詳解電容在電源中所起到的作用
2019/7/1 12:46:11??????點擊：
作為無(wu)源元件之(zhi)一(yi)的電(dian)容，其(qi)作用不(bu)外(wai)乎以下(xia)幾(ji)種：
1、應用(yong)(yong)于電源(yuan)電路(lu)，實現(xian)旁路(lu)、去藕、濾波和儲能方面電容的作用(yong)(yong)，下面分類詳(xiang)述之(zhi)：
1)濾波
濾波是電(dian)(dian)(dian)(dian)容(rong)(rong)的作用(yong)中(zhong)很重要的一部(bu)分。幾乎所有(you)(you)的電(dian)(dian)(dian)(dian)源電(dian)(dian)(dian)(dian)路中(zhong)都會用(yong)到(dao)。從理論上(即假設電(dian)(dian)(dian)(dian)容(rong)(rong)為純電(dian)(dian)(dian)(dian)容(rong)(rong))說(shuo)，電(dian)(dian)(dian)(dian)容(rong)(rong)越(yue)大(da)，阻(zu)抗(kang)越(yue)小，通過的頻(pin)率也越(yue)高(gao)(gao)。但實際上超(chao)過1uF的電(dian)(dian)(dian)(dian)容(rong)(rong)大(da)多為電(dian)(dian)(dian)(dian)解電(dian)(dian)(dian)(dian)容(rong)(rong)，有(you)(you)很大(da)的電(dian)(dian)(dian)(dian)感成份，所以頻(pin)率高(gao)(gao)后反(fan)而阻(zu)抗(kang)會增(zeng)大(da)。有(you)(you)時會看(kan)到(dao)有(you)(you)一個(ge)電(dian)(dian)(dian)(dian)容(rong)(rong)量較大(da)電(dian)(dian)(dian)(dian)解電(dian)(dian)(dian)(dian)容(rong)(rong)并聯了一個(ge)小電(dian)(dian)(dian)(dian)容(rong)(rong)，這時大(da)電(dian)(dian)(dian)(dian)容(rong)(rong)通低(di)(di)頻(pin)，小電(dian)(dian)(dian)(dian)容(rong)(rong)通高(gao)(gao)頻(pin)。電(dian)(dian)(dian)(dian)容(rong)(rong)的作用(yong)就(jiu)是通高(gao)(gao)阻(zu)低(di)(di)，通高(gao)(gao)頻(pin)阻(zu)低(di)(di)頻(pin)。電(dian)(dian)(dian)(dian)容(rong)(rong)越(yue)大(da)低(di)(di)頻(pin)越(yue)容(rong)(rong)易通過，電(dian)(dian)(dian)(dian)容(rong)(rong)越(yue)大(da)高(gao)(gao)頻(pin)越(yue)容(rong)(rong)易通過。具體(ti)用(yong)在濾波中(zhong),大(da)電(dian)(dian)(dian)(dian)容(rong)(rong)(1000uF)濾低(di)(di)頻(pin)，小電(dian)(dian)(dian)(dian)容(rong)(rong)(20pF)濾高(gao)(gao)頻(pin)。
曾有網友將濾(lv)波電(dian)容 比作“水(shui)(shui)塘”。由(you)于電(dian)容的(de)(de)兩端(duan)電(dian)壓不會突變(bian)(bian)，由(you)此可知，信號頻(pin)率(lv)(lv)越(yue)高則(ze)衰減越(yue)大，可很(hen)形象的(de)(de)說電(dian)容像(xiang)個水(shui)(shui)塘，不會因幾滴水(shui)(shui)的(de)(de)加入或蒸(zheng)發而引(yin)起水(shui)(shui)量的(de)(de)變(bian)(bian)化(hua)。 它把(ba)電(dian)壓的(de)(de)變(bian)(bian)動(dong)轉化(hua)為電(dian)流(liu)的(de)(de)變(bian)(bian)化(hua)，頻(pin)率(lv)(lv)越(yue)高，峰值電(dian)流(liu)就越(yue)大，從而緩(huan)沖了電(dian)壓。濾(lv)波就是(shi)充電(dian)，放電(dian)的(de)(de)過程。
2)旁路
旁路(lu)電(dian)容是(shi)為本地器(qi)件提供(gong)能(neng)(neng)量(liang)的儲能(neng)(neng)器(qi)件，它(ta)能(neng)(neng)使穩壓(ya)器(qi)的輸出均勻(yun)化，降(jiang)低(di)負載需求(qiu)。就像小(xiao)型可充(chong)電(dian)電(dian)池一樣，旁路(lu)電(dian)容能(neng)(neng)夠被充(chong)電(dian)，并向器(qi)件進行放 電(dian)。為盡量(liang)減少阻抗，旁路(lu)電(dian)容要盡量(liang)靠近負載器(qi)件的供(gong)電(dian)電(dian)源管腳(jiao)和地管腳(jiao)。這能(neng)(neng)夠很好地防(fang)止輸入值過(guo)大而導致的地電(dian)位抬高和噪聲(sheng)。地彈是(shi)地連(lian)接處在通過(guo)大 電(dian)流毛刺時的電(dian)壓(ya)降(jiang)。
3)去藕
去(qu)藕(ou)，又稱(cheng)解藕(ou)。從電(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)(lu)來說，總是(shi)(shi)可以區分(fen)為驅(qu)動(dong)(dong)的(de)(de)(de)(de)(de)源和被驅(qu)動(dong)(dong)的(de)(de)(de)(de)(de)負載。如果負載電(dian)(dian)(dian)(dian)(dian)容(rong)比(bi)較大(da)(da)，驅(qu)動(dong)(dong)電(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)(lu)要把電(dian)(dian)(dian)(dian)(dian)容(rong)充(chong)電(dian)(dian)(dian)(dian)(dian)、放電(dian)(dian)(dian)(dian)(dian)，才能(neng)完(wan)成信(xin)(xin)號(hao)的(de)(de)(de)(de)(de)跳(tiao)變，在(zai)上 升沿比(bi)較陡峭的(de)(de)(de)(de)(de)時候(hou)，電(dian)(dian)(dian)(dian)(dian)流(liu)比(bi)較大(da)(da)，這(zhe)樣驅(qu)動(dong)(dong)的(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)流(liu)就(jiu)會(hui)吸收很大(da)(da)的(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)源電(dian)(dian)(dian)(dian)(dian)流(liu)，由(you)于電(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)(lu)中的(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)感(gan)，電(dian)(dian)(dian)(dian)(dian)阻(特(te)別是(shi)(shi)芯(xin)片(pian)管腳上的(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)感(gan)，會(hui)產生(sheng)反(fan)彈)，這(zhe)種電(dian)(dian)(dian)(dian)(dian)流(liu)相(xiang)對(dui) 于正常(chang)情(qing)況(kuang)來說實際上就(jiu)是(shi)(shi)一(yi)種噪聲，會(hui)影響前級的(de)(de)(de)(de)(de)正常(chang)工作(zuo)(zuo)。這(zhe)就(jiu)是(shi)(shi)耦(ou)合(he)。去(qu)藕(ou)電(dian)(dian)(dian)(dian)(dian)容(rong)就(jiu)是(shi)(shi)起到一(yi)個電(dian)(dian)(dian)(dian)(dian)池的(de)(de)(de)(de)(de)作(zuo)(zuo)用，滿足驅(qu)動(dong)(dong)電(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)(lu)電(dian)(dian)(dian)(dian)(dian)流(liu)的(de)(de)(de)(de)(de)變化(hua)，避免相(xiang)互間的(de)(de)(de)(de)(de)耦(ou)合(he)干擾。將旁(pang)路(lu)(lu)(lu)(lu)電(dian)(dian)(dian)(dian)(dian)容(rong)和去(qu)藕(ou)電(dian)(dian)(dian)(dian)(dian)容(rong)結合(he)起來將更(geng)(geng)容(rong)易理解。旁(pang)路(lu)(lu)(lu)(lu)電(dian)(dian)(dian)(dian)(dian)容(rong)實際也(ye)是(shi)(shi)去(qu)藕(ou)合(he)的(de)(de)(de)(de)(de)，只(zhi)是(shi)(shi)旁(pang)路(lu)(lu)(lu)(lu)電(dian)(dian)(dian)(dian)(dian)容(rong)一(yi)般(ban)(ban)(ban)是(shi)(shi)指(zhi)高頻旁(pang)路(lu)(lu)(lu)(lu)，也(ye)就(jiu)是(shi)(shi)給高頻的(de)(de)(de)(de)(de)開關噪聲提(ti)高一(yi)條低(di)阻抗泄防 途徑。高頻旁(pang)路(lu)(lu)(lu)(lu)電(dian)(dian)(dian)(dian)(dian)容(rong)一(yi)般(ban)(ban)(ban)比(bi)較小(xiao)，根據諧振頻率一(yi)般(ban)(ban)(ban)是(shi)(shi)0.1u，0.01u等，而(er)(er)去(qu)耦(ou)合(he)電(dian)(dian)(dian)(dian)(dian)容(rong)一(yi)般(ban)(ban)(ban)比(bi)較大(da)(da)，是(shi)(shi)10uF或者更(geng)(geng)大(da)(da)，依據電(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)(lu)中分(fen)布參數，以及驅(qu)動(dong)(dong) 電(dian)(dian)(dian)(dian)(dian)流(liu)的(de)(de)(de)(de)(de)變化(hua)大(da)(da)小(xiao)來確定。旁(pang)路(lu)(lu)(lu)(lu)是(shi)(shi)把輸入信(xin)(xin)號(hao)中的(de)(de)(de)(de)(de)干擾作(zuo)(zuo)為濾除對(dui)象，而(er)(er)去(qu)耦(ou)是(shi)(shi)把輸出信(xin)(xin)號(hao)的(de)(de)(de)(de)(de)干擾作(zuo)(zuo)為濾除對(dui)象，防止干擾信(xin)(xin)號(hao)返回(hui)電(dian)(dian)(dian)(dian)(dian)源。這(zhe)應該是(shi)(shi)他們的(de)(de)(de)(de)(de)本質(zhi)區別。
4)儲能
儲能(neng)型電(dian)(dian)(dian)容(rong)(rong)器(qi)(qi)通(tong)過(guo)整流(liu)器(qi)(qi)收集電(dian)(dian)(dian)荷，并將存儲的(de)(de)能(neng)量通(tong)過(guo)變換器(qi)(qi)引線傳送至(zhi)電(dian)(dian)(dian)源的(de)(de)輸出(chu)端。電(dian)(dian)(dian)壓額定值為(wei)40～450VDC、電(dian)(dian)(dian)容(rong)(rong)值在220～150 000uF之間的(de)(de)鋁電(dian)(dian)(dian)解電(dian)(dian)(dian)容(rong)(rong)器(qi)(qi)(如(ru)EPCOS公司的(de)(de) B43504或B43505)是較(jiao)為(wei)常用(yong)的(de)(de)。根據不同的(de)(de)電(dian)(dian)(dian)源要求，器(qi)(qi)件有時(shi)會采用(yong)串聯(lian)、并聯(lian)或其組合的(de)(de)形式， 對(dui)于功率(lv)級超過(guo)10KW的(de)(de)電(dian)(dian)(dian)源，通(tong)常采用(yong)體積較(jiao)大(da)的(de)(de)罐形螺(luo)旋(xuan)端子電(dian)(dian)(dian)容(rong)(rong)器(qi)(qi)。
2、應用于信號電(dian)路，主要完(wan)成耦合、振蕩/同步及時間常(chang)數(shu)的作用：
1)耦合
舉個(ge)例子來講，晶體管放(fang)大器(qi)發(fa)射(she)極有一個(ge)自給(gei)偏(pian)壓電(dian)(dian)阻(zu)，它(ta)同(tong)時又使(shi)信號(hao)產生(sheng)壓降(jiang)反饋到輸(shu)(shu)入端形成了輸(shu)(shu)入輸(shu)(shu)出信號(hao)耦(ou)(ou)合(he)(he)，這(zhe)個(ge)電(dian)(dian)阻(zu)就是(shi)產生(sheng)了耦(ou)(ou)合(he)(he)的元件，如果(guo)在(zai)這(zhe)個(ge)電(dian)(dian)阻(zu)兩端并聯(lian)一個(ge)電(dian)(dian)容(rong)(rong)，由(you)于適(shi)當容(rong)(rong)量的電(dian)(dian)容(rong)(rong)器(qi)對交流(liu)信號(hao)較小(xiao)的阻(zu)抗,這(zhe)樣(yang)就減小(xiao)了電(dian)(dian)阻(zu)產生(sheng)的耦(ou)(ou)合(he)(he)效(xiao)應，故稱此電(dian)(dian)容(rong)(rong)為去耦(ou)(ou)電(dian)(dian)容(rong)(rong)。
2)振蕩(dang)/同(tong)步
包括RC、LC振蕩器及晶體(ti)(ti)的負(fu)載電容都(dou)屬于這一(yi)范(fan)疇。
3)時間常數(shu)
這就是常見的 R、C 串聯(lian)構成的積分電(dian)(dian)路。當輸入(ru)信號電(dian)(dian)壓加在輸入(ru)端時，電(dian)(dian)容(rong)(C)上的電(dian)(dian)壓逐漸上升(sheng)。而其充(chong)電(dian)(dian)電(dian)(dian)流則(ze)隨著電(dian)(dian)壓的上升(sheng)而減小。電(dian)(dian)流通過電(dian)(dian)阻(R)、電(dian)(dian)容(rong)(C)的特性通過下(xia)面的公式描(miao)述：
i = (V/R)e-(t/CR)
我們知(zhi)道了電容(rong)的作用以(yi)后(hou)下面(mian)來談談電容(rong)在使用中的注意事項(xiang)
A. 什(shen)么是好電容。
1.電(dian)容容量越大越好(hao)。
很多人在電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)的(de)(de)(de)(de)替換中(zhong)往(wang)往(wang)愛(ai)用(yong)大(da)容(rong)(rong)(rong)量的(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)。我們知道雖然電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)越(yue)(yue)大(da)，為IC提供(gong)的(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)補償的(de)(de)(de)(de)能(neng)(neng)力越(yue)(yue)強。且不說(shuo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)容(rong)(rong)(rong)量的(de)(de)(de)(de)增(zeng)大(da)帶來的(de)(de)(de)(de)體積變大(da)，增(zeng)加成(cheng)本的(de)(de)(de)(de)同時還(huan)影響空氣流(liu)動(dong)和散熱(re)。關鍵在于電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)上(shang)存在寄生電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)感，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)放(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)回(hui)路會在某個頻點上(shang)發生諧(xie)(xie)振(zhen)。在諧(xie)(xie)振(zhen)點，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)的(de)(de)(de)(de)阻抗(kang)小(xiao)。因此放(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)回(hui)路的(de)(de)(de)(de)阻抗(kang)最小(xiao)，補充能(neng)(neng)量的(de)(de)(de)(de)效(xiao)果也(ye)最好(hao)。但當頻率超過(guo)諧(xie)(xie)振(zhen)點時，放(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)回(hui)路的(de)(de)(de)(de)阻抗(kang)開始(shi)增(zeng)加，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)提供(gong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)能(neng)(neng)力便開始(shi)下降。電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)的(de)(de)(de)(de)容(rong)(rong)(rong)值越(yue)(yue)大(da)，諧(xie)(xie)振(zhen)頻率越(yue)(yue)低(di)，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)能(neng)(neng)有(you)效(xiao)補償電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)的(de)(de)(de)(de)頻率范圍也(ye)越(yue)(yue)小(xiao)。從保證(zheng)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)提供(gong)高頻電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)的(de)(de)(de)(de)能(neng)(neng)力的(de)(de)(de)(de)角度來說(shuo)，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)越(yue)(yue)大(da)越(yue)(yue)好(hao)的(de)(de)(de)(de)觀點是錯誤的(de)(de)(de)(de)，一(yi)般的(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路設計中(zhong)都(dou)有(you)一(yi)個參(can)考值的(de)(de)(de)(de)。
2.同(tong)樣容(rong)(rong)量的電容(rong)(rong)，并聯越多的小電容(rong)(rong)越好
耐壓值(zhi)(zhi)、耐溫值(zhi)(zhi)、容(rong)(rong)值(zhi)(zhi)、ESR(等(deng)效電阻(zu))等(deng)是(shi)(shi)電容(rong)(rong)的幾個重(zhong)要參數，對于ESR自然是(shi)(shi)越(yue)(yue)低(di)越(yue)(yue)好。ESR與電容(rong)(rong)的容(rong)(rong)量(liang)、頻率、電壓、溫度等(deng)都有關系。當(dang)電壓固定(ding)(ding)時(shi)候，容(rong)(rong)量(liang)越(yue)(yue)大，ESR越(yue)(yue)低(di)。在板卡設(she)計中(zhong)采(cai)用多個小電容(rong)(rong)并連多是(shi)(shi)出(chu)與PCB空間的限制，這樣有的人就認(ren)為，越(yue)(yue)多的并聯(lian)小電阻(zu)，ESR越(yue)(yue)低(di)，效果越(yue)(yue)好。理論上是(shi)(shi)如此，但是(shi)(shi)要考慮到(dao)電容(rong)(rong)接腳(jiao)焊點的阻(zu)抗，采(cai)用多個小電容(rong)(rong)并聯(lian)，效果并不一(yi)定(ding)(ding)突出(chu)。
3.ESR越(yue)低，效(xiao)果越(yue)好(hao)。
結(jie)合我(wo)們上面的(de)(de)(de)(de)提(ti)高的(de)(de)(de)(de)供電(dian)電(dian)路來說(shuo)，對(dui)于輸入(ru)電(dian)容(rong)來說(shuo)，輸入(ru)電(dian)容(rong)的(de)(de)(de)(de)容(rong)量要(yao)大(da)一點(dian)。相對(dui)容(rong)量的(de)(de)(de)(de)要(yao)求，對(dui)ESR的(de)(de)(de)(de)要(yao)求可以適當的(de)(de)(de)(de)降低。因(yin)(yin)為輸入(ru)電(dian)容(rong)主要(yao)是耐壓(ya)，其次是吸收(shou)MOSFET的(de)(de)(de)(de)開(kai)關脈沖。對(dui)于輸出電(dian)容(rong)來說(shuo)，耐壓(ya)的(de)(de)(de)(de)要(yao)求和(he)容(rong)量可以適當的(de)(de)(de)(de)降低一點(dian)。ESR的(de)(de)(de)(de)要(yao)求則高一點(dian)，因(yin)(yin)為這(zhe)里要(yao)保(bao)證(zheng)的(de)(de)(de)(de)是足夠的(de)(de)(de)(de)電(dian)流通過量。但這(zhe)里要(yao)注意的(de)(de)(de)(de)是ESR并不是越低越好，低ESR電(dian)容(rong)會引(yin)起(qi)開(kai)關電(dian)路振(zhen)蕩(dang)。而(er)消(xiao)振(zhen)電(dian)路復雜同(tong)時會導致(zhi)成本(ben)的(de)(de)(de)(de)增加。板卡(ka)設計中，這(zhe)里一般有(you)一個(ge)參(can)考(kao)值，此作為元件選用參(can)數，避免消(xiao)振(zhen)電(dian)路而(er)導致(zhi)成本(ben)的(de)(de)(de)(de)增加。
4.好電容代表著高品質(zhi)。
“唯電(dian)容(rong)論”曾經盛極一(yi)時，一(yi)些廠(chang)商(shang)和媒體(ti)也刻意(yi)的(de)把這(zhe)個(ge)事情做(zuo)成一(yi)個(ge)賣(mai)點(dian)。在(zai)板卡(ka)設計(ji)中，電(dian)路設計(ji)水平是(shi)關鍵(jian)。和有(you)的(de)廠(chang)商(shang)可以(yi)用(yong)(yong)(yong)兩(liang)相供電(dian)做(zuo)出比一(yi)些廠(chang)商(shang)采用(yong)(yong)(yong)四相供電(dian)更(geng)穩定(ding)的(de)產(chan)(chan)品一(yi)樣，一(yi)味的(de)采用(yong)(yong)(yong)高價電(dian)容(rong)，不一(yi)定(ding)能做(zuo)出好產(chan)(chan)品。衡量一(yi)個(ge)產(chan)(chan)品，一(yi)定(ding)要全方位多角度的(de)去考慮(lv)，切不可把電(dian)容(rong)的(de)作(zuo)用(yong)(yong)(yong)有(you)意(yi)無(wu)意(yi)的(de)夸(kua)大。
B. 電容爆漿之面面談(tan)
爆漿(jiang)的種類：
分兩類，輸入電容(rong)爆漿(jiang)和輸出電容(rong)爆漿(jiang)。
對于輸入(ru)(ru)(ru)電(dian)(dian)(dian)容(rong)(rong)來(lai)說(shuo)，就是我(wo)是說(shuo)的C1，C1對由電(dian)(dian)(dian)源接收到的電(dian)(dian)(dian)流進行過(guo)(guo)(guo)濾。輸入(ru)(ru)(ru)電(dian)(dian)(dian)容(rong)(rong)爆漿(jiang)和電(dian)(dian)(dian)源輸入(ru)(ru)(ru)電(dian)(dian)(dian)流的品質有(you)關。過(guo)(guo)(guo)多(duo)的毛刺電(dian)(dian)(dian)壓(ya)，峰值電(dian)(dian)(dian)壓(ya)過(guo)(guo)(guo)高(gao)，電(dian)(dian)(dian)流不穩(wen)定等都使電(dian)(dian)(dian)容(rong)(rong)過(guo)(guo)(guo)于充(chong)放電(dian)(dian)(dian)過(guo)(guo)(guo)于頻繁，長時間處于這類工作環境下的電(dian)(dian)(dian)容(rong)(rong)，內部溫度(du)升高(gao)很快。超(chao)過(guo)(guo)(guo)泄爆口(kou)的承受(shou)極限就會(hui)發生爆漿(jiang)。
對(dui)(dui)于(yu)輸出電(dian)容(rong)來(lai)說，就我說的(de)C2，對(dui)(dui)經電(dian)源模塊調(diao)整后的(de)電(dian)流進行濾波。此處電(dian)流經過一次過濾，比較平穩，發生(sheng)爆(bao)漿的(de)可能性相對(dui)(dui)來(lai)說小(xiao)了不少。但如果環境溫度過高，電(dian)容(rong)同樣容(rong)易(yi)發生(sheng)爆(bao)漿。爆(bao)，報(bao)也。采用(yong)垃圾東西自然要爆(bao)，報(bao)應啊(a)。欲知過去因者，見其(qi)(qi)現(xian)(xian)在果;欲知未來(lai)果者，見其(qi)(qi)現(xian)(xian)在因。
電解電容爆漿的原因：
電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)爆漿(jiang)(jiang)(jiang)的(de)(de)(de)(de)(de)(de)(de)原(yuan)因(yin)有很(hen)多，比如電(dian)(dian)(dian)(dian)(dian)流大(da)(da)于允許的(de)(de)(de)(de)(de)(de)(de)穩波電(dian)(dian)(dian)(dian)(dian)流、使(shi)用電(dian)(dian)(dian)(dian)(dian)壓超(chao)出工(gong)作電(dian)(dian)(dian)(dian)(dian)壓、逆向電(dian)(dian)(dian)(dian)(dian)壓、頻(pin)繁的(de)(de)(de)(de)(de)(de)(de)充(chong)放(fang)電(dian)(dian)(dian)(dian)(dian)等。但是(shi)(shi)(shi)(shi)(shi)最直接的(de)(de)(de)(de)(de)(de)(de)原(yuan)因(yin)就(jiu)是(shi)(shi)(shi)(shi)(shi)高(gao)(gao)溫(wen)。我們知道電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)有一個(ge)重(zhong)要的(de)(de)(de)(de)(de)(de)(de)參數(shu)就(jiu)是(shi)(shi)(shi)(shi)(shi)耐(nai)溫(wen)值(zhi)，指的(de)(de)(de)(de)(de)(de)(de)就(jiu)是(shi)(shi)(shi)(shi)(shi)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)內部電(dian)(dian)(dian)(dian)(dian)解液的(de)(de)(de)(de)(de)(de)(de)沸點(dian)。當電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)的(de)(de)(de)(de)(de)(de)(de)內部溫(wen)度(du)達(da)到(dao)(dao)電(dian)(dian)(dian)(dian)(dian)解液的(de)(de)(de)(de)(de)(de)(de)沸點(dian)時(shi)(shi)，電(dian)(dian)(dian)(dian)(dian)解液開始沸騰，電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)內部的(de)(de)(de)(de)(de)(de)(de)壓力(li)升(sheng)高(gao)(gao)，當壓力(li)超(chao)過(guo)泄(xie)爆口的(de)(de)(de)(de)(de)(de)(de)承受極限就(jiu)發生了爆漿(jiang)(jiang)(jiang)。所以說(shuo)溫(wen)度(du)是(shi)(shi)(shi)(shi)(shi)導致電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)爆漿(jiang)(jiang)(jiang)的(de)(de)(de)(de)(de)(de)(de)直接原(yuan)因(yin)。電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)設計使(shi)用壽(shou)(shou)(shou)命(ming)(ming)大(da)(da)約為(wei)2萬小時(shi)(shi)，受環(huan)(huan)境(jing)溫(wen)度(du)的(de)(de)(de)(de)(de)(de)(de)影(ying)響也很(hen)大(da)(da)。電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)的(de)(de)(de)(de)(de)(de)(de)使(shi)用壽(shou)(shou)(shou)命(ming)(ming)隨溫(wen)度(du)的(de)(de)(de)(de)(de)(de)(de)增(zeng)加(jia)而(er)減(jian)小，實驗證(zheng)明環(huan)(huan)境(jing)溫(wen)度(du)每(mei)升(sheng)高(gao)(gao)10℃，電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)的(de)(de)(de)(de)(de)(de)(de)壽(shou)(shou)(shou)命(ming)(ming)就(jiu)會減(jian)半(ban)。主要原(yuan)因(yin)就(jiu)是(shi)(shi)(shi)(shi)(shi)溫(wen)度(du)加(jia)速化(hua)學反應而(er)使(shi)介質(zhi)隨時(shi)(shi)間(jian)退化(hua)失效，這樣電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)壽(shou)(shou)(shou)命(ming)(ming)終結。為(wei)了保證(zheng)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)的(de)(de)(de)(de)(de)(de)(de)穩定性，電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)在插板前要經過(guo)長時(shi)(shi)間(jian)的(de)(de)(de)(de)(de)(de)(de)高(gao)(gao)溫(wen)環(huan)(huan)境(jing)的(de)(de)(de)(de)(de)(de)(de)測試。即使(shi)是(shi)(shi)(shi)(shi)(shi)在100℃，高(gao)(gao)品質(zhi)的(de)(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)也可以工(gong)作幾(ji)千個(ge)小時(shi)(shi)。同(tong)時(shi)(shi)，我們提到(dao)(dao)的(de)(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)的(de)(de)(de)(de)(de)(de)(de)壽(shou)(shou)(shou)命(ming)(ming)是(shi)(shi)(shi)(shi)(shi)指電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)在使(shi)用過(guo)程中(zhong)，電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)容(rong)(rong)(rong)(rong)(rong)(rong)量不(bu)會超(chao)過(guo)標(biao)準范圍變化(hua)的(de)(de)(de)(de)(de)(de)(de)10%。電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)壽(shou)(shou)(shou)命(ming)(ming)指的(de)(de)(de)(de)(de)(de)(de)是(shi)(shi)(shi)(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)(de)(de)問題，而(er)不(bu)是(shi)(shi)(shi)(shi)(shi)設計壽(shou)(shou)(shou)命(ming)(ming)到(dao)(dao)達(da)之后就(jiu)發生爆漿(jiang)(jiang)(jiang)。只是(shi)(shi)(shi)(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)(de)(de)設計的(de)(de)(de)(de)(de)(de)(de)容(rong)(rong)(rong)(rong)(rong)(rong)量標(biao)準。
所(suo)以，短時期內，正(zheng)常使用(yong)(yong)(yong)的(de)板卡電容就(jiu)發生爆(bao)漿的(de)情況，這(zhe)就(jiu)是電容品質(zhi)問題。另外，不正(zheng)常的(de)使用(yong)(yong)(yong)情況也有可(ke)能發生電容爆(bao)漿的(de)情況。比(bi)如熱(re)插拔(ba)電腦配件也會導致板卡局(ju)部電路電流、電壓(ya)的(de)劇烈變化，從而引發電容使用(yong)(yong)(yong)故障。
1、應用(yong)(yong)于電源(yuan)電路(lu)，實現(xian)旁路(lu)、去藕、濾波和儲能方面電容的作用(yong)(yong)，下面分類詳(xiang)述之(zhi)：
1)濾波
濾波是電(dian)(dian)(dian)(dian)容(rong)(rong)的作用(yong)中(zhong)很重要的一部(bu)分。幾乎所有(you)(you)的電(dian)(dian)(dian)(dian)源電(dian)(dian)(dian)(dian)路中(zhong)都會用(yong)到(dao)。從理論上(即假設電(dian)(dian)(dian)(dian)容(rong)(rong)為純電(dian)(dian)(dian)(dian)容(rong)(rong))說(shuo)，電(dian)(dian)(dian)(dian)容(rong)(rong)越(yue)大(da)，阻(zu)抗(kang)越(yue)小，通過的頻(pin)率也越(yue)高(gao)(gao)。但實際上超(chao)過1uF的電(dian)(dian)(dian)(dian)容(rong)(rong)大(da)多為電(dian)(dian)(dian)(dian)解電(dian)(dian)(dian)(dian)容(rong)(rong)，有(you)(you)很大(da)的電(dian)(dian)(dian)(dian)感成份，所以頻(pin)率高(gao)(gao)后反(fan)而阻(zu)抗(kang)會增(zeng)大(da)。有(you)(you)時會看(kan)到(dao)有(you)(you)一個(ge)電(dian)(dian)(dian)(dian)容(rong)(rong)量較大(da)電(dian)(dian)(dian)(dian)解電(dian)(dian)(dian)(dian)容(rong)(rong)并聯了一個(ge)小電(dian)(dian)(dian)(dian)容(rong)(rong)，這時大(da)電(dian)(dian)(dian)(dian)容(rong)(rong)通低(di)(di)頻(pin)，小電(dian)(dian)(dian)(dian)容(rong)(rong)通高(gao)(gao)頻(pin)。電(dian)(dian)(dian)(dian)容(rong)(rong)的作用(yong)就(jiu)是通高(gao)(gao)阻(zu)低(di)(di)，通高(gao)(gao)頻(pin)阻(zu)低(di)(di)頻(pin)。電(dian)(dian)(dian)(dian)容(rong)(rong)越(yue)大(da)低(di)(di)頻(pin)越(yue)容(rong)(rong)易通過，電(dian)(dian)(dian)(dian)容(rong)(rong)越(yue)大(da)高(gao)(gao)頻(pin)越(yue)容(rong)(rong)易通過。具體(ti)用(yong)在濾波中(zhong),大(da)電(dian)(dian)(dian)(dian)容(rong)(rong)(1000uF)濾低(di)(di)頻(pin)，小電(dian)(dian)(dian)(dian)容(rong)(rong)(20pF)濾高(gao)(gao)頻(pin)。
曾有網友將濾(lv)波電(dian)容 比作“水(shui)(shui)塘”。由(you)于電(dian)容的(de)(de)兩端(duan)電(dian)壓不會突變(bian)(bian)，由(you)此可知，信號頻(pin)率(lv)(lv)越(yue)高則(ze)衰減越(yue)大，可很(hen)形象的(de)(de)說電(dian)容像(xiang)個水(shui)(shui)塘，不會因幾滴水(shui)(shui)的(de)(de)加入或蒸(zheng)發而引(yin)起水(shui)(shui)量的(de)(de)變(bian)(bian)化(hua)。 它把(ba)電(dian)壓的(de)(de)變(bian)(bian)動(dong)轉化(hua)為電(dian)流(liu)的(de)(de)變(bian)(bian)化(hua)，頻(pin)率(lv)(lv)越(yue)高，峰值電(dian)流(liu)就越(yue)大，從而緩(huan)沖了電(dian)壓。濾(lv)波就是(shi)充電(dian)，放電(dian)的(de)(de)過程。
2)旁路
旁路(lu)電(dian)容是(shi)為本地器(qi)件提供(gong)能(neng)(neng)量(liang)的儲能(neng)(neng)器(qi)件，它(ta)能(neng)(neng)使穩壓(ya)器(qi)的輸出均勻(yun)化，降(jiang)低(di)負載需求(qiu)。就像小(xiao)型可充(chong)電(dian)電(dian)池一樣，旁路(lu)電(dian)容能(neng)(neng)夠被充(chong)電(dian)，并向器(qi)件進行放 電(dian)。為盡量(liang)減少阻抗，旁路(lu)電(dian)容要盡量(liang)靠近負載器(qi)件的供(gong)電(dian)電(dian)源管腳(jiao)和地管腳(jiao)。這能(neng)(neng)夠很好地防(fang)止輸入值過(guo)大而導致的地電(dian)位抬高和噪聲(sheng)。地彈是(shi)地連(lian)接處在通過(guo)大 電(dian)流毛刺時的電(dian)壓(ya)降(jiang)。
3)去藕
去(qu)藕(ou)，又稱(cheng)解藕(ou)。從電(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)(lu)來說，總是(shi)(shi)可以區分(fen)為驅(qu)動(dong)(dong)的(de)(de)(de)(de)(de)源和被驅(qu)動(dong)(dong)的(de)(de)(de)(de)(de)負載。如果負載電(dian)(dian)(dian)(dian)(dian)容(rong)比(bi)較大(da)(da)，驅(qu)動(dong)(dong)電(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)(lu)要把電(dian)(dian)(dian)(dian)(dian)容(rong)充(chong)電(dian)(dian)(dian)(dian)(dian)、放電(dian)(dian)(dian)(dian)(dian)，才能(neng)完(wan)成信(xin)(xin)號(hao)的(de)(de)(de)(de)(de)跳(tiao)變，在(zai)上 升沿比(bi)較陡峭的(de)(de)(de)(de)(de)時候(hou)，電(dian)(dian)(dian)(dian)(dian)流(liu)比(bi)較大(da)(da)，這(zhe)樣驅(qu)動(dong)(dong)的(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)流(liu)就(jiu)會(hui)吸收很大(da)(da)的(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)源電(dian)(dian)(dian)(dian)(dian)流(liu)，由(you)于電(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)(lu)中的(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)感(gan)，電(dian)(dian)(dian)(dian)(dian)阻(特(te)別是(shi)(shi)芯(xin)片(pian)管腳上的(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)感(gan)，會(hui)產生(sheng)反(fan)彈)，這(zhe)種電(dian)(dian)(dian)(dian)(dian)流(liu)相(xiang)對(dui) 于正常(chang)情(qing)況(kuang)來說實際上就(jiu)是(shi)(shi)一(yi)種噪聲，會(hui)影響前級的(de)(de)(de)(de)(de)正常(chang)工作(zuo)(zuo)。這(zhe)就(jiu)是(shi)(shi)耦(ou)合(he)。去(qu)藕(ou)電(dian)(dian)(dian)(dian)(dian)容(rong)就(jiu)是(shi)(shi)起到一(yi)個電(dian)(dian)(dian)(dian)(dian)池的(de)(de)(de)(de)(de)作(zuo)(zuo)用，滿足驅(qu)動(dong)(dong)電(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)(lu)電(dian)(dian)(dian)(dian)(dian)流(liu)的(de)(de)(de)(de)(de)變化(hua)，避免相(xiang)互間的(de)(de)(de)(de)(de)耦(ou)合(he)干擾。將旁(pang)路(lu)(lu)(lu)(lu)電(dian)(dian)(dian)(dian)(dian)容(rong)和去(qu)藕(ou)電(dian)(dian)(dian)(dian)(dian)容(rong)結合(he)起來將更(geng)(geng)容(rong)易理解。旁(pang)路(lu)(lu)(lu)(lu)電(dian)(dian)(dian)(dian)(dian)容(rong)實際也(ye)是(shi)(shi)去(qu)藕(ou)合(he)的(de)(de)(de)(de)(de)，只(zhi)是(shi)(shi)旁(pang)路(lu)(lu)(lu)(lu)電(dian)(dian)(dian)(dian)(dian)容(rong)一(yi)般(ban)(ban)(ban)是(shi)(shi)指(zhi)高頻旁(pang)路(lu)(lu)(lu)(lu)，也(ye)就(jiu)是(shi)(shi)給高頻的(de)(de)(de)(de)(de)開關噪聲提(ti)高一(yi)條低(di)阻抗泄防 途徑。高頻旁(pang)路(lu)(lu)(lu)(lu)電(dian)(dian)(dian)(dian)(dian)容(rong)一(yi)般(ban)(ban)(ban)比(bi)較小(xiao)，根據諧振頻率一(yi)般(ban)(ban)(ban)是(shi)(shi)0.1u，0.01u等，而(er)(er)去(qu)耦(ou)合(he)電(dian)(dian)(dian)(dian)(dian)容(rong)一(yi)般(ban)(ban)(ban)比(bi)較大(da)(da)，是(shi)(shi)10uF或者更(geng)(geng)大(da)(da)，依據電(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)(lu)中分(fen)布參數，以及驅(qu)動(dong)(dong) 電(dian)(dian)(dian)(dian)(dian)流(liu)的(de)(de)(de)(de)(de)變化(hua)大(da)(da)小(xiao)來確定。旁(pang)路(lu)(lu)(lu)(lu)是(shi)(shi)把輸入信(xin)(xin)號(hao)中的(de)(de)(de)(de)(de)干擾作(zuo)(zuo)為濾除對(dui)象，而(er)(er)去(qu)耦(ou)是(shi)(shi)把輸出信(xin)(xin)號(hao)的(de)(de)(de)(de)(de)干擾作(zuo)(zuo)為濾除對(dui)象，防止干擾信(xin)(xin)號(hao)返回(hui)電(dian)(dian)(dian)(dian)(dian)源。這(zhe)應該是(shi)(shi)他們的(de)(de)(de)(de)(de)本質(zhi)區別。
4)儲能
儲能(neng)型電(dian)(dian)(dian)容(rong)(rong)器(qi)(qi)通(tong)過(guo)整流(liu)器(qi)(qi)收集電(dian)(dian)(dian)荷，并將存儲的(de)(de)能(neng)量通(tong)過(guo)變換器(qi)(qi)引線傳送至(zhi)電(dian)(dian)(dian)源的(de)(de)輸出(chu)端。電(dian)(dian)(dian)壓額定值為(wei)40～450VDC、電(dian)(dian)(dian)容(rong)(rong)值在220～150 000uF之間的(de)(de)鋁電(dian)(dian)(dian)解電(dian)(dian)(dian)容(rong)(rong)器(qi)(qi)(如(ru)EPCOS公司的(de)(de) B43504或B43505)是較(jiao)為(wei)常用(yong)的(de)(de)。根據不同的(de)(de)電(dian)(dian)(dian)源要求，器(qi)(qi)件有時(shi)會采用(yong)串聯(lian)、并聯(lian)或其組合的(de)(de)形式， 對(dui)于功率(lv)級超過(guo)10KW的(de)(de)電(dian)(dian)(dian)源，通(tong)常采用(yong)體積較(jiao)大(da)的(de)(de)罐形螺(luo)旋(xuan)端子電(dian)(dian)(dian)容(rong)(rong)器(qi)(qi)。
2、應用于信號電(dian)路，主要完(wan)成耦合、振蕩/同步及時間常(chang)數(shu)的作用：
1)耦合
舉個(ge)例子來講，晶體管放(fang)大器(qi)發(fa)射(she)極有一個(ge)自給(gei)偏(pian)壓電(dian)(dian)阻(zu)，它(ta)同(tong)時又使(shi)信號(hao)產生(sheng)壓降(jiang)反饋到輸(shu)(shu)入端形成了輸(shu)(shu)入輸(shu)(shu)出信號(hao)耦(ou)(ou)合(he)(he)，這(zhe)個(ge)電(dian)(dian)阻(zu)就是(shi)產生(sheng)了耦(ou)(ou)合(he)(he)的元件，如果(guo)在(zai)這(zhe)個(ge)電(dian)(dian)阻(zu)兩端并聯(lian)一個(ge)電(dian)(dian)容(rong)(rong)，由(you)于適(shi)當容(rong)(rong)量的電(dian)(dian)容(rong)(rong)器(qi)對交流(liu)信號(hao)較小(xiao)的阻(zu)抗,這(zhe)樣(yang)就減小(xiao)了電(dian)(dian)阻(zu)產生(sheng)的耦(ou)(ou)合(he)(he)效(xiao)應，故稱此電(dian)(dian)容(rong)(rong)為去耦(ou)(ou)電(dian)(dian)容(rong)(rong)。
2)振蕩(dang)/同(tong)步
包括RC、LC振蕩器及晶體(ti)(ti)的負(fu)載電容都(dou)屬于這一(yi)范(fan)疇。
3)時間常數(shu)
這就是常見的 R、C 串聯(lian)構成的積分電(dian)(dian)路。當輸入(ru)信號電(dian)(dian)壓加在輸入(ru)端時，電(dian)(dian)容(rong)(C)上的電(dian)(dian)壓逐漸上升(sheng)。而其充(chong)電(dian)(dian)電(dian)(dian)流則(ze)隨著電(dian)(dian)壓的上升(sheng)而減小。電(dian)(dian)流通過電(dian)(dian)阻(R)、電(dian)(dian)容(rong)(C)的特性通過下(xia)面的公式描(miao)述：
i = (V/R)e-(t/CR)
我們知(zhi)道了電容(rong)的作用以(yi)后(hou)下面(mian)來談談電容(rong)在使用中的注意事項(xiang)
A. 什(shen)么是好電容。
1.電(dian)容容量越大越好(hao)。
很多人在電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)的(de)(de)(de)(de)替換中(zhong)往(wang)往(wang)愛(ai)用(yong)大(da)容(rong)(rong)(rong)量的(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)。我們知道雖然電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)越(yue)(yue)大(da)，為IC提供(gong)的(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)補償的(de)(de)(de)(de)能(neng)(neng)力越(yue)(yue)強。且不說(shuo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)容(rong)(rong)(rong)量的(de)(de)(de)(de)增(zeng)大(da)帶來的(de)(de)(de)(de)體積變大(da)，增(zeng)加成(cheng)本的(de)(de)(de)(de)同時還(huan)影響空氣流(liu)動(dong)和散熱(re)。關鍵在于電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)上(shang)存在寄生電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)感，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)放(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)回(hui)路會在某個頻點上(shang)發生諧(xie)(xie)振(zhen)。在諧(xie)(xie)振(zhen)點，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)的(de)(de)(de)(de)阻抗(kang)小(xiao)。因此放(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)回(hui)路的(de)(de)(de)(de)阻抗(kang)最小(xiao)，補充能(neng)(neng)量的(de)(de)(de)(de)效(xiao)果也(ye)最好(hao)。但當頻率超過(guo)諧(xie)(xie)振(zhen)點時，放(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)回(hui)路的(de)(de)(de)(de)阻抗(kang)開始(shi)增(zeng)加，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)提供(gong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)能(neng)(neng)力便開始(shi)下降。電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)的(de)(de)(de)(de)容(rong)(rong)(rong)值越(yue)(yue)大(da)，諧(xie)(xie)振(zhen)頻率越(yue)(yue)低(di)，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)能(neng)(neng)有(you)效(xiao)補償電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)的(de)(de)(de)(de)頻率范圍也(ye)越(yue)(yue)小(xiao)。從保證(zheng)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)提供(gong)高頻電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)的(de)(de)(de)(de)能(neng)(neng)力的(de)(de)(de)(de)角度來說(shuo)，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)越(yue)(yue)大(da)越(yue)(yue)好(hao)的(de)(de)(de)(de)觀點是錯誤的(de)(de)(de)(de)，一(yi)般的(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路設計中(zhong)都(dou)有(you)一(yi)個參(can)考值的(de)(de)(de)(de)。
2.同(tong)樣容(rong)(rong)量的電容(rong)(rong)，并聯越多的小電容(rong)(rong)越好
耐壓值(zhi)(zhi)、耐溫值(zhi)(zhi)、容(rong)(rong)值(zhi)(zhi)、ESR(等(deng)效電阻(zu))等(deng)是(shi)(shi)電容(rong)(rong)的幾個重(zhong)要參數，對于ESR自然是(shi)(shi)越(yue)(yue)低(di)越(yue)(yue)好。ESR與電容(rong)(rong)的容(rong)(rong)量(liang)、頻率、電壓、溫度等(deng)都有關系。當(dang)電壓固定(ding)(ding)時(shi)候，容(rong)(rong)量(liang)越(yue)(yue)大，ESR越(yue)(yue)低(di)。在板卡設(she)計中(zhong)采(cai)用多個小電容(rong)(rong)并連多是(shi)(shi)出(chu)與PCB空間的限制，這樣有的人就認(ren)為，越(yue)(yue)多的并聯(lian)小電阻(zu)，ESR越(yue)(yue)低(di)，效果越(yue)(yue)好。理論上是(shi)(shi)如此，但是(shi)(shi)要考慮到(dao)電容(rong)(rong)接腳(jiao)焊點的阻(zu)抗，采(cai)用多個小電容(rong)(rong)并聯(lian)，效果并不一(yi)定(ding)(ding)突出(chu)。
3.ESR越(yue)低，效(xiao)果越(yue)好(hao)。
結(jie)合我(wo)們上面的(de)(de)(de)(de)提(ti)高的(de)(de)(de)(de)供電(dian)電(dian)路來說(shuo)，對(dui)于輸入(ru)電(dian)容(rong)來說(shuo)，輸入(ru)電(dian)容(rong)的(de)(de)(de)(de)容(rong)量要(yao)大(da)一點(dian)。相對(dui)容(rong)量的(de)(de)(de)(de)要(yao)求，對(dui)ESR的(de)(de)(de)(de)要(yao)求可以適當的(de)(de)(de)(de)降低。因(yin)(yin)為輸入(ru)電(dian)容(rong)主要(yao)是耐壓(ya)，其次是吸收(shou)MOSFET的(de)(de)(de)(de)開(kai)關脈沖。對(dui)于輸出電(dian)容(rong)來說(shuo)，耐壓(ya)的(de)(de)(de)(de)要(yao)求和(he)容(rong)量可以適當的(de)(de)(de)(de)降低一點(dian)。ESR的(de)(de)(de)(de)要(yao)求則高一點(dian)，因(yin)(yin)為這(zhe)里要(yao)保(bao)證(zheng)的(de)(de)(de)(de)是足夠的(de)(de)(de)(de)電(dian)流通過量。但這(zhe)里要(yao)注意的(de)(de)(de)(de)是ESR并不是越低越好，低ESR電(dian)容(rong)會引(yin)起(qi)開(kai)關電(dian)路振(zhen)蕩(dang)。而(er)消(xiao)振(zhen)電(dian)路復雜同(tong)時會導致(zhi)成本(ben)的(de)(de)(de)(de)增加。板卡(ka)設計中，這(zhe)里一般有(you)一個(ge)參(can)考(kao)值，此作為元件選用參(can)數，避免消(xiao)振(zhen)電(dian)路而(er)導致(zhi)成本(ben)的(de)(de)(de)(de)增加。
4.好電容代表著高品質(zhi)。
“唯電(dian)容(rong)論”曾經盛極一(yi)時，一(yi)些廠(chang)商(shang)和媒體(ti)也刻意(yi)的(de)把這(zhe)個(ge)事情做(zuo)成一(yi)個(ge)賣(mai)點(dian)。在(zai)板卡(ka)設計(ji)中，電(dian)路設計(ji)水平是(shi)關鍵(jian)。和有(you)的(de)廠(chang)商(shang)可以(yi)用(yong)(yong)(yong)兩(liang)相供電(dian)做(zuo)出比一(yi)些廠(chang)商(shang)采用(yong)(yong)(yong)四相供電(dian)更(geng)穩定(ding)的(de)產(chan)(chan)品一(yi)樣，一(yi)味的(de)采用(yong)(yong)(yong)高價電(dian)容(rong)，不一(yi)定(ding)能做(zuo)出好產(chan)(chan)品。衡量一(yi)個(ge)產(chan)(chan)品，一(yi)定(ding)要全方位多角度的(de)去考慮(lv)，切不可把電(dian)容(rong)的(de)作(zuo)用(yong)(yong)(yong)有(you)意(yi)無(wu)意(yi)的(de)夸(kua)大。
B. 電容爆漿之面面談(tan)
爆漿(jiang)的種類：
分兩類，輸入電容(rong)爆漿(jiang)和輸出電容(rong)爆漿(jiang)。
對于輸入(ru)(ru)(ru)電(dian)(dian)(dian)容(rong)(rong)來(lai)說(shuo)，就是我(wo)是說(shuo)的C1，C1對由電(dian)(dian)(dian)源接收到的電(dian)(dian)(dian)流進行過(guo)(guo)(guo)濾。輸入(ru)(ru)(ru)電(dian)(dian)(dian)容(rong)(rong)爆漿(jiang)和電(dian)(dian)(dian)源輸入(ru)(ru)(ru)電(dian)(dian)(dian)流的品質有(you)關。過(guo)(guo)(guo)多(duo)的毛刺電(dian)(dian)(dian)壓(ya)，峰值電(dian)(dian)(dian)壓(ya)過(guo)(guo)(guo)高(gao)，電(dian)(dian)(dian)流不穩(wen)定等都使電(dian)(dian)(dian)容(rong)(rong)過(guo)(guo)(guo)于充(chong)放電(dian)(dian)(dian)過(guo)(guo)(guo)于頻繁，長時間處于這類工作環境下的電(dian)(dian)(dian)容(rong)(rong)，內部溫度(du)升高(gao)很快。超(chao)過(guo)(guo)(guo)泄爆口(kou)的承受(shou)極限就會(hui)發生爆漿(jiang)。
對(dui)(dui)于(yu)輸出電(dian)容(rong)來(lai)說，就我說的(de)C2，對(dui)(dui)經電(dian)源模塊調(diao)整后的(de)電(dian)流進行濾波。此處電(dian)流經過一次過濾，比較平穩，發生(sheng)爆(bao)漿的(de)可能性相對(dui)(dui)來(lai)說小(xiao)了不少。但如果環境溫度過高，電(dian)容(rong)同樣容(rong)易(yi)發生(sheng)爆(bao)漿。爆(bao)，報(bao)也。采用(yong)垃圾東西自然要爆(bao)，報(bao)應啊(a)。欲知過去因者，見其(qi)(qi)現(xian)(xian)在果;欲知未來(lai)果者，見其(qi)(qi)現(xian)(xian)在因。
電解電容爆漿的原因：
電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)爆漿(jiang)(jiang)(jiang)的(de)(de)(de)(de)(de)(de)(de)原(yuan)因(yin)有很(hen)多，比如電(dian)(dian)(dian)(dian)(dian)流大(da)(da)于允許的(de)(de)(de)(de)(de)(de)(de)穩波電(dian)(dian)(dian)(dian)(dian)流、使(shi)用電(dian)(dian)(dian)(dian)(dian)壓超(chao)出工(gong)作電(dian)(dian)(dian)(dian)(dian)壓、逆向電(dian)(dian)(dian)(dian)(dian)壓、頻(pin)繁的(de)(de)(de)(de)(de)(de)(de)充(chong)放(fang)電(dian)(dian)(dian)(dian)(dian)等。但是(shi)(shi)(shi)(shi)(shi)最直接的(de)(de)(de)(de)(de)(de)(de)原(yuan)因(yin)就(jiu)是(shi)(shi)(shi)(shi)(shi)高(gao)(gao)溫(wen)。我們知道電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)有一個(ge)重(zhong)要的(de)(de)(de)(de)(de)(de)(de)參數(shu)就(jiu)是(shi)(shi)(shi)(shi)(shi)耐(nai)溫(wen)值(zhi)，指的(de)(de)(de)(de)(de)(de)(de)就(jiu)是(shi)(shi)(shi)(shi)(shi)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)內部電(dian)(dian)(dian)(dian)(dian)解液的(de)(de)(de)(de)(de)(de)(de)沸點(dian)。當電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)的(de)(de)(de)(de)(de)(de)(de)內部溫(wen)度(du)達(da)到(dao)(dao)電(dian)(dian)(dian)(dian)(dian)解液的(de)(de)(de)(de)(de)(de)(de)沸點(dian)時(shi)(shi)，電(dian)(dian)(dian)(dian)(dian)解液開始沸騰，電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)內部的(de)(de)(de)(de)(de)(de)(de)壓力(li)升(sheng)高(gao)(gao)，當壓力(li)超(chao)過(guo)泄(xie)爆口的(de)(de)(de)(de)(de)(de)(de)承受極限就(jiu)發生了爆漿(jiang)(jiang)(jiang)。所以說(shuo)溫(wen)度(du)是(shi)(shi)(shi)(shi)(shi)導致電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)爆漿(jiang)(jiang)(jiang)的(de)(de)(de)(de)(de)(de)(de)直接原(yuan)因(yin)。電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)設計使(shi)用壽(shou)(shou)(shou)命(ming)(ming)大(da)(da)約為(wei)2萬小時(shi)(shi)，受環(huan)(huan)境(jing)溫(wen)度(du)的(de)(de)(de)(de)(de)(de)(de)影(ying)響也很(hen)大(da)(da)。電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)的(de)(de)(de)(de)(de)(de)(de)使(shi)用壽(shou)(shou)(shou)命(ming)(ming)隨溫(wen)度(du)的(de)(de)(de)(de)(de)(de)(de)增(zeng)加(jia)而(er)減(jian)小，實驗證(zheng)明環(huan)(huan)境(jing)溫(wen)度(du)每(mei)升(sheng)高(gao)(gao)10℃，電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)的(de)(de)(de)(de)(de)(de)(de)壽(shou)(shou)(shou)命(ming)(ming)就(jiu)會減(jian)半(ban)。主要原(yuan)因(yin)就(jiu)是(shi)(shi)(shi)(shi)(shi)溫(wen)度(du)加(jia)速化(hua)學反應而(er)使(shi)介質(zhi)隨時(shi)(shi)間(jian)退化(hua)失效，這樣電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)壽(shou)(shou)(shou)命(ming)(ming)終結。為(wei)了保證(zheng)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)的(de)(de)(de)(de)(de)(de)(de)穩定性，電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)在插板前要經過(guo)長時(shi)(shi)間(jian)的(de)(de)(de)(de)(de)(de)(de)高(gao)(gao)溫(wen)環(huan)(huan)境(jing)的(de)(de)(de)(de)(de)(de)(de)測試。即使(shi)是(shi)(shi)(shi)(shi)(shi)在100℃，高(gao)(gao)品質(zhi)的(de)(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)也可以工(gong)作幾(ji)千個(ge)小時(shi)(shi)。同(tong)時(shi)(shi)，我們提到(dao)(dao)的(de)(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)的(de)(de)(de)(de)(de)(de)(de)壽(shou)(shou)(shou)命(ming)(ming)是(shi)(shi)(shi)(shi)(shi)指電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)在使(shi)用過(guo)程中(zhong)，電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)容(rong)(rong)(rong)(rong)(rong)(rong)量不(bu)會超(chao)過(guo)標(biao)準范圍變化(hua)的(de)(de)(de)(de)(de)(de)(de)10%。電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)壽(shou)(shou)(shou)命(ming)(ming)指的(de)(de)(de)(de)(de)(de)(de)是(shi)(shi)(shi)(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)(de)(de)問題，而(er)不(bu)是(shi)(shi)(shi)(shi)(shi)設計壽(shou)(shou)(shou)命(ming)(ming)到(dao)(dao)達(da)之后就(jiu)發生爆漿(jiang)(jiang)(jiang)。只是(shi)(shi)(shi)(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)(de)(de)設計的(de)(de)(de)(de)(de)(de)(de)容(rong)(rong)(rong)(rong)(rong)(rong)量標(biao)準。
所(suo)以，短時期內，正(zheng)常使用(yong)(yong)(yong)的(de)板卡電容就(jiu)發生爆(bao)漿的(de)情況，這(zhe)就(jiu)是電容品質(zhi)問題。另外，不正(zheng)常的(de)使用(yong)(yong)(yong)情況也有可(ke)能發生電容爆(bao)漿的(de)情況。比(bi)如熱(re)插拔(ba)電腦配件也會導致板卡局(ju)部電路電流、電壓(ya)的(de)劇烈變化，從而引發電容使用(yong)(yong)(yong)故障。
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