文章主要是討論和分析開(kai)關(guan)(guan)電(dian)(dian)源(yuan)(yuan)印制(zhi)(zhi)板(ban)(ban)布線原則、開(kai)關(guan)(guan)電(dian)(dian)源(yuan)(yuan)印制(zhi)(zhi)板(ban)(ban)銅皮走(zou)線的(de)(de)一些事項、開(kai)關(guan)(guan)電(dian)(dian)源(yuan)(yuan)印制(zhi)(zhi)板(ban)(ban)大電(dian)(dian)流走(zou)線的(de)(de)處理(li)以及反激電(dian)(dian)源(yuan)(yuan)反射電(dian)(dian)壓的(de)(de)一個確(que)定因(yin)素等(deng)方面，解決鋁基板(ban)(ban)在(zai)開(kai)關(guan)(guan)電(dian)(dian)源(yuan)(yuan)中的(de)(de)應用(yong)、多層印制(zhi)(zhi)板(ban)(ban)在(zai)開(kai)關(guan)(guan)電(dian)(dian)源(yuan)(yuan)電(dian)(dian)路中的(de)(de)應用(yong)的(de)(de)一些大家關(guan)(guan)注的(de)(de)問題。

　　一、引言

　　開(kai)(kai)(kai)關電(dian)源是一種(zhong)(zhong)電(dian)壓(ya)轉(zhuan)換電(dian)路(lu)(lu)(lu)，主要(yao)的工作(zuo)內容(rong)是升(sheng)壓(ya)和降壓(ya)，廣泛應用于現代電(dian)子產(chan)品。因為開(kai)(kai)(kai)關三極管總是工作(zuo)在 “開(kai)(kai)(kai)” 和“關” 的狀態，所以叫開(kai)(kai)(kai)關電(dian)源。開(kai)(kai)(kai)關電(dian)源實質就是一個振蕩(dang)電(dian)路(lu)(lu)(lu)，這種(zhong)(zhong)轉(zhuan)換電(dian)能(neng)的方式(shi)，不僅(jin)應用在電(dian)源電(dian)路(lu)(lu)(lu)，在其它(ta)的電(dian)路(lu)(lu)(lu)應用也(ye)很普遍，如液晶顯(xian)示器(qi)的背光電(dian)路(lu)(lu)(lu)、日光燈等(deng)。開(kai)(kai)(kai)關電(dian)源與變壓(ya)器(qi)相比具有(you)效率高(gao)、穩性好、體積小等(deng)優點，缺點是功率相對(dui)較小，而(er)且會對(dui)電(dian)路(lu)(lu)(lu)產(chan)生(sheng)(sheng)高(gao)頻(pin)干擾(rao)，變壓(ya)器(qi)反(fan)饋式(shi)振蕩(dang)電(dian)路(lu)(lu)(lu)，能(neng)產(chan)生(sheng)(sheng)有(you)規律的脈沖電(dian)流或電(dian)壓(ya)的電(dian)路(lu)(lu)(lu)叫振蕩(dang)電(dian)路(lu)(lu)(lu)，變壓(ya)器(qi)反(fan)饋式(shi)振蕩(dang)電(dian)路(lu)(lu)(lu)就是能(neng)滿足這種(zhong)(zhong)條件的電(dian)路(lu)(lu)(lu)。

　　開(kai)(kai)關電(dian)(dian)源(yuan)分(fen)為(wei)，隔(ge)(ge)離(li)(li)(li)與非(fei)隔(ge)(ge)離(li)(li)(li)兩種形式(shi)(shi)(shi)(shi)(shi)，在(zai)(zai)這里主要談一(yi)談隔(ge)(ge)離(li)(li)(li)式(shi)(shi)(shi)(shi)(shi)開(kai)(kai)關電(dian)(dian)源(yuan)的拓撲形式(shi)(shi)(shi)(shi)(shi)，在(zai)(zai)下文中，非(fei)特別(bie)說明(ming)，均指(zhi)隔(ge)(ge)離(li)(li)(li)電(dian)(dian)源(yuan)。隔(ge)(ge)離(li)(li)(li)電(dian)(dian)源(yuan)按照結構形式(shi)(shi)(shi)(shi)(shi)不同，可(ke)分(fen)為(wei)兩大類(lei)：正(zheng)(zheng)(zheng)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)(zai)變(bian)壓(ya)器(qi)原邊(bian)導通(tong)時副(fu)邊(bian)截止，變(bian)壓(ya)器(qi)儲能。原邊(bian)截止時，副(fu)邊(bian)導通(tong)，能量釋放(fang)到(dao)負載的工作狀態，一(yi)般常規(gui)(gui)反激式(shi)(shi)(shi)(shi)(shi)電(dian)(dian)源(yuan)單(dan)管(guan)多(duo)，雙管(guan)的不常見(jian)。正(zheng)(zheng)(zheng)激式(shi)(shi)(shi)(shi)(shi)指(zhi)在(zai)(zai)變(bian)壓(ya)器(qi)原邊(bian)導通(tong)同時副(fu)邊(bian)感(gan)應出對應電(dian)(dian)壓(ya)輸出到(dao)負載，能量通(tong)過變(bian)壓(ya)器(qi)直接(jie)傳遞。按規(gui)(gui)格又(you)可(ke)分(fen)為(wei)常規(gui)(gui)正(zheng)(zheng)(zheng)激，包括單(dan)管(guan)正(zheng)(zheng)(zheng)激，雙管(guan)正(zheng)(zheng)(zheng) 激。半橋(qiao)、橋(qiao)式(shi)(shi)(shi)(shi)(shi)電(dian)(dian)路都(dou)屬于(yu)正(zheng)(zheng)(zheng)激電(dian)(dian)路。

　　正激(ji)和(he)反激(ji)電路(lu)各有其特點，在設計電路(lu)的(de)過程中為達到最優性價比，可(ke)(ke)以靈活運(yun)用(yong)(yong)(yong)。一般在小功(gong)率場合可(ke)(ke)選用(yong)(yong)(yong)反激(ji)式(shi)(shi)。稍微大一些(xie)可(ke)(ke)采(cai)用(yong)(yong)(yong)單管正激(ji)電路(lu)，中等功(gong)率可(ke)(ke)采(cai)用(yong)(yong)(yong)雙管正激(ji)電路(lu)或(huo)半橋電路(lu)，低電壓時采(cai)用(yong)(yong)(yong)推挽(wan)電路(lu)，與半橋工作狀(zhuang)態相同。大功(gong)率輸出，一般采(cai)用(yong)(yong)(yong)橋式(shi)(shi)電路(lu)，低壓也可(ke)(ke)采(cai)用(yong)(yong)(yong)推挽(wan)電路(lu)。

　　反(fan)激式(shi)電(dian)(dian)源(yuan)(yuan)(yuan)因(yin)其(qi)結構簡單(dan)，省掉了一(yi)個和變壓器體積大(da)(da)小差不多的電(dian)(dian)感，而在(zai)中小功(gong)(gong)率(lv)電(dian)(dian)源(yuan)(yuan)(yuan)中得到(dao)(dao)(dao)廣泛的應用。在(zai)有些介紹中講到(dao)(dao)(dao)反(fan)激式(shi)電(dian)(dian)源(yuan)(yuan)(yuan)功(gong)(gong)率(lv)只能做到(dao)(dao)(dao)幾十瓦(wa)，輸出(chu)功(gong)(gong)率(lv)超過100瓦(wa)就(jiu)沒(mei)有優(you)勢，實(shi)現(xian)起來有難度(du)。本人(ren)認(ren)為(wei)一(yi)般(ban)情況下是這樣的，但也不能一(yi)概而論(lun)，PI公司(si)的TOP芯(xin)片就(jiu)可(ke)做到(dao)(dao)(dao)300瓦(wa)，有文章介紹反(fan)激電(dian)(dian)源(yuan)(yuan)(yuan)可(ke)做到(dao)(dao)(dao)上千(qian)瓦(wa)，但沒(mei)見過實(shi)物。輸出(chu)功(gong)(gong)率(lv)大(da)(da)小與輸出(chu)電(dian)(dian)壓高低(di)有關(guan)。

　　反激電(dian)(dian)源變(bian)壓器漏感是一個非(fei)常關鍵的(de)參數，由于(yu)(yu)反激電(dian)(dian)源需要(yao)變(bian)壓器儲存能量(liang)，要(yao) 使(shi)變(bian)壓器鐵(tie)芯(xin)得到充(chong)分利用，一般都要(yao)在(zai)磁(ci)路中開氣(qi)隙，其目的(de)是改變(bian)鐵(tie)芯(xin)磁(ci)滯(zhi)回線(xian)的(de)斜率，使(shi)變(bian)壓器能夠承受(shou)大(da)的(de)脈沖(chong)(chong)電(dian)(dian)流(liu)沖(chong)(chong)擊，而不(bu)至于(yu)(yu)鐵(tie)芯(xin)進入飽和非(fei)線(xian)形狀 態，磁(ci)路中氣(qi)隙處(chu)于(yu)(yu)高磁(ci)阻狀態，在(zai)磁(ci)路中產生漏磁(ci)遠(yuan)大(da)于(yu)(yu)完(wan)全閉合磁(ci)路。

　　脈(mo)沖電(dian)壓(ya)(ya)(ya)連線盡(jin)(jin)可能短，其中輸(shu)(shu)入(ru)開(kai)關管到(dao)(dao)變(bian)(bian)壓(ya)(ya)(ya)器(qi)連線，輸(shu)(shu)出(chu)變(bian)(bian)壓(ya)(ya)(ya)器(qi)到(dao)(dao)整(zheng)流(liu)管連接(jie)(jie)線。脈(mo)沖電(dian)流(liu)環(huan)路盡(jin)(jin)可能小如輸(shu)(shu)入(ru)濾波(bo)電(dian)容(rong)正到(dao)(dao)變(bian)(bian)壓(ya)(ya)(ya)器(qi)到(dao)(dao)開(kai)關管返(fan)回電(dian)容(rong)負。輸(shu)(shu)出(chu)部分變(bian)(bian)壓(ya)(ya)(ya)器(qi)出(chu)端到(dao)(dao)整(zheng)流(liu)管到(dao)(dao)輸(shu)(shu)出(chu)電(dian)感(gan)(gan)到(dao)(dao)輸(shu)(shu)出(chu)電(dian)容(rong)返(fan)回變(bian)(bian)壓(ya)(ya)(ya)器(qi)電(dian)路中X電(dian)容(rong)要盡(jin)(jin)量(liang)接(jie)(jie) 近開(kai)關電(dian)源輸(shu)(shu)入(ru)端，輸(shu)(shu)入(ru)線應避免與(yu)其他電(dian)路平行，應避開(kai)。Y電(dian)容(rong)應放置在機(ji)殼接(jie)(jie)地端子(zi)或FG連接(jie)(jie)端。共摸電(dian)感(gan)(gan)應與(yu)變(bian)(bian)壓(ya)(ya)(ya)器(qi)保持(chi)一定距離，以避免磁偶(ou)合。

　　輸(shu)出電(dian)容一(yi)(yi)般可采用(yong)兩只(zhi)一(yi)(yi)只(zhi)靠近(jin)整流管另(ling)一(yi)(yi)只(zhi)應靠近(jin)輸(shu)出端子，可影響(xiang)電(dian)源(yuan)輸(shu)出紋波指標，兩只(zhi)小容量(liang)(liang)電(dian)容并(bing)聯效果應優于(yu)用(yong)一(yi)(yi)只(zhi)大容量(liang)(liang)電(dian)容。發熱器件(jian)(jian)要和電(dian)解(jie) 電(dian)容保持一(yi)(yi)定距(ju)離，以延長整機壽命(ming)(ming)，電(dian)解(jie)電(dian)容是開關電(dian)源(yuan)壽命(ming)(ming)的瓶(ping)勁，如(ru)變壓器、功率管、大功率電(dian)阻要和電(dian)解(jie)保持距(ju)離，電(dian)解(jie)之間(jian)也須(xu)留(liu)出散熱空(kong)間(jian)，條件(jian)(jian)允許可將(jiang)其放置在進風口。

　　二、印制板布線的一些原則

　　印(yin)制(zhi)板設計(ji)(ji)(ji)時(shi)，要考(kao)慮到干擾(rao)(rao)對(dui)系(xi)統的(de)(de)(de)影(ying)響(xiang)，將(jiang)(jiang)電(dian)(dian)(dian)(dian)(dian)路的(de)(de)(de)模擬部(bu)(bu)分(fen)(fen)和數字(zi)部(bu)(bu)分(fen)(fen)的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)路嚴格(ge)分(fen)(fen)開，對(dui)核心電(dian)(dian)(dian)(dian)(dian)路重點防(fang)護，將(jiang)(jiang)系(xi)統地線(xian)環繞，并布線(xian)盡(jin)可能粗，電(dian)(dian)(dian)(dian)(dian)源(yuan)增加濾波電(dian)(dian)(dian)(dian)(dian)路，采用DC-DC隔離，信號采用光(guang)電(dian)(dian)(dian)(dian)(dian)隔離，設計(ji)(ji)(ji)隔離電(dian)(dian)(dian)(dian)(dian)源(yuan)，分(fen)(fen)析容易產生干擾(rao)(rao)的(de)(de)(de)部(bu)(bu)分(fen)(fen)（如(ru)時(shi)鐘電(dian)(dian)(dian)(dian)(dian)路、通訊(xun)電(dian)(dian)(dian)(dian)(dian)路等）和容易被干擾(rao)(rao)的(de)(de)(de)部(bu)(bu)分(fen)(fen)（如(ru)模擬采樣(yang)(yang)電(dian)(dian)(dian)(dian)(dian)路等），對(dui)這兩種類型的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)路分(fen)(fen)別采取(qu)措施。對(dui)于干擾(rao)(rao)元件采取(qu)抑制(zhi)措施，對(dui)敏感元件采取(qu)隔離和保(bao)護措施，并且將(jiang)(jiang)它(ta)們在空間(jian)和電(dian)(dian)(dian)(dian)(dian)氣(qi)(qi)上(shang)拉(la)開距離。在板級設計(ji)(ji)(ji)時(shi)，還要注意元器件放置(zhi)要遠離印(yin)制(zhi)板邊沿，這對(dui)防(fang)護空氣(qi)(qi)放電(dian)(dian)(dian)(dian)(dian)是有利的(de)(de)(de)。樣(yang)(yang)電(dian)(dian)(dian)(dian)(dian)路的(de)(de)(de)原理圖設計(ji)(ji)(ji)參見圖1。

　　圖(tu)1 樣電路的原理圖(tu)設計原理圖(tu)

　　線(xian)間(jian)距(ju)：隨(sui)著印制(zhi)線(xian)路板(ban)(ban)制(zhi)造工藝(yi)的(de)(de)(de)不斷完善和(he)提(ti)高，一般加工廠制(zhi)造出線(xian)間(jian)距(ju)等于甚至(zhi)小于0.1mm已經(jing)不存在什么問題，完全能夠(gou)滿足大多數應用(yong)場合。考慮 到開關電源(yuan)所采用(yong)的(de)(de)(de)元器件(jian)及生(sheng)產(chan)工藝(yi)，一般雙面(mian)板(ban)(ban)最(zui)小線(xian)間(jian)距(ju)設(she)(she)(she)為0.3mm，單面(mian)板(ban)(ban)最(zui)小線(xian)間(jian)距(ju)設(she)(she)(she)為0.5mm，焊(han)盤與(yu)焊(han)盤、焊(han)盤與(yu)過(guo)孔或過(guo)孔與(yu)過(guo)孔，最(zui)小 間(jian)距(ju)設(she)(she)(she)為0.5mm，可(ke)(ke)避免在焊(han)接操作過(guo)程中出現“橋(qiao)接”現象。，這樣大多數制(zhi)板(ban)(ban)廠都能夠(gou)很輕(qing)松滿足生(sheng)產(chan)要求(qiu)，并可(ke)(ke)以把成(cheng)品(pin)率(lv)控制(zhi)得非(fei)常高，亦可(ke)(ke)實現合理 的(de)(de)(de)布線(xian)密度及有一個較經(jing)濟的(de)(de)(de)成(cheng)本(ben)。