)(dian)(dian)(dian)壓(ya)超(chao)出工作電(dian)(dian)(dian)(dian)(dian)壓(ya)、逆向(xiang)電(dian)(dian)(dian)(dian)(dian)壓(ya)、頻繁的(de)(de)(de)(de)(de)充放(fang)電(dian)(dian)(dian)(dian)(dian)等。但(dan)是(shi)(shi)最(zui)直接(jie)的(de)(de)(de)(de)(de)原(yuan)因就(jiu)是(shi)(shi)高(gao)溫(wen)(wen)(wen)。我們(men)知道(dao)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)有一個重(zhong)要(yao)的(de)(de)(de)(de)(de)參數就(jiu)是(shi)(shi)耐溫(wen)(wen)(wen)值，指(zhi)的(de)(de)(de)(de)(de)就(jiu)是(shi)(shi)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)內部(bu)電(dian)(dian)(dian)(dian)(dian)解(jie)(jie)液(ye)的(de)(de)(de)(de)(de)沸點。當電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)的(de)(de)(de)(de)(de)內部(bu)溫(wen)(wen)(wen)度(du)(du)達到電(dian)(dian)(dian)(dian)(dian)解(jie)(jie)液(ye)的(de)(de)(de)(de)(de)沸點時(shi)，電(dian)(dian)(dian)(dian)(dian)解(jie)(jie)液(ye)開始沸騰，電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)內部(bu)的(de)(de)(de)(de)(de)壓(ya)力升(sheng)高(gao)，當壓(ya)力超(chao)過(guo)(guo)泄爆口的(de)(de)(de)(de)(de)承受極限就(jiu)發生(sheng)了(le)(le)爆漿(jiang)。所以說(shuo)溫(wen)(wen)(wen)度(du)(du)是(shi)(shi)導(dao)致電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)爆漿(jiang)的(de)(de)(de)(de)(de)直接(jie)原(yuan)因。電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)設(she)計使(shi)(shi)用壽命(ming)(ming)大(da)(da)約為2萬小時(shi)，受環境(jing)(jing)溫(wen)(wen)(wen)度(du)(du)的(de)(de)(de)(de)(de)影響也很大(da)(da)。電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)的(de)(de)(de)(de)(de)使(shi)(shi)用壽命(ming)(ming)隨溫(wen)(wen)(wen)度(du)(du)的(de)(de)(de)(de)(de)增加而(er)減小，實驗證(zheng)明環境(jing)(jing)溫(wen)(wen)(wen)度(du)(du)每升(sheng)高(gao)10℃，電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)的(de)(de)(de)(de)(de)壽命(ming)(ming)就(jiu)會(hui)減半。主要(yao)原(yuan)因就(jiu)是(shi)(shi)溫(wen)(wen)(wen)度(du)(du)加速化(hua)學(xue)反(fan)應(ying)而(er)使(shi)(shi)介質(zhi)隨時(shi)間退化(hua)失效，這樣電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)壽命(ming)(ming)終結。為了(le)(le)保證(zheng)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)的(de)(de)(de)(de)(de)穩(wen)定性，電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)在插板前(qian)要(yao)經過(guo)(guo)長時(shi)間的(de)(de)(de)(de)(de)高(gao)溫(wen)(wen)(wen)環境(jing)(jing)的(de)(de)(de)(de)(de)測試(shi)。即使(shi)(shi)是(shi)(shi)在100℃，高(gao)品(pin)質(zhi)的(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)也可(ke)以工作幾千個小時(shi)。同時(shi)，我們(men)提(ti)到的(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)的(de)(de)(de)(de)(de)壽命(ming)(ming)是(shi)(shi)指(zhi)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)在使(shi)(shi)用過(guo)(guo)程中，電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)容(rong)(rong)(rong)(rong)(rong)(rong)量不會(hui)超(chao)過(guo)(guo)標(biao)準范圍變化(hua)的(de)(de)(de)(de)(de)10%。電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)壽命(ming)(ming)指(zhi)的(de)(de)(de)(de)(de)是(shi)(shi)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)容(rong)(rong)(rong)(rong)(rong)(rong)量的(de)(de)(de)(de)(de)問題，而(er)不是(shi)(shi)設(she)計壽命(ming)(ming)到達之后(hou)就(jiu)發生(sheng)爆漿(jiang)。只(zhi)是(shi)(shi)無法保證(zheng)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)的(de)(de)(de)(de)(de)設(she)計的(de)(de)(de)(de)(de)容(rong)(rong)(rong)(rong)(rong)(rong)量標(biao)準。
所(suo)以，短(duan)時期內，正常使(shi)(shi)用的板卡(ka)電(dian)容(rong)(rong)就發生爆漿的情況(kuang)(kuang)，這就是電(dian)容(rong)(rong)品質(zhi)問題。另外(wai)，不(bu)正常的使(shi)(shi)用情況(kuang)(kuang)也(ye)有可能發生電(dian)容(rong)(rong)爆漿的情況(kuang)(kuang)。比(bi)如熱插拔電(dian)腦配件也(ye)會(hui)導(dao)致板卡(ka)局部電(dian)路電(dian)流(liu)、電(dian)壓(ya)的劇烈變化(hua)，從(cong)而引(yin)發電(dian)容(rong)(rong)使(shi)(shi)用故障。
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