臺式機電源(yuan)電路圖原理分析 臺式機電源(yuan)是如何實現多(duo)種保護功能的

ATX電(dian)(dian)(dian)源(yuan)的控(kong)制電(dian)(dian)(dian)路(lu)(lu)(lu)(lu)(lu)如(ru)上圖(tu)。控(kong)制電(dian)(dian)(dian)路(lu)(lu)(lu)(lu)(lu)采用TL494及LM339集成電(dian)(dian)(dian)路(lu)(lu)(lu)(lu)(lu)（以下簡稱494和339）。494是雙排16腳(jiao)(jiao)(jiao)集成電(dian)(dian)(dian)路(lu)(lu)(lu)(lu)(lu)，工作(zuo)電(dian)(dian)(dian)壓(ya)7～40V。它含有由{14}腳(jiao)(jiao)(jiao)輸(shu)出(chu)(chu)的＋5V基準電(dian)(dian)(dian)源(yuan)，輸(shu)出(chu)(chu)電(dian)(dian)(dian)壓(ya)為(wei)＋5V（±0．05V），最大輸(shu)出(chu)(chu)電(dian)(dian)(dian)流(liu)250mA；一個頻(pin)率可(ke)調(diao)的鋸齒波產生電(dian)(dian)(dian)路(lu)(lu)(lu)(lu)(lu)，振蕩頻(pin)率由{5}腳(jiao)(jiao)(jiao)外接(jie)電(dian)(dian)(dian)容及{6}腳(jiao)(jiao)(jiao)外接(jie)電(dian)(dian)(dian)阻來決定。{13}腳(jiao)(jiao)(jiao)為(wei)高電(dian)(dian)(dian)平時，由{8}腳(jiao)(jiao)(jiao)及{11}腳(jiao)(jiao)(jiao)輸(shu)出(chu)(chu)雙路(lu)(lu)(lu)(lu)(lu)反(fan)相（即推挽工作(zuo)方式）的脈(mo)寬調(diao)制信號。

比較器(qi)是(shi)一種運算(suan)放大器(qi)，符號用(yong)三角形表示，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)(bi)較(jiao)(jiao)(jiao)(jiao)器(qi)(qi)同(tong)相端(duan)(duan)(duan)(duan)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)若高(gao)于(yu)(yu)反(fan)相端(duan)(duan)(duan)(duan)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)，則(ze)輸(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)端(duan)(duan)(duan)(duan)輸(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)高(gao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)；反(fan)之輸(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)低(di)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)。494內的(de)(de)(de)(de)(de)(de)(de)比(bi)(bi)較(jiao)(jiao)(jiao)(jiao)放大(da)(da)器(qi)(qi)有(you)(you)(you)四個(ge)(ge)，為(wei)敘述(shu)方(fang)便，在上(shang)(shang)圖中用小寫(xie)字(zi)母a、b、c、d來表示。其中a是(shi)死(si)(si)(si)區時(shi)(shi)間(jian)(jian)比(bi)(bi)較(jiao)(jiao)(jiao)(jiao)器(qi)(qi)。因兩(liang)個(ge)(ge)作逆變(bian)工(gong)作的(de)(de)(de)(de)(de)(de)(de)三(san)極(ji)(ji)管(guan)(guan)串(chuan)(chuan)聯后(hou)接(jie)到＋310V的(de)(de)(de)(de)(de)(de)(de)直流電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)上(shang)(shang)，若兩(liang)個(ge)(ge)三(san)極(ji)(ji)管(guan)(guan)同(tong)時(shi)(shi)導(dao)(dao)通(tong)(tong)(tong)(tong)，就(jiu)會形(xing)成對直流電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)的(de)(de)(de)(de)(de)(de)(de)短(duan)路(lu)。兩(liang)個(ge)(ge)三(san)極(ji)(ji)管(guan)(guan)同(tong)時(shi)(shi)導(dao)(dao)通(tong)(tong)(tong)(tong)可(ke)(ke)能發生(sheng)在一(yi)(yi)(yi)個(ge)(ge)管(guan)(guan)子從(cong)截(jie)止(zhi)(zhi)轉(zhuan)為(wei)導(dao)(dao)通(tong)(tong)(tong)(tong)，而另一(yi)(yi)(yi)個(ge)(ge)管(guan)(guan)子由(you)導(dao)(dao)通(tong)(tong)(tong)(tong)轉(zhuan)為(wei)截(jie)止(zhi)(zhi)的(de)(de)(de)(de)(de)(de)(de)時(shi)(shi)候(hou)。因為(wei)管(guan)(guan)子在轉(zhuan)換時(shi)(shi)有(you)(you)(you)時(shi)(shi)間(jian)(jian)的(de)(de)(de)(de)(de)(de)(de)延遲，截(jie)止(zhi)(zhi)的(de)(de)(de)(de)(de)(de)(de)管(guan)(guan)子已(yi)經轉(zhuan)為(wei)導(dao)(dao)通(tong)(tong)(tong)(tong)了(le)(le)，但導(dao)(dao)通(tong)(tong)(tong)(tong)的(de)(de)(de)(de)(de)(de)(de)管(guan)(guan)子尚未(wei)完(wan)全轉(zhuan)為(wei)截(jie)止(zhi)(zhi)，于(yu)(yu)是(shi)兩(liang)個(ge)(ge)管(guan)(guan)子都(dou)呈導(dao)(dao)通(tong)(tong)(tong)(tong)狀態而形(xing)成對直流電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)的(de)(de)(de)(de)(de)(de)(de)短(duan)路(lu)。為(wei)防(fang)止(zhi)(zhi)這樣的(de)(de)(de)(de)(de)(de)(de)事情發生(sheng)，494設置了(le)(le)死(si)(si)(si)區時(shi)(shi)間(jian)(jian)比(bi)(bi)較(jiao)(jiao)(jiao)(jiao)器(qi)(qi)a。從(cong)圖中可(ke)(ke)以看出(chu)(chu)(chu)(chu)，在比(bi)(bi)較(jiao)(jiao)(jiao)(jiao)器(qi)(qi)a的(de)(de)(de)(de)(de)(de)(de)反(fan)相輸(shu)(shu)(shu)(shu)(shu)入(ru)端(duan)(duan)(duan)(duan)串(chuan)(chuan)聯了(le)(le)一(yi)(yi)(yi)個(ge)(ge)“電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)”，正極(ji)(ji)接(jie)反(fan)相端(duan)(duan)(duan)(duan)，負(fu)極(ji)(ji)接(jie)494的(de)(de)(de)(de)(de)(de)(de){4}腳。A比(bi)(bi)較(jiao)(jiao)(jiao)(jiao)器(qi)(qi)同(tong)相端(duan)(duan)(duan)(duan)輸(shu)(shu)(shu)(shu)(shu)入(ru)的(de)(de)(de)(de)(de)(de)(de)鋸齒波(bo)信(xin)號，只(zhi)有(you)(you)(you)大(da)(da)于(yu)(yu)“電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)”電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)的(de)(de)(de)(de)(de)(de)(de)部(bu)分才(cai)(cai)有(you)(you)(you)輸(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)，在三(san)極(ji)(ji)管(guan)(guan)導(dao)(dao)通(tong)(tong)(tong)(tong)變(bian)為(wei)截(jie)止(zhi)(zhi)與(yu)截(jie)止(zhi)(zhi)轉(zhuan)為(wei)導(dao)(dao)通(tong)(tong)(tong)(tong)期(qi)間(jian)(jian)，也就(jiu)是(shi)死(si)(si)(si)區時(shi)(shi)間(jian)(jian)，494沒(mei)有(you)(you)(you)脈(mo)(mo)(mo)沖(chong)輸(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)，避免了(le)(le)對直流電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)的(de)(de)(de)(de)(de)(de)(de)短(duan)路(lu)。死(si)(si)(si)區時(shi)(shi)間(jian)(jian)還可(ke)(ke)由(you){4}腳外接(jie)的(de)(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)來控制(zhi)，{4}腳的(de)(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)上(shang)(shang)升，死(si)(si)(si)區時(shi)(shi)間(jian)(jian)變(bian)寬，494輸(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)的(de)(de)(de)(de)(de)(de)(de)脈(mo)(mo)(mo)沖(chong)就(jiu)變(bian)窄了(le)(le)，若{4}腳的(de)(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)超過了(le)(le)鋸齒波(bo)的(de)(de)(de)(de)(de)(de)(de)峰值電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)，494就(jiu)進入(ru)了(le)(le)保護狀態，{8}腳和(he)(he){11}腳就(jiu)不(bu)輸(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)脈(mo)(mo)(mo)沖(chong)了(le)(le)。494內部(bu)還有(you)(you)(you)3個(ge)(ge)二(er)輸(shu)(shu)(shu)(shu)(shu)入(ru)端(duan)(duan)(duan)(duan)與(yu)門(men)（用1、2、3表示）、兩(liang)個(ge)(ge)二(er)輸(shu)(shu)(shu)(shu)(shu)入(ru)端(duan)(duan)(duan)(duan)與(yu)非門(men)、反(fan)相器(qi)(qi)、T觸發器(qi)(qi)等電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)。與(yu)門(men)是(shi)這樣一(yi)(yi)(yi)種(zhong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)，只(zhi)有(you)(you)(you)所有(you)(you)(you)的(de)(de)(de)(de)(de)(de)(de)輸(shu)(shu)(shu)(shu)(shu)入(ru)端(duan)(duan)(duan)(duan)都(dou)是(shi)高(gao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)，輸(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)端(duan)(duan)(duan)(duan)才(cai)(cai)能輸(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)高(gao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)；若有(you)(you)(you)一(yi)(yi)(yi)個(ge)(ge)輸(shu)(shu)(shu)(shu)(shu)入(ru)端(duan)(duan)(duan)(duan)為(wei)低(di)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)，則(ze)輸(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)端(duan)(duan)(duan)(duan)輸(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)低(di)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)。反(fan)相器(qi)(qi)的(de)(de)(de)(de)(de)(de)(de)作用是(shi)把輸(shu)(shu)(shu)(shu)(shu)入(ru)信(xin)號隔離放大(da)(da)后(hou)反(fan)相輸(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)。與(yu)非門(men)則(ze)相當于(yu)(yu)一(yi)(yi)(yi)個(ge)(ge)與(yu)門(men)和(he)(he)一(yi)(yi)(yi)個(ge)(ge)反(fan)相器(qi)(qi)的(de)(de)(de)(de)(de)(de)(de)組合。T觸發器(qi)(qi)的(de)(de)(de)(de)(de)(de)(de)作用是(shi)：每輸(shu)(shu)(shu)(shu)(shu)入(ru)一(yi)(yi)(yi)個(ge)(ge)脈(mo)(mo)(mo)沖(chong)，輸(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)端(duan)(duan)(duan)(duan)的(de)(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)就(jiu)變(bian)化一(yi)(yi)(yi)次。如輸(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)端(duan)(duan)(duan)(duan)Q為(wei)低(di)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)，輸(shu)(shu)(shu)(shu)(shu)入(ru)一(yi)(yi)(yi)個(ge)(ge)脈(mo)(mo)(mo)沖(chong)后(hou)，Q變(bian)為(wei)高(gao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)，再輸(shu)(shu)(shu)(shu)(shu)入(ru)一(yi)(yi)(yi)個(ge)(ge)脈(mo)(mo)(mo)沖(chong)，Q又回(hui)到低(di)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)。

339是四(si)比較器集成電(dian)(dian)(dian)(dian)(dian)路(lu)。 LM339集成塊內(nei)部裝有(you)四(si)個(ge)獨立的(de)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)比較器，每個(ge)比較器有(you)兩(liang)個(ge)輸(shu)(shu)(shu)入端(duan)和一(yi)(yi)(yi)(yi)個(ge)輸(shu)(shu)(shu)出(chu)端(duan)。兩(liang)個(ge)輸(shu)(shu)(shu)入端(duan)一(yi)(yi)(yi)(yi)個(ge)稱(cheng)(cheng)為(wei)同(tong)相輸(shu)(shu)(shu)入端(duan)，用(yong)(yong)“+”表示，另(ling)一(yi)(yi)(yi)(yi)個(ge)稱(cheng)(cheng)為(wei)反相輸(shu)(shu)(shu)入端(duan)，用(yong)(yong)“-”表示。用(yong)(yong)作比較兩(liang)個(ge)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)時(shi)(shi)(shi)，任意一(yi)(yi)(yi)(yi)個(ge)輸(shu)(shu)(shu)入端(duan)加(jia)一(yi)(yi)(yi)(yi)個(ge)固(gu)定電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)做參考電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)（也稱(cheng)(cheng)為(wei)門限電(dian)(dian)(dian)(dian)(dian)平(ping)，它(ta)可(ke)選(xuan)擇(ze)LM339輸(shu)(shu)(shu)入共模(mo)范圍的(de)任何一(yi)(yi)(yi)(yi)點），另(ling)一(yi)(yi)(yi)(yi)端(duan)加(jia)一(yi)(yi)(yi)(yi)個(ge)待(dai)比較的(de)信號電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)。當(dang)(dang)“+”端(duan)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)高于(yu)(yu)(yu)“-”端(duan)時(shi)(shi)(shi)，輸(shu)(shu)(shu)出(chu)管(guan)截(jie)止(zhi)(zhi)，相當(dang)(dang)于(yu)(yu)(yu)輸(shu)(shu)(shu)出(chu)端(duan)開路(lu)。當(dang)(dang)“-”端(duan)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)高于(yu)(yu)(yu)“+”端(duan)時(shi)(shi)(shi)，輸(shu)(shu)(shu)出(chu)管(guan)飽和，相當(dang)(dang)于(yu)(yu)(yu)輸(shu)(shu)(shu)出(chu)端(duan)接低(di)電(dian)(dian)(dian)(dian)(dian)位。兩(liang)個(ge)輸(shu)(shu)(shu)入端(duan)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)差別大于(yu)(yu)(yu)10mV就能(neng)確保輸(shu)(shu)(shu)出(chu)能(neng)從一(yi)(yi)(yi)(yi)種狀態(tai)(tai)可(ke)靠地(di)轉換(huan)到(dao)另(ling)一(yi)(yi)(yi)(yi)種狀態(tai)(tai)， LM339的(de)輸(shu)(shu)(shu)出(chu)端(duan)相當(dang)(dang)于(yu)(yu)(yu)一(yi)(yi)(yi)(yi)只不接集電(dian)(dian)(dian)(dian)(dian)極(ji)電(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)的(de)晶體(ti)三(san)極(ji)管(guan)，在使用(yong)(yong)時(shi)(shi)(shi)輸(shu)(shu)(shu)出(chu)端(duan)到(dao)正電(dian)(dian)(dian)(dian)(dian)源一(yi)(yi)(yi)(yi)般(ban)須(xu)接一(yi)(yi)(yi)(yi)只電(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)（稱(cheng)(cheng)為(wei)上(shang)(shang)拉(la)電(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)，選(xuan)3-15K）。選(xuan)不同(tong)阻(zu)(zu)值的(de)上(shang)(shang)拉(la)電(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)會影(ying)響輸(shu)(shu)(shu)出(chu)端(duan)高電(dian)(dian)(dian)(dian)(dian)位的(de)值。因(yin)為(wei)當(dang)(dang)輸(shu)(shu)(shu)出(chu)晶體(ti)三(san)極(ji)管(guan)截(jie)止(zhi)(zhi)時(shi)(shi)(shi)，它(ta)的(de)集電(dian)(dian)(dian)(dian)(dian)極(ji)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)基(ji)本上(shang)(shang)取決于(yu)(yu)(yu)上(shang)(shang)拉(la)電(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)與負載的(de)值。

按管腳的順序把內部四(si)個(ge)比較器(qi)設為(wei)A、B 、C 、D 比較器(qi)。494和339再配合其他(ta)電路(lu)，共(gong)同完成ATX電源的穩(wen)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)(dian)源接通(tong)(tong)市電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)后(hou)，輔助電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源立即工(gong)(gong)作。一方(fang)(fang)面輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu) ＋5VSB電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源，同時(shi)(shi)向(xiang)(xiang)494的(de)(de)(de)(de)(de)(de)(de)(de){12}腳(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)(de)(de)(de)直流電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源。494從{14}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)＋5V基準電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源，鋸齒波振(zhen)(zhen)蕩(dang)器(qi)(qi)(qi)(qi)(qi)(qi)也開(kai)(kai)始(shi)起振(zhen)(zhen)工(gong)(gong)作。若(ruo)主機(ji)(ji)未(wei)開(kai)(kai)機(ji)(ji)，PS－ON信(xin)(xin)號(hao)(hao)為(wei)(wei)(wei)高電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)，經(jing)(jing)R37使(shi)(shi)(shi)(shi)339的(de)(de)(de)(de)(de)(de)(de)(de)B比(bi)(bi)(bi)較(jiao)(jiao)器(qi)(qi)(qi)(qi)(qi)(qi){6}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)亦(yi)(yi)為(wei)(wei)(wei)高電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)，因(yin)(yin)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻R37小(xiao)于(yu)R44，{6}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)高于(yu){7}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)，B比(bi)(bi)(bi)較(jiao)(jiao)器(qi)(qi)(qi)(qi)(qi)(qi)輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)端(duan)(duan)(duan)(duan){1}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)低(di)(di)(di)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)，經(jing)(jing)D36的(de)(de)(de)(de)(de)(de)(de)(de)鉗位(wei)作用，A比(bi)(bi)(bi)較(jiao)(jiao)器(qi)(qi)(qi)(qi)(qi)(qi)的(de)(de)(de)(de)(de)(de)(de)(de)反相端(duan)(duan)(duan)(duan){4}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)亦(yi)(yi)為(wei)(wei)(wei)低(di)(di)(di)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)，其電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)低(di)(di)(di)于(yu)同相端(duan)(duan)(duan)(duan){5}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)的(de)(de)(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)，輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)端(duan)(duan)(duan)(duan){2}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)呈(cheng)高電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)，經(jing)(jing)R41使(shi)(shi)(shi)(shi)494的(de)(de)(de)(de)(de)(de)(de)(de){4}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)為(wei)(wei)(wei)高電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)，故494內部的(de)(de)(de)(de)(de)(de)(de)(de)死區時(shi)(shi)間比(bi)(bi)(bi)較(jiao)(jiao)器(qi)(qi)(qi)(qi)(qi)(qi)a輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)低(di)(di)(di)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)，與(yu)(yu)(yu)門(men)1也因(yin)(yin)此輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)低(di)(di)(di)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)并(bing)進(jin)而使(shi)(shi)(shi)(shi)與(yu)(yu)(yu)門(men)2和與(yu)(yu)(yu)門(men)3輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)低(di)(di)(di)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)，封鎖了振(zhen)(zhen)蕩(dang)器(qi)(qi)(qi)(qi)(qi)(qi)的(de)(de)(de)(de)(de)(de)(de)(de)輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)，{8}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)、{11}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)無(wu)脈(mo)沖(chong)(chong)(chong)輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)，ATX電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源無(wu)±5V、±12V、＋3．3V電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)，主機(ji)(ji)處于(yu)待(dai)機(ji)(ji)狀(zhuang)態(tai)。因(yin)(yin)＋5V、＋12V電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)為(wei)(wei)(wei)零(ling)(ling)，經(jing)(jing)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻R15、R16使(shi)(shi)(shi)(shi)494的(de)(de)(de)(de)(de)(de)(de)(de){1}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)亦(yi)(yi)為(wei)(wei)(wei)零(ling)(ling)，494的(de)(de)(de)(de)(de)(de)(de)(de)c比(bi)(bi)(bi)較(jiao)(jiao)器(qi)(qi)(qi)(qi)(qi)(qi)的(de)(de)(de)(de)(de)(de)(de)(de)輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)端(duan)(duan)(duan)(duan){3}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)亦(yi)(yi)為(wei)(wei)(wei)零(ling)(ling)，經(jing)(jing)R48使(shi)(shi)(shi)(shi)339的(de)(de)(de)(de)(de)(de)(de)(de){9}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)亦(yi)(yi)為(wei)(wei)(wei)零(ling)(ling)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)，故339的(de)(de)(de)(de)(de)(de)(de)(de)C比(bi)(bi)(bi)較(jiao)(jiao)器(qi)(qi)(qi)(qi)(qi)(qi)的(de)(de)(de)(de)(de)(de)(de)(de)輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)端(duan)(duan)(duan)(duan){14}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)為(wei)(wei)(wei)零(ling)(ling)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)。另(ling)外，339的(de)(de)(de)(de)(de)(de)(de)(de){1}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)低(di)(di)(di)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)信(xin)(xin)號(hao)(hao)因(yin)(yin)D34的(de)(de)(de)(de)(de)(de)(de)(de)鉗位(wei)作用，也使(shi)(shi)(shi)(shi){14}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)為(wei)(wei)(wei)低(di)(di)(di)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)，經(jing)(jing)R50和R63使(shi)(shi)(shi)(shi){11}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)亦(yi)(yi)為(wei)(wei)(wei)低(di)(di)(di)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)。因(yin)(yin)此D比(bi)(bi)(bi)較(jiao)(jiao)器(qi)(qi)(qi)(qi)(qi)(qi)的(de)(de)(de)(de)(de)(de)(de)(de)輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)端(duan)(duan)(duan)(duan){13}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)為(wei)(wei)(wei)低(di)(di)(di)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)，也就(jiu)是(shi)PW－OK信(xin)(xin)號(hao)(hao)為(wei)(wei)(wei)低(di)(di)(di)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)，主機(ji)(ji)不會工(gong)(gong)作。開(kai)(kai)啟主機(ji)(ji)時(shi)(shi)，通(tong)(tong)過人工(gong)(gong)或遙控操作閉合(he)了與(yu)(yu)(yu)PS－ON相關的(de)(de)(de)(de)(de)(de)(de)(de)開(kai)(kai)關，PS－ON呈(cheng)低(di)(di)(di)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)，經(jing)(jing)R37使(shi)(shi)(shi)(shi)339的(de)(de)(de)(de)(de)(de)(de)(de)反相端(duan)(duan)(duan)(duan){6}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)為(wei)(wei)(wei)低(di)(di)(di)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)，B比(bi)(bi)(bi)較(jiao)(jiao)器(qi)(qi)(qi)(qi)(qi)(qi){1}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)高電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)，D35、D36反偏截(jie)止，A比(bi)(bi)(bi)較(jiao)(jiao)器(qi)(qi)(qi)(qi)(qi)(qi)的(de)(de)(de)(de)(de)(de)(de)(de)輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)則由{5}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)與(yu)(yu)(yu){4}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)的(de)(de)(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)決定。正常工(gong)(gong)作時(shi)(shi)，{5}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)低(di)(di)(di)于(yu){4}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)，{2}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)低(di)(di)(di)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)，經(jing)(jing)R41送到(dao)(dao)494的(de)(de)(de)(de)(de)(de)(de)(de){4}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)，使(shi)(shi)(shi)(shi){4}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)的(de)(de)(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)變為(wei)(wei)(wei)低(di)(di)(di)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)，鋸齒波振(zhen)(zhen)蕩(dang)信(xin)(xin)號(hao)(hao)可以從死區時(shi)(shi)間比(bi)(bi)(bi)較(jiao)(jiao)器(qi)(qi)(qi)(qi)(qi)(qi)a輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)脈(mo)沖(chong)(chong)(chong)信(xin)(xin)號(hao)(hao)，另(ling)一方(fang)(fang)面，振(zhen)(zhen)蕩(dang)信(xin)(xin)號(hao)(hao)送到(dao)(dao)了PWM比(bi)(bi)(bi)較(jiao)(jiao)器(qi)(qi)(qi)(qi)(qi)(qi)b的(de)(de)(de)(de)(de)(de)(de)(de)同相輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)(shu)入端(duan)(duan)(duan)(duan)，PWM比(bi)(bi)(bi)較(jiao)(jiao)器(qi)(qi)(qi)(qi)(qi)(qi)輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)的(de)(de)(de)(de)(de)(de)(de)(de)脈(mo)沖(chong)(chong)(chong)信(xin)(xin)號(hao)(hao)的(de)(de)(de)(de)(de)(de)(de)(de)寬度，則是(shi)由494的(de)(de)(de)(de)(de)(de)(de)(de){1}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)的(de)(de)(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)（也就(jiu)是(shi)負載的(de)(de)(de)(de)(de)(de)(de)(de)大(da)小(xiao)）與(yu)(yu)(yu){16}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)的(de)(de)(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)來決定。PWM比(bi)(bi)(bi)較(jiao)(jiao)器(qi)(qi)(qi)(qi)(qi)(qi)輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)的(de)(de)(de)(de)(de)(de)(de)(de)脈(mo)沖(chong)(chong)(chong)信(xin)(xin)號(hao)(hao)，最后(hou)經(jing)(jing)緩沖(chong)(chong)(chong)放大(da)器(qi)(qi)(qi)(qi)(qi)(qi)放大(da)后(hou)，從{8}、{11}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)脈(mo)沖(chong)(chong)(chong)信(xin)(xin)號(hao)(hao)，ATX電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源向(xiang)(xiang)主機(ji)(ji)輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)±5V、±12V、＋3.3V電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源。此過程因(yin)(yin)C35的(de)(de)(de)(de)(de)(de)(de)(de)充電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)有(you)數百毫秒的(de)(de)(de)(de)(de)(de)(de)(de)延時(shi)(shi)，但對(dui)主機(ji)(ji)開(kai)(kai)機(ji)(ji)并(bing)無(wu)影響。494的(de)(de)(de)(de)(de)(de)(de)(de){1}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)從＋5V、＋12V經(jing)(jing)取(qu)樣(yang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻R15、R16得到(dao)(dao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓，其電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)略(lve)高于(yu){2}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)，{3}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)高電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)，經(jing)(jing)R48使(shi)(shi)(shi)(shi)339的(de)(de)(de)(de)(de)(de)(de)(de){9}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)得到(dao)(dao)高電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)，其電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)高于(yu){8}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)，因(yin)(yin)而{14}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)高電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)，此電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)經(jing)(jing)R50與(yu)(yu)(yu)基準＋5V電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源經(jing)(jing)R64共同對(dui)C39充電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)，經(jing)(jing)數百毫秒后(hou)，{11}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)升到(dao)(dao)高于(yu){10}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)時(shi)(shi)，D比(bi)(bi)(bi)較(jiao)(jiao)器(qi)(qi)(qi)(qi)(qi)(qi){13}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)高電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)，此電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)經(jing)(jing)R49反饋至{11}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)，維持{11}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)處于(yu)高電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)狀(zhuang)態(tai)，故{13}腳(jiao)(jiao)(jiao)(jiao)(jiao)(jiao)輸(shu)(shu)(shu)(shu)(shu)(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)穩(wen)定的(de)(de)(de)(de)(de)(de)(de)(de)高電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping)(ping) PW－OK信(xin)(xin)號(hao)(hao)，主機(ji)(ji)檢(jian)測到(dao)(dao)此信(xin)(xin)號(hao)(hao)后(hou)即開(kai)(kai)始(shi)正常工(gong)(gong)作。

關機時，主機內開關使(shi)PS－ON呈(cheng)(cheng)(cheng)高電(dian)(dian)(dian)(dian)(dian)平(ping)，此(ci)時(shi)(shi)(shi)339的(de)(de){6}腳(jiao)(jiao)(jiao)電(dian)(dian)(dian)(dian)(dian)平(ping)高于(yu)(yu){7}腳(jiao)(jiao)(jiao)，{1}腳(jiao)(jiao)(jiao)輸出(chu)低(di)(di)電(dian)(dian)(dian)(dian)(dian)平(ping)，因(yin)(yin)二極管D34的(de)(de)鉗位作用，{14}腳(jiao)(jiao)(jiao)呈(cheng)(cheng)(cheng)低(di)(di)電(dian)(dian)(dian)(dian)(dian)平(ping)，C39對C比較器及B比較器放(fang)電(dian)(dian)(dian)(dian)(dian)，很快{11}腳(jiao)(jiao)(jiao)呈(cheng)(cheng)(cheng)低(di)(di)電(dian)(dian)(dian)(dian)(dian)平(ping)，{13}腳(jiao)(jiao)(jiao)輸出(chu)低(di)(di)電(dian)(dian)(dian)(dian)(dian)平(ping)，即PW－OK信(xin)號呈(cheng)(cheng)(cheng)低(di)(di)電(dian)(dian)(dian)(dian)(dian)平(ping)。在(zai)339的(de)(de){1}腳(jiao)(jiao)(jiao)為(wei)(wei)低(di)(di)電(dian)(dian)(dian)(dian)(dian)平(ping)時(shi)(shi)(shi)，經D36使(shi){4}臆腳(jiao)(jiao)(jiao)為(wei)(wei)低(di)(di)電(dian)(dian)(dian)(dian)(dian)平(ping)，{2}腳(jiao)(jiao)(jiao)輸出(chu)高電(dian)(dian)(dian)(dian)(dian)平(ping)，經R41傳送到494的(de)(de){4}腳(jiao)(jiao)(jiao)，但因(yin)(yin)C35電(dian)(dian)(dian)(dian)(dian)位不(bu)能突變，經數百毫秒的(de)(de)放(fang)電(dian)(dian)(dian)(dian)(dian)后(hou)方使(shi)494的(de)(de){4}腳(jiao)(jiao)(jiao)轉為(wei)(wei)高電(dian)(dian)(dian)(dian)(dian)平(ping)，從而封鎖正負脈沖(chong)的(de)(de)輸出(chu) ，主機(ji)進入待機(ji)狀(zhuang)態。上述(shu)的(de)(de)過程中，關機(ji)時(shi)(shi)(shi)C39和C35都要放(fang)電(dian)(dian)(dian)(dian)(dian)，但因(yin)(yin)放(fang)電(dian)(dian)(dian)(dian)(dian)時(shi)(shi)(shi)間常數不(bu)同，C39放(fang)電(dian)(dian)(dian)(dian)(dian)較快，故PW－OK信(xin)號先于(yu)(yu)各(ge)電(dian)(dian)(dian)(dian)(dian)源變成低(di)(di)電(dian)(dian)(dian)(dian)(dian)平(ping)，滿足了主機(ji)關機(ji)的(de)(de)需要。此(ci)外(wai)，關機(ji)時(shi)(shi)(shi)因(yin)(yin)各(ge)路輸出(chu)電(dian)(dian)(dian)(dian)(dian)源的(de)(de)電(dian)(dian)(dian)(dian)(dian)解電(dian)(dian)(dian)(dian)(dian)容(rong)放(fang)電(dian)(dian)(dian)(dian)(dian)需要時(shi)(shi)(shi)間，也使(shi)PW－OK信(xin)號先于(yu)(yu)各(ge)電(dian)(dian)(dian)(dian)(dian)源回到低(di)(di)電(dian)(dian)(dian)(dian)(dian)平(ping)。

二、 穩壓

494的(de)(de)(de){2}腳(jiao)經R47與(yu)基準(zhun)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)＋5V相連(lian)，維持較(jiao)好的(de)(de)(de)穩定(ding)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)，而{1}腳(jiao)則(ze)(ze)與(yu)取樣電(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)R15、R16與(yu)＋5V、＋12V相連(lian)接，正(zheng)常的(de)(de)(de)情況下(xia)，{1}腳(jiao)電(dian)(dian)(dian)(dian)(dian)(dian)平(ping)與(yu){2}腳(jiao)電(dian)(dian)(dian)(dian)(dian)(dian)平(ping)相等或(huo)略高。當輸(shu)(shu)出(chu)(chu)(chu)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)升高時(shi)（無論＋5V或(huo)＋12V），{1}腳(jiao)電(dian)(dian)(dian)(dian)(dian)(dian)平(ping)高于{2}腳(jiao)電(dian)(dian)(dian)(dian)(dian)(dian)平(ping)，c比(bi)(bi)較(jiao)器輸(shu)(shu)出(chu)(chu)(chu)誤(wu)差電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)與(yu)鋸齒(chi)波振(zhen)(zhen)蕩(dang)脈沖在PWM比(bi)(bi)較(jiao)器b進行比(bi)(bi)較(jiao)使(shi)輸(shu)(shu)出(chu)(chu)(chu)脈沖寬度變窄(zhai)，輸(shu)(shu)出(chu)(chu)(chu)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)回(hui)落到標準(zhun)值，反之則(ze)(ze)促使(shi)振(zhen)(zhen)蕩(dang)脈沖寬度增加，輸(shu)(shu)出(chu)(chu)(chu)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)回(hui)升。由于494內(nei)的(de)(de)(de)放大(da)器增益很(hen)高，故穩壓(ya)(ya)精度很(hen)好。從穩壓(ya)(ya)的(de)(de)(de)原理，我(wo)們可以(yi)得到ATX電(dian)(dian)(dian)(dian)(dian)(dian)源輸(shu)(shu)出(chu)(chu)(chu)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)偏(pian)(pian)高或(huo)偏(pian)(pian)低的(de)(de)(de)維修(xiu)方法(fa)。如(ru)果輸(shu)(shu)出(chu)(chu)(chu)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)偏(pian)(pian)低，可在494的(de)(de)(de){1}腳(jiao)對(dui)地(di)并(bing)聯(lian)電(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)，或(huo)是(shi)把R47的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)增大(da)。要是(shi)電(dian)(dian)(dian)(dian)(dian)(dian)源的(de)(de)(de)輸(shu)(shu)出(chu)(chu)(chu)偏(pian)(pian)高，則(ze)(ze)可在{2}腳(jiao)對(dui)地(di)并(bing)聯(lian)電(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)，也可以(yi)用增大(da)R33或(huo)取下(xia)R69、R35來(lai)降低輸(shu)(shu)出(chu)(chu)(chu)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)。

三、 過流保護

過(guo)(guo)流保護(hu)(hu)的(de)(de)(de)原理(li)是基(ji)于負載(zai)愈(yu)大，Q3、Q4集電(dian)(dian)(dian)(dian)(dian)(dian)極(ji)的(de)(de)(de)脈(mo)(mo)(mo)沖(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)壓也(ye)愈(yu)高(gao)，也(ye)即(ji)是R13（1．5kΩ）上的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)壓也(ye)愈(yu)高(gao)，從(cong)這里采樣(yang)經D14整流和(he)C36濾波，再(zai)經R54、R55并(bing)聯(lian)電(dian)(dian)(dian)(dian)(dian)(dian)阻與R51、R56、R58等組成的(de)(de)(de)分壓電(dian)(dian)(dian)(dian)(dian)(dian)路(lu)送(song)(song)到(dao)494的(de)(de)(de){16}腳(jiao)(jiao)(jiao)(jiao)(jiao)。隨(sui)著負載(zai)的(de)(de)(de)加重(zhong)(zhong)，{16}腳(jiao)(jiao)(jiao)(jiao)(jiao)的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)也(ye)隨(sui)之上升，當超(chao)過(guo)(guo){15}腳(jiao)(jiao)(jiao)(jiao)(jiao)的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)時(shi)，誤差放(fang)大器輸(shu)(shu)出(chu)(chu)的(de)(de)(de)誤差電(dian)(dian)(dian)(dian)(dian)(dian)壓促使(shi)調制(zhi)脈(mo)(mo)(mo)沖(chong)(chong)的(de)(de)(de)寬度變(bian)窄(zhai)從(cong)而(er)使(shi)負載(zai)電(dian)(dian)(dian)(dian)(dian)(dian)流減小(xiao)。另外，從(cong)R56、R58并(bing)聯(lian)電(dian)(dian)(dian)(dian)(dian)(dian)阻獲(huo)得的(de)(de)(de)分壓再(zai)經R52送(song)(song)到(dao)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)(dian)(dian)平(ping)(ping)(ping)超(chao)過(guo)(guo){4}腳(jiao)(jiao)(jiao)(jiao)(jiao)時(shi)，{2}腳(jiao)(jiao)(jiao)(jiao)(jiao)即(ji)輸(shu)(shu)出(chu)(chu)高(gao)電(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)送(song)(song)到(dao)494的(de)(de)(de){4}腳(jiao)(jiao)(jiao)(jiao)(jiao)，494停止(zhi)輸(shu)(shu)出(chu)(chu)脈(mo)(mo)(mo)沖(chong)(chong)信(xin)號，終(zhong)止(zhi)±5V、±12V、＋3．3V電(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)的(de)(de)(de)輸(shu)(shu)出(chu)(chu)，達到(dao)過(guo)(guo)流及短路(lu)保護(hu)(hu)的(de)(de)(de)目(mu)的(de)(de)(de)。需要說明的(de)(de)(de)是：494的(de)(de)(de){16}腳(jiao)(jiao)(jiao)(jiao)(jiao)電(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)的(de)(de)(de)高(gao)低只(zhi)能(neng)改變(bian)輸(shu)(shu)出(chu)(chu)脈(mo)(mo)(mo)沖(chong)(chong)的(de)(de)(de)寬度，但不影響494的(de)(de)(de){4}腳(jiao)(jiao)(jiao)(jiao)(jiao)電(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)狀(zhuang)態(tai)(tai)，而(er)339的(de)(de)(de){5}腳(jiao)(jiao)(jiao)(jiao)(jiao)電(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)一旦超(chao)過(guo)(guo){4}腳(jiao)(jiao)(jiao)(jiao)(jiao)的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)，339的(de)(de)(de){2}腳(jiao)(jiao)(jiao)(jiao)(jiao)就送(song)(song)出(chu)(chu)高(gao)電(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)去(qu)封鎖449的(de)(de)(de)脈(mo)(mo)(mo)沖(chong)(chong)輸(shu)(shu)出(chu)(chu)，終(zhong)止(zhi)±5V、±12V、＋3．3V電(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)的(de)(de)(de)輸(shu)(shu)出(chu)(chu)，同時(shi){2}腳(jiao)(jiao)(jiao)(jiao)(jiao)的(de)(de)(de)高(gao)電(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)經R59和(he)二極(ji)管D39反饋到(dao){5}腳(jiao)(jiao)(jiao)(jiao)(jiao)，維持{5}腳(jiao)(jiao)(jiao)(jiao)(jiao)處于高(gao)電(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)狀(zhuang)態(tai)(tai)，此(ci)時(shi)若過(guo)(guo)載(zai)或短路(lu)狀(zhuang)態(tai)(tai)消失，494的(de)(de)(de){4}腳(jiao)(jiao)(jiao)(jiao)(jiao)仍(reng)維持高(gao)電(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)(ping)，±5V與±12V、＋3．3V電(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)仍(reng)不能(neng)輸(shu)(shu)出(chu)(chu)，只(zhi)有切(qie)斷(duan)交流市(shi)電(dian)(dian)(dian)(dian)(dian)(dian)的(de)(de)(de)輸(shu)(shu)入(ru)，再(zai)重(zhong)(zhong)新接通交流電(dian)(dian)(dian)(dian)(dian)(dian)，方可(ke)再(zai)次開機(ji)。

四、過壓保護

過(guo)電(dian)(dian)(dian)壓(ya)保(bao)護(hu)由R17和穩(wen)壓(ya)管Z02并聯電(dian)(dian)(dian)路從＋5V采樣，經D37送(song)到339的(de)(de){5}腳(jiao)。若＋5V電(dian)(dian)(dian)源(yuan)(yuan)由于某種原(yuan)因升高，339的(de)(de){5}腳(jiao)電(dian)(dian)(dian)平也會隨之(zhi)升高，當超(chao)過(guo){4}腳(jiao)電(dian)(dian)(dian)平時(shi)(shi)，{2}腳(jiao)即送(song)出高電(dian)(dian)(dian)平去494的(de)(de){4}腳(jiao)，封鎖(suo)±5V、±12V、＋3．3V電(dian)(dian)(dian)源(yuan)(yuan)的(de)(de)輸出，達(da)到過(guo)電(dian)(dian)(dian)壓(ya)保(bao)護(hu)的(de)(de)目的(de)(de)。正常工作時(shi)(shi)，R17上(shang)(shang)的(de)(de)壓(ya)降(jiang)不大(da)，Z02截止送(song)到{5}腳(jiao)的(de)(de)電(dian)(dian)(dian)壓(ya)較低，若＋5V電(dian)(dian)(dian)源(yuan)(yuan)的(de)(de)電(dian)(dian)(dian)壓(ya)上(shang)(shang)升，使(shi)R17上(shang)(shang)的(de)(de)壓(ya)降(jiang)超(chao)過(guo)Z02的(de)(de)穩(wen)壓(ya)值，Z02導(dao)通，＋5V電(dian)(dian)(dian)源(yuan)(yuan)上(shang)(shang)升后(hou)的(de)(de)電(dian)(dian)(dian)壓(ya)值全部加到339的(de)(de){5}腳(jiao)上(shang)(shang)，促(cu)使(shi)其快速封鎖(suo)494脈沖的(de)(de)輸出，以保(bao)護(hu)電(dian)(dian)(dian)源(yuan)(yuan)。

五、欠壓保護

欠(qian)(qian)(qian)壓(ya)(ya)保(bao)(bao)(bao)護(hu)從－5V的(de)(de)(de)D32及－12V處的(de)(de)(de)R14取樣，經(jing)R34和D37送到(dao)(dao)339的(de)(de)(de){5}腳。若(ruo)因某種原因使輸出(chu)電(dian)(dian)壓(ya)(ya)過(guo)低時，－12V及 －5V電(dian)(dian)壓(ya)(ya)的(de)(de)(de)負(fu)值(zhi)也(ye)會隨之(zhi)減(jian)小，也(ye)就是電(dian)(dian)壓(ya)(ya)值(zhi)上(shang)(shang)升，經(jing)R34及D37送往339的(de)(de)(de){5}腳使電(dian)(dian)平上(shang)(shang)升，339的(de)(de)(de){2}腳送出(chu)高電(dian)(dian)平到(dao)(dao)494的(de)(de)(de){4}腳，從而(er)封鎖 449脈沖的(de)(de)(de)輸出(chu)，實現欠(qian)(qian)(qian)壓(ya)(ya)保(bao)(bao)(bao)護(hu)。二極管(guan)D32在導通時，其電(dian)(dian)壓(ya)(ya)降與通過(guo)的(de)(de)(de)電(dian)(dian)流(liu)基本(ben)無關，保(bao)(bao)(bao)持(chi)在0．6V～0．7V，于是－5V電(dian)(dian)壓(ya)(ya)的(de)(de)(de)減(jian)少量(liang)會全部傳送到(dao)(dao)D32的(de)(de)(de)負(fu)端(duan)，提高了欠(qian)(qian)(qian)壓(ya)(ya)保(bao)(bao)(bao)護(hu)的(de)(de)(de)靈敏度(du)。