文章主要是討論(lun)和分析開(kai)關(guan)電(dian)源(yuan)(yuan)(yuan)(yuan)印制(zhi)板布線(xian)原(yuan)則、開(kai)關(guan)電(dian)源(yuan)(yuan)(yuan)(yuan)印制(zhi)板銅皮走線(xian)的(de)一(yi)些(xie)事(shi)項、開(kai)關(guan)電(dian)源(yuan)(yuan)(yuan)(yuan)印制(zhi)板大電(dian)流走線(xian)的(de)處理以及反激電(dian)源(yuan)(yuan)(yuan)(yuan)反射電(dian)壓的(de)一(yi)個確定因(yin)素等方面(mian)，解決鋁基板在開(kai)關(guan)電(dian)源(yuan)(yuan)(yuan)(yuan)中(zhong)的(de)應用、多層印制(zhi)板在開(kai)關(guan)電(dian)源(yuan)(yuan)(yuan)(yuan)電(dian)路中(zhong)的(de)應用的(de)一(yi)些(xie)大家(jia)關(guan)注(zhu)的(de)問題(ti)。

　　一、引言

　　開關(guan)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源是(shi)(shi)(shi)一種(zhong)(zhong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)轉換(huan)(huan)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)，主(zhu)要的(de)(de)工(gong)(gong)作內容是(shi)(shi)(shi)升壓(ya)(ya)(ya)和降(jiang)壓(ya)(ya)(ya)，廣(guang)泛應用于現代電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)子產品。因為開關(guan)三極管(guan)總是(shi)(shi)(shi)工(gong)(gong)作在(zai)(zai) “開” 和“關(guan)” 的(de)(de)狀態，所以叫開關(guan)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源。開關(guan)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源實質就(jiu)(jiu)是(shi)(shi)(shi)一個振(zhen)(zhen)蕩(dang)(dang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)，這種(zhong)(zhong)轉換(huan)(huan)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)能(neng)的(de)(de)方式(shi)(shi)，不僅應用在(zai)(zai)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)，在(zai)(zai)其它的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)應用也很普遍，如(ru)液晶顯示(shi)器(qi)的(de)(de)背光電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)、日光燈(deng)等(deng)。開關(guan)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源與變壓(ya)(ya)(ya)器(qi)相比(bi)具有效率高、穩性好、體積小(xiao)等(deng)優點(dian)，缺點(dian)是(shi)(shi)(shi)功(gong)率相對(dui)較小(xiao)，而且會對(dui)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)產生高頻干擾，變壓(ya)(ya)(ya)器(qi)反(fan)饋式(shi)(shi)振(zhen)(zhen)蕩(dang)(dang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)，能(neng)產生有規律的(de)(de)脈沖電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流或電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)叫振(zhen)(zhen)蕩(dang)(dang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)，變壓(ya)(ya)(ya)器(qi)反(fan)饋式(shi)(shi)振(zhen)(zhen)蕩(dang)(dang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)就(jiu)(jiu)是(shi)(shi)(shi)能(neng)滿足這種(zhong)(zhong)條件(jian)的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)。

　　開(kai)關電源(yuan)分(fen)為，隔離(li)與非(fei)隔離(li)兩種形(xing)(xing)式(shi)，在這里主要談(tan)(tan)一談(tan)(tan)隔離(li)式(shi)開(kai)關電源(yuan)的拓(tuo)撲形(xing)(xing)式(shi)，在下文中，非(fei)特別說明(ming)，均(jun)指隔離(li)電源(yuan)。隔離(li)電源(yuan)按(an)照(zhao)結構形(xing)(xing)式(shi)不(bu)同(tong)(tong)，可(ke)分(fen)為兩大類：正(zheng)激(ji)式(shi)和反激(ji)式(shi)。反激(ji)式(shi)指在變(bian)(bian)壓(ya)器原(yuan)(yuan)邊(bian)(bian)導(dao)通時(shi)副邊(bian)(bian)截(jie)止(zhi)(zhi)，變(bian)(bian)壓(ya)器儲能(neng)。原(yuan)(yuan)邊(bian)(bian)截(jie)止(zhi)(zhi)時(shi)，副邊(bian)(bian)導(dao)通，能(neng)量釋放到負載的工作狀(zhuang)態(tai)，一般常規反激(ji)式(shi)電源(yuan)單(dan)管(guan)多，雙管(guan)的不(bu)常見(jian)。正(zheng)激(ji)式(shi)指在變(bian)(bian)壓(ya)器原(yuan)(yuan)邊(bian)(bian)導(dao)通同(tong)(tong)時(shi)副邊(bian)(bian)感應出對應電壓(ya)輸出到負載，能(neng)量通過(guo)變(bian)(bian)壓(ya)器直接(jie)傳遞。按(an)規格又(you)可(ke)分(fen)為常規正(zheng)激(ji)，包括單(dan)管(guan)正(zheng)激(ji)，雙管(guan)正(zheng) 激(ji)。半橋(qiao)、橋(qiao)式(shi)電路都(dou)屬(shu)于正(zheng)激(ji)電路。

　　正(zheng)(zheng)激(ji)和反激(ji)電(dian)(dian)(dian)(dian)(dian)路(lu)(lu)各有其(qi)特點，在設計電(dian)(dian)(dian)(dian)(dian)路(lu)(lu)的過程(cheng)中為達到最優性價比，可以靈(ling)活運用(yong)(yong)。一般在小功率(lv)場合可選用(yong)(yong)反激(ji)式。稍微大一些可采(cai)用(yong)(yong)單管(guan)正(zheng)(zheng)激(ji)電(dian)(dian)(dian)(dian)(dian)路(lu)(lu)，中等功率(lv)可采(cai)用(yong)(yong)雙管(guan)正(zheng)(zheng)激(ji)電(dian)(dian)(dian)(dian)(dian)路(lu)(lu)或半橋(qiao)電(dian)(dian)(dian)(dian)(dian)路(lu)(lu)，低電(dian)(dian)(dian)(dian)(dian)壓時采(cai)用(yong)(yong)推(tui)挽(wan)電(dian)(dian)(dian)(dian)(dian)路(lu)(lu)，與半橋(qiao)工作狀態相同(tong)。大功率(lv)輸出，一般采(cai)用(yong)(yong)橋(qiao)式電(dian)(dian)(dian)(dian)(dian)路(lu)(lu)，低壓也可采(cai)用(yong)(yong)推(tui)挽(wan)電(dian)(dian)(dian)(dian)(dian)路(lu)(lu)。

　　反(fan)激(ji)式電(dian)源因其(qi)結構簡單，省掉了一個和變壓器體積大小(xiao)差不多(duo)的(de)電(dian)感，而在中(zhong)小(xiao)功率(lv)電(dian)源中(zhong)得到(dao)(dao)廣泛(fan)的(de)應用(yong)。在有(you)(you)些(xie)介紹中(zhong)講(jiang)到(dao)(dao)反(fan)激(ji)式電(dian)源功率(lv)只(zhi)能做到(dao)(dao)幾十瓦(wa)，輸(shu)出功率(lv)超過100瓦(wa)就沒有(you)(you)優勢(shi)，實(shi)現(xian)起來有(you)(you)難度(du)。本(ben)人認為一般(ban)情(qing)況(kuang)下是(shi)這樣的(de)，但也不能一概(gai)而論，PI公司(si)的(de)TOP芯片就可做到(dao)(dao)300瓦(wa)，有(you)(you)文(wen)章介紹反(fan)激(ji)電(dian)源可做到(dao)(dao)上千(qian)瓦(wa)，但沒見(jian)過實(shi)物。輸(shu)出功率(lv)大小(xiao)與(yu)輸(shu)出電(dian)壓高(gao)低有(you)(you)關。

　　反激(ji)電源(yuan)變(bian)(bian)壓器漏感是一個(ge)非常關鍵的(de)參(can)數，由于(yu)反激(ji)電源(yuan)需要變(bian)(bian)壓器儲存能量，要 使(shi)變(bian)(bian)壓器鐵(tie)(tie)(tie)芯得到充分利用，一般都(dou)要在磁(ci)(ci)(ci)路中開氣隙(xi)，其目的(de)是改變(bian)(bian)鐵(tie)(tie)(tie)芯磁(ci)(ci)(ci)滯回(hui)線(xian)的(de)斜率，使(shi)變(bian)(bian)壓器能夠(gou)承受(shou)大的(de)脈沖(chong)電流沖(chong)擊，而不至于(yu)鐵(tie)(tie)(tie)芯進入飽和非線(xian)形狀(zhuang) 態，磁(ci)(ci)(ci)路中氣隙(xi)處于(yu)高磁(ci)(ci)(ci)阻狀(zhuang)態，在磁(ci)(ci)(ci)路中產生漏磁(ci)(ci)(ci)遠(yuan)大于(yu)完全閉合磁(ci)(ci)(ci)路。

　　脈沖電(dian)(dian)(dian)壓連(lian)線盡(jin)(jin)可(ke)(ke)能短，其中輸(shu)入(ru)開關管(guan)到(dao)變(bian)壓器(qi)(qi)連(lian)線，輸(shu)出(chu)變(bian)壓器(qi)(qi)到(dao)整流管(guan)連(lian)接(jie)線。脈沖電(dian)(dian)(dian)流環路盡(jin)(jin)可(ke)(ke)能小如輸(shu)入(ru)濾波電(dian)(dian)(dian)容(rong)正到(dao)變(bian)壓器(qi)(qi)到(dao)開關管(guan)返回電(dian)(dian)(dian)容(rong)負。輸(shu)出(chu)部分變(bian)壓器(qi)(qi)出(chu)端(duan)到(dao)整流管(guan)到(dao)輸(shu)出(chu)電(dian)(dian)(dian)感到(dao)輸(shu)出(chu)電(dian)(dian)(dian)容(rong)返回變(bian)壓器(qi)(qi)電(dian)(dian)(dian)路中X電(dian)(dian)(dian)容(rong)要盡(jin)(jin)量接(jie) 近開關電(dian)(dian)(dian)源輸(shu)入(ru)端(duan)，輸(shu)入(ru)線應(ying)(ying)避免(mian)與(yu)其他電(dian)(dian)(dian)路平行，應(ying)(ying)避開。Y電(dian)(dian)(dian)容(rong)應(ying)(ying)放置在(zai)機(ji)殼接(jie)地(di)端(duan)子或FG連(lian)接(jie)端(duan)。共摸電(dian)(dian)(dian)感應(ying)(ying)與(yu)變(bian)壓器(qi)(qi)保持一定距離(li)，以(yi)避免(mian)磁偶合。

　　輸(shu)出(chu)電(dian)容一(yi)般可采用兩只一(yi)只靠近整(zheng)流管另一(yi)只應靠近輸(shu)出(chu)端子，可影響電(dian)源(yuan)輸(shu)出(chu)紋波指標，兩只小容量電(dian)容并聯效果應優于(yu)用一(yi)只大容量電(dian)容。發(fa)熱器件(jian)要和(he)電(dian)解(jie)(jie) 電(dian)容保持(chi)一(yi)定距離(li)，以延長整(zheng)機壽命，電(dian)解(jie)(jie)電(dian)容是開關電(dian)源(yuan)壽命的瓶勁，如變壓器、功(gong)率管、大功(gong)率電(dian)阻要和(he)電(dian)解(jie)(jie)保持(chi)距離(li)，電(dian)解(jie)(jie)之(zhi)間(jian)也須留出(chu)散熱空間(jian)，條件(jian)允許(xu)可將其放置在進風口。

　　二、印制板布線的一些原則

　　印制(zhi)板(ban)設計時，要(yao)考慮到干擾(rao)對(dui)系統的(de)影響，將電(dian)(dian)路(lu)的(de)模擬部(bu)(bu)分(fen)(fen)和(he)數字(zi)部(bu)(bu)分(fen)(fen)的(de)電(dian)(dian)路(lu)嚴格分(fen)(fen)開，對(dui)核心電(dian)(dian)路(lu)重(zhong)點防護，將系統地線環繞，并(bing)布(bu)線盡可(ke)能粗，電(dian)(dian)源增加濾波(bo)電(dian)(dian)路(lu)，采(cai)用(yong)DC-DC隔(ge)離(li)，信號采(cai)用(yong)光電(dian)(dian)隔(ge)離(li)，設計隔(ge)離(li)電(dian)(dian)源，分(fen)(fen)析容易產生干擾(rao)的(de)部(bu)(bu)分(fen)(fen)（如(ru)時鐘電(dian)(dian)路(lu)、通訊電(dian)(dian)路(lu)等）和(he)容易被(bei)干擾(rao)的(de)部(bu)(bu)分(fen)(fen)（如(ru)模擬采(cai)樣(yang)電(dian)(dian)路(lu)等），對(dui)這兩種(zhong)類型的(de)電(dian)(dian)路(lu)分(fen)(fen)別(bie)采(cai)取(qu)措(cuo)施。對(dui)于干擾(rao)元件采(cai)取(qu)抑(yi)制(zhi)措(cuo)施，對(dui)敏感(gan)元件采(cai)取(qu)隔(ge)離(li)和(he)保護措(cuo)施，并(bing)且將它們在空間(jian)和(he)電(dian)(dian)氣上拉(la)開距離(li)。在板(ban)級(ji)設計時，還(huan)要(yao)注意元器件放(fang)置要(yao)遠離(li)印制(zhi)板(ban)邊沿(yan)，這對(dui)防護空氣放(fang)電(dian)(dian)是(shi)有利的(de)。樣(yang)電(dian)(dian)路(lu)的(de)原理圖設計參見(jian)圖1。

　　圖1 樣電路的原理圖設計原理圖

　　線(xian)(xian)間(jian)(jian)(jian)(jian)距(ju)(ju)：隨著(zhu)印制(zhi)(zhi)(zhi)(zhi)線(xian)(xian)路板(ban)制(zhi)(zhi)(zhi)(zhi)造(zao)工(gong)藝的不斷完善和提(ti)高，一般加工(gong)廠制(zhi)(zhi)(zhi)(zhi)造(zao)出線(xian)(xian)間(jian)(jian)(jian)(jian)距(ju)(ju)等于甚至小(xiao)于0.1mm已經(jing)不存在什么問題，完全能夠(gou)滿(man)足大多(duo)數(shu)應(ying)用(yong)場(chang)合(he)。考慮(lv) 到開關(guan)電源所采用(yong)的元(yuan)器件及生產(chan)工(gong)藝，一般雙面板(ban)最小(xiao)線(xian)(xian)間(jian)(jian)(jian)(jian)距(ju)(ju)設(she)為(wei)0.3mm，單面板(ban)最小(xiao)線(xian)(xian)間(jian)(jian)(jian)(jian)距(ju)(ju)設(she)為(wei)0.5mm，焊(han)盤與焊(han)盤、焊(han)盤與過(guo)孔(kong)或過(guo)孔(kong)與過(guo)孔(kong)，最小(xiao) 間(jian)(jian)(jian)(jian)距(ju)(ju)設(she)為(wei)0.5mm，可避免在焊(han)接(jie)操作過(guo)程(cheng)中出現“橋接(jie)”現象。，這樣大多(duo)數(shu)制(zhi)(zhi)(zhi)(zhi)板(ban)廠都能夠(gou)很輕松滿(man)足生產(chan)要求，并(bing)可以把(ba)成(cheng)品率控制(zhi)(zhi)(zhi)(zhi)得非(fei)常高，亦可實現合(he)理 的布(bu)線(xian)(xian)密度及有一個較經(jing)濟(ji)的成(cheng)本。