詳解電容在電源中所起到的作用
2019/7/1 12:46:11??????點擊：
作為(wei)無源(yuan)元件之一的電(dian)容，其作用(yong)不外乎以下幾(ji)種：
1、應用于(yu)電(dian)源電(dian)路，實現旁(pang)路、去藕、濾(lv)波和(he)儲(chu)能(neng)方面電(dian)容的作(zuo)用，下面分類詳述之：
1)濾(lv)波
濾(lv)波(bo)是電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)的(de)(de)(de)作(zuo)用中(zhong)很重要的(de)(de)(de)一部分。幾乎所有(you)(you)的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)路中(zhong)都(dou)會用到(dao)。從理論上(即假設電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)為純電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong))說，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)越(yue)(yue)大(da)(da)，阻(zu)抗(kang)越(yue)(yue)小，通(tong)(tong)過(guo)(guo)的(de)(de)(de)頻(pin)(pin)率也越(yue)(yue)高(gao)。但(dan)實際(ji)上超過(guo)(guo)1uF的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)大(da)(da)多為電(dian)(dian)(dian)(dian)(dian)(dian)(dian)解(jie)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)，有(you)(you)很大(da)(da)的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)感成份，所以頻(pin)(pin)率高(gao)后反(fan)而阻(zu)抗(kang)會增大(da)(da)。有(you)(you)時(shi)會看到(dao)有(you)(you)一個電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)量較大(da)(da)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)解(jie)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)并聯(lian)了一個小電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)，這時(shi)大(da)(da)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)通(tong)(tong)低頻(pin)(pin)，小電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)通(tong)(tong)高(gao)頻(pin)(pin)。電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)的(de)(de)(de)作(zuo)用就(jiu)是通(tong)(tong)高(gao)阻(zu)低，通(tong)(tong)高(gao)頻(pin)(pin)阻(zu)低頻(pin)(pin)。電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)越(yue)(yue)大(da)(da)低頻(pin)(pin)越(yue)(yue)容(rong)(rong)易(yi)(yi)通(tong)(tong)過(guo)(guo)，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)越(yue)(yue)大(da)(da)高(gao)頻(pin)(pin)越(yue)(yue)容(rong)(rong)易(yi)(yi)通(tong)(tong)過(guo)(guo)。具體用在濾(lv)波(bo)中(zhong),大(da)(da)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(1000uF)濾(lv)低頻(pin)(pin)，小電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(20pF)濾(lv)高(gao)頻(pin)(pin)。
曾有網友將濾波(bo)電(dian)(dian)(dian)(dian)(dian)容 比作“水(shui)(shui)塘”。由(you)于(yu)電(dian)(dian)(dian)(dian)(dian)容的(de)(de)兩(liang)端電(dian)(dian)(dian)(dian)(dian)壓(ya)不(bu)會突變，由(you)此可知，信號頻(pin)率(lv)(lv)越高則衰減(jian)越大(da)，可很形象的(de)(de)說電(dian)(dian)(dian)(dian)(dian)容像個水(shui)(shui)塘，不(bu)會因幾滴水(shui)(shui)的(de)(de)加入或(huo)蒸發而引起水(shui)(shui)量的(de)(de)變化。 它把電(dian)(dian)(dian)(dian)(dian)壓(ya)的(de)(de)變動轉(zhuan)化為電(dian)(dian)(dian)(dian)(dian)流的(de)(de)變化，頻(pin)率(lv)(lv)越高，峰值電(dian)(dian)(dian)(dian)(dian)流就越大(da)，從而緩(huan)沖了電(dian)(dian)(dian)(dian)(dian)壓(ya)。濾波(bo)就是充電(dian)(dian)(dian)(dian)(dian)，放電(dian)(dian)(dian)(dian)(dian)的(de)(de)過程。
2)旁(pang)路(lu)
旁(pang)路電(dian)(dian)容(rong)是為本地(di)器件(jian)提(ti)供能量的儲(chu)能器件(jian)，它能使穩壓器的輸出均勻化，降低負載需求。就像(xiang)小型可充電(dian)(dian)電(dian)(dian)池(chi)一樣，旁(pang)路電(dian)(dian)容(rong)能夠被充電(dian)(dian)，并向器件(jian)進行放 電(dian)(dian)。為盡量減少阻抗，旁(pang)路電(dian)(dian)容(rong)要盡量靠近負載器件(jian)的供電(dian)(dian)電(dian)(dian)源管(guan)腳和地(di)管(guan)腳。這能夠很好地(di)防止輸入值過大(da)(da)而導(dao)致的地(di)電(dian)(dian)位(wei)抬(tai)高和噪(zao)聲。地(di)彈是地(di)連接處在通過大(da)(da) 電(dian)(dian)流毛(mao)刺(ci)時的電(dian)(dian)壓降。
3)去藕
去藕，又稱解藕。從(cong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)來(lai)(lai)說，總是(shi)(shi)(shi)(shi)可(ke)以區(qu)分(fen)為驅(qu)(qu)動(dong)(dong)的源和被驅(qu)(qu)動(dong)(dong)的負載。如果負載電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)比(bi)(bi)(bi)較(jiao)大(da)，驅(qu)(qu)動(dong)(dong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)要把電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)充電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)、放電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)，才能完成信號(hao)的跳變(bian)，在上 升沿比(bi)(bi)(bi)較(jiao)陡峭的時候，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)比(bi)(bi)(bi)較(jiao)大(da)，這(zhe)樣驅(qu)(qu)動(dong)(dong)的電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)就(jiu)會(hui)吸收(shou)很大(da)的電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源電(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)路(lu)(lu)(lu)中的電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)感，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(特別是(shi)(shi)(shi)(shi)芯片(pian)管腳上的電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)感，會(hui)產(chan)生反彈)，這(zhe)種電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)相對(dui) 于(yu)正(zheng)常情況(kuang)來(lai)(lai)說實際(ji)上就(jiu)是(shi)(shi)(shi)(shi)一種噪聲(sheng)，會(hui)影響前級的正(zheng)常工作。這(zhe)就(jiu)是(shi)(shi)(shi)(shi)耦(ou)合(he)。去藕電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)就(jiu)是(shi)(shi)(shi)(shi)起(qi)到一個(ge)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池的作用，滿足驅(qu)(qu)動(dong)(dong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)的變(bian)化(hua)，避免(mian)相互間的耦(ou)合(he)干(gan)擾(rao)(rao)。將旁路(lu)(lu)(lu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)和去藕電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)結合(he)起(qi)來(lai)(lai)將更容(rong)(rong)(rong)(rong)(rong)易理解。旁路(lu)(lu)(lu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)實際(ji)也(ye)是(shi)(shi)(shi)(shi)去藕合(he)的，只是(shi)(shi)(shi)(shi)旁路(lu)(lu)(lu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)一般是(shi)(shi)(shi)(shi)指高頻旁路(lu)(lu)(lu)，也(ye)就(jiu)是(shi)(shi)(shi)(shi)給高頻的開(kai)關(guan)噪聲(sheng)提(ti)高一條低阻抗泄防 途(tu)徑。高頻旁路(lu)(lu)(lu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)一般比(bi)(bi)(bi)較(jiao)小(xiao)，根(gen)據(ju)諧振頻率一般是(shi)(shi)(shi)(shi)0.1u，0.01u等，而去耦(ou)合(he)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)一般比(bi)(bi)(bi)較(jiao)大(da)，是(shi)(shi)(shi)(shi)10uF或者(zhe)更大(da)，依據(ju)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)中分(fen)布參數，以及驅(qu)(qu)動(dong)(dong) 電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)的變(bian)化(hua)大(da)小(xiao)來(lai)(lai)確定(ding)。旁路(lu)(lu)(lu)是(shi)(shi)(shi)(shi)把輸入信號(hao)中的干(gan)擾(rao)(rao)作為濾除對(dui)象，而去耦(ou)是(shi)(shi)(shi)(shi)把輸出信號(hao)的干(gan)擾(rao)(rao)作為濾除對(dui)象，防止干(gan)擾(rao)(rao)信號(hao)返回電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源。這(zhe)應該是(shi)(shi)(shi)(shi)他們(men)的本質區(qu)別。
4)儲能
儲能型電(dian)(dian)(dian)(dian)容器(qi)通過整流器(qi)收集電(dian)(dian)(dian)(dian)荷，并(bing)將(jiang)存儲的(de)(de)能量(liang)通過變換(huan)器(qi)引線傳送(song)至電(dian)(dian)(dian)(dian)源的(de)(de)輸(shu)出端。電(dian)(dian)(dian)(dian)壓額(e)定值為40～450VDC、電(dian)(dian)(dian)(dian)容值在220～150 000uF之間的(de)(de)鋁電(dian)(dian)(dian)(dian)解電(dian)(dian)(dian)(dian)容器(qi)(如EPCOS公司的(de)(de) B43504或B43505)是較為常(chang)用(yong)的(de)(de)。根(gen)據不同的(de)(de)電(dian)(dian)(dian)(dian)源要(yao)求，器(qi)件有(you)時會采(cai)用(yong)串聯(lian)、并(bing)聯(lian)或其組(zu)合的(de)(de)形式， 對于功率級超過10KW的(de)(de)電(dian)(dian)(dian)(dian)源，通常(chang)采(cai)用(yong)體(ti)(ti)積較大的(de)(de)罐形螺旋端子電(dian)(dian)(dian)(dian)容器(qi)。
2、應(ying)用于信號電路，主要完成耦合、振(zhen)蕩/同(tong)步及時間常數(shu)的作用：
1)耦合
舉個(ge)例子來講，晶體管放大器發射極有一(yi)個(ge)自給偏壓(ya)電(dian)(dian)(dian)阻，它同時又(you)使信號(hao)產生(sheng)(sheng)壓(ya)降(jiang)反饋到輸入端(duan)形成了輸入輸出信號(hao)耦合，這個(ge)電(dian)(dian)(dian)阻就(jiu)是產生(sheng)(sheng)了耦合的(de)元(yuan)件，如果在這個(ge)電(dian)(dian)(dian)阻兩端(duan)并(bing)聯一(yi)個(ge)電(dian)(dian)(dian)容(rong)，由于適當容(rong)量的(de)電(dian)(dian)(dian)容(rong)器對交流信號(hao)較小的(de)阻抗(kang),這樣就(jiu)減小了電(dian)(dian)(dian)阻產生(sheng)(sheng)的(de)耦合效應，故稱此(ci)電(dian)(dian)(dian)容(rong)為去耦電(dian)(dian)(dian)容(rong)。
2)振(zhen)蕩(dang)/同步
包括RC、LC振蕩器及晶體的負載(zai)電容都屬于這(zhe)一(yi)范疇。
3)時(shi)間常數
這(zhe)就(jiu)是常見的(de) R、C 串聯構成的(de)積(ji)分(fen)電(dian)(dian)(dian)路。當輸入(ru)信號電(dian)(dian)(dian)壓加在輸入(ru)端時，電(dian)(dian)(dian)容(rong)(C)上(shang)的(de)電(dian)(dian)(dian)壓逐漸上(shang)升。而(er)其充電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)則隨著電(dian)(dian)(dian)壓的(de)上(shang)升而(er)減小。電(dian)(dian)(dian)流(liu)通過電(dian)(dian)(dian)阻(R)、電(dian)(dian)(dian)容(rong)(C)的(de)特性通過下面的(de)公(gong)式(shi)描述：
i = (V/R)e-(t/CR)
我們知(zhi)道(dao)了電容(rong)的作用以后下面來(lai)談談電容(rong)在使用中的注意事(shi)項
A. 什么是好電容。
1.電容容量越(yue)大越(yue)好。
很多人在(zai)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)的(de)(de)(de)(de)替換中往(wang)往(wang)愛用大(da)(da)容(rong)(rong)(rong)量的(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)。我(wo)們知道(dao)雖然電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)越大(da)(da)，為(wei)IC提供(gong)的(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)流(liu)補(bu)償(chang)的(de)(de)(de)(de)能(neng)(neng)力越強(qiang)。且不說(shuo)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)容(rong)(rong)(rong)量的(de)(de)(de)(de)增大(da)(da)帶來(lai)的(de)(de)(de)(de)體積(ji)變(bian)大(da)(da)，增加成(cheng)本的(de)(de)(de)(de)同時(shi)還影響空氣流(liu)動和散熱。關鍵(jian)在(zai)于電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)上存在(zai)寄生電(dian)(dian)(dian)(dian)(dian)感(gan)，電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)放電(dian)(dian)(dian)(dian)(dian)回(hui)路(lu)會在(zai)某個頻(pin)(pin)點上發生諧(xie)振(zhen)。在(zai)諧(xie)振(zhen)點，電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)的(de)(de)(de)(de)阻抗(kang)小。因此放電(dian)(dian)(dian)(dian)(dian)回(hui)路(lu)的(de)(de)(de)(de)阻抗(kang)最小，補(bu)充能(neng)(neng)量的(de)(de)(de)(de)效果也最好(hao)。但當頻(pin)(pin)率超過諧(xie)振(zhen)點時(shi)，放電(dian)(dian)(dian)(dian)(dian)回(hui)路(lu)的(de)(de)(de)(de)阻抗(kang)開始增加，電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)提供(gong)電(dian)(dian)(dian)(dian)(dian)流(liu)能(neng)(neng)力便開始下降。電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)的(de)(de)(de)(de)容(rong)(rong)(rong)值(zhi)越大(da)(da)，諧(xie)振(zhen)頻(pin)(pin)率越低，電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)能(neng)(neng)有(you)(you)效補(bu)償(chang)電(dian)(dian)(dian)(dian)(dian)流(liu)的(de)(de)(de)(de)頻(pin)(pin)率范圍也越小。從保(bao)證電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)提供(gong)高(gao)頻(pin)(pin)電(dian)(dian)(dian)(dian)(dian)流(liu)的(de)(de)(de)(de)能(neng)(neng)力的(de)(de)(de)(de)角度(du)來(lai)說(shuo)，電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)越大(da)(da)越好(hao)的(de)(de)(de)(de)觀(guan)點是錯誤的(de)(de)(de)(de)，一般的(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)路(lu)設計中都(dou)有(you)(you)一個參(can)考值(zhi)的(de)(de)(de)(de)。
2.同樣(yang)容量的電(dian)容，并聯(lian)越多(duo)的小電(dian)容越好
耐(nai)壓(ya)值(zhi)、耐(nai)溫值(zhi)、容值(zhi)、ESR(等(deng)效(xiao)電(dian)(dian)(dian)阻(zu))等(deng)是(shi)電(dian)(dian)(dian)容的(de)幾個(ge)重(zhong)要(yao)參數，對于ESR自然是(shi)越(yue)低(di)越(yue)好。ESR與電(dian)(dian)(dian)容的(de)容量、頻率、電(dian)(dian)(dian)壓(ya)、溫度等(deng)都(dou)有關(guan)系。當電(dian)(dian)(dian)壓(ya)固定時(shi)候，容量越(yue)大，ESR越(yue)低(di)。在板卡設計中采用多(duo)個(ge)小(xiao)(xiao)電(dian)(dian)(dian)容并(bing)(bing)連多(duo)是(shi)出與PCB空間的(de)限制(zhi)，這樣有的(de)人就認(ren)為(wei)，越(yue)多(duo)的(de)并(bing)(bing)聯小(xiao)(xiao)電(dian)(dian)(dian)阻(zu)，ESR越(yue)低(di)，效(xiao)果越(yue)好。理論上(shang)是(shi)如(ru)此，但(dan)是(shi)要(yao)考慮(lv)到電(dian)(dian)(dian)容接腳焊(han)點的(de)阻(zu)抗，采用多(duo)個(ge)小(xiao)(xiao)電(dian)(dian)(dian)容并(bing)(bing)聯，效(xiao)果并(bing)(bing)不一定突(tu)出。
3.ESR越低，效果越好。
結合我們上面的(de)(de)(de)(de)提高的(de)(de)(de)(de)供電(dian)(dian)(dian)電(dian)(dian)(dian)路來說，對(dui)于輸(shu)入(ru)電(dian)(dian)(dian)容來說，輸(shu)入(ru)電(dian)(dian)(dian)容的(de)(de)(de)(de)容量(liang)(liang)要(yao)大一(yi)(yi)(yi)點。相對(dui)容量(liang)(liang)的(de)(de)(de)(de)要(yao)求(qiu)，對(dui)ESR的(de)(de)(de)(de)要(yao)求(qiu)可以(yi)適當(dang)的(de)(de)(de)(de)降(jiang)低(di)。因為輸(shu)入(ru)電(dian)(dian)(dian)容主(zhu)要(yao)是(shi)耐(nai)壓，其次是(shi)吸收MOSFET的(de)(de)(de)(de)開關脈沖(chong)。對(dui)于輸(shu)出電(dian)(dian)(dian)容來說，耐(nai)壓的(de)(de)(de)(de)要(yao)求(qiu)和容量(liang)(liang)可以(yi)適當(dang)的(de)(de)(de)(de)降(jiang)低(di)一(yi)(yi)(yi)點。ESR的(de)(de)(de)(de)要(yao)求(qiu)則高一(yi)(yi)(yi)點，因為這(zhe)里要(yao)保證的(de)(de)(de)(de)是(shi)足夠的(de)(de)(de)(de)電(dian)(dian)(dian)流通過量(liang)(liang)。但(dan)這(zhe)里要(yao)注意的(de)(de)(de)(de)是(shi)ESR并不是(shi)越低(di)越好，低(di)ESR電(dian)(dian)(dian)容會引起開關電(dian)(dian)(dian)路振(zhen)蕩。而消振(zhen)電(dian)(dian)(dian)路復雜同時(shi)會導(dao)(dao)致成(cheng)本的(de)(de)(de)(de)增加(jia)。板卡設計中，這(zhe)里一(yi)(yi)(yi)般(ban)有一(yi)(yi)(yi)個參(can)考值，此作為元件(jian)選用參(can)數，避免消振(zhen)電(dian)(dian)(dian)路而導(dao)(dao)致成(cheng)本的(de)(de)(de)(de)增加(jia)。
4.好電容代表著高品質(zhi)。
“唯電容(rong)論”曾經盛極一(yi)時，一(yi)些廠(chang)商和媒(mei)體也(ye)刻意(yi)(yi)的把(ba)這(zhe)個(ge)事情(qing)做成(cheng)一(yi)個(ge)賣點。在板卡設計中(zhong)，電路設計水平是關鍵(jian)。和有(you)的廠(chang)商可(ke)以用(yong)(yong)兩相(xiang)供(gong)電做出(chu)比一(yi)些廠(chang)商采(cai)(cai)用(yong)(yong)四相(xiang)供(gong)電更穩定(ding)的產品一(yi)樣(yang)，一(yi)味(wei)的采(cai)(cai)用(yong)(yong)高(gao)價(jia)電容(rong)，不一(yi)定(ding)能做出(chu)好產品。衡量(liang)一(yi)個(ge)產品，一(yi)定(ding)要全方位多角度的去考慮(lv)，切不可(ke)把(ba)電容(rong)的作用(yong)(yong)有(you)意(yi)(yi)無(wu)意(yi)(yi)的夸大。
B. 電容(rong)爆漿之面面談(tan)
爆(bao)漿的種(zhong)類：
分兩類，輸入電(dian)容爆(bao)漿(jiang)和輸出電(dian)容爆(bao)漿(jiang)。
對于(yu)輸(shu)(shu)入(ru)(ru)電(dian)(dian)容(rong)來說(shuo)，就是我是說(shuo)的(de)(de)C1，C1對由電(dian)(dian)源接收(shou)到的(de)(de)電(dian)(dian)流(liu)(liu)進行過(guo)(guo)濾。輸(shu)(shu)入(ru)(ru)電(dian)(dian)容(rong)爆(bao)漿(jiang)和電(dian)(dian)源輸(shu)(shu)入(ru)(ru)電(dian)(dian)流(liu)(liu)的(de)(de)品質有關。過(guo)(guo)多的(de)(de)毛刺電(dian)(dian)壓，峰(feng)值電(dian)(dian)壓過(guo)(guo)高，電(dian)(dian)流(liu)(liu)不穩定等都(dou)使電(dian)(dian)容(rong)過(guo)(guo)于(yu)充放電(dian)(dian)過(guo)(guo)于(yu)頻繁(fan)，長時間處于(yu)這類工作環(huan)境下的(de)(de)電(dian)(dian)容(rong)，內(nei)部(bu)溫度升高很快。超過(guo)(guo)泄爆(bao)口的(de)(de)承受極限就會發(fa)生爆(bao)漿(jiang)。
對(dui)(dui)于輸(shu)出(chu)電容(rong)(rong)來說(shuo)，就我說(shuo)的C2，對(dui)(dui)經電源模塊(kuai)調(diao)整后(hou)的電流進行(xing)濾波。此處電流經過(guo)一(yi)次過(guo)濾，比較(jiao)平穩，發生(sheng)爆漿的可能性相對(dui)(dui)來說(shuo)小了不少。但(dan)如果環境溫(wen)度過(guo)高，電容(rong)(rong)同樣容(rong)(rong)易發生(sheng)爆漿。爆，報(bao)也(ye)。采用垃圾東西自然要爆，報(bao)應(ying)啊。欲(yu)知過(guo)去因(yin)者(zhe)，見其(qi)現在(zai)果;欲(yu)知未來果者(zhe)，見其(qi)現在(zai)因(yin)。
電解電容爆漿(jiang)的原因：
電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)(rong)爆漿(jiang)的(de)(de)(de)(de)(de)(de)原(yuan)因有很多，比如電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流大于允許的(de)(de)(de)(de)(de)(de)穩波電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流、使(shi)用(yong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)超出工作電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)、逆向電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)、頻繁的(de)(de)(de)(de)(de)(de)充放電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)等。但是(shi)最直接的(de)(de)(de)(de)(de)(de)原(yuan)因就是(shi)高(gao)溫(wen)(wen)。我們(men)知(zhi)道(dao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)(rong)有一(yi)個(ge)重要(yao)的(de)(de)(de)(de)(de)(de)參數就是(shi)耐溫(wen)(wen)值(zhi)，指(zhi)的(de)(de)(de)(de)(de)(de)就是(shi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)(rong)內部(bu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)解(jie)液的(de)(de)(de)(de)(de)(de)沸點。當電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)(rong)的(de)(de)(de)(de)(de)(de)內部(bu)溫(wen)(wen)度(du)(du)達(da)(da)到(dao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)解(jie)液的(de)(de)(de)(de)(de)(de)沸點時，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)解(jie)液開始沸騰，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)(rong)內部(bu)的(de)(de)(de)(de)(de)(de)壓(ya)力升(sheng)高(gao)，當壓(ya)力超過(guo)泄爆口的(de)(de)(de)(de)(de)(de)承受極限就發(fa)生了爆漿(jiang)。所以(yi)說溫(wen)(wen)度(du)(du)是(shi)導致(zhi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)(rong)爆漿(jiang)的(de)(de)(de)(de)(de)(de)直接原(yuan)因。電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)(rong)設計(ji)(ji)使(shi)用(yong)壽(shou)命(ming)大約為(wei)2萬小時，受環(huan)(huan)境溫(wen)(wen)度(du)(du)的(de)(de)(de)(de)(de)(de)影響也很大。電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)(rong)的(de)(de)(de)(de)(de)(de)使(shi)用(yong)壽(shou)命(ming)隨溫(wen)(wen)度(du)(du)的(de)(de)(de)(de)(de)(de)增加而減小，實驗證(zheng)明環(huan)(huan)境溫(wen)(wen)度(du)(du)每升(sheng)高(gao)10℃，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)(rong)的(de)(de)(de)(de)(de)(de)壽(shou)命(ming)就會減半。主要(yao)原(yuan)因就是(shi)溫(wen)(wen)度(du)(du)加速(su)化(hua)學反應(ying)而使(shi)介質隨時間退化(hua)失效，這樣電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)(rong)壽(shou)命(ming)終結。為(wei)了保證(zheng)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)(rong)的(de)(de)(de)(de)(de)(de)穩定性(xing)，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)(rong)在(zai)插(cha)板前要(yao)經過(guo)長時間的(de)(de)(de)(de)(de)(de)高(gao)溫(wen)(wen)環(huan)(huan)境的(de)(de)(de)(de)(de)(de)測試。即使(shi)是(shi)在(zai)100℃，高(gao)品質的(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)(rong)也可以(yi)工作幾千個(ge)小時。同時，我們(men)提到(dao)的(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)(rong)的(de)(de)(de)(de)(de)(de)壽(shou)命(ming)是(shi)指(zhi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)(rong)在(zai)使(shi)用(yong)過(guo)程(cheng)中，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)(rong)容(rong)(rong)(rong)(rong)(rong)(rong)(rong)量不會超過(guo)標準(zhun)范圍變化(hua)的(de)(de)(de)(de)(de)(de)10%。電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)(rong)壽(shou)命(ming)指(zhi)的(de)(de)(de)(de)(de)(de)是(shi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)(rong)容(rong)(rong)(rong)(rong)(rong)(rong)(rong)量的(de)(de)(de)(de)(de)(de)問題，而不是(shi)設計(ji)(ji)壽(shou)命(ming)到(dao)達(da)(da)之后(hou)就發(fa)生爆漿(jiang)。只是(shi)無法保證(zheng)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)(rong)的(de)(de)(de)(de)(de)(de)設計(ji)(ji)的(de)(de)(de)(de)(de)(de)容(rong)(rong)(rong)(rong)(rong)(rong)(rong)量標準(zhun)。
所以，短時期內，正(zheng)常使(shi)用的板(ban)卡電(dian)(dian)(dian)容(rong)就(jiu)發(fa)生爆漿的情(qing)(qing)況，這就(jiu)是電(dian)(dian)(dian)容(rong)品質問題。另外，不正(zheng)常的使(shi)用情(qing)(qing)況也(ye)(ye)有可能發(fa)生電(dian)(dian)(dian)容(rong)爆漿的情(qing)(qing)況。比(bi)如熱插拔電(dian)(dian)(dian)腦配件也(ye)(ye)會導致板(ban)卡局部電(dian)(dian)(dian)路(lu)電(dian)(dian)(dian)流、電(dian)(dian)(dian)壓(ya)的劇烈變(bian)化，從而引(yin)發(fa)電(dian)(dian)(dian)容(rong)使(shi)用故(gu)障。
1、應用于(yu)電(dian)源電(dian)路，實現旁(pang)路、去藕、濾(lv)波和(he)儲(chu)能(neng)方面電(dian)容的作(zuo)用，下面分類詳述之：
1)濾(lv)波
濾(lv)波(bo)是電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)的(de)(de)(de)作(zuo)用中(zhong)很重要的(de)(de)(de)一部分。幾乎所有(you)(you)的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)路中(zhong)都(dou)會用到(dao)。從理論上(即假設電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)為純電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong))說，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)越(yue)(yue)大(da)(da)，阻(zu)抗(kang)越(yue)(yue)小，通(tong)(tong)過(guo)(guo)的(de)(de)(de)頻(pin)(pin)率也越(yue)(yue)高(gao)。但(dan)實際(ji)上超過(guo)(guo)1uF的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)大(da)(da)多為電(dian)(dian)(dian)(dian)(dian)(dian)(dian)解(jie)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)，有(you)(you)很大(da)(da)的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)感成份，所以頻(pin)(pin)率高(gao)后反(fan)而阻(zu)抗(kang)會增大(da)(da)。有(you)(you)時(shi)會看到(dao)有(you)(you)一個電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)量較大(da)(da)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)解(jie)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)并聯(lian)了一個小電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)，這時(shi)大(da)(da)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)通(tong)(tong)低頻(pin)(pin)，小電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)通(tong)(tong)高(gao)頻(pin)(pin)。電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)的(de)(de)(de)作(zuo)用就(jiu)是通(tong)(tong)高(gao)阻(zu)低，通(tong)(tong)高(gao)頻(pin)(pin)阻(zu)低頻(pin)(pin)。電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)越(yue)(yue)大(da)(da)低頻(pin)(pin)越(yue)(yue)容(rong)(rong)易(yi)(yi)通(tong)(tong)過(guo)(guo)，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)越(yue)(yue)大(da)(da)高(gao)頻(pin)(pin)越(yue)(yue)容(rong)(rong)易(yi)(yi)通(tong)(tong)過(guo)(guo)。具體用在濾(lv)波(bo)中(zhong),大(da)(da)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(1000uF)濾(lv)低頻(pin)(pin)，小電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(20pF)濾(lv)高(gao)頻(pin)(pin)。
曾有網友將濾波(bo)電(dian)(dian)(dian)(dian)(dian)容 比作“水(shui)(shui)塘”。由(you)于(yu)電(dian)(dian)(dian)(dian)(dian)容的(de)(de)兩(liang)端電(dian)(dian)(dian)(dian)(dian)壓(ya)不(bu)會突變，由(you)此可知，信號頻(pin)率(lv)(lv)越高則衰減(jian)越大(da)，可很形象的(de)(de)說電(dian)(dian)(dian)(dian)(dian)容像個水(shui)(shui)塘，不(bu)會因幾滴水(shui)(shui)的(de)(de)加入或(huo)蒸發而引起水(shui)(shui)量的(de)(de)變化。 它把電(dian)(dian)(dian)(dian)(dian)壓(ya)的(de)(de)變動轉(zhuan)化為電(dian)(dian)(dian)(dian)(dian)流的(de)(de)變化，頻(pin)率(lv)(lv)越高，峰值電(dian)(dian)(dian)(dian)(dian)流就越大(da)，從而緩(huan)沖了電(dian)(dian)(dian)(dian)(dian)壓(ya)。濾波(bo)就是充電(dian)(dian)(dian)(dian)(dian)，放電(dian)(dian)(dian)(dian)(dian)的(de)(de)過程。
2)旁(pang)路(lu)
旁(pang)路電(dian)(dian)容(rong)是為本地(di)器件(jian)提(ti)供能量的儲(chu)能器件(jian)，它能使穩壓器的輸出均勻化，降低負載需求。就像(xiang)小型可充電(dian)(dian)電(dian)(dian)池(chi)一樣，旁(pang)路電(dian)(dian)容(rong)能夠被充電(dian)(dian)，并向器件(jian)進行放 電(dian)(dian)。為盡量減少阻抗，旁(pang)路電(dian)(dian)容(rong)要盡量靠近負載器件(jian)的供電(dian)(dian)電(dian)(dian)源管(guan)腳和地(di)管(guan)腳。這能夠很好地(di)防止輸入值過大(da)(da)而導(dao)致的地(di)電(dian)(dian)位(wei)抬(tai)高和噪(zao)聲。地(di)彈是地(di)連接處在通過大(da)(da) 電(dian)(dian)流毛(mao)刺(ci)時的電(dian)(dian)壓降。
3)去藕
去藕，又稱解藕。從(cong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)來(lai)(lai)說，總是(shi)(shi)(shi)(shi)可(ke)以區(qu)分(fen)為驅(qu)(qu)動(dong)(dong)的源和被驅(qu)(qu)動(dong)(dong)的負載。如果負載電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)比(bi)(bi)(bi)較(jiao)大(da)，驅(qu)(qu)動(dong)(dong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)要把電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)充電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)、放電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)，才能完成信號(hao)的跳變(bian)，在上 升沿比(bi)(bi)(bi)較(jiao)陡峭的時候，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)比(bi)(bi)(bi)較(jiao)大(da)，這(zhe)樣驅(qu)(qu)動(dong)(dong)的電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)就(jiu)會(hui)吸收(shou)很大(da)的電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源電(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)路(lu)(lu)(lu)中的電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)感，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(特別是(shi)(shi)(shi)(shi)芯片(pian)管腳上的電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)感，會(hui)產(chan)生反彈)，這(zhe)種電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)相對(dui) 于(yu)正(zheng)常情況(kuang)來(lai)(lai)說實際(ji)上就(jiu)是(shi)(shi)(shi)(shi)一種噪聲(sheng)，會(hui)影響前級的正(zheng)常工作。這(zhe)就(jiu)是(shi)(shi)(shi)(shi)耦(ou)合(he)。去藕電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)就(jiu)是(shi)(shi)(shi)(shi)起(qi)到一個(ge)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池的作用，滿足驅(qu)(qu)動(dong)(dong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)的變(bian)化(hua)，避免(mian)相互間的耦(ou)合(he)干(gan)擾(rao)(rao)。將旁路(lu)(lu)(lu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)和去藕電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)結合(he)起(qi)來(lai)(lai)將更容(rong)(rong)(rong)(rong)(rong)易理解。旁路(lu)(lu)(lu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)實際(ji)也(ye)是(shi)(shi)(shi)(shi)去藕合(he)的，只是(shi)(shi)(shi)(shi)旁路(lu)(lu)(lu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)一般是(shi)(shi)(shi)(shi)指高頻旁路(lu)(lu)(lu)，也(ye)就(jiu)是(shi)(shi)(shi)(shi)給高頻的開(kai)關(guan)噪聲(sheng)提(ti)高一條低阻抗泄防 途(tu)徑。高頻旁路(lu)(lu)(lu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)一般比(bi)(bi)(bi)較(jiao)小(xiao)，根(gen)據(ju)諧振頻率一般是(shi)(shi)(shi)(shi)0.1u，0.01u等，而去耦(ou)合(he)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)一般比(bi)(bi)(bi)較(jiao)大(da)，是(shi)(shi)(shi)(shi)10uF或者(zhe)更大(da)，依據(ju)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)中分(fen)布參數，以及驅(qu)(qu)動(dong)(dong) 電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)的變(bian)化(hua)大(da)小(xiao)來(lai)(lai)確定(ding)。旁路(lu)(lu)(lu)是(shi)(shi)(shi)(shi)把輸入信號(hao)中的干(gan)擾(rao)(rao)作為濾除對(dui)象，而去耦(ou)是(shi)(shi)(shi)(shi)把輸出信號(hao)的干(gan)擾(rao)(rao)作為濾除對(dui)象，防止干(gan)擾(rao)(rao)信號(hao)返回電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源。這(zhe)應該是(shi)(shi)(shi)(shi)他們(men)的本質區(qu)別。
4)儲能
儲能型電(dian)(dian)(dian)(dian)容器(qi)通過整流器(qi)收集電(dian)(dian)(dian)(dian)荷，并(bing)將(jiang)存儲的(de)(de)能量(liang)通過變換(huan)器(qi)引線傳送(song)至電(dian)(dian)(dian)(dian)源的(de)(de)輸(shu)出端。電(dian)(dian)(dian)(dian)壓額(e)定值為40～450VDC、電(dian)(dian)(dian)(dian)容值在220～150 000uF之間的(de)(de)鋁電(dian)(dian)(dian)(dian)解電(dian)(dian)(dian)(dian)容器(qi)(如EPCOS公司的(de)(de) B43504或B43505)是較為常(chang)用(yong)的(de)(de)。根(gen)據不同的(de)(de)電(dian)(dian)(dian)(dian)源要(yao)求，器(qi)件有(you)時會采(cai)用(yong)串聯(lian)、并(bing)聯(lian)或其組(zu)合的(de)(de)形式， 對于功率級超過10KW的(de)(de)電(dian)(dian)(dian)(dian)源，通常(chang)采(cai)用(yong)體(ti)(ti)積較大的(de)(de)罐形螺旋端子電(dian)(dian)(dian)(dian)容器(qi)。
2、應(ying)用于信號電路，主要完成耦合、振(zhen)蕩/同(tong)步及時間常數(shu)的作用：
1)耦合
舉個(ge)例子來講，晶體管放大器發射極有一(yi)個(ge)自給偏壓(ya)電(dian)(dian)(dian)阻，它同時又(you)使信號(hao)產生(sheng)(sheng)壓(ya)降(jiang)反饋到輸入端(duan)形成了輸入輸出信號(hao)耦合，這個(ge)電(dian)(dian)(dian)阻就(jiu)是產生(sheng)(sheng)了耦合的(de)元(yuan)件，如果在這個(ge)電(dian)(dian)(dian)阻兩端(duan)并(bing)聯一(yi)個(ge)電(dian)(dian)(dian)容(rong)，由于適當容(rong)量的(de)電(dian)(dian)(dian)容(rong)器對交流信號(hao)較小的(de)阻抗(kang),這樣就(jiu)減小了電(dian)(dian)(dian)阻產生(sheng)(sheng)的(de)耦合效應，故稱此(ci)電(dian)(dian)(dian)容(rong)為去耦電(dian)(dian)(dian)容(rong)。
2)振(zhen)蕩(dang)/同步
包括RC、LC振蕩器及晶體的負載(zai)電容都屬于這(zhe)一(yi)范疇。
3)時(shi)間常數
這(zhe)就(jiu)是常見的(de) R、C 串聯構成的(de)積(ji)分(fen)電(dian)(dian)(dian)路。當輸入(ru)信號電(dian)(dian)(dian)壓加在輸入(ru)端時，電(dian)(dian)(dian)容(rong)(C)上(shang)的(de)電(dian)(dian)(dian)壓逐漸上(shang)升。而(er)其充電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)則隨著電(dian)(dian)(dian)壓的(de)上(shang)升而(er)減小。電(dian)(dian)(dian)流(liu)通過電(dian)(dian)(dian)阻(R)、電(dian)(dian)(dian)容(rong)(C)的(de)特性通過下面的(de)公(gong)式(shi)描述：
i = (V/R)e-(t/CR)
我們知(zhi)道(dao)了電容(rong)的作用以后下面來(lai)談談電容(rong)在使用中的注意事(shi)項
A. 什么是好電容。
1.電容容量越(yue)大越(yue)好。
很多人在(zai)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)的(de)(de)(de)(de)替換中往(wang)往(wang)愛用大(da)(da)容(rong)(rong)(rong)量的(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)。我(wo)們知道(dao)雖然電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)越大(da)(da)，為(wei)IC提供(gong)的(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)流(liu)補(bu)償(chang)的(de)(de)(de)(de)能(neng)(neng)力越強(qiang)。且不說(shuo)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)容(rong)(rong)(rong)量的(de)(de)(de)(de)增大(da)(da)帶來(lai)的(de)(de)(de)(de)體積(ji)變(bian)大(da)(da)，增加成(cheng)本的(de)(de)(de)(de)同時(shi)還影響空氣流(liu)動和散熱。關鍵(jian)在(zai)于電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)上存在(zai)寄生電(dian)(dian)(dian)(dian)(dian)感(gan)，電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)放電(dian)(dian)(dian)(dian)(dian)回(hui)路(lu)會在(zai)某個頻(pin)(pin)點上發生諧(xie)振(zhen)。在(zai)諧(xie)振(zhen)點，電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)的(de)(de)(de)(de)阻抗(kang)小。因此放電(dian)(dian)(dian)(dian)(dian)回(hui)路(lu)的(de)(de)(de)(de)阻抗(kang)最小，補(bu)充能(neng)(neng)量的(de)(de)(de)(de)效果也最好(hao)。但當頻(pin)(pin)率超過諧(xie)振(zhen)點時(shi)，放電(dian)(dian)(dian)(dian)(dian)回(hui)路(lu)的(de)(de)(de)(de)阻抗(kang)開始增加，電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)提供(gong)電(dian)(dian)(dian)(dian)(dian)流(liu)能(neng)(neng)力便開始下降。電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)的(de)(de)(de)(de)容(rong)(rong)(rong)值(zhi)越大(da)(da)，諧(xie)振(zhen)頻(pin)(pin)率越低，電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)能(neng)(neng)有(you)(you)效補(bu)償(chang)電(dian)(dian)(dian)(dian)(dian)流(liu)的(de)(de)(de)(de)頻(pin)(pin)率范圍也越小。從保(bao)證電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)提供(gong)高(gao)頻(pin)(pin)電(dian)(dian)(dian)(dian)(dian)流(liu)的(de)(de)(de)(de)能(neng)(neng)力的(de)(de)(de)(de)角度(du)來(lai)說(shuo)，電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)越大(da)(da)越好(hao)的(de)(de)(de)(de)觀(guan)點是錯誤的(de)(de)(de)(de)，一般的(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)路(lu)設計中都(dou)有(you)(you)一個參(can)考值(zhi)的(de)(de)(de)(de)。
2.同樣(yang)容量的電(dian)容，并聯(lian)越多(duo)的小電(dian)容越好
耐(nai)壓(ya)值(zhi)、耐(nai)溫值(zhi)、容值(zhi)、ESR(等(deng)效(xiao)電(dian)(dian)(dian)阻(zu))等(deng)是(shi)電(dian)(dian)(dian)容的(de)幾個(ge)重(zhong)要(yao)參數，對于ESR自然是(shi)越(yue)低(di)越(yue)好。ESR與電(dian)(dian)(dian)容的(de)容量、頻率、電(dian)(dian)(dian)壓(ya)、溫度等(deng)都(dou)有關(guan)系。當電(dian)(dian)(dian)壓(ya)固定時(shi)候，容量越(yue)大，ESR越(yue)低(di)。在板卡設計中采用多(duo)個(ge)小(xiao)(xiao)電(dian)(dian)(dian)容并(bing)(bing)連多(duo)是(shi)出與PCB空間的(de)限制(zhi)，這樣有的(de)人就認(ren)為(wei)，越(yue)多(duo)的(de)并(bing)(bing)聯小(xiao)(xiao)電(dian)(dian)(dian)阻(zu)，ESR越(yue)低(di)，效(xiao)果越(yue)好。理論上(shang)是(shi)如(ru)此，但(dan)是(shi)要(yao)考慮(lv)到電(dian)(dian)(dian)容接腳焊(han)點的(de)阻(zu)抗，采用多(duo)個(ge)小(xiao)(xiao)電(dian)(dian)(dian)容并(bing)(bing)聯，效(xiao)果并(bing)(bing)不一定突(tu)出。
3.ESR越低，效果越好。
結合我們上面的(de)(de)(de)(de)提高的(de)(de)(de)(de)供電(dian)(dian)(dian)電(dian)(dian)(dian)路來說，對(dui)于輸(shu)入(ru)電(dian)(dian)(dian)容來說，輸(shu)入(ru)電(dian)(dian)(dian)容的(de)(de)(de)(de)容量(liang)(liang)要(yao)大一(yi)(yi)(yi)點。相對(dui)容量(liang)(liang)的(de)(de)(de)(de)要(yao)求(qiu)，對(dui)ESR的(de)(de)(de)(de)要(yao)求(qiu)可以(yi)適當(dang)的(de)(de)(de)(de)降(jiang)低(di)。因為輸(shu)入(ru)電(dian)(dian)(dian)容主(zhu)要(yao)是(shi)耐(nai)壓，其次是(shi)吸收MOSFET的(de)(de)(de)(de)開關脈沖(chong)。對(dui)于輸(shu)出電(dian)(dian)(dian)容來說，耐(nai)壓的(de)(de)(de)(de)要(yao)求(qiu)和容量(liang)(liang)可以(yi)適當(dang)的(de)(de)(de)(de)降(jiang)低(di)一(yi)(yi)(yi)點。ESR的(de)(de)(de)(de)要(yao)求(qiu)則高一(yi)(yi)(yi)點，因為這(zhe)里要(yao)保證的(de)(de)(de)(de)是(shi)足夠的(de)(de)(de)(de)電(dian)(dian)(dian)流通過量(liang)(liang)。但(dan)這(zhe)里要(yao)注意的(de)(de)(de)(de)是(shi)ESR并不是(shi)越低(di)越好，低(di)ESR電(dian)(dian)(dian)容會引起開關電(dian)(dian)(dian)路振(zhen)蕩。而消振(zhen)電(dian)(dian)(dian)路復雜同時(shi)會導(dao)(dao)致成(cheng)本的(de)(de)(de)(de)增加(jia)。板卡設計中，這(zhe)里一(yi)(yi)(yi)般(ban)有一(yi)(yi)(yi)個參(can)考值，此作為元件(jian)選用參(can)數，避免消振(zhen)電(dian)(dian)(dian)路而導(dao)(dao)致成(cheng)本的(de)(de)(de)(de)增加(jia)。
4.好電容代表著高品質(zhi)。
“唯電容(rong)論”曾經盛極一(yi)時，一(yi)些廠(chang)商和媒(mei)體也(ye)刻意(yi)(yi)的把(ba)這(zhe)個(ge)事情(qing)做成(cheng)一(yi)個(ge)賣點。在板卡設計中(zhong)，電路設計水平是關鍵(jian)。和有(you)的廠(chang)商可(ke)以用(yong)(yong)兩相(xiang)供(gong)電做出(chu)比一(yi)些廠(chang)商采(cai)(cai)用(yong)(yong)四相(xiang)供(gong)電更穩定(ding)的產品一(yi)樣(yang)，一(yi)味(wei)的采(cai)(cai)用(yong)(yong)高(gao)價(jia)電容(rong)，不一(yi)定(ding)能做出(chu)好產品。衡量(liang)一(yi)個(ge)產品，一(yi)定(ding)要全方位多角度的去考慮(lv)，切不可(ke)把(ba)電容(rong)的作用(yong)(yong)有(you)意(yi)(yi)無(wu)意(yi)(yi)的夸大。
B. 電容(rong)爆漿之面面談(tan)
爆(bao)漿的種(zhong)類：
分兩類，輸入電(dian)容爆(bao)漿(jiang)和輸出電(dian)容爆(bao)漿(jiang)。
對于(yu)輸(shu)(shu)入(ru)(ru)電(dian)(dian)容(rong)來說(shuo)，就是我是說(shuo)的(de)(de)C1，C1對由電(dian)(dian)源接收(shou)到的(de)(de)電(dian)(dian)流(liu)(liu)進行過(guo)(guo)濾。輸(shu)(shu)入(ru)(ru)電(dian)(dian)容(rong)爆(bao)漿(jiang)和電(dian)(dian)源輸(shu)(shu)入(ru)(ru)電(dian)(dian)流(liu)(liu)的(de)(de)品質有關。過(guo)(guo)多的(de)(de)毛刺電(dian)(dian)壓，峰(feng)值電(dian)(dian)壓過(guo)(guo)高，電(dian)(dian)流(liu)(liu)不穩定等都(dou)使電(dian)(dian)容(rong)過(guo)(guo)于(yu)充放電(dian)(dian)過(guo)(guo)于(yu)頻繁(fan)，長時間處于(yu)這類工作環(huan)境下的(de)(de)電(dian)(dian)容(rong)，內(nei)部(bu)溫度升高很快。超過(guo)(guo)泄爆(bao)口的(de)(de)承受極限就會發(fa)生爆(bao)漿(jiang)。
對(dui)(dui)于輸(shu)出(chu)電容(rong)(rong)來說(shuo)，就我說(shuo)的C2，對(dui)(dui)經電源模塊(kuai)調(diao)整后(hou)的電流進行(xing)濾波。此處電流經過(guo)一(yi)次過(guo)濾，比較(jiao)平穩，發生(sheng)爆漿的可能性相對(dui)(dui)來說(shuo)小了不少。但(dan)如果環境溫(wen)度過(guo)高，電容(rong)(rong)同樣容(rong)(rong)易發生(sheng)爆漿。爆，報(bao)也(ye)。采用垃圾東西自然要爆，報(bao)應(ying)啊。欲(yu)知過(guo)去因(yin)者(zhe)，見其(qi)現在(zai)果;欲(yu)知未來果者(zhe)，見其(qi)現在(zai)因(yin)。
電解電容爆漿(jiang)的原因：
電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)(rong)爆漿(jiang)的(de)(de)(de)(de)(de)(de)原(yuan)因有很多，比如電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流大于允許的(de)(de)(de)(de)(de)(de)穩波電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流、使(shi)用(yong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)超出工作電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)、逆向電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)、頻繁的(de)(de)(de)(de)(de)(de)充放電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)等。但是(shi)最直接的(de)(de)(de)(de)(de)(de)原(yuan)因就是(shi)高(gao)溫(wen)(wen)。我們(men)知(zhi)道(dao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)(rong)有一(yi)個(ge)重要(yao)的(de)(de)(de)(de)(de)(de)參數就是(shi)耐溫(wen)(wen)值(zhi)，指(zhi)的(de)(de)(de)(de)(de)(de)就是(shi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)(rong)內部(bu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)解(jie)液的(de)(de)(de)(de)(de)(de)沸點。當電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)(rong)的(de)(de)(de)(de)(de)(de)內部(bu)溫(wen)(wen)度(du)(du)達(da)(da)到(dao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)解(jie)液的(de)(de)(de)(de)(de)(de)沸點時，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)解(jie)液開始沸騰，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)(rong)內部(bu)的(de)(de)(de)(de)(de)(de)壓(ya)力升(sheng)高(gao)，當壓(ya)力超過(guo)泄爆口的(de)(de)(de)(de)(de)(de)承受極限就發(fa)生了爆漿(jiang)。所以(yi)說溫(wen)(wen)度(du)(du)是(shi)導致(zhi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)(rong)爆漿(jiang)的(de)(de)(de)(de)(de)(de)直接原(yuan)因。電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)(rong)設計(ji)(ji)使(shi)用(yong)壽(shou)命(ming)大約為(wei)2萬小時，受環(huan)(huan)境溫(wen)(wen)度(du)(du)的(de)(de)(de)(de)(de)(de)影響也很大。電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)(rong)的(de)(de)(de)(de)(de)(de)使(shi)用(yong)壽(shou)命(ming)隨溫(wen)(wen)度(du)(du)的(de)(de)(de)(de)(de)(de)增加而減小，實驗證(zheng)明環(huan)(huan)境溫(wen)(wen)度(du)(du)每升(sheng)高(gao)10℃，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)(rong)的(de)(de)(de)(de)(de)(de)壽(shou)命(ming)就會減半。主要(yao)原(yuan)因就是(shi)溫(wen)(wen)度(du)(du)加速(su)化(hua)學反應(ying)而使(shi)介質隨時間退化(hua)失效，這樣電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)(rong)壽(shou)命(ming)終結。為(wei)了保證(zheng)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)(rong)的(de)(de)(de)(de)(de)(de)穩定性(xing)，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)(rong)在(zai)插(cha)板前要(yao)經過(guo)長時間的(de)(de)(de)(de)(de)(de)高(gao)溫(wen)(wen)環(huan)(huan)境的(de)(de)(de)(de)(de)(de)測試。即使(shi)是(shi)在(zai)100℃，高(gao)品質的(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)(rong)也可以(yi)工作幾千個(ge)小時。同時，我們(men)提到(dao)的(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)(rong)的(de)(de)(de)(de)(de)(de)壽(shou)命(ming)是(shi)指(zhi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)(rong)在(zai)使(shi)用(yong)過(guo)程(cheng)中，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)(rong)容(rong)(rong)(rong)(rong)(rong)(rong)(rong)量不會超過(guo)標準(zhun)范圍變化(hua)的(de)(de)(de)(de)(de)(de)10%。電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)(rong)壽(shou)命(ming)指(zhi)的(de)(de)(de)(de)(de)(de)是(shi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)(rong)容(rong)(rong)(rong)(rong)(rong)(rong)(rong)量的(de)(de)(de)(de)(de)(de)問題，而不是(shi)設計(ji)(ji)壽(shou)命(ming)到(dao)達(da)(da)之后(hou)就發(fa)生爆漿(jiang)。只是(shi)無法保證(zheng)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)(rong)(rong)的(de)(de)(de)(de)(de)(de)設計(ji)(ji)的(de)(de)(de)(de)(de)(de)容(rong)(rong)(rong)(rong)(rong)(rong)(rong)量標準(zhun)。
所以，短時期內，正(zheng)常使(shi)用的板(ban)卡電(dian)(dian)(dian)容(rong)就(jiu)發(fa)生爆漿的情(qing)(qing)況，這就(jiu)是電(dian)(dian)(dian)容(rong)品質問題。另外，不正(zheng)常的使(shi)用情(qing)(qing)況也(ye)(ye)有可能發(fa)生電(dian)(dian)(dian)容(rong)爆漿的情(qing)(qing)況。比(bi)如熱插拔電(dian)(dian)(dian)腦配件也(ye)(ye)會導致板(ban)卡局部電(dian)(dian)(dian)路(lu)電(dian)(dian)(dian)流、電(dian)(dian)(dian)壓(ya)的劇烈變(bian)化，從而引(yin)發(fa)電(dian)(dian)(dian)容(rong)使(shi)用故(gu)障。
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