詳解電容在電源中所起到的作用
2019/7/1 12:46:11??????點擊：
作(zuo)為無源元件(jian)之一的(de)電(dian)容(rong)，其(qi)作(zuo)用不外乎以下幾種(zhong)：
1、應用于電(dian)源電(dian)路，實現旁路、去藕、濾(lv)波和(he)儲能(neng)方(fang)面電(dian)容的(de)作用，下面分類詳(xiang)述之：
1)濾(lv)波
濾(lv)波是(shi)電(dian)(dian)容(rong)(rong)(rong)(rong)的(de)(de)(de)(de)作用中很重要的(de)(de)(de)(de)一部(bu)分。幾(ji)乎(hu)所有的(de)(de)(de)(de)電(dian)(dian)源電(dian)(dian)路中都會(hui)用到(dao)。從(cong)理論上(shang)(即假設(she)電(dian)(dian)容(rong)(rong)(rong)(rong)為(wei)純(chun)電(dian)(dian)容(rong)(rong)(rong)(rong))說，電(dian)(dian)容(rong)(rong)(rong)(rong)越大(da)，阻抗越小(xiao)(xiao)，通(tong)(tong)過的(de)(de)(de)(de)頻(pin)(pin)(pin)(pin)(pin)率(lv)也越高(gao)(gao)。但實際上(shang)超過1uF的(de)(de)(de)(de)電(dian)(dian)容(rong)(rong)(rong)(rong)大(da)多為(wei)電(dian)(dian)解(jie)電(dian)(dian)容(rong)(rong)(rong)(rong)，有很大(da)的(de)(de)(de)(de)電(dian)(dian)感成份，所以頻(pin)(pin)(pin)(pin)(pin)率(lv)高(gao)(gao)后反而(er)阻抗會(hui)增大(da)。有時會(hui)看到(dao)有一個電(dian)(dian)容(rong)(rong)(rong)(rong)量較大(da)電(dian)(dian)解(jie)電(dian)(dian)容(rong)(rong)(rong)(rong)并聯了一個小(xiao)(xiao)電(dian)(dian)容(rong)(rong)(rong)(rong)，這時大(da)電(dian)(dian)容(rong)(rong)(rong)(rong)通(tong)(tong)低頻(pin)(pin)(pin)(pin)(pin)，小(xiao)(xiao)電(dian)(dian)容(rong)(rong)(rong)(rong)通(tong)(tong)高(gao)(gao)頻(pin)(pin)(pin)(pin)(pin)。電(dian)(dian)容(rong)(rong)(rong)(rong)的(de)(de)(de)(de)作用就是(shi)通(tong)(tong)高(gao)(gao)阻低，通(tong)(tong)高(gao)(gao)頻(pin)(pin)(pin)(pin)(pin)阻低頻(pin)(pin)(pin)(pin)(pin)。電(dian)(dian)容(rong)(rong)(rong)(rong)越大(da)低頻(pin)(pin)(pin)(pin)(pin)越容(rong)(rong)(rong)(rong)易通(tong)(tong)過，電(dian)(dian)容(rong)(rong)(rong)(rong)越大(da)高(gao)(gao)頻(pin)(pin)(pin)(pin)(pin)越容(rong)(rong)(rong)(rong)易通(tong)(tong)過。具體用在濾(lv)波中,大(da)電(dian)(dian)容(rong)(rong)(rong)(rong)(1000uF)濾(lv)低頻(pin)(pin)(pin)(pin)(pin)，小(xiao)(xiao)電(dian)(dian)容(rong)(rong)(rong)(rong)(20pF)濾(lv)高(gao)(gao)頻(pin)(pin)(pin)(pin)(pin)。
曾(ceng)有網友將(jiang)濾(lv)波(bo)電容(rong) 比作“水(shui)塘(tang)”。由于電容(rong)的(de)兩端電壓不(bu)會突變，由此可(ke)知，信號頻率(lv)越(yue)高則衰(shuai)減越(yue)大，可(ke)很形象的(de)說電容(rong)像(xiang)個(ge)水(shui)塘(tang)，不(bu)會因幾滴(di)水(shui)的(de)加入或蒸(zheng)發而引起(qi)水(shui)量的(de)變化。 它把電壓的(de)變動轉化為電流的(de)變化，頻率(lv)越(yue)高，峰值電流就越(yue)大，從而緩(huan)沖了電壓。濾(lv)波(bo)就是充電，放電的(de)過(guo)程。
2)旁路
旁(pang)路電(dian)(dian)(dian)容是為本地(di)(di)器(qi)件(jian)(jian)提供(gong)能量(liang)的(de)儲能器(qi)件(jian)(jian)，它(ta)能使(shi)穩壓器(qi)的(de)輸(shu)出均勻(yun)化，降(jiang)低負(fu)載需求(qiu)。就(jiu)像小(xiao)型可充電(dian)(dian)(dian)電(dian)(dian)(dian)池一樣，旁(pang)路電(dian)(dian)(dian)容能夠被充電(dian)(dian)(dian)，并向器(qi)件(jian)(jian)進行放(fang) 電(dian)(dian)(dian)。為盡量(liang)減少阻抗(kang)，旁(pang)路電(dian)(dian)(dian)容要盡量(liang)靠(kao)近負(fu)載器(qi)件(jian)(jian)的(de)供(gong)電(dian)(dian)(dian)電(dian)(dian)(dian)源管(guan)(guan)腳和地(di)(di)管(guan)(guan)腳。這能夠很好地(di)(di)防止輸(shu)入值過大(da)而(er)導致的(de)地(di)(di)電(dian)(dian)(dian)位(wei)抬高和噪聲。地(di)(di)彈是地(di)(di)連接處在通過大(da) 電(dian)(dian)(dian)流毛刺時的(de)電(dian)(dian)(dian)壓降(jiang)。
3)去藕
去藕，又稱解藕。從電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)(lu)來說(shuo)，總是可以區分為(wei)驅動(dong)(dong)的(de)(de)(de)(de)(de)(de)源(yuan)和被驅動(dong)(dong)的(de)(de)(de)(de)(de)(de)負載。如果負載電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容比(bi)較(jiao)大(da)，驅動(dong)(dong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)(lu)要把(ba)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容充電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)、放電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)，才能完成信(xin)(xin)號(hao)的(de)(de)(de)(de)(de)(de)跳(tiao)變，在上 升(sheng)沿比(bi)較(jiao)陡峭的(de)(de)(de)(de)(de)(de)時候，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流比(bi)較(jiao)大(da)，這(zhe)樣驅動(dong)(dong)的(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流就(jiu)會吸收很大(da)的(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流，由(you)于電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)(lu)中的(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)感，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(特(te)別是芯片管腳上的(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)感，會產生反彈)，這(zhe)種電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流相對(dui) 于正(zheng)常(chang)情(qing)況(kuang)來說(shuo)實(shi)際(ji)上就(jiu)是一種噪聲，會影響前級的(de)(de)(de)(de)(de)(de)正(zheng)常(chang)工(gong)作。這(zhe)就(jiu)是耦(ou)合。去藕電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容就(jiu)是起(qi)到一個電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池的(de)(de)(de)(de)(de)(de)作用，滿足驅動(dong)(dong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)(lu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流的(de)(de)(de)(de)(de)(de)變化(hua)，避免(mian)相互(hu)間的(de)(de)(de)(de)(de)(de)耦(ou)合干擾(rao)。將(jiang)旁路(lu)(lu)(lu)(lu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容和去藕電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容結合起(qi)來將(jiang)更(geng)容易(yi)理解。旁路(lu)(lu)(lu)(lu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容實(shi)際(ji)也是去藕合的(de)(de)(de)(de)(de)(de)，只是旁路(lu)(lu)(lu)(lu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容一般(ban)(ban)是指高(gao)頻旁路(lu)(lu)(lu)(lu)，也就(jiu)是給高(gao)頻的(de)(de)(de)(de)(de)(de)開關(guan)噪聲提高(gao)一條低阻(zu)抗泄防 途徑。高(gao)頻旁路(lu)(lu)(lu)(lu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容一般(ban)(ban)比(bi)較(jiao)小(xiao)，根據(ju)諧振頻率一般(ban)(ban)是0.1u，0.01u等，而去耦(ou)合電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容一般(ban)(ban)比(bi)較(jiao)大(da)，是10uF或(huo)者更(geng)大(da)，依(yi)據(ju)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)(lu)中分布參數，以及(ji)驅動(dong)(dong) 電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流的(de)(de)(de)(de)(de)(de)變化(hua)大(da)小(xiao)來確定。旁路(lu)(lu)(lu)(lu)是把(ba)輸入(ru)信(xin)(xin)號(hao)中的(de)(de)(de)(de)(de)(de)干擾(rao)作為(wei)濾除對(dui)象，而去耦(ou)是把(ba)輸出(chu)信(xin)(xin)號(hao)的(de)(de)(de)(de)(de)(de)干擾(rao)作為(wei)濾除對(dui)象，防止干擾(rao)信(xin)(xin)號(hao)返回電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)。這(zhe)應該是他們的(de)(de)(de)(de)(de)(de)本質區別。
4)儲(chu)能
儲能型電(dian)(dian)容器(qi)(qi)通過整(zheng)流器(qi)(qi)收(shou)集電(dian)(dian)荷，并(bing)將存儲的(de)能量通過變換器(qi)(qi)引線傳送(song)至電(dian)(dian)源(yuan)的(de)輸出端。電(dian)(dian)壓(ya)額定值為40～450VDC、電(dian)(dian)容值在220～150 000uF之間(jian)的(de)鋁電(dian)(dian)解電(dian)(dian)容器(qi)(qi)(如EPCOS公司的(de) B43504或B43505)是較為常用的(de)。根據不同的(de)電(dian)(dian)源(yuan)要(yao)求，器(qi)(qi)件(jian)有時會采用串聯(lian)、并(bing)聯(lian)或其組合(he)的(de)形式， 對于(yu)功(gong)率級超過10KW的(de)電(dian)(dian)源(yuan)，通常采用體(ti)積較大的(de)罐形螺旋端子電(dian)(dian)容器(qi)(qi)。
2、應用于信號電路，主要完(wan)成耦合、振(zhen)蕩/同步及時間常數的作用：
1)耦合
舉個例子來(lai)講，晶體管(guan)放大(da)器(qi)發射極有一(yi)個自給偏壓電(dian)阻，它同時又(you)使信(xin)號(hao)產(chan)生壓降(jiang)反饋到輸入(ru)端形(xing)成了輸入(ru)輸出(chu)信(xin)號(hao)耦(ou)合，這(zhe)個電(dian)阻就是產(chan)生了耦(ou)合的元件(jian)，如果在這(zhe)個電(dian)阻兩端并聯一(yi)個電(dian)容，由于適當容量的電(dian)容器(qi)對交(jiao)流信(xin)號(hao)較小(xiao)的阻抗,這(zhe)樣就減小(xiao)了電(dian)阻產(chan)生的耦(ou)合效應(ying)，故稱(cheng)此電(dian)容為去耦(ou)電(dian)容。
2)振蕩/同(tong)步(bu)
包括RC、LC振(zhen)蕩器及晶體的負載電容都(dou)屬于(yu)這一范疇。
3)時間常(chang)數
這(zhe)就(jiu)是常見的(de) R、C 串(chuan)聯構(gou)成的(de)積分電(dian)(dian)(dian)(dian)路。當(dang)輸入信號(hao)電(dian)(dian)(dian)(dian)壓(ya)加在輸入端時，電(dian)(dian)(dian)(dian)容(rong)(C)上(shang)的(de)電(dian)(dian)(dian)(dian)壓(ya)逐漸上(shang)升(sheng)。而(er)其充電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流則隨(sui)著(zhu)電(dian)(dian)(dian)(dian)壓(ya)的(de)上(shang)升(sheng)而(er)減(jian)小。電(dian)(dian)(dian)(dian)流通(tong)過(guo)(guo)電(dian)(dian)(dian)(dian)阻(zu)(R)、電(dian)(dian)(dian)(dian)容(rong)(C)的(de)特性通(tong)過(guo)(guo)下面(mian)的(de)公(gong)式描述：
i = (V/R)e-(t/CR)
我們(men)知道了電容(rong)的(de)作用(yong)以后下面來談(tan)談(tan)電容(rong)在使用(yong)中(zhong)的(de)注意事(shi)項
A. 什么是好電容。
1.電容(rong)容(rong)量越(yue)大越(yue)好。
很多(duo)人(ren)在電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)的(de)(de)替(ti)換(huan)中往往愛用大容(rong)(rong)量的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)。我們知道(dao)雖然電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)越(yue)(yue)(yue)大，為IC提供(gong)的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)補(bu)(bu)償的(de)(de)能力(li)越(yue)(yue)(yue)強。且不(bu)說電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)容(rong)(rong)量的(de)(de)增大帶(dai)來的(de)(de)體積變大，增加(jia)成本的(de)(de)同時還(huan)影響空(kong)氣(qi)流(liu)動和散熱。關鍵(jian)在于電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)上存在寄生電(dian)(dian)(dian)(dian)(dian)(dian)感，電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)放電(dian)(dian)(dian)(dian)(dian)(dian)回路會在某個頻(pin)(pin)點上發生諧(xie)振(zhen)。在諧(xie)振(zhen)點，電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)的(de)(de)阻(zu)抗(kang)小(xiao)(xiao)。因此放電(dian)(dian)(dian)(dian)(dian)(dian)回路的(de)(de)阻(zu)抗(kang)最小(xiao)(xiao)，補(bu)(bu)充能量的(de)(de)效果也最好(hao)。但當頻(pin)(pin)率超過諧(xie)振(zhen)點時，放電(dian)(dian)(dian)(dian)(dian)(dian)回路的(de)(de)阻(zu)抗(kang)開始增加(jia)，電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)提供(gong)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)能力(li)便開始下降。電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)的(de)(de)容(rong)(rong)值(zhi)越(yue)(yue)(yue)大，諧(xie)振(zhen)頻(pin)(pin)率越(yue)(yue)(yue)低，電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)能有效補(bu)(bu)償電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)的(de)(de)頻(pin)(pin)率范圍也越(yue)(yue)(yue)小(xiao)(xiao)。從保證電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)提供(gong)高(gao)頻(pin)(pin)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)的(de)(de)能力(li)的(de)(de)角度來說，電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)越(yue)(yue)(yue)大越(yue)(yue)(yue)好(hao)的(de)(de)觀點是錯誤的(de)(de)，一般的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)路設計中都有一個參考值(zhi)的(de)(de)。
2.同樣(yang)容(rong)量的電容(rong)，并聯(lian)越多的小電容(rong)越好
耐壓值(zhi)、耐溫值(zhi)、容值(zhi)、ESR(等(deng)效電阻)等(deng)是(shi)(shi)電容的幾個(ge)重要(yao)參數，對于ESR自然是(shi)(shi)越(yue)低(di)越(yue)好。ESR與電容的容量(liang)、頻率、電壓、溫度等(deng)都有(you)關系。當電壓固定時(shi)候(hou)，容量(liang)越(yue)大，ESR越(yue)低(di)。在板卡設(she)計中采用多個(ge)小電容并(bing)(bing)連多是(shi)(shi)出與PCB空間的限制，這樣有(you)的人就認為，越(yue)多的并(bing)(bing)聯(lian)小電阻，ESR越(yue)低(di)，效果(guo)越(yue)好。理論上是(shi)(shi)如(ru)此，但是(shi)(shi)要(yao)考慮到電容接腳焊點的阻抗(kang)，采用多個(ge)小電容并(bing)(bing)聯(lian)，效果(guo)并(bing)(bing)不一定突出。
3.ESR越低，效(xiao)果越好。
結合我們上面的(de)提(ti)高(gao)(gao)的(de)供電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)路(lu)來(lai)說(shuo)，對(dui)于輸(shu)入(ru)電(dian)(dian)(dian)(dian)容(rong)(rong)來(lai)說(shuo)，輸(shu)入(ru)電(dian)(dian)(dian)(dian)容(rong)(rong)的(de)容(rong)(rong)量要(yao)(yao)大(da)一(yi)(yi)(yi)點(dian)(dian)。相對(dui)容(rong)(rong)量的(de)要(yao)(yao)求(qiu)，對(dui)ESR的(de)要(yao)(yao)求(qiu)可以適當的(de)降(jiang)低(di)。因為(wei)輸(shu)入(ru)電(dian)(dian)(dian)(dian)容(rong)(rong)主要(yao)(yao)是耐壓(ya)，其(qi)次是吸收MOSFET的(de)開關(guan)脈沖(chong)。對(dui)于輸(shu)出電(dian)(dian)(dian)(dian)容(rong)(rong)來(lai)說(shuo)，耐壓(ya)的(de)要(yao)(yao)求(qiu)和容(rong)(rong)量可以適當的(de)降(jiang)低(di)一(yi)(yi)(yi)點(dian)(dian)。ESR的(de)要(yao)(yao)求(qiu)則高(gao)(gao)一(yi)(yi)(yi)點(dian)(dian)，因為(wei)這里要(yao)(yao)保證的(de)是足夠的(de)電(dian)(dian)(dian)(dian)流(liu)通過量。但這里要(yao)(yao)注意的(de)是ESR并(bing)不是越低(di)越好，低(di)ESR電(dian)(dian)(dian)(dian)容(rong)(rong)會引起開關(guan)電(dian)(dian)(dian)(dian)路(lu)振蕩。而消振電(dian)(dian)(dian)(dian)路(lu)復(fu)雜同時會導致成本(ben)的(de)增加。板卡設計中，這里一(yi)(yi)(yi)般有一(yi)(yi)(yi)個(ge)參考值(zhi)，此作為(wei)元件選(xuan)用(yong)參數，避免消振電(dian)(dian)(dian)(dian)路(lu)而導致成本(ben)的(de)增加。
4.好電(dian)容代表(biao)著高品質。
“唯電(dian)(dian)容(rong)(rong)論”曾經盛極一(yi)(yi)(yi)時(shi)，一(yi)(yi)(yi)些廠商和媒體(ti)也刻意的(de)把這個(ge)(ge)事(shi)情做(zuo)成(cheng)一(yi)(yi)(yi)個(ge)(ge)賣(mai)點。在板卡設計中，電(dian)(dian)路設計水平(ping)是關鍵(jian)。和有的(de)廠商可(ke)以(yi)用(yong)兩相供電(dian)(dian)做(zuo)出(chu)比一(yi)(yi)(yi)些廠商采(cai)用(yong)四(si)相供電(dian)(dian)更穩定的(de)產(chan)品(pin)一(yi)(yi)(yi)樣，一(yi)(yi)(yi)味的(de)采(cai)用(yong)高價電(dian)(dian)容(rong)(rong)，不一(yi)(yi)(yi)定能做(zuo)出(chu)好產(chan)品(pin)。衡(heng)量一(yi)(yi)(yi)個(ge)(ge)產(chan)品(pin)，一(yi)(yi)(yi)定要全方位(wei)多角度的(de)去(qu)考慮，切不可(ke)把電(dian)(dian)容(rong)(rong)的(de)作用(yong)有意無意的(de)夸(kua)大。
B. 電容爆漿(jiang)之面(mian)面(mian)談
爆漿的(de)種類：
分兩類，輸(shu)入(ru)電容爆漿(jiang)和輸(shu)出電容爆漿(jiang)。
對于(yu)輸入電(dian)(dian)(dian)(dian)容來說(shuo)，就(jiu)是我是說(shuo)的(de)C1，C1對由電(dian)(dian)(dian)(dian)源接收到(dao)的(de)電(dian)(dian)(dian)(dian)流進行過(guo)(guo)(guo)濾。輸入電(dian)(dian)(dian)(dian)容爆(bao)(bao)漿和(he)電(dian)(dian)(dian)(dian)源輸入電(dian)(dian)(dian)(dian)流的(de)品質(zhi)有關。過(guo)(guo)(guo)多的(de)毛刺電(dian)(dian)(dian)(dian)壓，峰(feng)值電(dian)(dian)(dian)(dian)壓過(guo)(guo)(guo)高，電(dian)(dian)(dian)(dian)流不穩定等都使電(dian)(dian)(dian)(dian)容過(guo)(guo)(guo)于(yu)充放電(dian)(dian)(dian)(dian)過(guo)(guo)(guo)于(yu)頻繁，長時(shi)間處于(yu)這類工作(zuo)環(huan)境(jing)下的(de)電(dian)(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(shou)極限就(jiu)會(hui)發生爆(bao)(bao)漿。
對(dui)于輸出電(dian)容(rong)來(lai)說(shuo)(shuo)，就我說(shuo)(shuo)的C2，對(dui)經電(dian)源模塊調整(zheng)后的電(dian)流(liu)進行(xing)濾(lv)波。此處(chu)電(dian)流(liu)經過一(yi)次過濾(lv)，比較平穩，發(fa)生(sheng)(sheng)爆(bao)漿的可能(neng)性(xing)相對(dui)來(lai)說(shuo)(shuo)小了不少。但如果環(huan)境溫度過高，電(dian)容(rong)同樣容(rong)易發(fa)生(sheng)(sheng)爆(bao)漿。爆(bao)，報也(ye)。采用垃(la)圾東西自(zi)然要爆(bao)，報應啊。欲知過去因者，見(jian)其現(xian)在(zai)果;欲知未來(lai)果者，見(jian)其現(xian)在(zai)因。
電解電容爆漿的原因：
電(dian)(dian)(dian)容(rong)(rong)(rong)爆漿的(de)(de)(de)(de)(de)(de)(de)(de)原(yuan)(yuan)(yuan)因(yin)有很多，比如(ru)電(dian)(dian)(dian)流大于允許的(de)(de)(de)(de)(de)(de)(de)(de)穩波電(dian)(dian)(dian)流、使(shi)(shi)用(yong)電(dian)(dian)(dian)壓(ya)超(chao)出工作電(dian)(dian)(dian)壓(ya)、逆向(xiang)電(dian)(dian)(dian)壓(ya)、頻繁(fan)的(de)(de)(de)(de)(de)(de)(de)(de)充放電(dian)(dian)(dian)等。但是最(zui)直接(jie)的(de)(de)(de)(de)(de)(de)(de)(de)原(yuan)(yuan)(yuan)因(yin)就(jiu)是高(gao)(gao)溫(wen)。我(wo)們知(zhi)道電(dian)(dian)(dian)容(rong)(rong)(rong)有一個重要的(de)(de)(de)(de)(de)(de)(de)(de)參數就(jiu)是耐溫(wen)值(zhi)，指的(de)(de)(de)(de)(de)(de)(de)(de)就(jiu)是電(dian)(dian)(dian)容(rong)(rong)(rong)內部電(dian)(dian)(dian)解(jie)液的(de)(de)(de)(de)(de)(de)(de)(de)沸點。當(dang)電(dian)(dian)(dian)容(rong)(rong)(rong)的(de)(de)(de)(de)(de)(de)(de)(de)內部溫(wen)度(du)(du)(du)達(da)到電(dian)(dian)(dian)解(jie)液的(de)(de)(de)(de)(de)(de)(de)(de)沸點時，電(dian)(dian)(dian)解(jie)液開始沸騰(teng)，電(dian)(dian)(dian)容(rong)(rong)(rong)內部的(de)(de)(de)(de)(de)(de)(de)(de)壓(ya)力升高(gao)(gao)，當(dang)壓(ya)力超(chao)過(guo)泄(xie)爆口的(de)(de)(de)(de)(de)(de)(de)(de)承受(shou)極(ji)限就(jiu)發(fa)生(sheng)了(le)(le)爆漿。所以說溫(wen)度(du)(du)(du)是導致電(dian)(dian)(dian)容(rong)(rong)(rong)爆漿的(de)(de)(de)(de)(de)(de)(de)(de)直接(jie)原(yuan)(yuan)(yuan)因(yin)。電(dian)(dian)(dian)容(rong)(rong)(rong)設(she)計使(shi)(shi)用(yong)壽(shou)(shou)命(ming)(ming)(ming)大約為2萬小(xiao)時，受(shou)環境溫(wen)度(du)(du)(du)的(de)(de)(de)(de)(de)(de)(de)(de)影響也很大。電(dian)(dian)(dian)容(rong)(rong)(rong)的(de)(de)(de)(de)(de)(de)(de)(de)使(shi)(shi)用(yong)壽(shou)(shou)命(ming)(ming)(ming)隨溫(wen)度(du)(du)(du)的(de)(de)(de)(de)(de)(de)(de)(de)增加而減小(xiao)，實驗證明環境溫(wen)度(du)(du)(du)每(mei)升高(gao)(gao)10℃，電(dian)(dian)(dian)容(rong)(rong)(rong)的(de)(de)(de)(de)(de)(de)(de)(de)壽(shou)(shou)命(ming)(ming)(ming)就(jiu)會減半(ban)。主要原(yuan)(yuan)(yuan)因(yin)就(jiu)是溫(wen)度(du)(du)(du)加速化(hua)(hua)學反應而使(shi)(shi)介質隨時間退化(hua)(hua)失效，這樣電(dian)(dian)(dian)容(rong)(rong)(rong)壽(shou)(shou)命(ming)(ming)(ming)終結。為了(le)(le)保證電(dian)(dian)(dian)容(rong)(rong)(rong)的(de)(de)(de)(de)(de)(de)(de)(de)穩定性(xing)，電(dian)(dian)(dian)容(rong)(rong)(rong)在(zai)插板前要經過(guo)長時間的(de)(de)(de)(de)(de)(de)(de)(de)高(gao)(gao)溫(wen)環境的(de)(de)(de)(de)(de)(de)(de)(de)測(ce)試。即使(shi)(shi)是在(zai)100℃，高(gao)(gao)品(pin)質的(de)(de)(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)容(rong)(rong)(rong)也可以工作幾千個小(xiao)時。同時，我(wo)們提到的(de)(de)(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)容(rong)(rong)(rong)的(de)(de)(de)(de)(de)(de)(de)(de)壽(shou)(shou)命(ming)(ming)(ming)是指電(dian)(dian)(dian)容(rong)(rong)(rong)在(zai)使(shi)(shi)用(yong)過(guo)程中(zhong)，電(dian)(dian)(dian)容(rong)(rong)(rong)容(rong)(rong)(rong)量(liang)不會超(chao)過(guo)標準(zhun)范(fan)圍(wei)變化(hua)(hua)的(de)(de)(de)(de)(de)(de)(de)(de)10%。電(dian)(dian)(dian)容(rong)(rong)(rong)壽(shou)(shou)命(ming)(ming)(ming)指的(de)(de)(de)(de)(de)(de)(de)(de)是電(dian)(dian)(dian)容(rong)(rong)(rong)容(rong)(rong)(rong)量(liang)的(de)(de)(de)(de)(de)(de)(de)(de)問題，而不是設(she)計壽(shou)(shou)命(ming)(ming)(ming)到達(da)之后就(jiu)發(fa)生(sheng)爆漿。只是無法保證電(dian)(dian)(dian)容(rong)(rong)(rong)的(de)(de)(de)(de)(de)(de)(de)(de)設(she)計的(de)(de)(de)(de)(de)(de)(de)(de)容(rong)(rong)(rong)量(liang)標準(zhun)。
所以，短時期內，正(zheng)(zheng)常使(shi)用(yong)(yong)的(de)板(ban)卡電(dian)(dian)(dian)容就(jiu)發(fa)生(sheng)爆(bao)漿的(de)情況(kuang)，這就(jiu)是電(dian)(dian)(dian)容品質問(wen)題(ti)。另外，不正(zheng)(zheng)常的(de)使(shi)用(yong)(yong)情況(kuang)也有可能發(fa)生(sheng)電(dian)(dian)(dian)容爆(bao)漿的(de)情況(kuang)。比如熱插拔電(dian)(dian)(dian)腦(nao)配(pei)件也會導致板(ban)卡局部電(dian)(dian)(dian)路電(dian)(dian)(dian)流、電(dian)(dian)(dian)壓的(de)劇烈變化，從而引(yin)發(fa)電(dian)(dian)(dian)容使(shi)用(yong)(yong)故(gu)障。
1、應用于電(dian)源電(dian)路，實現旁路、去藕、濾(lv)波和(he)儲能(neng)方(fang)面電(dian)容的(de)作用，下面分類詳(xiang)述之：
1)濾(lv)波
濾(lv)波是(shi)電(dian)(dian)容(rong)(rong)(rong)(rong)的(de)(de)(de)(de)作用中很重要的(de)(de)(de)(de)一部(bu)分。幾(ji)乎(hu)所有的(de)(de)(de)(de)電(dian)(dian)源電(dian)(dian)路中都會(hui)用到(dao)。從(cong)理論上(shang)(即假設(she)電(dian)(dian)容(rong)(rong)(rong)(rong)為(wei)純(chun)電(dian)(dian)容(rong)(rong)(rong)(rong))說，電(dian)(dian)容(rong)(rong)(rong)(rong)越大(da)，阻抗越小(xiao)(xiao)，通(tong)(tong)過的(de)(de)(de)(de)頻(pin)(pin)(pin)(pin)(pin)率(lv)也越高(gao)(gao)。但實際上(shang)超過1uF的(de)(de)(de)(de)電(dian)(dian)容(rong)(rong)(rong)(rong)大(da)多為(wei)電(dian)(dian)解(jie)電(dian)(dian)容(rong)(rong)(rong)(rong)，有很大(da)的(de)(de)(de)(de)電(dian)(dian)感成份，所以頻(pin)(pin)(pin)(pin)(pin)率(lv)高(gao)(gao)后反而(er)阻抗會(hui)增大(da)。有時會(hui)看到(dao)有一個電(dian)(dian)容(rong)(rong)(rong)(rong)量較大(da)電(dian)(dian)解(jie)電(dian)(dian)容(rong)(rong)(rong)(rong)并聯了一個小(xiao)(xiao)電(dian)(dian)容(rong)(rong)(rong)(rong)，這時大(da)電(dian)(dian)容(rong)(rong)(rong)(rong)通(tong)(tong)低頻(pin)(pin)(pin)(pin)(pin)，小(xiao)(xiao)電(dian)(dian)容(rong)(rong)(rong)(rong)通(tong)(tong)高(gao)(gao)頻(pin)(pin)(pin)(pin)(pin)。電(dian)(dian)容(rong)(rong)(rong)(rong)的(de)(de)(de)(de)作用就是(shi)通(tong)(tong)高(gao)(gao)阻低，通(tong)(tong)高(gao)(gao)頻(pin)(pin)(pin)(pin)(pin)阻低頻(pin)(pin)(pin)(pin)(pin)。電(dian)(dian)容(rong)(rong)(rong)(rong)越大(da)低頻(pin)(pin)(pin)(pin)(pin)越容(rong)(rong)(rong)(rong)易通(tong)(tong)過，電(dian)(dian)容(rong)(rong)(rong)(rong)越大(da)高(gao)(gao)頻(pin)(pin)(pin)(pin)(pin)越容(rong)(rong)(rong)(rong)易通(tong)(tong)過。具體用在濾(lv)波中,大(da)電(dian)(dian)容(rong)(rong)(rong)(rong)(1000uF)濾(lv)低頻(pin)(pin)(pin)(pin)(pin)，小(xiao)(xiao)電(dian)(dian)容(rong)(rong)(rong)(rong)(20pF)濾(lv)高(gao)(gao)頻(pin)(pin)(pin)(pin)(pin)。
曾(ceng)有網友將(jiang)濾(lv)波(bo)電容(rong) 比作“水(shui)塘(tang)”。由于電容(rong)的(de)兩端電壓不(bu)會突變，由此可(ke)知，信號頻率(lv)越(yue)高則衰(shuai)減越(yue)大，可(ke)很形象的(de)說電容(rong)像(xiang)個(ge)水(shui)塘(tang)，不(bu)會因幾滴(di)水(shui)的(de)加入或蒸(zheng)發而引起(qi)水(shui)量的(de)變化。 它把電壓的(de)變動轉化為電流的(de)變化，頻率(lv)越(yue)高，峰值電流就越(yue)大，從而緩(huan)沖了電壓。濾(lv)波(bo)就是充電，放電的(de)過(guo)程。
2)旁路
旁(pang)路電(dian)(dian)(dian)容是為本地(di)(di)器(qi)件(jian)(jian)提供(gong)能量(liang)的(de)儲能器(qi)件(jian)(jian)，它(ta)能使(shi)穩壓器(qi)的(de)輸(shu)出均勻(yun)化，降(jiang)低負(fu)載需求(qiu)。就(jiu)像小(xiao)型可充電(dian)(dian)(dian)電(dian)(dian)(dian)池一樣，旁(pang)路電(dian)(dian)(dian)容能夠被充電(dian)(dian)(dian)，并向器(qi)件(jian)(jian)進行放(fang) 電(dian)(dian)(dian)。為盡量(liang)減少阻抗(kang)，旁(pang)路電(dian)(dian)(dian)容要盡量(liang)靠(kao)近負(fu)載器(qi)件(jian)(jian)的(de)供(gong)電(dian)(dian)(dian)電(dian)(dian)(dian)源管(guan)(guan)腳和地(di)(di)管(guan)(guan)腳。這能夠很好地(di)(di)防止輸(shu)入值過大(da)而(er)導致的(de)地(di)(di)電(dian)(dian)(dian)位(wei)抬高和噪聲。地(di)(di)彈是地(di)(di)連接處在通過大(da) 電(dian)(dian)(dian)流毛刺時的(de)電(dian)(dian)(dian)壓降(jiang)。
3)去藕
去藕，又稱解藕。從電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)(lu)來說(shuo)，總是可以區分為(wei)驅動(dong)(dong)的(de)(de)(de)(de)(de)(de)源(yuan)和被驅動(dong)(dong)的(de)(de)(de)(de)(de)(de)負載。如果負載電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容比(bi)較(jiao)大(da)，驅動(dong)(dong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)(lu)要把(ba)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容充電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)、放電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)，才能完成信(xin)(xin)號(hao)的(de)(de)(de)(de)(de)(de)跳(tiao)變，在上 升(sheng)沿比(bi)較(jiao)陡峭的(de)(de)(de)(de)(de)(de)時候，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流比(bi)較(jiao)大(da)，這(zhe)樣驅動(dong)(dong)的(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流就(jiu)會吸收很大(da)的(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流，由(you)于電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)(lu)中的(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)感，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(特(te)別是芯片管腳上的(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)感，會產生反彈)，這(zhe)種電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流相對(dui) 于正(zheng)常(chang)情(qing)況(kuang)來說(shuo)實(shi)際(ji)上就(jiu)是一種噪聲，會影響前級的(de)(de)(de)(de)(de)(de)正(zheng)常(chang)工(gong)作。這(zhe)就(jiu)是耦(ou)合。去藕電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容就(jiu)是起(qi)到一個電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池的(de)(de)(de)(de)(de)(de)作用，滿足驅動(dong)(dong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)(lu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流的(de)(de)(de)(de)(de)(de)變化(hua)，避免(mian)相互(hu)間的(de)(de)(de)(de)(de)(de)耦(ou)合干擾(rao)。將(jiang)旁路(lu)(lu)(lu)(lu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容和去藕電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容結合起(qi)來將(jiang)更(geng)容易(yi)理解。旁路(lu)(lu)(lu)(lu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容實(shi)際(ji)也是去藕合的(de)(de)(de)(de)(de)(de)，只是旁路(lu)(lu)(lu)(lu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容一般(ban)(ban)是指高(gao)頻旁路(lu)(lu)(lu)(lu)，也就(jiu)是給高(gao)頻的(de)(de)(de)(de)(de)(de)開關(guan)噪聲提高(gao)一條低阻(zu)抗泄防 途徑。高(gao)頻旁路(lu)(lu)(lu)(lu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容一般(ban)(ban)比(bi)較(jiao)小(xiao)，根據(ju)諧振頻率一般(ban)(ban)是0.1u，0.01u等，而去耦(ou)合電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容一般(ban)(ban)比(bi)較(jiao)大(da)，是10uF或(huo)者更(geng)大(da)，依(yi)據(ju)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)(lu)中分布參數，以及(ji)驅動(dong)(dong) 電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流的(de)(de)(de)(de)(de)(de)變化(hua)大(da)小(xiao)來確定。旁路(lu)(lu)(lu)(lu)是把(ba)輸入(ru)信(xin)(xin)號(hao)中的(de)(de)(de)(de)(de)(de)干擾(rao)作為(wei)濾除對(dui)象，而去耦(ou)是把(ba)輸出(chu)信(xin)(xin)號(hao)的(de)(de)(de)(de)(de)(de)干擾(rao)作為(wei)濾除對(dui)象，防止干擾(rao)信(xin)(xin)號(hao)返回電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)。這(zhe)應該是他們的(de)(de)(de)(de)(de)(de)本質區別。
4)儲(chu)能
儲能型電(dian)(dian)容器(qi)(qi)通過整(zheng)流器(qi)(qi)收(shou)集電(dian)(dian)荷，并(bing)將存儲的(de)能量通過變換器(qi)(qi)引線傳送(song)至電(dian)(dian)源(yuan)的(de)輸出端。電(dian)(dian)壓(ya)額定值為40～450VDC、電(dian)(dian)容值在220～150 000uF之間(jian)的(de)鋁電(dian)(dian)解電(dian)(dian)容器(qi)(qi)(如EPCOS公司的(de) B43504或B43505)是較為常用的(de)。根據不同的(de)電(dian)(dian)源(yuan)要(yao)求，器(qi)(qi)件(jian)有時會采用串聯(lian)、并(bing)聯(lian)或其組合(he)的(de)形式， 對于(yu)功(gong)率級超過10KW的(de)電(dian)(dian)源(yuan)，通常采用體(ti)積較大的(de)罐形螺旋端子電(dian)(dian)容器(qi)(qi)。
2、應用于信號電路，主要完(wan)成耦合、振(zhen)蕩/同步及時間常數的作用：
1)耦合
舉個例子來(lai)講，晶體管(guan)放大(da)器(qi)發射極有一(yi)個自給偏壓電(dian)阻，它同時又(you)使信(xin)號(hao)產(chan)生壓降(jiang)反饋到輸入(ru)端形(xing)成了輸入(ru)輸出(chu)信(xin)號(hao)耦(ou)合，這(zhe)個電(dian)阻就是產(chan)生了耦(ou)合的元件(jian)，如果在這(zhe)個電(dian)阻兩端并聯一(yi)個電(dian)容，由于適當容量的電(dian)容器(qi)對交(jiao)流信(xin)號(hao)較小(xiao)的阻抗,這(zhe)樣就減小(xiao)了電(dian)阻產(chan)生的耦(ou)合效應(ying)，故稱(cheng)此電(dian)容為去耦(ou)電(dian)容。
2)振蕩/同(tong)步(bu)
包括RC、LC振(zhen)蕩器及晶體的負載電容都(dou)屬于(yu)這一范疇。
3)時間常(chang)數
這(zhe)就(jiu)是常見的(de) R、C 串(chuan)聯構(gou)成的(de)積分電(dian)(dian)(dian)(dian)路。當(dang)輸入信號(hao)電(dian)(dian)(dian)(dian)壓(ya)加在輸入端時，電(dian)(dian)(dian)(dian)容(rong)(C)上(shang)的(de)電(dian)(dian)(dian)(dian)壓(ya)逐漸上(shang)升(sheng)。而(er)其充電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流則隨(sui)著(zhu)電(dian)(dian)(dian)(dian)壓(ya)的(de)上(shang)升(sheng)而(er)減(jian)小。電(dian)(dian)(dian)(dian)流通(tong)過(guo)(guo)電(dian)(dian)(dian)(dian)阻(zu)(R)、電(dian)(dian)(dian)(dian)容(rong)(C)的(de)特性通(tong)過(guo)(guo)下面(mian)的(de)公(gong)式描述：
i = (V/R)e-(t/CR)
我們(men)知道了電容(rong)的(de)作用(yong)以后下面來談(tan)談(tan)電容(rong)在使用(yong)中(zhong)的(de)注意事(shi)項
A. 什么是好電容。
1.電容(rong)容(rong)量越(yue)大越(yue)好。
很多(duo)人(ren)在電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)的(de)(de)替(ti)換(huan)中往往愛用大容(rong)(rong)量的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)。我們知道(dao)雖然電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)越(yue)(yue)(yue)大，為IC提供(gong)的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)補(bu)(bu)償的(de)(de)能力(li)越(yue)(yue)(yue)強。且不(bu)說電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)容(rong)(rong)量的(de)(de)增大帶(dai)來的(de)(de)體積變大，增加(jia)成本的(de)(de)同時還(huan)影響空(kong)氣(qi)流(liu)動和散熱。關鍵(jian)在于電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)上存在寄生電(dian)(dian)(dian)(dian)(dian)(dian)感，電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)放電(dian)(dian)(dian)(dian)(dian)(dian)回路會在某個頻(pin)(pin)點上發生諧(xie)振(zhen)。在諧(xie)振(zhen)點，電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)的(de)(de)阻(zu)抗(kang)小(xiao)(xiao)。因此放電(dian)(dian)(dian)(dian)(dian)(dian)回路的(de)(de)阻(zu)抗(kang)最小(xiao)(xiao)，補(bu)(bu)充能量的(de)(de)效果也最好(hao)。但當頻(pin)(pin)率超過諧(xie)振(zhen)點時，放電(dian)(dian)(dian)(dian)(dian)(dian)回路的(de)(de)阻(zu)抗(kang)開始增加(jia)，電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)提供(gong)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)能力(li)便開始下降。電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)的(de)(de)容(rong)(rong)值(zhi)越(yue)(yue)(yue)大，諧(xie)振(zhen)頻(pin)(pin)率越(yue)(yue)(yue)低，電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)能有效補(bu)(bu)償電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)的(de)(de)頻(pin)(pin)率范圍也越(yue)(yue)(yue)小(xiao)(xiao)。從保證電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)提供(gong)高(gao)頻(pin)(pin)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)的(de)(de)能力(li)的(de)(de)角度來說，電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)越(yue)(yue)(yue)大越(yue)(yue)(yue)好(hao)的(de)(de)觀點是錯誤的(de)(de)，一般的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)路設計中都有一個參考值(zhi)的(de)(de)。
2.同樣(yang)容(rong)量的電容(rong)，并聯(lian)越多的小電容(rong)越好
耐壓值(zhi)、耐溫值(zhi)、容值(zhi)、ESR(等(deng)效電阻)等(deng)是(shi)(shi)電容的幾個(ge)重要(yao)參數，對于ESR自然是(shi)(shi)越(yue)低(di)越(yue)好。ESR與電容的容量(liang)、頻率、電壓、溫度等(deng)都有(you)關系。當電壓固定時(shi)候(hou)，容量(liang)越(yue)大，ESR越(yue)低(di)。在板卡設(she)計中采用多個(ge)小電容并(bing)(bing)連多是(shi)(shi)出與PCB空間的限制，這樣有(you)的人就認為，越(yue)多的并(bing)(bing)聯(lian)小電阻，ESR越(yue)低(di)，效果(guo)越(yue)好。理論上是(shi)(shi)如(ru)此，但是(shi)(shi)要(yao)考慮到電容接腳焊點的阻抗(kang)，采用多個(ge)小電容并(bing)(bing)聯(lian)，效果(guo)并(bing)(bing)不一定突出。
3.ESR越低，效(xiao)果越好。
結合我們上面的(de)提(ti)高(gao)(gao)的(de)供電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)路(lu)來(lai)說(shuo)，對(dui)于輸(shu)入(ru)電(dian)(dian)(dian)(dian)容(rong)(rong)來(lai)說(shuo)，輸(shu)入(ru)電(dian)(dian)(dian)(dian)容(rong)(rong)的(de)容(rong)(rong)量要(yao)(yao)大(da)一(yi)(yi)(yi)點(dian)(dian)。相對(dui)容(rong)(rong)量的(de)要(yao)(yao)求(qiu)，對(dui)ESR的(de)要(yao)(yao)求(qiu)可以適當的(de)降(jiang)低(di)。因為(wei)輸(shu)入(ru)電(dian)(dian)(dian)(dian)容(rong)(rong)主要(yao)(yao)是耐壓(ya)，其(qi)次是吸收MOSFET的(de)開關(guan)脈沖(chong)。對(dui)于輸(shu)出電(dian)(dian)(dian)(dian)容(rong)(rong)來(lai)說(shuo)，耐壓(ya)的(de)要(yao)(yao)求(qiu)和容(rong)(rong)量可以適當的(de)降(jiang)低(di)一(yi)(yi)(yi)點(dian)(dian)。ESR的(de)要(yao)(yao)求(qiu)則高(gao)(gao)一(yi)(yi)(yi)點(dian)(dian)，因為(wei)這里要(yao)(yao)保證的(de)是足夠的(de)電(dian)(dian)(dian)(dian)流(liu)通過量。但這里要(yao)(yao)注意的(de)是ESR并(bing)不是越低(di)越好，低(di)ESR電(dian)(dian)(dian)(dian)容(rong)(rong)會引起開關(guan)電(dian)(dian)(dian)(dian)路(lu)振蕩。而消振電(dian)(dian)(dian)(dian)路(lu)復(fu)雜同時會導致成本(ben)的(de)增加。板卡設計中，這里一(yi)(yi)(yi)般有一(yi)(yi)(yi)個(ge)參考值(zhi)，此作為(wei)元件選(xuan)用(yong)參數，避免消振電(dian)(dian)(dian)(dian)路(lu)而導致成本(ben)的(de)增加。
4.好電(dian)容代表(biao)著高品質。
“唯電(dian)(dian)容(rong)(rong)論”曾經盛極一(yi)(yi)(yi)時(shi)，一(yi)(yi)(yi)些廠商和媒體(ti)也刻意的(de)把這個(ge)(ge)事(shi)情做(zuo)成(cheng)一(yi)(yi)(yi)個(ge)(ge)賣(mai)點。在板卡設計中，電(dian)(dian)路設計水平(ping)是關鍵(jian)。和有的(de)廠商可(ke)以(yi)用(yong)兩相供電(dian)(dian)做(zuo)出(chu)比一(yi)(yi)(yi)些廠商采(cai)用(yong)四(si)相供電(dian)(dian)更穩定的(de)產(chan)品(pin)一(yi)(yi)(yi)樣，一(yi)(yi)(yi)味的(de)采(cai)用(yong)高價電(dian)(dian)容(rong)(rong)，不一(yi)(yi)(yi)定能做(zuo)出(chu)好產(chan)品(pin)。衡(heng)量一(yi)(yi)(yi)個(ge)(ge)產(chan)品(pin)，一(yi)(yi)(yi)定要全方位(wei)多角度的(de)去(qu)考慮，切不可(ke)把電(dian)(dian)容(rong)(rong)的(de)作用(yong)有意無意的(de)夸(kua)大。
B. 電容爆漿(jiang)之面(mian)面(mian)談
爆漿的(de)種類：
分兩類，輸(shu)入(ru)電容爆漿(jiang)和輸(shu)出電容爆漿(jiang)。
對于(yu)輸入電(dian)(dian)(dian)(dian)容來說(shuo)，就(jiu)是我是說(shuo)的(de)C1，C1對由電(dian)(dian)(dian)(dian)源接收到(dao)的(de)電(dian)(dian)(dian)(dian)流進行過(guo)(guo)(guo)濾。輸入電(dian)(dian)(dian)(dian)容爆(bao)(bao)漿和(he)電(dian)(dian)(dian)(dian)源輸入電(dian)(dian)(dian)(dian)流的(de)品質(zhi)有關。過(guo)(guo)(guo)多的(de)毛刺電(dian)(dian)(dian)(dian)壓，峰(feng)值電(dian)(dian)(dian)(dian)壓過(guo)(guo)(guo)高，電(dian)(dian)(dian)(dian)流不穩定等都使電(dian)(dian)(dian)(dian)容過(guo)(guo)(guo)于(yu)充放電(dian)(dian)(dian)(dian)過(guo)(guo)(guo)于(yu)頻繁，長時(shi)間處于(yu)這類工作(zuo)環(huan)境(jing)下的(de)電(dian)(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(shou)極限就(jiu)會(hui)發生爆(bao)(bao)漿。
對(dui)于輸出電(dian)容(rong)來(lai)說(shuo)(shuo)，就我說(shuo)(shuo)的C2，對(dui)經電(dian)源模塊調整(zheng)后的電(dian)流(liu)進行(xing)濾(lv)波。此處(chu)電(dian)流(liu)經過一(yi)次過濾(lv)，比較平穩，發(fa)生(sheng)(sheng)爆(bao)漿的可能(neng)性(xing)相對(dui)來(lai)說(shuo)(shuo)小了不少。但如果環(huan)境溫度過高，電(dian)容(rong)同樣容(rong)易發(fa)生(sheng)(sheng)爆(bao)漿。爆(bao)，報也(ye)。采用垃(la)圾東西自(zi)然要爆(bao)，報應啊。欲知過去因者，見(jian)其現(xian)在(zai)果;欲知未來(lai)果者，見(jian)其現(xian)在(zai)因。
電解電容爆漿的原因：
電(dian)(dian)(dian)容(rong)(rong)(rong)爆漿的(de)(de)(de)(de)(de)(de)(de)(de)原(yuan)(yuan)(yuan)因(yin)有很多，比如(ru)電(dian)(dian)(dian)流大于允許的(de)(de)(de)(de)(de)(de)(de)(de)穩波電(dian)(dian)(dian)流、使(shi)(shi)用(yong)電(dian)(dian)(dian)壓(ya)超(chao)出工作電(dian)(dian)(dian)壓(ya)、逆向(xiang)電(dian)(dian)(dian)壓(ya)、頻繁(fan)的(de)(de)(de)(de)(de)(de)(de)(de)充放電(dian)(dian)(dian)等。但是最(zui)直接(jie)的(de)(de)(de)(de)(de)(de)(de)(de)原(yuan)(yuan)(yuan)因(yin)就(jiu)是高(gao)(gao)溫(wen)。我(wo)們知(zhi)道電(dian)(dian)(dian)容(rong)(rong)(rong)有一個重要的(de)(de)(de)(de)(de)(de)(de)(de)參數就(jiu)是耐溫(wen)值(zhi)，指的(de)(de)(de)(de)(de)(de)(de)(de)就(jiu)是電(dian)(dian)(dian)容(rong)(rong)(rong)內部電(dian)(dian)(dian)解(jie)液的(de)(de)(de)(de)(de)(de)(de)(de)沸點。當(dang)電(dian)(dian)(dian)容(rong)(rong)(rong)的(de)(de)(de)(de)(de)(de)(de)(de)內部溫(wen)度(du)(du)(du)達(da)到電(dian)(dian)(dian)解(jie)液的(de)(de)(de)(de)(de)(de)(de)(de)沸點時，電(dian)(dian)(dian)解(jie)液開始沸騰(teng)，電(dian)(dian)(dian)容(rong)(rong)(rong)內部的(de)(de)(de)(de)(de)(de)(de)(de)壓(ya)力升高(gao)(gao)，當(dang)壓(ya)力超(chao)過(guo)泄(xie)爆口的(de)(de)(de)(de)(de)(de)(de)(de)承受(shou)極(ji)限就(jiu)發(fa)生(sheng)了(le)(le)爆漿。所以說溫(wen)度(du)(du)(du)是導致電(dian)(dian)(dian)容(rong)(rong)(rong)爆漿的(de)(de)(de)(de)(de)(de)(de)(de)直接(jie)原(yuan)(yuan)(yuan)因(yin)。電(dian)(dian)(dian)容(rong)(rong)(rong)設(she)計使(shi)(shi)用(yong)壽(shou)(shou)命(ming)(ming)(ming)大約為2萬小(xiao)時，受(shou)環境溫(wen)度(du)(du)(du)的(de)(de)(de)(de)(de)(de)(de)(de)影響也很大。電(dian)(dian)(dian)容(rong)(rong)(rong)的(de)(de)(de)(de)(de)(de)(de)(de)使(shi)(shi)用(yong)壽(shou)(shou)命(ming)(ming)(ming)隨溫(wen)度(du)(du)(du)的(de)(de)(de)(de)(de)(de)(de)(de)增加而減小(xiao)，實驗證明環境溫(wen)度(du)(du)(du)每(mei)升高(gao)(gao)10℃，電(dian)(dian)(dian)容(rong)(rong)(rong)的(de)(de)(de)(de)(de)(de)(de)(de)壽(shou)(shou)命(ming)(ming)(ming)就(jiu)會減半(ban)。主要原(yuan)(yuan)(yuan)因(yin)就(jiu)是溫(wen)度(du)(du)(du)加速化(hua)(hua)學反應而使(shi)(shi)介質隨時間退化(hua)(hua)失效，這樣電(dian)(dian)(dian)容(rong)(rong)(rong)壽(shou)(shou)命(ming)(ming)(ming)終結。為了(le)(le)保證電(dian)(dian)(dian)容(rong)(rong)(rong)的(de)(de)(de)(de)(de)(de)(de)(de)穩定性(xing)，電(dian)(dian)(dian)容(rong)(rong)(rong)在(zai)插板前要經過(guo)長時間的(de)(de)(de)(de)(de)(de)(de)(de)高(gao)(gao)溫(wen)環境的(de)(de)(de)(de)(de)(de)(de)(de)測(ce)試。即使(shi)(shi)是在(zai)100℃，高(gao)(gao)品(pin)質的(de)(de)(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)容(rong)(rong)(rong)也可以工作幾千個小(xiao)時。同時，我(wo)們提到的(de)(de)(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)容(rong)(rong)(rong)的(de)(de)(de)(de)(de)(de)(de)(de)壽(shou)(shou)命(ming)(ming)(ming)是指電(dian)(dian)(dian)容(rong)(rong)(rong)在(zai)使(shi)(shi)用(yong)過(guo)程中(zhong)，電(dian)(dian)(dian)容(rong)(rong)(rong)容(rong)(rong)(rong)量(liang)不會超(chao)過(guo)標準(zhun)范(fan)圍(wei)變化(hua)(hua)的(de)(de)(de)(de)(de)(de)(de)(de)10%。電(dian)(dian)(dian)容(rong)(rong)(rong)壽(shou)(shou)命(ming)(ming)(ming)指的(de)(de)(de)(de)(de)(de)(de)(de)是電(dian)(dian)(dian)容(rong)(rong)(rong)容(rong)(rong)(rong)量(liang)的(de)(de)(de)(de)(de)(de)(de)(de)問題，而不是設(she)計壽(shou)(shou)命(ming)(ming)(ming)到達(da)之后就(jiu)發(fa)生(sheng)爆漿。只是無法保證電(dian)(dian)(dian)容(rong)(rong)(rong)的(de)(de)(de)(de)(de)(de)(de)(de)設(she)計的(de)(de)(de)(de)(de)(de)(de)(de)容(rong)(rong)(rong)量(liang)標準(zhun)。
所以，短時期內，正(zheng)(zheng)常使(shi)用(yong)(yong)的(de)板(ban)卡電(dian)(dian)(dian)容就(jiu)發(fa)生(sheng)爆(bao)漿的(de)情況(kuang)，這就(jiu)是電(dian)(dian)(dian)容品質問(wen)題(ti)。另外，不正(zheng)(zheng)常的(de)使(shi)用(yong)(yong)情況(kuang)也有可能發(fa)生(sheng)電(dian)(dian)(dian)容爆(bao)漿的(de)情況(kuang)。比如熱插拔電(dian)(dian)(dian)腦(nao)配(pei)件也會導致板(ban)卡局部電(dian)(dian)(dian)路電(dian)(dian)(dian)流、電(dian)(dian)(dian)壓的(de)劇烈變化，從而引(yin)發(fa)電(dian)(dian)(dian)容使(shi)用(yong)(yong)故(gu)障。
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