詳解電容在電源中所起到的作用
2019/7/1 12:46:11??????點擊：
作為無源元件(jian)之一的電容，其作用(yong)不(bu)外乎(hu)以下幾(ji)種：
1、應用于電源電路，實現旁路、去藕、濾波和(he)儲能方(fang)面電容(rong)的作(zuo)用，下面分類(lei)詳述之：
1)濾波
濾波是電(dian)(dian)(dian)(dian)容(rong)(rong)的(de)作用中(zhong)很重要的(de)一部分。幾乎所有的(de)電(dian)(dian)(dian)(dian)源電(dian)(dian)(dian)(dian)路中(zhong)都(dou)會(hui)用到。從理論上(即假設(she)電(dian)(dian)(dian)(dian)容(rong)(rong)為純電(dian)(dian)(dian)(dian)容(rong)(rong))說，電(dian)(dian)(dian)(dian)容(rong)(rong)越(yue)大(da)(da)(da)(da)(da)，阻(zu)抗越(yue)小(xiao)(xiao)，通(tong)過的(de)頻(pin)(pin)率(lv)(lv)也越(yue)高(gao)。但實際上超過1uF的(de)電(dian)(dian)(dian)(dian)容(rong)(rong)大(da)(da)(da)(da)(da)多為電(dian)(dian)(dian)(dian)解(jie)電(dian)(dian)(dian)(dian)容(rong)(rong)，有很大(da)(da)(da)(da)(da)的(de)電(dian)(dian)(dian)(dian)感成(cheng)份，所以頻(pin)(pin)率(lv)(lv)高(gao)后(hou)反而阻(zu)抗會(hui)增大(da)(da)(da)(da)(da)。有時會(hui)看到有一個電(dian)(dian)(dian)(dian)容(rong)(rong)量較(jiao)大(da)(da)(da)(da)(da)電(dian)(dian)(dian)(dian)解(jie)電(dian)(dian)(dian)(dian)容(rong)(rong)并聯了一個小(xiao)(xiao)電(dian)(dian)(dian)(dian)容(rong)(rong)，這(zhe)時大(da)(da)(da)(da)(da)電(dian)(dian)(dian)(dian)容(rong)(rong)通(tong)低(di)頻(pin)(pin)，小(xiao)(xiao)電(dian)(dian)(dian)(dian)容(rong)(rong)通(tong)高(gao)頻(pin)(pin)。電(dian)(dian)(dian)(dian)容(rong)(rong)的(de)作用就是通(tong)高(gao)阻(zu)低(di)，通(tong)高(gao)頻(pin)(pin)阻(zu)低(di)頻(pin)(pin)。電(dian)(dian)(dian)(dian)容(rong)(rong)越(yue)大(da)(da)(da)(da)(da)低(di)頻(pin)(pin)越(yue)容(rong)(rong)易通(tong)過，電(dian)(dian)(dian)(dian)容(rong)(rong)越(yue)大(da)(da)(da)(da)(da)高(gao)頻(pin)(pin)越(yue)容(rong)(rong)易通(tong)過。具體用在濾波中(zhong),大(da)(da)(da)(da)(da)電(dian)(dian)(dian)(dian)容(rong)(rong)(1000uF)濾低(di)頻(pin)(pin)，小(xiao)(xiao)電(dian)(dian)(dian)(dian)容(rong)(rong)(20pF)濾高(gao)頻(pin)(pin)。
曾(ceng)有網友(you)將濾波電(dian)(dian)容(rong) 比作“水塘”。由于電(dian)(dian)容(rong)的(de)兩端(duan)電(dian)(dian)壓(ya)不(bu)會(hui)(hui)突變(bian)(bian)，由此可(ke)知，信號(hao)頻率越高則(ze)衰減越大(da)，可(ke)很形(xing)象的(de)說電(dian)(dian)容(rong)像個水塘，不(bu)會(hui)(hui)因幾滴水的(de)加入(ru)或(huo)蒸發而引起水量(liang)的(de)變(bian)(bian)化(hua)。 它把電(dian)(dian)壓(ya)的(de)變(bian)(bian)動轉化(hua)為電(dian)(dian)流的(de)變(bian)(bian)化(hua)，頻率越高，峰值電(dian)(dian)流就越大(da)，從而緩沖了電(dian)(dian)壓(ya)。濾波就是充電(dian)(dian)，放電(dian)(dian)的(de)過程。
2)旁(pang)路
旁路電(dian)容是(shi)(shi)為本(ben)地(di)器(qi)件提供(gong)能(neng)量的(de)儲能(neng)器(qi)件，它能(neng)使穩壓(ya)器(qi)的(de)輸出均(jun)勻化(hua)，降(jiang)低負載(zai)需求。就像(xiang)小型可(ke)充(chong)(chong)電(dian)電(dian)池一樣，旁路電(dian)容能(neng)夠被充(chong)(chong)電(dian)，并向器(qi)件進行放 電(dian)。為盡量減少阻抗(kang)，旁路電(dian)容要盡量靠近負載(zai)器(qi)件的(de)供(gong)電(dian)電(dian)源管(guan)腳(jiao)(jiao)和地(di)管(guan)腳(jiao)(jiao)。這能(neng)夠很(hen)好地(di)防止輸入值過大(da)而導致(zhi)的(de)地(di)電(dian)位(wei)抬高和噪聲。地(di)彈是(shi)(shi)地(di)連接處在(zai)通過大(da) 電(dian)流毛(mao)刺時的(de)電(dian)壓(ya)降(jiang)。
3)去藕
去(qu)(qu)(qu)藕(ou)，又稱解藕(ou)。從(cong)電(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)來(lai)說，總是(shi)(shi)(shi)(shi)(shi)可以區分為(wei)驅(qu)動(dong)的(de)(de)源和(he)被驅(qu)動(dong)的(de)(de)負載(zai)。如果負載(zai)電(dian)(dian)(dian)(dian)(dian)(dian)容比(bi)較大(da)，驅(qu)動(dong)電(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)要把電(dian)(dian)(dian)(dian)(dian)(dian)容充電(dian)(dian)(dian)(dian)(dian)(dian)、放電(dian)(dian)(dian)(dian)(dian)(dian)，才(cai)能完(wan)成信(xin)號(hao)的(de)(de)跳(tiao)變，在上(shang) 升沿比(bi)較陡峭的(de)(de)時候，電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)比(bi)較大(da)，這樣驅(qu)動(dong)的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)就(jiu)(jiu)會吸收很大(da)的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)源電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)，由于電(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)中(zhong)的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)感(gan)(gan)，電(dian)(dian)(dian)(dian)(dian)(dian)阻(特別是(shi)(shi)(shi)(shi)(shi)芯片管腳上(shang)的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)感(gan)(gan)，會產(chan)生反彈)，這種(zhong)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)相對(dui) 于正(zheng)(zheng)常情況來(lai)說實際上(shang)就(jiu)(jiu)是(shi)(shi)(shi)(shi)(shi)一(yi)(yi)種(zhong)噪(zao)聲，會影響(xiang)前(qian)級的(de)(de)正(zheng)(zheng)常工作。這就(jiu)(jiu)是(shi)(shi)(shi)(shi)(shi)耦合(he)。去(qu)(qu)(qu)藕(ou)電(dian)(dian)(dian)(dian)(dian)(dian)容就(jiu)(jiu)是(shi)(shi)(shi)(shi)(shi)起到一(yi)(yi)個電(dian)(dian)(dian)(dian)(dian)(dian)池的(de)(de)作用(yong)，滿(man)足驅(qu)動(dong)電(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)的(de)(de)變化(hua)，避免相互(hu)間的(de)(de)耦合(he)干擾。將(jiang)旁(pang)(pang)(pang)路(lu)(lu)電(dian)(dian)(dian)(dian)(dian)(dian)容和(he)去(qu)(qu)(qu)藕(ou)電(dian)(dian)(dian)(dian)(dian)(dian)容結合(he)起來(lai)將(jiang)更容易理解。旁(pang)(pang)(pang)路(lu)(lu)電(dian)(dian)(dian)(dian)(dian)(dian)容實際也是(shi)(shi)(shi)(shi)(shi)去(qu)(qu)(qu)藕(ou)合(he)的(de)(de)，只是(shi)(shi)(shi)(shi)(shi)旁(pang)(pang)(pang)路(lu)(lu)電(dian)(dian)(dian)(dian)(dian)(dian)容一(yi)(yi)般(ban)是(shi)(shi)(shi)(shi)(shi)指(zhi)高(gao)(gao)頻旁(pang)(pang)(pang)路(lu)(lu)，也就(jiu)(jiu)是(shi)(shi)(shi)(shi)(shi)給高(gao)(gao)頻的(de)(de)開關噪(zao)聲提高(gao)(gao)一(yi)(yi)條(tiao)低阻抗(kang)泄防 途徑。高(gao)(gao)頻旁(pang)(pang)(pang)路(lu)(lu)電(dian)(dian)(dian)(dian)(dian)(dian)容一(yi)(yi)般(ban)比(bi)較小(xiao)，根據諧振(zhen)頻率(lv)一(yi)(yi)般(ban)是(shi)(shi)(shi)(shi)(shi)0.1u，0.01u等，而去(qu)(qu)(qu)耦合(he)電(dian)(dian)(dian)(dian)(dian)(dian)容一(yi)(yi)般(ban)比(bi)較大(da)，是(shi)(shi)(shi)(shi)(shi)10uF或(huo)者(zhe)更大(da)，依據電(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)中(zhong)分布參數，以及驅(qu)動(dong) 電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)的(de)(de)變化(hua)大(da)小(xiao)來(lai)確定。旁(pang)(pang)(pang)路(lu)(lu)是(shi)(shi)(shi)(shi)(shi)把輸入信(xin)號(hao)中(zhong)的(de)(de)干擾作為(wei)濾除對(dui)象，而去(qu)(qu)(qu)耦是(shi)(shi)(shi)(shi)(shi)把輸出(chu)信(xin)號(hao)的(de)(de)干擾作為(wei)濾除對(dui)象，防止干擾信(xin)號(hao)返回電(dian)(dian)(dian)(dian)(dian)(dian)源。這應該是(shi)(shi)(shi)(shi)(shi)他們的(de)(de)本(ben)質區別。
4)儲能
儲能型(xing)電(dian)(dian)(dian)容(rong)器(qi)通(tong)過整流器(qi)收集電(dian)(dian)(dian)荷，并將存儲的(de)能量通(tong)過變換器(qi)引線傳送(song)至電(dian)(dian)(dian)源的(de)輸出端。電(dian)(dian)(dian)壓額定(ding)值為40～450VDC、電(dian)(dian)(dian)容(rong)值在220～150 000uF之間(jian)的(de)鋁電(dian)(dian)(dian)解電(dian)(dian)(dian)容(rong)器(qi)(如EPCOS公司的(de) B43504或(huo)B43505)是(shi)較(jiao)為常用的(de)。根據不同的(de)電(dian)(dian)(dian)源要求，器(qi)件有時會(hui)采用串聯、并聯或(huo)其組合的(de)形式， 對于(yu)功率(lv)級(ji)超過10KW的(de)電(dian)(dian)(dian)源，通(tong)常采用體(ti)積較(jiao)大(da)的(de)罐形螺旋端子電(dian)(dian)(dian)容(rong)器(qi)。
2、應(ying)用(yong)于信號電路，主要完成耦合、振(zhen)蕩/同步及時間常數的作用(yong)：
1)耦(ou)合
舉個(ge)(ge)例子來(lai)講，晶(jing)體(ti)管放大器(qi)發射極有一個(ge)(ge)自(zi)給偏壓電(dian)(dian)(dian)阻(zu)(zu)，它同時(shi)又使信(xin)號產(chan)生壓降反饋到輸入端形成了輸入輸出信(xin)號耦(ou)合，這個(ge)(ge)電(dian)(dian)(dian)阻(zu)(zu)就是產(chan)生了耦(ou)合的元件，如果(guo)在這個(ge)(ge)電(dian)(dian)(dian)阻(zu)(zu)兩端并聯(lian)一個(ge)(ge)電(dian)(dian)(dian)容，由于適當容量的電(dian)(dian)(dian)容器(qi)對(dui)交流信(xin)號較(jiao)小的阻(zu)(zu)抗,這樣就減小了電(dian)(dian)(dian)阻(zu)(zu)產(chan)生的耦(ou)合效應(ying)，故稱此電(dian)(dian)(dian)容為(wei)去耦(ou)電(dian)(dian)(dian)容。
2)振蕩/同(tong)步
包括(kuo)RC、LC振蕩器(qi)及晶體(ti)的(de)負載電容都屬(shu)于這(zhe)一范疇。
3)時(shi)間常數
這就是常見的(de) R、C 串聯構(gou)成的(de)積(ji)分電路。當輸(shu)入(ru)(ru)信(xin)號電壓加在輸(shu)入(ru)(ru)端時，電容(C)上的(de)電壓逐(zhu)漸上升。而其充電電流(liu)則隨(sui)著電壓的(de)上升而減小(xiao)。電流(liu)通(tong)過(guo)電阻(R)、電容(C)的(de)特性(xing)通(tong)過(guo)下面的(de)公式(shi)描述(shu)：
i = (V/R)e-(t/CR)
我們(men)知(zhi)道了電(dian)容的作用(yong)以后下面來談談電(dian)容在使用(yong)中的注意(yi)事項
A. 什么是(shi)好電容。
1.電容容量(liang)越大越好。
很多人(ren)在(zai)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)的(de)(de)(de)(de)(de)替(ti)換(huan)中往往愛用大(da)(da)容(rong)(rong)(rong)(rong)(rong)量(liang)的(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)。我們知道雖然電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)越(yue)(yue)大(da)(da)，為IC提(ti)供的(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)補償(chang)的(de)(de)(de)(de)(de)能(neng)力(li)越(yue)(yue)強。且不說(shuo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)容(rong)(rong)(rong)(rong)(rong)量(liang)的(de)(de)(de)(de)(de)增(zeng)(zeng)大(da)(da)帶來的(de)(de)(de)(de)(de)體(ti)積變(bian)大(da)(da)，增(zeng)(zeng)加成本的(de)(de)(de)(de)(de)同時還影(ying)響空(kong)氣流(liu)動和散熱(re)。關鍵在(zai)于電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)上存在(zai)寄生電(dian)(dian)(dian)(dian)(dian)(dian)(dian)感，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)放電(dian)(dian)(dian)(dian)(dian)(dian)(dian)回路(lu)會在(zai)某個頻(pin)點(dian)(dian)上發生諧振(zhen)。在(zai)諧振(zhen)點(dian)(dian)，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)的(de)(de)(de)(de)(de)阻(zu)抗(kang)小(xiao)。因(yin)此放電(dian)(dian)(dian)(dian)(dian)(dian)(dian)回路(lu)的(de)(de)(de)(de)(de)阻(zu)抗(kang)最小(xiao)，補充(chong)能(neng)量(liang)的(de)(de)(de)(de)(de)效果也最好。但當頻(pin)率(lv)超過諧振(zhen)點(dian)(dian)時，放電(dian)(dian)(dian)(dian)(dian)(dian)(dian)回路(lu)的(de)(de)(de)(de)(de)阻(zu)抗(kang)開(kai)始增(zeng)(zeng)加，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)提(ti)供電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)能(neng)力(li)便(bian)開(kai)始下降。電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)的(de)(de)(de)(de)(de)容(rong)(rong)(rong)(rong)(rong)值越(yue)(yue)大(da)(da)，諧振(zhen)頻(pin)率(lv)越(yue)(yue)低，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)能(neng)有(you)效補償(chang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)的(de)(de)(de)(de)(de)頻(pin)率(lv)范圍也越(yue)(yue)小(xiao)。從保(bao)證(zheng)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)提(ti)供高頻(pin)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)的(de)(de)(de)(de)(de)能(neng)力(li)的(de)(de)(de)(de)(de)角度(du)來說(shuo)，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)越(yue)(yue)大(da)(da)越(yue)(yue)好的(de)(de)(de)(de)(de)觀點(dian)(dian)是(shi)錯誤的(de)(de)(de)(de)(de)，一般(ban)的(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)設(she)計中都(dou)有(you)一個參考(kao)值的(de)(de)(de)(de)(de)。
2.同樣容(rong)量的(de)電容(rong)，并聯越多的(de)小電容(rong)越好
耐(nai)壓(ya)(ya)值(zhi)、耐(nai)溫(wen)值(zhi)、容(rong)值(zhi)、ESR(等(deng)效電(dian)(dian)阻)等(deng)是(shi)電(dian)(dian)容(rong)的(de)幾個重要(yao)參數，對于ESR自然是(shi)越(yue)(yue)低(di)越(yue)(yue)好。ESR與電(dian)(dian)容(rong)的(de)容(rong)量、頻率、電(dian)(dian)壓(ya)(ya)、溫(wen)度(du)等(deng)都有(you)關系。當電(dian)(dian)壓(ya)(ya)固定(ding)時候，容(rong)量越(yue)(yue)大(da)，ESR越(yue)(yue)低(di)。在板卡(ka)設(she)計中采用多個小電(dian)(dian)容(rong)并連多是(shi)出(chu)與PCB空(kong)間的(de)限(xian)制(zhi)，這樣有(you)的(de)人就認為，越(yue)(yue)多的(de)并聯(lian)小電(dian)(dian)阻，ESR越(yue)(yue)低(di)，效果越(yue)(yue)好。理(li)論上是(shi)如此，但是(shi)要(yao)考慮到電(dian)(dian)容(rong)接腳焊點的(de)阻抗(kang)，采用多個小電(dian)(dian)容(rong)并聯(lian)，效果并不一定(ding)突出(chu)。
3.ESR越低，效果越好。
結合我們上面的(de)(de)(de)(de)提(ti)高(gao)的(de)(de)(de)(de)供電(dian)(dian)電(dian)(dian)路(lu)(lu)來(lai)說(shuo)，對(dui)于(yu)輸(shu)入(ru)電(dian)(dian)容(rong)(rong)來(lai)說(shuo)，輸(shu)入(ru)電(dian)(dian)容(rong)(rong)的(de)(de)(de)(de)容(rong)(rong)量要(yao)大一點。相對(dui)容(rong)(rong)量的(de)(de)(de)(de)要(yao)求(qiu)(qiu)(qiu)，對(dui)ESR的(de)(de)(de)(de)要(yao)求(qiu)(qiu)(qiu)可以(yi)適(shi)當的(de)(de)(de)(de)降(jiang)低(di)(di)。因為輸(shu)入(ru)電(dian)(dian)容(rong)(rong)主要(yao)是(shi)耐壓，其次是(shi)吸收MOSFET的(de)(de)(de)(de)開關脈沖。對(dui)于(yu)輸(shu)出電(dian)(dian)容(rong)(rong)來(lai)說(shuo)，耐壓的(de)(de)(de)(de)要(yao)求(qiu)(qiu)(qiu)和容(rong)(rong)量可以(yi)適(shi)當的(de)(de)(de)(de)降(jiang)低(di)(di)一點。ESR的(de)(de)(de)(de)要(yao)求(qiu)(qiu)(qiu)則高(gao)一點，因為這里(li)要(yao)保證的(de)(de)(de)(de)是(shi)足夠的(de)(de)(de)(de)電(dian)(dian)流(liu)通過量。但這里(li)要(yao)注意的(de)(de)(de)(de)是(shi)ESR并不是(shi)越低(di)(di)越好，低(di)(di)ESR電(dian)(dian)容(rong)(rong)會(hui)引起開關電(dian)(dian)路(lu)(lu)振(zhen)蕩。而消(xiao)振(zhen)電(dian)(dian)路(lu)(lu)復雜同時會(hui)導致(zhi)成本(ben)的(de)(de)(de)(de)增加。板卡設計中，這里(li)一般有一個(ge)參考值(zhi)，此作為元件(jian)選(xuan)用參數，避免消(xiao)振(zhen)電(dian)(dian)路(lu)(lu)而導致(zhi)成本(ben)的(de)(de)(de)(de)增加。
4.好電容代表著(zhu)高(gao)品(pin)質。
“唯電(dian)容(rong)論”曾經盛極一(yi)時，一(yi)些廠商和媒體也刻意的把這(zhe)個事(shi)情做(zuo)(zuo)成一(yi)個賣點。在板卡(ka)設計(ji)中，電(dian)路設計(ji)水平是(shi)關(guan)鍵。和有(you)的廠商可以用兩相(xiang)供電(dian)做(zuo)(zuo)出比(bi)一(yi)些廠商采用四相(xiang)供電(dian)更穩定(ding)的產(chan)(chan)品一(yi)樣(yang)，一(yi)味的采用高價(jia)電(dian)容(rong)，不一(yi)定(ding)能做(zuo)(zuo)出好產(chan)(chan)品。衡量一(yi)個產(chan)(chan)品，一(yi)定(ding)要(yao)全方位多角度的去考慮，切(qie)不可把電(dian)容(rong)的作用有(you)意無意的夸大。
B. 電容(rong)爆(bao)漿之(zhi)面面談
爆漿的(de)種類：
分兩類，輸入電容(rong)(rong)爆漿和輸出(chu)電容(rong)(rong)爆漿。
對于輸(shu)入電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)來(lai)說(shuo)，就(jiu)是(shi)我是(shi)說(shuo)的(de)(de)C1，C1對由電(dian)(dian)(dian)(dian)(dian)(dian)源接(jie)收到(dao)的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)進行(xing)過(guo)(guo)濾。輸(shu)入電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)爆漿和電(dian)(dian)(dian)(dian)(dian)(dian)源輸(shu)入電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)的(de)(de)品質有關。過(guo)(guo)多的(de)(de)毛(mao)刺電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)，峰值電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)過(guo)(guo)高，電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)不穩定等都使電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)過(guo)(guo)于充(chong)放電(dian)(dian)(dian)(dian)(dian)(dian)過(guo)(guo)于頻繁，長時間處(chu)于這類工作環境下的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)，內部(bu)溫(wen)度升高很快。超過(guo)(guo)泄爆口的(de)(de)承(cheng)受極限(xian)就(jiu)會發生爆漿。
對(dui)于輸出電(dian)容來說(shuo)(shuo)，就我(wo)說(shuo)(shuo)的(de)C2，對(dui)經電(dian)源(yuan)模(mo)塊調整(zheng)后的(de)電(dian)流(liu)進行濾波。此(ci)處電(dian)流(liu)經過(guo)一次過(guo)濾，比較平穩，發(fa)(fa)生(sheng)爆漿(jiang)的(de)可能性相對(dui)來說(shuo)(shuo)小了(le)不少。但如果環境(jing)溫度過(guo)高，電(dian)容同樣容易(yi)發(fa)(fa)生(sheng)爆漿(jiang)。爆，報也。采(cai)用垃圾東西自然(ran)要爆，報應啊。欲(yu)知過(guo)去因者(zhe)(zhe)，見(jian)其現在(zai)果;欲(yu)知未(wei)來果者(zhe)(zhe)，見(jian)其現在(zai)因。
電(dian)解電(dian)容(rong)爆(bao)漿的(de)原(yuan)因：
電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)爆(bao)(bao)漿(jiang)的(de)(de)(de)(de)原因有很多，比如電(dian)(dian)(dian)(dian)(dian)流大(da)于允許的(de)(de)(de)(de)穩波電(dian)(dian)(dian)(dian)(dian)流、使(shi)(shi)(shi)(shi)用(yong)(yong)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)超出工(gong)作電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)、逆向電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)、頻繁的(de)(de)(de)(de)充放(fang)電(dian)(dian)(dian)(dian)(dian)等。但是(shi)最直(zhi)接的(de)(de)(de)(de)原因就(jiu)是(shi)高溫(wen)(wen)。我們(men)(men)知(zhi)道電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)有一個重要的(de)(de)(de)(de)參(can)數就(jiu)是(shi)耐(nai)溫(wen)(wen)值，指(zhi)的(de)(de)(de)(de)就(jiu)是(shi)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)內(nei)部(bu)(bu)電(dian)(dian)(dian)(dian)(dian)解液的(de)(de)(de)(de)沸(fei)點。當(dang)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)的(de)(de)(de)(de)內(nei)部(bu)(bu)溫(wen)(wen)度(du)達到電(dian)(dian)(dian)(dian)(dian)解液的(de)(de)(de)(de)沸(fei)點時(shi)，電(dian)(dian)(dian)(dian)(dian)解液開始沸(fei)騰，電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)內(nei)部(bu)(bu)的(de)(de)(de)(de)壓(ya)(ya)力升高，當(dang)壓(ya)(ya)力超過(guo)泄(xie)爆(bao)(bao)口的(de)(de)(de)(de)承受極限(xian)就(jiu)發(fa)生(sheng)(sheng)了(le)爆(bao)(bao)漿(jiang)。所以說溫(wen)(wen)度(du)是(shi)導致電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)爆(bao)(bao)漿(jiang)的(de)(de)(de)(de)直(zhi)接原因。電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)設計(ji)(ji)使(shi)(shi)(shi)(shi)用(yong)(yong)壽(shou)(shou)命(ming)(ming)大(da)約為2萬(wan)小時(shi)，受環(huan)境(jing)(jing)溫(wen)(wen)度(du)的(de)(de)(de)(de)影(ying)響也很大(da)。電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)的(de)(de)(de)(de)使(shi)(shi)(shi)(shi)用(yong)(yong)壽(shou)(shou)命(ming)(ming)隨溫(wen)(wen)度(du)的(de)(de)(de)(de)增加(jia)而(er)減小，實(shi)驗證(zheng)明環(huan)境(jing)(jing)溫(wen)(wen)度(du)每升高10℃，電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)的(de)(de)(de)(de)壽(shou)(shou)命(ming)(ming)就(jiu)會(hui)減半。主要原因就(jiu)是(shi)溫(wen)(wen)度(du)加(jia)速化學反應而(er)使(shi)(shi)(shi)(shi)介質隨時(shi)間退化失效，這樣電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)壽(shou)(shou)命(ming)(ming)終結。為了(le)保(bao)(bao)證(zheng)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)的(de)(de)(de)(de)穩定性，電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)在插板(ban)前要經過(guo)長時(shi)間的(de)(de)(de)(de)高溫(wen)(wen)環(huan)境(jing)(jing)的(de)(de)(de)(de)測(ce)試。即使(shi)(shi)(shi)(shi)是(shi)在100℃，高品質的(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)也可(ke)以工(gong)作幾千個小時(shi)。同時(shi)，我們(men)(men)提到的(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)的(de)(de)(de)(de)壽(shou)(shou)命(ming)(ming)是(shi)指(zhi)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)在使(shi)(shi)(shi)(shi)用(yong)(yong)過(guo)程中，電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)容(rong)(rong)(rong)量不會(hui)超過(guo)標(biao)準范(fan)圍變(bian)化的(de)(de)(de)(de)10%。電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)壽(shou)(shou)命(ming)(ming)指(zhi)的(de)(de)(de)(de)是(shi)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)容(rong)(rong)(rong)量的(de)(de)(de)(de)問題，而(er)不是(shi)設計(ji)(ji)壽(shou)(shou)命(ming)(ming)到達之后就(jiu)發(fa)生(sheng)(sheng)爆(bao)(bao)漿(jiang)。只是(shi)無法保(bao)(bao)證(zheng)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)的(de)(de)(de)(de)設計(ji)(ji)的(de)(de)(de)(de)容(rong)(rong)(rong)量標(biao)準。
所以(yi)，短時期內，正(zheng)常使(shi)用(yong)的(de)(de)板卡電(dian)容(rong)就發(fa)生爆(bao)漿的(de)(de)情(qing)況，這就是電(dian)容(rong)品質(zhi)問題。另(ling)外(wai)，不正(zheng)常的(de)(de)使(shi)用(yong)情(qing)況也(ye)有可(ke)能(neng)發(fa)生電(dian)容(rong)爆(bao)漿的(de)(de)情(qing)況。比如熱(re)插拔電(dian)腦配件(jian)也(ye)會(hui)導致板卡局部電(dian)路(lu)電(dian)流、電(dian)壓的(de)(de)劇烈變(bian)化，從而(er)引(yin)發(fa)電(dian)容(rong)使(shi)用(yong)故(gu)障(zhang)。
1、應用于電源電路，實現旁路、去藕、濾波和(he)儲能方(fang)面電容(rong)的作(zuo)用，下面分類(lei)詳述之：
1)濾波
濾波是電(dian)(dian)(dian)(dian)容(rong)(rong)的(de)作用中(zhong)很重要的(de)一部分。幾乎所有的(de)電(dian)(dian)(dian)(dian)源電(dian)(dian)(dian)(dian)路中(zhong)都(dou)會(hui)用到。從理論上(即假設(she)電(dian)(dian)(dian)(dian)容(rong)(rong)為純電(dian)(dian)(dian)(dian)容(rong)(rong))說，電(dian)(dian)(dian)(dian)容(rong)(rong)越(yue)大(da)(da)(da)(da)(da)，阻(zu)抗越(yue)小(xiao)(xiao)，通(tong)過的(de)頻(pin)(pin)率(lv)(lv)也越(yue)高(gao)。但實際上超過1uF的(de)電(dian)(dian)(dian)(dian)容(rong)(rong)大(da)(da)(da)(da)(da)多為電(dian)(dian)(dian)(dian)解(jie)電(dian)(dian)(dian)(dian)容(rong)(rong)，有很大(da)(da)(da)(da)(da)的(de)電(dian)(dian)(dian)(dian)感成(cheng)份，所以頻(pin)(pin)率(lv)(lv)高(gao)后(hou)反而阻(zu)抗會(hui)增大(da)(da)(da)(da)(da)。有時會(hui)看到有一個電(dian)(dian)(dian)(dian)容(rong)(rong)量較(jiao)大(da)(da)(da)(da)(da)電(dian)(dian)(dian)(dian)解(jie)電(dian)(dian)(dian)(dian)容(rong)(rong)并聯了一個小(xiao)(xiao)電(dian)(dian)(dian)(dian)容(rong)(rong)，這(zhe)時大(da)(da)(da)(da)(da)電(dian)(dian)(dian)(dian)容(rong)(rong)通(tong)低(di)頻(pin)(pin)，小(xiao)(xiao)電(dian)(dian)(dian)(dian)容(rong)(rong)通(tong)高(gao)頻(pin)(pin)。電(dian)(dian)(dian)(dian)容(rong)(rong)的(de)作用就是通(tong)高(gao)阻(zu)低(di)，通(tong)高(gao)頻(pin)(pin)阻(zu)低(di)頻(pin)(pin)。電(dian)(dian)(dian)(dian)容(rong)(rong)越(yue)大(da)(da)(da)(da)(da)低(di)頻(pin)(pin)越(yue)容(rong)(rong)易通(tong)過，電(dian)(dian)(dian)(dian)容(rong)(rong)越(yue)大(da)(da)(da)(da)(da)高(gao)頻(pin)(pin)越(yue)容(rong)(rong)易通(tong)過。具體用在濾波中(zhong),大(da)(da)(da)(da)(da)電(dian)(dian)(dian)(dian)容(rong)(rong)(1000uF)濾低(di)頻(pin)(pin)，小(xiao)(xiao)電(dian)(dian)(dian)(dian)容(rong)(rong)(20pF)濾高(gao)頻(pin)(pin)。
曾(ceng)有網友(you)將濾波電(dian)(dian)容(rong) 比作“水塘”。由于電(dian)(dian)容(rong)的(de)兩端(duan)電(dian)(dian)壓(ya)不(bu)會(hui)(hui)突變(bian)(bian)，由此可(ke)知，信號(hao)頻率越高則(ze)衰減越大(da)，可(ke)很形(xing)象的(de)說電(dian)(dian)容(rong)像個水塘，不(bu)會(hui)(hui)因幾滴水的(de)加入(ru)或(huo)蒸發而引起水量(liang)的(de)變(bian)(bian)化(hua)。 它把電(dian)(dian)壓(ya)的(de)變(bian)(bian)動轉化(hua)為電(dian)(dian)流的(de)變(bian)(bian)化(hua)，頻率越高，峰值電(dian)(dian)流就越大(da)，從而緩沖了電(dian)(dian)壓(ya)。濾波就是充電(dian)(dian)，放電(dian)(dian)的(de)過程。
2)旁(pang)路
旁路電(dian)容是(shi)(shi)為本(ben)地(di)器(qi)件提供(gong)能(neng)量的(de)儲能(neng)器(qi)件，它能(neng)使穩壓(ya)器(qi)的(de)輸出均(jun)勻化(hua)，降(jiang)低負載(zai)需求。就像(xiang)小型可(ke)充(chong)(chong)電(dian)電(dian)池一樣，旁路電(dian)容能(neng)夠被充(chong)(chong)電(dian)，并向器(qi)件進行放 電(dian)。為盡量減少阻抗(kang)，旁路電(dian)容要盡量靠近負載(zai)器(qi)件的(de)供(gong)電(dian)電(dian)源管(guan)腳(jiao)(jiao)和地(di)管(guan)腳(jiao)(jiao)。這能(neng)夠很(hen)好地(di)防止輸入值過大(da)而導致(zhi)的(de)地(di)電(dian)位(wei)抬高和噪聲。地(di)彈是(shi)(shi)地(di)連接處在(zai)通過大(da) 電(dian)流毛(mao)刺時的(de)電(dian)壓(ya)降(jiang)。
3)去藕
去(qu)(qu)(qu)藕(ou)，又稱解藕(ou)。從(cong)電(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)來(lai)說，總是(shi)(shi)(shi)(shi)(shi)可以區分為(wei)驅(qu)動(dong)的(de)(de)源和(he)被驅(qu)動(dong)的(de)(de)負載(zai)。如果負載(zai)電(dian)(dian)(dian)(dian)(dian)(dian)容比(bi)較大(da)，驅(qu)動(dong)電(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)要把電(dian)(dian)(dian)(dian)(dian)(dian)容充電(dian)(dian)(dian)(dian)(dian)(dian)、放電(dian)(dian)(dian)(dian)(dian)(dian)，才(cai)能完(wan)成信(xin)號(hao)的(de)(de)跳(tiao)變，在上(shang) 升沿比(bi)較陡峭的(de)(de)時候，電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)比(bi)較大(da)，這樣驅(qu)動(dong)的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)就(jiu)(jiu)會吸收很大(da)的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)源電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)，由于電(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)中(zhong)的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)感(gan)(gan)，電(dian)(dian)(dian)(dian)(dian)(dian)阻(特別是(shi)(shi)(shi)(shi)(shi)芯片管腳上(shang)的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)感(gan)(gan)，會產(chan)生反彈)，這種(zhong)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)相對(dui) 于正(zheng)(zheng)常情況來(lai)說實際上(shang)就(jiu)(jiu)是(shi)(shi)(shi)(shi)(shi)一(yi)(yi)種(zhong)噪(zao)聲，會影響(xiang)前(qian)級的(de)(de)正(zheng)(zheng)常工作。這就(jiu)(jiu)是(shi)(shi)(shi)(shi)(shi)耦合(he)。去(qu)(qu)(qu)藕(ou)電(dian)(dian)(dian)(dian)(dian)(dian)容就(jiu)(jiu)是(shi)(shi)(shi)(shi)(shi)起到一(yi)(yi)個電(dian)(dian)(dian)(dian)(dian)(dian)池的(de)(de)作用(yong)，滿(man)足驅(qu)動(dong)電(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)的(de)(de)變化(hua)，避免相互(hu)間的(de)(de)耦合(he)干擾。將(jiang)旁(pang)(pang)(pang)路(lu)(lu)電(dian)(dian)(dian)(dian)(dian)(dian)容和(he)去(qu)(qu)(qu)藕(ou)電(dian)(dian)(dian)(dian)(dian)(dian)容結合(he)起來(lai)將(jiang)更容易理解。旁(pang)(pang)(pang)路(lu)(lu)電(dian)(dian)(dian)(dian)(dian)(dian)容實際也是(shi)(shi)(shi)(shi)(shi)去(qu)(qu)(qu)藕(ou)合(he)的(de)(de)，只是(shi)(shi)(shi)(shi)(shi)旁(pang)(pang)(pang)路(lu)(lu)電(dian)(dian)(dian)(dian)(dian)(dian)容一(yi)(yi)般(ban)是(shi)(shi)(shi)(shi)(shi)指(zhi)高(gao)(gao)頻旁(pang)(pang)(pang)路(lu)(lu)，也就(jiu)(jiu)是(shi)(shi)(shi)(shi)(shi)給高(gao)(gao)頻的(de)(de)開關噪(zao)聲提高(gao)(gao)一(yi)(yi)條(tiao)低阻抗(kang)泄防 途徑。高(gao)(gao)頻旁(pang)(pang)(pang)路(lu)(lu)電(dian)(dian)(dian)(dian)(dian)(dian)容一(yi)(yi)般(ban)比(bi)較小(xiao)，根據諧振(zhen)頻率(lv)一(yi)(yi)般(ban)是(shi)(shi)(shi)(shi)(shi)0.1u，0.01u等，而去(qu)(qu)(qu)耦合(he)電(dian)(dian)(dian)(dian)(dian)(dian)容一(yi)(yi)般(ban)比(bi)較大(da)，是(shi)(shi)(shi)(shi)(shi)10uF或(huo)者(zhe)更大(da)，依據電(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)中(zhong)分布參數，以及驅(qu)動(dong) 電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)的(de)(de)變化(hua)大(da)小(xiao)來(lai)確定。旁(pang)(pang)(pang)路(lu)(lu)是(shi)(shi)(shi)(shi)(shi)把輸入信(xin)號(hao)中(zhong)的(de)(de)干擾作為(wei)濾除對(dui)象，而去(qu)(qu)(qu)耦是(shi)(shi)(shi)(shi)(shi)把輸出(chu)信(xin)號(hao)的(de)(de)干擾作為(wei)濾除對(dui)象，防止干擾信(xin)號(hao)返回電(dian)(dian)(dian)(dian)(dian)(dian)源。這應該是(shi)(shi)(shi)(shi)(shi)他們的(de)(de)本(ben)質區別。
4)儲能
儲能型(xing)電(dian)(dian)(dian)容(rong)器(qi)通(tong)過整流器(qi)收集電(dian)(dian)(dian)荷，并將存儲的(de)能量通(tong)過變換器(qi)引線傳送(song)至電(dian)(dian)(dian)源的(de)輸出端。電(dian)(dian)(dian)壓額定(ding)值為40～450VDC、電(dian)(dian)(dian)容(rong)值在220～150 000uF之間(jian)的(de)鋁電(dian)(dian)(dian)解電(dian)(dian)(dian)容(rong)器(qi)(如EPCOS公司的(de) B43504或(huo)B43505)是(shi)較(jiao)為常用的(de)。根據不同的(de)電(dian)(dian)(dian)源要求，器(qi)件有時會(hui)采用串聯、并聯或(huo)其組合的(de)形式， 對于(yu)功率(lv)級(ji)超過10KW的(de)電(dian)(dian)(dian)源，通(tong)常采用體(ti)積較(jiao)大(da)的(de)罐形螺旋端子電(dian)(dian)(dian)容(rong)器(qi)。
2、應(ying)用(yong)于信號電路，主要完成耦合、振(zhen)蕩/同步及時間常數的作用(yong)：
1)耦(ou)合
舉個(ge)(ge)例子來(lai)講，晶(jing)體(ti)管放大器(qi)發射極有一個(ge)(ge)自(zi)給偏壓電(dian)(dian)(dian)阻(zu)(zu)，它同時(shi)又使信(xin)號產(chan)生壓降反饋到輸入端形成了輸入輸出信(xin)號耦(ou)合，這個(ge)(ge)電(dian)(dian)(dian)阻(zu)(zu)就是產(chan)生了耦(ou)合的元件，如果(guo)在這個(ge)(ge)電(dian)(dian)(dian)阻(zu)(zu)兩端并聯(lian)一個(ge)(ge)電(dian)(dian)(dian)容，由于適當容量的電(dian)(dian)(dian)容器(qi)對(dui)交流信(xin)號較(jiao)小的阻(zu)(zu)抗,這樣就減小了電(dian)(dian)(dian)阻(zu)(zu)產(chan)生的耦(ou)合效應(ying)，故稱此電(dian)(dian)(dian)容為(wei)去耦(ou)電(dian)(dian)(dian)容。
2)振蕩/同(tong)步
包括(kuo)RC、LC振蕩器(qi)及晶體(ti)的(de)負載電容都屬(shu)于這(zhe)一范疇。
3)時(shi)間常數
這就是常見的(de) R、C 串聯構(gou)成的(de)積(ji)分電路。當輸(shu)入(ru)(ru)信(xin)號電壓加在輸(shu)入(ru)(ru)端時，電容(C)上的(de)電壓逐(zhu)漸上升。而其充電電流(liu)則隨(sui)著電壓的(de)上升而減小(xiao)。電流(liu)通(tong)過(guo)電阻(R)、電容(C)的(de)特性(xing)通(tong)過(guo)下面的(de)公式(shi)描述(shu)：
i = (V/R)e-(t/CR)
我們(men)知(zhi)道了電(dian)容的作用(yong)以后下面來談談電(dian)容在使用(yong)中的注意(yi)事項
A. 什么是(shi)好電容。
1.電容容量(liang)越大越好。
很多人(ren)在(zai)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)的(de)(de)(de)(de)(de)替(ti)換(huan)中往往愛用大(da)(da)容(rong)(rong)(rong)(rong)(rong)量(liang)的(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)。我們知道雖然電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)越(yue)(yue)大(da)(da)，為IC提(ti)供的(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)補償(chang)的(de)(de)(de)(de)(de)能(neng)力(li)越(yue)(yue)強。且不說(shuo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)容(rong)(rong)(rong)(rong)(rong)量(liang)的(de)(de)(de)(de)(de)增(zeng)(zeng)大(da)(da)帶來的(de)(de)(de)(de)(de)體(ti)積變(bian)大(da)(da)，增(zeng)(zeng)加成本的(de)(de)(de)(de)(de)同時還影(ying)響空(kong)氣流(liu)動和散熱(re)。關鍵在(zai)于電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)上存在(zai)寄生電(dian)(dian)(dian)(dian)(dian)(dian)(dian)感，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)放電(dian)(dian)(dian)(dian)(dian)(dian)(dian)回路(lu)會在(zai)某個頻(pin)點(dian)(dian)上發生諧振(zhen)。在(zai)諧振(zhen)點(dian)(dian)，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)的(de)(de)(de)(de)(de)阻(zu)抗(kang)小(xiao)。因(yin)此放電(dian)(dian)(dian)(dian)(dian)(dian)(dian)回路(lu)的(de)(de)(de)(de)(de)阻(zu)抗(kang)最小(xiao)，補充(chong)能(neng)量(liang)的(de)(de)(de)(de)(de)效果也最好。但當頻(pin)率(lv)超過諧振(zhen)點(dian)(dian)時，放電(dian)(dian)(dian)(dian)(dian)(dian)(dian)回路(lu)的(de)(de)(de)(de)(de)阻(zu)抗(kang)開(kai)始增(zeng)(zeng)加，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)提(ti)供電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)能(neng)力(li)便(bian)開(kai)始下降。電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)的(de)(de)(de)(de)(de)容(rong)(rong)(rong)(rong)(rong)值越(yue)(yue)大(da)(da)，諧振(zhen)頻(pin)率(lv)越(yue)(yue)低，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)能(neng)有(you)效補償(chang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)的(de)(de)(de)(de)(de)頻(pin)率(lv)范圍也越(yue)(yue)小(xiao)。從保(bao)證(zheng)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)提(ti)供高頻(pin)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)的(de)(de)(de)(de)(de)能(neng)力(li)的(de)(de)(de)(de)(de)角度(du)來說(shuo)，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)越(yue)(yue)大(da)(da)越(yue)(yue)好的(de)(de)(de)(de)(de)觀點(dian)(dian)是(shi)錯誤的(de)(de)(de)(de)(de)，一般(ban)的(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)設(she)計中都(dou)有(you)一個參考(kao)值的(de)(de)(de)(de)(de)。
2.同樣容(rong)量的(de)電容(rong)，并聯越多的(de)小電容(rong)越好
耐(nai)壓(ya)(ya)值(zhi)、耐(nai)溫(wen)值(zhi)、容(rong)值(zhi)、ESR(等(deng)效電(dian)(dian)阻)等(deng)是(shi)電(dian)(dian)容(rong)的(de)幾個重要(yao)參數，對于ESR自然是(shi)越(yue)(yue)低(di)越(yue)(yue)好。ESR與電(dian)(dian)容(rong)的(de)容(rong)量、頻率、電(dian)(dian)壓(ya)(ya)、溫(wen)度(du)等(deng)都有(you)關系。當電(dian)(dian)壓(ya)(ya)固定(ding)時候，容(rong)量越(yue)(yue)大(da)，ESR越(yue)(yue)低(di)。在板卡(ka)設(she)計中采用多個小電(dian)(dian)容(rong)并連多是(shi)出(chu)與PCB空(kong)間的(de)限(xian)制(zhi)，這樣有(you)的(de)人就認為，越(yue)(yue)多的(de)并聯(lian)小電(dian)(dian)阻，ESR越(yue)(yue)低(di)，效果越(yue)(yue)好。理(li)論上是(shi)如此，但是(shi)要(yao)考慮到電(dian)(dian)容(rong)接腳焊點的(de)阻抗(kang)，采用多個小電(dian)(dian)容(rong)并聯(lian)，效果并不一定(ding)突出(chu)。
3.ESR越低，效果越好。
結合我們上面的(de)(de)(de)(de)提(ti)高(gao)的(de)(de)(de)(de)供電(dian)(dian)電(dian)(dian)路(lu)(lu)來(lai)說(shuo)，對(dui)于(yu)輸(shu)入(ru)電(dian)(dian)容(rong)(rong)來(lai)說(shuo)，輸(shu)入(ru)電(dian)(dian)容(rong)(rong)的(de)(de)(de)(de)容(rong)(rong)量要(yao)大一點。相對(dui)容(rong)(rong)量的(de)(de)(de)(de)要(yao)求(qiu)(qiu)(qiu)，對(dui)ESR的(de)(de)(de)(de)要(yao)求(qiu)(qiu)(qiu)可以(yi)適(shi)當的(de)(de)(de)(de)降(jiang)低(di)(di)。因為輸(shu)入(ru)電(dian)(dian)容(rong)(rong)主要(yao)是(shi)耐壓，其次是(shi)吸收MOSFET的(de)(de)(de)(de)開關脈沖。對(dui)于(yu)輸(shu)出電(dian)(dian)容(rong)(rong)來(lai)說(shuo)，耐壓的(de)(de)(de)(de)要(yao)求(qiu)(qiu)(qiu)和容(rong)(rong)量可以(yi)適(shi)當的(de)(de)(de)(de)降(jiang)低(di)(di)一點。ESR的(de)(de)(de)(de)要(yao)求(qiu)(qiu)(qiu)則高(gao)一點，因為這里(li)要(yao)保證的(de)(de)(de)(de)是(shi)足夠的(de)(de)(de)(de)電(dian)(dian)流(liu)通過量。但這里(li)要(yao)注意的(de)(de)(de)(de)是(shi)ESR并不是(shi)越低(di)(di)越好，低(di)(di)ESR電(dian)(dian)容(rong)(rong)會(hui)引起開關電(dian)(dian)路(lu)(lu)振(zhen)蕩。而消(xiao)振(zhen)電(dian)(dian)路(lu)(lu)復雜同時會(hui)導致(zhi)成本(ben)的(de)(de)(de)(de)增加。板卡設計中，這里(li)一般有一個(ge)參考值(zhi)，此作為元件(jian)選(xuan)用參數，避免消(xiao)振(zhen)電(dian)(dian)路(lu)(lu)而導致(zhi)成本(ben)的(de)(de)(de)(de)增加。
4.好電容代表著(zhu)高(gao)品(pin)質。
“唯電(dian)容(rong)論”曾經盛極一(yi)時，一(yi)些廠商和媒體也刻意的把這(zhe)個事(shi)情做(zuo)(zuo)成一(yi)個賣點。在板卡(ka)設計(ji)中，電(dian)路設計(ji)水平是(shi)關(guan)鍵。和有(you)的廠商可以用兩相(xiang)供電(dian)做(zuo)(zuo)出比(bi)一(yi)些廠商采用四相(xiang)供電(dian)更穩定(ding)的產(chan)(chan)品一(yi)樣(yang)，一(yi)味的采用高價(jia)電(dian)容(rong)，不一(yi)定(ding)能做(zuo)(zuo)出好產(chan)(chan)品。衡量一(yi)個產(chan)(chan)品，一(yi)定(ding)要(yao)全方位多角度的去考慮，切(qie)不可把電(dian)容(rong)的作用有(you)意無意的夸大。
B. 電容(rong)爆(bao)漿之(zhi)面面談
爆漿的(de)種類：
分兩類，輸入電容(rong)(rong)爆漿和輸出(chu)電容(rong)(rong)爆漿。
對于輸(shu)入電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)來(lai)說(shuo)，就(jiu)是(shi)我是(shi)說(shuo)的(de)(de)C1，C1對由電(dian)(dian)(dian)(dian)(dian)(dian)源接(jie)收到(dao)的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)進行(xing)過(guo)(guo)濾。輸(shu)入電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)爆漿和電(dian)(dian)(dian)(dian)(dian)(dian)源輸(shu)入電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)的(de)(de)品質有關。過(guo)(guo)多的(de)(de)毛(mao)刺電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)，峰值電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)過(guo)(guo)高，電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)不穩定等都使電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)過(guo)(guo)于充(chong)放電(dian)(dian)(dian)(dian)(dian)(dian)過(guo)(guo)于頻繁，長時間處(chu)于這類工作環境下的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)，內部(bu)溫(wen)度升高很快。超過(guo)(guo)泄爆口的(de)(de)承(cheng)受極限(xian)就(jiu)會發生爆漿。
對(dui)于輸出電(dian)容來說(shuo)(shuo)，就我(wo)說(shuo)(shuo)的(de)C2，對(dui)經電(dian)源(yuan)模(mo)塊調整(zheng)后的(de)電(dian)流(liu)進行濾波。此(ci)處電(dian)流(liu)經過(guo)一次過(guo)濾，比較平穩，發(fa)(fa)生(sheng)爆漿(jiang)的(de)可能性相對(dui)來說(shuo)(shuo)小了(le)不少。但如果環境(jing)溫度過(guo)高，電(dian)容同樣容易(yi)發(fa)(fa)生(sheng)爆漿(jiang)。爆，報也。采(cai)用垃圾東西自然(ran)要爆，報應啊。欲(yu)知過(guo)去因者(zhe)(zhe)，見(jian)其現在(zai)果;欲(yu)知未(wei)來果者(zhe)(zhe)，見(jian)其現在(zai)因。
電(dian)解電(dian)容(rong)爆(bao)漿的(de)原(yuan)因：
電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)爆(bao)(bao)漿(jiang)的(de)(de)(de)(de)原因有很多，比如電(dian)(dian)(dian)(dian)(dian)流大(da)于允許的(de)(de)(de)(de)穩波電(dian)(dian)(dian)(dian)(dian)流、使(shi)(shi)(shi)(shi)用(yong)(yong)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)超出工(gong)作電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)、逆向電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)、頻繁的(de)(de)(de)(de)充放(fang)電(dian)(dian)(dian)(dian)(dian)等。但是(shi)最直(zhi)接的(de)(de)(de)(de)原因就(jiu)是(shi)高溫(wen)(wen)。我們(men)(men)知(zhi)道電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)有一個重要的(de)(de)(de)(de)參(can)數就(jiu)是(shi)耐(nai)溫(wen)(wen)值，指(zhi)的(de)(de)(de)(de)就(jiu)是(shi)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)內(nei)部(bu)(bu)電(dian)(dian)(dian)(dian)(dian)解液的(de)(de)(de)(de)沸(fei)點。當(dang)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)的(de)(de)(de)(de)內(nei)部(bu)(bu)溫(wen)(wen)度(du)達到電(dian)(dian)(dian)(dian)(dian)解液的(de)(de)(de)(de)沸(fei)點時(shi)，電(dian)(dian)(dian)(dian)(dian)解液開始沸(fei)騰，電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)內(nei)部(bu)(bu)的(de)(de)(de)(de)壓(ya)(ya)力升高，當(dang)壓(ya)(ya)力超過(guo)泄(xie)爆(bao)(bao)口的(de)(de)(de)(de)承受極限(xian)就(jiu)發(fa)生(sheng)(sheng)了(le)爆(bao)(bao)漿(jiang)。所以說溫(wen)(wen)度(du)是(shi)導致電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)爆(bao)(bao)漿(jiang)的(de)(de)(de)(de)直(zhi)接原因。電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)設計(ji)(ji)使(shi)(shi)(shi)(shi)用(yong)(yong)壽(shou)(shou)命(ming)(ming)大(da)約為2萬(wan)小時(shi)，受環(huan)境(jing)(jing)溫(wen)(wen)度(du)的(de)(de)(de)(de)影(ying)響也很大(da)。電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)的(de)(de)(de)(de)使(shi)(shi)(shi)(shi)用(yong)(yong)壽(shou)(shou)命(ming)(ming)隨溫(wen)(wen)度(du)的(de)(de)(de)(de)增加(jia)而(er)減小，實(shi)驗證(zheng)明環(huan)境(jing)(jing)溫(wen)(wen)度(du)每升高10℃，電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)的(de)(de)(de)(de)壽(shou)(shou)命(ming)(ming)就(jiu)會(hui)減半。主要原因就(jiu)是(shi)溫(wen)(wen)度(du)加(jia)速化學反應而(er)使(shi)(shi)(shi)(shi)介質隨時(shi)間退化失效，這樣電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)壽(shou)(shou)命(ming)(ming)終結。為了(le)保(bao)(bao)證(zheng)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)的(de)(de)(de)(de)穩定性，電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)在插板(ban)前要經過(guo)長時(shi)間的(de)(de)(de)(de)高溫(wen)(wen)環(huan)境(jing)(jing)的(de)(de)(de)(de)測(ce)試。即使(shi)(shi)(shi)(shi)是(shi)在100℃，高品質的(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)也可(ke)以工(gong)作幾千個小時(shi)。同時(shi)，我們(men)(men)提到的(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)的(de)(de)(de)(de)壽(shou)(shou)命(ming)(ming)是(shi)指(zhi)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)在使(shi)(shi)(shi)(shi)用(yong)(yong)過(guo)程中，電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)容(rong)(rong)(rong)量不會(hui)超過(guo)標(biao)準范(fan)圍變(bian)化的(de)(de)(de)(de)10%。電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)壽(shou)(shou)命(ming)(ming)指(zhi)的(de)(de)(de)(de)是(shi)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)容(rong)(rong)(rong)量的(de)(de)(de)(de)問題，而(er)不是(shi)設計(ji)(ji)壽(shou)(shou)命(ming)(ming)到達之后就(jiu)發(fa)生(sheng)(sheng)爆(bao)(bao)漿(jiang)。只是(shi)無法保(bao)(bao)證(zheng)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)的(de)(de)(de)(de)設計(ji)(ji)的(de)(de)(de)(de)容(rong)(rong)(rong)量標(biao)準。
所以(yi)，短時期內，正(zheng)常使(shi)用(yong)的(de)(de)板卡電(dian)容(rong)就發(fa)生爆(bao)漿的(de)(de)情(qing)況，這就是電(dian)容(rong)品質(zhi)問題。另(ling)外(wai)，不正(zheng)常的(de)(de)使(shi)用(yong)情(qing)況也(ye)有可(ke)能(neng)發(fa)生電(dian)容(rong)爆(bao)漿的(de)(de)情(qing)況。比如熱(re)插拔電(dian)腦配件(jian)也(ye)會(hui)導致板卡局部電(dian)路(lu)電(dian)流、電(dian)壓的(de)(de)劇烈變(bian)化，從而(er)引(yin)發(fa)電(dian)容(rong)使(shi)用(yong)故(gu)障(zhang)。
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