臺式機電源電路圖原理(li)分析 臺式機電源是如何(he)實現(xian)多種保護功能的(de)

ATX電(dian)源的控制電(dian)路(lu)如上圖。控制電(dian)路(lu)采用TL494及(ji)LM339集(ji)成電(dian)路(lu)（以下(xia)簡稱494和339）。494是雙排16腳集(ji)成電(dian)路(lu)，工作(zuo)(zuo)電(dian)壓(ya)7～40V。它含有由{14}腳輸出(chu)的＋5V基準電(dian)源，輸出(chu)電(dian)壓(ya)為＋5V（±0．05V），最大輸出(chu)電(dian)流250mA；一個頻率可調(diao)(diao)的鋸齒波產生電(dian)路(lu)，振蕩頻率由{5}腳外接電(dian)容及(ji){6}腳外接電(dian)阻來決定。{13}腳為高(gao)電(dian)平時，由{8}腳及(ji){11}腳輸出(chu)雙路(lu)反相（即推挽(wan)工作(zuo)(zuo)方式）的脈(mo)寬調(diao)(diao)制信號。

比較器是一(yi)種運算(suan)放大器，符號用三角形表示，它有一(yi)個同相輸入端(duan)(duan)“＋”；一(yi)個反相輸入端(duan)(duan)“－”和一(yi)個輸出(chu)端(duan)(duan)。

比(bi)(bi)較(jiao)(jiao)器(qi)(qi)(qi)(qi)同(tong)(tong)相(xiang)(xiang)(xiang)(xiang)端(duan)(duan)(duan)電(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)若高(gao)于反相(xiang)(xiang)(xiang)(xiang)端(duan)(duan)(duan)電(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)，則(ze)(ze)輸(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)端(duan)(duan)(duan)輸(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)高(gao)電(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)；反之輸(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)低(di)電(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)。494內的(de)(de)(de)(de)(de)(de)比(bi)(bi)較(jiao)(jiao)放(fang)(fang)大器(qi)(qi)(qi)(qi)有(you)四個(ge)，為(wei)(wei)(wei)敘述方便，在(zai)上(shang)圖中(zhong)(zhong)用(yong)小(xiao)寫字母a、b、c、d來表示。其中(zhong)(zhong)a是死區時(shi)間(jian)(jian)比(bi)(bi)較(jiao)(jiao)器(qi)(qi)(qi)(qi)。因兩(liang)個(ge)作逆變工作的(de)(de)(de)(de)(de)(de)三極管(guan)(guan)串(chuan)聯后接(jie)(jie)(jie)到＋310V的(de)(de)(de)(de)(de)(de)直(zhi)(zhi)(zhi)流電(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)上(shang)，若兩(liang)個(ge)三極管(guan)(guan)同(tong)(tong)時(shi)導(dao)通(tong)，就會形(xing)成對(dui)(dui)直(zhi)(zhi)(zhi)流電(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)的(de)(de)(de)(de)(de)(de)短(duan)(duan)路。兩(liang)個(ge)三極管(guan)(guan)同(tong)(tong)時(shi)導(dao)通(tong)可能發生在(zai)一(yi)(yi)(yi)個(ge)管(guan)(guan)子(zi)從截(jie)止(zhi)(zhi)轉(zhuan)為(wei)(wei)(wei)導(dao)通(tong)，而另一(yi)(yi)(yi)個(ge)管(guan)(guan)子(zi)由(you)導(dao)通(tong)轉(zhuan)為(wei)(wei)(wei)截(jie)止(zhi)(zhi)的(de)(de)(de)(de)(de)(de)時(shi)候。因為(wei)(wei)(wei)管(guan)(guan)子(zi)在(zai)轉(zhuan)換(huan)時(shi)有(you)時(shi)間(jian)(jian)的(de)(de)(de)(de)(de)(de)延遲，截(jie)止(zhi)(zhi)的(de)(de)(de)(de)(de)(de)管(guan)(guan)子(zi)已經轉(zhuan)為(wei)(wei)(wei)導(dao)通(tong)了(le)(le)(le)，但導(dao)通(tong)的(de)(de)(de)(de)(de)(de)管(guan)(guan)子(zi)尚未完全轉(zhuan)為(wei)(wei)(wei)截(jie)止(zhi)(zhi)，于是兩(liang)個(ge)管(guan)(guan)子(zi)都呈(cheng)導(dao)通(tong)狀(zhuang)態而形(xing)成對(dui)(dui)直(zhi)(zhi)(zhi)流電(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)的(de)(de)(de)(de)(de)(de)短(duan)(duan)路。為(wei)(wei)(wei)防止(zhi)(zhi)這樣的(de)(de)(de)(de)(de)(de)事情發生，494設置了(le)(le)(le)死區時(shi)間(jian)(jian)比(bi)(bi)較(jiao)(jiao)器(qi)(qi)(qi)(qi)a。從圖中(zhong)(zhong)可以看出(chu)(chu)(chu)，在(zai)比(bi)(bi)較(jiao)(jiao)器(qi)(qi)(qi)(qi)a的(de)(de)(de)(de)(de)(de)反相(xiang)(xiang)(xiang)(xiang)輸(shu)(shu)(shu)(shu)(shu)入(ru)(ru)(ru)端(duan)(duan)(duan)串(chuan)聯了(le)(le)(le)一(yi)(yi)(yi)個(ge)“電(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)”，正(zheng)極接(jie)(jie)(jie)反相(xiang)(xiang)(xiang)(xiang)端(duan)(duan)(duan)，負極接(jie)(jie)(jie)494的(de)(de)(de)(de)(de)(de){4}腳(jiao)。A比(bi)(bi)較(jiao)(jiao)器(qi)(qi)(qi)(qi)同(tong)(tong)相(xiang)(xiang)(xiang)(xiang)端(duan)(duan)(duan)輸(shu)(shu)(shu)(shu)(shu)入(ru)(ru)(ru)的(de)(de)(de)(de)(de)(de)鋸(ju)(ju)齒波信號，只(zhi)有(you)大于“電(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)”電(dian)(dian)(dian)(dian)(dian)(dian)壓的(de)(de)(de)(de)(de)(de)部(bu)分才有(you)輸(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)，在(zai)三極管(guan)(guan)導(dao)通(tong)變為(wei)(wei)(wei)截(jie)止(zhi)(zhi)與(yu)(yu)(yu)截(jie)止(zhi)(zhi)轉(zhuan)為(wei)(wei)(wei)導(dao)通(tong)期間(jian)(jian)，也就是死區時(shi)間(jian)(jian)，494沒有(you)脈(mo)沖(chong)(chong)輸(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)，避免了(le)(le)(le)對(dui)(dui)直(zhi)(zhi)(zhi)流電(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)的(de)(de)(de)(de)(de)(de)短(duan)(duan)路。死區時(shi)間(jian)(jian)還(huan)可由(you){4}腳(jiao)外接(jie)(jie)(jie)的(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)來控(kong)制，{4}腳(jiao)的(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)上(shang)升，死區時(shi)間(jian)(jian)變寬，494輸(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)的(de)(de)(de)(de)(de)(de)脈(mo)沖(chong)(chong)就變窄了(le)(le)(le)，若{4}腳(jiao)的(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)超過了(le)(le)(le)鋸(ju)(ju)齒波的(de)(de)(de)(de)(de)(de)峰(feng)值電(dian)(dian)(dian)(dian)(dian)(dian)壓，494就進入(ru)(ru)(ru)了(le)(le)(le)保護狀(zhuang)態，{8}腳(jiao)和(he){11}腳(jiao)就不輸(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)脈(mo)沖(chong)(chong)了(le)(le)(le)。494內部(bu)還(huan)有(you)3個(ge)二(er)(er)輸(shu)(shu)(shu)(shu)(shu)入(ru)(ru)(ru)端(duan)(duan)(duan)與(yu)(yu)(yu)門（用(yong)1、2、3表示）、兩(liang)個(ge)二(er)(er)輸(shu)(shu)(shu)(shu)(shu)入(ru)(ru)(ru)端(duan)(duan)(duan)與(yu)(yu)(yu)非門、反相(xiang)(xiang)(xiang)(xiang)器(qi)(qi)(qi)(qi)、T觸發器(qi)(qi)(qi)(qi)等(deng)電(dian)(dian)(dian)(dian)(dian)(dian)路。與(yu)(yu)(yu)門是這樣一(yi)(yi)(yi)種電(dian)(dian)(dian)(dian)(dian)(dian)路，只(zhi)有(you)所有(you)的(de)(de)(de)(de)(de)(de)輸(shu)(shu)(shu)(shu)(shu)入(ru)(ru)(ru)端(duan)(duan)(duan)都是高(gao)電(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)，輸(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)端(duan)(duan)(duan)才能輸(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)高(gao)電(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)；若有(you)一(yi)(yi)(yi)個(ge)輸(shu)(shu)(shu)(shu)(shu)入(ru)(ru)(ru)端(duan)(duan)(duan)為(wei)(wei)(wei)低(di)電(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)，則(ze)(ze)輸(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)端(duan)(duan)(duan)輸(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)低(di)電(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)。反相(xiang)(xiang)(xiang)(xiang)器(qi)(qi)(qi)(qi)的(de)(de)(de)(de)(de)(de)作用(yong)是把輸(shu)(shu)(shu)(shu)(shu)入(ru)(ru)(ru)信號隔(ge)離放(fang)(fang)大后反相(xiang)(xiang)(xiang)(xiang)輸(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)。與(yu)(yu)(yu)非門則(ze)(ze)相(xiang)(xiang)(xiang)(xiang)當(dang)于一(yi)(yi)(yi)個(ge)與(yu)(yu)(yu)門和(he)一(yi)(yi)(yi)個(ge)反相(xiang)(xiang)(xiang)(xiang)器(qi)(qi)(qi)(qi)的(de)(de)(de)(de)(de)(de)組合。T觸發器(qi)(qi)(qi)(qi)的(de)(de)(de)(de)(de)(de)作用(yong)是：每(mei)輸(shu)(shu)(shu)(shu)(shu)入(ru)(ru)(ru)一(yi)(yi)(yi)個(ge)脈(mo)沖(chong)(chong)，輸(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)端(duan)(duan)(duan)的(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)就變化(hua)一(yi)(yi)(yi)次。如輸(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)端(duan)(duan)(duan)Q為(wei)(wei)(wei)低(di)電(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)，輸(shu)(shu)(shu)(shu)(shu)入(ru)(ru)(ru)一(yi)(yi)(yi)個(ge)脈(mo)沖(chong)(chong)后，Q變為(wei)(wei)(wei)高(gao)電(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)，再(zai)輸(shu)(shu)(shu)(shu)(shu)入(ru)(ru)(ru)一(yi)(yi)(yi)個(ge)脈(mo)沖(chong)(chong)，Q又回到低(di)電(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)。

339是四比(bi)較(jiao)(jiao)(jiao)器(qi)集成電(dian)(dian)(dian)路(lu)。 LM339集成塊內部(bu)裝有四個(ge)(ge)(ge)(ge)獨立的(de)(de)(de)電(dian)(dian)(dian)壓(ya)(ya)(ya)比(bi)較(jiao)(jiao)(jiao)器(qi)，每個(ge)(ge)(ge)(ge)比(bi)較(jiao)(jiao)(jiao)器(qi)有兩個(ge)(ge)(ge)(ge)輸(shu)入(ru)(ru)端(duan)(duan)(duan)和一(yi)(yi)個(ge)(ge)(ge)(ge)輸(shu)出(chu)端(duan)(duan)(duan)。兩個(ge)(ge)(ge)(ge)輸(shu)入(ru)(ru)端(duan)(duan)(duan)一(yi)(yi)個(ge)(ge)(ge)(ge)稱(cheng)(cheng)為同(tong)相輸(shu)入(ru)(ru)端(duan)(duan)(duan)，用(yong)“+”表(biao)示，另一(yi)(yi)個(ge)(ge)(ge)(ge)稱(cheng)(cheng)為反(fan)相輸(shu)入(ru)(ru)端(duan)(duan)(duan)，用(yong)“-”表(biao)示。用(yong)作比(bi)較(jiao)(jiao)(jiao)兩個(ge)(ge)(ge)(ge)電(dian)(dian)(dian)壓(ya)(ya)(ya)時，任(ren)意一(yi)(yi)個(ge)(ge)(ge)(ge)輸(shu)入(ru)(ru)端(duan)(duan)(duan)加一(yi)(yi)個(ge)(ge)(ge)(ge)固定電(dian)(dian)(dian)壓(ya)(ya)(ya)做參考(kao)電(dian)(dian)(dian)壓(ya)(ya)(ya)（也稱(cheng)(cheng)為門限電(dian)(dian)(dian)平(ping)，它可選擇LM339輸(shu)入(ru)(ru)共模范圍(wei)的(de)(de)(de)任(ren)何一(yi)(yi)點），另一(yi)(yi)端(duan)(duan)(duan)加一(yi)(yi)個(ge)(ge)(ge)(ge)待比(bi)較(jiao)(jiao)(jiao)的(de)(de)(de)信號電(dian)(dian)(dian)壓(ya)(ya)(ya)。當“+”端(duan)(duan)(duan)電(dian)(dian)(dian)壓(ya)(ya)(ya)高(gao)于(yu)(yu)(yu)“-”端(duan)(duan)(duan)時，輸(shu)出(chu)管(guan)截(jie)止(zhi)，相當于(yu)(yu)(yu)輸(shu)出(chu)端(duan)(duan)(duan)開路(lu)。當“-”端(duan)(duan)(duan)電(dian)(dian)(dian)壓(ya)(ya)(ya)高(gao)于(yu)(yu)(yu)“+”端(duan)(duan)(duan)時，輸(shu)出(chu)管(guan)飽和，相當于(yu)(yu)(yu)輸(shu)出(chu)端(duan)(duan)(duan)接(jie)低電(dian)(dian)(dian)位(wei)。兩個(ge)(ge)(ge)(ge)輸(shu)入(ru)(ru)端(duan)(duan)(duan)電(dian)(dian)(dian)壓(ya)(ya)(ya)差別(bie)大于(yu)(yu)(yu)10mV就能(neng)確(que)保輸(shu)出(chu)能(neng)從一(yi)(yi)種狀(zhuang)態可靠(kao)地(di)轉換(huan)到另一(yi)(yi)種狀(zhuang)態， LM339的(de)(de)(de)輸(shu)出(chu)端(duan)(duan)(duan)相當于(yu)(yu)(yu)一(yi)(yi)只(zhi)不接(jie)集電(dian)(dian)(dian)極電(dian)(dian)(dian)阻的(de)(de)(de)晶(jing)體(ti)三(san)極管(guan)，在使(shi)用(yong)時輸(shu)出(chu)端(duan)(duan)(duan)到正電(dian)(dian)(dian)源一(yi)(yi)般(ban)須接(jie)一(yi)(yi)只(zhi)電(dian)(dian)(dian)阻（稱(cheng)(cheng)為上(shang)(shang)拉(la)電(dian)(dian)(dian)阻，選3-15K）。選不同(tong)阻值的(de)(de)(de)上(shang)(shang)拉(la)電(dian)(dian)(dian)阻會影(ying)響輸(shu)出(chu)端(duan)(duan)(duan)高(gao)電(dian)(dian)(dian)位(wei)的(de)(de)(de)值。因為當輸(shu)出(chu)晶(jing)體(ti)三(san)極管(guan)截(jie)止(zhi)時，它的(de)(de)(de)集電(dian)(dian)(dian)極電(dian)(dian)(dian)壓(ya)(ya)(ya)基本上(shang)(shang)取(qu)決于(yu)(yu)(yu)上(shang)(shang)拉(la)電(dian)(dian)(dian)阻與負載的(de)(de)(de)值。

按管腳的順(shun)序把內部(bu)四個比較器設(she)為A、B 、C 、D 比較器。494和(he)339再配合其他電(dian)路，共同完成(cheng)ATX電(dian)源的穩壓，產生PW－OK信(xin)號及各(ge)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)(yuan)接通市電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)后(hou)(hou)，輔助電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)立即工(gong)作(zuo)(zuo)。一方面(mian)輸(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)源(yuan)(yuan)，同(tong)時(shi)向(xiang)494的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de){12}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)提供十(shi)幾(ji)伏(fu)(fu)到(dao)二十(shi)多伏(fu)(fu)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)直流電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)。494從(cong){14}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)輸(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)＋5V基(ji)準電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)，鋸齒波(bo)振(zhen)(zhen)蕩(dang)器(qi)(qi)(qi)(qi)(qi)也(ye)開(kai)(kai)始起振(zhen)(zhen)工(gong)作(zuo)(zuo)。若主(zhu)(zhu)機(ji)未開(kai)(kai)機(ji)，PS－ON信(xin)(xin)號(hao)(hao)(hao)為(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)，經(jing)(jing)(jing)(jing)R37使(shi)339的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)B比(bi)(bi)較(jiao)(jiao)(jiao)(jiao)器(qi)(qi)(qi)(qi)(qi){6}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)亦(yi)(yi)為(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)，因(yin)電(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)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)高(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)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)，B比(bi)(bi)較(jiao)(jiao)(jiao)(jiao)器(qi)(qi)(qi)(qi)(qi)輸(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)出(chu)(chu)(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)，經(jing)(jing)(jing)(jing)D36的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)鉗位作(zuo)(zuo)用，A比(bi)(bi)較(jiao)(jiao)(jiao)(jiao)器(qi)(qi)(qi)(qi)(qi)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)反相端(duan)(duan){4}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)亦(yi)(yi)為(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)，其(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)低(di)(di)于(yu)同(tong)相端(duan)(duan){5}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)的(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)，輸(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)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)，經(jing)(jing)(jing)(jing)R41使(shi)494的(de)(de)(de)(de)(de)(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)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)，故494內部的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)死(si)區(qu)時(shi)間(jian)比(bi)(bi)較(jiao)(jiao)(jiao)(jiao)器(qi)(qi)(qi)(qi)(qi)a輸(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)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)，與門(men)1也(ye)因(yin)此(ci)輸(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)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)并進而使(shi)與門(men)2和與門(men)3輸(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)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)，封(feng)鎖了振(zhen)(zhen)蕩(dang)器(qi)(qi)(qi)(qi)(qi)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)輸(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(mo)沖(chong)(chong)輸(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)源(yuan)(yuan)無(wu)±5V、±12V、＋3．3V電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)輸(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)，主(zhu)(zhu)機(ji)處于(yu)待機(ji)狀態(tai)。因(yin)＋5V、＋12V電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)輸(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)為(wei)零，經(jing)(jing)(jing)(jing)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻R15、R16使(shi)494的(de)(de)(de)(de)(de)(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)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)亦(yi)(yi)為(wei)零，494的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)c比(bi)(bi)較(jiao)(jiao)(jiao)(jiao)器(qi)(qi)(qi)(qi)(qi)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)輸(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)出(chu)(chu)(chu)(chu)(chu)(chu)亦(yi)(yi)為(wei)零，經(jing)(jing)(jing)(jing)R48使(shi)339的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de){9}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)亦(yi)(yi)為(wei)零電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)，故339的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)C比(bi)(bi)較(jiao)(jiao)(jiao)(jiao)器(qi)(qi)(qi)(qi)(qi)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)輸(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)零電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)。另(ling)外，339的(de)(de)(de)(de)(de)(de)(de)(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)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)信(xin)(xin)號(hao)(hao)(hao)因(yin)D34的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)鉗位作(zuo)(zuo)用，也(ye)使(shi){14}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)為(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)，經(jing)(jing)(jing)(jing)R50和R63使(shi){11}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)亦(yi)(yi)為(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)。因(yin)此(ci)D比(bi)(bi)較(jiao)(jiao)(jiao)(jiao)器(qi)(qi)(qi)(qi)(qi)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)輸(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)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)，也(ye)就是PW－OK信(xin)(xin)號(hao)(hao)(hao)為(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)，主(zhu)(zhu)機(ji)不會工(gong)作(zuo)(zuo)。開(kai)(kai)啟主(zhu)(zhu)機(ji)時(shi)，通過人工(gong)或遙控(kong)操作(zuo)(zuo)閉(bi)合了與PS－ON相關的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)開(kai)(kai)關，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)，經(jing)(jing)(jing)(jing)R37使(shi)339的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)反相端(duan)(duan){6}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)為(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)，B比(bi)(bi)較(jiao)(jiao)(jiao)(jiao)器(qi)(qi)(qi)(qi)(qi){1}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)輸(shu)(shu)(shu)(shu)出(chu)(chu)(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)，D35、D36反偏截止，A比(bi)(bi)較(jiao)(jiao)(jiao)(jiao)器(qi)(qi)(qi)(qi)(qi)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)輸(shu)(shu)(shu)(shu)出(chu)(chu)(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)則由{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)(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)決定。正常工(gong)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)平(ping)(ping)(ping)(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)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)，{2}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)輸(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)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)，經(jing)(jing)(jing)(jing)R41送(song)到(dao)494的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de){4}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)，使(shi){4}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)的(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)變為(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)，鋸齒波(bo)振(zhen)(zhen)蕩(dang)信(xin)(xin)號(hao)(hao)(hao)可以從(cong)死(si)區(qu)時(shi)間(jian)比(bi)(bi)較(jiao)(jiao)(jiao)(jiao)器(qi)(qi)(qi)(qi)(qi)a輸(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)脈(mo)沖(chong)(chong)信(xin)(xin)號(hao)(hao)(hao)，另(ling)一方面(mian)，振(zhen)(zhen)蕩(dang)信(xin)(xin)號(hao)(hao)(hao)送(song)到(dao)了PWM比(bi)(bi)較(jiao)(jiao)(jiao)(jiao)器(qi)(qi)(qi)(qi)(qi)b的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)同(tong)相輸(shu)(shu)(shu)(shu)入端(duan)(duan)，PWM比(bi)(bi)較(jiao)(jiao)(jiao)(jiao)器(qi)(qi)(qi)(qi)(qi)輸(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)的(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)寬度，則是由494的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de){1}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)的(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)（也(ye)就是負(fu)載的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)大小）與{16}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)的(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)來決定。PWM比(bi)(bi)較(jiao)(jiao)(jiao)(jiao)器(qi)(qi)(qi)(qi)(qi)輸(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)的(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)(hou)經(jing)(jing)(jing)(jing)緩沖(chong)(chong)放(fang)大器(qi)(qi)(qi)(qi)(qi)放(fang)大后(hou)(hou)，從(cong){8}、{11}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)輸(shu)(shu)(shu)(shu)出(chu)(chu)(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)(yuan)向(xiang)主(zhu)(zhu)機(ji)輸(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)源(yuan)(yuan)。此(ci)過程因(yin)C35的(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)有數百(bai)毫秒(miao)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)延(yan)時(shi)，但對主(zhu)(zhu)機(ji)開(kai)(kai)機(ji)并無(wu)影(ying)響。494的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de){1}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)從(cong)＋5V、＋12V經(jing)(jing)(jing)(jing)取樣電(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)壓，其(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)略高(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)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)，{3}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)輸(shu)(shu)(shu)(shu)出(chu)(chu)(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)，經(jing)(jing)(jing)(jing)R48使(shi)339的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de){9}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)得到(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)，其(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)高(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)平(ping)(ping)(ping)(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)出(chu)(chu)(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)，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)經(jing)(jing)(jing)(jing)R50與基(ji)準＋5V電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)經(jing)(jing)(jing)(jing)R64共同(tong)對C39充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)，經(jing)(jing)(jing)(jing)數百(bai)毫秒(miao)后(hou)(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)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)升到(dao)高(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)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)時(shi)，D比(bi)(bi)較(jiao)(jiao)(jiao)(jiao)器(qi)(qi)(qi)(qi)(qi){13}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)輸(shu)(shu)(shu)(shu)出(chu)(chu)(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)，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)經(jing)(jing)(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)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)狀態(tai)，故{13}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)輸(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)穩(wen)定的(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) PW－OK信(xin)(xin)號(hao)(hao)(hao)，主(zhu)(zhu)機(ji)檢(jian)測到(dao)此(ci)信(xin)(xin)號(hao)(hao)(hao)后(hou)(hou)即開(kai)(kai)始正常工(gong)作(zuo)(zuo)。

關機時，主機內開(kai)關使PS－ON呈高電(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)，此時(shi)(shi)(shi)339的(de)(de)(de){6}腳電(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)高于(yu){7}腳，{1}腳輸出(chu)低(di)(di)電(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)，因(yin)(yin)(yin)二極管D34的(de)(de)(de)鉗(qian)位作(zuo)用，{14}腳呈低(di)(di)電(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)，C39對C比(bi)較器及B比(bi)較器放(fang)(fang)(fang)電(dian)(dian)(dian)(dian)(dian)(dian)，很快(kuai){11}腳呈低(di)(di)電(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)，{13}腳輸出(chu)低(di)(di)電(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)，即PW－OK信號呈低(di)(di)電(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)。在339的(de)(de)(de){1}腳為低(di)(di)電(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)時(shi)(shi)(shi)，經D36使{4}臆腳為低(di)(di)電(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)，{2}腳輸出(chu)高電(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)，經R41傳送到494的(de)(de)(de){4}腳，但因(yin)(yin)(yin)C35電(dian)(dian)(dian)(dian)(dian)(dian)位不能突變，經數(shu)百毫秒的(de)(de)(de)放(fang)(fang)(fang)電(dian)(dian)(dian)(dian)(dian)(dian)后方使494的(de)(de)(de){4}腳轉為高電(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)，從而封鎖正負脈沖的(de)(de)(de)輸出(chu) ，主(zhu)機(ji)進入(ru)待機(ji)狀(zhuang)態。上述的(de)(de)(de)過程中，關機(ji)時(shi)(shi)(shi)C39和(he)C35都(dou)要放(fang)(fang)(fang)電(dian)(dian)(dian)(dian)(dian)(dian)，但因(yin)(yin)(yin)放(fang)(fang)(fang)電(dian)(dian)(dian)(dian)(dian)(dian)時(shi)(shi)(shi)間(jian)常數(shu)不同，C39放(fang)(fang)(fang)電(dian)(dian)(dian)(dian)(dian)(dian)較快(kuai)，故PW－OK信號先(xian)(xian)于(yu)各電(dian)(dian)(dian)(dian)(dian)(dian)源變成低(di)(di)電(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)，滿足了主(zhu)機(ji)關機(ji)的(de)(de)(de)需要。此外，關機(ji)時(shi)(shi)(shi)因(yin)(yin)(yin)各路輸出(chu)電(dian)(dian)(dian)(dian)(dian)(dian)源的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)解(jie)電(dian)(dian)(dian)(dian)(dian)(dian)容放(fang)(fang)(fang)電(dian)(dian)(dian)(dian)(dian)(dian)需要時(shi)(shi)(shi)間(jian)，也使PW－OK信號先(xian)(xian)于(yu)各電(dian)(dian)(dian)(dian)(dian)(dian)源回(hui)到低(di)(di)電(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)。

二、 穩壓

494的(de)(de){2}腳經R47與基準電(dian)(dian)(dian)壓(ya)＋5V相連(lian)，維持(chi)較(jiao)好(hao)的(de)(de)穩定電(dian)(dian)(dian)壓(ya)，而{1}腳則(ze)與取(qu)樣電(dian)(dian)(dian)阻R15、R16與＋5V、＋12V相連(lian)接，正常的(de)(de)情(qing)況下，{1}腳電(dian)(dian)(dian)平與{2}腳電(dian)(dian)(dian)平相等或(huo)(huo)略(lve)高(gao)。當(dang)輸(shu)(shu)(shu)(shu)出(chu)(chu)電(dian)(dian)(dian)壓(ya)升高(gao)時（無論＋5V或(huo)(huo)＋12V），{1}腳電(dian)(dian)(dian)平高(gao)于(yu){2}腳電(dian)(dian)(dian)平，c比較(jiao)器輸(shu)(shu)(shu)(shu)出(chu)(chu)誤差(cha)電(dian)(dian)(dian)壓(ya)與鋸齒波振(zhen)蕩(dang)脈沖(chong)在(zai)(zai)PWM比較(jiao)器b進行比較(jiao)使輸(shu)(shu)(shu)(shu)出(chu)(chu)脈沖(chong)寬度變窄，輸(shu)(shu)(shu)(shu)出(chu)(chu)電(dian)(dian)(dian)壓(ya)回(hui)(hui)落到(dao)標(biao)準值，反(fan)之則(ze)促使振(zhen)蕩(dang)脈沖(chong)寬度增(zeng)加，輸(shu)(shu)(shu)(shu)出(chu)(chu)電(dian)(dian)(dian)壓(ya)回(hui)(hui)升。由于(yu)494內(nei)的(de)(de)放大器增(zeng)益很高(gao)，故(gu)穩壓(ya)精度很好(hao)。從(cong)穩壓(ya)的(de)(de)原理，我(wo)們可(ke)以(yi)得到(dao)ATX電(dian)(dian)(dian)源(yuan)輸(shu)(shu)(shu)(shu)出(chu)(chu)電(dian)(dian)(dian)壓(ya)偏高(gao)或(huo)(huo)偏低的(de)(de)維修(xiu)方法(fa)。如果輸(shu)(shu)(shu)(shu)出(chu)(chu)電(dian)(dian)(dian)壓(ya)偏低，可(ke)在(zai)(zai)494的(de)(de){1}腳對地(di)(di)并聯(lian)電(dian)(dian)(dian)阻，或(huo)(huo)是把(ba)R47的(de)(de)電(dian)(dian)(dian)阻增(zeng)大。要是電(dian)(dian)(dian)源(yuan)的(de)(de)輸(shu)(shu)(shu)(shu)出(chu)(chu)偏高(gao)，則(ze)可(ke)在(zai)(zai){2}腳對地(di)(di)并聯(lian)電(dian)(dian)(dian)阻，也可(ke)以(yi)用增(zeng)大R33或(huo)(huo)取(qu)下R69、R35來(lai)降低輸(shu)(shu)(shu)(shu)出(chu)(chu)電(dian)(dian)(dian)壓(ya)。

三、 過流保護

過(guo)流(liu)保(bao)護(hu)的(de)(de)(de)原理是基于負(fu)載愈(yu)(yu)大，Q3、Q4集電(dian)(dian)(dian)(dian)極的(de)(de)(de)脈(mo)沖(chong)電(dian)(dian)(dian)(dian)壓也愈(yu)(yu)高，也即(ji)是R13（1．5kΩ）上的(de)(de)(de)電(dian)(dian)(dian)(dian)壓也愈(yu)(yu)高，從這里采樣經D14整流(liu)和C36濾波(bo)，再(zai)(zai)經R54、R55并聯電(dian)(dian)(dian)(dian)阻與(yu)R51、R56、R58等組(zu)成(cheng)的(de)(de)(de)分(fen)壓電(dian)(dian)(dian)(dian)路送到494的(de)(de)(de){16}腳(jiao)(jiao)(jiao)(jiao)(jiao)。隨著負(fu)載的(de)(de)(de)加(jia)重(zhong)，{16}腳(jiao)(jiao)(jiao)(jiao)(jiao)的(de)(de)(de)電(dian)(dian)(dian)(dian)平(ping)(ping)(ping)也隨之(zhi)上升，當超(chao)過(guo){15}腳(jiao)(jiao)(jiao)(jiao)(jiao)的(de)(de)(de)電(dian)(dian)(dian)(dian)平(ping)(ping)(ping)時(shi)，誤差放大器輸出(chu)(chu)的(de)(de)(de)誤差電(dian)(dian)(dian)(dian)壓促使調制(zhi)脈(mo)沖(chong)的(de)(de)(de)寬(kuan)度變窄從而使負(fu)載電(dian)(dian)(dian)(dian)流(liu)減小。另外，從R56、R58并聯電(dian)(dian)(dian)(dian)阻獲得的(de)(de)(de)分(fen)壓再(zai)(zai)經R52送到339的(de)(de)(de){5}腳(jiao)(jiao)(jiao)(jiao)(jiao)，當{5}腳(jiao)(jiao)(jiao)(jiao)(jiao)的(de)(de)(de)電(dian)(dian)(dian)(dian)平(ping)(ping)(ping)超(chao)過(guo){4}腳(jiao)(jiao)(jiao)(jiao)(jiao)時(shi)，{2}腳(jiao)(jiao)(jiao)(jiao)(jiao)即(ji)輸出(chu)(chu)高電(dian)(dian)(dian)(dian)平(ping)(ping)(ping)送到494的(de)(de)(de){4}腳(jiao)(jiao)(jiao)(jiao)(jiao)，494停止輸出(chu)(chu)脈(mo)沖(chong)信號，終止±5V、±12V、＋3．3V電(dian)(dian)(dian)(dian)源(yuan)的(de)(de)(de)輸出(chu)(chu)，達(da)到過(guo)流(liu)及(ji)短(duan)(duan)路保(bao)護(hu)的(de)(de)(de)目的(de)(de)(de)。需要說明的(de)(de)(de)是：494的(de)(de)(de){16}腳(jiao)(jiao)(jiao)(jiao)(jiao)電(dian)(dian)(dian)(dian)平(ping)(ping)(ping)的(de)(de)(de)高低(di)只(zhi)能改變輸出(chu)(chu)脈(mo)沖(chong)的(de)(de)(de)寬(kuan)度，但(dan)不影(ying)響494的(de)(de)(de){4}腳(jiao)(jiao)(jiao)(jiao)(jiao)電(dian)(dian)(dian)(dian)平(ping)(ping)(ping)狀態(tai)，而339的(de)(de)(de){5}腳(jiao)(jiao)(jiao)(jiao)(jiao)電(dian)(dian)(dian)(dian)平(ping)(ping)(ping)一旦超(chao)過(guo){4}腳(jiao)(jiao)(jiao)(jiao)(jiao)的(de)(de)(de)電(dian)(dian)(dian)(dian)平(ping)(ping)(ping)，339的(de)(de)(de){2}腳(jiao)(jiao)(jiao)(jiao)(jiao)就送出(chu)(chu)高電(dian)(dian)(dian)(dian)平(ping)(ping)(ping)去封鎖(suo)449的(de)(de)(de)脈(mo)沖(chong)輸出(chu)(chu)，終止±5V、±12V、＋3．3V電(dian)(dian)(dian)(dian)源(yuan)的(de)(de)(de)輸出(chu)(chu)，同(tong)時(shi){2}腳(jiao)(jiao)(jiao)(jiao)(jiao)的(de)(de)(de)高電(dian)(dian)(dian)(dian)平(ping)(ping)(ping)經R59和二極管(guan)D39反饋(kui)到{5}腳(jiao)(jiao)(jiao)(jiao)(jiao)，維持{5}腳(jiao)(jiao)(jiao)(jiao)(jiao)處于高電(dian)(dian)(dian)(dian)平(ping)(ping)(ping)狀態(tai)，此時(shi)若過(guo)載或短(duan)(duan)路狀態(tai)消失，494的(de)(de)(de){4}腳(jiao)(jiao)(jiao)(jiao)(jiao)仍(reng)維持高電(dian)(dian)(dian)(dian)平(ping)(ping)(ping)，±5V與(yu)±12V、＋3．3V電(dian)(dian)(dian)(dian)源(yuan)仍(reng)不能輸出(chu)(chu)，只(zhi)有切斷交流(liu)市電(dian)(dian)(dian)(dian)的(de)(de)(de)輸入，再(zai)(zai)重(zhong)新接(jie)通交流(liu)電(dian)(dian)(dian)(dian)，方可再(zai)(zai)次開機。

四、過壓保護

過(guo)電(dian)(dian)(dian)(dian)壓(ya)(ya)保(bao)護(hu)(hu)由R17和(he)穩壓(ya)(ya)管Z02并(bing)聯(lian)電(dian)(dian)(dian)(dian)路從＋5V采(cai)樣，經D37送到(dao)(dao)339的(de)(de)(de)(de)(de){5}腳(jiao)。若(ruo)＋5V電(dian)(dian)(dian)(dian)源由于某種原因升(sheng)(sheng)高(gao)(gao)，339的(de)(de)(de)(de)(de){5}腳(jiao)電(dian)(dian)(dian)(dian)平(ping)也會隨之升(sheng)(sheng)高(gao)(gao)，當(dang)超(chao)過(guo){4}腳(jiao)電(dian)(dian)(dian)(dian)平(ping)時(shi)，{2}腳(jiao)即送出高(gao)(gao)電(dian)(dian)(dian)(dian)平(ping)去(qu)494的(de)(de)(de)(de)(de){4}腳(jiao)，封(feng)鎖±5V、±12V、＋3．3V電(dian)(dian)(dian)(dian)源的(de)(de)(de)(de)(de)輸出，達到(dao)(dao)過(guo)電(dian)(dian)(dian)(dian)壓(ya)(ya)保(bao)護(hu)(hu)的(de)(de)(de)(de)(de)目(mu)的(de)(de)(de)(de)(de)。正(zheng)常工作時(shi)，R17上(shang)的(de)(de)(de)(de)(de)壓(ya)(ya)降不大，Z02截止送到(dao)(dao){5}腳(jiao)的(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)壓(ya)(ya)較(jiao)低，若(ruo)＋5V電(dian)(dian)(dian)(dian)源的(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)壓(ya)(ya)上(shang)升(sheng)(sheng)，使R17上(shang)的(de)(de)(de)(de)(de)壓(ya)(ya)降超(chao)過(guo)Z02的(de)(de)(de)(de)(de)穩壓(ya)(ya)值(zhi)，Z02導通，＋5V電(dian)(dian)(dian)(dian)源上(shang)升(sheng)(sheng)后的(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)壓(ya)(ya)值(zhi)全部(bu)加到(dao)(dao)339的(de)(de)(de)(de)(de){5}腳(jiao)上(shang)，促使其快(kuai)速封(feng)鎖494脈沖的(de)(de)(de)(de)(de)輸出，以保(bao)護(hu)(hu)電(dian)(dian)(dian)(dian)源。

五、欠壓保護

欠壓(ya)保護(hu)(hu)從－5V的(de)(de)(de)D32及－12V處的(de)(de)(de)R14取樣，經R34和(he)D37送到339的(de)(de)(de){5}腳。若(ruo)因(yin)某種原因(yin)使輸(shu)出電(dian)(dian)壓(ya)過低時(shi)，－12V及 －5V電(dian)(dian)壓(ya)的(de)(de)(de)負(fu)值也會隨(sui)之(zhi)減(jian)(jian)小，也就是電(dian)(dian)壓(ya)值上升(sheng)，經R34及D37送往339的(de)(de)(de){5}腳使電(dian)(dian)平(ping)上升(sheng)，339的(de)(de)(de){2}腳送出高電(dian)(dian)平(ping)到494的(de)(de)(de){4}腳，從而封鎖 449脈沖的(de)(de)(de)輸(shu)出，實(shi)現欠壓(ya)保護(hu)(hu)。二極管(guan)D32在導通時(shi)，其電(dian)(dian)壓(ya)降與通過的(de)(de)(de)電(dian)(dian)流(liu)基(ji)本無(wu)關，保持在0．6V～0．7V，于是－5V電(dian)(dian)壓(ya)的(de)(de)(de)減(jian)(jian)少(shao)量會全(quan)部傳送到D32的(de)(de)(de)負(fu)端，提(ti)高了欠壓(ya)保護(hu)(hu)的(de)(de)(de)靈(ling)敏度(du)。