詳解電容在電源中所起到的作用
2019/7/1 12:46:11??????點擊：
作(zuo)為(wei)無(wu)源(yuan)元件之一的電容，其作(zuo)用不外(wai)乎以下幾種：
1、應(ying)用于電(dian)源電(dian)路，實現(xian)旁路、去藕(ou)、濾波(bo)和儲能方面電(dian)容的作(zuo)用，下面分類詳(xiang)述(shu)之：
1)濾波
濾波是電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)的(de)(de)作(zuo)用中(zhong)(zhong)很重要(yao)的(de)(de)一(yi)部分。幾乎(hu)所有(you)的(de)(de)電(dian)(dian)(dian)(dian)(dian)源電(dian)(dian)(dian)(dian)(dian)路中(zhong)(zhong)都會用到。從理論上(即假設電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)為純(chun)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong))說，電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)越(yue)(yue)(yue)大(da)(da)，阻(zu)抗越(yue)(yue)(yue)小(xiao)，通(tong)(tong)過的(de)(de)頻(pin)率也越(yue)(yue)(yue)高(gao)(gao)。但實際上超過1uF的(de)(de)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)大(da)(da)多為電(dian)(dian)(dian)(dian)(dian)解電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)，有(you)很大(da)(da)的(de)(de)電(dian)(dian)(dian)(dian)(dian)感成份(fen)，所以頻(pin)率高(gao)(gao)后反(fan)而阻(zu)抗會增大(da)(da)。有(you)時(shi)(shi)會看到有(you)一(yi)個(ge)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)量較大(da)(da)電(dian)(dian)(dian)(dian)(dian)解電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)并(bing)聯了一(yi)個(ge)小(xiao)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)，這時(shi)(shi)大(da)(da)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)通(tong)(tong)低(di)(di)頻(pin)，小(xiao)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)通(tong)(tong)高(gao)(gao)頻(pin)。電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)的(de)(de)作(zuo)用就是通(tong)(tong)高(gao)(gao)阻(zu)低(di)(di)，通(tong)(tong)高(gao)(gao)頻(pin)阻(zu)低(di)(di)頻(pin)。電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)越(yue)(yue)(yue)大(da)(da)低(di)(di)頻(pin)越(yue)(yue)(yue)容(rong)(rong)(rong)(rong)(rong)(rong)易通(tong)(tong)過，電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)越(yue)(yue)(yue)大(da)(da)高(gao)(gao)頻(pin)越(yue)(yue)(yue)容(rong)(rong)(rong)(rong)(rong)(rong)易通(tong)(tong)過。具體(ti)用在(zai)濾波中(zhong)(zhong),大(da)(da)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)(1000uF)濾低(di)(di)頻(pin)，小(xiao)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)(20pF)濾高(gao)(gao)頻(pin)。
曾有網(wang)友將濾波電(dian)容(rong) 比(bi)作“水塘”。由于電(dian)容(rong)的兩端電(dian)壓不會(hui)突(tu)變(bian)，由此可知，信號頻率越高則衰減(jian)越大(da)，可很形象(xiang)的說電(dian)容(rong)像個水塘，不會(hui)因幾滴水的加(jia)入(ru)或蒸發(fa)而引起(qi)水量的變(bian)化(hua)。 它把(ba)電(dian)壓的變(bian)動轉化(hua)為(wei)電(dian)流的變(bian)化(hua)，頻率越高，峰值電(dian)流就(jiu)越大(da)，從而緩沖(chong)了電(dian)壓。濾波就(jiu)是(shi)充電(dian)，放電(dian)的過程(cheng)。
2)旁路
旁路電(dian)(dian)(dian)容是(shi)為本地(di)器件提供(gong)能(neng)(neng)量的儲能(neng)(neng)器件，它能(neng)(neng)使(shi)穩壓器的輸(shu)出(chu)均勻化，降(jiang)低負(fu)載需求。就像小(xiao)型可充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)池一樣，旁路電(dian)(dian)(dian)容能(neng)(neng)夠被充(chong)電(dian)(dian)(dian)，并(bing)向器件進行(xing)放 電(dian)(dian)(dian)。為盡量減少阻抗，旁路電(dian)(dian)(dian)容要盡量靠近負(fu)載器件的供(gong)電(dian)(dian)(dian)電(dian)(dian)(dian)源管腳和(he)地(di)管腳。這能(neng)(neng)夠很好地(di)防止輸(shu)入值過大而導致的地(di)電(dian)(dian)(dian)位抬高和(he)噪聲。地(di)彈是(shi)地(di)連接處在通過大 電(dian)(dian)(dian)流(liu)毛刺時的電(dian)(dian)(dian)壓降(jiang)。
3)去藕
去(qu)(qu)藕(ou)，又稱(cheng)解(jie)藕(ou)。從(cong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)來(lai)說(shuo)(shuo)，總是(shi)(shi)(shi)可以(yi)區分(fen)為驅(qu)(qu)動(dong)的(de)(de)(de)源(yuan)和被驅(qu)(qu)動(dong)的(de)(de)(de)負載。如(ru)果負載電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)比(bi)較(jiao)大，驅(qu)(qu)動(dong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)要把電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)充電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)、放(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)，才能完成(cheng)信(xin)號(hao)(hao)的(de)(de)(de)跳(tiao)變，在上 升沿比(bi)較(jiao)陡峭的(de)(de)(de)時候(hou)，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)比(bi)較(jiao)大，這樣驅(qu)(qu)動(dong)的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)就(jiu)(jiu)(jiu)會(hui)吸收很(hen)大的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)，由(you)于電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)中的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)感(gan)，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(特別(bie)是(shi)(shi)(shi)芯片(pian)管腳上的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)感(gan)，會(hui)產生反彈(dan))，這種電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)相(xiang)對(dui) 于正(zheng)常(chang)情況來(lai)說(shuo)(shuo)實際(ji)上就(jiu)(jiu)(jiu)是(shi)(shi)(shi)一(yi)種噪聲(sheng)，會(hui)影響(xiang)前級的(de)(de)(de)正(zheng)常(chang)工作。這就(jiu)(jiu)(jiu)是(shi)(shi)(shi)耦(ou)(ou)(ou)合(he)(he)。去(qu)(qu)藕(ou)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)就(jiu)(jiu)(jiu)是(shi)(shi)(shi)起到(dao)一(yi)個(ge)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池的(de)(de)(de)作用(yong)，滿足(zu)驅(qu)(qu)動(dong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)的(de)(de)(de)變化，避免相(xiang)互間的(de)(de)(de)耦(ou)(ou)(ou)合(he)(he)干擾(rao)。將旁(pang)路(lu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)和去(qu)(qu)藕(ou)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)結合(he)(he)起來(lai)將更容(rong)(rong)(rong)易理解(jie)。旁(pang)路(lu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)實際(ji)也(ye)是(shi)(shi)(shi)去(qu)(qu)藕(ou)合(he)(he)的(de)(de)(de)，只是(shi)(shi)(shi)旁(pang)路(lu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)一(yi)般是(shi)(shi)(shi)指高頻旁(pang)路(lu)，也(ye)就(jiu)(jiu)(jiu)是(shi)(shi)(shi)給高頻的(de)(de)(de)開(kai)關噪聲(sheng)提高一(yi)條低阻(zu)抗泄防 途徑(jing)。高頻旁(pang)路(lu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)一(yi)般比(bi)較(jiao)小(xiao)，根據諧(xie)振頻率一(yi)般是(shi)(shi)(shi)0.1u，0.01u等，而去(qu)(qu)耦(ou)(ou)(ou)合(he)(he)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)一(yi)般比(bi)較(jiao)大，是(shi)(shi)(shi)10uF或者(zhe)更大，依(yi)據電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)中分(fen)布(bu)參數(shu)，以(yi)及驅(qu)(qu)動(dong) 電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)的(de)(de)(de)變化大小(xiao)來(lai)確(que)定。旁(pang)路(lu)是(shi)(shi)(shi)把輸(shu)入信(xin)號(hao)(hao)中的(de)(de)(de)干擾(rao)作為濾(lv)(lv)除對(dui)象，而去(qu)(qu)耦(ou)(ou)(ou)是(shi)(shi)(shi)把輸(shu)出信(xin)號(hao)(hao)的(de)(de)(de)干擾(rao)作為濾(lv)(lv)除對(dui)象，防止干擾(rao)信(xin)號(hao)(hao)返回(hui)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)。這應該(gai)是(shi)(shi)(shi)他(ta)們的(de)(de)(de)本(ben)質區別(bie)。
4)儲能(neng)
儲能(neng)型(xing)電(dian)(dian)(dian)容器(qi)(qi)通(tong)(tong)過(guo)(guo)整流器(qi)(qi)收集電(dian)(dian)(dian)荷，并(bing)將存儲的(de)能(neng)量通(tong)(tong)過(guo)(guo)變換(huan)器(qi)(qi)引線傳送(song)至(zhi)電(dian)(dian)(dian)源的(de)輸出端。電(dian)(dian)(dian)壓額定值為40～450VDC、電(dian)(dian)(dian)容值在220～150 000uF之間的(de)鋁電(dian)(dian)(dian)解電(dian)(dian)(dian)容器(qi)(qi)(如(ru)EPCOS公司的(de) B43504或B43505)是較為常(chang)(chang)用(yong)的(de)。根據不同的(de)電(dian)(dian)(dian)源要求，器(qi)(qi)件有(you)時會采用(yong)串聯(lian)、并(bing)聯(lian)或其(qi)組合的(de)形(xing)式， 對于功率級超過(guo)(guo)10KW的(de)電(dian)(dian)(dian)源，通(tong)(tong)常(chang)(chang)采用(yong)體(ti)積較大的(de)罐形(xing)螺(luo)旋端子電(dian)(dian)(dian)容器(qi)(qi)。
2、應用(yong)于信號電(dian)路，主要(yao)完成(cheng)耦合、振蕩(dang)/同步及時間常數的作用(yong)：
1)耦(ou)合
舉個例子來(lai)講，晶體管放大器發射極(ji)有一個自(zi)給(gei)偏壓電阻(zu)，它同(tong)時又使信號產(chan)生壓降反饋到輸入(ru)端(duan)(duan)形成(cheng)了(le)輸入(ru)輸出信號耦合(he)，這個電阻(zu)就(jiu)是(shi)產(chan)生了(le)耦合(he)的(de)元(yuan)件，如(ru)果在這個電阻(zu)兩(liang)端(duan)(duan)并聯一個電容，由(you)于適當容量的(de)電容器對交流(liu)信號較小(xiao)的(de)阻(zu)抗,這樣就(jiu)減小(xiao)了(le)電阻(zu)產(chan)生的(de)耦合(he)效應，故稱此電容為去耦電容。
2)振蕩/同(tong)步
包括RC、LC振蕩器(qi)及晶體(ti)的負載電容(rong)都屬于(yu)這一范疇。
3)時(shi)間常(chang)數(shu)
這(zhe)就是常見的(de)(de)(de) R、C 串聯構(gou)成的(de)(de)(de)積分電(dian)路。當(dang)輸(shu)入信(xin)號電(dian)壓加在輸(shu)入端(duan)時，電(dian)容(rong)(C)上的(de)(de)(de)電(dian)壓逐(zhu)漸(jian)上升。而其(qi)充電(dian)電(dian)流(liu)則(ze)隨著電(dian)壓的(de)(de)(de)上升而減(jian)小。電(dian)流(liu)通(tong)過(guo)電(dian)阻(zu)(R)、電(dian)容(rong)(C)的(de)(de)(de)特性通(tong)過(guo)下面的(de)(de)(de)公式描(miao)述：
i = (V/R)e-(t/CR)
我們知道(dao)了電容(rong)的(de)作用以后下面(mian)來談談電容(rong)在(zai)使用中(zhong)的(de)注(zhu)意事項
A. 什么(me)是好電容。
1.電容容量(liang)越(yue)大越(yue)好。
很多(duo)人(ren)在(zai)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)的(de)替換中(zhong)(zhong)往(wang)(wang)往(wang)(wang)愛用大容(rong)(rong)(rong)(rong)量的(de)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)。我們(men)知道雖(sui)然(ran)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)越(yue)(yue)大，為(wei)IC提(ti)供的(de)電(dian)(dian)(dian)(dian)(dian)流(liu)補(bu)(bu)償的(de)能(neng)力(li)越(yue)(yue)強(qiang)。且不說電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)容(rong)(rong)(rong)(rong)量的(de)增大帶來的(de)體積變(bian)大，增加成本的(de)同時還(huan)影(ying)響空氣流(liu)動和散(san)熱。關鍵在(zai)于電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)上存在(zai)寄生電(dian)(dian)(dian)(dian)(dian)感，電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)放(fang)電(dian)(dian)(dian)(dian)(dian)回(hui)(hui)路(lu)會(hui)在(zai)某個(ge)頻(pin)(pin)(pin)點(dian)上發生諧(xie)振(zhen)。在(zai)諧(xie)振(zhen)點(dian)，電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)的(de)阻(zu)抗(kang)小(xiao)。因此(ci)放(fang)電(dian)(dian)(dian)(dian)(dian)回(hui)(hui)路(lu)的(de)阻(zu)抗(kang)最(zui)小(xiao)，補(bu)(bu)充(chong)能(neng)量的(de)效果也最(zui)好。但當(dang)頻(pin)(pin)(pin)率(lv)超過諧(xie)振(zhen)點(dian)時，放(fang)電(dian)(dian)(dian)(dian)(dian)回(hui)(hui)路(lu)的(de)阻(zu)抗(kang)開始增加，電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)提(ti)供電(dian)(dian)(dian)(dian)(dian)流(liu)能(neng)力(li)便開始下(xia)降。電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)的(de)容(rong)(rong)(rong)(rong)值(zhi)越(yue)(yue)大，諧(xie)振(zhen)頻(pin)(pin)(pin)率(lv)越(yue)(yue)低，電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)能(neng)有(you)效補(bu)(bu)償電(dian)(dian)(dian)(dian)(dian)流(liu)的(de)頻(pin)(pin)(pin)率(lv)范(fan)圍也越(yue)(yue)小(xiao)。從保證電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)提(ti)供高頻(pin)(pin)(pin)電(dian)(dian)(dian)(dian)(dian)流(liu)的(de)能(neng)力(li)的(de)角度來說，電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)越(yue)(yue)大越(yue)(yue)好的(de)觀點(dian)是錯(cuo)誤的(de)，一般的(de)電(dian)(dian)(dian)(dian)(dian)路(lu)設計中(zhong)(zhong)都有(you)一個(ge)參考值(zhi)的(de)。
2.同樣容量的電(dian)容，并聯越(yue)(yue)多的小電(dian)容越(yue)(yue)好
耐壓(ya)值(zhi)、耐溫值(zhi)、容(rong)值(zhi)、ESR(等(deng)效(xiao)電(dian)阻(zu))等(deng)是電(dian)容(rong)的幾個重要參數，對(dui)于ESR自然(ran)是越(yue)低(di)越(yue)好。ESR與電(dian)容(rong)的容(rong)量(liang)、頻率(lv)、電(dian)壓(ya)、溫度等(deng)都(dou)有關(guan)系。當電(dian)壓(ya)固(gu)定時(shi)候(hou)，容(rong)量(liang)越(yue)大，ESR越(yue)低(di)。在板(ban)卡設(she)計中(zhong)采用多個小電(dian)容(rong)并(bing)連(lian)多是出與PCB空間(jian)的限制，這樣(yang)有的人就認為，越(yue)多的并(bing)聯小電(dian)阻(zu)，ESR越(yue)低(di)，效(xiao)果越(yue)好。理論上是如此，但是要考慮(lv)到電(dian)容(rong)接腳焊點的阻(zu)抗，采用多個小電(dian)容(rong)并(bing)聯，效(xiao)果并(bing)不一(yi)定突出。
3.ESR越低，效果越好。
結(jie)合(he)我(wo)們上面的(de)(de)(de)提(ti)高的(de)(de)(de)供(gong)電(dian)電(dian)路(lu)來(lai)說(shuo)，對于輸入電(dian)容(rong)來(lai)說(shuo)，輸入電(dian)容(rong)的(de)(de)(de)容(rong)量要(yao)(yao)大一點。相對容(rong)量的(de)(de)(de)要(yao)(yao)求(qiu)(qiu)，對ESR的(de)(de)(de)要(yao)(yao)求(qiu)(qiu)可(ke)以(yi)適當的(de)(de)(de)降低(di)。因為(wei)(wei)輸入電(dian)容(rong)主(zhu)要(yao)(yao)是耐壓，其(qi)次是吸收MOSFET的(de)(de)(de)開關脈沖(chong)。對于輸出電(dian)容(rong)來(lai)說(shuo)，耐壓的(de)(de)(de)要(yao)(yao)求(qiu)(qiu)和容(rong)量可(ke)以(yi)適當的(de)(de)(de)降低(di)一點。ESR的(de)(de)(de)要(yao)(yao)求(qiu)(qiu)則高一點，因為(wei)(wei)這(zhe)里要(yao)(yao)保(bao)證的(de)(de)(de)是足夠的(de)(de)(de)電(dian)流通過量。但這(zhe)里要(yao)(yao)注意的(de)(de)(de)是ESR并不(bu)是越(yue)低(di)越(yue)好，低(di)ESR電(dian)容(rong)會引起開關電(dian)路(lu)振蕩。而(er)消振電(dian)路(lu)復(fu)雜同時會導致成本的(de)(de)(de)增(zeng)加(jia)。板(ban)卡設計中(zhong)，這(zhe)里一般有一個參考(kao)值(zhi)，此(ci)作(zuo)為(wei)(wei)元(yuan)件(jian)選用參數，避免消振電(dian)路(lu)而(er)導致成本的(de)(de)(de)增(zeng)加(jia)。
4.好電容代表(biao)著高品質。
“唯電(dian)(dian)容(rong)(rong)論”曾經盛極一(yi)(yi)時(shi)，一(yi)(yi)些廠商(shang)(shang)和(he)媒(mei)體也刻意(yi)(yi)的(de)(de)把(ba)這(zhe)個事(shi)情做(zuo)成一(yi)(yi)個賣點(dian)。在(zai)板卡設計中，電(dian)(dian)路設計水平是關(guan)鍵。和(he)有(you)的(de)(de)廠商(shang)(shang)可以用(yong)兩相供電(dian)(dian)做(zuo)出比一(yi)(yi)些廠商(shang)(shang)采用(yong)四相供電(dian)(dian)更(geng)穩定的(de)(de)產品一(yi)(yi)樣，一(yi)(yi)味的(de)(de)采用(yong)高價電(dian)(dian)容(rong)(rong)，不一(yi)(yi)定能做(zuo)出好產品。衡量(liang)一(yi)(yi)個產品，一(yi)(yi)定要全方位多角度(du)的(de)(de)去(qu)考慮，切(qie)不可把(ba)電(dian)(dian)容(rong)(rong)的(de)(de)作用(yong)有(you)意(yi)(yi)無意(yi)(yi)的(de)(de)夸大。
B. 電容爆漿之(zhi)面(mian)面(mian)談
爆漿的種類：
分兩類，輸入電容(rong)爆漿和輸出電容(rong)爆漿。
對(dui)于輸入電(dian)容(rong)來說(shuo)，就(jiu)是我是說(shuo)的(de)C1，C1對(dui)由電(dian)源接收到的(de)電(dian)流進行過(guo)濾。輸入電(dian)容(rong)爆漿和(he)電(dian)源輸入電(dian)流的(de)品質有關。過(guo)多的(de)毛刺(ci)電(dian)壓，峰(feng)值(zhi)電(dian)壓過(guo)高(gao)，電(dian)流不穩(wen)定等都使(shi)電(dian)容(rong)過(guo)于充(chong)放電(dian)過(guo)于頻繁(fan)，長時(shi)間(jian)處于這類工作環境下的(de)電(dian)容(rong)，內部(bu)溫(wen)度升高(gao)很快。超過(guo)泄爆口的(de)承(cheng)受極(ji)限就(jiu)會發生爆漿。
對于(yu)輸出電容來(lai)說，就我說的C2，對經電源模塊調整后的電流進行濾波。此處電流經過一次過濾，比較平穩，發生(sheng)爆(bao)漿的可能性(xing)相對來(lai)說小(xiao)了(le)不少。但如果(guo)環境溫度過高，電容同樣容易(yi)發生(sheng)爆(bao)漿。爆(bao)，報也。采用垃圾東(dong)西自然要(yao)爆(bao)，報應啊。欲知(zhi)過去因(yin)者，見(jian)其(qi)現在(zai)果(guo);欲知(zhi)未來(lai)果(guo)者，見(jian)其(qi)現在(zai)因(yin)。
電解(jie)電容爆漿(jiang)的原因：
電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)爆(bao)漿(jiang)的(de)(de)(de)(de)原因(yin)(yin)有(you)很多，比如(ru)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流大(da)于允許的(de)(de)(de)(de)穩(wen)波電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流、使(shi)(shi)用電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓超(chao)出工(gong)作(zuo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓、逆向電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓、頻繁的(de)(de)(de)(de)充放電(dian)(dian)(dian)(dian)(dian)(dian)(dian)等。但是(shi)(shi)(shi)(shi)(shi)最(zui)直(zhi)接的(de)(de)(de)(de)原因(yin)(yin)就(jiu)(jiu)是(shi)(shi)(shi)(shi)(shi)高(gao)溫(wen)。我們知道電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)有(you)一個重要(yao)的(de)(de)(de)(de)參(can)數就(jiu)(jiu)是(shi)(shi)(shi)(shi)(shi)耐溫(wen)值，指的(de)(de)(de)(de)就(jiu)(jiu)是(shi)(shi)(shi)(shi)(shi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)內部(bu)(bu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)解液(ye)的(de)(de)(de)(de)沸(fei)(fei)點(dian)。當(dang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)的(de)(de)(de)(de)內部(bu)(bu)溫(wen)度(du)(du)(du)達(da)到電(dian)(dian)(dian)(dian)(dian)(dian)(dian)解液(ye)的(de)(de)(de)(de)沸(fei)(fei)點(dian)時，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)解液(ye)開始沸(fei)(fei)騰，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)內部(bu)(bu)的(de)(de)(de)(de)壓力(li)升(sheng)高(gao)，當(dang)壓力(li)超(chao)過泄爆(bao)口的(de)(de)(de)(de)承受極限就(jiu)(jiu)發(fa)生(sheng)了(le)爆(bao)漿(jiang)。所以說溫(wen)度(du)(du)(du)是(shi)(shi)(shi)(shi)(shi)導致電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)爆(bao)漿(jiang)的(de)(de)(de)(de)直(zhi)接原因(yin)(yin)。電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)設計使(shi)(shi)用壽(shou)命(ming)(ming)(ming)大(da)約(yue)為(wei)2萬小時，受環(huan)境溫(wen)度(du)(du)(du)的(de)(de)(de)(de)影響也很大(da)。電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)的(de)(de)(de)(de)使(shi)(shi)用壽(shou)命(ming)(ming)(ming)隨溫(wen)度(du)(du)(du)的(de)(de)(de)(de)增加而減(jian)小，實(shi)驗證(zheng)明環(huan)境溫(wen)度(du)(du)(du)每升(sheng)高(gao)10℃，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)的(de)(de)(de)(de)壽(shou)命(ming)(ming)(ming)就(jiu)(jiu)會減(jian)半。主要(yao)原因(yin)(yin)就(jiu)(jiu)是(shi)(shi)(shi)(shi)(shi)溫(wen)度(du)(du)(du)加速化(hua)學反應而使(shi)(shi)介質隨時間退化(hua)失效(xiao)，這樣電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)壽(shou)命(ming)(ming)(ming)終結。為(wei)了(le)保證(zheng)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)的(de)(de)(de)(de)穩(wen)定性，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)在(zai)插板前要(yao)經過長(chang)時間的(de)(de)(de)(de)高(gao)溫(wen)環(huan)境的(de)(de)(de)(de)測試。即使(shi)(shi)是(shi)(shi)(shi)(shi)(shi)在(zai)100℃，高(gao)品質的(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)也可以工(gong)作(zuo)幾千(qian)個小時。同(tong)時，我們提到的(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)的(de)(de)(de)(de)壽(shou)命(ming)(ming)(ming)是(shi)(shi)(shi)(shi)(shi)指電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)在(zai)使(shi)(shi)用過程中，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)容(rong)(rong)(rong)(rong)(rong)(rong)量不會超(chao)過標準范(fan)圍變化(hua)的(de)(de)(de)(de)10%。電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)壽(shou)命(ming)(ming)(ming)指的(de)(de)(de)(de)是(shi)(shi)(shi)(shi)(shi)電(dian)(dian)(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)問題，而不是(shi)(shi)(shi)(shi)(shi)設計壽(shou)命(ming)(ming)(ming)到達(da)之后就(jiu)(jiu)發(fa)生(sheng)爆(bao)漿(jiang)。只(zhi)是(shi)(shi)(shi)(shi)(shi)無法保證(zheng)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)的(de)(de)(de)(de)設計的(de)(de)(de)(de)容(rong)(rong)(rong)(rong)(rong)(rong)量標準。
所以，短時期內，正(zheng)常(chang)使(shi)用(yong)的板卡電(dian)容(rong)(rong)就發生爆(bao)漿的情況，這就是電(dian)容(rong)(rong)品質(zhi)問題。另(ling)外(wai)，不正(zheng)常(chang)的使(shi)用(yong)情況也有可能發生電(dian)容(rong)(rong)爆(bao)漿的情況。比如熱插拔電(dian)腦配件也會導致板卡局部電(dian)路電(dian)流、電(dian)壓(ya)的劇(ju)烈變化，從而(er)引發電(dian)容(rong)(rong)使(shi)用(yong)故障。
1、應(ying)用于電(dian)源電(dian)路，實現(xian)旁路、去藕(ou)、濾波(bo)和儲能方面電(dian)容的作(zuo)用，下面分類詳(xiang)述(shu)之：
1)濾波
濾波是電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)的(de)(de)作(zuo)用中(zhong)(zhong)很重要(yao)的(de)(de)一(yi)部分。幾乎(hu)所有(you)的(de)(de)電(dian)(dian)(dian)(dian)(dian)源電(dian)(dian)(dian)(dian)(dian)路中(zhong)(zhong)都會用到。從理論上(即假設電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)為純(chun)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong))說，電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)越(yue)(yue)(yue)大(da)(da)，阻(zu)抗越(yue)(yue)(yue)小(xiao)，通(tong)(tong)過的(de)(de)頻(pin)率也越(yue)(yue)(yue)高(gao)(gao)。但實際上超過1uF的(de)(de)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)大(da)(da)多為電(dian)(dian)(dian)(dian)(dian)解電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)，有(you)很大(da)(da)的(de)(de)電(dian)(dian)(dian)(dian)(dian)感成份(fen)，所以頻(pin)率高(gao)(gao)后反(fan)而阻(zu)抗會增大(da)(da)。有(you)時(shi)(shi)會看到有(you)一(yi)個(ge)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)量較大(da)(da)電(dian)(dian)(dian)(dian)(dian)解電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)并(bing)聯了一(yi)個(ge)小(xiao)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)，這時(shi)(shi)大(da)(da)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)通(tong)(tong)低(di)(di)頻(pin)，小(xiao)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)通(tong)(tong)高(gao)(gao)頻(pin)。電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)的(de)(de)作(zuo)用就是通(tong)(tong)高(gao)(gao)阻(zu)低(di)(di)，通(tong)(tong)高(gao)(gao)頻(pin)阻(zu)低(di)(di)頻(pin)。電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)越(yue)(yue)(yue)大(da)(da)低(di)(di)頻(pin)越(yue)(yue)(yue)容(rong)(rong)(rong)(rong)(rong)(rong)易通(tong)(tong)過，電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)越(yue)(yue)(yue)大(da)(da)高(gao)(gao)頻(pin)越(yue)(yue)(yue)容(rong)(rong)(rong)(rong)(rong)(rong)易通(tong)(tong)過。具體(ti)用在(zai)濾波中(zhong)(zhong),大(da)(da)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)(1000uF)濾低(di)(di)頻(pin)，小(xiao)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)(20pF)濾高(gao)(gao)頻(pin)。
曾有網(wang)友將濾波電(dian)容(rong) 比(bi)作“水塘”。由于電(dian)容(rong)的兩端電(dian)壓不會(hui)突(tu)變(bian)，由此可知，信號頻率越高則衰減(jian)越大(da)，可很形象(xiang)的說電(dian)容(rong)像個水塘，不會(hui)因幾滴水的加(jia)入(ru)或蒸發(fa)而引起(qi)水量的變(bian)化(hua)。 它把(ba)電(dian)壓的變(bian)動轉化(hua)為(wei)電(dian)流的變(bian)化(hua)，頻率越高，峰值電(dian)流就(jiu)越大(da)，從而緩沖(chong)了電(dian)壓。濾波就(jiu)是(shi)充電(dian)，放電(dian)的過程(cheng)。
2)旁路
旁路電(dian)(dian)(dian)容是(shi)為本地(di)器件提供(gong)能(neng)(neng)量的儲能(neng)(neng)器件，它能(neng)(neng)使(shi)穩壓器的輸(shu)出(chu)均勻化，降(jiang)低負(fu)載需求。就像小(xiao)型可充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)池一樣，旁路電(dian)(dian)(dian)容能(neng)(neng)夠被充(chong)電(dian)(dian)(dian)，并(bing)向器件進行(xing)放 電(dian)(dian)(dian)。為盡量減少阻抗，旁路電(dian)(dian)(dian)容要盡量靠近負(fu)載器件的供(gong)電(dian)(dian)(dian)電(dian)(dian)(dian)源管腳和(he)地(di)管腳。這能(neng)(neng)夠很好地(di)防止輸(shu)入值過大而導致的地(di)電(dian)(dian)(dian)位抬高和(he)噪聲。地(di)彈是(shi)地(di)連接處在通過大 電(dian)(dian)(dian)流(liu)毛刺時的電(dian)(dian)(dian)壓降(jiang)。
3)去藕
去(qu)(qu)藕(ou)，又稱(cheng)解(jie)藕(ou)。從(cong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)來(lai)說(shuo)(shuo)，總是(shi)(shi)(shi)可以(yi)區分(fen)為驅(qu)(qu)動(dong)的(de)(de)(de)源(yuan)和被驅(qu)(qu)動(dong)的(de)(de)(de)負載。如(ru)果負載電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)比(bi)較(jiao)大，驅(qu)(qu)動(dong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)要把電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)充電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)、放(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)，才能完成(cheng)信(xin)號(hao)(hao)的(de)(de)(de)跳(tiao)變，在上 升沿比(bi)較(jiao)陡峭的(de)(de)(de)時候(hou)，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)比(bi)較(jiao)大，這樣驅(qu)(qu)動(dong)的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)就(jiu)(jiu)(jiu)會(hui)吸收很(hen)大的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)，由(you)于電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)中的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)感(gan)，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(特別(bie)是(shi)(shi)(shi)芯片(pian)管腳上的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)感(gan)，會(hui)產生反彈(dan))，這種電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)相(xiang)對(dui) 于正(zheng)常(chang)情況來(lai)說(shuo)(shuo)實際(ji)上就(jiu)(jiu)(jiu)是(shi)(shi)(shi)一(yi)種噪聲(sheng)，會(hui)影響(xiang)前級的(de)(de)(de)正(zheng)常(chang)工作。這就(jiu)(jiu)(jiu)是(shi)(shi)(shi)耦(ou)(ou)(ou)合(he)(he)。去(qu)(qu)藕(ou)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)就(jiu)(jiu)(jiu)是(shi)(shi)(shi)起到(dao)一(yi)個(ge)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池的(de)(de)(de)作用(yong)，滿足(zu)驅(qu)(qu)動(dong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)的(de)(de)(de)變化，避免相(xiang)互間的(de)(de)(de)耦(ou)(ou)(ou)合(he)(he)干擾(rao)。將旁(pang)路(lu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)和去(qu)(qu)藕(ou)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)結合(he)(he)起來(lai)將更容(rong)(rong)(rong)易理解(jie)。旁(pang)路(lu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)實際(ji)也(ye)是(shi)(shi)(shi)去(qu)(qu)藕(ou)合(he)(he)的(de)(de)(de)，只是(shi)(shi)(shi)旁(pang)路(lu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)一(yi)般是(shi)(shi)(shi)指高頻旁(pang)路(lu)，也(ye)就(jiu)(jiu)(jiu)是(shi)(shi)(shi)給高頻的(de)(de)(de)開(kai)關噪聲(sheng)提高一(yi)條低阻(zu)抗泄防 途徑(jing)。高頻旁(pang)路(lu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)一(yi)般比(bi)較(jiao)小(xiao)，根據諧(xie)振頻率一(yi)般是(shi)(shi)(shi)0.1u，0.01u等，而去(qu)(qu)耦(ou)(ou)(ou)合(he)(he)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)一(yi)般比(bi)較(jiao)大，是(shi)(shi)(shi)10uF或者(zhe)更大，依(yi)據電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)中分(fen)布(bu)參數(shu)，以(yi)及驅(qu)(qu)動(dong) 電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)的(de)(de)(de)變化大小(xiao)來(lai)確(que)定。旁(pang)路(lu)是(shi)(shi)(shi)把輸(shu)入信(xin)號(hao)(hao)中的(de)(de)(de)干擾(rao)作為濾(lv)(lv)除對(dui)象，而去(qu)(qu)耦(ou)(ou)(ou)是(shi)(shi)(shi)把輸(shu)出信(xin)號(hao)(hao)的(de)(de)(de)干擾(rao)作為濾(lv)(lv)除對(dui)象，防止干擾(rao)信(xin)號(hao)(hao)返回(hui)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)。這應該(gai)是(shi)(shi)(shi)他(ta)們的(de)(de)(de)本(ben)質區別(bie)。
4)儲能(neng)
儲能(neng)型(xing)電(dian)(dian)(dian)容器(qi)(qi)通(tong)(tong)過(guo)(guo)整流器(qi)(qi)收集電(dian)(dian)(dian)荷，并(bing)將存儲的(de)能(neng)量通(tong)(tong)過(guo)(guo)變換(huan)器(qi)(qi)引線傳送(song)至(zhi)電(dian)(dian)(dian)源的(de)輸出端。電(dian)(dian)(dian)壓額定值為40～450VDC、電(dian)(dian)(dian)容值在220～150 000uF之間的(de)鋁電(dian)(dian)(dian)解電(dian)(dian)(dian)容器(qi)(qi)(如(ru)EPCOS公司的(de) B43504或B43505)是較為常(chang)(chang)用(yong)的(de)。根據不同的(de)電(dian)(dian)(dian)源要求，器(qi)(qi)件有(you)時會采用(yong)串聯(lian)、并(bing)聯(lian)或其(qi)組合的(de)形(xing)式， 對于功率級超過(guo)(guo)10KW的(de)電(dian)(dian)(dian)源，通(tong)(tong)常(chang)(chang)采用(yong)體(ti)積較大的(de)罐形(xing)螺(luo)旋端子電(dian)(dian)(dian)容器(qi)(qi)。
2、應用(yong)于信號電(dian)路，主要(yao)完成(cheng)耦合、振蕩(dang)/同步及時間常數的作用(yong)：
1)耦(ou)合
舉個例子來(lai)講，晶體管放大器發射極(ji)有一個自(zi)給(gei)偏壓電阻(zu)，它同(tong)時又使信號產(chan)生壓降反饋到輸入(ru)端(duan)(duan)形成(cheng)了(le)輸入(ru)輸出信號耦合(he)，這個電阻(zu)就(jiu)是(shi)產(chan)生了(le)耦合(he)的(de)元(yuan)件，如(ru)果在這個電阻(zu)兩(liang)端(duan)(duan)并聯一個電容，由(you)于適當容量的(de)電容器對交流(liu)信號較小(xiao)的(de)阻(zu)抗,這樣就(jiu)減小(xiao)了(le)電阻(zu)產(chan)生的(de)耦合(he)效應，故稱此電容為去耦電容。
2)振蕩/同(tong)步
包括RC、LC振蕩器(qi)及晶體(ti)的負載電容(rong)都屬于(yu)這一范疇。
3)時(shi)間常(chang)數(shu)
這(zhe)就是常見的(de)(de)(de) R、C 串聯構(gou)成的(de)(de)(de)積分電(dian)路。當(dang)輸(shu)入信(xin)號電(dian)壓加在輸(shu)入端(duan)時，電(dian)容(rong)(C)上的(de)(de)(de)電(dian)壓逐(zhu)漸(jian)上升。而其(qi)充電(dian)電(dian)流(liu)則(ze)隨著電(dian)壓的(de)(de)(de)上升而減(jian)小。電(dian)流(liu)通(tong)過(guo)電(dian)阻(zu)(R)、電(dian)容(rong)(C)的(de)(de)(de)特性通(tong)過(guo)下面的(de)(de)(de)公式描(miao)述：
i = (V/R)e-(t/CR)
我們知道(dao)了電容(rong)的(de)作用以后下面(mian)來談談電容(rong)在(zai)使用中(zhong)的(de)注(zhu)意事項
A. 什么(me)是好電容。
1.電容容量(liang)越(yue)大越(yue)好。
很多(duo)人(ren)在(zai)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)的(de)替換中(zhong)(zhong)往(wang)(wang)往(wang)(wang)愛用大容(rong)(rong)(rong)(rong)量的(de)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)。我們(men)知道雖(sui)然(ran)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)越(yue)(yue)大，為(wei)IC提(ti)供的(de)電(dian)(dian)(dian)(dian)(dian)流(liu)補(bu)(bu)償的(de)能(neng)力(li)越(yue)(yue)強(qiang)。且不說電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)容(rong)(rong)(rong)(rong)量的(de)增大帶來的(de)體積變(bian)大，增加成本的(de)同時還(huan)影(ying)響空氣流(liu)動和散(san)熱。關鍵在(zai)于電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)上存在(zai)寄生電(dian)(dian)(dian)(dian)(dian)感，電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)放(fang)電(dian)(dian)(dian)(dian)(dian)回(hui)(hui)路(lu)會(hui)在(zai)某個(ge)頻(pin)(pin)(pin)點(dian)上發生諧(xie)振(zhen)。在(zai)諧(xie)振(zhen)點(dian)，電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)的(de)阻(zu)抗(kang)小(xiao)。因此(ci)放(fang)電(dian)(dian)(dian)(dian)(dian)回(hui)(hui)路(lu)的(de)阻(zu)抗(kang)最(zui)小(xiao)，補(bu)(bu)充(chong)能(neng)量的(de)效果也最(zui)好。但當(dang)頻(pin)(pin)(pin)率(lv)超過諧(xie)振(zhen)點(dian)時，放(fang)電(dian)(dian)(dian)(dian)(dian)回(hui)(hui)路(lu)的(de)阻(zu)抗(kang)開始增加，電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)提(ti)供電(dian)(dian)(dian)(dian)(dian)流(liu)能(neng)力(li)便開始下(xia)降。電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)的(de)容(rong)(rong)(rong)(rong)值(zhi)越(yue)(yue)大，諧(xie)振(zhen)頻(pin)(pin)(pin)率(lv)越(yue)(yue)低，電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)能(neng)有(you)效補(bu)(bu)償電(dian)(dian)(dian)(dian)(dian)流(liu)的(de)頻(pin)(pin)(pin)率(lv)范(fan)圍也越(yue)(yue)小(xiao)。從保證電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)提(ti)供高頻(pin)(pin)(pin)電(dian)(dian)(dian)(dian)(dian)流(liu)的(de)能(neng)力(li)的(de)角度來說，電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)越(yue)(yue)大越(yue)(yue)好的(de)觀點(dian)是錯(cuo)誤的(de)，一般的(de)電(dian)(dian)(dian)(dian)(dian)路(lu)設計中(zhong)(zhong)都有(you)一個(ge)參考值(zhi)的(de)。
2.同樣容量的電(dian)容，并聯越(yue)(yue)多的小電(dian)容越(yue)(yue)好
耐壓(ya)值(zhi)、耐溫值(zhi)、容(rong)值(zhi)、ESR(等(deng)效(xiao)電(dian)阻(zu))等(deng)是電(dian)容(rong)的幾個重要參數，對(dui)于ESR自然(ran)是越(yue)低(di)越(yue)好。ESR與電(dian)容(rong)的容(rong)量(liang)、頻率(lv)、電(dian)壓(ya)、溫度等(deng)都(dou)有關(guan)系。當電(dian)壓(ya)固(gu)定時(shi)候(hou)，容(rong)量(liang)越(yue)大，ESR越(yue)低(di)。在板(ban)卡設(she)計中(zhong)采用多個小電(dian)容(rong)并(bing)連(lian)多是出與PCB空間(jian)的限制，這樣(yang)有的人就認為，越(yue)多的并(bing)聯小電(dian)阻(zu)，ESR越(yue)低(di)，效(xiao)果越(yue)好。理論上是如此，但是要考慮(lv)到電(dian)容(rong)接腳焊點的阻(zu)抗，采用多個小電(dian)容(rong)并(bing)聯，效(xiao)果并(bing)不一(yi)定突出。
3.ESR越低，效果越好。
結(jie)合(he)我(wo)們上面的(de)(de)(de)提(ti)高的(de)(de)(de)供(gong)電(dian)電(dian)路(lu)來(lai)說(shuo)，對于輸入電(dian)容(rong)來(lai)說(shuo)，輸入電(dian)容(rong)的(de)(de)(de)容(rong)量要(yao)(yao)大一點。相對容(rong)量的(de)(de)(de)要(yao)(yao)求(qiu)(qiu)，對ESR的(de)(de)(de)要(yao)(yao)求(qiu)(qiu)可(ke)以(yi)適當的(de)(de)(de)降低(di)。因為(wei)(wei)輸入電(dian)容(rong)主(zhu)要(yao)(yao)是耐壓，其(qi)次是吸收MOSFET的(de)(de)(de)開關脈沖(chong)。對于輸出電(dian)容(rong)來(lai)說(shuo)，耐壓的(de)(de)(de)要(yao)(yao)求(qiu)(qiu)和容(rong)量可(ke)以(yi)適當的(de)(de)(de)降低(di)一點。ESR的(de)(de)(de)要(yao)(yao)求(qiu)(qiu)則高一點，因為(wei)(wei)這(zhe)里要(yao)(yao)保(bao)證的(de)(de)(de)是足夠的(de)(de)(de)電(dian)流通過量。但這(zhe)里要(yao)(yao)注意的(de)(de)(de)是ESR并不(bu)是越(yue)低(di)越(yue)好，低(di)ESR電(dian)容(rong)會引起開關電(dian)路(lu)振蕩。而(er)消振電(dian)路(lu)復(fu)雜同時會導致成本的(de)(de)(de)增(zeng)加(jia)。板(ban)卡設計中(zhong)，這(zhe)里一般有一個參考(kao)值(zhi)，此(ci)作(zuo)為(wei)(wei)元(yuan)件(jian)選用參數，避免消振電(dian)路(lu)而(er)導致成本的(de)(de)(de)增(zeng)加(jia)。
4.好電容代表(biao)著高品質。
“唯電(dian)(dian)容(rong)(rong)論”曾經盛極一(yi)(yi)時(shi)，一(yi)(yi)些廠商(shang)(shang)和(he)媒(mei)體也刻意(yi)(yi)的(de)(de)把(ba)這(zhe)個事(shi)情做(zuo)成一(yi)(yi)個賣點(dian)。在(zai)板卡設計中，電(dian)(dian)路設計水平是關(guan)鍵。和(he)有(you)的(de)(de)廠商(shang)(shang)可以用(yong)兩相供電(dian)(dian)做(zuo)出比一(yi)(yi)些廠商(shang)(shang)采用(yong)四相供電(dian)(dian)更(geng)穩定的(de)(de)產品一(yi)(yi)樣，一(yi)(yi)味的(de)(de)采用(yong)高價電(dian)(dian)容(rong)(rong)，不一(yi)(yi)定能做(zuo)出好產品。衡量(liang)一(yi)(yi)個產品，一(yi)(yi)定要全方位多角度(du)的(de)(de)去(qu)考慮，切(qie)不可把(ba)電(dian)(dian)容(rong)(rong)的(de)(de)作用(yong)有(you)意(yi)(yi)無意(yi)(yi)的(de)(de)夸大。
B. 電容爆漿之(zhi)面(mian)面(mian)談
爆漿的種類：
分兩類，輸入電容(rong)爆漿和輸出電容(rong)爆漿。
對(dui)于輸入電(dian)容(rong)來說(shuo)，就(jiu)是我是說(shuo)的(de)C1，C1對(dui)由電(dian)源接收到的(de)電(dian)流進行過(guo)濾。輸入電(dian)容(rong)爆漿和(he)電(dian)源輸入電(dian)流的(de)品質有關。過(guo)多的(de)毛刺(ci)電(dian)壓，峰(feng)值(zhi)電(dian)壓過(guo)高(gao)，電(dian)流不穩(wen)定等都使(shi)電(dian)容(rong)過(guo)于充(chong)放電(dian)過(guo)于頻繁(fan)，長時(shi)間(jian)處于這類工作環境下的(de)電(dian)容(rong)，內部(bu)溫(wen)度升高(gao)很快。超過(guo)泄爆口的(de)承(cheng)受極(ji)限就(jiu)會發生爆漿。
對于(yu)輸出電容來(lai)說，就我說的C2，對經電源模塊調整后的電流進行濾波。此處電流經過一次過濾，比較平穩，發生(sheng)爆(bao)漿的可能性(xing)相對來(lai)說小(xiao)了(le)不少。但如果(guo)環境溫度過高，電容同樣容易(yi)發生(sheng)爆(bao)漿。爆(bao)，報也。采用垃圾東(dong)西自然要(yao)爆(bao)，報應啊。欲知(zhi)過去因(yin)者，見(jian)其(qi)現在(zai)果(guo);欲知(zhi)未來(lai)果(guo)者，見(jian)其(qi)現在(zai)因(yin)。
電解(jie)電容爆漿(jiang)的原因：
電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)爆(bao)漿(jiang)的(de)(de)(de)(de)原因(yin)(yin)有(you)很多，比如(ru)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流大(da)于允許的(de)(de)(de)(de)穩(wen)波電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流、使(shi)(shi)用電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓超(chao)出工(gong)作(zuo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓、逆向電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓、頻繁的(de)(de)(de)(de)充放電(dian)(dian)(dian)(dian)(dian)(dian)(dian)等。但是(shi)(shi)(shi)(shi)(shi)最(zui)直(zhi)接的(de)(de)(de)(de)原因(yin)(yin)就(jiu)(jiu)是(shi)(shi)(shi)(shi)(shi)高(gao)溫(wen)。我們知道電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)有(you)一個重要(yao)的(de)(de)(de)(de)參(can)數就(jiu)(jiu)是(shi)(shi)(shi)(shi)(shi)耐溫(wen)值，指的(de)(de)(de)(de)就(jiu)(jiu)是(shi)(shi)(shi)(shi)(shi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)內部(bu)(bu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)解液(ye)的(de)(de)(de)(de)沸(fei)(fei)點(dian)。當(dang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)的(de)(de)(de)(de)內部(bu)(bu)溫(wen)度(du)(du)(du)達(da)到電(dian)(dian)(dian)(dian)(dian)(dian)(dian)解液(ye)的(de)(de)(de)(de)沸(fei)(fei)點(dian)時，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)解液(ye)開始沸(fei)(fei)騰，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)內部(bu)(bu)的(de)(de)(de)(de)壓力(li)升(sheng)高(gao)，當(dang)壓力(li)超(chao)過泄爆(bao)口的(de)(de)(de)(de)承受極限就(jiu)(jiu)發(fa)生(sheng)了(le)爆(bao)漿(jiang)。所以說溫(wen)度(du)(du)(du)是(shi)(shi)(shi)(shi)(shi)導致電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)爆(bao)漿(jiang)的(de)(de)(de)(de)直(zhi)接原因(yin)(yin)。電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)設計使(shi)(shi)用壽(shou)命(ming)(ming)(ming)大(da)約(yue)為(wei)2萬小時，受環(huan)境溫(wen)度(du)(du)(du)的(de)(de)(de)(de)影響也很大(da)。電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)的(de)(de)(de)(de)使(shi)(shi)用壽(shou)命(ming)(ming)(ming)隨溫(wen)度(du)(du)(du)的(de)(de)(de)(de)增加而減(jian)小，實(shi)驗證(zheng)明環(huan)境溫(wen)度(du)(du)(du)每升(sheng)高(gao)10℃，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)的(de)(de)(de)(de)壽(shou)命(ming)(ming)(ming)就(jiu)(jiu)會減(jian)半。主要(yao)原因(yin)(yin)就(jiu)(jiu)是(shi)(shi)(shi)(shi)(shi)溫(wen)度(du)(du)(du)加速化(hua)學反應而使(shi)(shi)介質隨時間退化(hua)失效(xiao)，這樣電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)壽(shou)命(ming)(ming)(ming)終結。為(wei)了(le)保證(zheng)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)的(de)(de)(de)(de)穩(wen)定性，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)在(zai)插板前要(yao)經過長(chang)時間的(de)(de)(de)(de)高(gao)溫(wen)環(huan)境的(de)(de)(de)(de)測試。即使(shi)(shi)是(shi)(shi)(shi)(shi)(shi)在(zai)100℃，高(gao)品質的(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)也可以工(gong)作(zuo)幾千(qian)個小時。同(tong)時，我們提到的(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)的(de)(de)(de)(de)壽(shou)命(ming)(ming)(ming)是(shi)(shi)(shi)(shi)(shi)指電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)在(zai)使(shi)(shi)用過程中，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)容(rong)(rong)(rong)(rong)(rong)(rong)量不會超(chao)過標準范(fan)圍變化(hua)的(de)(de)(de)(de)10%。電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)壽(shou)命(ming)(ming)(ming)指的(de)(de)(de)(de)是(shi)(shi)(shi)(shi)(shi)電(dian)(dian)(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)問題，而不是(shi)(shi)(shi)(shi)(shi)設計壽(shou)命(ming)(ming)(ming)到達(da)之后就(jiu)(jiu)發(fa)生(sheng)爆(bao)漿(jiang)。只(zhi)是(shi)(shi)(shi)(shi)(shi)無法保證(zheng)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)的(de)(de)(de)(de)設計的(de)(de)(de)(de)容(rong)(rong)(rong)(rong)(rong)(rong)量標準。
所以，短時期內，正(zheng)常(chang)使(shi)用(yong)的板卡電(dian)容(rong)(rong)就發生爆(bao)漿的情況，這就是電(dian)容(rong)(rong)品質(zhi)問題。另(ling)外(wai)，不正(zheng)常(chang)的使(shi)用(yong)情況也有可能發生電(dian)容(rong)(rong)爆(bao)漿的情況。比如熱插拔電(dian)腦配件也會導致板卡局部電(dian)路電(dian)流、電(dian)壓(ya)的劇(ju)烈變化，從而(er)引發電(dian)容(rong)(rong)使(shi)用(yong)故障。
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