文章主(zhu)要是討(tao)論和分析開(kai)關(guan)電(dian)源(yuan)(yuan)印(yin)(yin)制(zhi)板布(bu)線(xian)(xian)原則、開(kai)關(guan)電(dian)源(yuan)(yuan)印(yin)(yin)制(zhi)板銅皮走線(xian)(xian)的一些(xie)事項(xiang)、開(kai)關(guan)電(dian)源(yuan)(yuan)印(yin)(yin)制(zhi)板大(da)電(dian)流走線(xian)(xian)的處理(li)以(yi)及反(fan)激電(dian)源(yuan)(yuan)反(fan)射電(dian)壓的一個(ge)確定(ding)因素等方面，解決鋁(lv)基板在開(kai)關(guan)電(dian)源(yuan)(yuan)中(zhong)的應用、多(duo)層印(yin)(yin)制(zhi)板在開(kai)關(guan)電(dian)源(yuan)(yuan)電(dian)路(lu)中(zhong)的應用的一些(xie)大(da)家(jia)關(guan)注的問題。

　　一、引言

　　開(kai)(kai)關(guan)電(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)是一種(zhong)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)轉換電(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)，主(zhu)要的(de)工作(zuo)內容是升壓(ya)和降壓(ya)，廣泛應(ying)(ying)用(yong)(yong)于(yu)現代(dai)電(dian)(dian)(dian)(dian)(dian)(dian)子產(chan)(chan)品(pin)。因為開(kai)(kai)關(guan)三極管總是工作(zuo)在 “開(kai)(kai)” 和“關(guan)” 的(de)狀態，所以叫開(kai)(kai)關(guan)電(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)。開(kai)(kai)關(guan)電(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)實質就是一個振蕩電(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)，這種(zhong)轉換電(dian)(dian)(dian)(dian)(dian)(dian)能(neng)的(de)方式(shi)，不僅應(ying)(ying)用(yong)(yong)在電(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)電(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)，在其它的(de)電(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)應(ying)(ying)用(yong)(yong)也很普遍，如液晶顯(xian)示(shi)器的(de)背光電(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)、日光燈(deng)等。開(kai)(kai)關(guan)電(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)與變(bian)壓(ya)器相比具有(you)效率高、穩性好、體積小(xiao)等優點，缺點是功(gong)率相對較小(xiao)，而(er)且會對電(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)產(chan)(chan)生高頻干(gan)擾(rao)，變(bian)壓(ya)器反饋式(shi)振蕩電(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)，能(neng)產(chan)(chan)生有(you)規律的(de)脈沖電(dian)(dian)(dian)(dian)(dian)(dian)流或(huo)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)的(de)電(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)叫振蕩電(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)，變(bian)壓(ya)器反饋式(shi)振蕩電(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)就是能(neng)滿(man)足這種(zhong)條件的(de)電(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)。

　　開關電(dian)源(yuan)分(fen)為，隔離(li)(li)與非隔離(li)(li)兩種形(xing)式(shi)(shi)(shi)(shi)(shi)，在(zai)這(zhe)里主要(yao)談(tan)一談(tan)隔離(li)(li)式(shi)(shi)(shi)(shi)(shi)開關電(dian)源(yuan)的(de)拓撲形(xing)式(shi)(shi)(shi)(shi)(shi)，在(zai)下文中，非特(te)別說明(ming)，均(jun)指(zhi)隔離(li)(li)電(dian)源(yuan)。隔離(li)(li)電(dian)源(yuan)按照結(jie)構形(xing)式(shi)(shi)(shi)(shi)(shi)不同(tong)，可分(fen)為兩大類：正激式(shi)(shi)(shi)(shi)(shi)和反激式(shi)(shi)(shi)(shi)(shi)。反激式(shi)(shi)(shi)(shi)(shi)指(zhi)在(zai)變壓器(qi)(qi)原(yuan)邊導通時副(fu)(fu)邊截(jie)止，變壓器(qi)(qi)儲能。原(yuan)邊截(jie)止時，副(fu)(fu)邊導通，能量釋(shi)放(fang)到(dao)負(fu)載(zai)的(de)工作狀態，一般常(chang)(chang)規(gui)反激式(shi)(shi)(shi)(shi)(shi)電(dian)源(yuan)單(dan)管(guan)多，雙(shuang)管(guan)的(de)不常(chang)(chang)見。正激式(shi)(shi)(shi)(shi)(shi)指(zhi)在(zai)變壓器(qi)(qi)原(yuan)邊導通同(tong)時副(fu)(fu)邊感應(ying)出對應(ying)電(dian)壓輸出到(dao)負(fu)載(zai)，能量通過變壓器(qi)(qi)直接(jie)傳(chuan)遞。按規(gui)格又可分(fen)為常(chang)(chang)規(gui)正激，包(bao)括單(dan)管(guan)正激，雙(shuang)管(guan)正 激。半橋、橋式(shi)(shi)(shi)(shi)(shi)電(dian)路都屬(shu)于正激電(dian)路。

　　正激和反(fan)激電路(lu)(lu)(lu)(lu)各(ge)有(you)其特點，在(zai)設計電路(lu)(lu)(lu)(lu)的過程中為達到最優性價比，可(ke)以靈活運用(yong)(yong)。一(yi)般在(zai)小功(gong)率場合可(ke)選用(yong)(yong)反(fan)激式。稍微大一(yi)些可(ke)采(cai)用(yong)(yong)單管正激電路(lu)(lu)(lu)(lu)，中等功(gong)率可(ke)采(cai)用(yong)(yong)雙管正激電路(lu)(lu)(lu)(lu)或半橋(qiao)電路(lu)(lu)(lu)(lu)，低(di)電壓時采(cai)用(yong)(yong)推(tui)挽電路(lu)(lu)(lu)(lu)，與半橋(qiao)工(gong)作狀態相(xiang)同。大功(gong)率輸出，一(yi)般采(cai)用(yong)(yong)橋(qiao)式電路(lu)(lu)(lu)(lu)，低(di)壓也可(ke)采(cai)用(yong)(yong)推(tui)挽電路(lu)(lu)(lu)(lu)。

　　反激式(shi)電源因(yin)其結構(gou)簡單，省掉了一(yi)(yi)個和變壓器體積大(da)小(xiao)(xiao)差(cha)不多的電感，而(er)在中(zhong)小(xiao)(xiao)功(gong)率(lv)電源中(zhong)得到(dao)(dao)廣泛的應用。在有些介(jie)紹(shao)中(zhong)講到(dao)(dao)反激式(shi)電源功(gong)率(lv)只能做到(dao)(dao)幾十瓦，輸出功(gong)率(lv)超過100瓦就(jiu)沒有優勢，實現(xian)起來有難度。本(ben)人認為一(yi)(yi)般情(qing)況下是這樣的，但也不能一(yi)(yi)概而(er)論，PI公(gong)司的TOP芯片就(jiu)可做到(dao)(dao)300瓦，有文(wen)章介(jie)紹(shao)反激電源可做到(dao)(dao)上千瓦，但沒見過實物。輸出功(gong)率(lv)大(da)小(xiao)(xiao)與輸出電壓高低有關。

　　反激電(dian)源變壓器(qi)漏(lou)感是一(yi)個非常關鍵(jian)的(de)參數，由于(yu)(yu)反激電(dian)源需要變壓器(qi)儲存能量(liang)，要 使(shi)變壓器(qi)鐵(tie)芯(xin)得到充(chong)分利用，一(yi)般都要在(zai)磁(ci)(ci)路(lu)中開氣(qi)隙，其目的(de)是改(gai)變鐵(tie)芯(xin)磁(ci)(ci)滯回(hui)線(xian)的(de)斜率，使(shi)變壓器(qi)能夠承受大的(de)脈沖(chong)電(dian)流沖(chong)擊，而不至于(yu)(yu)鐵(tie)芯(xin)進入飽和非線(xian)形狀 態，磁(ci)(ci)路(lu)中氣(qi)隙處于(yu)(yu)高磁(ci)(ci)阻狀態，在(zai)磁(ci)(ci)路(lu)中產生漏(lou)磁(ci)(ci)遠大于(yu)(yu)完全(quan)閉合磁(ci)(ci)路(lu)。

　　脈沖電(dian)壓(ya)連(lian)線盡(jin)可能(neng)(neng)短，其(qi)中輸(shu)(shu)入(ru)開(kai)(kai)關管(guan)到變壓(ya)器連(lian)線，輸(shu)(shu)出(chu)變壓(ya)器到整流(liu)(liu)管(guan)連(lian)接(jie)線。脈沖電(dian)流(liu)(liu)環路盡(jin)可能(neng)(neng)小如輸(shu)(shu)入(ru)濾波電(dian)容(rong)(rong)正到變壓(ya)器到開(kai)(kai)關管(guan)返回電(dian)容(rong)(rong)負(fu)。輸(shu)(shu)出(chu)部分變壓(ya)器出(chu)端(duan)到整流(liu)(liu)管(guan)到輸(shu)(shu)出(chu)電(dian)感到輸(shu)(shu)出(chu)電(dian)容(rong)(rong)返回變壓(ya)器電(dian)路中X電(dian)容(rong)(rong)要盡(jin)量接(jie) 近開(kai)(kai)關電(dian)源(yuan)輸(shu)(shu)入(ru)端(duan)，輸(shu)(shu)入(ru)線應避(bi)免(mian)與其(qi)他(ta)電(dian)路平行(xing)，應避(bi)開(kai)(kai)。Y電(dian)容(rong)(rong)應放置(zhi)在機殼接(jie)地端(duan)子(zi)或FG連(lian)接(jie)端(duan)。共摸電(dian)感應與變壓(ya)器保持一定距離，以避(bi)免(mian)磁偶合。

　　輸出(chu)(chu)電容一般可(ke)采用兩(liang)只一只靠(kao)近整流管另一只應靠(kao)近輸出(chu)(chu)端子，可(ke)影響電源輸出(chu)(chu)紋波指(zhi)標，兩(liang)只小容量電容并(bing)聯效(xiao)果(guo)應優于(yu)用一只大容量電容。發熱器件(jian)要和(he)(he)電解(jie)(jie) 電容保持一定(ding)距(ju)離，以延長整機壽命(ming)(ming)，電解(jie)(jie)電容是(shi)開關(guan)電源壽命(ming)(ming)的(de)瓶勁，如變壓(ya)器、功率管、大功率電阻要和(he)(he)電解(jie)(jie)保持距(ju)離，電解(jie)(jie)之(zhi)間(jian)也須留(liu)出(chu)(chu)散(san)熱空間(jian)，條件(jian)允許可(ke)將其放置在進風口。

　　二、印制板布線的一些原則

　　印制板(ban)(ban)設計(ji)(ji)時，要(yao)考慮到(dao)干擾(rao)對系(xi)統的(de)(de)影響，將電(dian)(dian)(dian)(dian)路的(de)(de)模擬(ni)部(bu)分(fen)(fen)和(he)數字(zi)部(bu)分(fen)(fen)的(de)(de)電(dian)(dian)(dian)(dian)路嚴格(ge)分(fen)(fen)開，對核心電(dian)(dian)(dian)(dian)路重點防(fang)護(hu)，將系(xi)統地線(xian)環繞，并布(bu)線(xian)盡(jin)可能粗，電(dian)(dian)(dian)(dian)源增加濾波電(dian)(dian)(dian)(dian)路，采(cai)用DC-DC隔離(li)，信號(hao)采(cai)用光電(dian)(dian)(dian)(dian)隔離(li)，設計(ji)(ji)隔離(li)電(dian)(dian)(dian)(dian)源，分(fen)(fen)析容易產(chan)生干擾(rao)的(de)(de)部(bu)分(fen)(fen)（如(ru)時鐘電(dian)(dian)(dian)(dian)路、通訊電(dian)(dian)(dian)(dian)路等(deng)）和(he)容易被干擾(rao)的(de)(de)部(bu)分(fen)(fen)（如(ru)模擬(ni)采(cai)樣電(dian)(dian)(dian)(dian)路等(deng)），對這(zhe)兩種類型(xing)的(de)(de)電(dian)(dian)(dian)(dian)路分(fen)(fen)別(bie)采(cai)取(qu)(qu)措(cuo)(cuo)施(shi)。對于干擾(rao)元件采(cai)取(qu)(qu)抑制措(cuo)(cuo)施(shi)，對敏感(gan)元件采(cai)取(qu)(qu)隔離(li)和(he)保護(hu)措(cuo)(cuo)施(shi)，并且將它們在(zai)空間和(he)電(dian)(dian)(dian)(dian)氣上拉(la)開距離(li)。在(zai)板(ban)(ban)級設計(ji)(ji)時，還要(yao)注意元器件放(fang)置要(yao)遠離(li)印制板(ban)(ban)邊(bian)沿，這(zhe)對防(fang)護(hu)空氣放(fang)電(dian)(dian)(dian)(dian)是有(you)利(li)的(de)(de)。樣電(dian)(dian)(dian)(dian)路的(de)(de)原理圖(tu)設計(ji)(ji)參(can)見(jian)圖(tu)1。

　　圖1 樣電(dian)路的原(yuan)理(li)圖設(she)計原(yuan)理(li)圖

　　線間距(ju)：隨著印制(zhi)線路(lu)板(ban)制(zhi)造(zao)工藝的(de)不(bu)斷(duan)完(wan)善(shan)和提高，一般(ban)加工廠(chang)制(zhi)造(zao)出線間距(ju)等于甚至小(xiao)于0.1mm已經不(bu)存在什么問題，完(wan)全能(neng)夠滿足(zu)大(da)多數應用場合。考慮 到開關電源(yuan)所采用的(de)元器件及生(sheng)產(chan)工藝，一般(ban)雙面(mian)板(ban)最小(xiao)線間距(ju)設為0.3mm，單面(mian)板(ban)最小(xiao)線間距(ju)設為0.5mm，焊(han)盤與(yu)焊(han)盤、焊(han)盤與(yu)過(guo)(guo)(guo)孔(kong)或過(guo)(guo)(guo)孔(kong)與(yu)過(guo)(guo)(guo)孔(kong)，最小(xiao) 間距(ju)設為0.5mm，可避免(mian)在焊(han)接操(cao)作(zuo)過(guo)(guo)(guo)程(cheng)中出現(xian)(xian)“橋接”現(xian)(xian)象。，這樣大(da)多數制(zhi)板(ban)廠(chang)都能(neng)夠很輕松滿足(zu)生(sheng)產(chan)要求，并(bing)可以把成(cheng)品(pin)率控制(zhi)得(de)非常高，亦可實現(xian)(xian)合理 的(de)布線密度(du)及有一個(ge)較經濟的(de)成(cheng)本。