臺(tai)式機電(dian)源電(dian)路圖原理分析 臺(tai)式機電(dian)源是如何實現(xian)多(duo)種保護功能的

ATX電(dian)源(yuan)的(de)控(kong)制(zhi)電(dian)路(lu)如上圖(tu)。控(kong)制(zhi)電(dian)路(lu)采用TL494及(ji)LM339集成(cheng)電(dian)路(lu)（以下簡稱494和339）。494是雙(shuang)排16腳(jiao)(jiao)(jiao)集成(cheng)電(dian)路(lu)，工(gong)作電(dian)壓7～40V。它(ta)含有由{14}腳(jiao)(jiao)(jiao)輸(shu)出的(de)＋5V基(ji)準電(dian)源(yuan)，輸(shu)出電(dian)壓為(wei)＋5V（±0．05V），最大輸(shu)出電(dian)流250mA；一個頻率可調的(de)鋸齒波產生電(dian)路(lu)，振(zhen)蕩(dang)頻率由{5}腳(jiao)(jiao)(jiao)外(wai)接電(dian)容及(ji){6}腳(jiao)(jiao)(jiao)外(wai)接電(dian)阻來決定。{13}腳(jiao)(jiao)(jiao)為(wei)高電(dian)平時，由{8}腳(jiao)(jiao)(jiao)及(ji){11}腳(jiao)(jiao)(jiao)輸(shu)出雙(shuang)路(lu)反相（即推挽工(gong)作方(fang)式）的(de)脈寬調制(zhi)信號(hao)。

比較(jiao)器是(shi)一種運算放大器，符號用三角形表示(shi)，它(ta)有一個(ge)同相輸入端“＋”；一個(ge)反相輸入端“－”和一個(ge)輸出端。

比(bi)較(jiao)(jiao)器(qi)(qi)(qi)同(tong)相(xiang)(xiang)端(duan)(duan)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)若(ruo)(ruo)高于(yu)反(fan)(fan)相(xiang)(xiang)端(duan)(duan)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)，則輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)端(duan)(duan)輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)高電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)；反(fan)(fan)之(zhi)輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)低(di)(di)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)。494內的(de)(de)(de)比(bi)較(jiao)(jiao)放(fang)大器(qi)(qi)(qi)有(you)四(si)個(ge)(ge)(ge)，為(wei)(wei)敘(xu)述方便，在(zai)(zai)上(shang)圖中用小寫字母(mu)a、b、c、d來(lai)(lai)表(biao)示。其(qi)中a是(shi)死(si)(si)區(qu)(qu)時(shi)(shi)間(jian)(jian)(jian)比(bi)較(jiao)(jiao)器(qi)(qi)(qi)。因兩(liang)個(ge)(ge)(ge)作逆變(bian)工(gong)作的(de)(de)(de)三(san)(san)極(ji)管(guan)串聯后接到＋310V的(de)(de)(de)直(zhi)(zhi)流(liu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)上(shang)，若(ruo)(ruo)兩(liang)個(ge)(ge)(ge)三(san)(san)極(ji)管(guan)同(tong)時(shi)(shi)導(dao)(dao)(dao)通(tong)(tong)，就(jiu)會(hui)形(xing)成對直(zhi)(zhi)流(liu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)的(de)(de)(de)短(duan)路(lu)。兩(liang)個(ge)(ge)(ge)三(san)(san)極(ji)管(guan)同(tong)時(shi)(shi)導(dao)(dao)(dao)通(tong)(tong)可(ke)能發(fa)(fa)生在(zai)(zai)一(yi)(yi)(yi)(yi)個(ge)(ge)(ge)管(guan)子從(cong)截(jie)止(zhi)(zhi)(zhi)轉為(wei)(wei)導(dao)(dao)(dao)通(tong)(tong)，而另一(yi)(yi)(yi)(yi)個(ge)(ge)(ge)管(guan)子由導(dao)(dao)(dao)通(tong)(tong)轉為(wei)(wei)截(jie)止(zhi)(zhi)(zhi)的(de)(de)(de)時(shi)(shi)候(hou)。因為(wei)(wei)管(guan)子在(zai)(zai)轉換時(shi)(shi)有(you)時(shi)(shi)間(jian)(jian)(jian)的(de)(de)(de)延遲，截(jie)止(zhi)(zhi)(zhi)的(de)(de)(de)管(guan)子已(yi)經轉為(wei)(wei)導(dao)(dao)(dao)通(tong)(tong)了(le)(le)，但導(dao)(dao)(dao)通(tong)(tong)的(de)(de)(de)管(guan)子尚(shang)未完(wan)全轉為(wei)(wei)截(jie)止(zhi)(zhi)(zhi)，于(yu)是(shi)兩(liang)個(ge)(ge)(ge)管(guan)子都呈導(dao)(dao)(dao)通(tong)(tong)狀(zhuang)態而形(xing)成對直(zhi)(zhi)流(liu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)的(de)(de)(de)短(duan)路(lu)。為(wei)(wei)防止(zhi)(zhi)(zhi)這樣(yang)的(de)(de)(de)事(shi)情發(fa)(fa)生，494設(she)置(zhi)了(le)(le)死(si)(si)區(qu)(qu)時(shi)(shi)間(jian)(jian)(jian)比(bi)較(jiao)(jiao)器(qi)(qi)(qi)a。從(cong)圖中可(ke)以看出(chu)(chu)(chu)(chu)，在(zai)(zai)比(bi)較(jiao)(jiao)器(qi)(qi)(qi)a的(de)(de)(de)反(fan)(fan)相(xiang)(xiang)輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)入(ru)端(duan)(duan)串聯了(le)(le)一(yi)(yi)(yi)(yi)個(ge)(ge)(ge)“電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)”，正極(ji)接反(fan)(fan)相(xiang)(xiang)端(duan)(duan)，負極(ji)接494的(de)(de)(de){4}腳(jiao)(jiao)。A比(bi)較(jiao)(jiao)器(qi)(qi)(qi)同(tong)相(xiang)(xiang)端(duan)(duan)輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)入(ru)的(de)(de)(de)鋸齒(chi)波(bo)(bo)信(xin)號，只有(you)大于(yu)“電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)”電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓的(de)(de)(de)部(bu)分才有(you)輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)，在(zai)(zai)三(san)(san)極(ji)管(guan)導(dao)(dao)(dao)通(tong)(tong)變(bian)為(wei)(wei)截(jie)止(zhi)(zhi)(zhi)與截(jie)止(zhi)(zhi)(zhi)轉為(wei)(wei)導(dao)(dao)(dao)通(tong)(tong)期(qi)間(jian)(jian)(jian)，也就(jiu)是(shi)死(si)(si)區(qu)(qu)時(shi)(shi)間(jian)(jian)(jian)，494沒有(you)脈(mo)(mo)沖(chong)(chong)(chong)輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)，避免(mian)了(le)(le)對直(zhi)(zhi)流(liu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)的(de)(de)(de)短(duan)路(lu)。死(si)(si)區(qu)(qu)時(shi)(shi)間(jian)(jian)(jian)還(huan)可(ke)由{4}腳(jiao)(jiao)外接的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)來(lai)(lai)控制，{4}腳(jiao)(jiao)的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)上(shang)升，死(si)(si)區(qu)(qu)時(shi)(shi)間(jian)(jian)(jian)變(bian)寬(kuan)，494輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)的(de)(de)(de)脈(mo)(mo)沖(chong)(chong)(chong)就(jiu)變(bian)窄了(le)(le)，若(ruo)(ruo){4}腳(jiao)(jiao)的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)超過了(le)(le)鋸齒(chi)波(bo)(bo)的(de)(de)(de)峰值電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓，494就(jiu)進入(ru)了(le)(le)保護狀(zhuang)態，{8}腳(jiao)(jiao)和{11}腳(jiao)(jiao)就(jiu)不輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)脈(mo)(mo)沖(chong)(chong)(chong)了(le)(le)。494內部(bu)還(huan)有(you)3個(ge)(ge)(ge)二輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)入(ru)端(duan)(duan)與門(men)（用1、2、3表(biao)示）、兩(liang)個(ge)(ge)(ge)二輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)入(ru)端(duan)(duan)與非(fei)門(men)、反(fan)(fan)相(xiang)(xiang)器(qi)(qi)(qi)、T觸(chu)發(fa)(fa)器(qi)(qi)(qi)等(deng)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)。與門(men)是(shi)這樣(yang)一(yi)(yi)(yi)(yi)種(zhong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)，只有(you)所(suo)有(you)的(de)(de)(de)輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)入(ru)端(duan)(duan)都是(shi)高電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)，輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)端(duan)(duan)才能輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)高電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)；若(ruo)(ruo)有(you)一(yi)(yi)(yi)(yi)個(ge)(ge)(ge)輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)入(ru)端(duan)(duan)為(wei)(wei)低(di)(di)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)，則輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)端(duan)(duan)輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)低(di)(di)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)。反(fan)(fan)相(xiang)(xiang)器(qi)(qi)(qi)的(de)(de)(de)作用是(shi)把輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)入(ru)信(xin)號隔(ge)離(li)放(fang)大后反(fan)(fan)相(xiang)(xiang)輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)。與非(fei)門(men)則相(xiang)(xiang)當于(yu)一(yi)(yi)(yi)(yi)個(ge)(ge)(ge)與門(men)和一(yi)(yi)(yi)(yi)個(ge)(ge)(ge)反(fan)(fan)相(xiang)(xiang)器(qi)(qi)(qi)的(de)(de)(de)組合。T觸(chu)發(fa)(fa)器(qi)(qi)(qi)的(de)(de)(de)作用是(shi)：每輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)入(ru)一(yi)(yi)(yi)(yi)個(ge)(ge)(ge)脈(mo)(mo)沖(chong)(chong)(chong)，輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)端(duan)(duan)的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)就(jiu)變(bian)化(hua)一(yi)(yi)(yi)(yi)次。如輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)端(duan)(duan)Q為(wei)(wei)低(di)(di)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)，輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)入(ru)一(yi)(yi)(yi)(yi)個(ge)(ge)(ge)脈(mo)(mo)沖(chong)(chong)(chong)后，Q變(bian)為(wei)(wei)高電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)，再(zai)輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)入(ru)一(yi)(yi)(yi)(yi)個(ge)(ge)(ge)脈(mo)(mo)沖(chong)(chong)(chong)，Q又回到低(di)(di)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)。

339是四比(bi)(bi)較(jiao)器集成(cheng)電(dian)(dian)路。 LM339集成(cheng)塊內部裝有四個(ge)(ge)(ge)獨立的(de)(de)(de)電(dian)(dian)壓(ya)(ya)比(bi)(bi)較(jiao)器，每個(ge)(ge)(ge)比(bi)(bi)較(jiao)器有兩(liang)個(ge)(ge)(ge)輸(shu)(shu)(shu)(shu)入端(duan)(duan)和一(yi)(yi)(yi)個(ge)(ge)(ge)輸(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)端(duan)(duan)。兩(liang)個(ge)(ge)(ge)輸(shu)(shu)(shu)(shu)入端(duan)(duan)一(yi)(yi)(yi)個(ge)(ge)(ge)稱為同相(xiang)(xiang)輸(shu)(shu)(shu)(shu)入端(duan)(duan)，用“+”表示，另(ling)(ling)一(yi)(yi)(yi)個(ge)(ge)(ge)稱為反相(xiang)(xiang)輸(shu)(shu)(shu)(shu)入端(duan)(duan)，用“-”表示。用作比(bi)(bi)較(jiao)兩(liang)個(ge)(ge)(ge)電(dian)(dian)壓(ya)(ya)時(shi)(shi)，任意一(yi)(yi)(yi)個(ge)(ge)(ge)輸(shu)(shu)(shu)(shu)入端(duan)(duan)加一(yi)(yi)(yi)個(ge)(ge)(ge)固定(ding)電(dian)(dian)壓(ya)(ya)做參考電(dian)(dian)壓(ya)(ya)（也稱為門限(xian)電(dian)(dian)平，它可選(xuan)擇LM339輸(shu)(shu)(shu)(shu)入共模(mo)范圍的(de)(de)(de)任何一(yi)(yi)(yi)點），另(ling)(ling)一(yi)(yi)(yi)端(duan)(duan)加一(yi)(yi)(yi)個(ge)(ge)(ge)待比(bi)(bi)較(jiao)的(de)(de)(de)信號電(dian)(dian)壓(ya)(ya)。當(dang)“+”端(duan)(duan)電(dian)(dian)壓(ya)(ya)高于“-”端(duan)(duan)時(shi)(shi)，輸(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)管(guan)截止，相(xiang)(xiang)當(dang)于輸(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)端(duan)(duan)開(kai)路。當(dang)“-”端(duan)(duan)電(dian)(dian)壓(ya)(ya)高于“+”端(duan)(duan)時(shi)(shi)，輸(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)管(guan)飽(bao)和，相(xiang)(xiang)當(dang)于輸(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)端(duan)(duan)接(jie)低電(dian)(dian)位。兩(liang)個(ge)(ge)(ge)輸(shu)(shu)(shu)(shu)入端(duan)(duan)電(dian)(dian)壓(ya)(ya)差別大于10mV就能確(que)保輸(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)能從一(yi)(yi)(yi)種狀態(tai)可靠地轉(zhuan)換到(dao)另(ling)(ling)一(yi)(yi)(yi)種狀態(tai)， LM339的(de)(de)(de)輸(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)端(duan)(duan)相(xiang)(xiang)當(dang)于一(yi)(yi)(yi)只不(bu)接(jie)集電(dian)(dian)極電(dian)(dian)阻(zu)的(de)(de)(de)晶(jing)體三(san)(san)極管(guan)，在使用時(shi)(shi)輸(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)端(duan)(duan)到(dao)正電(dian)(dian)源一(yi)(yi)(yi)般須接(jie)一(yi)(yi)(yi)只電(dian)(dian)阻(zu)（稱為上(shang)拉(la)電(dian)(dian)阻(zu)，選(xuan)3-15K）。選(xuan)不(bu)同阻(zu)值(zhi)的(de)(de)(de)上(shang)拉(la)電(dian)(dian)阻(zu)會(hui)影(ying)響輸(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)端(duan)(duan)高電(dian)(dian)位的(de)(de)(de)值(zhi)。因為當(dang)輸(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)晶(jing)體三(san)(san)極管(guan)截止時(shi)(shi)，它的(de)(de)(de)集電(dian)(dian)極電(dian)(dian)壓(ya)(ya)基本上(shang)取(qu)決于上(shang)拉(la)電(dian)(dian)阻(zu)與(yu)負載(zai)的(de)(de)(de)值(zhi)。

按管腳的順序把內部(bu)四個比(bi)較(jiao)器設為A、B 、C 、D 比(bi)較(jiao)器。494和339再配(pei)合其他電路，共同(tong)完成ATX電源(yuan)的穩(wen)壓(ya)，產(chan)生(sheng)PW－OK信號及各(ge)種保(bao)護(hu)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)(dian)源(yuan)接通市電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)后(hou)，輔助電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)立即工(gong)作(zuo)。一方面輸(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu) ＋5VSB電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)，同時向(xiang)494的(de)(de)(de){12}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)提供十幾伏到(dao)二十多伏的(de)(de)(de)直流電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)。494從{14}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)輸(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)＋5V基準電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)，鋸齒波(bo)振(zhen)蕩(dang)器(qi)(qi)(qi)(qi)也(ye)開(kai)(kai)始起振(zhen)工(gong)作(zuo)。若主機未開(kai)(kai)機，PS－ON信(xin)(xin)(xin)(xin)號(hao)(hao)(hao)(hao)為(wei)(wei)(wei)高(gao)(gao)(gao)(gao)(gao)(gao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)，經(jing)(jing)(jing)R37使(shi)(shi)(shi)(shi)339的(de)(de)(de)B比(bi)(bi)(bi)較(jiao)器(qi)(qi)(qi)(qi){6}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)亦(yi)(yi)為(wei)(wei)(wei)高(gao)(gao)(gao)(gao)(gao)(gao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)，因(yin)電(dian)(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)(jiao)(jiao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)高(gao)(gao)(gao)(gao)(gao)(gao)于(yu){7}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)，B比(bi)(bi)(bi)較(jiao)器(qi)(qi)(qi)(qi)輸(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)端(duan)(duan){1}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)輸(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)低(di)(di)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)，經(jing)(jing)(jing)D36的(de)(de)(de)鉗位作(zuo)用(yong)(yong)，A比(bi)(bi)(bi)較(jiao)器(qi)(qi)(qi)(qi)的(de)(de)(de)反(fan)相(xiang)(xiang)端(duan)(duan){4}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)亦(yi)(yi)為(wei)(wei)(wei)低(di)(di)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)，其電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)低(di)(di)于(yu)同相(xiang)(xiang)端(duan)(duan){5}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)，輸(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)端(duan)(duan){2}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)呈高(gao)(gao)(gao)(gao)(gao)(gao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)，經(jing)(jing)(jing)R41使(shi)(shi)(shi)(shi)494的(de)(de)(de){4}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)為(wei)(wei)(wei)高(gao)(gao)(gao)(gao)(gao)(gao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)，故(gu)494內部的(de)(de)(de)死(si)區(qu)時間比(bi)(bi)(bi)較(jiao)器(qi)(qi)(qi)(qi)a輸(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)低(di)(di)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)，與(yu)(yu)門1也(ye)因(yin)此輸(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)低(di)(di)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)并(bing)進而使(shi)(shi)(shi)(shi)與(yu)(yu)門2和與(yu)(yu)門3輸(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)低(di)(di)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)，封鎖了(le)振(zhen)蕩(dang)器(qi)(qi)(qi)(qi)的(de)(de)(de)輸(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)，{8}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)、{11}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)無(wu)脈沖輸(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)，ATX電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)無(wu)±5V、±12V、＋3．3V電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)輸(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)，主機處(chu)(chu)于(yu)待機狀態。因(yin)＋5V、＋12V電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)輸(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)為(wei)(wei)(wei)零(ling)(ling)，經(jing)(jing)(jing)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻R15、R16使(shi)(shi)(shi)(shi)494的(de)(de)(de){1}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)亦(yi)(yi)為(wei)(wei)(wei)零(ling)(ling)，494的(de)(de)(de)c比(bi)(bi)(bi)較(jiao)器(qi)(qi)(qi)(qi)的(de)(de)(de)輸(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)端(duan)(duan){3}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)輸(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)亦(yi)(yi)為(wei)(wei)(wei)零(ling)(ling)，經(jing)(jing)(jing)R48使(shi)(shi)(shi)(shi)339的(de)(de)(de){9}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)亦(yi)(yi)為(wei)(wei)(wei)零(ling)(ling)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)，故(gu)339的(de)(de)(de)C比(bi)(bi)(bi)較(jiao)器(qi)(qi)(qi)(qi)的(de)(de)(de)輸(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)端(duan)(duan){14}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)為(wei)(wei)(wei)零(ling)(ling)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)。另(ling)外(wai)，339的(de)(de)(de){1}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)低(di)(di)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)信(xin)(xin)(xin)(xin)號(hao)(hao)(hao)(hao)因(yin)D34的(de)(de)(de)鉗位作(zuo)用(yong)(yong)，也(ye)使(shi)(shi)(shi)(shi){14}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)為(wei)(wei)(wei)低(di)(di)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)，經(jing)(jing)(jing)R50和R63使(shi)(shi)(shi)(shi){11}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)亦(yi)(yi)為(wei)(wei)(wei)低(di)(di)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)。因(yin)此D比(bi)(bi)(bi)較(jiao)器(qi)(qi)(qi)(qi)的(de)(de)(de)輸(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)端(duan)(duan){13}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)為(wei)(wei)(wei)低(di)(di)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)，也(ye)就(jiu)是PW－OK信(xin)(xin)(xin)(xin)號(hao)(hao)(hao)(hao)為(wei)(wei)(wei)低(di)(di)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)，主機不(bu)會工(gong)作(zuo)。開(kai)(kai)啟主機時，通過人工(gong)或遙控(kong)操作(zuo)閉(bi)合了(le)與(yu)(yu)PS－ON相(xiang)(xiang)關(guan)的(de)(de)(de)開(kai)(kai)關(guan)，PS－ON呈低(di)(di)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)，經(jing)(jing)(jing)R37使(shi)(shi)(shi)(shi)339的(de)(de)(de)反(fan)相(xiang)(xiang)端(duan)(duan){6}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)為(wei)(wei)(wei)低(di)(di)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)，B比(bi)(bi)(bi)較(jiao)器(qi)(qi)(qi)(qi){1}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)輸(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)高(gao)(gao)(gao)(gao)(gao)(gao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)，D35、D36反(fan)偏截止，A比(bi)(bi)(bi)較(jiao)器(qi)(qi)(qi)(qi)的(de)(de)(de)輸(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)則由(you)(you){5}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)與(yu)(yu){4}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)決定(ding)。正(zheng)常工(gong)作(zuo)時，{5}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)低(di)(di)于(yu){4}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)，{2}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)輸(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)低(di)(di)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)，經(jing)(jing)(jing)R41送到(dao)494的(de)(de)(de){4}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)，使(shi)(shi)(shi)(shi){4}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)變為(wei)(wei)(wei)低(di)(di)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)，鋸齒波(bo)振(zhen)蕩(dang)信(xin)(xin)(xin)(xin)號(hao)(hao)(hao)(hao)可以從死(si)區(qu)時間比(bi)(bi)(bi)較(jiao)器(qi)(qi)(qi)(qi)a輸(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)脈沖信(xin)(xin)(xin)(xin)號(hao)(hao)(hao)(hao)，另(ling)一方面，振(zhen)蕩(dang)信(xin)(xin)(xin)(xin)號(hao)(hao)(hao)(hao)送到(dao)了(le)PWM比(bi)(bi)(bi)較(jiao)器(qi)(qi)(qi)(qi)b的(de)(de)(de)同相(xiang)(xiang)輸(shu)(shu)(shu)(shu)(shu)(shu)入端(duan)(duan)，PWM比(bi)(bi)(bi)較(jiao)器(qi)(qi)(qi)(qi)輸(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)的(de)(de)(de)脈沖信(xin)(xin)(xin)(xin)號(hao)(hao)(hao)(hao)的(de)(de)(de)寬度，則是由(you)(you)494的(de)(de)(de){1}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)（也(ye)就(jiu)是負載的(de)(de)(de)大(da)小）與(yu)(yu){16}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)來決定(ding)。PWM比(bi)(bi)(bi)較(jiao)器(qi)(qi)(qi)(qi)輸(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)的(de)(de)(de)脈沖信(xin)(xin)(xin)(xin)號(hao)(hao)(hao)(hao)，最后(hou)經(jing)(jing)(jing)緩沖放大(da)器(qi)(qi)(qi)(qi)放大(da)后(hou)，從{8}、{11}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)輸(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)脈沖信(xin)(xin)(xin)(xin)號(hao)(hao)(hao)(hao)，ATX電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)向(xiang)主機輸(shu)(shu)(shu)(shu)(shu)(shu)出(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)(dian)源(yuan)。此過程因(yin)C35的(de)(de)(de)充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)有數(shu)(shu)百毫(hao)秒的(de)(de)(de)延時，但對主機開(kai)(kai)機并(bing)無(wu)影響。494的(de)(de)(de){1}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)從＋5V、＋12V經(jing)(jing)(jing)取樣電(dian)(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)(dian)壓，其電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)略(lve)高(gao)(gao)(gao)(gao)(gao)(gao)于(yu){2}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)，{3}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)輸(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)高(gao)(gao)(gao)(gao)(gao)(gao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)，經(jing)(jing)(jing)R48使(shi)(shi)(shi)(shi)339的(de)(de)(de){9}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)得到(dao)高(gao)(gao)(gao)(gao)(gao)(gao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)，其電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)高(gao)(gao)(gao)(gao)(gao)(gao)于(yu){8}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)，因(yin)而{14}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)輸(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)高(gao)(gao)(gao)(gao)(gao)(gao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)，此電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)經(jing)(jing)(jing)R50與(yu)(yu)基準＋5V電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(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)(dian)，經(jing)(jing)(jing)數(shu)(shu)百毫(hao)秒后(hou)，{11}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)升到(dao)高(gao)(gao)(gao)(gao)(gao)(gao)于(yu){10}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)時，D比(bi)(bi)(bi)較(jiao)器(qi)(qi)(qi)(qi){13}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)輸(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)高(gao)(gao)(gao)(gao)(gao)(gao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)，此電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)經(jing)(jing)(jing)R49反(fan)饋(kui)至{11}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)，維持(chi){11}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)處(chu)(chu)于(yu)高(gao)(gao)(gao)(gao)(gao)(gao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)狀態，故(gu){13}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)輸(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)穩定(ding)的(de)(de)(de)高(gao)(gao)(gao)(gao)(gao)(gao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping) PW－OK信(xin)(xin)(xin)(xin)號(hao)(hao)(hao)(hao)，主機檢測到(dao)此信(xin)(xin)(xin)(xin)號(hao)(hao)(hao)(hao)后(hou)即開(kai)(kai)始正(zheng)常工(gong)作(zuo)。

關機時，主機內開關(guan)使(shi)PS－ON呈(cheng)(cheng)高電(dian)(dian)(dian)平(ping)，此時339的(de)(de)(de){6}腳(jiao)(jiao)電(dian)(dian)(dian)平(ping)高于(yu){7}腳(jiao)(jiao)，{1}腳(jiao)(jiao)輸(shu)(shu)出(chu)(chu)低(di)電(dian)(dian)(dian)平(ping)，因二極管D34的(de)(de)(de)鉗位作用，{14}腳(jiao)(jiao)呈(cheng)(cheng)低(di)電(dian)(dian)(dian)平(ping)，C39對C比較器及B比較器放電(dian)(dian)(dian)，很快{11}腳(jiao)(jiao)呈(cheng)(cheng)低(di)電(dian)(dian)(dian)平(ping)，{13}腳(jiao)(jiao)輸(shu)(shu)出(chu)(chu)低(di)電(dian)(dian)(dian)平(ping)，即PW－OK信(xin)號呈(cheng)(cheng)低(di)電(dian)(dian)(dian)平(ping)。在339的(de)(de)(de){1}腳(jiao)(jiao)為(wei)低(di)電(dian)(dian)(dian)平(ping)時，經D36使(shi){4}臆腳(jiao)(jiao)為(wei)低(di)電(dian)(dian)(dian)平(ping)，{2}腳(jiao)(jiao)輸(shu)(shu)出(chu)(chu)高電(dian)(dian)(dian)平(ping)，經R41傳送到(dao)494的(de)(de)(de){4}腳(jiao)(jiao)，但因C35電(dian)(dian)(dian)位不能(neng)突變，經數百(bai)毫秒的(de)(de)(de)放電(dian)(dian)(dian)后方使(shi)494的(de)(de)(de){4}腳(jiao)(jiao)轉(zhuan)為(wei)高電(dian)(dian)(dian)平(ping)，從而(er)封鎖(suo)正負脈沖的(de)(de)(de)輸(shu)(shu)出(chu)(chu) ，主機(ji)(ji)進(jin)入待機(ji)(ji)狀態(tai)。上述的(de)(de)(de)過(guo)程(cheng)中(zhong)，關(guan)機(ji)(ji)時C39和(he)C35都要(yao)放電(dian)(dian)(dian)，但因放電(dian)(dian)(dian)時間(jian)常數不同，C39放電(dian)(dian)(dian)較快，故PW－OK信(xin)號先于(yu)各電(dian)(dian)(dian)源(yuan)變成低(di)電(dian)(dian)(dian)平(ping)，滿足了主機(ji)(ji)關(guan)機(ji)(ji)的(de)(de)(de)需要(yao)。此外，關(guan)機(ji)(ji)時因各路(lu)輸(shu)(shu)出(chu)(chu)電(dian)(dian)(dian)源(yuan)的(de)(de)(de)電(dian)(dian)(dian)解電(dian)(dian)(dian)容放電(dian)(dian)(dian)需要(yao)時間(jian)，也(ye)使(shi)PW－OK信(xin)號先于(yu)各電(dian)(dian)(dian)源(yuan)回到(dao)低(di)電(dian)(dian)(dian)平(ping)。

二、 穩壓

494的{2}腳(jiao)經R47與(yu)(yu)基準電(dian)壓(ya)＋5V相連(lian)，維持較(jiao)好的穩(wen)定電(dian)壓(ya)，而{1}腳(jiao)則(ze)與(yu)(yu)取(qu)樣電(dian)阻R15、R16與(yu)(yu)＋5V、＋12V相連(lian)接，正常的情況下，{1}腳(jiao)電(dian)平(ping)與(yu)(yu){2}腳(jiao)電(dian)平(ping)相等或略高(gao)(gao)(gao)。當輸(shu)出(chu)電(dian)壓(ya)升高(gao)(gao)(gao)時（無論＋5V或＋12V），{1}腳(jiao)電(dian)平(ping)高(gao)(gao)(gao)于{2}腳(jiao)電(dian)平(ping)，c比(bi)較(jiao)器(qi)輸(shu)出(chu)誤差(cha)電(dian)壓(ya)與(yu)(yu)鋸齒波振(zhen)蕩脈(mo)沖在(zai)PWM比(bi)較(jiao)器(qi)b進行(xing)比(bi)較(jiao)使輸(shu)出(chu)脈(mo)沖寬度(du)變窄，輸(shu)出(chu)電(dian)壓(ya)回(hui)落到(dao)標準值，反之(zhi)則(ze)促使振(zhen)蕩脈(mo)沖寬度(du)增(zeng)加，輸(shu)出(chu)電(dian)壓(ya)回(hui)升。由于494內(nei)的放大器(qi)增(zeng)益很(hen)(hen)高(gao)(gao)(gao)，故穩(wen)壓(ya)精度(du)很(hen)(hen)好。從穩(wen)壓(ya)的原理，我們可(ke)以得(de)到(dao)ATX電(dian)源輸(shu)出(chu)電(dian)壓(ya)偏高(gao)(gao)(gao)或偏低的維修方法。如(ru)果輸(shu)出(chu)電(dian)壓(ya)偏低，可(ke)在(zai)494的{1}腳(jiao)對地并聯電(dian)阻，或是把(ba)R47的電(dian)阻增(zeng)大。要是電(dian)源的輸(shu)出(chu)偏高(gao)(gao)(gao)，則(ze)可(ke)在(zai){2}腳(jiao)對地并聯電(dian)阻，也(ye)可(ke)以用(yong)增(zeng)大R33或取(qu)下R69、R35來降低輸(shu)出(chu)電(dian)壓(ya)。

三、 過流保護

過(guo)流保護的(de)(de)(de)原(yuan)理(li)是基于負載愈大(da)，Q3、Q4集電(dian)(dian)(dian)(dian)極(ji)的(de)(de)(de)脈(mo)沖(chong)電(dian)(dian)(dian)(dian)壓也(ye)(ye)愈高(gao)(gao)，也(ye)(ye)即是R13（1．5kΩ）上的(de)(de)(de)電(dian)(dian)(dian)(dian)壓也(ye)(ye)愈高(gao)(gao)，從這里采(cai)樣經(jing)D14整(zheng)流和(he)C36濾波，再經(jing)R54、R55并聯電(dian)(dian)(dian)(dian)阻(zu)(zu)與(yu)R51、R56、R58等組成的(de)(de)(de)分壓電(dian)(dian)(dian)(dian)路(lu)(lu)送(song)到(dao)494的(de)(de)(de){16}腳(jiao)(jiao)(jiao)(jiao)。隨著負載的(de)(de)(de)加重，{16}腳(jiao)(jiao)(jiao)(jiao)的(de)(de)(de)電(dian)(dian)(dian)(dian)平(ping)(ping)也(ye)(ye)隨之上升，當超過(guo){15}腳(jiao)(jiao)(jiao)(jiao)的(de)(de)(de)電(dian)(dian)(dian)(dian)平(ping)(ping)時，誤差放大(da)器(qi)輸(shu)(shu)(shu)出的(de)(de)(de)誤差電(dian)(dian)(dian)(dian)壓促使(shi)調(diao)制脈(mo)沖(chong)的(de)(de)(de)寬(kuan)度(du)變窄從而(er)使(shi)負載電(dian)(dian)(dian)(dian)流減小。另外，從R56、R58并聯電(dian)(dian)(dian)(dian)阻(zu)(zu)獲得(de)的(de)(de)(de)分壓再經(jing)R52送(song)到(dao)339的(de)(de)(de){5}腳(jiao)(jiao)(jiao)(jiao)，當{5}腳(jiao)(jiao)(jiao)(jiao)的(de)(de)(de)電(dian)(dian)(dian)(dian)平(ping)(ping)超過(guo){4}腳(jiao)(jiao)(jiao)(jiao)時，{2}腳(jiao)(jiao)(jiao)(jiao)即輸(shu)(shu)(shu)出高(gao)(gao)電(dian)(dian)(dian)(dian)平(ping)(ping)送(song)到(dao)494的(de)(de)(de){4}腳(jiao)(jiao)(jiao)(jiao)，494停止輸(shu)(shu)(shu)出脈(mo)沖(chong)信(xin)號，終止±5V、±12V、＋3．3V電(dian)(dian)(dian)(dian)源(yuan)的(de)(de)(de)輸(shu)(shu)(shu)出，達到(dao)過(guo)流及短路(lu)(lu)保護的(de)(de)(de)目(mu)的(de)(de)(de)。需要說明的(de)(de)(de)是：494的(de)(de)(de){16}腳(jiao)(jiao)(jiao)(jiao)電(dian)(dian)(dian)(dian)平(ping)(ping)的(de)(de)(de)高(gao)(gao)低(di)只(zhi)(zhi)能改變輸(shu)(shu)(shu)出脈(mo)沖(chong)的(de)(de)(de)寬(kuan)度(du)，但(dan)不影響494的(de)(de)(de){4}腳(jiao)(jiao)(jiao)(jiao)電(dian)(dian)(dian)(dian)平(ping)(ping)狀(zhuang)態(tai)，而(er)339的(de)(de)(de){5}腳(jiao)(jiao)(jiao)(jiao)電(dian)(dian)(dian)(dian)平(ping)(ping)一(yi)旦超過(guo){4}腳(jiao)(jiao)(jiao)(jiao)的(de)(de)(de)電(dian)(dian)(dian)(dian)平(ping)(ping)，339的(de)(de)(de){2}腳(jiao)(jiao)(jiao)(jiao)就送(song)出高(gao)(gao)電(dian)(dian)(dian)(dian)平(ping)(ping)去封(feng)鎖449的(de)(de)(de)脈(mo)沖(chong)輸(shu)(shu)(shu)出，終止±5V、±12V、＋3．3V電(dian)(dian)(dian)(dian)源(yuan)的(de)(de)(de)輸(shu)(shu)(shu)出，同時{2}腳(jiao)(jiao)(jiao)(jiao)的(de)(de)(de)高(gao)(gao)電(dian)(dian)(dian)(dian)平(ping)(ping)經(jing)R59和(he)二(er)極(ji)管D39反饋到(dao){5}腳(jiao)(jiao)(jiao)(jiao)，維(wei)(wei)持{5}腳(jiao)(jiao)(jiao)(jiao)處于高(gao)(gao)電(dian)(dian)(dian)(dian)平(ping)(ping)狀(zhuang)態(tai)，此時若(ruo)過(guo)載或短路(lu)(lu)狀(zhuang)態(tai)消失，494的(de)(de)(de){4}腳(jiao)(jiao)(jiao)(jiao)仍(reng)維(wei)(wei)持高(gao)(gao)電(dian)(dian)(dian)(dian)平(ping)(ping)，±5V與(yu)±12V、＋3．3V電(dian)(dian)(dian)(dian)源(yuan)仍(reng)不能輸(shu)(shu)(shu)出，只(zhi)(zhi)有(you)切斷交流市電(dian)(dian)(dian)(dian)的(de)(de)(de)輸(shu)(shu)(shu)入，再重新接(jie)通交流電(dian)(dian)(dian)(dian)，方可再次開機(ji)。

四、過壓保護

過(guo)(guo)電(dian)(dian)(dian)(dian)壓(ya)保(bao)(bao)護由(you)R17和穩壓(ya)管Z02并聯(lian)電(dian)(dian)(dian)(dian)路(lu)從＋5V采樣(yang)，經(jing)D37送(song)到(dao)339的(de)(de)(de)(de)(de)(de){5}腳(jiao)(jiao)(jiao)。若(ruo)＋5V電(dian)(dian)(dian)(dian)源(yuan)由(you)于某種原因升高(gao)，339的(de)(de)(de)(de)(de)(de){5}腳(jiao)(jiao)(jiao)電(dian)(dian)(dian)(dian)平(ping)也會隨之升高(gao)，當超(chao)過(guo)(guo){4}腳(jiao)(jiao)(jiao)電(dian)(dian)(dian)(dian)平(ping)時(shi)，{2}腳(jiao)(jiao)(jiao)即送(song)出(chu)高(gao)電(dian)(dian)(dian)(dian)平(ping)去494的(de)(de)(de)(de)(de)(de){4}腳(jiao)(jiao)(jiao)，封鎖±5V、±12V、＋3．3V電(dian)(dian)(dian)(dian)源(yuan)的(de)(de)(de)(de)(de)(de)輸出(chu)，達(da)到(dao)過(guo)(guo)電(dian)(dian)(dian)(dian)壓(ya)保(bao)(bao)護的(de)(de)(de)(de)(de)(de)目(mu)的(de)(de)(de)(de)(de)(de)。正常工作時(shi)，R17上(shang)(shang)的(de)(de)(de)(de)(de)(de)壓(ya)降不大，Z02截止(zhi)送(song)到(dao){5}腳(jiao)(jiao)(jiao)的(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)壓(ya)較低，若(ruo)＋5V電(dian)(dian)(dian)(dian)源(yuan)的(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)壓(ya)上(shang)(shang)升，使R17上(shang)(shang)的(de)(de)(de)(de)(de)(de)壓(ya)降超(chao)過(guo)(guo)Z02的(de)(de)(de)(de)(de)(de)穩壓(ya)值(zhi)，Z02導(dao)通，＋5V電(dian)(dian)(dian)(dian)源(yuan)上(shang)(shang)升后的(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)壓(ya)值(zhi)全部加(jia)到(dao)339的(de)(de)(de)(de)(de)(de){5}腳(jiao)(jiao)(jiao)上(shang)(shang)，促使其快(kuai)速封鎖494脈沖(chong)的(de)(de)(de)(de)(de)(de)輸出(chu)，以保(bao)(bao)護電(dian)(dian)(dian)(dian)源(yuan)。

五、欠壓保護

欠(qian)壓保(bao)護從－5V的(de)D32及－12V處的(de)R14取樣，經R34和D37送(song)(song)到339的(de){5}腳。若因某種(zhong)原因使(shi)輸出(chu)電(dian)(dian)壓過低時(shi)，－12V及 －5V電(dian)(dian)壓的(de)負(fu)值也會隨之(zhi)減小(xiao)，也就是電(dian)(dian)壓值上升，經R34及D37送(song)(song)往339的(de){5}腳使(shi)電(dian)(dian)平(ping)上升，339的(de){2}腳送(song)(song)出(chu)高電(dian)(dian)平(ping)到494的(de){4}腳，從而(er)封鎖 449脈沖(chong)的(de)輸出(chu)，實現欠(qian)壓保(bao)護。二(er)極管D32在(zai)導(dao)通時(shi)，其電(dian)(dian)壓降與通過的(de)電(dian)(dian)流(liu)基本無關，保(bao)持(chi)在(zai)0．6V～0．7V，于是－5V電(dian)(dian)壓的(de)減少(shao)量會全部傳送(song)(song)到D32的(de)負(fu)端，提高了(le)欠(qian)壓保(bao)護的(de)靈敏度。