臺(tai)式機電源電路(lu)圖(tu)原理分析 臺(tai)式機電源是(shi)如何實現(xian)多種保護(hu)功(gong)能的

ATX電(dian)(dian)源(yuan)的控(kong)制電(dian)(dian)路(lu)如(ru)上圖(tu)。控(kong)制電(dian)(dian)路(lu)采(cai)用(yong)TL494及(ji)LM339集成(cheng)電(dian)(dian)路(lu)（以下(xia)簡稱494和339）。494是雙(shuang)排16腳(jiao)(jiao)集成(cheng)電(dian)(dian)路(lu)，工(gong)作電(dian)(dian)壓(ya)7～40V。它(ta)含(han)有由(you){14}腳(jiao)(jiao)輸出的＋5V基(ji)準電(dian)(dian)源(yuan)，輸出電(dian)(dian)壓(ya)為＋5V（±0．05V），最大輸出電(dian)(dian)流250mA；一個頻率(lv)可(ke)調的鋸齒波(bo)產生電(dian)(dian)路(lu)，振蕩頻率(lv)由(you){5}腳(jiao)(jiao)外接電(dian)(dian)容及(ji){6}腳(jiao)(jiao)外接電(dian)(dian)阻來(lai)決定(ding)。{13}腳(jiao)(jiao)為高電(dian)(dian)平時，由(you){8}腳(jiao)(jiao)及(ji){11}腳(jiao)(jiao)輸出雙(shuang)路(lu)反相（即推挽工(gong)作方式(shi)）的脈寬(kuan)調制信(xin)號。

比(bi)較(jiao)器(qi)是一(yi)(yi)(yi)(yi)種運(yun)算放大器(qi)，符號用三角形(xing)表(biao)示，它有一(yi)(yi)(yi)(yi)個同相(xiang)(xiang)輸入端(duan)“＋”；一(yi)(yi)(yi)(yi)個反相(xiang)(xiang)輸入端(duan)“－”和一(yi)(yi)(yi)(yi)個輸出端(duan)。

比(bi)較(jiao)器(qi)(qi)同相(xiang)(xiang)(xiang)端(duan)(duan)(duan)(duan)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)若(ruo)(ruo)高(gao)(gao)(gao)(gao)于反相(xiang)(xiang)(xiang)端(duan)(duan)(duan)(duan)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)，則輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)端(duan)(duan)(duan)(duan)輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)高(gao)(gao)(gao)(gao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)；反之(zhi)輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)低電(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)。494內的(de)(de)(de)(de)比(bi)較(jiao)放(fang)大(da)器(qi)(qi)有(you)(you)四個(ge)(ge)，為(wei)(wei)敘述方便(bian)，在(zai)(zai)上(shang)圖(tu)中用(yong)(yong)(yong)小寫字母(mu)a、b、c、d來表示。其中a是死(si)區時間(jian)(jian)比(bi)較(jiao)器(qi)(qi)。因兩個(ge)(ge)作逆變(bian)工作的(de)(de)(de)(de)三極(ji)管(guan)(guan)(guan)串(chuan)聯后(hou)接(jie)到＋310V的(de)(de)(de)(de)直流(liu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)上(shang)，若(ruo)(ruo)兩個(ge)(ge)三極(ji)管(guan)(guan)(guan)同時導(dao)通(tong)(tong)，就(jiu)(jiu)會形成對直流(liu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)的(de)(de)(de)(de)短路。兩個(ge)(ge)三極(ji)管(guan)(guan)(guan)同時導(dao)通(tong)(tong)可(ke)能發生(sheng)在(zai)(zai)一(yi)(yi)個(ge)(ge)管(guan)(guan)(guan)子從截(jie)止(zhi)(zhi)轉為(wei)(wei)導(dao)通(tong)(tong)，而另一(yi)(yi)個(ge)(ge)管(guan)(guan)(guan)子由導(dao)通(tong)(tong)轉為(wei)(wei)截(jie)止(zhi)(zhi)的(de)(de)(de)(de)時候。因為(wei)(wei)管(guan)(guan)(guan)子在(zai)(zai)轉換時有(you)(you)時間(jian)(jian)的(de)(de)(de)(de)延(yan)遲，截(jie)止(zhi)(zhi)的(de)(de)(de)(de)管(guan)(guan)(guan)子已經轉為(wei)(wei)導(dao)通(tong)(tong)了，但(dan)導(dao)通(tong)(tong)的(de)(de)(de)(de)管(guan)(guan)(guan)子尚(shang)未(wei)完(wan)全轉為(wei)(wei)截(jie)止(zhi)(zhi)，于是兩個(ge)(ge)管(guan)(guan)(guan)子都(dou)(dou)呈導(dao)通(tong)(tong)狀態而形成對直流(liu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)的(de)(de)(de)(de)短路。為(wei)(wei)防(fang)止(zhi)(zhi)這樣(yang)的(de)(de)(de)(de)事情發生(sheng)，494設(she)置了死(si)區時間(jian)(jian)比(bi)較(jiao)器(qi)(qi)a。從圖(tu)中可(ke)以看出(chu)(chu)(chu)(chu)，在(zai)(zai)比(bi)較(jiao)器(qi)(qi)a的(de)(de)(de)(de)反相(xiang)(xiang)(xiang)輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)(shu)入(ru)(ru)(ru)端(duan)(duan)(duan)(duan)串(chuan)聯了一(yi)(yi)個(ge)(ge)“電(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)”，正極(ji)接(jie)反相(xiang)(xiang)(xiang)端(duan)(duan)(duan)(duan)，負極(ji)接(jie)494的(de)(de)(de)(de){4}腳。A比(bi)較(jiao)器(qi)(qi)同相(xiang)(xiang)(xiang)端(duan)(duan)(duan)(duan)輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)(shu)入(ru)(ru)(ru)的(de)(de)(de)(de)鋸(ju)齒波信號(hao)，只有(you)(you)大(da)于“電(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)”電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)的(de)(de)(de)(de)部分才(cai)有(you)(you)輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)，在(zai)(zai)三極(ji)管(guan)(guan)(guan)導(dao)通(tong)(tong)變(bian)為(wei)(wei)截(jie)止(zhi)(zhi)與(yu)截(jie)止(zhi)(zhi)轉為(wei)(wei)導(dao)通(tong)(tong)期間(jian)(jian)，也就(jiu)(jiu)是死(si)區時間(jian)(jian)，494沒有(you)(you)脈(mo)沖(chong)(chong)輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)，避免了對直流(liu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)的(de)(de)(de)(de)短路。死(si)區時間(jian)(jian)還可(ke)由{4}腳外接(jie)的(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)來控(kong)制，{4}腳的(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)上(shang)升，死(si)區時間(jian)(jian)變(bian)寬，494輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)的(de)(de)(de)(de)脈(mo)沖(chong)(chong)就(jiu)(jiu)變(bian)窄了，若(ruo)(ruo){4}腳的(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)超過(guo)了鋸(ju)齒波的(de)(de)(de)(de)峰值(zhi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)，494就(jiu)(jiu)進(jin)入(ru)(ru)(ru)了保護狀態，{8}腳和{11}腳就(jiu)(jiu)不(bu)輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)脈(mo)沖(chong)(chong)了。494內部還有(you)(you)3個(ge)(ge)二輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)(shu)入(ru)(ru)(ru)端(duan)(duan)(duan)(duan)與(yu)門(men)（用(yong)(yong)(yong)1、2、3表示）、兩個(ge)(ge)二輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)(shu)入(ru)(ru)(ru)端(duan)(duan)(duan)(duan)與(yu)非門(men)、反相(xiang)(xiang)(xiang)器(qi)(qi)、T觸發器(qi)(qi)等電(dian)(dian)(dian)(dian)(dian)(dian)(dian)路。與(yu)門(men)是這樣(yang)一(yi)(yi)種電(dian)(dian)(dian)(dian)(dian)(dian)(dian)路，只有(you)(you)所有(you)(you)的(de)(de)(de)(de)輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)(shu)入(ru)(ru)(ru)端(duan)(duan)(duan)(duan)都(dou)(dou)是高(gao)(gao)(gao)(gao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)，輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)端(duan)(duan)(duan)(duan)才(cai)能輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)高(gao)(gao)(gao)(gao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)；若(ruo)(ruo)有(you)(you)一(yi)(yi)個(ge)(ge)輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)(shu)入(ru)(ru)(ru)端(duan)(duan)(duan)(duan)為(wei)(wei)低電(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)，則輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)端(duan)(duan)(duan)(duan)輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)低電(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)。反相(xiang)(xiang)(xiang)器(qi)(qi)的(de)(de)(de)(de)作用(yong)(yong)(yong)是把輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)(shu)入(ru)(ru)(ru)信號(hao)隔離放(fang)大(da)后(hou)反相(xiang)(xiang)(xiang)輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)。與(yu)非門(men)則相(xiang)(xiang)(xiang)當于一(yi)(yi)個(ge)(ge)與(yu)門(men)和一(yi)(yi)個(ge)(ge)反相(xiang)(xiang)(xiang)器(qi)(qi)的(de)(de)(de)(de)組合。T觸發器(qi)(qi)的(de)(de)(de)(de)作用(yong)(yong)(yong)是：每輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)(shu)入(ru)(ru)(ru)一(yi)(yi)個(ge)(ge)脈(mo)沖(chong)(chong)，輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)端(duan)(duan)(duan)(duan)的(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)就(jiu)(jiu)變(bian)化(hua)一(yi)(yi)次。如輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)端(duan)(duan)(duan)(duan)Q為(wei)(wei)低電(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)，輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)(shu)入(ru)(ru)(ru)一(yi)(yi)個(ge)(ge)脈(mo)沖(chong)(chong)后(hou)，Q變(bian)為(wei)(wei)高(gao)(gao)(gao)(gao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)，再輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)(shu)入(ru)(ru)(ru)一(yi)(yi)個(ge)(ge)脈(mo)沖(chong)(chong)，Q又回(hui)到低電(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)。

339是四比較(jiao)器(qi)集成(cheng)電(dian)(dian)(dian)(dian)(dian)路(lu)。 LM339集成(cheng)塊(kuai)內部(bu)裝(zhuang)有(you)四個(ge)獨立的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)壓(ya)比較(jiao)器(qi)，每個(ge)比較(jiao)器(qi)有(you)兩個(ge)輸(shu)(shu)(shu)入(ru)端(duan)(duan)(duan)(duan)和一(yi)(yi)個(ge)輸(shu)(shu)(shu)出(chu)(chu)(chu)(chu)端(duan)(duan)(duan)(duan)。兩個(ge)輸(shu)(shu)(shu)入(ru)端(duan)(duan)(duan)(duan)一(yi)(yi)個(ge)稱(cheng)(cheng)為(wei)(wei)同(tong)相輸(shu)(shu)(shu)入(ru)端(duan)(duan)(duan)(duan)，用(yong)“+”表示(shi)，另一(yi)(yi)個(ge)稱(cheng)(cheng)為(wei)(wei)反(fan)相輸(shu)(shu)(shu)入(ru)端(duan)(duan)(duan)(duan)，用(yong)“-”表示(shi)。用(yong)作比較(jiao)兩個(ge)電(dian)(dian)(dian)(dian)(dian)壓(ya)時(shi)(shi)，任(ren)意一(yi)(yi)個(ge)輸(shu)(shu)(shu)入(ru)端(duan)(duan)(duan)(duan)加一(yi)(yi)個(ge)固定電(dian)(dian)(dian)(dian)(dian)壓(ya)做參考電(dian)(dian)(dian)(dian)(dian)壓(ya)（也稱(cheng)(cheng)為(wei)(wei)門限電(dian)(dian)(dian)(dian)(dian)平，它可選(xuan)擇LM339輸(shu)(shu)(shu)入(ru)共模范圍的(de)(de)(de)任(ren)何一(yi)(yi)點），另一(yi)(yi)端(duan)(duan)(duan)(duan)加一(yi)(yi)個(ge)待比較(jiao)的(de)(de)(de)信號電(dian)(dian)(dian)(dian)(dian)壓(ya)。當(dang)“+”端(duan)(duan)(duan)(duan)電(dian)(dian)(dian)(dian)(dian)壓(ya)高(gao)于(yu)(yu)(yu)“-”端(duan)(duan)(duan)(duan)時(shi)(shi)，輸(shu)(shu)(shu)出(chu)(chu)(chu)(chu)管截止，相當(dang)于(yu)(yu)(yu)輸(shu)(shu)(shu)出(chu)(chu)(chu)(chu)端(duan)(duan)(duan)(duan)開路(lu)。當(dang)“-”端(duan)(duan)(duan)(duan)電(dian)(dian)(dian)(dian)(dian)壓(ya)高(gao)于(yu)(yu)(yu)“+”端(duan)(duan)(duan)(duan)時(shi)(shi)，輸(shu)(shu)(shu)出(chu)(chu)(chu)(chu)管飽和，相當(dang)于(yu)(yu)(yu)輸(shu)(shu)(shu)出(chu)(chu)(chu)(chu)端(duan)(duan)(duan)(duan)接低電(dian)(dian)(dian)(dian)(dian)位。兩個(ge)輸(shu)(shu)(shu)入(ru)端(duan)(duan)(duan)(duan)電(dian)(dian)(dian)(dian)(dian)壓(ya)差別(bie)大于(yu)(yu)(yu)10mV就能確保輸(shu)(shu)(shu)出(chu)(chu)(chu)(chu)能從一(yi)(yi)種狀態(tai)(tai)可靠地轉換到另一(yi)(yi)種狀態(tai)(tai)， LM339的(de)(de)(de)輸(shu)(shu)(shu)出(chu)(chu)(chu)(chu)端(duan)(duan)(duan)(duan)相當(dang)于(yu)(yu)(yu)一(yi)(yi)只不接集電(dian)(dian)(dian)(dian)(dian)極(ji)電(dian)(dian)(dian)(dian)(dian)阻的(de)(de)(de)晶體三(san)極(ji)管，在使(shi)用(yong)時(shi)(shi)輸(shu)(shu)(shu)出(chu)(chu)(chu)(chu)端(duan)(duan)(duan)(duan)到正電(dian)(dian)(dian)(dian)(dian)源(yuan)一(yi)(yi)般(ban)須接一(yi)(yi)只電(dian)(dian)(dian)(dian)(dian)阻（稱(cheng)(cheng)為(wei)(wei)上(shang)拉(la)(la)(la)電(dian)(dian)(dian)(dian)(dian)阻，選(xuan)3-15K）。選(xuan)不同(tong)阻值的(de)(de)(de)上(shang)拉(la)(la)(la)電(dian)(dian)(dian)(dian)(dian)阻會影響(xiang)輸(shu)(shu)(shu)出(chu)(chu)(chu)(chu)端(duan)(duan)(duan)(duan)高(gao)電(dian)(dian)(dian)(dian)(dian)位的(de)(de)(de)值。因為(wei)(wei)當(dang)輸(shu)(shu)(shu)出(chu)(chu)(chu)(chu)晶體三(san)極(ji)管截止時(shi)(shi)，它的(de)(de)(de)集電(dian)(dian)(dian)(dian)(dian)極(ji)電(dian)(dian)(dian)(dian)(dian)壓(ya)基(ji)本上(shang)取決(jue)于(yu)(yu)(yu)上(shang)拉(la)(la)(la)電(dian)(dian)(dian)(dian)(dian)阻與負載(zai)的(de)(de)(de)值。

按管腳(jiao)的順(shun)序(xu)把內部四(si)個(ge)比較器設為A、B 、C 、D 比較器。494和339再配合其他電(dian)路，共同(tong)完成ATX電(dian)源的穩壓(ya)，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)(dian)源(yuan)接通(tong)市(shi)電(dian)(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)(dian)源(yuan)立即(ji)工作(zuo)(zuo)。一(yi)方(fang)面輸(shu)(shu)(shu)(shu)(shu)(shu)出(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(shi)向494的(de)(de)(de)(de)(de){12}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)提(ti)供十幾伏到(dao)(dao)二十多伏的(de)(de)(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(cong){14}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)輸(shu)(shu)(shu)(shu)(shu)(shu)出(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(ju)齒波(bo)振(zhen)蕩(dang)器(qi)也(ye)開(kai)(kai)始(shi)起振(zhen)工作(zuo)(zuo)。若主(zhu)機(ji)(ji)未開(kai)(kai)機(ji)(ji)，PS－ON信(xin)(xin)(xin)(xin)(xin)號(hao)(hao)(hao)(hao)(hao)(hao)為(wei)高(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)R37使339的(de)(de)(de)(de)(de)B比(bi)較(jiao)(jiao)器(qi){6}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)亦(yi)為(wei)高(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)，因電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)R37小(xiao)于(yu)(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)于(yu)(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)較(jiao)(jiao)器(qi)輸(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)端{1}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)輸(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)低(di)(di)(di)(di)(di)(di)(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)D36的(de)(de)(de)(de)(de)鉗位作(zuo)(zuo)用(yong)，A比(bi)較(jiao)(jiao)器(qi)的(de)(de)(de)(de)(de)反相端{4}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)亦(yi)為(wei)低(di)(di)(di)(di)(di)(di)(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)(di)(di)(di)(di)(di)(di)于(yu)(yu)同相端{5}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)的(de)(de)(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)端{2}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)呈高(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)R41使494的(de)(de)(de)(de)(de){4}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)為(wei)高(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494內部(bu)的(de)(de)(de)(de)(de)死區時(shi)間比(bi)較(jiao)(jiao)器(qi)a輸(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)低(di)(di)(di)(di)(di)(di)(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)，與門1也(ye)因此(ci)(ci)輸(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)低(di)(di)(di)(di)(di)(di)(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)并進而使與門2和與門3輸(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)低(di)(di)(di)(di)(di)(di)(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(feng)鎖(suo)了(le)振(zhen)蕩(dang)器(qi)的(de)(de)(de)(de)(de)輸(shu)(shu)(shu)(shu)(shu)(shu)出(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)無脈沖(chong)(chong)輸(shu)(shu)(shu)(shu)(shu)(shu)出(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±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)，主(zhu)機(ji)(ji)處于(yu)(yu)待機(ji)(ji)狀態。因＋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)為(wei)零，經(jing)(jing)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)R15、R16使494的(de)(de)(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)為(wei)零，494的(de)(de)(de)(de)(de)c比(bi)較(jiao)(jiao)器(qi)的(de)(de)(de)(de)(de)輸(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)端{3}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)輸(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)亦(yi)為(wei)零，經(jing)(jing)R48使339的(de)(de)(de)(de)(de){9}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)亦(yi)為(wei)零電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)，故339的(de)(de)(de)(de)(de)C比(bi)較(jiao)(jiao)器(qi)的(de)(de)(de)(de)(de)輸(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)端{14}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)為(wei)零電(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)(de)(de){1}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)低(di)(di)(di)(di)(di)(di)(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)(xin)號(hao)(hao)(hao)(hao)(hao)(hao)因D34的(de)(de)(de)(de)(de)鉗位作(zuo)(zuo)用(yong)，也(ye)使{14}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)為(wei)低(di)(di)(di)(di)(di)(di)(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)R50和R63使{11}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)亦(yi)為(wei)低(di)(di)(di)(di)(di)(di)(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)。因此(ci)(ci)D比(bi)較(jiao)(jiao)器(qi)的(de)(de)(de)(de)(de)輸(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)端{13}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)為(wei)低(di)(di)(di)(di)(di)(di)(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)就是PW－OK信(xin)(xin)(xin)(xin)(xin)號(hao)(hao)(hao)(hao)(hao)(hao)為(wei)低(di)(di)(di)(di)(di)(di)(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(zhu)機(ji)(ji)不會工作(zuo)(zuo)。開(kai)(kai)啟主(zhu)機(ji)(ji)時(shi)，通(tong)過(guo)人工或(huo)遙控操作(zuo)(zuo)閉合了(le)與PS－ON相關(guan)的(de)(de)(de)(de)(de)開(kai)(kai)關(guan)，PS－ON呈低(di)(di)(di)(di)(di)(di)(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)R37使339的(de)(de)(de)(de)(de)反相端{6}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)為(wei)低(di)(di)(di)(di)(di)(di)(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)較(jiao)(jiao)器(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)高(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反偏截(jie)止，A比(bi)較(jiao)(jiao)器(qi)的(de)(de)(de)(de)(de)輸(shu)(shu)(shu)(shu)(shu)(shu)出(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(ze)由{5}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)與{4}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)的(de)(de)(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。正常工作(zuo)(zuo)時(shi)，{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)(di)(di)(di)(di)(di)(di)于(yu)(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)低(di)(di)(di)(di)(di)(di)(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)R41送到(dao)(dao)494的(de)(de)(de)(de)(de){4}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)，使{4}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)的(de)(de)(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)低(di)(di)(di)(di)(di)(di)(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(ju)齒波(bo)振(zhen)蕩(dang)信(xin)(xin)(xin)(xin)(xin)號(hao)(hao)(hao)(hao)(hao)(hao)可以從(cong)死區時(shi)間比(bi)較(jiao)(jiao)器(qi)a輸(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)脈沖(chong)(chong)信(xin)(xin)(xin)(xin)(xin)號(hao)(hao)(hao)(hao)(hao)(hao)，另(ling)一(yi)方(fang)面，振(zhen)蕩(dang)信(xin)(xin)(xin)(xin)(xin)號(hao)(hao)(hao)(hao)(hao)(hao)送到(dao)(dao)了(le)PWM比(bi)較(jiao)(jiao)器(qi)b的(de)(de)(de)(de)(de)同相輸(shu)(shu)(shu)(shu)(shu)(shu)入端，PWM比(bi)較(jiao)(jiao)器(qi)輸(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)的(de)(de)(de)(de)(de)脈沖(chong)(chong)信(xin)(xin)(xin)(xin)(xin)號(hao)(hao)(hao)(hao)(hao)(hao)的(de)(de)(de)(de)(de)寬度(du)，則(ze)是由494的(de)(de)(de)(de)(de){1}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)的(de)(de)(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)就是負載的(de)(de)(de)(de)(de)大小(xiao)）與{16}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)的(de)(de)(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。PWM比(bi)較(jiao)(jiao)器(qi)輸(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)的(de)(de)(de)(de)(de)脈沖(chong)(chong)信(xin)(xin)(xin)(xin)(xin)號(hao)(hao)(hao)(hao)(hao)(hao)，最后經(jing)(jing)緩沖(chong)(chong)放(fang)大器(qi)放(fang)大后，從(cong){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)脈沖(chong)(chong)信(xin)(xin)(xin)(xin)(xin)號(hao)(hao)(hao)(hao)(hao)(hao)，ATX電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)向主(zhu)機(ji)(ji)輸(shu)(shu)(shu)(shu)(shu)(shu)出(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(ci)(ci)過(guo)程因C35的(de)(de)(de)(de)(de)充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)有數百毫(hao)秒的(de)(de)(de)(de)(de)延時(shi)，但對(dui)主(zhu)機(ji)(ji)開(kai)(kai)機(ji)(ji)并無影響。494的(de)(de)(de)(de)(de){1}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)從(cong)＋5V、＋12V經(jing)(jing)取樣電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)R15、R16得到(dao)(dao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)，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)略高(gao)(gao)(gao)(gao)于(yu)(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)高(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)R48使339的(de)(de)(de)(de)(de){9}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)得到(dao)(dao)高(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)于(yu)(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)高(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(ci)(ci)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)R50與基準＋5V電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)經(jing)(jing)R64共(gong)同對(dui)C39充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)，經(jing)(jing)數百毫(hao)秒后，{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(sheng)到(dao)(dao)高(gao)(gao)(gao)(gao)于(yu)(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(shi)，D比(bi)較(jiao)(jiao)器(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)高(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(ci)(ci)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)R49反饋至{11}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)，維持{11}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)處于(yu)(yu)高(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{13}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)輸(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)穩定的(de)(de)(de)(de)(de)高(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)(xin)號(hao)(hao)(hao)(hao)(hao)(hao)，主(zhu)機(ji)(ji)檢(jian)測到(dao)(dao)此(ci)(ci)信(xin)(xin)(xin)(xin)(xin)號(hao)(hao)(hao)(hao)(hao)(hao)后即(ji)開(kai)(kai)始(shi)正常工作(zuo)(zuo)。

關機時，主機內開關(guan)使(shi)PS－ON呈(cheng)高電(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)，此(ci)時(shi)339的(de)(de){6}腳(jiao)電(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)高于(yu){7}腳(jiao)，{1}腳(jiao)輸(shu)(shu)出(chu)低(di)(di)電(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)，因(yin)二極管D34的(de)(de)鉗位(wei)作用(yong)，{14}腳(jiao)呈(cheng)低(di)(di)電(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)，C39對C比較(jiao)器及B比較(jiao)器放(fang)電(dian)(dian)(dian)(dian)(dian)(dian)，很(hen)快{11}腳(jiao)呈(cheng)低(di)(di)電(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)，{13}腳(jiao)輸(shu)(shu)出(chu)低(di)(di)電(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)，即PW－OK信(xin)號呈(cheng)低(di)(di)電(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)。在339的(de)(de){1}腳(jiao)為(wei)(wei)低(di)(di)電(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)時(shi)，經D36使(shi){4}臆腳(jiao)為(wei)(wei)低(di)(di)電(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)，{2}腳(jiao)輸(shu)(shu)出(chu)高電(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)，經R41傳送到494的(de)(de){4}腳(jiao)，但因(yin)C35電(dian)(dian)(dian)(dian)(dian)(dian)位(wei)不(bu)(bu)能(neng)突變，經數百毫秒的(de)(de)放(fang)電(dian)(dian)(dian)(dian)(dian)(dian)后方使(shi)494的(de)(de){4}腳(jiao)轉為(wei)(wei)高電(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)，從而封(feng)鎖正負脈沖的(de)(de)輸(shu)(shu)出(chu) ，主機進(jin)入待機狀(zhuang)態。上述的(de)(de)過程(cheng)中，關(guan)機時(shi)C39和C35都(dou)要放(fang)電(dian)(dian)(dian)(dian)(dian)(dian)，但因(yin)放(fang)電(dian)(dian)(dian)(dian)(dian)(dian)時(shi)間常數不(bu)(bu)同，C39放(fang)電(dian)(dian)(dian)(dian)(dian)(dian)較(jiao)快，故PW－OK信(xin)號先于(yu)各(ge)電(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)變成低(di)(di)電(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)，滿足了主機關(guan)機的(de)(de)需要。此(ci)外，關(guan)機時(shi)因(yin)各(ge)路輸(shu)(shu)出(chu)電(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)解(jie)電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)放(fang)電(dian)(dian)(dian)(dian)(dian)(dian)需要時(shi)間，也使(shi)PW－OK信(xin)號先于(yu)各(ge)電(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)回(hui)到低(di)(di)電(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)。

二、 穩壓

494的(de)(de){2}腳(jiao)經R47與(yu)基準電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)＋5V相連，維持較(jiao)好(hao)的(de)(de)穩(wen)定電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)，而{1}腳(jiao)則(ze)(ze)與(yu)取樣電(dian)(dian)(dian)(dian)阻(zu)R15、R16與(yu)＋5V、＋12V相連接，正(zheng)常(chang)的(de)(de)情況(kuang)下，{1}腳(jiao)電(dian)(dian)(dian)(dian)平(ping)與(yu){2}腳(jiao)電(dian)(dian)(dian)(dian)平(ping)相等或(huo)略高(gao)。當輸(shu)出(chu)(chu)(chu)電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)升高(gao)時（無(wu)論＋5V或(huo)＋12V），{1}腳(jiao)電(dian)(dian)(dian)(dian)平(ping)高(gao)于{2}腳(jiao)電(dian)(dian)(dian)(dian)平(ping)，c比較(jiao)器(qi)(qi)輸(shu)出(chu)(chu)(chu)誤差電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)與(yu)鋸齒波振蕩脈沖在PWM比較(jiao)器(qi)(qi)b進行比較(jiao)使(shi)輸(shu)出(chu)(chu)(chu)脈沖寬(kuan)度變窄(zhai)，輸(shu)出(chu)(chu)(chu)電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)回落到標(biao)準值，反(fan)之則(ze)(ze)促使(shi)振蕩脈沖寬(kuan)度增加，輸(shu)出(chu)(chu)(chu)電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)回升。由于494內的(de)(de)放大(da)(da)器(qi)(qi)增益(yi)很高(gao)，故穩(wen)壓(ya)(ya)(ya)精(jing)度很好(hao)。從(cong)穩(wen)壓(ya)(ya)(ya)的(de)(de)原理，我(wo)們可(ke)以(yi)得到ATX電(dian)(dian)(dian)(dian)源輸(shu)出(chu)(chu)(chu)電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)偏(pian)(pian)高(gao)或(huo)偏(pian)(pian)低的(de)(de)維修方法(fa)。如果輸(shu)出(chu)(chu)(chu)電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)偏(pian)(pian)低，可(ke)在494的(de)(de){1}腳(jiao)對地(di)并(bing)聯電(dian)(dian)(dian)(dian)阻(zu)，或(huo)是把R47的(de)(de)電(dian)(dian)(dian)(dian)阻(zu)增大(da)(da)。要是電(dian)(dian)(dian)(dian)源的(de)(de)輸(shu)出(chu)(chu)(chu)偏(pian)(pian)高(gao)，則(ze)(ze)可(ke)在{2}腳(jiao)對地(di)并(bing)聯電(dian)(dian)(dian)(dian)阻(zu)，也可(ke)以(yi)用增大(da)(da)R33或(huo)取下R69、R35來降(jiang)低輸(shu)出(chu)(chu)(chu)電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)。

三、 過流保護

過(guo)流(liu)(liu)(liu)保(bao)護的(de)(de)(de)(de)(de)(de)原理是(shi)基于負(fu)載(zai)愈大(da)，Q3、Q4集電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)極的(de)(de)(de)(de)(de)(de)脈(mo)(mo)(mo)沖(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)也愈高，也即是(shi)R13（1．5kΩ）上的(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)也愈高，從這里(li)采(cai)樣經(jing)D14整流(liu)(liu)(liu)和C36濾(lv)波，再經(jing)R54、R55并聯(lian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻與(yu)R51、R56、R58等(deng)組成的(de)(de)(de)(de)(de)(de)分壓(ya)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路送(song)(song)到494的(de)(de)(de)(de)(de)(de){16}腳(jiao)。隨著負(fu)載(zai)的(de)(de)(de)(de)(de)(de)加(jia)重，{16}腳(jiao)的(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)也隨之上升，當(dang)超過(guo){15}腳(jiao)的(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)時，誤差(cha)放大(da)器輸(shu)(shu)出(chu)(chu)(chu)的(de)(de)(de)(de)(de)(de)誤差(cha)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)促(cu)使調制脈(mo)(mo)(mo)沖(chong)的(de)(de)(de)(de)(de)(de)寬(kuan)(kuan)度變(bian)窄從而使負(fu)載(zai)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)減小。另外，從R56、R58并聯(lian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻獲得的(de)(de)(de)(de)(de)(de)分壓(ya)再經(jing)R52送(song)(song)到339的(de)(de)(de)(de)(de)(de){5}腳(jiao)，當(dang){5}腳(jiao)的(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)超過(guo){4}腳(jiao)時，{2}腳(jiao)即輸(shu)(shu)出(chu)(chu)(chu)高電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)送(song)(song)到494的(de)(de)(de)(de)(de)(de){4}腳(jiao)，494停止(zhi)輸(shu)(shu)出(chu)(chu)(chu)脈(mo)(mo)(mo)沖(chong)信號，終止(zhi)±5V、±12V、＋3．3V電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源的(de)(de)(de)(de)(de)(de)輸(shu)(shu)出(chu)(chu)(chu)，達到過(guo)流(liu)(liu)(liu)及短路保(bao)護的(de)(de)(de)(de)(de)(de)目(mu)的(de)(de)(de)(de)(de)(de)。需要說明的(de)(de)(de)(de)(de)(de)是(shi)：494的(de)(de)(de)(de)(de)(de){16}腳(jiao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)的(de)(de)(de)(de)(de)(de)高低只(zhi)能改變(bian)輸(shu)(shu)出(chu)(chu)(chu)脈(mo)(mo)(mo)沖(chong)的(de)(de)(de)(de)(de)(de)寬(kuan)(kuan)度，但不(bu)影響494的(de)(de)(de)(de)(de)(de){4}腳(jiao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)狀(zhuang)態，而339的(de)(de)(de)(de)(de)(de){5}腳(jiao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)一旦超過(guo){4}腳(jiao)的(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)，339的(de)(de)(de)(de)(de)(de){2}腳(jiao)就(jiu)送(song)(song)出(chu)(chu)(chu)高電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)去封鎖449的(de)(de)(de)(de)(de)(de)脈(mo)(mo)(mo)沖(chong)輸(shu)(shu)出(chu)(chu)(chu)，終止(zhi)±5V、±12V、＋3．3V電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源的(de)(de)(de)(de)(de)(de)輸(shu)(shu)出(chu)(chu)(chu)，同時{2}腳(jiao)的(de)(de)(de)(de)(de)(de)高電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)經(jing)R59和二(er)極管D39反饋到{5}腳(jiao)，維持{5}腳(jiao)處于高電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)狀(zhuang)態，此時若過(guo)載(zai)或短路狀(zhuang)態消失，494的(de)(de)(de)(de)(de)(de){4}腳(jiao)仍維持高電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)，±5V與(yu)±12V、＋3．3V電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源仍不(bu)能輸(shu)(shu)出(chu)(chu)(chu)，只(zhi)有切(qie)斷交(jiao)流(liu)(liu)(liu)市電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)的(de)(de)(de)(de)(de)(de)輸(shu)(shu)入，再重新(xin)接通(tong)交(jiao)流(liu)(liu)(liu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)，方可(ke)再次開機。

四、過壓保護

過電(dian)(dian)(dian)(dian)壓(ya)保護由(you)R17和穩壓(ya)管Z02并聯電(dian)(dian)(dian)(dian)路從＋5V采樣，經D37送到(dao)(dao)339的(de)(de)(de){5}腳(jiao)(jiao)。若＋5V電(dian)(dian)(dian)(dian)源(yuan)(yuan)由(you)于(yu)某種(zhong)原因升(sheng)高(gao)，339的(de)(de)(de){5}腳(jiao)(jiao)電(dian)(dian)(dian)(dian)平也會隨之升(sheng)高(gao)，當超過{4}腳(jiao)(jiao)電(dian)(dian)(dian)(dian)平時，{2}腳(jiao)(jiao)即送出高(gao)電(dian)(dian)(dian)(dian)平去(qu)494的(de)(de)(de){4}腳(jiao)(jiao)，封(feng)鎖±5V、±12V、＋3．3V電(dian)(dian)(dian)(dian)源(yuan)(yuan)的(de)(de)(de)輸出，達(da)到(dao)(dao)過電(dian)(dian)(dian)(dian)壓(ya)保護的(de)(de)(de)目的(de)(de)(de)。正常工(gong)作時，R17上的(de)(de)(de)壓(ya)降(jiang)不大，Z02截止送到(dao)(dao){5}腳(jiao)(jiao)的(de)(de)(de)電(dian)(dian)(dian)(dian)壓(ya)較低，若＋5V電(dian)(dian)(dian)(dian)源(yuan)(yuan)的(de)(de)(de)電(dian)(dian)(dian)(dian)壓(ya)上升(sheng)，使R17上的(de)(de)(de)壓(ya)降(jiang)超過Z02的(de)(de)(de)穩壓(ya)值，Z02導通，＋5V電(dian)(dian)(dian)(dian)源(yuan)(yuan)上升(sheng)后的(de)(de)(de)電(dian)(dian)(dian)(dian)壓(ya)值全(quan)部加到(dao)(dao)339的(de)(de)(de){5}腳(jiao)(jiao)上，促使其快速封(feng)鎖494脈沖的(de)(de)(de)輸出，以(yi)保護電(dian)(dian)(dian)(dian)源(yuan)(yuan)。

五、欠壓保護

欠(qian)壓(ya)保(bao)護從(cong)－5V的D32及－12V處的R14取樣，經R34和D37送(song)到(dao)(dao)339的{5}腳(jiao)。若因某(mou)種原因使輸出電壓(ya)過(guo)低(di)時，－12V及 －5V電壓(ya)的負值也(ye)(ye)會隨之(zhi)減(jian)小，也(ye)(ye)就是(shi)電壓(ya)值上(shang)升，經R34及D37送(song)往339的{5}腳(jiao)使電平上(shang)升，339的{2}腳(jiao)送(song)出高電平到(dao)(dao)494的{4}腳(jiao)，從(cong)而(er)封鎖 449脈沖的輸出，實現欠(qian)壓(ya)保(bao)護。二極管(guan)D32在導(dao)通時，其電壓(ya)降與(yu)通過(guo)的電流基本無關，保(bao)持在0．6V～0．7V，于是(shi)－5V電壓(ya)的減(jian)少量會全部傳送(song)到(dao)(dao)D32的負端(duan)，提高了欠(qian)壓(ya)保(bao)護的靈敏度。