一、工业开关电源电路图

1000W单组输出电源

二、开关电源工作原理

开(kai)(kai)(kai)(kai)关(guan)(guan)(guan)电(dian)(dian)(dian)源就是采用功率半导体器(qi)件(jian)作为(wei)开(kai)(kai)(kai)(kai)关(guan)(guan)(guan)元件(jian)，通(tong)过周期性通(tong)断(duan)开(kai)(kai)(kai)(kai)关(guan)(guan)(guan)，控(kong)制开(kai)(kai)(kai)(kai)关(guan)(guan)(guan)元件(jian)的(de)(de)(de)占(zhan)空(kong)比来调整输(shu)出(chu)电(dian)(dian)(dian)压(ya)。开(kai)(kai)(kai)(kai)关(guan)(guan)(guan)元件(jian)以(yi)一(yi)定(ding)的(de)(de)(de)时(shi)间(jian)(jian)间(jian)(jian)隔重复地(di)接(jie)通(tong)和断(duan)开(kai)(kai)(kai)(kai)，在(zai)开(kai)(kai)(kai)(kai)关(guan)(guan)(guan)无件(jian)接(jie)通(tong)时(shi)输(shu)入(ru)电(dian)(dian)(dian)源Vi通(tong)过开(kai)(kai)(kai)(kai)关(guan)(guan)(guan)S和滤波(bo)电(dian)(dian)(dian)路向负载RL提(ti)供能(neng)量，当开(kai)(kai)(kai)(kai)关(guan)(guan)(guan)S断(duan)开(kai)(kai)(kai)(kai)时(shi)，电(dian)(dian)(dian)路中的(de)(de)(de)储能(neng)装置（L1、C2、二极管D组成的(de)(de)(de)电(dian)(dian)(dian)路）向负载RL释放在(zai)开(kai)(kai)(kai)(kai)关(guan)(guan)(guan)接(jie)通(tong)时(shi)所储存的(de)(de)(de)能(neng)量，使(shi)负载得到连续(xu)而稳定(ding)的(de)(de)(de)能(neng)量。

VO=TON/T*Vi

VO 为负载两端(duan)的电压平均(jun)值

TON 为开关每(mei)次接(jie)通(tong)的时间

T 为开关(guan)通(tong)断(duan)的工作周期

由式可知(zhi)，改(gai)(gai)变(bian)开关接通时(shi)(shi)间和工(gong)作(zuo)(zuo)周期的(de)比(bi)(bi)例，VO间电压(ya)平均值也随之改(gai)(gai)变(bian)，因此，随着负(fu)载及输(shu)入电源电压(ya)的(de)变(bian)化自动调整TON和T的(de)比(bi)(bi)例便使输(shu)出电压(ya)VO维持不(bu)变(bian)。改(gai)(gai)变(bian)接通时(shi)(shi)间TON和工(gong)作(zuo)(zuo)周期比(bi)(bi)例亦即改(gai)(gai)变(bian)脉冲的(de)占空比(bi)(bi)，这(zhei)种(zhong)方法称为“时(shi)(shi)间比(bi)(bi)率控制”（TimeRationControl,缩写为TRC）。

按TRC控制原理，有三种方式：

1． 脉冲宽度调制（PulseWithModulation,缩写为PWM）

开关周期恒定，通过改(gai)变脉(mai)冲宽度来(lai)改(gai)变占(zhan)空比的方式。

2． 脉冲频率调制（PulseFrequencyModulation,缩写为PFM）

导通(tong)脉(mai)冲宽度恒定，通(tong)过改(gai)变开(kai)关工作频率(lv)来改(gai)变占(zhan)空比的方(fang)式(shi)。

3． 混合调制

导通脉冲宽(kuan)度(du)和开关工作频率均不固定，彼此都能改(gai)变的(de)方式，它是(shi)以上(shang)二种方式的(de)混(hun)合。

三、开关电源的维修技巧和常见故障

1．维修技巧

开(kai)关电源的维修(xiu)可(ke)分为两步进行：

断电情(qing)况(kuang)下，“看、闻、问、量”

看：打开电(dian)(dian)源(yuan)的(de)外壳，检(jian)(jian)查(cha)保险丝是否熔(rong)断，再观察电(dian)(dian)源(yuan)的(de)内(nei)部情况，如果发(fa)现电(dian)(dian)源(yuan)的(de)PCB板上(shang)有烧焦处或(huo)元件(jian)破(po)裂，则应(ying)重点检(jian)(jian)查(cha)此(ci)处元件(jian)及(ji)相(xiang)关(guan)电(dian)(dian)路元件(jian)。资产管理

闻(wen)：闻(wen)一下电源内部是否有(you)糊味，检查是否有(you)烧焦的(de)元器件。

问(wen)：问(wen)一下电(dian)源(yuan)损坏的经(jing)过，是否对电(dian)源(yuan)进行违(wei)规操作。

量(liang)：没(mei)通电(dian)(dian)(dian)前(qian)，用(yong)万(wan)(wan)用(yong)表量(liang)一下高压(ya)(ya)电(dian)(dian)(dian)容(rong)(rong)两端的(de)(de)电(dian)(dian)(dian)压(ya)(ya)先。如果是(shi)开(kai)(kai)(kai)关电(dian)(dian)(dian)源(yuan)不起振或(huo)开(kai)(kai)(kai)关管开(kai)(kai)(kai)路(lu)引起的(de)(de)故障，则大多(duo)数(shu)情况下，高压(ya)(ya)滤波(bo)电(dian)(dian)(dian)容(rong)(rong)两端的(de)(de)电(dian)(dian)(dian)压(ya)(ya)未泄(xie)放悼，此电(dian)(dian)(dian)压(ya)(ya)有(you)300多(duo)伏，需小心(xin)。用(yong)万(wan)(wan)用(yong)表测量(liang)AC电(dian)(dian)(dian)源(yuan)线两端的(de)(de)正反向(xiang)电(dian)(dian)(dian)阻(zu)(zu)及(ji)电(dian)(dian)(dian)容(rong)(rong)器充电(dian)(dian)(dian)情况，电(dian)(dian)(dian)阻(zu)(zu)值不应过低，否则电(dian)(dian)(dian)源(yuan)内(nei)部可能(neng)(neng)存在短路(lu)。电(dian)(dian)(dian)容(rong)(rong)器应能(neng)(neng)充放电(dian)(dian)(dian)。脱(tuo)开(kai)(kai)(kai)负载，分(fen)别测量(liang)各组输出(chu)端的(de)(de)对地电(dian)(dian)(dian)阻(zu)(zu)，正常时，表针应有(you)电(dian)(dian)(dian)容(rong)(rong)器充放电(dian)(dian)(dian)摆(bai)动，最后指(zhi)示的(de)(de)应为该路(lu)的(de)(de)泄(xie)放电(dian)(dian)(dian)阻(zu)(zu)的(de)(de)阻(zu)(zu)值。

加电检测

通电(dian)后观察(cha)电(dian)源是否有烧保(bao)险及个别元件(jian)冒烟等现象(xiang)，若有要及时切(qie)断供电(dian)进行(xing)检修。

测量高压滤波电(dian)容两端有无300伏输(shu)出，若无应(ying)重(zhong)点(dian)查整(zheng)流二极(ji)管、滤波电(dian)容等。

测量(liang)高频变(bian)压器次级线圈有(you)无输出，若(ruo)无应(ying)重点查开关管(guan)是否(fou)(fou)损(sun)坏，是否(fou)(fou)起振，保护电路是否(fou)(fou)动(dong)作等(deng)，若(ruo)有(you)则应(ying)重点检查各(ge)输出侧的(de)整流二极管(guan)、滤波电容、三通稳(wen)压管(guan)等(deng)。

如果电(dian)源(yuan)启动一下就停(ting)止，则(ze)(ze)该电(dian)源(yuan)处于保(bao)(bao)(bao)护状态下，可直接(jie)测量PWM芯片保(bao)(bao)(bao)护输入脚的电(dian)压(ya)，如果电(dian)压(ya)超出规定值，则(ze)(ze)说明(ming)电(dian)源(yuan)处于保(bao)(bao)(bao)护状态下，应重点检(jian)查(cha)产生保(bao)(bao)(bao)护的原(yuan)因。

2．常见故障

保险丝熔断

一般(ban)情况下(xia)(xia)(xia)，保(bao)(bao)险丝熔(rong)断(duan)(duan)说明电(dian)(dian)(dian)源的(de)(de)(de)内部线路(lu)(lu)(lu)有(you)(you)问题。由(you)于(yu)电(dian)(dian)(dian)源工(gong)作在高(gao)电(dian)(dian)(dian)压(ya)、大电(dian)(dian)(dian)流(liu)的(de)(de)(de)状态下(xia)(xia)(xia)，电(dian)(dian)(dian)网电(dian)(dian)(dian)压(ya)的(de)(de)(de)波动、浪(lang)涌都会引起电(dian)(dian)(dian)源内电(dian)(dian)(dian)流(liu)瞬间增大而(er)使保(bao)(bao)险丝熔(rong)断(duan)(duan)。重点应检(jian)查(cha)(cha)电(dian)(dian)(dian)源输入端的(de)(de)(de)整流(liu)二(er)极管(guan)，高(gao)压(ya)滤波电(dian)(dian)(dian)解电(dian)(dian)(dian)容，逆(ni)变功率开(kai)关(guan)管(guan)等，检(jian)查(cha)(cha)一下(xia)(xia)(xia)这此元(yuan)器(qi)件(jian)(jian)(jian)有(you)(you)无击穿、开(kai)路(lu)(lu)(lu)、损坏等。如(ru)果确实是(shi)保(bao)(bao)险丝熔(rong)断(duan)(duan)，应该(gai)首先查(cha)(cha)看(kan)(kan)电(dian)(dian)(dian)路(lu)(lu)(lu)板上(shang)的(de)(de)(de)各个(ge)元(yuan)件(jian)(jian)(jian)，看(kan)(kan)这些元(yuan)件(jian)(jian)(jian)的(de)(de)(de)外(wai)表(biao)有(you)(you)没(mei)有(you)(you)被烧糊，有(you)(you)没(mei)有(you)(you)电(dian)(dian)(dian)解液溢出(chu)，如(ru)果没(mei)有(you)(you)发现上(shang)述情况，则用万(wan)用表(biao)测(ce)量(liang)开(kai)关(guan)管(guan)有(you)(you)无击穿短路(lu)(lu)(lu)。需要特(te)别注意(yi)的(de)(de)(de)是(shi)：切不可在查(cha)(cha)出(chu)某元(yuan)件(jian)(jian)(jian)损坏时，更换后直接开(kai)机，这样很有(you)(you)可能(neng)由(you)于(yu)其(qi)它(ta)高(gao)压(ya)元(yuan)件(jian)(jian)(jian)仍有(you)(you)故(gu)障又将更换的(de)(de)(de)元(yuan)件(jian)(jian)(jian)损坏，一定要对上(shang)述电(dian)(dian)(dian)路(lu)(lu)(lu)的(de)(de)(de)所(suo)有(you)(you)高(gao)压(ya)元(yuan)件(jian)(jian)(jian)进行全(quan)面检(jian)查(cha)(cha)测(ce)量(liang)后，才(cai)能(neng)彻底排除保(bao)(bao)险丝熔(rong)断(duan)(duan)的(de)(de)(de)故(gu)障。

无直流电压输出或电压输出不稳定

如(ru)果保险丝是完好的(de)，在(zai)(zai)有(you)负(fu)载情(qing)况(kuang)下，各级(ji)(ji)直流(liu)(liu)(liu)(liu)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)压(ya)(ya)(ya)无(wu)(wu)输(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)。这种(zhong)情(qing)况(kuang)主要(yao)(yao)是以下原(yuan)因造成(cheng)的(de)：电(dian)(dian)(dian)(dian)(dian)(dian)(dian)源中(zhong)出(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)现(xian)(xian)(xian)开(kai)路(lu)(lu)、短(duan)路(lu)(lu)现(xian)(xian)(xian)象，过(guo)压(ya)(ya)(ya)、过(guo)流(liu)(liu)(liu)(liu)保护电(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)出(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)现(xian)(xian)(xian)故(gu)障(zhang)，辅(fu)助电(dian)(dian)(dian)(dian)(dian)(dian)(dian)源故(gu)障(zhang)，振荡电(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)没有(you)工(gong)作(zuo)，电(dian)(dian)(dian)(dian)(dian)(dian)(dian)源负(fu)载过(guo)重，高(gao)(gao)(gao)(gao)频整(zheng)流(liu)(liu)(liu)(liu)滤(lv)波(bo)(bo)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)中(zhong)整(zheng)流(liu)(liu)(liu)(liu)二(er)极(ji)(ji)管(guan)被击穿(chuan)(chuan)，滤(lv)波(bo)(bo)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)容漏电(dian)(dian)(dian)(dian)(dian)(dian)(dian)等(deng)(deng)。在(zai)(zai)用万用表测(ce)量(liang)次级(ji)(ji)元(yuan)(yuan)(yuan)件(jian)，排除了(le)高(gao)(gao)(gao)(gao)频整(zheng)流(liu)(liu)(liu)(liu)二(er)极(ji)(ji)管(guan)击穿(chuan)(chuan)、负(fu)载短(duan)路(lu)(lu)的(de)情(qing)况(kuang)后，如(ru)果这时输(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)为(wei)零(ling)，则(ze)可以肯定是电(dian)(dian)(dian)(dian)(dian)(dian)(dian)源的(de)控制(zhi)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)出(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)了(le)故(gu)障(zhang)。若有(you)部分电(dian)(dian)(dian)(dian)(dian)(dian)(dian)压(ya)(ya)(ya)输(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)说(shuo)明前级(ji)(ji)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)工(gong)作(zuo)正(zheng)常，故(gu)障(zhang)出(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)在(zai)(zai)高(gao)(gao)(gao)(gao)频整(zheng)流(liu)(liu)(liu)(liu)滤(lv)波(bo)(bo)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)中(zhong)。高(gao)(gao)(gao)(gao)频滤(lv)波(bo)(bo)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)主要(yao)(yao)由(you)整(zheng)流(liu)(liu)(liu)(liu)二(er)极(ji)(ji)管(guan)及低压(ya)(ya)(ya)滤(lv)波(bo)(bo)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)容组成(cheng)直流(liu)(liu)(liu)(liu)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)压(ya)(ya)(ya)输(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)，其(qi)中(zhong)整(zheng)流(liu)(liu)(liu)(liu)二(er)极(ji)(ji)管(guan)击穿(chuan)(chuan)会使(shi)该(gai)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)无(wu)(wu)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)压(ya)(ya)(ya)输(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)，滤(lv)波(bo)(bo)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)容漏电(dian)(dian)(dian)(dian)(dian)(dian)(dian)会造成(cheng)输(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)压(ya)(ya)(ya)不稳等(deng)(deng)故(gu)障(zhang)。用万用表静态测(ce)量(liang)对应元(yuan)(yuan)(yuan)件(jian)即可检(jian)查(cha)(cha)出(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)其(qi)损坏的(de)元(yuan)(yuan)(yuan)件(jian)。例：某一24伏直流(liu)(liu)(liu)(liu)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)机供电(dian)(dian)(dian)(dian)(dian)(dian)(dian)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)源通(tong)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)后无(wu)(wu)直流(liu)(liu)(liu)(liu)24伏输(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu) ，拆开(kai)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)源外壳，观察保险丝未烧断且电(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)板无(wu)(wu)明显的(de)烧焦(jiao)处或破裂元(yuan)(yuan)(yuan)件(jian)，在(zai)(zai)未通(tong)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)情(qing)况(kuang)下量(liang)AC输(shu)(shu)(shu)入端(duan)(duan)(duan)阻值和(he)DC输(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)端(duan)(duan)(duan)阻值正(zheng)常，量(liang)开(kai)关(guan)(guan)管(guan)、整(zheng)流(liu)(liu)(liu)(liu)桥(qiao)、整(zheng)流(liu)(liu)(liu)(liu)管(guan)等(deng)(deng)重要(yao)(yao)元(yuan)(yuan)(yuan)件(jian)正(zheng)常，故(gu)判断不存(cun)在(zai)(zai)内(nei)部严重短(duan)路(lu)(lu)的(de)可能，估计(ji)保护电(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)动(dong)作(zuo)。经检(jian)查(cha)(cha)此开(kai)关(guan)(guan)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)源采用U3842 PWM控制(zhi)芯片(pian)，经查(cha)(cha)找(zhao)相关(guan)(guan)的(de)资料得知(zhi)，当U3842芯片(pian)的(de)3端(duan)(duan)(duan)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)压(ya)(ya)(ya)高(gao)(gao)(gao)(gao)于1伏时，内(nei)部电(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)(liu)敏感(gan)比较(jiao)器(qi)输(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)高(gao)(gao)(gao)(gao)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)平，将PWM锁存(cun)器(qi)复位使(shi)输(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)关(guan)(guan)闭。通(tong)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)测(ce)量(liang)U3842的(de)3端(duan)(duan)(duan)高(gao)(gao)(gao)(gao)于1伏，6端(duan)(duan)(duan)无(wu)(wu)输(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)，经检(jian)查(cha)(cha)相关(guan)(guan)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)，发现(xian)(xian)(xian)稳压(ya)(ya)(ya)管(guan)D2击穿(chuan)(chuan)，如(ru)图3.故(gu)PC1导(dao)通(tong)，致使(shi)U3842的(de)3端(duan)(duan)(duan)为(wei)高(gao)(gao)(gao)(gao)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)平，故(gu)6端(duan)(duan)(duan)无(wu)(wu)输(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)，开(kai)关(guan)(guan)管(guan)不工(gong)作(zuo)，直流(liu)(liu)(liu)(liu)侧无(wu)(wu)直流(liu)(liu)(liu)(liu)输(shu)(shu)(shu)出(chu)(chu)(chu)(chu)(chu)(chu)(chu)(chu)。更换(huan)同型号稳压(ya)(ya)(ya)管(guan)D2，故(gu)障(zhang)解除。

电源负载能力差

电(dian)(dian)(dian)源(yuan)(yuan)负(fu)载(zai)(zai)能力差是一个(ge)常见的(de)故(gu)障，一般都(dou)是出现在老(lao)(lao)式或工作时(shi)间(jian)长的(de)电(dian)(dian)(dian)源(yuan)(yuan)中，主要(yao)原因(yin)是各(ge)元器件老(lao)(lao)化，开(kai)关管的(de)工作不稳定，没(mei)有(you)及时(shi)进(jin)行散(san)热(re)等。应重点检(jian)查(cha)稳压(ya)(ya)二(er)极管是否发热(re)漏电(dian)(dian)(dian)，整流二(er)极管损坏、高压(ya)(ya)滤波(bo)电(dian)(dian)(dian)容损坏等。例(li)：我厂近红处激光(guang)(guang)光(guang)(guang)谱仪(yi)（VECTOR 22），开(kai)机后无法(fa)完成自检(jian)并(bing)报(bao)警且主板指示灯不断闪烁。经检(jian)查(cha)，供光(guang)(guang)谱仪(yi)主板的(de)直流5V电(dian)(dian)(dian)源(yuan)(yuan)仅剩(sheng)2.3伏(fu)左右，脱开(kai)5V直流电(dian)(dian)(dian)源(yuan)(yuan)的(de)负(fu)载(zai)(zai)，通(tong)(tong)电(dian)(dian)(dian)再次测量5V直流电(dian)(dian)(dian)源(yuan)(yuan)，这时(shi)则(ze)有(you)5V，初步判断此5V直流电(dian)(dian)(dian)源(yuan)(yuan)带载(zai)(zai)能力差，拆开(kai)电(dian)(dian)(dian)源(yuan)(yuan)外壳进(jin)行检(jian)修，由于没(mei)有(you)带负(fu)载(zai)(zai)时(shi)，通(tong)(tong)电(dian)(dian)(dian)有(you)直流5V输出，故(gu)重点检(jian)查(cha)次级线(xian)圈(quan)侧的(de)输出整流电(dian)(dian)(dian)路(lu)，给(ji)5伏(fu)电(dian)(dian)(dian)源(yuan)(yuan)接(jie)上(shang)假(jia)负(fu)载(zai)(zai)通(tong)(tong)电(dian)(dian)(dian)进(jin)行测量发现三通(tong)(tong)稳压(ya)(ya)7805的(de)1、2脚(jiao)之间(jian)电(dian)(dian)(dian)压(ya)(ya)为5.2伏(fu)，2、3脚(jiao)之间(jian)却剩(sheng)2.3伏(fu)，如图4，故(gu)判断三通(tong)(tong)稳压(ya)(ya)管7805性(xing)能变坏，更换三通(tong)(tong)稳压(ya)(ya)管7805故(gu)障解决(jue)。

联系(xi)方式：邹先生

联(lian)系电话：0755-83888366-8022

手机：18123972950

QQ：2880195519

联系地址：深圳市福(fu)田区车公庙天安数(shu)码城天吉大(da)厦CD座(zuo)5C1

请(qing)搜微信公众号:“KIA半导体(ti)”或扫一扫下图“关注(zhu)”官(guan)方微信公众号

请“关(guan)注”官方(fang)微信公众号:提供(gong)  MOS管  技(ji)术帮助