臺式機電源(yuan)電路圖原(yuan)理分(fen)析 臺式機電源(yuan)是(shi)如何實現(xian)多種(zhong)保護(hu)功能的

ATX電(dian)源(yuan)的(de)(de)控(kong)制(zhi)(zhi)電(dian)路(lu)(lu)如上圖。控(kong)制(zhi)(zhi)電(dian)路(lu)(lu)采用TL494及LM339集成(cheng)(cheng)電(dian)路(lu)(lu)（以下簡稱494和339）。494是(shi)雙排16腳(jiao)(jiao)(jiao)(jiao)(jiao)集成(cheng)(cheng)電(dian)路(lu)(lu)，工(gong)(gong)作(zuo)(zuo)電(dian)壓7～40V。它含有由(you){14}腳(jiao)(jiao)(jiao)(jiao)(jiao)輸出的(de)(de)＋5V基準(zhun)電(dian)源(yuan)，輸出電(dian)壓為(wei)＋5V（±0．05V），最大(da)輸出電(dian)流250mA；一個頻率可(ke)調的(de)(de)鋸齒波產(chan)生電(dian)路(lu)(lu)，振蕩頻率由(you){5}腳(jiao)(jiao)(jiao)(jiao)(jiao)外(wai)接電(dian)容及{6}腳(jiao)(jiao)(jiao)(jiao)(jiao)外(wai)接電(dian)阻來決定。{13}腳(jiao)(jiao)(jiao)(jiao)(jiao)為(wei)高電(dian)平時，由(you){8}腳(jiao)(jiao)(jiao)(jiao)(jiao)及{11}腳(jiao)(jiao)(jiao)(jiao)(jiao)輸出雙路(lu)(lu)反(fan)相（即推挽工(gong)(gong)作(zuo)(zuo)方(fang)式）的(de)(de)脈寬(kuan)調制(zhi)(zhi)信號(hao)。

比較器是一種運算(suan)放大(da)器，符號用三角形(xing)表示，它有一個同相輸(shu)入端(duan)“＋”；一個反相輸(shu)入端(duan)“－”和(he)一個輸(shu)出端(duan)。

比(bi)較(jiao)器(qi)(qi)(qi)同相(xiang)(xiang)(xiang)(xiang)端(duan)(duan)電(dian)(dian)(dian)平(ping)(ping)(ping)(ping)若(ruo)高(gao)于(yu)反(fan)(fan)相(xiang)(xiang)(xiang)(xiang)端(duan)(duan)電(dian)(dian)(dian)平(ping)(ping)(ping)(ping)，則(ze)輸(shu)出(chu)端(duan)(duan)輸(shu)出(chu)高(gao)電(dian)(dian)(dian)平(ping)(ping)(ping)(ping)；反(fan)(fan)之(zhi)輸(shu)出(chu)低(di)電(dian)(dian)(dian)平(ping)(ping)(ping)(ping)。494內(nei)的(de)(de)(de)(de)(de)(de)(de)比(bi)較(jiao)放(fang)大器(qi)(qi)(qi)有(you)(you)(you)四個，為(wei)(wei)(wei)(wei)(wei)敘述方(fang)便(bian)，在(zai)上圖中用(yong)(yong)小(xiao)寫字母a、b、c、d來(lai)表示。其(qi)中a是死(si)區(qu)時(shi)(shi)(shi)間(jian)(jian)比(bi)較(jiao)器(qi)(qi)(qi)。因兩(liang)個作(zuo)(zuo)逆(ni)變(bian)工作(zuo)(zuo)的(de)(de)(de)(de)(de)(de)(de)三(san)(san)極(ji)(ji)(ji)管(guan)串聯(lian)后(hou)(hou)接(jie)到＋310V的(de)(de)(de)(de)(de)(de)(de)直流(liu)電(dian)(dian)(dian)源上，若(ruo)兩(liang)個三(san)(san)極(ji)(ji)(ji)管(guan)同時(shi)(shi)(shi)導(dao)通(tong)，就會形(xing)成對直流(liu)電(dian)(dian)(dian)源的(de)(de)(de)(de)(de)(de)(de)短(duan)路。兩(liang)個三(san)(san)極(ji)(ji)(ji)管(guan)同時(shi)(shi)(shi)導(dao)通(tong)可能(neng)發(fa)生(sheng)在(zai)一(yi)個管(guan)子(zi)(zi)從(cong)截(jie)(jie)(jie)止轉(zhuan)為(wei)(wei)(wei)(wei)(wei)導(dao)通(tong)，而(er)另一(yi)個管(guan)子(zi)(zi)由導(dao)通(tong)轉(zhuan)為(wei)(wei)(wei)(wei)(wei)截(jie)(jie)(jie)止的(de)(de)(de)(de)(de)(de)(de)時(shi)(shi)(shi)候(hou)。因為(wei)(wei)(wei)(wei)(wei)管(guan)子(zi)(zi)在(zai)轉(zhuan)換時(shi)(shi)(shi)有(you)(you)(you)時(shi)(shi)(shi)間(jian)(jian)的(de)(de)(de)(de)(de)(de)(de)延(yan)遲，截(jie)(jie)(jie)止的(de)(de)(de)(de)(de)(de)(de)管(guan)子(zi)(zi)已經轉(zhuan)為(wei)(wei)(wei)(wei)(wei)導(dao)通(tong)了(le)(le)，但導(dao)通(tong)的(de)(de)(de)(de)(de)(de)(de)管(guan)子(zi)(zi)尚(shang)未完全轉(zhuan)為(wei)(wei)(wei)(wei)(wei)截(jie)(jie)(jie)止，于(yu)是兩(liang)個管(guan)子(zi)(zi)都(dou)呈導(dao)通(tong)狀態而(er)形(xing)成對直流(liu)電(dian)(dian)(dian)源的(de)(de)(de)(de)(de)(de)(de)短(duan)路。為(wei)(wei)(wei)(wei)(wei)防止這樣(yang)的(de)(de)(de)(de)(de)(de)(de)事情發(fa)生(sheng)，494設置了(le)(le)死(si)區(qu)時(shi)(shi)(shi)間(jian)(jian)比(bi)較(jiao)器(qi)(qi)(qi)a。從(cong)圖中可以看出(chu)，在(zai)比(bi)較(jiao)器(qi)(qi)(qi)a的(de)(de)(de)(de)(de)(de)(de)反(fan)(fan)相(xiang)(xiang)(xiang)(xiang)輸(shu)入(ru)(ru)端(duan)(duan)串聯(lian)了(le)(le)一(yi)個“電(dian)(dian)(dian)源”，正極(ji)(ji)(ji)接(jie)反(fan)(fan)相(xiang)(xiang)(xiang)(xiang)端(duan)(duan)，負極(ji)(ji)(ji)接(jie)494的(de)(de)(de)(de)(de)(de)(de){4}腳(jiao)(jiao)。A比(bi)較(jiao)器(qi)(qi)(qi)同相(xiang)(xiang)(xiang)(xiang)端(duan)(duan)輸(shu)入(ru)(ru)的(de)(de)(de)(de)(de)(de)(de)鋸齒波信(xin)(xin)號，只有(you)(you)(you)大于(yu)“電(dian)(dian)(dian)源”電(dian)(dian)(dian)壓的(de)(de)(de)(de)(de)(de)(de)部分(fen)才有(you)(you)(you)輸(shu)出(chu)，在(zai)三(san)(san)極(ji)(ji)(ji)管(guan)導(dao)通(tong)變(bian)為(wei)(wei)(wei)(wei)(wei)截(jie)(jie)(jie)止與截(jie)(jie)(jie)止轉(zhuan)為(wei)(wei)(wei)(wei)(wei)導(dao)通(tong)期間(jian)(jian)，也就是死(si)區(qu)時(shi)(shi)(shi)間(jian)(jian)，494沒有(you)(you)(you)脈(mo)沖(chong)(chong)輸(shu)出(chu)，避免了(le)(le)對直流(liu)電(dian)(dian)(dian)源的(de)(de)(de)(de)(de)(de)(de)短(duan)路。死(si)區(qu)時(shi)(shi)(shi)間(jian)(jian)還可由{4}腳(jiao)(jiao)外(wai)接(jie)的(de)(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)平(ping)(ping)(ping)(ping)來(lai)控制，{4}腳(jiao)(jiao)的(de)(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)平(ping)(ping)(ping)(ping)上升(sheng)，死(si)區(qu)時(shi)(shi)(shi)間(jian)(jian)變(bian)寬，494輸(shu)出(chu)的(de)(de)(de)(de)(de)(de)(de)脈(mo)沖(chong)(chong)就變(bian)窄了(le)(le)，若(ruo){4}腳(jiao)(jiao)的(de)(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)平(ping)(ping)(ping)(ping)超過了(le)(le)鋸齒波的(de)(de)(de)(de)(de)(de)(de)峰(feng)值電(dian)(dian)(dian)壓，494就進入(ru)(ru)了(le)(le)保(bao)護狀態，{8}腳(jiao)(jiao)和{11}腳(jiao)(jiao)就不輸(shu)出(chu)脈(mo)沖(chong)(chong)了(le)(le)。494內(nei)部還有(you)(you)(you)3個二輸(shu)入(ru)(ru)端(duan)(duan)與門(men)（用(yong)(yong)1、2、3表示）、兩(liang)個二輸(shu)入(ru)(ru)端(duan)(duan)與非(fei)門(men)、反(fan)(fan)相(xiang)(xiang)(xiang)(xiang)器(qi)(qi)(qi)、T觸(chu)發(fa)器(qi)(qi)(qi)等電(dian)(dian)(dian)路。與門(men)是這樣(yang)一(yi)種電(dian)(dian)(dian)路，只有(you)(you)(you)所有(you)(you)(you)的(de)(de)(de)(de)(de)(de)(de)輸(shu)入(ru)(ru)端(duan)(duan)都(dou)是高(gao)電(dian)(dian)(dian)平(ping)(ping)(ping)(ping)，輸(shu)出(chu)端(duan)(duan)才能(neng)輸(shu)出(chu)高(gao)電(dian)(dian)(dian)平(ping)(ping)(ping)(ping)；若(ruo)有(you)(you)(you)一(yi)個輸(shu)入(ru)(ru)端(duan)(duan)為(wei)(wei)(wei)(wei)(wei)低(di)電(dian)(dian)(dian)平(ping)(ping)(ping)(ping)，則(ze)輸(shu)出(chu)端(duan)(duan)輸(shu)出(chu)低(di)電(dian)(dian)(dian)平(ping)(ping)(ping)(ping)。反(fan)(fan)相(xiang)(xiang)(xiang)(xiang)器(qi)(qi)(qi)的(de)(de)(de)(de)(de)(de)(de)作(zuo)(zuo)用(yong)(yong)是把輸(shu)入(ru)(ru)信(xin)(xin)號隔(ge)離放(fang)大后(hou)(hou)反(fan)(fan)相(xiang)(xiang)(xiang)(xiang)輸(shu)出(chu)。與非(fei)門(men)則(ze)相(xiang)(xiang)(xiang)(xiang)當于(yu)一(yi)個與門(men)和一(yi)個反(fan)(fan)相(xiang)(xiang)(xiang)(xiang)器(qi)(qi)(qi)的(de)(de)(de)(de)(de)(de)(de)組(zu)合(he)。T觸(chu)發(fa)器(qi)(qi)(qi)的(de)(de)(de)(de)(de)(de)(de)作(zuo)(zuo)用(yong)(yong)是：每輸(shu)入(ru)(ru)一(yi)個脈(mo)沖(chong)(chong)，輸(shu)出(chu)端(duan)(duan)的(de)(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)平(ping)(ping)(ping)(ping)就變(bian)化一(yi)次。如(ru)輸(shu)出(chu)端(duan)(duan)Q為(wei)(wei)(wei)(wei)(wei)低(di)電(dian)(dian)(dian)平(ping)(ping)(ping)(ping)，輸(shu)入(ru)(ru)一(yi)個脈(mo)沖(chong)(chong)后(hou)(hou)，Q變(bian)為(wei)(wei)(wei)(wei)(wei)高(gao)電(dian)(dian)(dian)平(ping)(ping)(ping)(ping)，再輸(shu)入(ru)(ru)一(yi)個脈(mo)沖(chong)(chong)，Q又(you)回到低(di)電(dian)(dian)(dian)平(ping)(ping)(ping)(ping)。

339是四(si)比較(jiao)(jiao)(jiao)器集(ji)成電(dian)(dian)(dian)(dian)路(lu)。 LM339集(ji)成塊(kuai)內部裝有四(si)個獨立的(de)(de)電(dian)(dian)(dian)(dian)壓(ya)比較(jiao)(jiao)(jiao)器，每個比較(jiao)(jiao)(jiao)器有兩(liang)(liang)個輸(shu)(shu)(shu)(shu)(shu)入(ru)(ru)端(duan)(duan)(duan)(duan)和(he)一(yi)(yi)(yi)(yi)個輸(shu)(shu)(shu)(shu)(shu)出端(duan)(duan)(duan)(duan)。兩(liang)(liang)個輸(shu)(shu)(shu)(shu)(shu)入(ru)(ru)端(duan)(duan)(duan)(duan)一(yi)(yi)(yi)(yi)個稱(cheng)為(wei)同相(xiang)輸(shu)(shu)(shu)(shu)(shu)入(ru)(ru)端(duan)(duan)(duan)(duan)，用“+”表示，另(ling)一(yi)(yi)(yi)(yi)個稱(cheng)為(wei)反相(xiang)輸(shu)(shu)(shu)(shu)(shu)入(ru)(ru)端(duan)(duan)(duan)(duan)，用“-”表示。用作比較(jiao)(jiao)(jiao)兩(liang)(liang)個電(dian)(dian)(dian)(dian)壓(ya)時(shi)(shi)，任(ren)意一(yi)(yi)(yi)(yi)個輸(shu)(shu)(shu)(shu)(shu)入(ru)(ru)端(duan)(duan)(duan)(duan)加(jia)一(yi)(yi)(yi)(yi)個固(gu)定(ding)電(dian)(dian)(dian)(dian)壓(ya)做參(can)考(kao)電(dian)(dian)(dian)(dian)壓(ya)（也(ye)稱(cheng)為(wei)門限(xian)電(dian)(dian)(dian)(dian)平，它(ta)可選擇LM339輸(shu)(shu)(shu)(shu)(shu)入(ru)(ru)共(gong)模(mo)范圍的(de)(de)任(ren)何一(yi)(yi)(yi)(yi)點），另(ling)一(yi)(yi)(yi)(yi)端(duan)(duan)(duan)(duan)加(jia)一(yi)(yi)(yi)(yi)個待比較(jiao)(jiao)(jiao)的(de)(de)信(xin)號電(dian)(dian)(dian)(dian)壓(ya)。當(dang)“+”端(duan)(duan)(duan)(duan)電(dian)(dian)(dian)(dian)壓(ya)高于(yu)“-”端(duan)(duan)(duan)(duan)時(shi)(shi)，輸(shu)(shu)(shu)(shu)(shu)出管截(jie)止(zhi)，相(xiang)當(dang)于(yu)輸(shu)(shu)(shu)(shu)(shu)出端(duan)(duan)(duan)(duan)開路(lu)。當(dang)“-”端(duan)(duan)(duan)(duan)電(dian)(dian)(dian)(dian)壓(ya)高于(yu)“+”端(duan)(duan)(duan)(duan)時(shi)(shi)，輸(shu)(shu)(shu)(shu)(shu)出管飽和(he)，相(xiang)當(dang)于(yu)輸(shu)(shu)(shu)(shu)(shu)出端(duan)(duan)(duan)(duan)接低電(dian)(dian)(dian)(dian)位。兩(liang)(liang)個輸(shu)(shu)(shu)(shu)(shu)入(ru)(ru)端(duan)(duan)(duan)(duan)電(dian)(dian)(dian)(dian)壓(ya)差(cha)別大于(yu)10mV就能(neng)(neng)確保(bao)輸(shu)(shu)(shu)(shu)(shu)出能(neng)(neng)從一(yi)(yi)(yi)(yi)種狀態可靠(kao)地(di)轉換到(dao)另(ling)一(yi)(yi)(yi)(yi)種狀態， LM339的(de)(de)輸(shu)(shu)(shu)(shu)(shu)出端(duan)(duan)(duan)(duan)相(xiang)當(dang)于(yu)一(yi)(yi)(yi)(yi)只(zhi)不(bu)(bu)接集(ji)電(dian)(dian)(dian)(dian)極電(dian)(dian)(dian)(dian)阻(zu)的(de)(de)晶體三(san)極管，在使用時(shi)(shi)輸(shu)(shu)(shu)(shu)(shu)出端(duan)(duan)(duan)(duan)到(dao)正電(dian)(dian)(dian)(dian)源一(yi)(yi)(yi)(yi)般須接一(yi)(yi)(yi)(yi)只(zhi)電(dian)(dian)(dian)(dian)阻(zu)（稱(cheng)為(wei)上(shang)拉(la)電(dian)(dian)(dian)(dian)阻(zu)，選3-15K）。選不(bu)(bu)同阻(zu)值(zhi)(zhi)的(de)(de)上(shang)拉(la)電(dian)(dian)(dian)(dian)阻(zu)會影響輸(shu)(shu)(shu)(shu)(shu)出端(duan)(duan)(duan)(duan)高電(dian)(dian)(dian)(dian)位的(de)(de)值(zhi)(zhi)。因為(wei)當(dang)輸(shu)(shu)(shu)(shu)(shu)出晶體三(san)極管截(jie)止(zhi)時(shi)(shi)，它(ta)的(de)(de)集(ji)電(dian)(dian)(dian)(dian)極電(dian)(dian)(dian)(dian)壓(ya)基本上(shang)取決于(yu)上(shang)拉(la)電(dian)(dian)(dian)(dian)阻(zu)與(yu)負載(zai)的(de)(de)值(zhi)(zhi)。

按管腳的順序把(ba)內部四個比較(jiao)器(qi)設為A、B 、C 、D 比較(jiao)器(qi)。494和339再配合其他電(dian)路，共同完成ATX電(dian)源的穩壓(ya)，產生PW－OK信(xin)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)源(yuan)接通(tong)市電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)后(hou)，輔助(zhu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)立即(ji)工作(zuo)(zuo)。一方面輸(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu) ＋5VSB電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)，同時向(xiang)494的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de){12}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)提供十幾伏到(dao)(dao)二十多伏的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)直流(liu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)。494從(cong)(cong){14}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)輸(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)＋5V基準電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)，鋸(ju)齒波(bo)振(zhen)(zhen)蕩(dang)器(qi)(qi)(qi)(qi)也(ye)(ye)開(kai)始(shi)起振(zhen)(zhen)工作(zuo)(zuo)。若主(zhu)(zhu)機(ji)(ji)未(wei)開(kai)機(ji)(ji)，PS－ON信(xin)(xin)號(hao)(hao)(hao)為(wei)(wei)(wei)高(gao)(gao)(gao)(gao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)，經(jing)(jing)(jing)(jing)(jing)R37使(shi)(shi)339的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)B比(bi)(bi)(bi)較(jiao)(jiao)(jiao)(jiao)(jiao)器(qi)(qi)(qi)(qi){6}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)亦為(wei)(wei)(wei)高(gao)(gao)(gao)(gao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)，因電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻R37小(xiao)于(yu)(yu)(yu)(yu)R44，{6}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)高(gao)(gao)(gao)(gao)于(yu)(yu)(yu)(yu){7}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)，B比(bi)(bi)(bi)較(jiao)(jiao)(jiao)(jiao)(jiao)器(qi)(qi)(qi)(qi)輸(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)端(duan)(duan){1}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)輸(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)低(di)(di)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)，經(jing)(jing)(jing)(jing)(jing)D36的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)鉗(qian)位作(zuo)(zuo)用(yong)，A比(bi)(bi)(bi)較(jiao)(jiao)(jiao)(jiao)(jiao)器(qi)(qi)(qi)(qi)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)反(fan)相端(duan)(duan){4}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)亦為(wei)(wei)(wei)低(di)(di)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)，其(qi)(qi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)低(di)(di)于(yu)(yu)(yu)(yu)同相端(duan)(duan){5}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)，輸(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)端(duan)(duan){2}腳(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)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)，經(jing)(jing)(jing)(jing)(jing)R41使(shi)(shi)494的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de){4}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)為(wei)(wei)(wei)高(gao)(gao)(gao)(gao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)，故(gu)(gu)494內部的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)死(si)區時間(jian)比(bi)(bi)(bi)較(jiao)(jiao)(jiao)(jiao)(jiao)器(qi)(qi)(qi)(qi)a輸(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)低(di)(di)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)，與(yu)門1也(ye)(ye)因此(ci)輸(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)低(di)(di)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)并(bing)進而使(shi)(shi)與(yu)門2和(he)與(yu)門3輸(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)低(di)(di)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)，封鎖了(le)振(zhen)(zhen)蕩(dang)器(qi)(qi)(qi)(qi)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)輸(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)，{8}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)、{11}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)無脈(mo)沖(chong)(chong)輸(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)，ATX電(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)源(yuan)輸(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)，主(zhu)(zhu)機(ji)(ji)處于(yu)(yu)(yu)(yu)待(dai)機(ji)(ji)狀態。因＋5V、＋12V電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)輸(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)為(wei)(wei)(wei)零(ling)(ling)，經(jing)(jing)(jing)(jing)(jing)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻R15、R16使(shi)(shi)494的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de){1}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)亦為(wei)(wei)(wei)零(ling)(ling)，494的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)c比(bi)(bi)(bi)較(jiao)(jiao)(jiao)(jiao)(jiao)器(qi)(qi)(qi)(qi)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)輸(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)端(duan)(duan){3}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)輸(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)亦為(wei)(wei)(wei)零(ling)(ling)，經(jing)(jing)(jing)(jing)(jing)R48使(shi)(shi)339的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de){9}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)亦為(wei)(wei)(wei)零(ling)(ling)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)，故(gu)(gu)339的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)C比(bi)(bi)(bi)較(jiao)(jiao)(jiao)(jiao)(jiao)器(qi)(qi)(qi)(qi)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)輸(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)端(duan)(duan){14}腳(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)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)。另外，339的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de){1}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)低(di)(di)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)信(xin)(xin)號(hao)(hao)(hao)因D34的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)鉗(qian)位作(zuo)(zuo)用(yong)，也(ye)(ye)使(shi)(shi){14}腳(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)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)，經(jing)(jing)(jing)(jing)(jing)R50和(he)R63使(shi)(shi){11}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)亦為(wei)(wei)(wei)低(di)(di)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)。因此(ci)D比(bi)(bi)(bi)較(jiao)(jiao)(jiao)(jiao)(jiao)器(qi)(qi)(qi)(qi)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)輸(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)端(duan)(duan){13}腳(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)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)，也(ye)(ye)就(jiu)(jiu)是PW－OK信(xin)(xin)號(hao)(hao)(hao)為(wei)(wei)(wei)低(di)(di)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)，主(zhu)(zhu)機(ji)(ji)不會工作(zuo)(zuo)。開(kai)啟主(zhu)(zhu)機(ji)(ji)時，通(tong)過(guo)人工或遙(yao)控操作(zuo)(zuo)閉(bi)合了(le)與(yu)PS－ON相關(guan)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)開(kai)關(guan)，PS－ON呈低(di)(di)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)，經(jing)(jing)(jing)(jing)(jing)R37使(shi)(shi)339的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)反(fan)相端(duan)(duan){6}腳(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)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)，B比(bi)(bi)(bi)較(jiao)(jiao)(jiao)(jiao)(jiao)器(qi)(qi)(qi)(qi){1}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)輸(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)高(gao)(gao)(gao)(gao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)，D35、D36反(fan)偏截止，A比(bi)(bi)(bi)較(jiao)(jiao)(jiao)(jiao)(jiao)器(qi)(qi)(qi)(qi)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)輸(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)則(ze)由{5}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)與(yu){4}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)決定。正常(chang)工作(zuo)(zuo)時，{5}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)低(di)(di)于(yu)(yu)(yu)(yu){4}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)，{2}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)輸(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)低(di)(di)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)，經(jing)(jing)(jing)(jing)(jing)R41送(song)到(dao)(dao)494的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de){4}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)，使(shi)(shi){4}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(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)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)，鋸(ju)齒波(bo)振(zhen)(zhen)蕩(dang)信(xin)(xin)號(hao)(hao)(hao)可以從(cong)(cong)死(si)區時間(jian)比(bi)(bi)(bi)較(jiao)(jiao)(jiao)(jiao)(jiao)器(qi)(qi)(qi)(qi)a輸(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)脈(mo)沖(chong)(chong)信(xin)(xin)號(hao)(hao)(hao)，另一方面，振(zhen)(zhen)蕩(dang)信(xin)(xin)號(hao)(hao)(hao)送(song)到(dao)(dao)了(le)PWM比(bi)(bi)(bi)較(jiao)(jiao)(jiao)(jiao)(jiao)器(qi)(qi)(qi)(qi)b的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)同相輸(shu)(shu)(shu)(shu)(shu)入端(duan)(duan)，PWM比(bi)(bi)(bi)較(jiao)(jiao)(jiao)(jiao)(jiao)器(qi)(qi)(qi)(qi)輸(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)脈(mo)沖(chong)(chong)信(xin)(xin)號(hao)(hao)(hao)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)寬(kuan)度(du)，則(ze)是由494的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de){1}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)（也(ye)(ye)就(jiu)(jiu)是負載的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)大(da)小(xiao)）與(yu){16}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)來決定。PWM比(bi)(bi)(bi)較(jiao)(jiao)(jiao)(jiao)(jiao)器(qi)(qi)(qi)(qi)輸(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)脈(mo)沖(chong)(chong)信(xin)(xin)號(hao)(hao)(hao)，最后(hou)經(jing)(jing)(jing)(jing)(jing)緩沖(chong)(chong)放大(da)器(qi)(qi)(qi)(qi)放大(da)后(hou)，從(cong)(cong){8}、{11}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)輸(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)脈(mo)沖(chong)(chong)信(xin)(xin)號(hao)(hao)(hao)，ATX電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)向(xiang)主(zhu)(zhu)機(ji)(ji)輸(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)±5V、±12V、＋3.3V電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)。此(ci)過(guo)程因C35的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)充(chong)電(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)(de)(de)(de)(de)(de)(de)(de)(de)延時，但對主(zhu)(zhu)機(ji)(ji)開(kai)機(ji)(ji)并(bing)無影響。494的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de){1}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)從(cong)(cong)＋5V、＋12V經(jing)(jing)(jing)(jing)(jing)取樣電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻R15、R16得(de)到(dao)(dao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓，其(qi)(qi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)略(lve)高(gao)(gao)(gao)(gao)于(yu)(yu)(yu)(yu){2}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)，{3}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)輸(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)高(gao)(gao)(gao)(gao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)，經(jing)(jing)(jing)(jing)(jing)R48使(shi)(shi)339的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de){9}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)得(de)到(dao)(dao)高(gao)(gao)(gao)(gao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)，其(qi)(qi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)高(gao)(gao)(gao)(gao)于(yu)(yu)(yu)(yu){8}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)，因而{14}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)輸(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)高(gao)(gao)(gao)(gao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(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)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)經(jing)(jing)(jing)(jing)(jing)R50與(yu)基準＋5V電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)經(jing)(jing)(jing)(jing)(jing)R64共同對C39充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)，經(jing)(jing)(jing)(jing)(jing)數(shu)百毫(hao)(hao)秒后(hou)，{11}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)升到(dao)(dao)高(gao)(gao)(gao)(gao)于(yu)(yu)(yu)(yu){10}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)時，D比(bi)(bi)(bi)較(jiao)(jiao)(jiao)(jiao)(jiao)器(qi)(qi)(qi)(qi){13}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)輸(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)高(gao)(gao)(gao)(gao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(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)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)經(jing)(jing)(jing)(jing)(jing)R49反(fan)饋(kui)至{11}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)，維持{11}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)處于(yu)(yu)(yu)(yu)高(gao)(gao)(gao)(gao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)狀態，故(gu)(gu){13}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)輸(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)穩定的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)高(gao)(gao)(gao)(gao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping) PW－OK信(xin)(xin)號(hao)(hao)(hao)，主(zhu)(zhu)機(ji)(ji)檢測到(dao)(dao)此(ci)信(xin)(xin)號(hao)(hao)(hao)后(hou)即(ji)開(kai)始(shi)正常(chang)工作(zuo)(zuo)。

關機時，主機內開(kai)關(guan)使PS－ON呈(cheng)(cheng)高電(dian)(dian)(dian)(dian)平(ping)(ping)(ping)，此時(shi)339的(de)(de)(de){6}腳電(dian)(dian)(dian)(dian)平(ping)(ping)(ping)高于(yu){7}腳，{1}腳輸(shu)(shu)出(chu)(chu)低(di)(di)(di)(di)電(dian)(dian)(dian)(dian)平(ping)(ping)(ping)，因(yin)二(er)極管D34的(de)(de)(de)鉗(qian)位作用，{14}腳呈(cheng)(cheng)低(di)(di)(di)(di)電(dian)(dian)(dian)(dian)平(ping)(ping)(ping)，C39對C比較器及B比較器放(fang)電(dian)(dian)(dian)(dian)，很快{11}腳呈(cheng)(cheng)低(di)(di)(di)(di)電(dian)(dian)(dian)(dian)平(ping)(ping)(ping)，{13}腳輸(shu)(shu)出(chu)(chu)低(di)(di)(di)(di)電(dian)(dian)(dian)(dian)平(ping)(ping)(ping)，即PW－OK信號(hao)呈(cheng)(cheng)低(di)(di)(di)(di)電(dian)(dian)(dian)(dian)平(ping)(ping)(ping)。在339的(de)(de)(de){1}腳為低(di)(di)(di)(di)電(dian)(dian)(dian)(dian)平(ping)(ping)(ping)時(shi)，經D36使{4}臆腳為低(di)(di)(di)(di)電(dian)(dian)(dian)(dian)平(ping)(ping)(ping)，{2}腳輸(shu)(shu)出(chu)(chu)高電(dian)(dian)(dian)(dian)平(ping)(ping)(ping)，經R41傳送(song)到494的(de)(de)(de){4}腳，但(dan)因(yin)C35電(dian)(dian)(dian)(dian)位不能突變，經數(shu)(shu)百毫秒的(de)(de)(de)放(fang)電(dian)(dian)(dian)(dian)后方使494的(de)(de)(de){4}腳轉為高電(dian)(dian)(dian)(dian)平(ping)(ping)(ping)，從而封(feng)鎖正負脈沖的(de)(de)(de)輸(shu)(shu)出(chu)(chu) ，主機進入待機狀(zhuang)態。上述的(de)(de)(de)過程中，關(guan)機時(shi)C39和C35都要放(fang)電(dian)(dian)(dian)(dian)，但(dan)因(yin)放(fang)電(dian)(dian)(dian)(dian)時(shi)間常(chang)數(shu)(shu)不同(tong)，C39放(fang)電(dian)(dian)(dian)(dian)較快，故PW－OK信號(hao)先于(yu)各電(dian)(dian)(dian)(dian)源變成低(di)(di)(di)(di)電(dian)(dian)(dian)(dian)平(ping)(ping)(ping)，滿足了主機關(guan)機的(de)(de)(de)需要。此外(wai)，關(guan)機時(shi)因(yin)各路輸(shu)(shu)出(chu)(chu)電(dian)(dian)(dian)(dian)源的(de)(de)(de)電(dian)(dian)(dian)(dian)解電(dian)(dian)(dian)(dian)容(rong)放(fang)電(dian)(dian)(dian)(dian)需要時(shi)間，也使PW－OK信號(hao)先于(yu)各電(dian)(dian)(dian)(dian)源回到低(di)(di)(di)(di)電(dian)(dian)(dian)(dian)平(ping)(ping)(ping)。

二、 穩壓

494的(de)(de){2}腳(jiao)(jiao)(jiao)(jiao)經R47與基準(zhun)電(dian)(dian)(dian)壓(ya)＋5V相(xiang)連，維持(chi)較好的(de)(de)穩(wen)定電(dian)(dian)(dian)壓(ya)，而{1}腳(jiao)(jiao)(jiao)(jiao)則與取(qu)樣(yang)電(dian)(dian)(dian)阻(zu)R15、R16與＋5V、＋12V相(xiang)連接，正常的(de)(de)情(qing)況下(xia)，{1}腳(jiao)(jiao)(jiao)(jiao)電(dian)(dian)(dian)平(ping)與{2}腳(jiao)(jiao)(jiao)(jiao)電(dian)(dian)(dian)平(ping)相(xiang)等或(huo)略高(gao)(gao)。當(dang)輸(shu)(shu)(shu)出(chu)(chu)(chu)電(dian)(dian)(dian)壓(ya)升高(gao)(gao)時（無(wu)論(lun)＋5V或(huo)＋12V），{1}腳(jiao)(jiao)(jiao)(jiao)電(dian)(dian)(dian)平(ping)高(gao)(gao)于(yu)(yu){2}腳(jiao)(jiao)(jiao)(jiao)電(dian)(dian)(dian)平(ping)，c比較器輸(shu)(shu)(shu)出(chu)(chu)(chu)誤差電(dian)(dian)(dian)壓(ya)與鋸齒波振(zhen)蕩(dang)脈沖在(zai)PWM比較器b進行(xing)比較使(shi)輸(shu)(shu)(shu)出(chu)(chu)(chu)脈沖寬度變窄，輸(shu)(shu)(shu)出(chu)(chu)(chu)電(dian)(dian)(dian)壓(ya)回落到標準(zhun)值，反之(zhi)則促使(shi)振(zhen)蕩(dang)脈沖寬度增(zeng)加，輸(shu)(shu)(shu)出(chu)(chu)(chu)電(dian)(dian)(dian)壓(ya)回升。由(you)于(yu)(yu)494內的(de)(de)放大器增(zeng)益(yi)很(hen)高(gao)(gao)，故穩(wen)壓(ya)精(jing)度很(hen)好。從(cong)穩(wen)壓(ya)的(de)(de)原理，我們可以得到ATX電(dian)(dian)(dian)源(yuan)輸(shu)(shu)(shu)出(chu)(chu)(chu)電(dian)(dian)(dian)壓(ya)偏(pian)(pian)高(gao)(gao)或(huo)偏(pian)(pian)低的(de)(de)維修方法。如果(guo)輸(shu)(shu)(shu)出(chu)(chu)(chu)電(dian)(dian)(dian)壓(ya)偏(pian)(pian)低，可在(zai)494的(de)(de){1}腳(jiao)(jiao)(jiao)(jiao)對地并(bing)聯電(dian)(dian)(dian)阻(zu)，或(huo)是(shi)把R47的(de)(de)電(dian)(dian)(dian)阻(zu)增(zeng)大。要是(shi)電(dian)(dian)(dian)源(yuan)的(de)(de)輸(shu)(shu)(shu)出(chu)(chu)(chu)偏(pian)(pian)高(gao)(gao)，則可在(zai){2}腳(jiao)(jiao)(jiao)(jiao)對地并(bing)聯電(dian)(dian)(dian)阻(zu)，也可以用增(zeng)大R33或(huo)取(qu)下(xia)R69、R35來降低輸(shu)(shu)(shu)出(chu)(chu)(chu)電(dian)(dian)(dian)壓(ya)。

三、 過流保護

過(guo)流(liu)(liu)保護的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)原(yuan)理是(shi)基于負(fu)載(zai)愈大，Q3、Q4集(ji)電(dian)(dian)極(ji)(ji)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)脈(mo)(mo)沖電(dian)(dian)壓(ya)(ya)(ya)也愈高(gao)(gao)(gao)，也即(ji)是(shi)R13（1．5kΩ）上的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)電(dian)(dian)壓(ya)(ya)(ya)也愈高(gao)(gao)(gao)，從這里采樣經(jing)D14整流(liu)(liu)和C36濾(lv)波，再(zai)(zai)經(jing)R54、R55并聯電(dian)(dian)阻(zu)(zu)與R51、R56、R58等組成(cheng)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)分(fen)壓(ya)(ya)(ya)電(dian)(dian)路送(song)(song)到(dao)(dao)494的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de){16}腳(jiao)。隨著負(fu)載(zai)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)加重，{16}腳(jiao)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)電(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)也隨之上升，當(dang)超過(guo){15}腳(jiao)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)電(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)時(shi)(shi)，誤差(cha)放大器輸(shu)(shu)(shu)出(chu)(chu)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)誤差(cha)電(dian)(dian)壓(ya)(ya)(ya)促使調制脈(mo)(mo)沖的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)寬度(du)(du)變(bian)窄從而使負(fu)載(zai)電(dian)(dian)流(liu)(liu)減小。另外，從R56、R58并聯電(dian)(dian)阻(zu)(zu)獲(huo)得(de)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)分(fen)壓(ya)(ya)(ya)再(zai)(zai)經(jing)R52送(song)(song)到(dao)(dao)339的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de){5}腳(jiao)，當(dang){5}腳(jiao)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)電(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)超過(guo){4}腳(jiao)時(shi)(shi)，{2}腳(jiao)即(ji)輸(shu)(shu)(shu)出(chu)(chu)高(gao)(gao)(gao)電(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)送(song)(song)到(dao)(dao)494的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de){4}腳(jiao)，494停止輸(shu)(shu)(shu)出(chu)(chu)脈(mo)(mo)沖信號，終(zhong)止±5V、±12V、＋3．3V電(dian)(dian)源(yuan)(yuan)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)輸(shu)(shu)(shu)出(chu)(chu)，達到(dao)(dao)過(guo)流(liu)(liu)及(ji)短(duan)(duan)路保護的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)目(mu)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)。需(xu)要說明的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)是(shi)：494的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de){16}腳(jiao)電(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)高(gao)(gao)(gao)低只能改變(bian)輸(shu)(shu)(shu)出(chu)(chu)脈(mo)(mo)沖的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)寬度(du)(du)，但(dan)不影(ying)響494的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de){4}腳(jiao)電(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)狀(zhuang)態，而339的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de){5}腳(jiao)電(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)一(yi)旦(dan)超過(guo){4}腳(jiao)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)電(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)，339的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de){2}腳(jiao)就送(song)(song)出(chu)(chu)高(gao)(gao)(gao)電(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)去封(feng)鎖449的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)脈(mo)(mo)沖輸(shu)(shu)(shu)出(chu)(chu)，終(zhong)止±5V、±12V、＋3．3V電(dian)(dian)源(yuan)(yuan)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)輸(shu)(shu)(shu)出(chu)(chu)，同時(shi)(shi){2}腳(jiao)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)高(gao)(gao)(gao)電(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)經(jing)R59和二極(ji)(ji)管D39反饋(kui)到(dao)(dao){5}腳(jiao)，維(wei)(wei)持(chi){5}腳(jiao)處于高(gao)(gao)(gao)電(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)狀(zhuang)態，此時(shi)(shi)若過(guo)載(zai)或短(duan)(duan)路狀(zhuang)態消失(shi)，494的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de){4}腳(jiao)仍(reng)維(wei)(wei)持(chi)高(gao)(gao)(gao)電(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)，±5V與±12V、＋3．3V電(dian)(dian)源(yuan)(yuan)仍(reng)不能輸(shu)(shu)(shu)出(chu)(chu)，只有切斷交流(liu)(liu)市電(dian)(dian)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)輸(shu)(shu)(shu)入(ru)，再(zai)(zai)重新接通交流(liu)(liu)電(dian)(dian)，方(fang)可再(zai)(zai)次開機。

四、過壓保護

過(guo)電(dian)(dian)壓(ya)(ya)保(bao)護由(you)R17和穩壓(ya)(ya)管Z02并聯電(dian)(dian)路(lu)從(cong)＋5V采樣，經D37送(song)到(dao)339的(de)(de){5}腳(jiao)(jiao)。若＋5V電(dian)(dian)源由(you)于某種(zhong)原因(yin)升(sheng)(sheng)高，339的(de)(de){5}腳(jiao)(jiao)電(dian)(dian)平也會隨之升(sheng)(sheng)高，當超過(guo){4}腳(jiao)(jiao)電(dian)(dian)平時，{2}腳(jiao)(jiao)即送(song)出(chu)高電(dian)(dian)平去494的(de)(de){4}腳(jiao)(jiao)，封鎖±5V、±12V、＋3．3V電(dian)(dian)源的(de)(de)輸出(chu)，達到(dao)過(guo)電(dian)(dian)壓(ya)(ya)保(bao)護的(de)(de)目的(de)(de)。正常工(gong)作(zuo)時，R17上(shang)的(de)(de)壓(ya)(ya)降(jiang)不大(da)，Z02截止送(song)到(dao){5}腳(jiao)(jiao)的(de)(de)電(dian)(dian)壓(ya)(ya)較(jiao)低，若＋5V電(dian)(dian)源的(de)(de)電(dian)(dian)壓(ya)(ya)上(shang)升(sheng)(sheng)，使(shi)R17上(shang)的(de)(de)壓(ya)(ya)降(jiang)超過(guo)Z02的(de)(de)穩壓(ya)(ya)值(zhi)，Z02導通，＋5V電(dian)(dian)源上(shang)升(sheng)(sheng)后的(de)(de)電(dian)(dian)壓(ya)(ya)值(zhi)全(quan)部加(jia)到(dao)339的(de)(de){5}腳(jiao)(jiao)上(shang)，促(cu)使(shi)其快速封鎖494脈(mo)沖的(de)(de)輸出(chu)，以(yi)保(bao)護電(dian)(dian)源。

五、欠壓保護

欠壓(ya)保護從－5V的(de)(de)D32及(ji)－12V處(chu)的(de)(de)R14取樣，經R34和D37送(song)到(dao)339的(de)(de){5}腳。若(ruo)因某種(zhong)原因使輸(shu)出電(dian)(dian)(dian)壓(ya)過低(di)時，－12V及(ji) －5V電(dian)(dian)(dian)壓(ya)的(de)(de)負(fu)值也會隨之減小，也就是電(dian)(dian)(dian)壓(ya)值上升，經R34及(ji)D37送(song)往339的(de)(de){5}腳使電(dian)(dian)(dian)平上升，339的(de)(de){2}腳送(song)出高電(dian)(dian)(dian)平到(dao)494的(de)(de){4}腳，從而封鎖 449脈沖(chong)的(de)(de)輸(shu)出，實現欠壓(ya)保護。二極管D32在導(dao)通(tong)時，其電(dian)(dian)(dian)壓(ya)降與通(tong)過的(de)(de)電(dian)(dian)(dian)流(liu)基本(ben)無(wu)關(guan)，保持(chi)在0．6V～0．7V，于是－5V電(dian)(dian)(dian)壓(ya)的(de)(de)減少量會全(quan)部(bu)傳(chuan)送(song)到(dao)D32的(de)(de)負(fu)端，提高了欠壓(ya)保護的(de)(de)靈敏度(du)。