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開關電源故障檢查 開關電源維修方法

本文章由注冊用戶 沉靜時光 上傳提供 評論 發布 反饋 0
摘要:您知道開關電源故障如何維修嗎?開關電源的維修可分為斷電情況下,“看、聞、問、量”、加電檢測兩步進行。看:打開電源的外殼,檢查保險絲是否熔斷,再觀察電源的內部情況。聞:聞一下電源內部是否有糊味,檢查是否有燒焦的元器件。下面小編就詳細為您介紹開關電源維修技巧。

開關電源簡介

開關電源是利用現(xian)代(dai)電(dian)(dian)(dian)(dian)力電(dian)(dian)(dian)(dian)子(zi)技術(shu),控制(zhi)開(kai)(kai)關晶體管開(kai)(kai)通(tong)和關斷(duan)的(de)時間比率,維持(chi)穩定輸出(chu)電(dian)(dian)(dian)(dian)壓的(de)一(yi)種(zhong)電(dian)(dian)(dian)(dian)源(yuan)(yuan)。廣泛(fan)運用在(zai)工(gong)業、軍事、科研、通(tong)訊、醫(yi)療及(ji)多種(zhong)家用電(dian)(dian)(dian)(dian)器中。開(kai)(kai)關電(dian)(dian)(dian)(dian)源(yuan)(yuan)的(de)發(fa)展與應用在(zai)節約能源(yuan)(yuan)、節約資源(yuan)(yuan)及(ji)保護(hu)環境方面都具有重要的(de)意(yi)義(yi)。下面我(wo)們(men)就來(lai)看看開(kai)(kai)關電(dian)(dian)(dian)(dian)源(yuan)(yuan)電(dian)(dian)(dian)(dian)路(lu)圖與維修(xiu)技巧。

開(kai)關(guan)電(dian)源的(de)主要電(dian)路(lu)是由輸入電(dian)磁干擾濾(lv)波(bo)器(EMI)、整流濾(lv)波(bo)電(dian)路(lu)、功率變換電(dian)路(lu)、PWM控制器電(dian)路(lu)、輸出(chu)(chu)(chu)整流濾(lv)波(bo)電(dian)路(lu)組(zu)成。輔助電(dian)路(lu)有輸入過(guo)欠壓(ya)保護(hu)電(dian)路(lu)、輸出(chu)(chu)(chu)過(guo)欠壓(ya)保護(hu)電(dian)路(lu)、輸出(chu)(chu)(chu)過(guo)流保護(hu)電(dian)路(lu)、輸出(chu)(chu)(chu)短(duan)路(lu)保護(hu)電(dian)路(lu)等。

開關電源的維修步驟

加電檢測

該圖片由注冊用戶"沉靜時光"提供,版權聲明反饋

通電后觀察電源是否有(you)燒保險及(ji)個別元件冒煙(yan)等現象,若有(you)要及(ji)時(shi)切斷供電進行(xing)檢修。

測量高(gao)壓濾(lv)波電容兩端有無300伏輸出,若無應重點查(cha)整流二(er)極管、濾(lv)波電容等。

測量高(gao)頻(pin)變壓器(qi)次級線圈有無輸出,若無應重點查開關(guan)管是否(fou)損壞,是否(fou)起振,保護電路(lu)是否(fou)動作等,若有則應重點檢查各(ge)輸出側的(de)整流二極管、濾波電容、三通(tong)穩壓管等。

如果(guo)電(dian)(dian)源啟動一下就停(ting)止,則該(gai)電(dian)(dian)源處于保(bao)(bao)護(hu)狀態下,可直(zhi)接測量PWM芯片保(bao)(bao)護(hu)輸入腳的電(dian)(dian)壓(ya),如果(guo)電(dian)(dian)壓(ya)超出(chu)規定值,則說明電(dian)(dian)源處于保(bao)(bao)護(hu)狀態下,應重點(dian)檢查產生保(bao)(bao)護(hu)的原(yuan)因。

總(zong)之,開關電(dian)源(yuan)電(dian)路有易有難,功率(lv)有大有小,輸出電(dian)壓多種(zhong)多樣(yang)。只要按(an)照上述維修技巧,多動手進行開關電(dian)源(yuan)的維修,就能(neng)迅速地排除開關電(dian)源(yuan)故障,達到事(shi)半功倍的效果。

斷電后看聞問量

看(kan):打(da)開(kai)電源(yuan)的外殼,檢查保險絲(si)是(shi)否熔(rong)斷,再觀(guan)察電源(yuan)的內部情況,如果發現電源(yuan)的PCB板上有燒焦處或元(yuan)件破裂,則應(ying)重點檢查此處元(yuan)件及相關(guan)電路元(yuan)件。

聞:聞一下電源內部是否有糊味,檢查是否有燒焦的(de)元(yuan)器件。

問:問一(yi)下電源損壞的經過,是(shi)否對(dui)電源進行違(wei)規操作(zuo)。

量:沒通(tong)電(dian)前,用萬(wan)用表量一下高壓電(dian)容(rong)兩(liang)端(duan)的(de)電(dian)壓先。如果是開(kai)關電(dian)源(yuan)不起(qi)振或開(kai)關管(guan)開(kai)路(lu)引起(qi)的(de)故障(zhang),則大多數情況下,高壓濾波電(dian)容(rong)兩(liang)端(duan)的(de)電(dian)壓未泄(xie)放(fang)(fang)悼,用萬(wan)用表測(ce)量AC電(dian)源(yuan)線兩(liang)端(duan)的(de)正反向電(dian)阻及(ji)電(dian)容(rong)器(qi)充電(dian)情況,電(dian)阻值不應(ying)過低,否則電(dian)源(yuan)內部可能存在短路(lu)。電(dian)容(rong)器(qi)應(ying)能充放(fang)(fang)電(dian)。脫開(kai)負載,分別測(ce)量各組(zu)輸(shu)出端(duan)的(de)對地電(dian)阻,正常時(shi),表針應(ying)有電(dian)容(rong)器(qi)充放(fang)(fang)電(dian)擺動,最后指示的(de)應(ying)為該路(lu)的(de)泄(xie)放(fang)(fang)電(dian)阻的(de)阻值。

開關電源常見故障檢修

1、保險絲熔斷

一(yi)般情況下(xia),保(bao)險(xian)絲熔(rong)斷(duan)說(shuo)明開(kai)(kai)關電(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)的內部電(dian)(dian)(dian)(dian)(dian)(dian)路(lu)存在(zai)短路(lu)或(huo)過(guo)流的故障(zhang)。由于開(kai)(kai)關電(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)工(gong)作在(zai)高電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya),大電(dian)(dian)(dian)(dian)(dian)(dian)流的狀態下(xia),直流濾(lv)波(bo)和變換(huan)振蕩(dang)電(dian)(dian)(dian)(dian)(dian)(dian)路(lu)在(zai)高壓(ya)狀態工(gong)作時間太長,電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)變化相對大。電(dian)(dian)(dian)(dian)(dian)(dian)網電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)的波(bo)動,浪涌都會引(yin)起電(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)內電(dian)(dian)(dian)(dian)(dian)(dian)流瞬間增(zeng)大而使保(bao)險(xian)絲熔(rong)斷(duan)。重點應檢(jian)查電(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)輸入(ru)端的整流二極(ji)管,高壓(ya)濾(lv)波(bo)電(dian)(dian)(dian)(dian)(dian)(dian)解(jie)電(dian)(dian)(dian)(dian)(dian)(dian)容,開(kai)(kai)關功(gong)率管,UC3842本身及外圍元(yuan)器件等。檢(jian)查一(yi)下(xia)這些元(yuan)器件有無擊穿,開(kai)(kai)路(lu),損壞,燒焦(jiao),炸裂等現象。

維(wei)修方法:首先仔細(xi)查(cha)看電(dian)路板上(shang)(shang)面的(de)(de)各個元(yuan)件(jian),看是(shi)(shi)(shi)(shi)否(fou)在這些(xie)元(yuan)件(jian)的(de)(de)外(wai)表(biao)有(you)(you)(you)沒有(you)(you)(you)被燒(shao)(shao)糊,有(you)(you)(you)沒有(you)(you)(you)電(dian)解液溢出,聞一(yi)(yi)聞有(you)(you)(you)沒有(you)(you)(you)異味。經(jing)看,聞之后(hou)(hou),再(zai)用萬(wan)用表(biao)進行檢查(cha)。首先測(ce)量(liang)(liang)一(yi)(yi)下(xia)電(dian)源輸入端(duan)的(de)(de)電(dian)阻值,若小(xiao)于200K,則(ze)說明(ming)后(hou)(hou)端(duan)有(you)(you)(you)局部(bu)短路現象(xiang),然(ran)后(hou)(hou)分(fen)別測(ce)量(liang)(liang)四只(zhi)整流(liu)二極管正(zheng),反(fan)向電(dian)阻和兩個限流(liu)電(dian)阻的(de)(de)阻值,看其(qi)有(you)(you)(you)無短路或燒(shao)(shao)壞;然(ran)后(hou)(hou)再(zai)測(ce)量(liang)(liang)一(yi)(yi)下(xia)電(dian)源濾波電(dian)容(rong)(rong)是(shi)(shi)(shi)(shi)否(fou)能(neng)進行正(zheng)常充放電(dian),再(zai)就測(ce)量(liang)(liang)一(yi)(yi)下(xia)開關功率(lv)(lv)管是(shi)(shi)(shi)(shi)否(fou)擊(ji)穿損(sun)壞,以及UC3842本身,及周圍元(yuan)件(jian)是(shi)(shi)(shi)(shi)否(fou)擊(ji)穿,燒(shao)(shao)壞等。需要說明(ming)的(de)(de)一(yi)(yi)點(dian)是(shi)(shi)(shi)(shi):因(yin)是(shi)(shi)(shi)(shi)在路測(ce)量(liang)(liang),有(you)(you)(you)可能(neng)會使測(ce)量(liang)(liang)結果(guo)有(you)(you)(you)誤,造(zao)成誤判。因(yin)此必要時可把元(yuan)器(qi)件(jian)焊下(xia)來再(zai)進行測(ce)量(liang)(liang)。如果(guo)仍然(ran)沒有(you)(you)(you)上(shang)(shang)述情況則(ze)測(ce)量(liang)(liang)一(yi)(yi)下(xia)輸入電(dian)源線及輸出電(dian)源線是(shi)(shi)(shi)(shi)否(fou)內(nei)部(bu)短路。一(yi)(yi)般(ban)情況下(xia),熔(rong)斷(duan)器(qi)熔(rong)斷(duan)故障,整流(liu)二極管,電(dian)源濾波電(dian)容(rong)(rong),開關功率(lv)(lv)管,UC3842是(shi)(shi)(shi)(shi)易損(sun)件(jian),損(sun)壞的(de)(de)概率(lv)(lv)可達95%以上(shang)(shang),一(yi)(yi)般(ban)著重檢查(cha)一(yi)(yi)下(xia)這些(xie)元(yuan)器(qi)件(jian),就可很(hen)容(rong)(rong)易排(pai)除此類(lei)故障。

2、無直流電壓輸出或電壓輸出不穩定

如果保(bao)險絲是完好的,在有負(fu)載的情況(kuang)下,各(ge)級直流(liu)(liu)電(dian)(dian)(dian)壓無輸出。這種情況(kuang)主要是以下原(yuan)因(yin)造(zao)成的:電(dian)(dian)(dian)源(yuan)中(zhong)(zhong)出現開路(lu),短路(lu)現象,過(guo)壓,過(guo)流(liu)(liu)保(bao)護電(dian)(dian)(dian)路(lu)出現故(gu)障,振蕩電(dian)(dian)(dian)路(lu)沒有工作,電(dian)(dian)(dian)源(yuan)負(fu)載過(guo)重,高頻整(zheng)流(liu)(liu)濾(lv)波電(dian)(dian)(dian)路(lu)中(zhong)(zhong)整(zheng)流(liu)(liu)二極管被擊穿,濾(lv)波電(dian)(dian)(dian)容漏電(dian)(dian)(dian)等。

維(wei)修(xiu)方法:首(shou)先(xian),用萬用表(biao)測(ce)量(liang)一下高頻變(bian)壓(ya)(ya)器次級的(de)(de)(de)各(ge)(ge)個(ge)元(yuan)(yuan)器件是(shi)否有損(sun)(sun)壞(huai)。在排除(chu)了高頻整(zheng)流(liu)二(er)極(ji)管擊穿、負(fu)載(zai)短路(lu)(lu)(lu)的(de)(de)(de)情況后(hou),然后(hou)在測(ce)量(liang)各(ge)(ge)輸(shu)出端的(de)(de)(de)直流(liu)電(dian)(dian)壓(ya)(ya),如果這(zhe)(zhe)時輸(shu)出仍為零,則可以肯(ken)定是(shi)電(dian)(dian)源(yuan)(yuan)的(de)(de)(de)控制電(dian)(dian)路(lu)(lu)(lu)出了故障(zhang)。控制電(dian)(dian)路(lu)(lu)(lu)的(de)(de)(de)兩部分是(shi)集成(cheng)開關(guan)電(dian)(dian)源(yuan)(yuan)控制器和過(guo)壓(ya)(ya)保護電(dian)(dian)路(lu)(lu)(lu)。最(zui)后(hou)用萬用表(biao)靜態測(ce)量(liang)高頻濾(lv)波電(dian)(dian)路(lu)(lu)(lu)中整(zheng)流(liu)二(er)極(ji)管及低壓(ya)(ya)濾(lv)波電(dian)(dian)容是(shi)否損(sun)(sun)壞(huai)。如果確實相關(guan)的(de)(de)(de)元(yuan)(yuan)件損(sun)(sun)壞(huai),在更換好新(xin)的(de)(de)(de)完好的(de)(de)(de)元(yuan)(yuan)件后(hou),開機測(ce)試,一般(ban)故障(zhang)即可排除(chu)。需要說明(ming)的(de)(de)(de)是(shi):電(dian)(dian)源(yuan)(yuan)輸(shu)出線斷線或開焊,虛焊也(ye)會造成(cheng)這(zhe)(zhe)種故障(zhang)。在維(wei)修(xiu)時應注意這(zhe)(zhe)一點。

3、電源負載能力差

電(dian)(dian)源負(fu)載能力差是(shi)一(yi)個常見的(de)故障,一(yi)般都是(shi)出現在老式或是(shi)工作時間長(chang)的(de)電(dian)(dian)源中,主要原因是(shi)各元(yuan)器件老化,開(kai)關管的(de)工作不穩定(ding),沒有及時進(jin)行散(san)熱等。此外還有穩壓(ya)二(er)極管發熱漏電(dian)(dian),整(zheng)流二(er)極管損壞(huai)等。

維修(xiu)方法:用萬用表著重檢查一下穩(wen)壓(ya)二極管,高壓(ya)濾(lv)波(bo)電容,限流電阻有無變(bian)質等再(zai)仔細檢查一下電路板上的所有焊(han)(han)點是(shi)否開(kai)焊(han)(han),虛接等。把開(kai)焊(han)(han)的焊(han)(han)點重新焊(han)(han)牢(lao),更換變(bian)質的元(yuan)器件,一般故障即可排除。

4、無直流電壓輸出,但保險絲完好

這種現象說明開關(guan)電源未工作,或者工作后進入了保護(hu)狀態。

維修方法:首先應判(pan)斷(duan)一下開(kai)關(guan)電(dian)(dian)(dian)(dian)源(yuan)(yuan)的(de)主(zhu)控芯(xin)片(pian)UC3842是否處在工作(zuo)狀態或已經損(sun)壞(huai)。判(pan)斷(duan)方法是這(zhe)樣的(de):加電(dian)(dian)(dian)(dian)測UC3842的(de)第(di)(di)7腳(jiao)(jiao)對地電(dian)(dian)(dian)(dian)壓(ya)(ya),若(ruo)(ruo)測第(di)(di)8腳(jiao)(jiao)有(you)+5V電(dian)(dian)(dian)(dian)壓(ya)(ya),1,2,4,6腳(jiao)(jiao)也有(you)不同(tong)的(de)電(dian)(dian)(dian)(dian)壓(ya)(ya),則說明電(dian)(dian)(dian)(dian)路已起振(zhen),UC3842基本(ben)(ben)正常(chang);若(ruo)(ruo)7腳(jiao)(jiao)電(dian)(dian)(dian)(dian)壓(ya)(ya)低,其余管腳(jiao)(jiao)無(wu)電(dian)(dian)(dian)(dian)壓(ya)(ya)或不波動,則UC3842已損(sun)壞(huai)。UC3842芯(xin)片(pian)損(sun)壞(huai)最(zui)常(chang)見(jian)的(de)是6,7腳(jiao)(jiao)對地擊(ji)(ji)穿(chuan),5,7腳(jiao)(jiao)對地擊(ji)(ji)穿(chuan)和1,7腳(jiao)(jiao)對地擊(ji)(ji)穿(chuan)。如果(guo)這(zhe)幾只腳(jiao)(jiao)都為(wei)擊(ji)(ji)穿(chuan),而開(kai)關(guan)電(dian)(dian)(dian)(dian)源(yuan)(yuan)還(huan)是不能正常(chang)啟動,則UC3842必(bi)壞(huai),應直接(jie)更換(huan)。若(ruo)(ruo)判(pan)斷(duan)芯(xin)片(pian)未(wei)壞(huai),則就著重檢查(cha)開(kai)關(guan)功率(lv)管的(de)柵(zha)極(G極)的(de)限流電(dian)(dian)(dian)(dian)阻是否開(kai)焊,虛接(jie),變(bian)值,變(bian)質以及開(kai)關(guan)功率(lv)管本(ben)(ben)身是否性能不良(liang)。除(chu)此(ci)之外,電(dian)(dian)(dian)(dian)源(yuan)(yuan)輸(shu)出線也有(you)可(ke)能斷(duan)線或接(jie)觸不良(liang)也會(hui)造(zao)成這(zhe)種(zhong)故障。因此(ci)在維修時也應注意檢查(cha)一下。

5、有直流電壓輸出,但輸出電壓過高

這種故(gu)(gu)障往往來自于穩壓(ya)取樣和(he)穩壓(ya)控(kong)制電路(lu)出現故(gu)(gu)障所致。在開(kai)關電源中,直流輸出、取樣電阻(zu)、誤差取樣放大器(如LM324,LM358等(deng))、光耦(ou)合器(PC817)、電源控(kong)制芯片(pian)(UC3842)等(deng)電路(lu)共同(tong)構(gou)成(cheng)了一(yi)個閉合的控(kong)制環(huan)路(lu),任何一(yi)處出問題(ti)都會導致輸出電壓(ya)升高(gao)。

維修(xiu)方法:由于(yu)開關電(dian)(dian)(dian)源(yuan)中有過(guo)壓(ya)保(bao)護(hu)電(dian)(dian)(dian)路(lu),輸出(chu)電(dian)(dian)(dian)壓(ya)過(guo)高首先會使過(guo)壓(ya)保(bao)護(hu)電(dian)(dian)(dian)路(lu)動作。因此對于(yu)這種故(gu)障的(de)(de)維修(xiu),我(wo)們可(ke)以通(tong)過(guo)斷(duan)開過(guo)壓(ya)保(bao)護(hu)電(dian)(dian)(dian)路(lu),使過(guo)壓(ya)保(bao)護(hu)電(dian)(dian)(dian)路(lu)不起作用,在這時,測量(liang)開機瞬間(jian)的(de)(de)電(dian)(dian)(dian)源(yuan)主電(dian)(dian)(dian)壓(ya)。如果測量(liang)值(zhi)(zhi)(zhi)比(bi)正常值(zhi)(zhi)(zhi)高出(chu)IV以上,說明輸出(chu)電(dian)(dian)(dian)壓(ya)過(guo)高。我(wo)們應(ying)著重檢查取(qu)樣電(dian)(dian)(dian)阻是(shi)否變值(zhi)(zhi)(zhi)或(huo)(huo)損壞(huai)(huai),精(jing)密穩(wen)壓(ya)放(fang)大(da)器(qi)(qi)(TL431)或(huo)(huo)光(guang)耦合器(qi)(qi)(PC817)性能不良,變質(zhi)或(huo)(huo)損壞(huai)(huai);其中精(jing)密穩(wen)壓(ya)放(fang)大(da)器(qi)(qi)(TL431)極(ji)(ji)易損壞(huai)(huai),我(wo)們可(ke)用下述(shu)方法對精(jing)密穩(wen)壓(ya)放(fang)大(da)器(qi)(qi)(TL431)作出(chu)好壞(huai)(huai)的(de)(de)判別:將(jiang)TL431的(de)(de)參(can)考端(Ref)與它的(de)(de)陰極(ji)(ji)(Cathode)相連(lian),串10k的(de)(de)電(dian)(dian)(dian)阻,接(jie)入5V電(dian)(dian)(dian)壓(ya),若(ruo)陽極(ji)(ji)(Anode)與陰極(ji)(ji)之間(jian)為2、5V,并且等(deng)待片刻還仍然為2、5V,則為好管,否則為壞(huai)(huai)管。

6、有直流電壓輸出,但輸出直流電壓過低

對于這種故障現象,根據(ju)維修經驗可知,除穩壓控制電(dian)(dian)路(lu)會引(yin)起(qi)輸(shu)(shu)出電(dian)(dian)壓過低外,還有(you)一(yi)些(xie)原因會引(yin)起(qi)輸(shu)(shu)出電(dian)(dian)壓過低,主要有(you)以下(xia)幾點:


① 開(kai)(kai)關電(dian)源負載(zai)有短路(lu)(lu)故障。此時,應斷(duan)開(kai)(kai)開(kai)(kai)關電(dian)源電(dian)路(lu)(lu)的所有負載(zai),以區分是開(kai)(kai)關電(dian)源電(dian)路(lu)(lu)還是負載(zai)電(dian)路(lu)(lu)有故障。若(ruo)斷(duan)開(kai)(kai)負載(zai)電(dian)路(lu)(lu)電(dian)壓輸出正(zheng)常,說明是負載(zai)過重(zhong);若(ruo)仍不正(zheng)常,說明開(kai)(kai)關電(dian)源電(dian)路(lu)(lu)有故障。

② 輸出電(dian)壓端整流二極管(guan)、濾波電(dian)容失效(xiao)等,可以通過代換法進行判(pan)斷。

③ 開(kai)關功(gong)率管的性能(neng)下降(jiang),必然導致(zhi)開(kai)關管不能(neng)正常導通,使電源(yuan)的內阻(zu)增加,帶負載能(neng)力下降(jiang)。

④ 開(kai)關功率管的源極(S極),通(tong)常(chang)接(jie)一(yi)個(ge)阻(zu)值很小,但(dan)功率很大的電阻(zu),作(zuo)為過流保護檢測電阻(zu),此電阻(zu)的阻(zu)值一(yi)般在0.2到(dao)0.8之間。此電阻(zu)如變值或開(kai)焊,接(jie)觸不良也會(hui)造成輸出電壓過低的故障。

高(gao)頻變壓器不良,不但造(zao)成(cheng)(cheng)輸出電(dian)壓下降,還會造(zao)成(cheng)(cheng)開關功率管(guan)激勵不足從(cong)而屢損開關管(guan)。

⑤ 高壓直(zhi)流濾波電(dian)容(rong)不良,造成電(dian)源帶負(fu)(fu)載能力差,一接負(fu)(fu)載輸出電(dian)壓便下降(jiang)。

⑥ 電源輸(shu)出(chu)線接觸(chu)不良,有(you)一定的接觸(chu)電阻,造成(cheng)輸(shu)出(chu)電壓過(guo)低。

⑦ 電(dian)(dian)(dian)網電(dian)(dian)(dian)壓(ya)(ya)是否過低。雖然開關電(dian)(dian)(dian)源(yuan)在低壓(ya)(ya)下仍(reng)然可以輸出額定的(de)電(dian)(dian)(dian)壓(ya)(ya)值,但當電(dian)(dian)(dian)網電(dian)(dian)(dian)壓(ya)(ya)低于開關電(dian)(dian)(dian)源(yuan)的(de)最低電(dian)(dian)(dian)壓(ya)(ya)限定值時,也(ye)會使輸出電(dian)(dian)(dian)壓(ya)(ya)過低。

維修方法(fa):對(dui)于這種故(gu)障我們可(ke)以根據(ju)(ju)以上(shang)故(gu)障原因,來逐一(yi)進(jin)行排(pai)查(cha)(cha)(cha)。但(dan)在(zai)(zai)實際(ji)維修時(shi)(shi),可(ke)根據(ju)(ju)實際(ji)情況來進(jin)行排(pai)查(cha)(cha)(cha),不(bu)(bu)一(yi)定要(yao)逐一(yi)排(pai)查(cha)(cha)(cha)。首(shou)先用(yong)萬用(yong)表檢(jian)查(cha)(cha)(cha)一(yi)下高(gao)壓(ya)(ya)直流濾波電(dian)容(rong)是(shi)否變(bian)質(zhi),容(rong)量(liang)是(shi)否下降,能(neng)否正常充放電(dian)。如無(wu)以上(shang)現象,則測(ce)量(liang)一(yi)下開關功率(lv)(lv)管的(de)(de)(de)(de)柵極(G極)的(de)(de)(de)(de)限(xian)流電(dian)阻以及源極(S極)的(de)(de)(de)(de)過流保(bao)護檢(jian)測(ce)電(dian)阻是(shi)否變(bian)值,變(bian)質(zhi)或開焊,接(jie)觸不(bu)(bu)良。經判別后,若無(wu)問(wen)題,我們就檢(jian)查(cha)(cha)(cha)一(yi)下高(gao)頻變(bian)壓(ya)(ya)器(qi)的(de)(de)(de)(de)鐵芯(xin)是(shi)否完(wan)好(hao)無(wu)損。因在(zai)(zai)日(ri)常生活使(shi)用(yong)中,不(bu)(bu)可(ke)避免(mian)的(de)(de)(de)(de)重(zhong)摔或重(zhong)幢,使(shi)高(gao)頻變(bian)壓(ya)(ya)器(qi)的(de)(de)(de)(de)鐵芯(xin)損壞。使(shi)高(gao)頻變(bian)壓(ya)(ya)器(qi)的(de)(de)(de)(de)磁(ci)(ci)通量(liang),磁(ci)(ci)感應強度,以及磁(ci)(ci)路等(deng)都會(hui)受到(dao)很(hen)大(da)的(de)(de)(de)(de)影響,造(zao)成(cheng)傳(chuan)輸(shu)的(de)(de)(de)(de)效(xiao)率(lv)(lv),能(neng)量(liang)將會(hui)大(da)打折(zhe)扣。由于高(gao)頻變(bian)壓(ya)(ya)器(qi)為了減小渦(wo)流,增大(da)高(gao)頻交流電(dian)的(de)(de)(de)(de)傳(chuan)輸(shu)效(xiao)率(lv)(lv),它的(de)(de)(de)(de)鐵芯(xin)是(shi)用(yong)軟磁(ci)(ci)鐵氧體制作而成(cheng)的(de)(de)(de)(de)。這種磁(ci)(ci)性(xing)材料具有(you)高(gao)的(de)(de)(de)(de)導磁(ci)(ci)率(lv)(lv),但(dan)質(zhi)脆,易碎。因此(ci)它的(de)(de)(de)(de)損壞率(lv)(lv)也(ye)是(shi)很(hen)高(gao)的(de)(de)(de)(de)。因此(ci)在(zai)(zai)維修時(shi)(shi)千萬不(bu)(bu)要(yao)忘了檢(jian)查(cha)(cha)(cha)此(ci)處(chu),以免(mian)走彎路。除此(ci)之外還有(you)可(ke)能(neng)就是(shi)輸(shu)出濾波電(dian)容(rong)容(rong)量(liang)降低,甚至失容(rong)或開焊,虛(xu)(xu)(xu)接(jie);電(dian)源輸(shu)出限(xian)流電(dian)阻變(bian)值或虛(xu)(xu)(xu)接(jie),電(dian)源輸(shu)出線虛(xu)(xu)(xu)接(jie)等(deng)。在(zai)(zai)實際(ji)維修時(shi)(shi),這些因素都不(bu)(bu)要(yao)放過,都應檢(jian)查(cha)(cha)(cha)一(yi)下,以保(bao)證萬無(wu)一(yi)失。

7、散熱風扇不轉

這(zhe)種故障原(yuan)因主要是由于(yu)控制風扇的三極管(guan)(8550或8050)損壞(huai),或者風扇本(ben)身損壞(huai)或風葉被(bei)雜物卡住。但有(you)些開關電源中采用的是智能(neng)散(san)熱(re),對(dui)于(yu)采用這(zhe)種方式(shi)散(san)熱(re)的開關電源,熱(re)敏電阻損壞(huai)的概(gai)率是很大的。

維修方(fang)法:首先(xian)用(yong)(yong)萬用(yong)(yong)表測量一下控制風(feng)扇(shan)(shan)的(de)三極管是否損壞(huai)(huai),若測得(de)此管未(wei)損壞(huai)(huai)那就有可(ke)(ke)能是風(feng)扇(shan)(shan)本身(shen)損壞(huai)(huai)。可(ke)(ke)以把風(feng)扇(shan)(shan)從電(dian)(dian)路(lu)板上拔下來(lai),另外接(jie)上一個12V的(de)直流電(dian)(dian)(注(zhu)(zhu)意正負極),看是否轉動(dong)(dong)(dong),并看有無異物卡住。若擺動(dong)(dong)(dong)幾(ji)下風(feng)扇(shan)(shan)的(de)電(dian)(dian)線,風(feng)扇(shan)(shan)就轉動(dong)(dong)(dong),則(ze)說明電(dian)(dian)線內部有斷線或(huo)接(jie)頭接(jie)觸(chu)不(bu)(bu)良。若仍不(bu)(bu)轉動(dong)(dong)(dong),則(ze)風(feng)扇(shan)(shan)必壞(huai)(huai)。對于采(cai)用(yong)(yong)智能散熱(re)(re)的(de)開關(guan)電(dian)(dian)源來(lai)說,除(chu)按(an)上述(shu)檢查外,還應(ying)檢查一下熱(re)(re)敏電(dian)(dian)阻(zu)(zu)是否不(bu)(bu)良或(huo)損壞(huai)(huai),開焊等。但要注(zhu)(zhu)意此熱(re)(re)敏電(dian)(dian)阻(zu)(zu)為負溫(wen)度系數的(de)熱(re)(re)敏電(dian)(dian)阻(zu)(zu),更換時應(ying)注(zhu)(zhu)意。

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