文章主要(yao)是討論(lun)和(he)分析開(kai)(kai)關電(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)印制板布線(xian)原(yuan)則、開(kai)(kai)關電(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)印制板銅皮(pi)走線(xian)的(de)一(yi)些事項、開(kai)(kai)關電(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)印制板大(da)電(dian)(dian)(dian)(dian)(dian)流走線(xian)的(de)處理以及反激(ji)電(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)反射電(dian)(dian)(dian)(dian)(dian)壓的(de)一(yi)個確定因素等方面，解決鋁(lv)基板在開(kai)(kai)關電(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)中的(de)應(ying)用(yong)、多層(ceng)印制板在開(kai)(kai)關電(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)電(dian)(dian)(dian)(dian)(dian)路中的(de)應(ying)用(yong)的(de)一(yi)些大(da)家關注的(de)問題(ti)。

　　一、引言

　　開(kai)關電(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)是(shi)一(yi)種(zhong)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)轉換電(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)，主要的(de)(de)(de)(de)工(gong)作(zuo)內容是(shi)升壓(ya)(ya)和(he)降壓(ya)(ya)，廣泛應(ying)用于現代電(dian)(dian)(dian)(dian)(dian)子(zi)產品。因為開(kai)關三極管(guan)總是(shi)工(gong)作(zuo)在 “開(kai)” 和(he)“關” 的(de)(de)(de)(de)狀態，所(suo)以(yi)叫開(kai)關電(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)。開(kai)關電(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)實質就是(shi)一(yi)個振蕩(dang)電(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)，這(zhe)種(zhong)轉換電(dian)(dian)(dian)(dian)(dian)能(neng)的(de)(de)(de)(de)方(fang)式，不僅應(ying)用在電(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)電(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)，在其它的(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)應(ying)用也(ye)很(hen)普遍(bian)，如液(ye)晶顯示器(qi)的(de)(de)(de)(de)背光電(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)、日光燈等。開(kai)關電(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)與變(bian)(bian)壓(ya)(ya)器(qi)相比具有(you)效率高、穩性好、體積小等優點，缺點是(shi)功率相對較小，而且會對電(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)產生高頻(pin)干擾，變(bian)(bian)壓(ya)(ya)器(qi)反(fan)(fan)饋(kui)式振蕩(dang)電(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)，能(neng)產生有(you)規律(lv)的(de)(de)(de)(de)脈沖電(dian)(dian)(dian)(dian)(dian)流或電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)的(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)叫振蕩(dang)電(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)，變(bian)(bian)壓(ya)(ya)器(qi)反(fan)(fan)饋(kui)式振蕩(dang)電(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)就是(shi)能(neng)滿足這(zhe)種(zhong)條件的(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)。

　　開關電(dian)(dian)源(yuan)(yuan)分(fen)(fen)為(wei)，隔(ge)離(li)與非(fei)隔(ge)離(li)兩種形式，在(zai)這里主要談(tan)(tan)一談(tan)(tan)隔(ge)離(li)式開關電(dian)(dian)源(yuan)(yuan)的(de)拓撲(pu)形式，在(zai)下文中(zhong)，非(fei)特別說明，均指(zhi)隔(ge)離(li)電(dian)(dian)源(yuan)(yuan)。隔(ge)離(li)電(dian)(dian)源(yuan)(yuan)按(an)照(zhao)結構形式不同(tong)，可分(fen)(fen)為(wei)兩大(da)類：正(zheng)(zheng)激(ji)(ji)式和(he)反(fan)激(ji)(ji)式。反(fan)激(ji)(ji)式指(zhi)在(zai)變壓器原(yuan)邊導通(tong)時(shi)副(fu)邊截止，變壓器儲(chu)能(neng)。原(yuan)邊截止時(shi)，副(fu)邊導通(tong)，能(neng)量釋放到(dao)(dao)負載的(de)工作狀態，一般常規(gui)反(fan)激(ji)(ji)式電(dian)(dian)源(yuan)(yuan)單(dan)管(guan)(guan)多，雙(shuang)管(guan)(guan)的(de)不常見(jian)。正(zheng)(zheng)激(ji)(ji)式指(zhi)在(zai)變壓器原(yuan)邊導通(tong)同(tong)時(shi)副(fu)邊感應(ying)出對應(ying)電(dian)(dian)壓輸出到(dao)(dao)負載，能(neng)量通(tong)過變壓器直接傳遞。按(an)規(gui)格又可分(fen)(fen)為(wei)常規(gui)正(zheng)(zheng)激(ji)(ji)，包括單(dan)管(guan)(guan)正(zheng)(zheng)激(ji)(ji)，雙(shuang)管(guan)(guan)正(zheng)(zheng) 激(ji)(ji)。半橋(qiao)(qiao)、橋(qiao)(qiao)式電(dian)(dian)路(lu)(lu)都屬于正(zheng)(zheng)激(ji)(ji)電(dian)(dian)路(lu)(lu)。

　　正激(ji)(ji)和(he)反激(ji)(ji)電(dian)(dian)路各有其特點，在(zai)設計電(dian)(dian)路的過(guo)程中(zhong)(zhong)為達到最優(you)性價比，可(ke)(ke)以靈活(huo)運(yun)用。一般(ban)在(zai)小功率場合可(ke)(ke)選用反激(ji)(ji)式(shi)。稍(shao)微大一些可(ke)(ke)采(cai)用單管正激(ji)(ji)電(dian)(dian)路，中(zhong)(zhong)等功率可(ke)(ke)采(cai)用雙(shuang)管正激(ji)(ji)電(dian)(dian)路或半橋電(dian)(dian)路，低電(dian)(dian)壓(ya)時采(cai)用推(tui)挽(wan)電(dian)(dian)路，與半橋工作(zuo)狀態相同。大功率輸(shu)出，一般(ban)采(cai)用橋式(shi)電(dian)(dian)路，低壓(ya)也可(ke)(ke)采(cai)用推(tui)挽(wan)電(dian)(dian)路。

　　反激(ji)式(shi)電(dian)源因(yin)其結(jie)構(gou)簡單，省掉(diao)了(le)一個和變壓(ya)器體積大小差不(bu)多的(de)電(dian)感，而在中小功率電(dian)源中得到廣泛的(de)應用(yong)。在有(you)(you)些介(jie)紹中講到反激(ji)式(shi)電(dian)源功率只能做到幾(ji)十瓦(wa)，輸出功率超過100瓦(wa)就沒(mei)有(you)(you)優勢，實現(xian)起來(lai)有(you)(you)難度。本人(ren)認為一般(ban)情況下是這(zhe)樣的(de)，但也(ye)不(bu)能一概(gai)而論，PI公司的(de)TOP芯片就可(ke)(ke)做到300瓦(wa)，有(you)(you)文章介(jie)紹反激(ji)電(dian)源可(ke)(ke)做到上千瓦(wa)，但沒(mei)見過實物。輸出功率大小與輸出電(dian)壓(ya)高低有(you)(you)關。

　　反(fan)激電源(yuan)變壓器(qi)漏感是(shi)一個非(fei)常(chang)關鍵的(de)(de)參數(shu)，由于(yu)反(fan)激電源(yuan)需要變壓器(qi)儲存能量，要 使變壓器(qi)鐵芯得(de)到(dao)充分利(li)用，一般都要在磁路(lu)中開氣(qi)隙，其目的(de)(de)是(shi)改變鐵芯磁滯回(hui)線的(de)(de)斜率，使變壓器(qi)能夠承受大的(de)(de)脈沖(chong)電流沖(chong)擊，而(er)不至于(yu)鐵芯進入飽和(he)非(fei)線形狀 態(tai)，磁路(lu)中氣(qi)隙處(chu)于(yu)高磁阻(zu)狀態(tai)，在磁路(lu)中產生漏磁遠大于(yu)完全(quan)閉合磁路(lu)。

　　脈(mo)(mo)沖(chong)(chong)電(dian)壓(ya)連(lian)線(xian)盡可能短(duan)，其(qi)中輸(shu)(shu)(shu)入開(kai)關管到(dao)變(bian)壓(ya)器(qi)連(lian)線(xian)，輸(shu)(shu)(shu)出(chu)變(bian)壓(ya)器(qi)到(dao)整流(liu)管連(lian)接線(xian)。脈(mo)(mo)沖(chong)(chong)電(dian)流(liu)環路(lu)盡可能小(xiao)如輸(shu)(shu)(shu)入濾波電(dian)容(rong)(rong)(rong)正到(dao)變(bian)壓(ya)器(qi)到(dao)開(kai)關管返回電(dian)容(rong)(rong)(rong)負。輸(shu)(shu)(shu)出(chu)部(bu)分變(bian)壓(ya)器(qi)出(chu)端(duan)到(dao)整流(liu)管到(dao)輸(shu)(shu)(shu)出(chu)電(dian)感(gan)到(dao)輸(shu)(shu)(shu)出(chu)電(dian)容(rong)(rong)(rong)返回變(bian)壓(ya)器(qi)電(dian)路(lu)中X電(dian)容(rong)(rong)(rong)要盡量接 近開(kai)關電(dian)源輸(shu)(shu)(shu)入端(duan)，輸(shu)(shu)(shu)入線(xian)應(ying)避免與(yu)其(qi)他(ta)電(dian)路(lu)平行，應(ying)避開(kai)。Y電(dian)容(rong)(rong)(rong)應(ying)放置在機殼(ke)接地端(duan)子或FG連(lian)接端(duan)。共摸電(dian)感(gan)應(ying)與(yu)變(bian)壓(ya)器(qi)保(bao)持一定(ding)距離(li)，以避免磁偶(ou)合。

　　輸(shu)出電(dian)(dian)容(rong)一(yi)般可(ke)采用兩(liang)只一(yi)只靠近整(zheng)(zheng)流管(guan)(guan)另(ling)一(yi)只應(ying)靠近輸(shu)出端子，可(ke)影響電(dian)(dian)源輸(shu)出紋(wen)波(bo)指標，兩(liang)只小(xiao)容(rong)量電(dian)(dian)容(rong)并聯效果(guo)應(ying)優于用一(yi)只大容(rong)量電(dian)(dian)容(rong)。發(fa)熱器(qi)(qi)件要(yao)和(he)電(dian)(dian)解(jie)(jie) 電(dian)(dian)容(rong)保持(chi)一(yi)定距(ju)離，以延長整(zheng)(zheng)機(ji)壽命(ming)，電(dian)(dian)解(jie)(jie)電(dian)(dian)容(rong)是開關電(dian)(dian)源壽命(ming)的瓶勁，如變壓器(qi)(qi)、功率管(guan)(guan)、大功率電(dian)(dian)阻要(yao)和(he)電(dian)(dian)解(jie)(jie)保持(chi)距(ju)離，電(dian)(dian)解(jie)(jie)之間也須(xu)留出散熱空間，條件允許可(ke)將其放(fang)置在進風(feng)口。

　　二、印制板布線的一些原則

　　印制板設(she)計(ji)時(shi)，要(yao)考(kao)慮(lv)到干擾(rao)對(dui)(dui)系統(tong)的(de)影(ying)響，將(jiang)電(dian)(dian)路(lu)(lu)的(de)模擬部(bu)分(fen)(fen)(fen)和(he)數字(zi)部(bu)分(fen)(fen)(fen)的(de)電(dian)(dian)路(lu)(lu)嚴格分(fen)(fen)(fen)開，對(dui)(dui)核(he)心電(dian)(dian)路(lu)(lu)重點防(fang)護(hu)，將(jiang)系統(tong)地線環繞，并布(bu)線盡(jin)可(ke)能粗(cu)，電(dian)(dian)源(yuan)(yuan)增加(jia)濾波(bo)電(dian)(dian)路(lu)(lu)，采用(yong)DC-DC隔離(li)，信號采用(yong)光(guang)電(dian)(dian)隔離(li)，設(she)計(ji)隔離(li)電(dian)(dian)源(yuan)(yuan)，分(fen)(fen)(fen)析容易(yi)產生干擾(rao)的(de)部(bu)分(fen)(fen)(fen)（如時(shi)鐘(zhong)電(dian)(dian)路(lu)(lu)、通訊電(dian)(dian)路(lu)(lu)等）和(he)容易(yi)被干擾(rao)的(de)部(bu)分(fen)(fen)(fen)（如模擬采樣(yang)電(dian)(dian)路(lu)(lu)等），對(dui)(dui)這兩種類(lei)型的(de)電(dian)(dian)路(lu)(lu)分(fen)(fen)(fen)別采取措施。對(dui)(dui)于干擾(rao)元件采取抑(yi)制措施，對(dui)(dui)敏(min)感元件采取隔離(li)和(he)保護(hu)措施，并且將(jiang)它們(men)在空(kong)間(jian)和(he)電(dian)(dian)氣(qi)上拉開距離(li)。在板級設(she)計(ji)時(shi)，還要(yao)注意元器件放置要(yao)遠離(li)印制板邊沿，這對(dui)(dui)防(fang)護(hu)空(kong)氣(qi)放電(dian)(dian)是有利的(de)。樣(yang)電(dian)(dian)路(lu)(lu)的(de)原(yuan)理圖設(she)計(ji)參(can)見(jian)圖1。

　　圖(tu)(tu)1 樣(yang)電(dian)路的原理圖(tu)(tu)設計原理圖(tu)(tu)

　　線(xian)間(jian)距(ju)：隨著(zhu)印制(zhi)線(xian)路板(ban)制(zhi)造(zao)工藝的不斷完(wan)善和提高(gao)，一般加工廠(chang)制(zhi)造(zao)出線(xian)間(jian)距(ju)等于(yu)甚(shen)至小(xiao)于(yu)0.1mm已經(jing)不存在什(shen)么(me)問題(ti)，完(wan)全(quan)能(neng)夠(gou)滿(man)足大多數應用場合。考慮 到開關電源(yuan)所(suo)采用的元器(qi)件及生產工藝，一般雙(shuang)面(mian)板(ban)最小(xiao)線(xian)間(jian)距(ju)設為(wei)0.3mm，單面(mian)板(ban)最小(xiao)線(xian)間(jian)距(ju)設為(wei)0.5mm，焊(han)盤與(yu)焊(han)盤、焊(han)盤與(yu)過孔或過孔與(yu)過孔，最小(xiao) 間(jian)距(ju)設為(wei)0.5mm，可避免在焊(han)接操作過程中出現(xian)“橋接”現(xian)象。，這樣大多數制(zhi)板(ban)廠(chang)都(dou)能(neng)夠(gou)很輕(qing)松滿(man)足生產要求，并可以把成品率(lv)控(kong)制(zhi)得非常高(gao)，亦可實(shi)現(xian)合理 的布線(xian)密度及有一個(ge)較經(jing)濟(ji)的成本(ben)。