文章主要是(shi)討論和分析(xi)開關(guan)(guan)電(dian)(dian)(dian)源印制(zhi)板(ban)布線原則(ze)、開關(guan)(guan)電(dian)(dian)(dian)源印制(zhi)板(ban)銅皮走(zou)線的(de)一些(xie)事項(xiang)、開關(guan)(guan)電(dian)(dian)(dian)源印制(zhi)板(ban)大電(dian)(dian)(dian)流走(zou)線的(de)處(chu)理以及(ji)反激電(dian)(dian)(dian)源反射電(dian)(dian)(dian)壓的(de)一個確定因素等方(fang)面，解決鋁(lv)基板(ban)在開關(guan)(guan)電(dian)(dian)(dian)源中的(de)應(ying)用(yong)、多層印制(zhi)板(ban)在開關(guan)(guan)電(dian)(dian)(dian)源電(dian)(dian)(dian)路中的(de)應(ying)用(yong)的(de)一些(xie)大家關(guan)(guan)注(zhu)的(de)問題。

　　一、引言

　　開(kai)(kai)關(guan)(guan)電(dian)(dian)(dian)(dian)(dian)(dian)源是(shi)一(yi)(yi)種(zhong)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)轉換(huan)電(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)，主要的(de)(de)工(gong)作內容是(shi)升壓(ya)和(he)降(jiang)壓(ya)，廣泛應(ying)(ying)用于現代電(dian)(dian)(dian)(dian)(dian)(dian)子產(chan)品。因為開(kai)(kai)關(guan)(guan)三(san)極(ji)管總是(shi)工(gong)作在 “開(kai)(kai)” 和(he)“關(guan)(guan)” 的(de)(de)狀(zhuang)態，所以叫開(kai)(kai)關(guan)(guan)電(dian)(dian)(dian)(dian)(dian)(dian)源。開(kai)(kai)關(guan)(guan)電(dian)(dian)(dian)(dian)(dian)(dian)源實質就(jiu)是(shi)一(yi)(yi)個振(zhen)蕩(dang)電(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)，這種(zhong)轉換(huan)電(dian)(dian)(dian)(dian)(dian)(dian)能(neng)的(de)(de)方(fang)式(shi)，不僅應(ying)(ying)用在電(dian)(dian)(dian)(dian)(dian)(dian)源電(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)，在其它的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)應(ying)(ying)用也很普(pu)遍，如液晶顯(xian)示(shi)器的(de)(de)背光電(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)、日光燈等(deng)。開(kai)(kai)關(guan)(guan)電(dian)(dian)(dian)(dian)(dian)(dian)源與變(bian)壓(ya)器相比(bi)具(ju)有效率高、穩性好、體積小等(deng)優點，缺點是(shi)功率相對(dui)較(jiao)小，而且會對(dui)電(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)產(chan)生高頻干(gan)擾，變(bian)壓(ya)器反饋式(shi)振(zhen)蕩(dang)電(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)，能(neng)產(chan)生有規(gui)律(lv)的(de)(de)脈沖電(dian)(dian)(dian)(dian)(dian)(dian)流或(huo)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)叫振(zhen)蕩(dang)電(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)，變(bian)壓(ya)器反饋式(shi)振(zhen)蕩(dang)電(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)就(jiu)是(shi)能(neng)滿足這種(zhong)條件(jian)的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)。

　　開(kai)關(guan)(guan)電(dian)(dian)(dian)源(yuan)分(fen)為，隔(ge)離(li)(li)與非隔(ge)離(li)(li)兩種(zhong)形(xing)式(shi)(shi)(shi)，在(zai)這里主要(yao)談一(yi)談隔(ge)離(li)(li)式(shi)(shi)(shi)開(kai)關(guan)(guan)電(dian)(dian)(dian)源(yuan)的拓撲形(xing)式(shi)(shi)(shi)，在(zai)下文(wen)中，非特別說明，均指(zhi)隔(ge)離(li)(li)電(dian)(dian)(dian)源(yuan)。隔(ge)離(li)(li)電(dian)(dian)(dian)源(yuan)按(an)照結構形(xing)式(shi)(shi)(shi)不(bu)同(tong)，可(ke)分(fen)為兩大類：正激(ji)(ji)式(shi)(shi)(shi)和反激(ji)(ji)式(shi)(shi)(shi)。反激(ji)(ji)式(shi)(shi)(shi)指(zhi)在(zai)變壓(ya)(ya)(ya)器(qi)原邊(bian)(bian)(bian)(bian)導(dao)通(tong)時副(fu)(fu)邊(bian)(bian)(bian)(bian)截(jie)止(zhi)，變壓(ya)(ya)(ya)器(qi)儲能。原邊(bian)(bian)(bian)(bian)截(jie)止(zhi)時，副(fu)(fu)邊(bian)(bian)(bian)(bian)導(dao)通(tong)，能量(liang)釋放到負載的工(gong)作狀態，一(yi)般常規反激(ji)(ji)式(shi)(shi)(shi)電(dian)(dian)(dian)源(yuan)單(dan)管(guan)多(duo)，雙(shuang)管(guan)的不(bu)常見。正激(ji)(ji)式(shi)(shi)(shi)指(zhi)在(zai)變壓(ya)(ya)(ya)器(qi)原邊(bian)(bian)(bian)(bian)導(dao)通(tong)同(tong)時副(fu)(fu)邊(bian)(bian)(bian)(bian)感應出對應電(dian)(dian)(dian)壓(ya)(ya)(ya)輸出到負載，能量(liang)通(tong)過變壓(ya)(ya)(ya)器(qi)直接傳遞。按(an)規格(ge)又(you)可(ke)分(fen)為常規正激(ji)(ji)，包(bao)括(kuo)單(dan)管(guan)正激(ji)(ji)，雙(shuang)管(guan)正 激(ji)(ji)。半橋、橋式(shi)(shi)(shi)電(dian)(dian)(dian)路都屬于正激(ji)(ji)電(dian)(dian)(dian)路。

　　正(zheng)激(ji)和反激(ji)電(dian)(dian)路(lu)(lu)(lu)各有其特點，在(zai)設計電(dian)(dian)路(lu)(lu)(lu)的過程中為(wei)達到最優性價比，可(ke)(ke)以靈(ling)活(huo)運用(yong)(yong)(yong)。一(yi)般在(zai)小功率場合可(ke)(ke)選用(yong)(yong)(yong)反激(ji)式。稍微大一(yi)些可(ke)(ke)采(cai)用(yong)(yong)(yong)單(dan)管正(zheng)激(ji)電(dian)(dian)路(lu)(lu)(lu)，中等功率可(ke)(ke)采(cai)用(yong)(yong)(yong)雙管正(zheng)激(ji)電(dian)(dian)路(lu)(lu)(lu)或半橋(qiao)電(dian)(dian)路(lu)(lu)(lu)，低電(dian)(dian)壓(ya)時采(cai)用(yong)(yong)(yong)推挽(wan)電(dian)(dian)路(lu)(lu)(lu)，與半橋(qiao)工作(zuo)狀態相同(tong)。大功率輸出，一(yi)般采(cai)用(yong)(yong)(yong)橋(qiao)式電(dian)(dian)路(lu)(lu)(lu)，低壓(ya)也可(ke)(ke)采(cai)用(yong)(yong)(yong)推挽(wan)電(dian)(dian)路(lu)(lu)(lu)。

　　反激(ji)式(shi)電源(yuan)(yuan)因其結構簡單，省掉了一(yi)個和(he)變壓器體積(ji)大(da)小(xiao)差不(bu)多(duo)的(de)(de)電感，而在中(zhong)(zhong)小(xiao)功(gong)(gong)率電源(yuan)(yuan)中(zhong)(zhong)得到(dao)(dao)廣泛的(de)(de)應用(yong)。在有些(xie)介(jie)紹中(zhong)(zhong)講到(dao)(dao)反激(ji)式(shi)電源(yuan)(yuan)功(gong)(gong)率只能做(zuo)到(dao)(dao)幾十(shi)瓦，輸出功(gong)(gong)率超(chao)過100瓦就沒有優(you)勢，實(shi)現(xian)起來有難度。本人認為(wei)一(yi)般情況(kuang)下(xia)是(shi)這(zhe)樣的(de)(de)，但也(ye)不(bu)能一(yi)概而論，PI公司的(de)(de)TOP芯(xin)片就可做(zuo)到(dao)(dao)300瓦，有文章介(jie)紹反激(ji)電源(yuan)(yuan)可做(zuo)到(dao)(dao)上千瓦，但沒見過實(shi)物。輸出功(gong)(gong)率大(da)小(xiao)與輸出電壓高低有關。

　　反激電源(yuan)變(bian)壓器漏(lou)感是一個非常關鍵(jian)的參數，由于(yu)(yu)反激電源(yuan)需(xu)要變(bian)壓器儲存能(neng)量，要 使(shi)變(bian)壓器鐵芯得到(dao)充分(fen)利用，一般都要在(zai)磁(ci)路(lu)(lu)中(zhong)開氣隙，其(qi)目的是改變(bian)鐵芯磁(ci)滯(zhi)回(hui)線的斜率(lv)，使(shi)變(bian)壓器能(neng)夠承受大(da)的脈(mo)沖(chong)(chong)電流沖(chong)(chong)擊，而不(bu)至于(yu)(yu)鐵芯進(jin)入飽和非線形(xing)狀 態(tai)，磁(ci)路(lu)(lu)中(zhong)氣隙處于(yu)(yu)高磁(ci)阻狀態(tai)，在(zai)磁(ci)路(lu)(lu)中(zhong)產生漏(lou)磁(ci)遠大(da)于(yu)(yu)完全閉合磁(ci)路(lu)(lu)。

　　脈沖電(dian)(dian)壓(ya)(ya)連線(xian)(xian)盡(jin)可能(neng)短，其中輸(shu)入開(kai)關(guan)管到(dao)變壓(ya)(ya)器(qi)連線(xian)(xian)，輸(shu)出(chu)變壓(ya)(ya)器(qi)到(dao)整流(liu)(liu)管連接(jie)線(xian)(xian)。脈沖電(dian)(dian)流(liu)(liu)環(huan)路(lu)盡(jin)可能(neng)小如輸(shu)入濾波電(dian)(dian)容正(zheng)到(dao)變壓(ya)(ya)器(qi)到(dao)開(kai)關(guan)管返回電(dian)(dian)容負。輸(shu)出(chu)部(bu)分變壓(ya)(ya)器(qi)出(chu)端(duan)到(dao)整流(liu)(liu)管到(dao)輸(shu)出(chu)電(dian)(dian)感到(dao)輸(shu)出(chu)電(dian)(dian)容返回變壓(ya)(ya)器(qi)電(dian)(dian)路(lu)中X電(dian)(dian)容要盡(jin)量接(jie) 近開(kai)關(guan)電(dian)(dian)源輸(shu)入端(duan)，輸(shu)入線(xian)(xian)應(ying)(ying)避免(mian)與(yu)其他電(dian)(dian)路(lu)平行，應(ying)(ying)避開(kai)。Y電(dian)(dian)容應(ying)(ying)放置在機殼(ke)接(jie)地端(duan)子(zi)或(huo)FG連接(jie)端(duan)。共摸電(dian)(dian)感應(ying)(ying)與(yu)變壓(ya)(ya)器(qi)保持一定距離，以避免(mian)磁偶合。

　　輸出電(dian)(dian)容(rong)一(yi)般可采用兩只(zhi)一(yi)只(zhi)靠近(jin)整流管另一(yi)只(zhi)應靠近(jin)輸出端子，可影響(xiang)電(dian)(dian)源輸出紋波(bo)指標，兩只(zhi)小容(rong)量電(dian)(dian)容(rong)并聯效果應優于用一(yi)只(zhi)大容(rong)量電(dian)(dian)容(rong)。發熱(re)器件要(yao)和(he)電(dian)(dian)解(jie) 電(dian)(dian)容(rong)保(bao)持一(yi)定(ding)距離，以延長整機(ji)壽命，電(dian)(dian)解(jie)電(dian)(dian)容(rong)是開關電(dian)(dian)源壽命的瓶勁(jing)，如(ru)變壓器、功(gong)率(lv)管、大功(gong)率(lv)電(dian)(dian)阻要(yao)和(he)電(dian)(dian)解(jie)保(bao)持距離，電(dian)(dian)解(jie)之間(jian)也(ye)須留(liu)出散熱(re)空(kong)間(jian)，條件允許可將(jiang)其(qi)放置在進風口。

　　二、印制板布線的一些原則

　　印制(zhi)板設計(ji)(ji)時(shi)，要(yao)考慮到(dao)干(gan)(gan)擾對(dui)系統的(de)(de)(de)影響(xiang)，將電(dian)(dian)(dian)(dian)路(lu)(lu)的(de)(de)(de)模擬部(bu)(bu)分(fen)和(he)數字部(bu)(bu)分(fen)的(de)(de)(de)電(dian)(dian)(dian)(dian)路(lu)(lu)嚴格(ge)分(fen)開，對(dui)核心電(dian)(dian)(dian)(dian)路(lu)(lu)重點防護，將系統地線(xian)環繞，并(bing)布線(xian)盡可能(neng)粗，電(dian)(dian)(dian)(dian)源增加濾波電(dian)(dian)(dian)(dian)路(lu)(lu)，采(cai)用DC-DC隔(ge)離，信(xin)號(hao)采(cai)用光電(dian)(dian)(dian)(dian)隔(ge)離，設計(ji)(ji)隔(ge)離電(dian)(dian)(dian)(dian)源，分(fen)析容易(yi)產生干(gan)(gan)擾的(de)(de)(de)部(bu)(bu)分(fen)（如時(shi)鐘(zhong)電(dian)(dian)(dian)(dian)路(lu)(lu)、通訊電(dian)(dian)(dian)(dian)路(lu)(lu)等）和(he)容易(yi)被(bei)干(gan)(gan)擾的(de)(de)(de)部(bu)(bu)分(fen)（如模擬采(cai)樣電(dian)(dian)(dian)(dian)路(lu)(lu)等），對(dui)這兩種(zhong)類型的(de)(de)(de)電(dian)(dian)(dian)(dian)路(lu)(lu)分(fen)別采(cai)取(qu)措(cuo)施。對(dui)于干(gan)(gan)擾元(yuan)(yuan)件(jian)(jian)采(cai)取(qu)抑制(zhi)措(cuo)施，對(dui)敏感元(yuan)(yuan)件(jian)(jian)采(cai)取(qu)隔(ge)離和(he)保護措(cuo)施，并(bing)且將它們(men)在空間(jian)和(he)電(dian)(dian)(dian)(dian)氣上拉開距離。在板級設計(ji)(ji)時(shi)，還要(yao)注意元(yuan)(yuan)器件(jian)(jian)放置要(yao)遠離印制(zhi)板邊沿，這對(dui)防護空氣放電(dian)(dian)(dian)(dian)是有利的(de)(de)(de)。樣電(dian)(dian)(dian)(dian)路(lu)(lu)的(de)(de)(de)原理(li)圖(tu)設計(ji)(ji)參見圖(tu)1。

　　圖(tu)1 樣電路的原理(li)圖(tu)設計原理(li)圖(tu)

　　線(xian)(xian)間(jian)距：隨著(zhu)印制線(xian)(xian)路板(ban)制造工藝的(de)不斷(duan)完(wan)善(shan)和提高，一(yi)(yi)般加工廠制造出(chu)線(xian)(xian)間(jian)距等于(yu)甚(shen)至(zhi)小(xiao)于(yu)0.1mm已經(jing)不存在什么(me)問(wen)題(ti)，完(wan)全能夠(gou)滿足大多數應(ying)用(yong)場合。考(kao)慮 到(dao)開(kai)關電源所采用(yong)的(de)元器件及(ji)生產(chan)工藝，一(yi)(yi)般雙面板(ban)最小(xiao)線(xian)(xian)間(jian)距設為0.3mm，單面板(ban)最小(xiao)線(xian)(xian)間(jian)距設為0.5mm，焊(han)盤(pan)與(yu)焊(han)盤(pan)、焊(han)盤(pan)與(yu)過孔或過孔與(yu)過孔，最小(xiao) 間(jian)距設為0.5mm，可(ke)避免在焊(han)接操作過程中出(chu)現(xian)“橋接”現(xian)象。，這樣大多數制板(ban)廠都能夠(gou)很(hen)輕松滿足生產(chan)要求，并可(ke)以把成(cheng)品率控制得非常高，亦可(ke)實現(xian)合理 的(de)布線(xian)(xian)密度及(ji)有(you)一(yi)(yi)個較經(jing)濟的(de)成(cheng)本。