臺式(shi)機(ji)電(dian)源電(dian)路圖原理(li)分析 臺式(shi)機(ji)電(dian)源是(shi)如何實現多種(zhong)保護功能的

ATX電(dian)(dian)(dian)(dian)源(yuan)的(de)控制(zhi)電(dian)(dian)(dian)(dian)路(lu)如(ru)上圖。控制(zhi)電(dian)(dian)(dian)(dian)路(lu)采(cai)用TL494及LM339集(ji)成電(dian)(dian)(dian)(dian)路(lu)（以下簡稱494和339）。494是(shi)雙(shuang)排(pai)16腳(jiao)(jiao)集(ji)成電(dian)(dian)(dian)(dian)路(lu)，工作電(dian)(dian)(dian)(dian)壓7～40V。它含有由(you)(you){14}腳(jiao)(jiao)輸(shu)(shu)出(chu)(chu)的(de)＋5V基(ji)準電(dian)(dian)(dian)(dian)源(yuan)，輸(shu)(shu)出(chu)(chu)電(dian)(dian)(dian)(dian)壓為(wei)＋5V（±0．05V），最(zui)大輸(shu)(shu)出(chu)(chu)電(dian)(dian)(dian)(dian)流250mA；一個頻(pin)(pin)率可調的(de)鋸齒波產生電(dian)(dian)(dian)(dian)路(lu)，振蕩頻(pin)(pin)率由(you)(you){5}腳(jiao)(jiao)外接電(dian)(dian)(dian)(dian)容(rong)及{6}腳(jiao)(jiao)外接電(dian)(dian)(dian)(dian)阻(zu)來決定(ding)。{13}腳(jiao)(jiao)為(wei)高電(dian)(dian)(dian)(dian)平(ping)時，由(you)(you){8}腳(jiao)(jiao)及{11}腳(jiao)(jiao)輸(shu)(shu)出(chu)(chu)雙(shuang)路(lu)反相（即推挽工作方式）的(de)脈(mo)寬調制(zhi)信號。

比較器是一(yi)種運算(suan)放大器，符號用三(san)角形表示，它有(you)一(yi)個(ge)同(tong)相(xiang)(xiang)輸入端“＋”；一(yi)個(ge)反相(xiang)(xiang)輸入端“－”和一(yi)個(ge)輸出端。

比(bi)較(jiao)器(qi)(qi)(qi)同相(xiang)(xiang)端(duan)(duan)(duan)(duan)(duan)電(dian)(dian)平(ping)(ping)(ping)(ping)若(ruo)高于反相(xiang)(xiang)端(duan)(duan)(duan)(duan)(duan)電(dian)(dian)平(ping)(ping)(ping)(ping)，則(ze)輸(shu)(shu)出(chu)(chu)(chu)端(duan)(duan)(duan)(duan)(duan)輸(shu)(shu)出(chu)(chu)(chu)高電(dian)(dian)平(ping)(ping)(ping)(ping)；反之輸(shu)(shu)出(chu)(chu)(chu)低電(dian)(dian)平(ping)(ping)(ping)(ping)。494內的(de)(de)(de)(de)(de)比(bi)較(jiao)放(fang)大器(qi)(qi)(qi)有(you)(you)(you)四個(ge)(ge)(ge)(ge)，為(wei)(wei)(wei)敘述方便，在上圖(tu)中用小寫(xie)字母a、b、c、d來表示。其中a是(shi)死(si)(si)區(qu)(qu)(qu)時(shi)間(jian)(jian)比(bi)較(jiao)器(qi)(qi)(qi)。因兩(liang)個(ge)(ge)(ge)(ge)作逆(ni)變(bian)工(gong)作的(de)(de)(de)(de)(de)三極(ji)管串聯后接(jie)(jie)到＋310V的(de)(de)(de)(de)(de)直(zhi)流電(dian)(dian)源上，若(ruo)兩(liang)個(ge)(ge)(ge)(ge)三極(ji)管同時(shi)導(dao)(dao)通(tong)，就(jiu)(jiu)會形(xing)成對直(zhi)流電(dian)(dian)源的(de)(de)(de)(de)(de)短路(lu)。兩(liang)個(ge)(ge)(ge)(ge)三極(ji)管同時(shi)導(dao)(dao)通(tong)可(ke)能(neng)發生(sheng)在一(yi)(yi)(yi)(yi)(yi)個(ge)(ge)(ge)(ge)管子從截(jie)(jie)(jie)(jie)止轉(zhuan)為(wei)(wei)(wei)導(dao)(dao)通(tong)，而另一(yi)(yi)(yi)(yi)(yi)個(ge)(ge)(ge)(ge)管子由(you)導(dao)(dao)通(tong)轉(zhuan)為(wei)(wei)(wei)截(jie)(jie)(jie)(jie)止的(de)(de)(de)(de)(de)時(shi)候。因為(wei)(wei)(wei)管子在轉(zhuan)換(huan)時(shi)有(you)(you)(you)時(shi)間(jian)(jian)的(de)(de)(de)(de)(de)延遲，截(jie)(jie)(jie)(jie)止的(de)(de)(de)(de)(de)管子已(yi)經(jing)轉(zhuan)為(wei)(wei)(wei)導(dao)(dao)通(tong)了(le)，但導(dao)(dao)通(tong)的(de)(de)(de)(de)(de)管子尚(shang)未(wei)完(wan)全轉(zhuan)為(wei)(wei)(wei)截(jie)(jie)(jie)(jie)止，于是(shi)兩(liang)個(ge)(ge)(ge)(ge)管子都(dou)呈(cheng)導(dao)(dao)通(tong)狀態(tai)而形(xing)成對直(zhi)流電(dian)(dian)源的(de)(de)(de)(de)(de)短路(lu)。為(wei)(wei)(wei)防止這(zhe)樣的(de)(de)(de)(de)(de)事(shi)情(qing)發生(sheng)，494設置了(le)死(si)(si)區(qu)(qu)(qu)時(shi)間(jian)(jian)比(bi)較(jiao)器(qi)(qi)(qi)a。從圖(tu)中可(ke)以看出(chu)(chu)(chu)，在比(bi)較(jiao)器(qi)(qi)(qi)a的(de)(de)(de)(de)(de)反相(xiang)(xiang)輸(shu)(shu)入(ru)(ru)端(duan)(duan)(duan)(duan)(duan)串聯了(le)一(yi)(yi)(yi)(yi)(yi)個(ge)(ge)(ge)(ge)“電(dian)(dian)源”，正(zheng)極(ji)接(jie)(jie)反相(xiang)(xiang)端(duan)(duan)(duan)(duan)(duan)，負極(ji)接(jie)(jie)494的(de)(de)(de)(de)(de){4}腳(jiao)。A比(bi)較(jiao)器(qi)(qi)(qi)同相(xiang)(xiang)端(duan)(duan)(duan)(duan)(duan)輸(shu)(shu)入(ru)(ru)的(de)(de)(de)(de)(de)鋸(ju)齒波(bo)信號，只有(you)(you)(you)大于“電(dian)(dian)源”電(dian)(dian)壓(ya)的(de)(de)(de)(de)(de)部分(fen)才有(you)(you)(you)輸(shu)(shu)出(chu)(chu)(chu)，在三極(ji)管導(dao)(dao)通(tong)變(bian)為(wei)(wei)(wei)截(jie)(jie)(jie)(jie)止與(yu)截(jie)(jie)(jie)(jie)止轉(zhuan)為(wei)(wei)(wei)導(dao)(dao)通(tong)期間(jian)(jian)，也就(jiu)(jiu)是(shi)死(si)(si)區(qu)(qu)(qu)時(shi)間(jian)(jian)，494沒有(you)(you)(you)脈(mo)(mo)沖輸(shu)(shu)出(chu)(chu)(chu)，避免了(le)對直(zhi)流電(dian)(dian)源的(de)(de)(de)(de)(de)短路(lu)。死(si)(si)區(qu)(qu)(qu)時(shi)間(jian)(jian)還可(ke)由(you){4}腳(jiao)外接(jie)(jie)的(de)(de)(de)(de)(de)電(dian)(dian)平(ping)(ping)(ping)(ping)來控制，{4}腳(jiao)的(de)(de)(de)(de)(de)電(dian)(dian)平(ping)(ping)(ping)(ping)上升，死(si)(si)區(qu)(qu)(qu)時(shi)間(jian)(jian)變(bian)寬，494輸(shu)(shu)出(chu)(chu)(chu)的(de)(de)(de)(de)(de)脈(mo)(mo)沖就(jiu)(jiu)變(bian)窄(zhai)了(le)，若(ruo){4}腳(jiao)的(de)(de)(de)(de)(de)電(dian)(dian)平(ping)(ping)(ping)(ping)超過了(le)鋸(ju)齒波(bo)的(de)(de)(de)(de)(de)峰值電(dian)(dian)壓(ya)，494就(jiu)(jiu)進入(ru)(ru)了(le)保護狀態(tai)，{8}腳(jiao)和{11}腳(jiao)就(jiu)(jiu)不輸(shu)(shu)出(chu)(chu)(chu)脈(mo)(mo)沖了(le)。494內部還有(you)(you)(you)3個(ge)(ge)(ge)(ge)二輸(shu)(shu)入(ru)(ru)端(duan)(duan)(duan)(duan)(duan)與(yu)門(men)（用1、2、3表示）、兩(liang)個(ge)(ge)(ge)(ge)二輸(shu)(shu)入(ru)(ru)端(duan)(duan)(duan)(duan)(duan)與(yu)非(fei)門(men)、反相(xiang)(xiang)器(qi)(qi)(qi)、T觸(chu)發器(qi)(qi)(qi)等電(dian)(dian)路(lu)。與(yu)門(men)是(shi)這(zhe)樣一(yi)(yi)(yi)(yi)(yi)種電(dian)(dian)路(lu)，只有(you)(you)(you)所有(you)(you)(you)的(de)(de)(de)(de)(de)輸(shu)(shu)入(ru)(ru)端(duan)(duan)(duan)(duan)(duan)都(dou)是(shi)高電(dian)(dian)平(ping)(ping)(ping)(ping)，輸(shu)(shu)出(chu)(chu)(chu)端(duan)(duan)(duan)(duan)(duan)才能(neng)輸(shu)(shu)出(chu)(chu)(chu)高電(dian)(dian)平(ping)(ping)(ping)(ping)；若(ruo)有(you)(you)(you)一(yi)(yi)(yi)(yi)(yi)個(ge)(ge)(ge)(ge)輸(shu)(shu)入(ru)(ru)端(duan)(duan)(duan)(duan)(duan)為(wei)(wei)(wei)低電(dian)(dian)平(ping)(ping)(ping)(ping)，則(ze)輸(shu)(shu)出(chu)(chu)(chu)端(duan)(duan)(duan)(duan)(duan)輸(shu)(shu)出(chu)(chu)(chu)低電(dian)(dian)平(ping)(ping)(ping)(ping)。反相(xiang)(xiang)器(qi)(qi)(qi)的(de)(de)(de)(de)(de)作用是(shi)把輸(shu)(shu)入(ru)(ru)信號隔離放(fang)大后反相(xiang)(xiang)輸(shu)(shu)出(chu)(chu)(chu)。與(yu)非(fei)門(men)則(ze)相(xiang)(xiang)當(dang)于一(yi)(yi)(yi)(yi)(yi)個(ge)(ge)(ge)(ge)與(yu)門(men)和一(yi)(yi)(yi)(yi)(yi)個(ge)(ge)(ge)(ge)反相(xiang)(xiang)器(qi)(qi)(qi)的(de)(de)(de)(de)(de)組合。T觸(chu)發器(qi)(qi)(qi)的(de)(de)(de)(de)(de)作用是(shi)：每輸(shu)(shu)入(ru)(ru)一(yi)(yi)(yi)(yi)(yi)個(ge)(ge)(ge)(ge)脈(mo)(mo)沖，輸(shu)(shu)出(chu)(chu)(chu)端(duan)(duan)(duan)(duan)(duan)的(de)(de)(de)(de)(de)電(dian)(dian)平(ping)(ping)(ping)(ping)就(jiu)(jiu)變(bian)化一(yi)(yi)(yi)(yi)(yi)次。如輸(shu)(shu)出(chu)(chu)(chu)端(duan)(duan)(duan)(duan)(duan)Q為(wei)(wei)(wei)低電(dian)(dian)平(ping)(ping)(ping)(ping)，輸(shu)(shu)入(ru)(ru)一(yi)(yi)(yi)(yi)(yi)個(ge)(ge)(ge)(ge)脈(mo)(mo)沖后，Q變(bian)為(wei)(wei)(wei)高電(dian)(dian)平(ping)(ping)(ping)(ping)，再輸(shu)(shu)入(ru)(ru)一(yi)(yi)(yi)(yi)(yi)個(ge)(ge)(ge)(ge)脈(mo)(mo)沖，Q又(you)回到低電(dian)(dian)平(ping)(ping)(ping)(ping)。

339是四(si)比(bi)(bi)(bi)較(jiao)(jiao)器集成電(dian)(dian)路(lu)。 LM339集成塊內部裝(zhuang)有(you)四(si)個(ge)獨(du)立的(de)(de)電(dian)(dian)壓(ya)(ya)(ya)比(bi)(bi)(bi)較(jiao)(jiao)器，每個(ge)比(bi)(bi)(bi)較(jiao)(jiao)器有(you)兩個(ge)輸(shu)(shu)入(ru)(ru)(ru)端(duan)(duan)(duan)(duan)和一(yi)個(ge)輸(shu)(shu)出(chu)(chu)端(duan)(duan)(duan)(duan)。兩個(ge)輸(shu)(shu)入(ru)(ru)(ru)端(duan)(duan)(duan)(duan)一(yi)個(ge)稱(cheng)為同相輸(shu)(shu)入(ru)(ru)(ru)端(duan)(duan)(duan)(duan)，用“+”表示，另一(yi)個(ge)稱(cheng)為反(fan)相輸(shu)(shu)入(ru)(ru)(ru)端(duan)(duan)(duan)(duan)，用“-”表示。用作比(bi)(bi)(bi)較(jiao)(jiao)兩個(ge)電(dian)(dian)壓(ya)(ya)(ya)時，任意一(yi)個(ge)輸(shu)(shu)入(ru)(ru)(ru)端(duan)(duan)(duan)(duan)加一(yi)個(ge)固定電(dian)(dian)壓(ya)(ya)(ya)做參考電(dian)(dian)壓(ya)(ya)(ya)（也稱(cheng)為門限電(dian)(dian)平，它可選(xuan)擇LM339輸(shu)(shu)入(ru)(ru)(ru)共(gong)模(mo)范圍的(de)(de)任何一(yi)點），另一(yi)端(duan)(duan)(duan)(duan)加一(yi)個(ge)待比(bi)(bi)(bi)較(jiao)(jiao)的(de)(de)信號電(dian)(dian)壓(ya)(ya)(ya)。當(dang)“+”端(duan)(duan)(duan)(duan)電(dian)(dian)壓(ya)(ya)(ya)高(gao)于(yu)(yu)(yu)“-”端(duan)(duan)(duan)(duan)時，輸(shu)(shu)出(chu)(chu)管截止，相當(dang)于(yu)(yu)(yu)輸(shu)(shu)出(chu)(chu)端(duan)(duan)(duan)(duan)開(kai)路(lu)。當(dang)“-”端(duan)(duan)(duan)(duan)電(dian)(dian)壓(ya)(ya)(ya)高(gao)于(yu)(yu)(yu)“+”端(duan)(duan)(duan)(duan)時，輸(shu)(shu)出(chu)(chu)管飽和，相當(dang)于(yu)(yu)(yu)輸(shu)(shu)出(chu)(chu)端(duan)(duan)(duan)(duan)接低電(dian)(dian)位(wei)。兩個(ge)輸(shu)(shu)入(ru)(ru)(ru)端(duan)(duan)(duan)(duan)電(dian)(dian)壓(ya)(ya)(ya)差別大于(yu)(yu)(yu)10mV就能確保(bao)輸(shu)(shu)出(chu)(chu)能從一(yi)種狀態可靠地轉換到(dao)另一(yi)種狀態， LM339的(de)(de)輸(shu)(shu)出(chu)(chu)端(duan)(duan)(duan)(duan)相當(dang)于(yu)(yu)(yu)一(yi)只(zhi)不(bu)接集電(dian)(dian)極(ji)電(dian)(dian)阻(zu)(zu)的(de)(de)晶體三(san)極(ji)管，在使用時輸(shu)(shu)出(chu)(chu)端(duan)(duan)(duan)(duan)到(dao)正電(dian)(dian)源一(yi)般須接一(yi)只(zhi)電(dian)(dian)阻(zu)(zu)（稱(cheng)為上拉(la)(la)電(dian)(dian)阻(zu)(zu)，選(xuan)3-15K）。選(xuan)不(bu)同阻(zu)(zu)值的(de)(de)上拉(la)(la)電(dian)(dian)阻(zu)(zu)會影(ying)響(xiang)輸(shu)(shu)出(chu)(chu)端(duan)(duan)(duan)(duan)高(gao)電(dian)(dian)位(wei)的(de)(de)值。因為當(dang)輸(shu)(shu)出(chu)(chu)晶體三(san)極(ji)管截止時，它的(de)(de)集電(dian)(dian)極(ji)電(dian)(dian)壓(ya)(ya)(ya)基(ji)本上取決于(yu)(yu)(yu)上拉(la)(la)電(dian)(dian)阻(zu)(zu)與負載(zai)的(de)(de)值。

按管腳的(de)順序(xu)把內部四個比(bi)較器(qi)設為A、B 、C 、D 比(bi)較器(qi)。494和339再配(pei)合其他電路，共同完成(cheng)ATX電源的(de)穩壓，產生PW－OK信號及各種保護功能。

一、 產生PW－OK信號

PC主機要求各路電源穩定之后才工作，以保護各元器件不致因電壓不穩而損壞，故設置了PW－OK信號（約＋5V），主機在獲得此信號后才開始工作。接通電源時，要求PW－OK信號比±5V、±12V、＋3．3V電源延遲數百毫秒才產生，關機時PW－OK信號應比直流電源先消失數百毫秒，以便主機先停止工作，硬盤的磁頭回復到著陸區，以保護硬盤。

ATX電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)接通市電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)后，輔助電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)立即工作(zuo)。一方面輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu) ＋5VSB電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)，同時(shi)(shi)向494的(de)(de)(de)(de){12}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)提供十幾伏到(dao)二(er)十多(duo)伏的(de)(de)(de)(de)直流(liu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)。494從(cong){14}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)＋5V基準(zhun)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)，鋸齒(chi)波振蕩器(qi)(qi)也(ye)(ye)開始起振工作(zuo)。若(ruo)主(zhu)機(ji)(ji)未開機(ji)(ji)，PS－ON信(xin)號(hao)(hao)(hao)(hao)為(wei)(wei)(wei)(wei)(wei)高電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)，經(jing)(jing)(jing)R37使339的(de)(de)(de)(de)B比(bi)(bi)(bi)較(jiao)(jiao)(jiao)器(qi)(qi){6}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)亦(yi)為(wei)(wei)(wei)(wei)(wei)高電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)，因(yin)(yin)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻R37小于(yu)R44，{6}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)高于(yu){7}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)，B比(bi)(bi)(bi)較(jiao)(jiao)(jiao)器(qi)(qi)輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)端(duan)(duan){1}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)低(di)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)，經(jing)(jing)(jing)D36的(de)(de)(de)(de)鉗位(wei)作(zuo)用，A比(bi)(bi)(bi)較(jiao)(jiao)(jiao)器(qi)(qi)的(de)(de)(de)(de)反相(xiang)端(duan)(duan){4}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)亦(yi)為(wei)(wei)(wei)(wei)(wei)低(di)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)，其電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)低(di)于(yu)同相(xiang)端(duan)(duan){5}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)的(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)，輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)端(duan)(duan){2}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)呈高電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)，經(jing)(jing)(jing)R41使494的(de)(de)(de)(de){4}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)為(wei)(wei)(wei)(wei)(wei)高電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)，故(gu)494內部的(de)(de)(de)(de)死區時(shi)(shi)間(jian)比(bi)(bi)(bi)較(jiao)(jiao)(jiao)器(qi)(qi)a輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)低(di)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)，與(yu)門1也(ye)(ye)因(yin)(yin)此(ci)輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)低(di)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)并(bing)(bing)進而(er)使與(yu)門2和(he)與(yu)門3輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)低(di)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)，封鎖(suo)了振蕩器(qi)(qi)的(de)(de)(de)(de)輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)，{8}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)、{11}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)無脈沖(chong)輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)，ATX電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)無±5V、±12V、＋3．3V電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)，主(zhu)機(ji)(ji)處(chu)于(yu)待(dai)機(ji)(ji)狀(zhuang)態(tai)。因(yin)(yin)＋5V、＋12V電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)為(wei)(wei)(wei)(wei)(wei)零(ling)，經(jing)(jing)(jing)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻R15、R16使494的(de)(de)(de)(de){1}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)亦(yi)為(wei)(wei)(wei)(wei)(wei)零(ling)，494的(de)(de)(de)(de)c比(bi)(bi)(bi)較(jiao)(jiao)(jiao)器(qi)(qi)的(de)(de)(de)(de)輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)端(duan)(duan){3}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)亦(yi)為(wei)(wei)(wei)(wei)(wei)零(ling)，經(jing)(jing)(jing)R48使339的(de)(de)(de)(de){9}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)亦(yi)為(wei)(wei)(wei)(wei)(wei)零(ling)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)，故(gu)339的(de)(de)(de)(de)C比(bi)(bi)(bi)較(jiao)(jiao)(jiao)器(qi)(qi)的(de)(de)(de)(de)輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)端(duan)(duan){14}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)為(wei)(wei)(wei)(wei)(wei)零(ling)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)。另外(wai)，339的(de)(de)(de)(de){1}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)低(di)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)信(xin)號(hao)(hao)(hao)(hao)因(yin)(yin)D34的(de)(de)(de)(de)鉗位(wei)作(zuo)用，也(ye)(ye)使{14}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)為(wei)(wei)(wei)(wei)(wei)低(di)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)，經(jing)(jing)(jing)R50和(he)R63使{11}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)亦(yi)為(wei)(wei)(wei)(wei)(wei)低(di)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)。因(yin)(yin)此(ci)D比(bi)(bi)(bi)較(jiao)(jiao)(jiao)器(qi)(qi)的(de)(de)(de)(de)輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)端(duan)(duan){13}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)為(wei)(wei)(wei)(wei)(wei)低(di)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)，也(ye)(ye)就是PW－OK信(xin)號(hao)(hao)(hao)(hao)為(wei)(wei)(wei)(wei)(wei)低(di)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)，主(zhu)機(ji)(ji)不會(hui)工作(zuo)。開啟主(zhu)機(ji)(ji)時(shi)(shi)，通過人工或遙控(kong)操作(zuo)閉(bi)合了與(yu)PS－ON相(xiang)關(guan)的(de)(de)(de)(de)開關(guan)，PS－ON呈低(di)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)，經(jing)(jing)(jing)R37使339的(de)(de)(de)(de)反相(xiang)端(duan)(duan){6}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)為(wei)(wei)(wei)(wei)(wei)低(di)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)，B比(bi)(bi)(bi)較(jiao)(jiao)(jiao)器(qi)(qi){1}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)高電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)，D35、D36反偏截止(zhi)，A比(bi)(bi)(bi)較(jiao)(jiao)(jiao)器(qi)(qi)的(de)(de)(de)(de)輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)則由{5}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)與(yu){4}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)的(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)決(jue)定(ding)。正常(chang)工作(zuo)時(shi)(shi)，{5}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)低(di)于(yu){4}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)，{2}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)低(di)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)，經(jing)(jing)(jing)R41送到(dao)494的(de)(de)(de)(de){4}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)，使{4}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)的(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)變為(wei)(wei)(wei)(wei)(wei)低(di)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)，鋸齒(chi)波振蕩信(xin)號(hao)(hao)(hao)(hao)可以(yi)從(cong)死區時(shi)(shi)間(jian)比(bi)(bi)(bi)較(jiao)(jiao)(jiao)器(qi)(qi)a輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)脈沖(chong)信(xin)號(hao)(hao)(hao)(hao)，另一方面，振蕩信(xin)號(hao)(hao)(hao)(hao)送到(dao)了PWM比(bi)(bi)(bi)較(jiao)(jiao)(jiao)器(qi)(qi)b的(de)(de)(de)(de)同相(xiang)輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)(shu)入端(duan)(duan)，PWM比(bi)(bi)(bi)較(jiao)(jiao)(jiao)器(qi)(qi)輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)的(de)(de)(de)(de)脈沖(chong)信(xin)號(hao)(hao)(hao)(hao)的(de)(de)(de)(de)寬度，則是由494的(de)(de)(de)(de){1}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)的(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)（也(ye)(ye)就是負載(zai)的(de)(de)(de)(de)大(da)小）與(yu){16}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)的(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)來決(jue)定(ding)。PWM比(bi)(bi)(bi)較(jiao)(jiao)(jiao)器(qi)(qi)輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)的(de)(de)(de)(de)脈沖(chong)信(xin)號(hao)(hao)(hao)(hao)，最后經(jing)(jing)(jing)緩沖(chong)放(fang)大(da)器(qi)(qi)放(fang)大(da)后，從(cong){8}、{11}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)脈沖(chong)信(xin)號(hao)(hao)(hao)(hao)，ATX電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)向主(zhu)機(ji)(ji)輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)±5V、±12V、＋3.3V電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)。此(ci)過程(cheng)因(yin)(yin)C35的(de)(de)(de)(de)充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)有數(shu)百毫(hao)(hao)秒的(de)(de)(de)(de)延時(shi)(shi)，但對主(zhu)機(ji)(ji)開機(ji)(ji)并(bing)(bing)無影響。494的(de)(de)(de)(de){1}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)從(cong)＋5V、＋12V經(jing)(jing)(jing)取樣電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻R15、R16得到(dao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓，其電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)略高于(yu){2}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)，{3}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)高電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)，經(jing)(jing)(jing)R48使339的(de)(de)(de)(de){9}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)得到(dao)高電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)，其電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)高于(yu){8}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)，因(yin)(yin)而(er){14}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)高電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)，此(ci)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)經(jing)(jing)(jing)R50與(yu)基準(zhun)＋5V電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)經(jing)(jing)(jing)R64共同對C39充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)，經(jing)(jing)(jing)數(shu)百毫(hao)(hao)秒后，{11}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)升到(dao)高于(yu){10}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)時(shi)(shi)，D比(bi)(bi)(bi)較(jiao)(jiao)(jiao)器(qi)(qi){13}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)高電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)，此(ci)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)經(jing)(jing)(jing)R49反饋至{11}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)，維持{11}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)處(chu)于(yu)高電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)狀(zhuang)態(tai)，故(gu){13}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)穩定(ding)的(de)(de)(de)(de)高電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping) PW－OK信(xin)號(hao)(hao)(hao)(hao)，主(zhu)機(ji)(ji)檢測到(dao)此(ci)信(xin)號(hao)(hao)(hao)(hao)后即開始正常(chang)工作(zuo)。

關機時，主機內開關(guan)(guan)(guan)使PS－ON呈高(gao)(gao)電(dian)(dian)(dian)(dian)平(ping)(ping)(ping)，此(ci)時(shi)339的(de)(de){6}腳電(dian)(dian)(dian)(dian)平(ping)(ping)(ping)高(gao)(gao)于{7}腳，{1}腳輸(shu)出(chu)低(di)電(dian)(dian)(dian)(dian)平(ping)(ping)(ping)，因二極管D34的(de)(de)鉗位(wei)作用(yong)，{14}腳呈低(di)電(dian)(dian)(dian)(dian)平(ping)(ping)(ping)，C39對C比較(jiao)器及B比較(jiao)器放(fang)(fang)(fang)電(dian)(dian)(dian)(dian)，很快{11}腳呈低(di)電(dian)(dian)(dian)(dian)平(ping)(ping)(ping)，{13}腳輸(shu)出(chu)低(di)電(dian)(dian)(dian)(dian)平(ping)(ping)(ping)，即PW－OK信(xin)號呈低(di)電(dian)(dian)(dian)(dian)平(ping)(ping)(ping)。在339的(de)(de){1}腳為(wei)低(di)電(dian)(dian)(dian)(dian)平(ping)(ping)(ping)時(shi)，經(jing)D36使{4}臆腳為(wei)低(di)電(dian)(dian)(dian)(dian)平(ping)(ping)(ping)，{2}腳輸(shu)出(chu)高(gao)(gao)電(dian)(dian)(dian)(dian)平(ping)(ping)(ping)，經(jing)R41傳(chuan)送(song)到(dao)494的(de)(de){4}腳，但因C35電(dian)(dian)(dian)(dian)位(wei)不能突變(bian)(bian)，經(jing)數(shu)百毫(hao)秒(miao)的(de)(de)放(fang)(fang)(fang)電(dian)(dian)(dian)(dian)后(hou)方(fang)使494的(de)(de){4}腳轉為(wei)高(gao)(gao)電(dian)(dian)(dian)(dian)平(ping)(ping)(ping)，從而封(feng)鎖正負脈沖的(de)(de)輸(shu)出(chu) ，主機(ji)(ji)進入待(dai)機(ji)(ji)狀(zhuang)態。上述的(de)(de)過程中，關(guan)(guan)(guan)機(ji)(ji)時(shi)C39和C35都要(yao)放(fang)(fang)(fang)電(dian)(dian)(dian)(dian)，但因放(fang)(fang)(fang)電(dian)(dian)(dian)(dian)時(shi)間(jian)常(chang)數(shu)不同(tong)，C39放(fang)(fang)(fang)電(dian)(dian)(dian)(dian)較(jiao)快，故(gu)PW－OK信(xin)號先(xian)于各電(dian)(dian)(dian)(dian)源(yuan)(yuan)(yuan)變(bian)(bian)成(cheng)低(di)電(dian)(dian)(dian)(dian)平(ping)(ping)(ping)，滿足(zu)了主機(ji)(ji)關(guan)(guan)(guan)機(ji)(ji)的(de)(de)需(xu)要(yao)。此(ci)外，關(guan)(guan)(guan)機(ji)(ji)時(shi)因各路輸(shu)出(chu)電(dian)(dian)(dian)(dian)源(yuan)(yuan)(yuan)的(de)(de)電(dian)(dian)(dian)(dian)解(jie)電(dian)(dian)(dian)(dian)容(rong)放(fang)(fang)(fang)電(dian)(dian)(dian)(dian)需(xu)要(yao)時(shi)間(jian)，也使PW－OK信(xin)號先(xian)于各電(dian)(dian)(dian)(dian)源(yuan)(yuan)(yuan)回到(dao)低(di)電(dian)(dian)(dian)(dian)平(ping)(ping)(ping)。

二、 穩壓

494的(de)(de){2}腳經R47與基準電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)＋5V相連，維持較(jiao)好(hao)的(de)(de)穩定電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)，而{1}腳則(ze)與取樣電(dian)(dian)(dian)(dian)阻R15、R16與＋5V、＋12V相連接，正常的(de)(de)情(qing)況下(xia)，{1}腳電(dian)(dian)(dian)(dian)平與{2}腳電(dian)(dian)(dian)(dian)平相等或(huo)略高(gao)(gao)。當(dang)輸(shu)(shu)出(chu)電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)升(sheng)高(gao)(gao)時（無論＋5V或(huo)＋12V），{1}腳電(dian)(dian)(dian)(dian)平高(gao)(gao)于(yu){2}腳電(dian)(dian)(dian)(dian)平，c比較(jiao)器(qi)輸(shu)(shu)出(chu)誤差電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)與鋸齒(chi)波振(zhen)蕩脈沖在(zai)PWM比較(jiao)器(qi)b進行比較(jiao)使輸(shu)(shu)出(chu)脈沖寬度(du)變窄，輸(shu)(shu)出(chu)電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)回(hui)落(luo)到標準值，反之則(ze)促使振(zhen)蕩脈沖寬度(du)增(zeng)(zeng)加，輸(shu)(shu)出(chu)電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)回(hui)升(sheng)。由于(yu)494內的(de)(de)放大(da)器(qi)增(zeng)(zeng)益很(hen)高(gao)(gao)，故穩壓(ya)(ya)(ya)精(jing)度(du)很(hen)好(hao)。從(cong)穩壓(ya)(ya)(ya)的(de)(de)原理，我們可以得到ATX電(dian)(dian)(dian)(dian)源(yuan)輸(shu)(shu)出(chu)電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)偏(pian)高(gao)(gao)或(huo)偏(pian)低(di)(di)的(de)(de)維修方法。如果輸(shu)(shu)出(chu)電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)偏(pian)低(di)(di)，可在(zai)494的(de)(de){1}腳對地并聯電(dian)(dian)(dian)(dian)阻，或(huo)是把R47的(de)(de)電(dian)(dian)(dian)(dian)阻增(zeng)(zeng)大(da)。要是電(dian)(dian)(dian)(dian)源(yuan)的(de)(de)輸(shu)(shu)出(chu)偏(pian)高(gao)(gao)，則(ze)可在(zai){2}腳對地并聯電(dian)(dian)(dian)(dian)阻，也可以用增(zeng)(zeng)大(da)R33或(huo)取下(xia)R69、R35來降低(di)(di)輸(shu)(shu)出(chu)電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)。

三、 過流保護

過(guo)流保護(hu)的(de)(de)(de)(de)(de)(de)(de)原(yuan)理(li)是基于負載愈大，Q3、Q4集電(dian)(dian)極的(de)(de)(de)(de)(de)(de)(de)脈沖(chong)(chong)(chong)電(dian)(dian)壓(ya)也(ye)愈高(gao)(gao)，也(ye)即是R13（1．5kΩ）上的(de)(de)(de)(de)(de)(de)(de)電(dian)(dian)壓(ya)也(ye)愈高(gao)(gao)，從這(zhe)里采樣(yang)經(jing)D14整流和C36濾波(bo)，再(zai)經(jing)R54、R55并(bing)聯電(dian)(dian)阻與(yu)R51、R56、R58等(deng)組成(cheng)的(de)(de)(de)(de)(de)(de)(de)分(fen)(fen)壓(ya)電(dian)(dian)路送到(dao)494的(de)(de)(de)(de)(de)(de)(de){16}腳(jiao)(jiao)(jiao)。隨著負載的(de)(de)(de)(de)(de)(de)(de)加重(zhong)，{16}腳(jiao)(jiao)(jiao)的(de)(de)(de)(de)(de)(de)(de)電(dian)(dian)平(ping)(ping)(ping)(ping)(ping)也(ye)隨之(zhi)上升(sheng)，當超(chao)過(guo){15}腳(jiao)(jiao)(jiao)的(de)(de)(de)(de)(de)(de)(de)電(dian)(dian)平(ping)(ping)(ping)(ping)(ping)時，誤差(cha)放(fang)大器輸出(chu)(chu)的(de)(de)(de)(de)(de)(de)(de)誤差(cha)電(dian)(dian)壓(ya)促使調制脈沖(chong)(chong)(chong)的(de)(de)(de)(de)(de)(de)(de)寬度變(bian)窄從而使負載電(dian)(dian)流減小。另外，從R56、R58并(bing)聯電(dian)(dian)阻獲(huo)得的(de)(de)(de)(de)(de)(de)(de)分(fen)(fen)壓(ya)再(zai)經(jing)R52送到(dao)339的(de)(de)(de)(de)(de)(de)(de){5}腳(jiao)(jiao)(jiao)，當{5}腳(jiao)(jiao)(jiao)的(de)(de)(de)(de)(de)(de)(de)電(dian)(dian)平(ping)(ping)(ping)(ping)(ping)超(chao)過(guo){4}腳(jiao)(jiao)(jiao)時，{2}腳(jiao)(jiao)(jiao)即輸出(chu)(chu)高(gao)(gao)電(dian)(dian)平(ping)(ping)(ping)(ping)(ping)送到(dao)494的(de)(de)(de)(de)(de)(de)(de){4}腳(jiao)(jiao)(jiao)，494停止輸出(chu)(chu)脈沖(chong)(chong)(chong)信(xin)號，終止±5V、±12V、＋3．3V電(dian)(dian)源的(de)(de)(de)(de)(de)(de)(de)輸出(chu)(chu)，達到(dao)過(guo)流及短路保護(hu)的(de)(de)(de)(de)(de)(de)(de)目的(de)(de)(de)(de)(de)(de)(de)。需要說(shuo)明(ming)的(de)(de)(de)(de)(de)(de)(de)是：494的(de)(de)(de)(de)(de)(de)(de){16}腳(jiao)(jiao)(jiao)電(dian)(dian)平(ping)(ping)(ping)(ping)(ping)的(de)(de)(de)(de)(de)(de)(de)高(gao)(gao)低(di)只(zhi)能(neng)改變(bian)輸出(chu)(chu)脈沖(chong)(chong)(chong)的(de)(de)(de)(de)(de)(de)(de)寬度，但不影響494的(de)(de)(de)(de)(de)(de)(de){4}腳(jiao)(jiao)(jiao)電(dian)(dian)平(ping)(ping)(ping)(ping)(ping)狀態，而339的(de)(de)(de)(de)(de)(de)(de){5}腳(jiao)(jiao)(jiao)電(dian)(dian)平(ping)(ping)(ping)(ping)(ping)一旦超(chao)過(guo){4}腳(jiao)(jiao)(jiao)的(de)(de)(de)(de)(de)(de)(de)電(dian)(dian)平(ping)(ping)(ping)(ping)(ping)，339的(de)(de)(de)(de)(de)(de)(de){2}腳(jiao)(jiao)(jiao)就送出(chu)(chu)高(gao)(gao)電(dian)(dian)平(ping)(ping)(ping)(ping)(ping)去封鎖449的(de)(de)(de)(de)(de)(de)(de)脈沖(chong)(chong)(chong)輸出(chu)(chu)，終止±5V、±12V、＋3．3V電(dian)(dian)源的(de)(de)(de)(de)(de)(de)(de)輸出(chu)(chu)，同時{2}腳(jiao)(jiao)(jiao)的(de)(de)(de)(de)(de)(de)(de)高(gao)(gao)電(dian)(dian)平(ping)(ping)(ping)(ping)(ping)經(jing)R59和二極管D39反饋到(dao){5}腳(jiao)(jiao)(jiao)，維持(chi){5}腳(jiao)(jiao)(jiao)處(chu)于高(gao)(gao)電(dian)(dian)平(ping)(ping)(ping)(ping)(ping)狀態，此時若過(guo)載或短路狀態消失，494的(de)(de)(de)(de)(de)(de)(de){4}腳(jiao)(jiao)(jiao)仍維持(chi)高(gao)(gao)電(dian)(dian)平(ping)(ping)(ping)(ping)(ping)，±5V與(yu)±12V、＋3．3V電(dian)(dian)源仍不能(neng)輸出(chu)(chu)，只(zhi)有切斷交流市電(dian)(dian)的(de)(de)(de)(de)(de)(de)(de)輸入，再(zai)重(zhong)新(xin)接通交流電(dian)(dian)，方可再(zai)次開機。

四、過壓保護

過(guo)(guo)電(dian)(dian)壓(ya)(ya)保(bao)護(hu)由R17和穩(wen)壓(ya)(ya)管Z02并聯電(dian)(dian)路從＋5V采樣，經D37送(song)到(dao)(dao)339的(de)(de){5}腳(jiao)。若(ruo)＋5V電(dian)(dian)源(yuan)(yuan)由于某種原因升(sheng)高(gao)，339的(de)(de){5}腳(jiao)電(dian)(dian)平也會(hui)隨(sui)之升(sheng)高(gao)，當超過(guo)(guo){4}腳(jiao)電(dian)(dian)平時，{2}腳(jiao)即送(song)出高(gao)電(dian)(dian)平去494的(de)(de){4}腳(jiao)，封(feng)鎖±5V、±12V、＋3．3V電(dian)(dian)源(yuan)(yuan)的(de)(de)輸出，達到(dao)(dao)過(guo)(guo)電(dian)(dian)壓(ya)(ya)保(bao)護(hu)的(de)(de)目(mu)的(de)(de)。正(zheng)常工作時，R17上(shang)的(de)(de)壓(ya)(ya)降不大，Z02截止送(song)到(dao)(dao){5}腳(jiao)的(de)(de)電(dian)(dian)壓(ya)(ya)較低，若(ruo)＋5V電(dian)(dian)源(yuan)(yuan)的(de)(de)電(dian)(dian)壓(ya)(ya)上(shang)升(sheng)，使R17上(shang)的(de)(de)壓(ya)(ya)降超過(guo)(guo)Z02的(de)(de)穩(wen)壓(ya)(ya)值，Z02導通，＋5V電(dian)(dian)源(yuan)(yuan)上(shang)升(sheng)后的(de)(de)電(dian)(dian)壓(ya)(ya)值全部加到(dao)(dao)339的(de)(de){5}腳(jiao)上(shang)，促(cu)使其快速封(feng)鎖494脈沖的(de)(de)輸出，以保(bao)護(hu)電(dian)(dian)源(yuan)(yuan)。

五、欠壓保護

欠(qian)壓(ya)(ya)(ya)保(bao)護從－5V的(de)D32及(ji)(ji)－12V處的(de)R14取(qu)樣，經R34和D37送到(dao)339的(de){5}腳(jiao)。若因(yin)某種原(yuan)因(yin)使輸(shu)出電(dian)壓(ya)(ya)(ya)過(guo)低時(shi)，－12V及(ji)(ji) －5V電(dian)壓(ya)(ya)(ya)的(de)負(fu)值(zhi)也(ye)會隨之減(jian)小，也(ye)就是電(dian)壓(ya)(ya)(ya)值(zhi)上(shang)升(sheng)(sheng)，經R34及(ji)(ji)D37送往339的(de){5}腳(jiao)使電(dian)平上(shang)升(sheng)(sheng)，339的(de){2}腳(jiao)送出高電(dian)平到(dao)494的(de){4}腳(jiao)，從而封鎖 449脈沖(chong)的(de)輸(shu)出，實現欠(qian)壓(ya)(ya)(ya)保(bao)護。二極管D32在導通(tong)時(shi)，其電(dian)壓(ya)(ya)(ya)降與(yu)通(tong)過(guo)的(de)電(dian)流基(ji)本無關，保(bao)持在0．6V～0．7V，于是－5V電(dian)壓(ya)(ya)(ya)的(de)減(jian)少量會全部傳送到(dao)D32的(de)負(fu)端，提高了欠(qian)壓(ya)(ya)(ya)保(bao)護的(de)靈敏(min)度(du)。