詳解電容在電源中所起到的作用
2019/7/1 12:46:11??????點擊：
作(zuo)為無源元件之一(yi)的電容(rong)，其(qi)作(zuo)用不(bu)外乎以(yi)下幾(ji)種(zhong)：
1、應用于(yu)電源電路，實現(xian)旁(pang)路、去藕、濾(lv)波(bo)和儲能方面(mian)電容的作用，下(xia)面(mian)分(fen)類詳(xiang)述之(zhi)：
1)濾波(bo)
濾(lv)波是(shi)電(dian)(dian)(dian)容(rong)(rong)的(de)(de)作用中(zhong)很(hen)重要的(de)(de)一部分。幾乎所有的(de)(de)電(dian)(dian)(dian)源電(dian)(dian)(dian)路中(zhong)都會用到。從理論上(shang)(即(ji)假設電(dian)(dian)(dian)容(rong)(rong)為(wei)純電(dian)(dian)(dian)容(rong)(rong))說(shuo)，電(dian)(dian)(dian)容(rong)(rong)越(yue)(yue)大(da)，阻(zu)(zu)抗(kang)越(yue)(yue)小(xiao)，通(tong)(tong)過(guo)的(de)(de)頻(pin)(pin)(pin)率也(ye)越(yue)(yue)高(gao)(gao)。但實際上(shang)超過(guo)1uF的(de)(de)電(dian)(dian)(dian)容(rong)(rong)大(da)多為(wei)電(dian)(dian)(dian)解電(dian)(dian)(dian)容(rong)(rong)，有很(hen)大(da)的(de)(de)電(dian)(dian)(dian)感成(cheng)份，所以(yi)頻(pin)(pin)(pin)率高(gao)(gao)后(hou)反而阻(zu)(zu)抗(kang)會增大(da)。有時(shi)(shi)會看到有一個電(dian)(dian)(dian)容(rong)(rong)量(liang)較大(da)電(dian)(dian)(dian)解電(dian)(dian)(dian)容(rong)(rong)并聯了一個小(xiao)電(dian)(dian)(dian)容(rong)(rong)，這時(shi)(shi)大(da)電(dian)(dian)(dian)容(rong)(rong)通(tong)(tong)低頻(pin)(pin)(pin)，小(xiao)電(dian)(dian)(dian)容(rong)(rong)通(tong)(tong)高(gao)(gao)頻(pin)(pin)(pin)。電(dian)(dian)(dian)容(rong)(rong)的(de)(de)作用就是(shi)通(tong)(tong)高(gao)(gao)阻(zu)(zu)低，通(tong)(tong)高(gao)(gao)頻(pin)(pin)(pin)阻(zu)(zu)低頻(pin)(pin)(pin)。電(dian)(dian)(dian)容(rong)(rong)越(yue)(yue)大(da)低頻(pin)(pin)(pin)越(yue)(yue)容(rong)(rong)易通(tong)(tong)過(guo)，電(dian)(dian)(dian)容(rong)(rong)越(yue)(yue)大(da)高(gao)(gao)頻(pin)(pin)(pin)越(yue)(yue)容(rong)(rong)易通(tong)(tong)過(guo)。具體用在(zai)濾(lv)波中(zhong),大(da)電(dian)(dian)(dian)容(rong)(rong)(1000uF)濾(lv)低頻(pin)(pin)(pin)，小(xiao)電(dian)(dian)(dian)容(rong)(rong)(20pF)濾(lv)高(gao)(gao)頻(pin)(pin)(pin)。
曾有網(wang)友(you)將濾波(bo)電(dian)(dian)容(rong)(rong) 比作“水(shui)(shui)塘”。由于電(dian)(dian)容(rong)(rong)的兩端(duan)電(dian)(dian)壓(ya)不會突(tu)變，由此可知，信號頻率越高(gao)則衰減越大(da)，可很形象的說(shuo)電(dian)(dian)容(rong)(rong)像個水(shui)(shui)塘，不會因幾滴水(shui)(shui)的加入(ru)或蒸發而(er)引起水(shui)(shui)量(liang)的變化(hua)。 它(ta)把電(dian)(dian)壓(ya)的變動轉化(hua)為電(dian)(dian)流的變化(hua)，頻率越高(gao)，峰值(zhi)電(dian)(dian)流就越大(da)，從而(er)緩(huan)沖了(le)電(dian)(dian)壓(ya)。濾波(bo)就是充電(dian)(dian)，放電(dian)(dian)的過(guo)程。
2)旁(pang)路
旁(pang)路(lu)電(dian)(dian)(dian)容(rong)(rong)是(shi)為(wei)本地(di)(di)器(qi)件(jian)(jian)(jian)提供(gong)能(neng)量(liang)的(de)儲(chu)能(neng)器(qi)件(jian)(jian)(jian)，它(ta)能(neng)使穩壓器(qi)的(de)輸(shu)出均勻化(hua)，降低負載(zai)需求。就像小(xiao)型可充電(dian)(dian)(dian)電(dian)(dian)(dian)池一樣，旁(pang)路(lu)電(dian)(dian)(dian)容(rong)(rong)能(neng)夠(gou)被充電(dian)(dian)(dian)，并向器(qi)件(jian)(jian)(jian)進行(xing)放 電(dian)(dian)(dian)。為(wei)盡量(liang)減(jian)少阻抗，旁(pang)路(lu)電(dian)(dian)(dian)容(rong)(rong)要盡量(liang)靠近負載(zai)器(qi)件(jian)(jian)(jian)的(de)供(gong)電(dian)(dian)(dian)電(dian)(dian)(dian)源管(guan)腳(jiao)和地(di)(di)管(guan)腳(jiao)。這能(neng)夠(gou)很好(hao)地(di)(di)防止(zhi)輸(shu)入值過大而導致的(de)地(di)(di)電(dian)(dian)(dian)位抬高和噪聲(sheng)。地(di)(di)彈是(shi)地(di)(di)連接(jie)處在(zai)通(tong)過大 電(dian)(dian)(dian)流毛刺時的(de)電(dian)(dian)(dian)壓降。
3)去藕
去(qu)藕(ou)(ou)，又稱解(jie)藕(ou)(ou)。從電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)來(lai)(lai)說，總是(shi)(shi)(shi)(shi)可以區(qu)分為(wei)驅(qu)(qu)動的(de)(de)源和(he)被(bei)驅(qu)(qu)動的(de)(de)負載。如果(guo)負載電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)比(bi)較大(da)(da)(da)，驅(qu)(qu)動電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)要把(ba)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)充電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)、放電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)，才能完成信(xin)(xin)號(hao)(hao)的(de)(de)跳(tiao)變(bian)，在上 升沿(yan)比(bi)較陡(dou)峭的(de)(de)時(shi)候，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)比(bi)較大(da)(da)(da)，這(zhe)樣驅(qu)(qu)動的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)就(jiu)(jiu)會吸(xi)收很大(da)(da)(da)的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)，由于(yu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)中的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)感，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(特別是(shi)(shi)(shi)(shi)芯(xin)片(pian)管(guan)腳(jiao)上的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)感，會產(chan)生反(fan)彈(dan))，這(zhe)種(zhong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)相對(dui) 于(yu)正常情況來(lai)(lai)說實際上就(jiu)(jiu)是(shi)(shi)(shi)(shi)一(yi)(yi)(yi)種(zhong)噪(zao)聲，會影(ying)響(xiang)前級的(de)(de)正常工作(zuo)。這(zhe)就(jiu)(jiu)是(shi)(shi)(shi)(shi)耦(ou)合(he)。去(qu)藕(ou)(ou)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)就(jiu)(jiu)是(shi)(shi)(shi)(shi)起到一(yi)(yi)(yi)個電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)的(de)(de)作(zuo)用，滿足驅(qu)(qu)動電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)的(de)(de)變(bian)化(hua)，避免相互(hu)間(jian)的(de)(de)耦(ou)合(he)干(gan)(gan)擾(rao)。將(jiang)(jiang)旁(pang)路(lu)(lu)(lu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)和(he)去(qu)藕(ou)(ou)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)結合(he)起來(lai)(lai)將(jiang)(jiang)更容(rong)(rong)易理(li)解(jie)。旁(pang)路(lu)(lu)(lu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)實際也(ye)是(shi)(shi)(shi)(shi)去(qu)藕(ou)(ou)合(he)的(de)(de)，只(zhi)是(shi)(shi)(shi)(shi)旁(pang)路(lu)(lu)(lu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)一(yi)(yi)(yi)般(ban)(ban)是(shi)(shi)(shi)(shi)指(zhi)高頻(pin)旁(pang)路(lu)(lu)(lu)，也(ye)就(jiu)(jiu)是(shi)(shi)(shi)(shi)給高頻(pin)的(de)(de)開關噪(zao)聲提高一(yi)(yi)(yi)條低阻(zu)抗(kang)泄防 途徑。高頻(pin)旁(pang)路(lu)(lu)(lu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)一(yi)(yi)(yi)般(ban)(ban)比(bi)較小(xiao)，根據(ju)諧振頻(pin)率(lv)一(yi)(yi)(yi)般(ban)(ban)是(shi)(shi)(shi)(shi)0.1u，0.01u等(deng)，而(er)去(qu)耦(ou)合(he)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)一(yi)(yi)(yi)般(ban)(ban)比(bi)較大(da)(da)(da)，是(shi)(shi)(shi)(shi)10uF或者更大(da)(da)(da)，依據(ju)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)中分布參(can)數，以及驅(qu)(qu)動 電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)的(de)(de)變(bian)化(hua)大(da)(da)(da)小(xiao)來(lai)(lai)確定。旁(pang)路(lu)(lu)(lu)是(shi)(shi)(shi)(shi)把(ba)輸(shu)入信(xin)(xin)號(hao)(hao)中的(de)(de)干(gan)(gan)擾(rao)作(zuo)為(wei)濾除(chu)對(dui)象，而(er)去(qu)耦(ou)是(shi)(shi)(shi)(shi)把(ba)輸(shu)出信(xin)(xin)號(hao)(hao)的(de)(de)干(gan)(gan)擾(rao)作(zuo)為(wei)濾除(chu)對(dui)象，防止干(gan)(gan)擾(rao)信(xin)(xin)號(hao)(hao)返回電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源。這(zhe)應該(gai)是(shi)(shi)(shi)(shi)他(ta)們(men)的(de)(de)本質(zhi)區(qu)別。
4)儲(chu)能
儲(chu)能(neng)型電(dian)容(rong)器通過整流器收集電(dian)荷(he)，并將存儲(chu)的(de)能(neng)量通過變換(huan)器引線傳送至電(dian)源的(de)輸出端(duan)。電(dian)壓(ya)額定值為40～450VDC、電(dian)容(rong)值在220～150 000uF之(zhi)間的(de)鋁電(dian)解電(dian)容(rong)器(如EPCOS公司的(de) B43504或B43505)是較為常用(yong)(yong)的(de)。根(gen)據不同(tong)的(de)電(dian)源要求，器件有時會采(cai)用(yong)(yong)串聯、并聯或其組合的(de)形式， 對于功率級超過10KW的(de)電(dian)源，通常采(cai)用(yong)(yong)體積較大的(de)罐形螺(luo)旋端(duan)子電(dian)容(rong)器。
2、應用(yong)于(yu)信號電路，主要(yao)完成(cheng)耦合、振蕩(dang)/同(tong)步(bu)及時間常數的作(zuo)用(yong)：
1)耦合
舉個例子來講，晶體管(guan)放大器(qi)(qi)發射極有一(yi)個自給偏壓電(dian)(dian)(dian)(dian)阻(zu)(zu)，它同時又使(shi)信(xin)號(hao)產(chan)生(sheng)壓降反饋到(dao)輸入(ru)端(duan)形成了輸入(ru)輸出信(xin)號(hao)耦(ou)(ou)合，這(zhe)個電(dian)(dian)(dian)(dian)阻(zu)(zu)就(jiu)是產(chan)生(sheng)了耦(ou)(ou)合的元件，如(ru)果在這(zhe)個電(dian)(dian)(dian)(dian)阻(zu)(zu)兩端(duan)并聯一(yi)個電(dian)(dian)(dian)(dian)容(rong)(rong)，由于適當容(rong)(rong)量的電(dian)(dian)(dian)(dian)容(rong)(rong)器(qi)(qi)對交(jiao)流信(xin)號(hao)較小的阻(zu)(zu)抗(kang),這(zhe)樣(yang)就(jiu)減小了電(dian)(dian)(dian)(dian)阻(zu)(zu)產(chan)生(sheng)的耦(ou)(ou)合效應，故稱(cheng)此電(dian)(dian)(dian)(dian)容(rong)(rong)為去耦(ou)(ou)電(dian)(dian)(dian)(dian)容(rong)(rong)。
2)振蕩(dang)/同步(bu)
包(bao)括RC、LC振蕩器(qi)及晶體的負載電容(rong)都屬于這一范疇。
3)時間常數
這就是常見的(de) R、C 串聯(lian)構成的(de)積(ji)分電(dian)(dian)(dian)(dian)路(lu)。當(dang)輸入信號電(dian)(dian)(dian)(dian)壓(ya)加在輸入端時，電(dian)(dian)(dian)(dian)容(C)上(shang)的(de)電(dian)(dian)(dian)(dian)壓(ya)逐(zhu)漸上(shang)升(sheng)(sheng)。而其充電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流則隨著(zhu)電(dian)(dian)(dian)(dian)壓(ya)的(de)上(shang)升(sheng)(sheng)而減小。電(dian)(dian)(dian)(dian)流通過電(dian)(dian)(dian)(dian)阻(R)、電(dian)(dian)(dian)(dian)容(C)的(de)特(te)性通過下(xia)面的(de)公式描述(shu)：
i = (V/R)e-(t/CR)
我們知道了電容的作用以后(hou)下面來談談電容在使(shi)用中的注意事項
A. 什么是好電容。
1.電(dian)容(rong)容(rong)量越(yue)大越(yue)好。
很多人在(zai)電(dian)(dian)(dian)(dian)容(rong)(rong)的(de)(de)(de)(de)(de)替換中(zhong)(zhong)往(wang)往(wang)愛(ai)用大(da)(da)容(rong)(rong)量的(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)容(rong)(rong)。我們知道雖(sui)然電(dian)(dian)(dian)(dian)容(rong)(rong)越(yue)(yue)(yue)大(da)(da)，為IC提供(gong)的(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)流(liu)(liu)補(bu)償的(de)(de)(de)(de)(de)能(neng)(neng)力越(yue)(yue)(yue)強。且不說電(dian)(dian)(dian)(dian)容(rong)(rong)容(rong)(rong)量的(de)(de)(de)(de)(de)增(zeng)大(da)(da)帶(dai)來(lai)的(de)(de)(de)(de)(de)體(ti)積變大(da)(da)，增(zeng)加成(cheng)本的(de)(de)(de)(de)(de)同(tong)時(shi)還影(ying)響空氣流(liu)(liu)動(dong)和散熱。關鍵(jian)在(zai)于電(dian)(dian)(dian)(dian)容(rong)(rong)上存在(zai)寄生電(dian)(dian)(dian)(dian)感，電(dian)(dian)(dian)(dian)容(rong)(rong)放(fang)電(dian)(dian)(dian)(dian)回路(lu)會在(zai)某個頻(pin)點(dian)上發生諧振。在(zai)諧振點(dian)，電(dian)(dian)(dian)(dian)容(rong)(rong)的(de)(de)(de)(de)(de)阻抗(kang)小。因此放(fang)電(dian)(dian)(dian)(dian)回路(lu)的(de)(de)(de)(de)(de)阻抗(kang)最(zui)小，補(bu)充能(neng)(neng)量的(de)(de)(de)(de)(de)效(xiao)果(guo)也(ye)最(zui)好(hao)。但當頻(pin)率超(chao)過諧振點(dian)時(shi)，放(fang)電(dian)(dian)(dian)(dian)回路(lu)的(de)(de)(de)(de)(de)阻抗(kang)開始增(zeng)加，電(dian)(dian)(dian)(dian)容(rong)(rong)提供(gong)電(dian)(dian)(dian)(dian)流(liu)(liu)能(neng)(neng)力便開始下降。電(dian)(dian)(dian)(dian)容(rong)(rong)的(de)(de)(de)(de)(de)容(rong)(rong)值(zhi)(zhi)越(yue)(yue)(yue)大(da)(da)，諧振頻(pin)率越(yue)(yue)(yue)低，電(dian)(dian)(dian)(dian)容(rong)(rong)能(neng)(neng)有效(xiao)補(bu)償電(dian)(dian)(dian)(dian)流(liu)(liu)的(de)(de)(de)(de)(de)頻(pin)率范圍也(ye)越(yue)(yue)(yue)小。從保證電(dian)(dian)(dian)(dian)容(rong)(rong)提供(gong)高頻(pin)電(dian)(dian)(dian)(dian)流(liu)(liu)的(de)(de)(de)(de)(de)能(neng)(neng)力的(de)(de)(de)(de)(de)角度(du)來(lai)說，電(dian)(dian)(dian)(dian)容(rong)(rong)越(yue)(yue)(yue)大(da)(da)越(yue)(yue)(yue)好(hao)的(de)(de)(de)(de)(de)觀(guan)點(dian)是錯誤的(de)(de)(de)(de)(de)，一(yi)般的(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)路(lu)設(she)計中(zhong)(zhong)都有一(yi)個參考(kao)值(zhi)(zhi)的(de)(de)(de)(de)(de)。
2.同(tong)樣容量的電容，并聯越(yue)多的小電容越(yue)好
耐壓(ya)值(zhi)、耐溫值(zhi)、容(rong)(rong)(rong)值(zhi)、ESR(等(deng)(deng)效電(dian)阻(zu))等(deng)(deng)是(shi)電(dian)容(rong)(rong)(rong)的(de)(de)幾(ji)個重要參數，對于ESR自然是(shi)越(yue)低越(yue)好。ESR與電(dian)容(rong)(rong)(rong)的(de)(de)容(rong)(rong)(rong)量、頻率、電(dian)壓(ya)、溫度等(deng)(deng)都有(you)關系(xi)。當(dang)電(dian)壓(ya)固定時(shi)候，容(rong)(rong)(rong)量越(yue)大，ESR越(yue)低。在(zai)板卡(ka)設計中采用多個小電(dian)容(rong)(rong)(rong)并(bing)連多是(shi)出與PCB空間的(de)(de)限制，這(zhe)樣有(you)的(de)(de)人就認為，越(yue)多的(de)(de)并(bing)聯小電(dian)阻(zu)，ESR越(yue)低，效果(guo)越(yue)好。理論上(shang)是(shi)如此，但(dan)是(shi)要考慮到電(dian)容(rong)(rong)(rong)接腳焊點的(de)(de)阻(zu)抗(kang)，采用多個小電(dian)容(rong)(rong)(rong)并(bing)聯，效果(guo)并(bing)不一定突(tu)出。
3.ESR越低，效果越好。
結合我們上面的(de)提高的(de)供電(dian)(dian)(dian)電(dian)(dian)(dian)路(lu)(lu)來(lai)(lai)說，對(dui)于輸(shu)入電(dian)(dian)(dian)容(rong)(rong)(rong)來(lai)(lai)說，輸(shu)入電(dian)(dian)(dian)容(rong)(rong)(rong)的(de)容(rong)(rong)(rong)量要(yao)(yao)大一(yi)(yi)(yi)點。相對(dui)容(rong)(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)降低(di)(di)。因為(wei)輸(shu)入電(dian)(dian)(dian)容(rong)(rong)(rong)主要(yao)(yao)是耐(nai)壓，其次是吸收MOSFET的(de)開關脈沖。對(dui)于輸(shu)出電(dian)(dian)(dian)容(rong)(rong)(rong)來(lai)(lai)說，耐(nai)壓的(de)要(yao)(yao)求(qiu)和(he)容(rong)(rong)(rong)量可以適當的(de)降低(di)(di)一(yi)(yi)(yi)點。ESR的(de)要(yao)(yao)求(qiu)則高一(yi)(yi)(yi)點，因為(wei)這里要(yao)(yao)保(bao)證的(de)是足夠的(de)電(dian)(dian)(dian)流通過量。但(dan)這里要(yao)(yao)注意的(de)是ESR并不是越(yue)(yue)低(di)(di)越(yue)(yue)好，低(di)(di)ESR電(dian)(dian)(dian)容(rong)(rong)(rong)會引起開關電(dian)(dian)(dian)路(lu)(lu)振蕩(dang)。而消振電(dian)(dian)(dian)路(lu)(lu)復雜同時會導致成本(ben)(ben)的(de)增(zeng)加(jia)。板卡設計中，這里一(yi)(yi)(yi)般有一(yi)(yi)(yi)個參考值，此作為(wei)元件選用(yong)參數(shu)，避免消振電(dian)(dian)(dian)路(lu)(lu)而導致成本(ben)(ben)的(de)增(zeng)加(jia)。
4.好電(dian)容代(dai)表(biao)著高(gao)品(pin)質。
“唯電容(rong)論”曾經盛極一(yi)(yi)時，一(yi)(yi)些廠(chang)(chang)商(shang)和媒體也刻意(yi)的(de)(de)把(ba)(ba)這個事情做(zuo)成一(yi)(yi)個賣點。在板卡設(she)計(ji)中，電路(lu)設(she)計(ji)水平是關鍵。和有的(de)(de)廠(chang)(chang)商(shang)可(ke)以(yi)用(yong)兩相(xiang)供電做(zuo)出比一(yi)(yi)些廠(chang)(chang)商(shang)采用(yong)四(si)相(xiang)供電更穩定的(de)(de)產(chan)品(pin)(pin)一(yi)(yi)樣，一(yi)(yi)味的(de)(de)采用(yong)高(gao)價電容(rong)，不一(yi)(yi)定能做(zuo)出好產(chan)品(pin)(pin)。衡(heng)量一(yi)(yi)個產(chan)品(pin)(pin)，一(yi)(yi)定要全方位多角度的(de)(de)去(qu)考慮，切不可(ke)把(ba)(ba)電容(rong)的(de)(de)作用(yong)有意(yi)無意(yi)的(de)(de)夸(kua)大(da)。
B. 電容爆漿(jiang)之面面談(tan)
爆漿的(de)種(zhong)類：
分兩(liang)類，輸(shu)入電(dian)(dian)容爆漿(jiang)和輸(shu)出電(dian)(dian)容爆漿(jiang)。
對(dui)于(yu)輸入(ru)(ru)電(dian)(dian)容來說，就(jiu)是(shi)(shi)我是(shi)(shi)說的(de)C1，C1對(dui)由(you)電(dian)(dian)源(yuan)接收到的(de)電(dian)(dian)流進行過(guo)濾。輸入(ru)(ru)電(dian)(dian)容爆漿和電(dian)(dian)源(yuan)輸入(ru)(ru)電(dian)(dian)流的(de)品(pin)質有關(guan)。過(guo)多的(de)毛刺電(dian)(dian)壓，峰值(zhi)電(dian)(dian)壓過(guo)高，電(dian)(dian)流不(bu)穩定等(deng)都使電(dian)(dian)容過(guo)于(yu)充放電(dian)(dian)過(guo)于(yu)頻繁，長(chang)時間(jian)處于(yu)這類工作(zuo)環境下的(de)電(dian)(dian)容，內部溫度(du)升高很快。超過(guo)泄爆口(kou)的(de)承(cheng)受(shou)極限就(jiu)會(hui)發生(sheng)爆漿。
對于輸出電(dian)容(rong)(rong)來(lai)說(shuo)，就(jiu)我說(shuo)的(de)C2，對經(jing)電(dian)源(yuan)模塊調整后的(de)電(dian)流進行濾(lv)波(bo)。此處電(dian)流經(jing)過(guo)一次過(guo)濾(lv)，比較(jiao)平穩，發生(sheng)爆漿的(de)可(ke)能性相對來(lai)說(shuo)小(xiao)了(le)不少(shao)。但如果(guo)環境溫度過(guo)高(gao)，電(dian)容(rong)(rong)同樣容(rong)(rong)易(yi)發生(sheng)爆漿。爆，報也。采用垃圾(ji)東(dong)西自然(ran)要爆，報應(ying)啊。欲知過(guo)去(qu)因者，見(jian)其現(xian)在果(guo);欲知未(wei)來(lai)果(guo)者，見(jian)其現(xian)在因。
電解(jie)電容(rong)爆漿的原因：
電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)爆(bao)漿的(de)(de)(de)(de)原因有很多，比如電(dian)(dian)(dian)(dian)(dian)流大于允許的(de)(de)(de)(de)穩波電(dian)(dian)(dian)(dian)(dian)流、使(shi)用電(dian)(dian)(dian)(dian)(dian)壓超出(chu)工作電(dian)(dian)(dian)(dian)(dian)壓、逆向電(dian)(dian)(dian)(dian)(dian)壓、頻繁的(de)(de)(de)(de)充放(fang)電(dian)(dian)(dian)(dian)(dian)等。但是(shi)(shi)(shi)最直接的(de)(de)(de)(de)原因就(jiu)(jiu)(jiu)是(shi)(shi)(shi)高溫(wen)。我們知道(dao)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)有一個重要(yao)的(de)(de)(de)(de)參數就(jiu)(jiu)(jiu)是(shi)(shi)(shi)耐(nai)溫(wen)值，指的(de)(de)(de)(de)就(jiu)(jiu)(jiu)是(shi)(shi)(shi)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)內部(bu)(bu)電(dian)(dian)(dian)(dian)(dian)解液的(de)(de)(de)(de)沸點(dian)。當電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)的(de)(de)(de)(de)內部(bu)(bu)溫(wen)度(du)(du)達到電(dian)(dian)(dian)(dian)(dian)解液的(de)(de)(de)(de)沸點(dian)時(shi)，電(dian)(dian)(dian)(dian)(dian)解液開(kai)始(shi)沸騰，電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)內部(bu)(bu)的(de)(de)(de)(de)壓力升高，當壓力超過(guo)泄爆(bao)口的(de)(de)(de)(de)承受極限就(jiu)(jiu)(jiu)發生(sheng)了爆(bao)漿。所以(yi)說溫(wen)度(du)(du)是(shi)(shi)(shi)導(dao)致(zhi)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)爆(bao)漿的(de)(de)(de)(de)直接原因。電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)設計(ji)使(shi)用壽(shou)(shou)(shou)命(ming)(ming)(ming)大約為2萬(wan)小(xiao)時(shi)，受環(huan)境(jing)溫(wen)度(du)(du)的(de)(de)(de)(de)影(ying)響也(ye)很大。電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)的(de)(de)(de)(de)使(shi)用壽(shou)(shou)(shou)命(ming)(ming)(ming)隨溫(wen)度(du)(du)的(de)(de)(de)(de)增加而減小(xiao)，實驗證明環(huan)境(jing)溫(wen)度(du)(du)每升高10℃，電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)的(de)(de)(de)(de)壽(shou)(shou)(shou)命(ming)(ming)(ming)就(jiu)(jiu)(jiu)會(hui)減半。主(zhu)要(yao)原因就(jiu)(jiu)(jiu)是(shi)(shi)(shi)溫(wen)度(du)(du)加速化(hua)學反(fan)應而使(shi)介質隨時(shi)間(jian)退化(hua)失(shi)效，這樣電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)壽(shou)(shou)(shou)命(ming)(ming)(ming)終結(jie)。為了保證電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)的(de)(de)(de)(de)穩定性，電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)在(zai)插(cha)板(ban)前要(yao)經過(guo)長時(shi)間(jian)的(de)(de)(de)(de)高溫(wen)環(huan)境(jing)的(de)(de)(de)(de)測試。即使(shi)是(shi)(shi)(shi)在(zai)100℃，高品質的(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)也(ye)可以(yi)工作幾千個小(xiao)時(shi)。同時(shi)，我們提到的(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)的(de)(de)(de)(de)壽(shou)(shou)(shou)命(ming)(ming)(ming)是(shi)(shi)(shi)指電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)在(zai)使(shi)用過(guo)程中，電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)容(rong)(rong)(rong)(rong)(rong)量(liang)不(bu)會(hui)超過(guo)標(biao)準(zhun)(zhun)范圍變化(hua)的(de)(de)(de)(de)10%。電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)壽(shou)(shou)(shou)命(ming)(ming)(ming)指的(de)(de)(de)(de)是(shi)(shi)(shi)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)容(rong)(rong)(rong)(rong)(rong)量(liang)的(de)(de)(de)(de)問題，而不(bu)是(shi)(shi)(shi)設計(ji)壽(shou)(shou)(shou)命(ming)(ming)(ming)到達之后(hou)就(jiu)(jiu)(jiu)發生(sheng)爆(bao)漿。只是(shi)(shi)(shi)無法保證電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)的(de)(de)(de)(de)設計(ji)的(de)(de)(de)(de)容(rong)(rong)(rong)(rong)(rong)量(liang)標(biao)準(zhun)(zhun)。
所以(yi)，短時期內，正(zheng)常使(shi)用的板(ban)卡電(dian)(dian)容就發(fa)生爆漿的情況(kuang)(kuang)，這就是電(dian)(dian)容品質問題。另外(wai)，不正(zheng)常的使(shi)用情況(kuang)(kuang)也有可(ke)能發(fa)生電(dian)(dian)容爆漿的情況(kuang)(kuang)。比如熱(re)插拔電(dian)(dian)腦配件也會導(dao)致板(ban)卡局部電(dian)(dian)路電(dian)(dian)流、電(dian)(dian)壓的劇烈變化(hua)，從而(er)引發(fa)電(dian)(dian)容使(shi)用故(gu)障。
1、應用于(yu)電源電路，實現(xian)旁(pang)路、去藕、濾(lv)波(bo)和儲能方面(mian)電容的作用，下(xia)面(mian)分(fen)類詳(xiang)述之(zhi)：
1)濾波(bo)
濾(lv)波是(shi)電(dian)(dian)(dian)容(rong)(rong)的(de)(de)作用中(zhong)很(hen)重要的(de)(de)一部分。幾乎所有的(de)(de)電(dian)(dian)(dian)源電(dian)(dian)(dian)路中(zhong)都會用到。從理論上(shang)(即(ji)假設電(dian)(dian)(dian)容(rong)(rong)為(wei)純電(dian)(dian)(dian)容(rong)(rong))說(shuo)，電(dian)(dian)(dian)容(rong)(rong)越(yue)(yue)大(da)，阻(zu)(zu)抗(kang)越(yue)(yue)小(xiao)，通(tong)(tong)過(guo)的(de)(de)頻(pin)(pin)(pin)率也(ye)越(yue)(yue)高(gao)(gao)。但實際上(shang)超過(guo)1uF的(de)(de)電(dian)(dian)(dian)容(rong)(rong)大(da)多為(wei)電(dian)(dian)(dian)解電(dian)(dian)(dian)容(rong)(rong)，有很(hen)大(da)的(de)(de)電(dian)(dian)(dian)感成(cheng)份，所以(yi)頻(pin)(pin)(pin)率高(gao)(gao)后(hou)反而阻(zu)(zu)抗(kang)會增大(da)。有時(shi)(shi)會看到有一個電(dian)(dian)(dian)容(rong)(rong)量(liang)較大(da)電(dian)(dian)(dian)解電(dian)(dian)(dian)容(rong)(rong)并聯了一個小(xiao)電(dian)(dian)(dian)容(rong)(rong)，這時(shi)(shi)大(da)電(dian)(dian)(dian)容(rong)(rong)通(tong)(tong)低頻(pin)(pin)(pin)，小(xiao)電(dian)(dian)(dian)容(rong)(rong)通(tong)(tong)高(gao)(gao)頻(pin)(pin)(pin)。電(dian)(dian)(dian)容(rong)(rong)的(de)(de)作用就是(shi)通(tong)(tong)高(gao)(gao)阻(zu)(zu)低，通(tong)(tong)高(gao)(gao)頻(pin)(pin)(pin)阻(zu)(zu)低頻(pin)(pin)(pin)。電(dian)(dian)(dian)容(rong)(rong)越(yue)(yue)大(da)低頻(pin)(pin)(pin)越(yue)(yue)容(rong)(rong)易通(tong)(tong)過(guo)，電(dian)(dian)(dian)容(rong)(rong)越(yue)(yue)大(da)高(gao)(gao)頻(pin)(pin)(pin)越(yue)(yue)容(rong)(rong)易通(tong)(tong)過(guo)。具體用在(zai)濾(lv)波中(zhong),大(da)電(dian)(dian)(dian)容(rong)(rong)(1000uF)濾(lv)低頻(pin)(pin)(pin)，小(xiao)電(dian)(dian)(dian)容(rong)(rong)(20pF)濾(lv)高(gao)(gao)頻(pin)(pin)(pin)。
曾有網(wang)友(you)將濾波(bo)電(dian)(dian)容(rong)(rong) 比作“水(shui)(shui)塘”。由于電(dian)(dian)容(rong)(rong)的兩端(duan)電(dian)(dian)壓(ya)不會突(tu)變，由此可知，信號頻率越高(gao)則衰減越大(da)，可很形象的說(shuo)電(dian)(dian)容(rong)(rong)像個水(shui)(shui)塘，不會因幾滴水(shui)(shui)的加入(ru)或蒸發而(er)引起水(shui)(shui)量(liang)的變化(hua)。 它(ta)把電(dian)(dian)壓(ya)的變動轉化(hua)為電(dian)(dian)流的變化(hua)，頻率越高(gao)，峰值(zhi)電(dian)(dian)流就越大(da)，從而(er)緩(huan)沖了(le)電(dian)(dian)壓(ya)。濾波(bo)就是充電(dian)(dian)，放電(dian)(dian)的過(guo)程。
2)旁(pang)路
旁(pang)路(lu)電(dian)(dian)(dian)容(rong)(rong)是(shi)為(wei)本地(di)(di)器(qi)件(jian)(jian)(jian)提供(gong)能(neng)量(liang)的(de)儲(chu)能(neng)器(qi)件(jian)(jian)(jian)，它(ta)能(neng)使穩壓器(qi)的(de)輸(shu)出均勻化(hua)，降低負載(zai)需求。就像小(xiao)型可充電(dian)(dian)(dian)電(dian)(dian)(dian)池一樣，旁(pang)路(lu)電(dian)(dian)(dian)容(rong)(rong)能(neng)夠(gou)被充電(dian)(dian)(dian)，并向器(qi)件(jian)(jian)(jian)進行(xing)放 電(dian)(dian)(dian)。為(wei)盡量(liang)減(jian)少阻抗，旁(pang)路(lu)電(dian)(dian)(dian)容(rong)(rong)要盡量(liang)靠近負載(zai)器(qi)件(jian)(jian)(jian)的(de)供(gong)電(dian)(dian)(dian)電(dian)(dian)(dian)源管(guan)腳(jiao)和地(di)(di)管(guan)腳(jiao)。這能(neng)夠(gou)很好(hao)地(di)(di)防止(zhi)輸(shu)入值過大而導致的(de)地(di)(di)電(dian)(dian)(dian)位抬高和噪聲(sheng)。地(di)(di)彈是(shi)地(di)(di)連接(jie)處在(zai)通(tong)過大 電(dian)(dian)(dian)流毛刺時的(de)電(dian)(dian)(dian)壓降。
3)去藕
去(qu)藕(ou)(ou)，又稱解(jie)藕(ou)(ou)。從電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)來(lai)(lai)說，總是(shi)(shi)(shi)(shi)可以區(qu)分為(wei)驅(qu)(qu)動的(de)(de)源和(he)被(bei)驅(qu)(qu)動的(de)(de)負載。如果(guo)負載電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)比(bi)較大(da)(da)(da)，驅(qu)(qu)動電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)要把(ba)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)充電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)、放電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)，才能完成信(xin)(xin)號(hao)(hao)的(de)(de)跳(tiao)變(bian)，在上 升沿(yan)比(bi)較陡(dou)峭的(de)(de)時(shi)候，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)比(bi)較大(da)(da)(da)，這(zhe)樣驅(qu)(qu)動的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)就(jiu)(jiu)會吸(xi)收很大(da)(da)(da)的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)，由于(yu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)中的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)感，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(特別是(shi)(shi)(shi)(shi)芯(xin)片(pian)管(guan)腳(jiao)上的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)感，會產(chan)生反(fan)彈(dan))，這(zhe)種(zhong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)相對(dui) 于(yu)正常情況來(lai)(lai)說實際上就(jiu)(jiu)是(shi)(shi)(shi)(shi)一(yi)(yi)(yi)種(zhong)噪(zao)聲，會影(ying)響(xiang)前級的(de)(de)正常工作(zuo)。這(zhe)就(jiu)(jiu)是(shi)(shi)(shi)(shi)耦(ou)合(he)。去(qu)藕(ou)(ou)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)就(jiu)(jiu)是(shi)(shi)(shi)(shi)起到一(yi)(yi)(yi)個電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)的(de)(de)作(zuo)用，滿足驅(qu)(qu)動電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)的(de)(de)變(bian)化(hua)，避免相互(hu)間(jian)的(de)(de)耦(ou)合(he)干(gan)(gan)擾(rao)。將(jiang)(jiang)旁(pang)路(lu)(lu)(lu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)和(he)去(qu)藕(ou)(ou)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)結合(he)起來(lai)(lai)將(jiang)(jiang)更容(rong)(rong)易理(li)解(jie)。旁(pang)路(lu)(lu)(lu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)實際也(ye)是(shi)(shi)(shi)(shi)去(qu)藕(ou)(ou)合(he)的(de)(de)，只(zhi)是(shi)(shi)(shi)(shi)旁(pang)路(lu)(lu)(lu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)一(yi)(yi)(yi)般(ban)(ban)是(shi)(shi)(shi)(shi)指(zhi)高頻(pin)旁(pang)路(lu)(lu)(lu)，也(ye)就(jiu)(jiu)是(shi)(shi)(shi)(shi)給高頻(pin)的(de)(de)開關噪(zao)聲提高一(yi)(yi)(yi)條低阻(zu)抗(kang)泄防 途徑。高頻(pin)旁(pang)路(lu)(lu)(lu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)一(yi)(yi)(yi)般(ban)(ban)比(bi)較小(xiao)，根據(ju)諧振頻(pin)率(lv)一(yi)(yi)(yi)般(ban)(ban)是(shi)(shi)(shi)(shi)0.1u，0.01u等(deng)，而(er)去(qu)耦(ou)合(he)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)一(yi)(yi)(yi)般(ban)(ban)比(bi)較大(da)(da)(da)，是(shi)(shi)(shi)(shi)10uF或者更大(da)(da)(da)，依據(ju)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)中分布參(can)數，以及驅(qu)(qu)動 電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)的(de)(de)變(bian)化(hua)大(da)(da)(da)小(xiao)來(lai)(lai)確定。旁(pang)路(lu)(lu)(lu)是(shi)(shi)(shi)(shi)把(ba)輸(shu)入信(xin)(xin)號(hao)(hao)中的(de)(de)干(gan)(gan)擾(rao)作(zuo)為(wei)濾除(chu)對(dui)象，而(er)去(qu)耦(ou)是(shi)(shi)(shi)(shi)把(ba)輸(shu)出信(xin)(xin)號(hao)(hao)的(de)(de)干(gan)(gan)擾(rao)作(zuo)為(wei)濾除(chu)對(dui)象，防止干(gan)(gan)擾(rao)信(xin)(xin)號(hao)(hao)返回電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源。這(zhe)應該(gai)是(shi)(shi)(shi)(shi)他(ta)們(men)的(de)(de)本質(zhi)區(qu)別。
4)儲(chu)能
儲(chu)能(neng)型電(dian)容(rong)器通過整流器收集電(dian)荷(he)，并將存儲(chu)的(de)能(neng)量通過變換(huan)器引線傳送至電(dian)源的(de)輸出端(duan)。電(dian)壓(ya)額定值為40～450VDC、電(dian)容(rong)值在220～150 000uF之(zhi)間的(de)鋁電(dian)解電(dian)容(rong)器(如EPCOS公司的(de) B43504或B43505)是較為常用(yong)(yong)的(de)。根(gen)據不同(tong)的(de)電(dian)源要求，器件有時會采(cai)用(yong)(yong)串聯、并聯或其組合的(de)形式， 對于功率級超過10KW的(de)電(dian)源，通常采(cai)用(yong)(yong)體積較大的(de)罐形螺(luo)旋端(duan)子電(dian)容(rong)器。
2、應用(yong)于(yu)信號電路，主要(yao)完成(cheng)耦合、振蕩(dang)/同(tong)步(bu)及時間常數的作(zuo)用(yong)：
1)耦合
舉個例子來講，晶體管(guan)放大器(qi)(qi)發射極有一(yi)個自給偏壓電(dian)(dian)(dian)(dian)阻(zu)(zu)，它同時又使(shi)信(xin)號(hao)產(chan)生(sheng)壓降反饋到(dao)輸入(ru)端(duan)形成了輸入(ru)輸出信(xin)號(hao)耦(ou)(ou)合，這(zhe)個電(dian)(dian)(dian)(dian)阻(zu)(zu)就(jiu)是產(chan)生(sheng)了耦(ou)(ou)合的元件，如(ru)果在這(zhe)個電(dian)(dian)(dian)(dian)阻(zu)(zu)兩端(duan)并聯一(yi)個電(dian)(dian)(dian)(dian)容(rong)(rong)，由于適當容(rong)(rong)量的電(dian)(dian)(dian)(dian)容(rong)(rong)器(qi)(qi)對交(jiao)流信(xin)號(hao)較小的阻(zu)(zu)抗(kang),這(zhe)樣(yang)就(jiu)減小了電(dian)(dian)(dian)(dian)阻(zu)(zu)產(chan)生(sheng)的耦(ou)(ou)合效應，故稱(cheng)此電(dian)(dian)(dian)(dian)容(rong)(rong)為去耦(ou)(ou)電(dian)(dian)(dian)(dian)容(rong)(rong)。
2)振蕩(dang)/同步(bu)
包(bao)括RC、LC振蕩器(qi)及晶體的負載電容(rong)都屬于這一范疇。
3)時間常數
這就是常見的(de) R、C 串聯(lian)構成的(de)積(ji)分電(dian)(dian)(dian)(dian)路(lu)。當(dang)輸入信號電(dian)(dian)(dian)(dian)壓(ya)加在輸入端時，電(dian)(dian)(dian)(dian)容(C)上(shang)的(de)電(dian)(dian)(dian)(dian)壓(ya)逐(zhu)漸上(shang)升(sheng)(sheng)。而其充電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流則隨著(zhu)電(dian)(dian)(dian)(dian)壓(ya)的(de)上(shang)升(sheng)(sheng)而減小。電(dian)(dian)(dian)(dian)流通過電(dian)(dian)(dian)(dian)阻(R)、電(dian)(dian)(dian)(dian)容(C)的(de)特(te)性通過下(xia)面的(de)公式描述(shu)：
i = (V/R)e-(t/CR)
我們知道了電容的作用以后(hou)下面來談談電容在使(shi)用中的注意事項
A. 什么是好電容。
1.電(dian)容(rong)容(rong)量越(yue)大越(yue)好。
很多人在(zai)電(dian)(dian)(dian)(dian)容(rong)(rong)的(de)(de)(de)(de)(de)替換中(zhong)(zhong)往(wang)往(wang)愛(ai)用大(da)(da)容(rong)(rong)量的(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)容(rong)(rong)。我們知道雖(sui)然電(dian)(dian)(dian)(dian)容(rong)(rong)越(yue)(yue)(yue)大(da)(da)，為IC提供(gong)的(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)流(liu)(liu)補(bu)償的(de)(de)(de)(de)(de)能(neng)(neng)力越(yue)(yue)(yue)強。且不說電(dian)(dian)(dian)(dian)容(rong)(rong)容(rong)(rong)量的(de)(de)(de)(de)(de)增(zeng)大(da)(da)帶(dai)來(lai)的(de)(de)(de)(de)(de)體(ti)積變大(da)(da)，增(zeng)加成(cheng)本的(de)(de)(de)(de)(de)同(tong)時(shi)還影(ying)響空氣流(liu)(liu)動(dong)和散熱。關鍵(jian)在(zai)于電(dian)(dian)(dian)(dian)容(rong)(rong)上存在(zai)寄生電(dian)(dian)(dian)(dian)感，電(dian)(dian)(dian)(dian)容(rong)(rong)放(fang)電(dian)(dian)(dian)(dian)回路(lu)會在(zai)某個頻(pin)點(dian)上發生諧振。在(zai)諧振點(dian)，電(dian)(dian)(dian)(dian)容(rong)(rong)的(de)(de)(de)(de)(de)阻抗(kang)小。因此放(fang)電(dian)(dian)(dian)(dian)回路(lu)的(de)(de)(de)(de)(de)阻抗(kang)最(zui)小，補(bu)充能(neng)(neng)量的(de)(de)(de)(de)(de)效(xiao)果(guo)也(ye)最(zui)好(hao)。但當頻(pin)率超(chao)過諧振點(dian)時(shi)，放(fang)電(dian)(dian)(dian)(dian)回路(lu)的(de)(de)(de)(de)(de)阻抗(kang)開始增(zeng)加，電(dian)(dian)(dian)(dian)容(rong)(rong)提供(gong)電(dian)(dian)(dian)(dian)流(liu)(liu)能(neng)(neng)力便開始下降。電(dian)(dian)(dian)(dian)容(rong)(rong)的(de)(de)(de)(de)(de)容(rong)(rong)值(zhi)(zhi)越(yue)(yue)(yue)大(da)(da)，諧振頻(pin)率越(yue)(yue)(yue)低，電(dian)(dian)(dian)(dian)容(rong)(rong)能(neng)(neng)有效(xiao)補(bu)償電(dian)(dian)(dian)(dian)流(liu)(liu)的(de)(de)(de)(de)(de)頻(pin)率范圍也(ye)越(yue)(yue)(yue)小。從保證電(dian)(dian)(dian)(dian)容(rong)(rong)提供(gong)高頻(pin)電(dian)(dian)(dian)(dian)流(liu)(liu)的(de)(de)(de)(de)(de)能(neng)(neng)力的(de)(de)(de)(de)(de)角度(du)來(lai)說，電(dian)(dian)(dian)(dian)容(rong)(rong)越(yue)(yue)(yue)大(da)(da)越(yue)(yue)(yue)好(hao)的(de)(de)(de)(de)(de)觀(guan)點(dian)是錯誤的(de)(de)(de)(de)(de)，一(yi)般的(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)路(lu)設(she)計中(zhong)(zhong)都有一(yi)個參考(kao)值(zhi)(zhi)的(de)(de)(de)(de)(de)。
2.同(tong)樣容量的電容，并聯越(yue)多的小電容越(yue)好
耐壓(ya)值(zhi)、耐溫值(zhi)、容(rong)(rong)(rong)值(zhi)、ESR(等(deng)(deng)效電(dian)阻(zu))等(deng)(deng)是(shi)電(dian)容(rong)(rong)(rong)的(de)(de)幾(ji)個重要參數，對于ESR自然是(shi)越(yue)低越(yue)好。ESR與電(dian)容(rong)(rong)(rong)的(de)(de)容(rong)(rong)(rong)量、頻率、電(dian)壓(ya)、溫度等(deng)(deng)都有(you)關系(xi)。當(dang)電(dian)壓(ya)固定時(shi)候，容(rong)(rong)(rong)量越(yue)大，ESR越(yue)低。在(zai)板卡(ka)設計中采用多個小電(dian)容(rong)(rong)(rong)并(bing)連多是(shi)出與PCB空間的(de)(de)限制，這(zhe)樣有(you)的(de)(de)人就認為，越(yue)多的(de)(de)并(bing)聯小電(dian)阻(zu)，ESR越(yue)低，效果(guo)越(yue)好。理論上(shang)是(shi)如此，但(dan)是(shi)要考慮到電(dian)容(rong)(rong)(rong)接腳焊點的(de)(de)阻(zu)抗(kang)，采用多個小電(dian)容(rong)(rong)(rong)并(bing)聯，效果(guo)并(bing)不一定突(tu)出。
3.ESR越低，效果越好。
結合我們上面的(de)提高的(de)供電(dian)(dian)(dian)電(dian)(dian)(dian)路(lu)(lu)來(lai)(lai)說，對(dui)于輸(shu)入電(dian)(dian)(dian)容(rong)(rong)(rong)來(lai)(lai)說，輸(shu)入電(dian)(dian)(dian)容(rong)(rong)(rong)的(de)容(rong)(rong)(rong)量要(yao)(yao)大一(yi)(yi)(yi)點。相對(dui)容(rong)(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)降低(di)(di)。因為(wei)輸(shu)入電(dian)(dian)(dian)容(rong)(rong)(rong)主要(yao)(yao)是耐(nai)壓，其次是吸收MOSFET的(de)開關脈沖。對(dui)于輸(shu)出電(dian)(dian)(dian)容(rong)(rong)(rong)來(lai)(lai)說，耐(nai)壓的(de)要(yao)(yao)求(qiu)和(he)容(rong)(rong)(rong)量可以適當的(de)降低(di)(di)一(yi)(yi)(yi)點。ESR的(de)要(yao)(yao)求(qiu)則高一(yi)(yi)(yi)點，因為(wei)這里要(yao)(yao)保(bao)證的(de)是足夠的(de)電(dian)(dian)(dian)流通過量。但(dan)這里要(yao)(yao)注意的(de)是ESR并不是越(yue)(yue)低(di)(di)越(yue)(yue)好，低(di)(di)ESR電(dian)(dian)(dian)容(rong)(rong)(rong)會引起開關電(dian)(dian)(dian)路(lu)(lu)振蕩(dang)。而消振電(dian)(dian)(dian)路(lu)(lu)復雜同時會導致成本(ben)(ben)的(de)增(zeng)加(jia)。板卡設計中，這里一(yi)(yi)(yi)般有一(yi)(yi)(yi)個參考值，此作為(wei)元件選用(yong)參數(shu)，避免消振電(dian)(dian)(dian)路(lu)(lu)而導致成本(ben)(ben)的(de)增(zeng)加(jia)。
4.好電(dian)容代(dai)表(biao)著高(gao)品(pin)質。
“唯電容(rong)論”曾經盛極一(yi)(yi)時，一(yi)(yi)些廠(chang)(chang)商(shang)和媒體也刻意(yi)的(de)(de)把(ba)(ba)這個事情做(zuo)成一(yi)(yi)個賣點。在板卡設(she)計(ji)中，電路(lu)設(she)計(ji)水平是關鍵。和有的(de)(de)廠(chang)(chang)商(shang)可(ke)以(yi)用(yong)兩相(xiang)供電做(zuo)出比一(yi)(yi)些廠(chang)(chang)商(shang)采用(yong)四(si)相(xiang)供電更穩定的(de)(de)產(chan)品(pin)(pin)一(yi)(yi)樣，一(yi)(yi)味的(de)(de)采用(yong)高(gao)價電容(rong)，不一(yi)(yi)定能做(zuo)出好產(chan)品(pin)(pin)。衡(heng)量一(yi)(yi)個產(chan)品(pin)(pin)，一(yi)(yi)定要全方位多角度的(de)(de)去(qu)考慮，切不可(ke)把(ba)(ba)電容(rong)的(de)(de)作用(yong)有意(yi)無意(yi)的(de)(de)夸(kua)大(da)。
B. 電容爆漿(jiang)之面面談(tan)
爆漿的(de)種(zhong)類：
分兩(liang)類，輸(shu)入電(dian)(dian)容爆漿(jiang)和輸(shu)出電(dian)(dian)容爆漿(jiang)。
對(dui)于(yu)輸入(ru)(ru)電(dian)(dian)容來說，就(jiu)是(shi)(shi)我是(shi)(shi)說的(de)C1，C1對(dui)由(you)電(dian)(dian)源(yuan)接收到的(de)電(dian)(dian)流進行過(guo)濾。輸入(ru)(ru)電(dian)(dian)容爆漿和電(dian)(dian)源(yuan)輸入(ru)(ru)電(dian)(dian)流的(de)品(pin)質有關(guan)。過(guo)多的(de)毛刺電(dian)(dian)壓，峰值(zhi)電(dian)(dian)壓過(guo)高，電(dian)(dian)流不(bu)穩定等(deng)都使電(dian)(dian)容過(guo)于(yu)充放電(dian)(dian)過(guo)于(yu)頻繁，長(chang)時間(jian)處于(yu)這類工作(zuo)環境下的(de)電(dian)(dian)容，內部溫度(du)升高很快。超過(guo)泄爆口(kou)的(de)承(cheng)受(shou)極限就(jiu)會(hui)發生(sheng)爆漿。
對于輸出電(dian)容(rong)(rong)來(lai)說(shuo)，就(jiu)我說(shuo)的(de)C2，對經(jing)電(dian)源(yuan)模塊調整后的(de)電(dian)流進行濾(lv)波(bo)。此處電(dian)流經(jing)過(guo)一次過(guo)濾(lv)，比較(jiao)平穩，發生(sheng)爆漿的(de)可(ke)能性相對來(lai)說(shuo)小(xiao)了(le)不少(shao)。但如果(guo)環境溫度過(guo)高(gao)，電(dian)容(rong)(rong)同樣容(rong)(rong)易(yi)發生(sheng)爆漿。爆，報也。采用垃圾(ji)東(dong)西自然(ran)要爆，報應(ying)啊。欲知過(guo)去(qu)因者，見(jian)其現(xian)在果(guo);欲知未(wei)來(lai)果(guo)者，見(jian)其現(xian)在因。
電解(jie)電容(rong)爆漿的原因：
電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)爆(bao)漿的(de)(de)(de)(de)原因有很多，比如電(dian)(dian)(dian)(dian)(dian)流大于允許的(de)(de)(de)(de)穩波電(dian)(dian)(dian)(dian)(dian)流、使(shi)用電(dian)(dian)(dian)(dian)(dian)壓超出(chu)工作電(dian)(dian)(dian)(dian)(dian)壓、逆向電(dian)(dian)(dian)(dian)(dian)壓、頻繁的(de)(de)(de)(de)充放(fang)電(dian)(dian)(dian)(dian)(dian)等。但是(shi)(shi)(shi)最直接的(de)(de)(de)(de)原因就(jiu)(jiu)(jiu)是(shi)(shi)(shi)高溫(wen)。我們知道(dao)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)有一個重要(yao)的(de)(de)(de)(de)參數就(jiu)(jiu)(jiu)是(shi)(shi)(shi)耐(nai)溫(wen)值，指的(de)(de)(de)(de)就(jiu)(jiu)(jiu)是(shi)(shi)(shi)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)內部(bu)(bu)電(dian)(dian)(dian)(dian)(dian)解液的(de)(de)(de)(de)沸點(dian)。當電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)的(de)(de)(de)(de)內部(bu)(bu)溫(wen)度(du)(du)達到電(dian)(dian)(dian)(dian)(dian)解液的(de)(de)(de)(de)沸點(dian)時(shi)，電(dian)(dian)(dian)(dian)(dian)解液開(kai)始(shi)沸騰，電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)內部(bu)(bu)的(de)(de)(de)(de)壓力升高，當壓力超過(guo)泄爆(bao)口的(de)(de)(de)(de)承受極限就(jiu)(jiu)(jiu)發生(sheng)了爆(bao)漿。所以(yi)說溫(wen)度(du)(du)是(shi)(shi)(shi)導(dao)致(zhi)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)爆(bao)漿的(de)(de)(de)(de)直接原因。電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)設計(ji)使(shi)用壽(shou)(shou)(shou)命(ming)(ming)(ming)大約為2萬(wan)小(xiao)時(shi)，受環(huan)境(jing)溫(wen)度(du)(du)的(de)(de)(de)(de)影(ying)響也(ye)很大。電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)的(de)(de)(de)(de)使(shi)用壽(shou)(shou)(shou)命(ming)(ming)(ming)隨溫(wen)度(du)(du)的(de)(de)(de)(de)增加而減小(xiao)，實驗證明環(huan)境(jing)溫(wen)度(du)(du)每升高10℃，電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)的(de)(de)(de)(de)壽(shou)(shou)(shou)命(ming)(ming)(ming)就(jiu)(jiu)(jiu)會(hui)減半。主(zhu)要(yao)原因就(jiu)(jiu)(jiu)是(shi)(shi)(shi)溫(wen)度(du)(du)加速化(hua)學反(fan)應而使(shi)介質隨時(shi)間(jian)退化(hua)失(shi)效，這樣電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)壽(shou)(shou)(shou)命(ming)(ming)(ming)終結(jie)。為了保證電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)的(de)(de)(de)(de)穩定性，電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)在(zai)插(cha)板(ban)前要(yao)經過(guo)長時(shi)間(jian)的(de)(de)(de)(de)高溫(wen)環(huan)境(jing)的(de)(de)(de)(de)測試。即使(shi)是(shi)(shi)(shi)在(zai)100℃，高品質的(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)也(ye)可以(yi)工作幾千個小(xiao)時(shi)。同時(shi)，我們提到的(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)的(de)(de)(de)(de)壽(shou)(shou)(shou)命(ming)(ming)(ming)是(shi)(shi)(shi)指電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)在(zai)使(shi)用過(guo)程中，電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)容(rong)(rong)(rong)(rong)(rong)量(liang)不(bu)會(hui)超過(guo)標(biao)準(zhun)(zhun)范圍變化(hua)的(de)(de)(de)(de)10%。電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)壽(shou)(shou)(shou)命(ming)(ming)(ming)指的(de)(de)(de)(de)是(shi)(shi)(shi)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)容(rong)(rong)(rong)(rong)(rong)量(liang)的(de)(de)(de)(de)問題，而不(bu)是(shi)(shi)(shi)設計(ji)壽(shou)(shou)(shou)命(ming)(ming)(ming)到達之后(hou)就(jiu)(jiu)(jiu)發生(sheng)爆(bao)漿。只是(shi)(shi)(shi)無法保證電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)的(de)(de)(de)(de)設計(ji)的(de)(de)(de)(de)容(rong)(rong)(rong)(rong)(rong)量(liang)標(biao)準(zhun)(zhun)。
所以(yi)，短時期內，正(zheng)常使(shi)用的板(ban)卡電(dian)(dian)容就發(fa)生爆漿的情況(kuang)(kuang)，這就是電(dian)(dian)容品質問題。另外(wai)，不正(zheng)常的使(shi)用情況(kuang)(kuang)也有可(ke)能發(fa)生電(dian)(dian)容爆漿的情況(kuang)(kuang)。比如熱(re)插拔電(dian)(dian)腦配件也會導(dao)致板(ban)卡局部電(dian)(dian)路電(dian)(dian)流、電(dian)(dian)壓的劇烈變化(hua)，從而(er)引發(fa)電(dian)(dian)容使(shi)用故(gu)障。
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