文章主要是(shi)討論和分析開(kai)(kai)關(guan)(guan)(guan)電(dian)(dian)(dian)源(yuan)(yuan)印(yin)制(zhi)(zhi)板(ban)(ban)布線(xian)(xian)原則、開(kai)(kai)關(guan)(guan)(guan)電(dian)(dian)(dian)源(yuan)(yuan)印(yin)制(zhi)(zhi)板(ban)(ban)銅皮走線(xian)(xian)的(de)(de)(de)一些事項、開(kai)(kai)關(guan)(guan)(guan)電(dian)(dian)(dian)源(yuan)(yuan)印(yin)制(zhi)(zhi)板(ban)(ban)大電(dian)(dian)(dian)流走線(xian)(xian)的(de)(de)(de)處(chu)理(li)以及反激電(dian)(dian)(dian)源(yuan)(yuan)反射電(dian)(dian)(dian)壓的(de)(de)(de)一個確定(ding)因素等方面，解決鋁基(ji)板(ban)(ban)在(zai)開(kai)(kai)關(guan)(guan)(guan)電(dian)(dian)(dian)源(yuan)(yuan)中的(de)(de)(de)應(ying)用、多層印(yin)制(zhi)(zhi)板(ban)(ban)在(zai)開(kai)(kai)關(guan)(guan)(guan)電(dian)(dian)(dian)源(yuan)(yuan)電(dian)(dian)(dian)路中的(de)(de)(de)應(ying)用的(de)(de)(de)一些大家關(guan)(guan)(guan)注的(de)(de)(de)問(wen)題。

　　一、引言

　　開(kai)關(guan)電(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)是(shi)(shi)一(yi)種電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)轉(zhuan)換電(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)，主要的(de)(de)工作內容是(shi)(shi)升壓(ya)(ya)和降(jiang)壓(ya)(ya)，廣泛應(ying)用于現代(dai)電(dian)(dian)(dian)(dian)(dian)(dian)子產(chan)品。因為開(kai)關(guan)三極管總是(shi)(shi)工作在(zai)(zai)(zai) “開(kai)” 和“關(guan)” 的(de)(de)狀態(tai)，所以(yi)叫(jiao)開(kai)關(guan)電(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)。開(kai)關(guan)電(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)實(shi)質(zhi)就是(shi)(shi)一(yi)個振(zhen)蕩(dang)(dang)電(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)，這種轉(zhuan)換電(dian)(dian)(dian)(dian)(dian)(dian)能的(de)(de)方(fang)式(shi)(shi)，不僅應(ying)用在(zai)(zai)(zai)電(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)電(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)，在(zai)(zai)(zai)其它(ta)的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)應(ying)用也很普遍，如液(ye)晶顯(xian)示器(qi)(qi)的(de)(de)背光(guang)電(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)、日光(guang)燈等(deng)(deng)。開(kai)關(guan)電(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)與變壓(ya)(ya)器(qi)(qi)相比具(ju)有效率高(gao)、穩性(xing)好、體積(ji)小等(deng)(deng)優(you)點，缺點是(shi)(shi)功(gong)率相對較(jiao)小，而(er)且會對電(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)產(chan)生(sheng)高(gao)頻(pin)干擾，變壓(ya)(ya)器(qi)(qi)反饋式(shi)(shi)振(zhen)蕩(dang)(dang)電(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)，能產(chan)生(sheng)有規律(lv)的(de)(de)脈沖電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)或電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)叫(jiao)振(zhen)蕩(dang)(dang)電(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)，變壓(ya)(ya)器(qi)(qi)反饋式(shi)(shi)振(zhen)蕩(dang)(dang)電(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)就是(shi)(shi)能滿(man)足(zu)這種條(tiao)件的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)。

　　開關電(dian)(dian)(dian)源(yuan)(yuan)(yuan)分為，隔離(li)與非隔離(li)兩(liang)種形(xing)式，在這里主要談(tan)一(yi)談(tan)隔離(li)式開關電(dian)(dian)(dian)源(yuan)(yuan)(yuan)的(de)拓撲形(xing)式，在下文中(zhong)，非特別說(shuo)明，均指(zhi)隔離(li)電(dian)(dian)(dian)源(yuan)(yuan)(yuan)。隔離(li)電(dian)(dian)(dian)源(yuan)(yuan)(yuan)按照結構形(xing)式不同(tong)，可分為兩(liang)大類：正(zheng)激(ji)式和(he)反(fan)(fan)激(ji)式。反(fan)(fan)激(ji)式指(zhi)在變(bian)(bian)壓器(qi)(qi)原邊導通(tong)時(shi)副邊截止，變(bian)(bian)壓器(qi)(qi)儲能(neng)。原邊截止時(shi)，副邊導通(tong)，能(neng)量(liang)釋放到(dao)負載(zai)的(de)工作(zuo)狀態，一(yi)般(ban)常規(gui)反(fan)(fan)激(ji)式電(dian)(dian)(dian)源(yuan)(yuan)(yuan)單管(guan)(guan)多，雙(shuang)管(guan)(guan)的(de)不常見。正(zheng)激(ji)式指(zhi)在變(bian)(bian)壓器(qi)(qi)原邊導通(tong)同(tong)時(shi)副邊感應出對應電(dian)(dian)(dian)壓輸出到(dao)負載(zai)，能(neng)量(liang)通(tong)過變(bian)(bian)壓器(qi)(qi)直接傳遞。按規(gui)格(ge)又可分為常規(gui)正(zheng)激(ji)，包(bao)括單管(guan)(guan)正(zheng)激(ji)，雙(shuang)管(guan)(guan)正(zheng) 激(ji)。半(ban)橋(qiao)、橋(qiao)式電(dian)(dian)(dian)路都屬于正(zheng)激(ji)電(dian)(dian)(dian)路。

　　正激(ji)和反激(ji)電(dian)(dian)路(lu)(lu)(lu)(lu)各有(you)其特(te)點(dian)，在設計電(dian)(dian)路(lu)(lu)(lu)(lu)的過程中(zhong)為(wei)達(da)到最優性價比，可(ke)以靈活運(yun)用(yong)。一般(ban)在小功率場(chang)合(he)可(ke)選用(yong)反激(ji)式(shi)。稍微大一些可(ke)采(cai)用(yong)單管正激(ji)電(dian)(dian)路(lu)(lu)(lu)(lu)，中(zhong)等(deng)功率可(ke)采(cai)用(yong)雙管正激(ji)電(dian)(dian)路(lu)(lu)(lu)(lu)或半(ban)橋(qiao)電(dian)(dian)路(lu)(lu)(lu)(lu)，低電(dian)(dian)壓(ya)時采(cai)用(yong)推(tui)(tui)挽電(dian)(dian)路(lu)(lu)(lu)(lu)，與(yu)半(ban)橋(qiao)工作狀態相同(tong)。大功率輸出，一般(ban)采(cai)用(yong)橋(qiao)式(shi)電(dian)(dian)路(lu)(lu)(lu)(lu)，低壓(ya)也可(ke)采(cai)用(yong)推(tui)(tui)挽電(dian)(dian)路(lu)(lu)(lu)(lu)。

　　反(fan)激式電(dian)(dian)(dian)源因其結構簡單，省掉了一個和變壓器體(ti)積大(da)小(xiao)差不(bu)多的電(dian)(dian)(dian)感(gan)，而在中(zhong)小(xiao)功(gong)率(lv)電(dian)(dian)(dian)源中(zhong)得到(dao)廣(guang)泛的應(ying)用。在有(you)(you)些介(jie)紹中(zhong)講到(dao)反(fan)激式電(dian)(dian)(dian)源功(gong)率(lv)只能做到(dao)幾(ji)十瓦(wa)，輸出(chu)功(gong)率(lv)超(chao)過100瓦(wa)就沒(mei)(mei)有(you)(you)優勢(shi)，實現起(qi)來有(you)(you)難(nan)度(du)。本人認(ren)為一般情況下(xia)是這樣的，但(dan)也不(bu)能一概(gai)而論(lun)，PI公司的TOP芯片就可做到(dao)300瓦(wa)，有(you)(you)文章(zhang)介(jie)紹反(fan)激電(dian)(dian)(dian)源可做到(dao)上千瓦(wa)，但(dan)沒(mei)(mei)見過實物(wu)。輸出(chu)功(gong)率(lv)大(da)小(xiao)與輸出(chu)電(dian)(dian)(dian)壓高低(di)有(you)(you)關。

　　反(fan)激電源變壓(ya)(ya)器(qi)(qi)漏感是(shi)一個非常關鍵(jian)的(de)參數(shu)，由(you)于(yu)(yu)反(fan)激電源需要變壓(ya)(ya)器(qi)(qi)儲存能量(liang)，要 使變壓(ya)(ya)器(qi)(qi)鐵(tie)(tie)芯得(de)到充分(fen)利用，一般都要在磁(ci)(ci)路(lu)中開氣隙，其目(mu)的(de)是(shi)改變鐵(tie)(tie)芯磁(ci)(ci)滯(zhi)回線的(de)斜率，使變壓(ya)(ya)器(qi)(qi)能夠承受大(da)的(de)脈沖電流沖擊，而不至于(yu)(yu)鐵(tie)(tie)芯進(jin)入飽和非線形(xing)狀 態，磁(ci)(ci)路(lu)中氣隙處(chu)于(yu)(yu)高(gao)磁(ci)(ci)阻狀態，在磁(ci)(ci)路(lu)中產生漏磁(ci)(ci)遠大(da)于(yu)(yu)完全(quan)閉合磁(ci)(ci)路(lu)。

　　脈沖電(dian)(dian)(dian)(dian)(dian)壓(ya)連線(xian)盡可(ke)能短(duan)，其中輸(shu)入(ru)開關管(guan)到(dao)(dao)變(bian)壓(ya)器(qi)(qi)連線(xian)，輸(shu)出(chu)變(bian)壓(ya)器(qi)(qi)到(dao)(dao)整(zheng)流(liu)(liu)管(guan)連接線(xian)。脈沖電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)環路(lu)盡可(ke)能小如(ru)輸(shu)入(ru)濾(lv)波(bo)電(dian)(dian)(dian)(dian)(dian)容正到(dao)(dao)變(bian)壓(ya)器(qi)(qi)到(dao)(dao)開關管(guan)返回電(dian)(dian)(dian)(dian)(dian)容負。輸(shu)出(chu)部分變(bian)壓(ya)器(qi)(qi)出(chu)端(duan)(duan)到(dao)(dao)整(zheng)流(liu)(liu)管(guan)到(dao)(dao)輸(shu)出(chu)電(dian)(dian)(dian)(dian)(dian)感到(dao)(dao)輸(shu)出(chu)電(dian)(dian)(dian)(dian)(dian)容返回變(bian)壓(ya)器(qi)(qi)電(dian)(dian)(dian)(dian)(dian)路(lu)中X電(dian)(dian)(dian)(dian)(dian)容要盡量接 近開關電(dian)(dian)(dian)(dian)(dian)源輸(shu)入(ru)端(duan)(duan)，輸(shu)入(ru)線(xian)應避免與(yu)其他(ta)電(dian)(dian)(dian)(dian)(dian)路(lu)平行，應避開。Y電(dian)(dian)(dian)(dian)(dian)容應放置(zhi)在機殼(ke)接地端(duan)(duan)子或FG連接端(duan)(duan)。共摸電(dian)(dian)(dian)(dian)(dian)感應與(yu)變(bian)壓(ya)器(qi)(qi)保(bao)持一(yi)定距離，以避免磁偶(ou)合。

　　輸出(chu)電(dian)(dian)(dian)(dian)(dian)容(rong)一(yi)般可采用兩只(zhi)一(yi)只(zhi)靠近整(zheng)流管另一(yi)只(zhi)應(ying)(ying)靠近輸出(chu)端子(zi)，可影(ying)響電(dian)(dian)(dian)(dian)(dian)源輸出(chu)紋波指標，兩只(zhi)小容(rong)量電(dian)(dian)(dian)(dian)(dian)容(rong)并聯(lian)效果應(ying)(ying)優于用一(yi)只(zhi)大(da)容(rong)量電(dian)(dian)(dian)(dian)(dian)容(rong)。發熱器(qi)件要(yao)和電(dian)(dian)(dian)(dian)(dian)解 電(dian)(dian)(dian)(dian)(dian)容(rong)保(bao)(bao)持一(yi)定(ding)距(ju)離(li)，以延長整(zheng)機(ji)壽命(ming)，電(dian)(dian)(dian)(dian)(dian)解電(dian)(dian)(dian)(dian)(dian)容(rong)是開關(guan)電(dian)(dian)(dian)(dian)(dian)源壽命(ming)的(de)瓶勁，如變壓器(qi)、功(gong)率管、大(da)功(gong)率電(dian)(dian)(dian)(dian)(dian)阻要(yao)和電(dian)(dian)(dian)(dian)(dian)解保(bao)(bao)持距(ju)離(li)，電(dian)(dian)(dian)(dian)(dian)解之(zhi)間(jian)也須留出(chu)散熱空間(jian)，條(tiao)件允許可將其(qi)放置在進風口(kou)。

　　二、印制板布線的一些原則

　　印制(zhi)(zhi)板(ban)設計(ji)時，要考慮(lv)到干擾對(dui)(dui)系統的(de)影響，將(jiang)電(dian)(dian)(dian)路(lu)(lu)(lu)的(de)模擬部(bu)(bu)(bu)分(fen)和(he)數字部(bu)(bu)(bu)分(fen)的(de)電(dian)(dian)(dian)路(lu)(lu)(lu)嚴格分(fen)開，對(dui)(dui)核心電(dian)(dian)(dian)路(lu)(lu)(lu)重點防(fang)護，將(jiang)系統地線環繞(rao)，并(bing)(bing)布(bu)線盡(jin)可能(neng)粗，電(dian)(dian)(dian)源增(zeng)加濾(lv)波電(dian)(dian)(dian)路(lu)(lu)(lu)，采(cai)用DC-DC隔離(li)，信號采(cai)用光電(dian)(dian)(dian)隔離(li)，設計(ji)隔離(li)電(dian)(dian)(dian)源，分(fen)析容易(yi)產生干擾的(de)部(bu)(bu)(bu)分(fen)（如時鐘電(dian)(dian)(dian)路(lu)(lu)(lu)、通訊電(dian)(dian)(dian)路(lu)(lu)(lu)等）和(he)容易(yi)被干擾的(de)部(bu)(bu)(bu)分(fen)（如模擬采(cai)樣(yang)電(dian)(dian)(dian)路(lu)(lu)(lu)等），對(dui)(dui)這兩種(zhong)類型的(de)電(dian)(dian)(dian)路(lu)(lu)(lu)分(fen)別采(cai)取(qu)措(cuo)施(shi)。對(dui)(dui)于干擾元(yuan)件采(cai)取(qu)抑制(zhi)(zhi)措(cuo)施(shi)，對(dui)(dui)敏感(gan)元(yuan)件采(cai)取(qu)隔離(li)和(he)保護措(cuo)施(shi)，并(bing)(bing)且將(jiang)它們在空間(jian)和(he)電(dian)(dian)(dian)氣上拉開距離(li)。在板(ban)級(ji)設計(ji)時，還要注意元(yuan)器件放置要遠離(li)印制(zhi)(zhi)板(ban)邊沿，這對(dui)(dui)防(fang)護空氣放電(dian)(dian)(dian)是有利的(de)。樣(yang)電(dian)(dian)(dian)路(lu)(lu)(lu)的(de)原理圖(tu)設計(ji)參見圖(tu)1。

　　圖(tu)1 樣電路的原理圖(tu)設計原理圖(tu)

　　線(xian)(xian)(xian)間距(ju)：隨著印制(zhi)(zhi)線(xian)(xian)(xian)路板(ban)(ban)(ban)制(zhi)(zhi)造(zao)工(gong)藝(yi)(yi)的(de)不斷完(wan)善和提高(gao)，一般加工(gong)廠(chang)(chang)制(zhi)(zhi)造(zao)出線(xian)(xian)(xian)間距(ju)等于甚至小于0.1mm已(yi)經不存在什么問題，完(wan)全(quan)能(neng)夠滿(man)(man)足大多數應用場合。考慮(lv) 到開(kai)關(guan)電源(yuan)所采(cai)用的(de)元器件(jian)及生(sheng)產(chan)工(gong)藝(yi)(yi)，一般雙面(mian)板(ban)(ban)(ban)最小線(xian)(xian)(xian)間距(ju)設(she)(she)為0.3mm，單面(mian)板(ban)(ban)(ban)最小線(xian)(xian)(xian)間距(ju)設(she)(she)為0.5mm，焊盤與焊盤、焊盤與過(guo)孔或過(guo)孔與過(guo)孔，最小 間距(ju)設(she)(she)為0.5mm，可(ke)避(bi)免在焊接(jie)操(cao)作(zuo)過(guo)程中出現“橋接(jie)”現象。，這樣大多數制(zhi)(zhi)板(ban)(ban)(ban)廠(chang)(chang)都能(neng)夠很輕松滿(man)(man)足生(sheng)產(chan)要求，并可(ke)以把成(cheng)品率控制(zhi)(zhi)得(de)非常高(gao)，亦可(ke)實現合理 的(de)布線(xian)(xian)(xian)密度及有一個較經濟的(de)成(cheng)本。