陶老師ESD、EMI、EMC講座(3)——防雷設計
發布時間:2010-08-09 來源:電子元件技術網
下xia麵mian我wo們men講jiang雷lei電dian防fang護hu。雷lei電dian防fang護hu對dui於yu發fa電dian機ji那na邊bian來lai說shuo已yi經jing是shi很hen成cheng熟shu了le,整zheng天tian打da雷lei發fa電dian廠chang都dou沒mei有you癱tan瘓huan,為wei什shen麼me能neng夠gou做zuo得de這zhe麼me好hao?就jiu是shi把ba發fa電dian機ji的de中zhong線xian接jie地di,與yu大da地di相xiang連lian接jie,以yi後hou跟gen外wai麵mian輸shu送song電dian,上shang麵mian的de高gao壓ya電dian塔ta上shang一yi般ban都dou拉la有you一yi根gen線xian或huo兩liang根gen線xian,就jiu是shi避bi雷lei線xian,避bi雷lei線xian與yu中zhong線xian不bu同tong,中zhong線xian單dan獨du接jie地di,地di線xian是shi單dan獨du給gei避bi雷lei用yong的de,不bu電dian的de,這zhe叫jiao三san相xiang四si線xian製zhi供gong電dian。現在美國推出一個標準是三相五線製,就是中線接地,用電這邊也要另外接地,接地不與那邊相連,叫做三相五線製,一般中線是不接的,到了變壓器這(zhe)邊(bian)以(yi)後(hou),這(zhe)裏(li)也(ye)有(you)一(yi)個(ge)中(zhong)線(xian),中(zhong)線(xian)也(ye)接(jie)地(di),還(hai)有(you)變(bian)壓(ya)器(qi)的(de)外(wai)殼(ke)也(ye)接(jie)地(di),這(zhe)邊(bian)有(you)個(ge)中(zhong)線(xian),也(ye)接(jie)地(di),三(san)個(ge)地(di)最(zui)好(hao)都(dou)不(bu)要(yao)接(jie)在(zai)一(yi)起(qi),越(yue)分(fen)開(kai)越(yue)好(hao),這(zhe)邊(bian)的(de)中(zhong)線(xian)是(shi)一(yi)個(ge)小(xiao)線(xian)路(lu),當(dang)成(cheng)供(gong)電(dian)線(xian)路(lu),對(dui)變(bian)壓(ya)器(qi)有(you)保(bao)護(hu),對(dui)使(shi)用(yong)設(she)備(bei)不(bu)保(bao)護(hu),名(ming)義(yi)上(shang)是(shi)接(jie)地(di)的(de),但(dan)那(na)邊(bian)實(shi)際(ji)上(shang)沒(mei)有(you)接(jie)地(di)。接(jie)地(di)的(de)概(gai)念(nian)是(shi)這(zhe)樣(yang),任(ren)何(he)一(yi)個(ge)導(dao)線(xian),當(dang)你(ni)充(chong)放(fang)電(dian)很(hen)快(kuai)的(de)時(shi)候(hou)電(dian)磁(ci)波(bo)傳(chuan)播(bo)的(de)速(su)度(du)是(shi)有(you)限(xian)的(de),比(bi)如(ru)說(shuo)電(dian)磁(ci)波(bo)在(zai)空(kong)氣(qi)裏(li)麵(mian)傳(chuan)是(shi)30萬公裏/秒,在導體裏麵傳播沒有這麼快,一般隻有空氣中的1/3或1/2左(zuo)右(you),少(shao)了(le)之(zhi)後(hou)靈(ling)敏(min)度(du)沒(mei)有(you)這(zhe)麼(me)高(gao),當(dang)放(fang)電(dian)在(zai)每(mei)秒(miao)計(ji)的(de)時(shi)候(hou),放(fang)電(dian)的(de)時(shi)候(hou)經(jing)過(guo)多(duo)少(shao)秒(miao)鍾(zhong)才(cai)到(dao)這(zhe)裏(li)?當(dang)電(dian)流(liu)傳(chuan)到(dao)這(zhe)邊(bian)來(lai),那(na)邊(bian)早(zao)就(jiu)燒(shao)掉(diao)了(le)。所(suo)以(yi)在(zai)快(kuai)速(su)充(chong)放(fang)電(dian)裏(li)麵(mian)不(bu)要(yao)隨(sui)便(bian)把(ba)某(mou)一(yi)點(dian)接(jie)地(di),某(mou)一(yi)點(dian)與(yu)另(ling)外(wai)一(yi)點(dian)看(kan)成(cheng)同(tong)樣(yang)的(de)功(gong)能(neng),因(yin)為(wei)有(you)一(yi)個(ge)時(shi)間(jian)差(cha)的(de)問(wen)題(ti)。你(ni)認(ren)為(wei)它(ta)在(zai)這(zhe)裏(li)接(jie)地(di)是(shi)對(dui)直(zhi)流(liu)可(ke)以(yi),對(dui)交(jiao)流(liu)也(ye)行(xing),因(yin)為(wei)是(shi)排(pai)隊(dui)走(zou),沒(mei)有(you)輪(lun)到(dao)你(ni),接(jie)地(di)也(ye)沒(mei)有(you)用(yong)。
雷(lei)電(dian)的(de)原(yuan)理(li)就(jiu)是(shi)這(zhe)樣(yang),這(zhe)一(yi)塊(kuai)是(shi)帶(dai)電(dian)的(de),降(jiang)到(dao)這(zhe)兩(liang)根(gen)線(xian)上(shang)麵(mian)去(qu)。對(dui)地(di)球(qiu)來(lai)說(shuo)相(xiang)當(dang)於(yu)一(yi)個(ge)分(fen)布(bu)電(dian)容(rong),雷(lei)電(dian)就(jiu)是(shi)一(yi)個(ge)共(gong)模(mo)信(xin)號(hao),相(xiang)當(dang)於(yu)對(dui)整(zheng)個(ge)電(dian)容(rong)進(jin)行(xing)放(fang)電(dian)。放(fang)電(dian)有(you)幾(ji)個(ge)回(hui)路(lu),上(shang)麵(mian)的(de)電(dian)流(liu)通(tong)過(guo)電(dian)容(rong)到(dao)達(da)地(di),電(dian)流(liu)通(tong)過(guo)電(dian)容(rong)到(dao)大(da)地(di),這(zhe)是(shi)共(gong)模(mo)電(dian)容(rong)。這(zhe)部(bu)分(fen)電(dian)流(liu)也(ye)通(tong)過(guo)電(dian)容(rong)下(xia)地(di),還(hai)有(you)一(yi)部(bu)分(fen)通(tong)過(guo)變(bian)壓(ya)器(qi)分(fen)布(bu)電(dian)容(rong)傳(chuan)到(dao)負(fu)載(zai)這(zhe)邊(bian),然(ran)後(hou)通(tong)過(guo)分(fen)布(bu)電(dian)容(rong)下(xia)地(di)。你(ni)可(ke)以(yi)認(ren)為(wei)這(zhe)個(ge)電(dian)容(rong)是(shi)大(da)地(di)的(de)分(fen)布(bu)電(dian)容(rong),實(shi)際(ji)上(shang)不(bu)跟(gen)大(da)地(di)它(ta)本(ben)身(shen)也(ye)是(shi)分(fen)布(bu)電(dian)容(rong),任(ren)何(he)一(yi)個(ge)導(dao)體(ti)隻(zhi)要(yao)電(dian)位(wei)改(gai)變(bian)就(jiu)相(xiang)當(dang)於(yu)一(yi)個(ge)電(dian)容(rong),比(bi)如(ru)說(shuo)你(ni)的(de)身(shen)體(ti)帶(dai)電(dian),另(ling)外(wai)一(yi)個(ge)不(bu)帶(dai)電(dian),兩(liang)個(ge)人(ren)握(wo)手(shou)就(jiu)會(hui)把(ba)電(dian)荷(he)傳(chuan)到(dao)另(ling)外(wai)一(yi)個(ge)人(ren)身(shen)上(shang),相(xiang)當(dang)於(yu)你(ni)這(zhe)個(ge)電(dian)容(rong)對(dui)另(ling)外(wai)一(yi)個(ge)電(dian)容(rong)放(fang)電(dian),另(ling)外(wai)一(yi)個(ge)相(xiang)對(dui)來(lai)說(shuo)是(shi)充(chong)電(dian),是(shi)一(yi)個(ge)充(chong)放(fang)電(dian)的(de)過(guo)程(cheng)。
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除了共模電流以外,還有一個差模電流,為什麼?兩個回路都放電的時候,放電的時間、強(qiang)度(du)不(bu)一(yi)樣(yang),有(you)的(de)放(fang)快(kuai)一(yi)點(dian),有(you)的(de)放(fang)慢(man)一(yi)點(dian),如(ru)果(guo)兩(liang)個(ge)東(dong)西(xi)的(de)速(su)度(du)都(dou)一(yi)樣(yang),任(ren)何(he)電(dian)位(wei)差(cha)都(dou)是(shi)一(yi)樣(yang)的(de)就(jiu)不(bu)會(hui)產(chan)生(sheng)差(cha)模(mo)電(dian)流(liu)了(le)。但(dan)是(shi)有(you)時(shi)候(hou)有(you)一(yi)些(xie)是(shi)中(zhong)線(xian)接(jie)地(di),放(fang)電(dian)快(kuai)一(yi)些(xie),相(xiang)對(dui)來(lai)說(shuo)電(dian)壓(ya)跌(die)得(de)特(te)別(bie)快(kuai),另(ling)外(wai)一(yi)個(ge)跌(die)得(de)特(te)別(bie)慢(man),就(jiu)會(hui)產(chan)生(sheng)差(cha)模(mo),首(shou)先(xian)是(shi)共(gong)模(mo),然(ran)後(hou)產(chan)生(sheng)差(cha)模(mo)。
下(xia)麵(mian)講(jiang)一(yi)下(xia)共(gong)模(mo)電(dian)壓(ya)對(dui)電(dian)路(lu)的(de)損(sun)害(hai)。其(qi)實(shi)共(gong)模(mo)電(dian)壓(ya)對(dui)開(kai)關(guan)電(dian)容(rong)前(qian)麵(mian)的(de)影(ying)響(xiang)不(bu)是(shi)很(hen)大(da),最(zui)大(da)是(shi)後(hou)麵(mian)一(yi)點(dian),通(tong)過(guo)電(dian)壓(ya)器(qi)分(fen)布(bu)電(dian)路(lu),以(yi)前(qian)的(de)模(mo)式(shi)電(dian)路(lu)電(dian)壓(ya)用(yong)得(de)很(hen)低(di),都(dou)是(shi)1v-5vzuoyou,namijirongyijichuan,dianrongyexiangdangxiao。conglimianchuanjinqudedianyajingguolvbobuduandexishoujiangxialai,yibanyoushangqianfu,rongyibahoumiandejichuan。zaishijianguochengzhongweilefanglei,zhejigeweizhizuihaozaishangmianbuyigeleidiandianrong,duifangleidianjichuanhenyouxiao。gongmodianyajinquyihoushunjianjichuan,ruguodianzimeiduankai,waimiandedianliuhuijixuyanxuxiaqubatashaodiao,ruguobeiyigedianrongshangqu,gongmodianrongtongguodianrongyixiazibataxishoudiao,rangjigedianronghuxiangtongdianwei,jigemozubuhuinamerongyijichuan。
現xian在zai很hen多duo防fang雷lei都dou是shi用yong壓ya敏min電dian阻zu或huo放fang電dian器qi件jian,我wo在zai這zhe裏li告gao訴su你ni,最zui有you效xiao的de是shi在zai排pai版ban的de時shi候hou,在zai電dian源yuan線xian那na個ge地di方fang排pai出chu一yi個ge放fang電dian裝zhuang置zhi,這zhe樣yang既ji經jing濟ji又you實shi用yong,放fang電dian管guan沒mei有you那na麼me大da的de功gong率lv吸xi收shou掉diao雷lei電dian的de能neng量liang,如ru果guo排pai一yi個ge像xiang鋸ju齒chi一yi樣yang的de放fang電dian裝zhuang置zhi,隻zhi要yao能neng量liang不bu大da基ji本ben上shang都dou能neng夠gou吸xi收shou。發fa電dian距ju離li一yi般ban是shi6mm,現在規定低於6mm就不合格,因為測試的時候,打火的時候耐壓2000v,交流2000v,其實正常放電是10000v/mm,也就是說1000v/cm,要留一定的安全係數,所以不測你,不到6mm就算不合格,所以一定要6mm,真正打雷進來,經過放電,電壓輸入進來隻有6000v。前麵輸入電壓是幾十萬伏都沒有關係,一放電它就在6000v的範圍裏麵,進來隻有6000v了le,其qi他ta都dou放fang掉diao。放fang掉diao以yi後hou吸xi收shou才cai有you效xiao,最zui有you效xiao的de裏li麵mian有you一yi個ge限xian流liu電dian感gan,還hai有you共gong模mo電dian流liu,對dui雷lei電dian有you效xiao。差cha模mo會hui通tong過guo差cha模mo電dian容rong來lai吸xi收shou,放fang電dian是shi一yi樣yang的de,有you一yi個ge差cha模mo,可ke以yi用yong電dian容rong吸xi收shou。電dian容rong上shang麵mian標biao的de是shi耐nai壓ya交jiao流liu250v,實際測的直流耐壓是8000v以上,大家要注意一下。這個CX標的是250v,買的浪湧電壓都在5000v以上,用5000v電壓都打不穿,但是標的是250v,這是安全規定。
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剛gang才cai在zai休xiu息xi的de時shi候hou與yu大da家jia交jiao流liu,大da家jia真zhen的de很hen感gan興xing趣qu,熱re情qing也ye相xiang當dang高gao,我wo也ye希xi望wang大da家jia通tong過guo這zhe個ge機ji會hui互hu相xiang認ren識shi,多duo多duo交jiao流liu,特te別bie是shi這zhe些xie經jing驗yan之zhi談tan在zai書shu上shang是shi很hen難nan找zhao到dao的de。如ru果guo還hai要yao有you更geng深shen的de研yan究jiu,我wo建jian議yi你ni有you機ji會hui去qu歐ou洲zhou最zui大da的de物wu理li研yan究jiu所suo,現xian在zai研yan究jiu的de課ke題ti與yu此ci相xiang關guan,就jiu是shi電dian磁ci層ceng理li論lun,現xian在zai空kong間jian物wu理li也ye好hao,電dian磁ci層ceng理li論lun是shi最zui難nan解jie決jue的de問wen題ti,現xian在zai有you四si個ge力li,如ru果guo能neng夠gou把ba四si個ge力li統tong一yi起qi來lai,宇yu宙zhou空kong間jian的de問wen題ti基ji本ben上shang都dou可ke以yi解jie答da。一yi個ge是shi重zhong力li,原yuan來lai無wu法fa解jie釋shi重zhong力li如ru何he產chan生sheng,就jiu有you重zhong力li層ceng。還hai有you電dian場chang力li,無wu法fa解jie釋shi這zhe個ge怎zen麼me產chan生sheng,就jiu有you電dian場chang力li,還hai有you磁ci場chang力li、合he力li,如ru果guo四si個ge力li統tong一yi在zai一yi起qi就jiu可ke以yi解jie決jue。在zai書shu上shang介jie紹shao電dian磁ci層ceng,一yi點dian點dian東dong西xi都dou全quan部bu解jie決jue了le,包bao括kuo量liang綱gang都dou沒mei有you統tong一yi,大da家jia都dou在zai爭zheng論lun,電dian場chang強qiang度du和he磁ci場chang強qiang度du的de量liang綱gang都dou沒mei有you解jie決jue。按an照zhao電dian場chang的de強qiang度du,原yuan來lai牛niu頓dun用yong力li表biao示shi,這zhe個ge東dong西xi與yu現xian在zai電dian工gong學xue不bu搭da架jia了le。特te別bie是shi電dian流liu強qiang度du通tong過guo兩liang根gen導dao線xian多duo少shao,直zhi徑jing多duo大da、dianliuduodalailiangli,zhezhongcichangqiangduduiwomenshiyongyouduodaguanxi?dangchudingxialaiyoubuhaotuifan,xianzaimanmanyinjinleciganyingqiangdu,bacichangqiangdupingbidiaole,zaidianyajisuanlidajiadouzhidaociganyinglidu,haiyoudianchangqiangdumanmanyepingbidiaole,jiushiyongdianweitidu。
下(xia)麵(mian)我(wo)們(men)講(jiang)一(yi)些(xie)具(ju)體(ti)的(de)。這(zhe)是(shi)一(yi)個(ge)開(kai)關(guan)電(dian)源(yuan),開(kai)關(guan)電(dian)源(yuan)被(bei)雷(lei)劈(pi)的(de)時(shi)候(hou),輸(shu)入(ru)回(hui)路(lu)基(ji)本(ben)上(shang)都(dou)燒(shao)了(le),假(jia)如(ru)沒(mei)燒(shao)是(shi)什(shen)麼(me)樣(yang)的(de)?可(ke)以(yi)看(kan)看(kan),這(zhe)是(shi)橋(qiao)堆(dui),這(zhe)兩(liang)個(ge)是(shi)Ydianrong,zhelimianhaiyouyigeyamindianzu。zheshigongmoxianquan,leipiyihouquanbushaole,shuomingyamindianzumeiyouqidaoshenmebaohuzuoyong,lianggedianrongdoushaole,shuomingdianganxiangdang、相(xiang)當(dang)地(di)高(gao)。為(wei)了(le)防(fang)止(zhi)雷(lei)電(dian),首(shou)先(xian)前(qian)麵(mian)一(yi)定(ding)要(yao)加(jia)一(yi)個(ge)能(neng)量(liang)吸(xi)收(shou),比(bi)較(jiao)大(da)的(de)東(dong)西(xi),成(cheng)本(ben)相(xiang)對(dui)來(lai)說(shuo)比(bi)較(jiao)低(di),像(xiang)試(shi)驗(yan)站(zhan)裏(li)麵(mian)的(de)放(fang)電(dian)裝(zhuang)置(zhi),那(na)個(ge)東(dong)西(xi)沒(mei)有(you)地(di)方(fang)裝(zhuang),也(ye)貴(gui)得(de)很(hen)。在(zai)硬(ying)紙(zhi)板(ban)上(shang)麵(mian)排(pai)幾(ji)個(ge)鋸(ju)齒(chi),中(zhong)間(jian)隔(ge)一(yi)個(ge)頭(tou)就(jiu)行(xing)了(le)。如(ru)果(guo)中(zhong)間(jian)隔(ge)6mm也可以。有一個一級電感,電感可以使瞬間上去很快的電壓降下來,突然加一個1萬伏、10萬wan伏fu,加jia上shang去qu隻zhi有you這zhe兩liang端duan,另ling外wai兩liang端duan建jian立li不bu起qi來lai,所suo以yi剛gang加jia進jin去qu的de時shi候hou對dui雷lei電dian來lai說shuo,大da部bu分fen能neng量liang都dou被bei吸xi收shou掉diao了le。後hou麵mian經jing過guo這zhe個ge以yi後hou,剩sheng餘yu部bu分fen通tong過guo共gong膜mo電dian容rong繼ji續xu吸xi收shou,吸xi收shou完wan以yi後hou還hai有you差cha模mo部bu分fen,產chan生sheng的de差cha模mo部bu分fen通tong過guo電dian容rong把ba差cha模mo吸xi收shou掉diao。共gong模mo電dian容rong和he差cha模mo電dian容rong具ju有you抑yi製zhi傳chuan導dao幹gan擾rao的de作zuo用yong,對dui雷lei電dian也ye有you抑yi製zhi作zuo用yong,所suo以yi很hen多duo人ren也ye在zai問wen,電dian容rong接jie到dao前qian麵mian好hao還hai是shi接jie在zai後hou麵mian好hao?這zhe個ge東dong西xi看kan你ni有you什shen麼me作zuo用yong,如ru果guo隻zhi是shi為wei了le防fangEMI電(dian)磁(ci)幹(gan)擾(rao)的(de)話(hua),接(jie)在(zai)越(yue)前(qian)麵(mian)越(yue)好(hao),接(jie)在(zai)測(ce)試(shi)儀(yi)表(biao)的(de)輸(shu)入(ru)端(duan)最(zui)好(hao),接(jie)到(dao)那(na)裏(li)把(ba)信(xin)號(hao)全(quan)部(bu)短(duan)路(lu)掉(diao)了(le),就(jiu)看(kan)不(bu)到(dao)了(le)。但(dan)是(shi)對(dui)於(yu)雷(lei)電(dian),你(ni)接(jie)到(dao)後(hou)麵(mian)要(yao)好(hao)很(hen)多(duo),所(suo)以(yi)這(zhe)主(zhu)要(yao)是(shi)防(fang)雷(lei)的(de),你(ni)就(jiu)不(bu)要(yao)考(kao)慮(lv)電(dian)磁(ci)幹(gan)擾(rao)和(he)EMC了,盡量把兩個放在後麵。
另外一個是接地,這個特別重要,不能接到最輸入端的地方,應該接在後麵,一打雷造成很大的回路,把裏麵的東西燒壞、擊穿,這個放電回路是越小越好,這個寬大一點,放電電流都在30個ge安an培pei以yi上shang,如ru果guo聽ting到dao雷lei聲sheng的de放fang電dian都dou是shi上shang萬wan安an培pei,如ru果guo沒mei有you雷lei聲sheng隻zhi是shi把ba東dong西xi擊ji穿chuan都dou有you幾ji萬wan安an培pei。這zhe樣yang相xiang對dui來lai說shuo電dian容rong不bu是shi很hen大da,都dou是shi幾ji百bai安an培pei或huo幾ji十shi安an培pei,盡jin量liang把ba地di線xian、麵(mian)積(ji)加(jia)大(da),而(er)且(qie)最(zui)好(hao)接(jie)在(zai)機(ji)殼(ke)上(shang),如(ru)果(guo)放(fang)在(zai)機(ji)殼(ke)上(shang),雷(lei)擊(ji)一(yi)擊(ji),上(shang)麵(mian)帶(dai)的(de)電(dian)與(yu)前(qian)麵(mian)起(qi)來(lai)就(jiu)聚(ju)集(ji)起(qi)來(lai),所(suo)有(you)的(de)都(dou)是(shi)擋(dang)電(dian)位(wei),一(yi)有(you)擋(dang)電(dian)位(wei)以(yi)後(hou)裏(li)麵(mian)不(bu)存(cun)在(zai)充(chong)放(fang)電(dian)的(de)問(wen)題(ti)了(le)。大(da)家(jia)知(zhi)道(dao)吧(ba)?一(yi)個(ge)封(feng)閉(bi)的(de)金(jin)屬(shu)裏(li)頭(tou),不(bu)管(guan)外(wai)麵(mian)帶(dai)多(duo)高(gao)的(de)電(dian)壓(ya),中(zhong)間(jian)都(dou)是(shi)不(bu)帶(dai)電(dian)的(de)。一(yi)根(gen)導(dao)線(xian)不(bu)管(guan)通(tong)多(duo)少(shao)安(an)培(pei)的(de)電(dian)流(liu),中(zhong)間(jian)的(de)電(dian)壓(ya)、電dian流liu也ye是shi等deng於yu零ling的de。電dian流liu分fen布bu都dou是shi在zai表biao麵mian,大da家jia可ke以yi做zuo一yi個ge試shi驗yan,做zuo一yi個ge金jin屬shu球qiu,在zai外wai麵mian充chong電dian,看kan看kan中zhong間jian有you沒mei有you電dian壓ya,應ying該gai沒mei有you。一yi般ban都dou是shi這zhe樣yang做zuo的de,先xian把ba一yi個ge東dong西xi屏ping蔽bi起qi來lai,或huo者zhe接jie大da地di,不bu接jie也ye沒mei有you關guan係xi,裏li麵mian不bu帶dai電dian的de,或huo者zhe是shi空kong的de都dou可ke以yi測ce試shi出chu有you電dian壓ya。因yin為wei電dian場chang通tong過guo互hu相xiang抵di消xiao,這zhe個ge球qiu外wai麵mian帶dai電dian,大da家jia都dou是shi靜jing電dian,磁ci力li線xian都dou是shi互hu相xiang抵di消xiao的de,電dian力li線xian互hu相xiang抵di消xiao,中zhong間jian的de電dian場chang強qiang度du等deng於yu零ling,所suo以yi就jiu不bu帶dai電dian。
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對於一些比較貴重的儀器、設(she)備(bei),在(zai)開(kai)關(guan)電(dian)容(rong)電(dian)壓(ya)器(qi)這(zhe)裏(li)最(zui)好(hao)做(zuo)靜(jing)電(dian)比(bi)例(li),在(zai)初(chu)次(ci)級(ji)線(xian)圈(quan)中(zhong)間(jian)做(zuo)一(yi)個(ge)鋁(lv)箔(bo)片(pian)都(dou)可(ke)以(yi),包(bao)一(yi)層(ceng),這(zhe)層(ceng)不(bu)能(neng)短(duan)路(lu),短(duan)路(lu)的(de)話(hua)變(bian)壓(ya)器(qi)就(jiu)會(hui)燒(shao)掉(diao),包(bao)在(zai)外(wai)麵(mian)可(ke)以(yi)短(duan)路(lu),包(bao)在(zai)裏(li)麵(mian)不(bu)能(neng)短(duan)路(lu),包(bao)在(zai)外(wai)麵(mian)吸(xi)收(shou)漏(lou)電(dian)電(dian)感(gan),包(bao)在(zai)裏(li)麵(mian)的(de)主(zhu)回(hui)路(lu)裏(li)麵(mian)會(hui)短(duan)路(lu),然(ran)後(hou)把(ba)它(ta)進(jin)行(xing)接(jie)地(di),這(zhe)相(xiang)當(dang)於(yu)可(ke)以(yi)隔(ge)離(li)掉(diao)。這(zhe)個(ge)有(you)一(yi)個(ge)教(jiao)訓(xun),前(qian)段(duan)時(shi)間(jian)康(kang)佳(jia)台(tai)灣(wan)裝(zhuang)LCD屏測試,打了一個隔離變壓器,後麵就是接測試儀表,每個月都有一台、兩(liang)台(tai)測(ce)試(shi)儀(yi)表(biao)損(sun)壞(huai),查(zha)不(bu)出(chu)原(yuan)因(yin),最(zui)後(hou)讓(rang)他(ta)們(men)把(ba)隔(ge)離(li)變(bian)壓(ya)器(qi)的(de)中(zhong)間(jian)屏(ping)蔽(bi)才(cai)好(hao)。屏(ping)蔽(bi)以(yi)後(hou),進(jin)一(yi)步(bu)有(you)機(ji)會(hui)的(de)話(hua),在(zai)接(jie)頭(tou)有(you)連(lian)接(jie)的(de)地(di)方(fang)加(jia)一(yi)個(ge)磁(ci)環(huan),讓(rang)共(gong)模(mo)電(dian)壓(ya)將(jiang)磁(ci)環(huan)速(su)度(du)放(fang)慢(man),緩(huan)衝(chong)一(yi)下(xia),讓(rang)瞬(shun)間(jian)能(neng)量(liang)降(jiang)低(di),瞬(shun)間(jian)能(neng)量(liang)緩(huan)慢(man)一(yi)點(dian),慢(man)慢(man)的(de)過(guo),損(sun)傷(shang)就(jiu)會(hui)少(shao)很(hen)多(duo)。所(suo)有(you)電(dian)路(lu)都(dou)可(ke)以(yi)把(ba)它(ta)看(kan)成(cheng)一(yi)個(ge)分(fen)布(bu)電(dian)流(liu),隻(zhi)要(yao)某(mou)地(di)方(fang)電(dian)壓(ya)電(dian)位(wei)在(zai)改(gai)變(bian),對(dui)後(hou)麵(mian)都(dou)會(hui)產(chan)生(sheng)充(chong)放(fang)電(dian),從(cong)這(zhe)上(shang)麵(mian)理(li)解(jie)就(jiu)知(zhi)道(dao)了(le),如(ru)果(guo)哪(na)個(ge)地(di)方(fang)構(gou)成(cheng)回(hui)路(lu),如(ru)果(guo)有(you)一(yi)個(ge)高(gao)電(dian)壓(ya)進(jin)來(lai)一(yi)直(zhi)傳(chuan)導(dao)到(dao)後(hou)麵(mian),最(zui)後(hou)充(chong)電(dian),充(chong)電(dian)可(ke)以(yi)理(li)解(jie)成(cheng)分(fen)布(bu)電(dian)容(rong),如(ru)果(guo)沒(mei)有(you)這(zhe)個(ge)也(ye)有(you)一(yi)個(ge)分(fen)布(bu)電(dian)容(rong)在(zai)裏(li)麵(mian),把(ba)分(fen)布(bu)電(dian)容(rong)放(fang)在(zai)這(zhe)裏(li),就(jiu)比(bi)較(jiao)形(xing)象(xiang)地(di)。就(jiu)像(xiang)以(yi)前(qian)的(de)絕(jue)緣(yuan)長(chang)效(xiao)濾(lv)管(guan)一(yi)樣(yang),手(shou)一(yi)摸(mo)沒(mei)有(you)造(zao)成(cheng)回(hui)路(lu)也(ye)壞(huai)掉(diao)了(le),絕(jue)緣(yuan)的(de)濾(lv)管(guan)很(hen)容(rong)易(yi)壞(huai),一(yi)從(cong)裏(li)麵(mian)拿(na)出(chu)來(lai),手(shou)一(yi)摸(mo)就(jiu)壞(huai)掉(diao),一(yi)個(ge)身(shen)上(shang)麵(mian)帶(dai)正(zheng)電(dian),或(huo)者(zhe)你(ni)作(zuo)為(wei)天(tian)線(xian)有(you)感(gan)應(ying)電(dian)壓(ya),感(gan)應(ying)一(yi)下(xia)來(lai)回(hui)充(chong)放(fang)電(dian)就(jiu)壞(huai)掉(diao)了(le)。
對於濾波電容,大家注意前麵的EMC濾lv波bo,這zhe個ge電dian容rong不bu是shi理li想xiang電dian容rong,裏li麵mian有you一yi個ge電dian感gan,還hai有you漏lou電dian電dian阻zu,裏li麵mian有you串chuan聯lian電dian阻zu,電dian感gan和he電dian容rong有you沒mei有you產chan生sheng串chuan聯lian諧xie振zhen?曲qu線xian是shi這zhe樣yang一yi條tiao斜xie線xian,串chuan聯lian諧xie振zhen相xiang當dang於yu把ba信xin號hao短duan路lu掉diao了le,信xin號hao短duan路lu的de阻zu礙ai很hen大da,這zhe裏li麵mian有you一yi個ge最zui佳jia值zhi,然ran後hou成cheng為wei感gan線xian,進jin行xingEMC電路設計的時候最好用不同的電容進行配模,這是0.4的曲線,33nFbinglianjiukeyibaozhengzaishangmianbushihaode,danduyigedianronghoumianfugaibudao,yihouyoujihuiwojiangzhexieyuanqijian,nimenzaidaxuelimianxuedeshifuhao,duidianzudianrongjibenshibudongde,haiyoudianzudianrongzhefangmiandewentizuiduo,haiyoudianrong,dianronglaihuijihuadeshihou,sudugenbushangwaimiandebianhua,huisunhaoxiangdangda,huishaohuai,tebieshimaiyadianrong,henduorenrenweitijiyuexiaoyuehao,danmeiyoukaolvzaikaiguanshangrongyichuxianwenti。

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這是網友提出的一些問題,我放在這裏。大家討論一下:
1、防雷是否一定要接地?對於感應雷而言,局部等電位連接是否可以取代接地,設備能否得到足夠的保護?
大(da)家(jia)想(xiang)想(xiang)看(kan),跟(gen)前(qian)麵(mian)我(wo)們(men)所(suo)說(shuo)的(de),感(gan)應(ying)雷(lei)這(zhe)個(ge)東(dong)西(xi)沒(mei)有(you)一(yi)個(ge)標(biao)準(zhun)的(de)概(gai)念(nian)說(shuo)什(shen)麼(me)叫(jiao)做(zuo)感(gan)應(ying)雷(lei)。隻(zhi)要(yao)打(da)雷(lei)的(de)話(hua),外(wai)麵(mian)打(da)雷(lei),窗(chuang)戶(hu)上(shang)麵(mian)的(de)金(jin)屬(shu),如(ru)果(guo)夜(ye)間(jian)都(dou)可(ke)以(yi)看(kan)到(dao)放(fang)電(dian)產(chan)生(sheng)火(huo)花(hua),這(zhe)就(jiu)是(shi)通(tong)過(guo)電(dian)磁(ci)感(gan)應(ying)產(chan)生(sheng)的(de)位(wei)移(yi)電(dian)流(liu)原(yuan)理(li)。從(cong)原(yuan)理(li)上(shang)來(lai)說(shuo),三(san)相(xiang)四(si)線(xian)或(huo)三(san)相(xiang)五(wu)線(xian),發(fa)電(dian)機(ji)有(you)中(zhong)線(xian)接(jie)地(di),設(she)備(bei)使(shi)用(yong)者(zhe)的(de)外(wai)殼(ke)接(jie)地(di)是(shi)最(zui)有(you)效(xiao)的(de)避(bi)雷(lei)方(fang)法(fa),但(dan)現(xian)在(zai)很(hen)多(duo)設(she)備(bei)都(dou)不(bu)接(jie)地(di),沒(mei)有(you)辦(ban)法(fa)接(jie),隻(zhi)有(you)很(hen)貴(gui)重(zhong)的(de)進(jin)口(kou)設(she)備(bei)用(yong)三(san)相(xiang)電(dian)源(yuan),中(zhong)間(jian)那(na)一(yi)條(tiao)地(di)線(xian),地(di)線(xian)不(bu)是(shi)中(zhong)線(xian),大(da)家(jia)要(yao)搞(gao)清(qing)楚(chu)。中(zhong)線(xian)雖(sui)然(ran)是(shi)接(jie)地(di)的(de),但(dan)在(zai)這(zhe)裏(li)不(bu)能(neng)當(dang)成(cheng)地(di)線(xian),地(di)線(xian)一(yi)定(ding)是(shi)自(zi)己(ji)大(da)樓(lou)本(ben)身(shen)的(de)地(di),而(er)且(qie)要(yao)量(liang)好(hao)接(jie)地(di)的(de)地(di)線(xian)。因(yin)為(wei)地(di)線(xian)接(jie)進(jin)去(qu)以(yi)後(hou),大(da)樓(lou)對(dui)外(wai)麵(mian)的(de)電(dian)磁(ci)層(ceng)進(jin)行(xing)屏(ping)蔽(bi)了(le),大(da)樓(lou)相(xiang)對(dui)來(lai)說(shuo)也(ye)是(shi)導(dao)電(dian)的(de),就(jiu)算(suan)不(bu)導(dao)電(dian),現(xian)在(zai)國(guo)家(jia)都(dou)有(you)安(an)全(quan)要(yao)求(qiu),大(da)樓(lou)超(chao)過(guo)多(duo)少(shao)層(ceng)都(dou)要(yao)加(jia)上(shang)避(bi)雷(lei)針(zhen),就(jiu)是(shi)防(fang)雷(lei)的(de)。如(ru)果(guo)不(bu)能(neng)接(jie)地(di),你(ni)就(jiu)要(yao)考(kao)慮(lv)充(chong)放(fang)電(dian)的(de)問(wen)題(ti)。前(qian)麵(mian)最(zui)好(hao)的(de)共(gong)模(mo)電(dian)容(rong)我(wo)覺(jiao)得(de)還(hai)是(shi)要(yao),我(wo)認(ren)為(wei)這(zhe)個(ge)共(gong)模(mo)電(dian)容(rong)最(zui)好(hao)連(lian)接(jie)上(shang),不(bu)能(neng)接(jie)大(da)地(di),要(yao)接(jie)在(zai)外(wai)殼(ke)上(shang),接(jie)到(dao)外(wai)殼(ke)上(shang)有(you)什(shen)麼(me)好(hao)處(chu)?共(gong)模(mo)電(dian)壓(ya)一(yi)進(jin)來(lai),雖(sui)然(ran)電(dian)流(liu)沒(mei)有(you)通(tong)過(guo)地(di)放(fang)電(dian)回(hui)路(lu),把(ba)電(dian)壓(ya)舉(ju)高(gao)起(qi)來(lai)了(le),與(yu)外(wai)麵(mian)輸(shu)入(ru)電(dian)壓(ya)是(shi)一(yi)樣(yang)的(de),外(wai)殼(ke)電(dian)壓(ya)取(qu)的(de)一(yi)樣(yang),起(qi)到(dao)了(le)屏(ping)蔽(bi)作(zuo)用(yong)。如(ru)果(guo)這(zhe)個(ge)接(jie)地(di)的(de)話(hua)會(hui)更(geng)加(jia)安(an)全(quan),但(dan)是(shi)地(di)線(xian)要(yao)足(zu)夠(gou)粗(cu),回(hui)路(lu)也(ye)足(zu)夠(gou),因(yin)為(wei)放(fang)電(dian)的(de)電(dian)流(liu)很(hen)大(da),很(hen)容(rong)易(yi)燒(shao)掉(diao)。這(zhe)幾(ji)個(ge)東(dong)西(xi)是(shi)經(jing)過(guo)很(hen)多(duo)年(nian)的(de)試(shi)驗(yan),8shihenchengshudedongxi,buguanzuogongmohaishifangleidouyaozuoshang,ruguolianjikedoumeiyou,zhishisuliaoke,yeyaokaolvzhegenxianjiedaoshenmeweizhizuihao?shijiedaolimianmianjizuidadedifang,jiushigonggongdimianjizuidadedifang,rangdianweijuqilai,qitadianweichabuhuichanshenghendadedianronghuilu。zhuyaoshikaolvchongfangdianhuilu,dianliuyuexiaoyuehao,lianggedianweichayuexiaoyuehao。
2、我wo們men是shi做zuo防fang雷lei模mo塊kuai的de,在zai實shi際ji應ying用yong中zhong,現xian場chang通tong常chang會hui碰peng到dao沒mei有you地di可ke接jie,這zhe時shi我wo們men首shou先xian建jian議yi客ke戶hu做zuo一yi個ge接jie地di係xi統tong,但dan如ru果guo因yin為wei造zao價jia或huo者zhe其qi他ta原yuan因yin確que實shi接jie地di有you困kun難nan,我wo們men建jian議yi客ke戶hu把ba防fang雷lei器qi的de地di和he其qi他ta設she備bei做zuo等deng電dian位wei連lian接jie後hou懸xuan浮fu,是shi否fou妥tuo當dang?
這(zhe)個(ge)防(fang)雷(lei)模(mo)塊(kuai)一(yi)般(ban)都(dou)是(shi)放(fang)電(dian)管(guan),一(yi)般(ban)在(zai)外(wai)麵(mian)賣(mai)的(de)都(dou)是(shi)壓(ya)敏(min)電(dian)阻(zu)或(huo)者(zhe)氣(qi)體(ti)放(fang)電(dian)管(guan),相(xiang)當(dang)於(yu)穩(wen)壓(ya)二(er)極(ji)管(guan)一(yi)樣(yang)的(de),比(bi)較(jiao)先(xian)進(jin)一(yi)點(dian)的(de)就(jiu)是(shi)與(yu)矽(gui)一(yi)樣(yang)的(de),就(jiu)是(shi)電(dian)壓(ya)超(chao)過(guo)多(duo)少(shao)的(de)時(shi)候(hou),壓(ya)敏(min)管(guan)就(jiu)導(dao)通(tong),或(huo)者(zhe)氣(qi)體(ti)放(fang)電(dian)管(guan),壓(ya)敏(min)電(dian)阻(zu)比(bi)較(jiao)便(bian)宜(yi),但(dan)是(shi)最(zui)不(bu)可(ke)靠(kao)的(de)。首(shou)先(xian)壓(ya)敏(min)電(dian)阻(zu)過(guo)壓(ya)衝(chong)擊(ji)的(de)時(shi)候(hou),壽(shou)命(ming)有(you)限(xian)的(de),隻(zhi)有(you)十(shi)幾(ji)次(ci)就(jiu)不(bu)能(neng)用(yong)了(le),壓(ya)敏(min)電(dian)阻(zu)是(shi)一(yi)堆(dui)亂(luan)七(qi)八(ba)糟(zao)的(de)二(er)極(ji)管(guan)在(zai)裏(li)麵(mian)互(hu)相(xiang)接(jie)觸(chu),就(jiu)是(shi)兩(liang)個(ge)不(bu)同(tong)金(jin)屬(shu)氧(yang)化(hua)物(wu)之(zhi)間(jian)互(hu)相(xiang)接(jie)觸(chu)相(xiang)當(dang)於(yu)一(yi)個(ge)二(er)極(ji)管(guan),以(yi)前(qian)我(wo)們(men)用(yong)礦(kuang)石(shi)收(shou)音(yin)機(ji)或(huo)者(zhe)用(yong)礦(kuang)石(shi)整(zheng)流(liu),就(jiu)是(shi)拿(na)兩(liang)塊(kuai)氧(yang)化(hua)銅(tong)或(huo)者(zhe)氧(yang)化(hua)礦(kuang)石(shi)連(lian)接(jie)以(yi)後(hou)就(jiu)可(ke)以(yi)當(dang)成(cheng)整(zheng)流(liu)二(er)極(ji)管(guan)使(shi)用(yong),原(yuan)理(li)是(shi)一(yi)樣(yang)的(de),裏(li)麵(mian)一(yi)大(da)堆(dui)氧(yang)化(hua)鉛(qian),每(mei)個(ge)界(jie)麵(mian)都(dou)相(xiang)同(tong),相(xiang)當(dang)於(yu)一(yi)個(ge)二(er)極(ji)管(guan),二(er)極(ji)管(guan)有(you)一(yi)個(ge)耐(nai)壓(ya),通(tong)過(guo)裏(li)麵(mian)來(lai)控(kong)製(zhi)耐(nai)壓(ya)的(de)參(can)數(shu)。這(zhe)種(zhong)一(yi)次(ci)擊(ji)穿(chuan)以(yi)後(hou)二(er)極(ji)管(guan)壞(huai)掉(diao)了(le),選(xuan)另(ling)外(wai)一(yi)個(ge)渠(qu)道(dao)。二(er)極(ji)管(guan)都(dou)是(shi)哪(na)個(ge)電(dian)壓(ya)高(gao)擊(ji)就(jiu)穿(chuan)哪(na)一(yi)個(ge),另(ling)外(wai)一(yi)個(ge)低(di)的(de)就(jiu)不(bu)擊(ji)穿(chuan),哪(na)個(ge)電(dian)壓(ya)高(gao)就(jiu)損(sun)壞(huai)那(na)一(yi)個(ge),然(ran)後(hou)再(zai)損(sun)壞(huai)另(ling)外(wai)一(yi)個(ge),最(zui)多(duo)隻(zhi)能(neng)損(sun)十(shi)幾(ji)次(ci),壓(ya)敏(min)電(dian)阻(zu)就(jiu)壞(huai)了(le)。用(yong)普(pu)通(tong)穩(wen)壓(ya)二(er)極(ji)管(guan)功(gong)率(lv)不(bu)夠(gou),分(fen)布(bu)電(dian)容(rong)比(bi)較(jiao)大(da)。用(yong)空(kong)氣(qi)的(de)話(hua)相(xiang)對(dui)放(fang)電(dian)管(guan)恢(hui)複(fu)時(shi)間(jian)很(hen)長(chang),點(dian)火(huo)時(shi)間(jian)也(ye)長(chang),導(dao)通(tong)時(shi)間(jian)很(hen)長(chang),恢(hui)複(fu)時(shi)間(jian)很(hen)長(chang),對(dui)於(yu)高(gao)速(su)的(de)保(bao)護(hu)來(lai)不(bu)及(ji)。比(bi)如(ru)說(shuo)作(zuo)為(wei)傳(chuan)輸(shu)線(xian)之(zhi)類(lei)的(de)保(bao)護(hu)是(shi)不(bu)行(xing)的(de),過(guo)壓(ya)以(yi)後(hou)一(yi)導(dao)通(tong)了(le),導(dao)致(zhi)長(chang)時(shi)間(jian)難(nan)以(yi)恢(hui)複(fu)。防(fang)雷(lei)模(mo)塊(kuai)我(wo)建(jian)議(yi)用(yong)在(zai)最(zui)後(hou)麵(mian),就(jiu)是(shi)作(zuo)為(wei)後(hou)備(bei)來(lai)使(shi)用(yong),就(jiu)是(shi)在(zai)IC輸(shu)入(ru)角(jiao)可(ke)以(yi)接(jie)輸(shu)入(ru)輸(shu)出(chu)接(jie)口(kou)的(de)位(wei)置(zhi),在(zai)電(dian)源(yuan)輸(shu)入(ru)的(de)地(di)方(fang)絕(jue)對(dui)不(bu)能(neng)用(yong),一(yi)個(ge)是(shi)用(yong)上(shang)去(qu)沒(mei)有(you)效(xiao),另(ling)外(wai)成(cheng)本(ben)很(hen)高(gao),作(zuo)為(wei)輸(shu)入(ru)端(duan)用(yong)人(ren)工(gong)排(pai)一(yi)個(ge)放(fang)電(dian)裝(zhuang)置(zhi),在(zai)後(hou)麵(mian)再(zai)加(jia)上(shang)防(fang)雷(lei)模(mo)塊(kuai),互(hu)相(xiang)組(zu)合(he)起(qi)來(lai)使(shi)用(yong)。
3、關於EMI電磁幹擾,我們的防雷元器件是否能夠奏效?還是主要依靠設計、合理布局更有效?
按照道理EMI是電磁幹擾,避雷元器件按照道理並不聯係在一起,但EMC濾波裏麵,與EMC濾波器同樣有防雷功能,就是前麵的幾個電感和共模電容還有差模電容對防雷都起到作用,大家要理解,EMC濾lv波bo是shi用yong於yu設she備bei上shang的de,但dan反fan過guo來lai考kao慮lv雷lei電dian的de時shi候hou,你ni就jiu要yao把ba幹gan擾rao信xin號hao從cong外wai麵mian輸shu進jin來lai,要yao這zhe樣yang考kao慮lv了le,不bu能neng單dan方fang麵mian,最zui好hao在zai防fang雷lei加jia上shang一yi個ge放fang電dian裝zhuang置zhi加jia在zai電dian感gan後hou麵mian,共gong用yong共gong模mo濾lv波bo電dian容rong。
4、ESD在PCB設計中應注意的事項有哪些?
ESD一般除了防雷以外,還有一些別的相關內容,裏麵有一些IC很容易受到周邊電壓比較高的器件幹擾或損壞,比如說在電視機裏麵,電視機裏麵的高壓包產生的高壓是上萬的,裏麵的CPUdengmoshidianlunijueduibunengkaojingaoyadianyuanbufen,bixuyuanlita。yiqianwomenshiguo,doushiyinweiyugaoyabaokaodetaijinle,balimiandeqidongqiganrao,balimiandeshujudaluan,womenzhishizaishangmiantieleyikuaishibopian,zuikaishishiguolvzuixiangyanlimianyoushibopian,womenconglajiduilimianjianlai,yingjichuliwangshangmiantie,rangxiulibuzheyanglaiyingfuchuli。manmanwomenduizhegedongxirenshihenqingchule,xianzaihenduojichengdianlucaiquzhezhongfangshi,youdezaishangmiandaiyigesanrepian,benshenkeyizuopingbi,huozhezaishangmiantieyigejiaozhi,jiaozhiyoudaodiandezuoyong,keyifangshangqu,zheshiESD方fang麵mian的de防fang護hu方fang法fa。因yin為wei貼tie了le一yi塊kuai以yi後hou,哪na怕pa電dian離li層ceng很hen高gao的de打da下xia去qu都dou不bu會hui擊ji壞huai,所suo以yi在zai貴gui重zhong集ji成cheng電dian路lu裏li麵mian,在zai電dian路lu板ban上shang麵mian貼tie一yi塊kuai有you一yi邊bian絕jue緣yuan的de,兩liang邊bian的de絕jue緣yuan都dou是shi零ling,但dan是shi有you一yi塊kuai示shi波bo片pian,外wai麵mian都dou有you賣mai,非fei常chang方fang便bian。現xian在zai電dian視shi機ji裏li麵mian都dou大da量liang采cai用yong這zhe種zhong技ji術shu。對dui於yu排pai線xian的de輸shu入ru輸shu出chu線xian、xinhaoxiandoushikaodeyuejinyuehao,lianggenxianyidingyaozhaochulainageshishuru,nageshishuchu,dianliuliujinquhaishiliuchulaide,xiankaojindeyuejinyuehao,limiandemianjiyuesuoxiaoyuehao,ruguodianliuhenxiao,xinhaogonglvhenxiao,jinliangyongxiaoerbushiyongda,ruguodalefenbudianrongyeda,fenbudianrongdadeyihourongyijieshoudianziganraohedianrongsunhuai,limiandechangxiaoguanyongyanjingkanbudao,yongfangdajingfangdajibaibeiyeshikanbudaode,yinxiankeyikandao,limianyinxiandedianrongxiangduilaishuogaohenduo,jieyidiandianzhengdianjinquyihoujichuanle,suoyilimiandedaoxianyueduanyuehao。jichengdianludeshurushuchudouyiban,jialeyigeerjiguan,jiushiyudianrongjiezaiyiqi,benshenzaidianlulimiandouyoubaohuzuoyong,ruguomeiyoujiedaodianlulimianyongshouqumoshihuaidiaode,jiedaolimianyouxinhaozuoyonglejiubuhuihuai。
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5、在射頻電路中,敏感線路(如數據線等)如何保護?
shujuxiandajiadouyijingyouhenduofangfa,yibanshujuxianzuihaoyongchafen,jianglianggenxianniuzaiyiqi,niuzaiyiqiyihouyigeliujinqu,yigeliuchulai,shuangjiaozaiyiqi,waimianjiayicengpingbixian,waimianzhiyouyitiaojiedi,buyaoliangtiaodoujie,jieyitoujiukeyile,shuangjiaoxianduidianziganraohuxiangdixiao,tongyigefangxiangliuchulaidedianliuchanshengdefangxiangzhenghaoxiangfan,huxiangdixiao,chafenshizuihaode,buyaojiedaogonggongdishang,yongchafen。henjiandan,zhegexianjiayigecihuan,liangduandoujiayigecihuan,zhegecihuanduichamoyouxiangdangdengyuling,liuguodexinhaoyigeshichamoxinhao,ganraoxinhaodabufenshigongmode,jiashangdianganshangmianduigongmohenyouxiao,ESD放電基本上都是共模,加載上麵對ESD起qi到dao保bao護hu作zuo用yong。充chong放fang電dian加jia一yi個ge小xiao磁ci環huan,如ru果guo沒mei有you小xiao磁ci環huan,用yong適shi配pei器qi往wang插cha頭tou上shang一yi插cha,瞬shun間jian選xuan擇ze突tu然ran充chong電dian會hui有you損sun壞huai,不bu要yao輕qing易yi把ba磁ci環huan去qu掉diao,那na就jiu是shi讓rang你ni對dui充chong放fang電dian抑yi製zhi速su度du的de降jiang慢man。
6、IC引腳的靜電防護,加什麼器件既經濟又有效?
如果不考慮速度,最好是在輸入端加一個電阻,靠近IC加一個電容,這隻有幾十PU加大,如果信號頻率很高,盡量想辦法把信號線的阻耗降低,不要搞得很高。現在一般的信號線,高頻都是50歐姆,兩個之間接一個75安培或50安培的,把阻礙降低,直衝放電就是兩個電位。75歐姆以上,一根線上麵加的1v電壓上去,流過的電流多大?或者說一個毫安的電流在上麵的電壓也很小,因為ESD放電的電壓很高,電流很小,放電電壓馬上掉下來,不會衝擊到集成電路裏麵去。所以在要求不是特別高上麵,盡量把輸入降低。
7、ESD防護器件什麼時候應該放在端口處,什麼時候該放在芯片管角?
保bao護hu單dan個ge集ji成cheng電dian路lu就jiu放fang在zai集ji成cheng電dian路lu的de地di方fang最zui好hao,如ru果guo保bao護hu整zheng個ge設she備bei就jiu放fang在zai端duan口kou。放fang在zai集ji成cheng電dian路lu這zhe個ge地di方fang,後hou麵mian那na一yi段duan照zhao樣yang有you電dian壓ya可ke以yi感gan應ying到dao別bie的deIC上,對別的IC會產生損壞,所以你要保護好IC,就在IC加上ESD的保護,如果對整個設備進行保護的話,所有的接口都加ESD保護就足夠了,這個成本是最低的。因為你把數據輸出、輸入接一個保護,裏麵本身不會產生ESD放電,如果裏麵產生ESD放電早不能過關,ESD放(fang)電(dian)肯(ken)定(ding)從(cong)外(wai)麵(mian)進(jin)去(qu)的(de),把(ba)所(suo)有(you)的(de)口(kou)都(dou)封(feng)住(zhu)就(jiu)不(bu)會(hui)有(you)問(wen)題(ti)。所(suo)以(yi),我(wo)建(jian)議(yi)你(ni)如(ru)果(guo)從(cong)設(she)備(bei)考(kao)慮(lv),從(cong)成(cheng)本(ben)考(kao)慮(lv)就(jiu)接(jie)輸(shu)入(ru)輸(shu)出(chu)口(kou)的(de)地(di)方(fang),為(wei)了(le)保(bao)護(hu)集(ji)成(cheng)電(dian)路(lu),對(dui)其(qi)他(ta)不(bu)管(guan)的(de)話(hua)就(jiu)接(jie)在(zai)集(ji)成(cheng)電(dian)路(lu)上(shang)。

雷(lei)電(dian)的(de)原(yuan)理(li)就(jiu)是(shi)這(zhe)樣(yang),這(zhe)一(yi)塊(kuai)是(shi)帶(dai)電(dian)的(de),降(jiang)到(dao)這(zhe)兩(liang)根(gen)線(xian)上(shang)麵(mian)去(qu)。對(dui)地(di)球(qiu)來(lai)說(shuo)相(xiang)當(dang)於(yu)一(yi)個(ge)分(fen)布(bu)電(dian)容(rong),雷(lei)電(dian)就(jiu)是(shi)一(yi)個(ge)共(gong)模(mo)信(xin)號(hao),相(xiang)當(dang)於(yu)對(dui)整(zheng)個(ge)電(dian)容(rong)進(jin)行(xing)放(fang)電(dian)。放(fang)電(dian)有(you)幾(ji)個(ge)回(hui)路(lu),上(shang)麵(mian)的(de)電(dian)流(liu)通(tong)過(guo)電(dian)容(rong)到(dao)達(da)地(di),電(dian)流(liu)通(tong)過(guo)電(dian)容(rong)到(dao)大(da)地(di),這(zhe)是(shi)共(gong)模(mo)電(dian)容(rong)。這(zhe)部(bu)分(fen)電(dian)流(liu)也(ye)通(tong)過(guo)電(dian)容(rong)下(xia)地(di),還(hai)有(you)一(yi)部(bu)分(fen)通(tong)過(guo)變(bian)壓(ya)器(qi)分(fen)布(bu)電(dian)容(rong)傳(chuan)到(dao)負(fu)載(zai)這(zhe)邊(bian),然(ran)後(hou)通(tong)過(guo)分(fen)布(bu)電(dian)容(rong)下(xia)地(di)。你(ni)可(ke)以(yi)認(ren)為(wei)這(zhe)個(ge)電(dian)容(rong)是(shi)大(da)地(di)的(de)分(fen)布(bu)電(dian)容(rong),實(shi)際(ji)上(shang)不(bu)跟(gen)大(da)地(di)它(ta)本(ben)身(shen)也(ye)是(shi)分(fen)布(bu)電(dian)容(rong),任(ren)何(he)一(yi)個(ge)導(dao)體(ti)隻(zhi)要(yao)電(dian)位(wei)改(gai)變(bian)就(jiu)相(xiang)當(dang)於(yu)一(yi)個(ge)電(dian)容(rong),比(bi)如(ru)說(shuo)你(ni)的(de)身(shen)體(ti)帶(dai)電(dian),另(ling)外(wai)一(yi)個(ge)不(bu)帶(dai)電(dian),兩(liang)個(ge)人(ren)握(wo)手(shou)就(jiu)會(hui)把(ba)電(dian)荷(he)傳(chuan)到(dao)另(ling)外(wai)一(yi)個(ge)人(ren)身(shen)上(shang),相(xiang)當(dang)於(yu)你(ni)這(zhe)個(ge)電(dian)容(rong)對(dui)另(ling)外(wai)一(yi)個(ge)電(dian)容(rong)放(fang)電(dian),另(ling)外(wai)一(yi)個(ge)相(xiang)對(dui)來(lai)說(shuo)是(shi)充(chong)電(dian),是(shi)一(yi)個(ge)充(chong)放(fang)電(dian)的(de)過(guo)程(cheng)。


除了共模電流以外,還有一個差模電流,為什麼?兩個回路都放電的時候,放電的時間、強(qiang)度(du)不(bu)一(yi)樣(yang),有(you)的(de)放(fang)快(kuai)一(yi)點(dian),有(you)的(de)放(fang)慢(man)一(yi)點(dian),如(ru)果(guo)兩(liang)個(ge)東(dong)西(xi)的(de)速(su)度(du)都(dou)一(yi)樣(yang),任(ren)何(he)電(dian)位(wei)差(cha)都(dou)是(shi)一(yi)樣(yang)的(de)就(jiu)不(bu)會(hui)產(chan)生(sheng)差(cha)模(mo)電(dian)流(liu)了(le)。但(dan)是(shi)有(you)時(shi)候(hou)有(you)一(yi)些(xie)是(shi)中(zhong)線(xian)接(jie)地(di),放(fang)電(dian)快(kuai)一(yi)些(xie),相(xiang)對(dui)來(lai)說(shuo)電(dian)壓(ya)跌(die)得(de)特(te)別(bie)快(kuai),另(ling)外(wai)一(yi)個(ge)跌(die)得(de)特(te)別(bie)慢(man),就(jiu)會(hui)產(chan)生(sheng)差(cha)模(mo),首(shou)先(xian)是(shi)共(gong)模(mo),然(ran)後(hou)產(chan)生(sheng)差(cha)模(mo)。
下(xia)麵(mian)講(jiang)一(yi)下(xia)共(gong)模(mo)電(dian)壓(ya)對(dui)電(dian)路(lu)的(de)損(sun)害(hai)。其(qi)實(shi)共(gong)模(mo)電(dian)壓(ya)對(dui)開(kai)關(guan)電(dian)容(rong)前(qian)麵(mian)的(de)影(ying)響(xiang)不(bu)是(shi)很(hen)大(da),最(zui)大(da)是(shi)後(hou)麵(mian)一(yi)點(dian),通(tong)過(guo)電(dian)壓(ya)器(qi)分(fen)布(bu)電(dian)路(lu),以(yi)前(qian)的(de)模(mo)式(shi)電(dian)路(lu)電(dian)壓(ya)用(yong)得(de)很(hen)低(di),都(dou)是(shi)1v-5vzuoyou,namijirongyijichuan,dianrongyexiangdangxiao。conglimianchuanjinqudedianyajingguolvbobuduandexishoujiangxialai,yibanyoushangqianfu,rongyibahoumiandejichuan。zaishijianguochengzhongweilefanglei,zhejigeweizhizuihaozaishangmianbuyigeleidiandianrong,duifangleidianjichuanhenyouxiao。gongmodianyajinquyihoushunjianjichuan,ruguodianzimeiduankai,waimiandedianliuhuijixuyanxuxiaqubatashaodiao,ruguobeiyigedianrongshangqu,gongmodianrongtongguodianrongyixiazibataxishoudiao,rangjigedianronghuxiangtongdianwei,jigemozubuhuinamerongyijichuan。


剛gang才cai在zai休xiu息xi的de時shi候hou與yu大da家jia交jiao流liu,大da家jia真zhen的de很hen感gan興xing趣qu,熱re情qing也ye相xiang當dang高gao,我wo也ye希xi望wang大da家jia通tong過guo這zhe個ge機ji會hui互hu相xiang認ren識shi,多duo多duo交jiao流liu,特te別bie是shi這zhe些xie經jing驗yan之zhi談tan在zai書shu上shang是shi很hen難nan找zhao到dao的de。如ru果guo還hai要yao有you更geng深shen的de研yan究jiu,我wo建jian議yi你ni有you機ji會hui去qu歐ou洲zhou最zui大da的de物wu理li研yan究jiu所suo,現xian在zai研yan究jiu的de課ke題ti與yu此ci相xiang關guan,就jiu是shi電dian磁ci層ceng理li論lun,現xian在zai空kong間jian物wu理li也ye好hao,電dian磁ci層ceng理li論lun是shi最zui難nan解jie決jue的de問wen題ti,現xian在zai有you四si個ge力li,如ru果guo能neng夠gou把ba四si個ge力li統tong一yi起qi來lai,宇yu宙zhou空kong間jian的de問wen題ti基ji本ben上shang都dou可ke以yi解jie答da。一yi個ge是shi重zhong力li,原yuan來lai無wu法fa解jie釋shi重zhong力li如ru何he產chan生sheng,就jiu有you重zhong力li層ceng。還hai有you電dian場chang力li,無wu法fa解jie釋shi這zhe個ge怎zen麼me產chan生sheng,就jiu有you電dian場chang力li,還hai有you磁ci場chang力li、合he力li,如ru果guo四si個ge力li統tong一yi在zai一yi起qi就jiu可ke以yi解jie決jue。在zai書shu上shang介jie紹shao電dian磁ci層ceng,一yi點dian點dian東dong西xi都dou全quan部bu解jie決jue了le,包bao括kuo量liang綱gang都dou沒mei有you統tong一yi,大da家jia都dou在zai爭zheng論lun,電dian場chang強qiang度du和he磁ci場chang強qiang度du的de量liang綱gang都dou沒mei有you解jie決jue。按an照zhao電dian場chang的de強qiang度du,原yuan來lai牛niu頓dun用yong力li表biao示shi,這zhe個ge東dong西xi與yu現xian在zai電dian工gong學xue不bu搭da架jia了le。特te別bie是shi電dian流liu強qiang度du通tong過guo兩liang根gen導dao線xian多duo少shao,直zhi徑jing多duo大da、dianliuduodalailiangli,zhezhongcichangqiangduduiwomenshiyongyouduodaguanxi?dangchudingxialaiyoubuhaotuifan,xianzaimanmanyinjinleciganyingqiangdu,bacichangqiangdupingbidiaole,zaidianyajisuanlidajiadouzhidaociganyinglidu,haiyoudianchangqiangdumanmanyepingbidiaole,jiushiyongdianweitidu。
下(xia)麵(mian)我(wo)們(men)講(jiang)一(yi)些(xie)具(ju)體(ti)的(de)。這(zhe)是(shi)一(yi)個(ge)開(kai)關(guan)電(dian)源(yuan),開(kai)關(guan)電(dian)源(yuan)被(bei)雷(lei)劈(pi)的(de)時(shi)候(hou),輸(shu)入(ru)回(hui)路(lu)基(ji)本(ben)上(shang)都(dou)燒(shao)了(le),假(jia)如(ru)沒(mei)燒(shao)是(shi)什(shen)麼(me)樣(yang)的(de)?可(ke)以(yi)看(kan)看(kan),這(zhe)是(shi)橋(qiao)堆(dui),這(zhe)兩(liang)個(ge)是(shi)Ydianrong,zhelimianhaiyouyigeyamindianzu。zheshigongmoxianquan,leipiyihouquanbushaole,shuomingyamindianzumeiyouqidaoshenmebaohuzuoyong,lianggedianrongdoushaole,shuomingdianganxiangdang、相(xiang)當(dang)地(di)高(gao)。為(wei)了(le)防(fang)止(zhi)雷(lei)電(dian),首(shou)先(xian)前(qian)麵(mian)一(yi)定(ding)要(yao)加(jia)一(yi)個(ge)能(neng)量(liang)吸(xi)收(shou),比(bi)較(jiao)大(da)的(de)東(dong)西(xi),成(cheng)本(ben)相(xiang)對(dui)來(lai)說(shuo)比(bi)較(jiao)低(di),像(xiang)試(shi)驗(yan)站(zhan)裏(li)麵(mian)的(de)放(fang)電(dian)裝(zhuang)置(zhi),那(na)個(ge)東(dong)西(xi)沒(mei)有(you)地(di)方(fang)裝(zhuang),也(ye)貴(gui)得(de)很(hen)。在(zai)硬(ying)紙(zhi)板(ban)上(shang)麵(mian)排(pai)幾(ji)個(ge)鋸(ju)齒(chi),中(zhong)間(jian)隔(ge)一(yi)個(ge)頭(tou)就(jiu)行(xing)了(le)。如(ru)果(guo)中(zhong)間(jian)隔(ge)6mm也可以。有一個一級電感,電感可以使瞬間上去很快的電壓降下來,突然加一個1萬伏、10萬wan伏fu,加jia上shang去qu隻zhi有you這zhe兩liang端duan,另ling外wai兩liang端duan建jian立li不bu起qi來lai,所suo以yi剛gang加jia進jin去qu的de時shi候hou對dui雷lei電dian來lai說shuo,大da部bu分fen能neng量liang都dou被bei吸xi收shou掉diao了le。後hou麵mian經jing過guo這zhe個ge以yi後hou,剩sheng餘yu部bu分fen通tong過guo共gong膜mo電dian容rong繼ji續xu吸xi收shou,吸xi收shou完wan以yi後hou還hai有you差cha模mo部bu分fen,產chan生sheng的de差cha模mo部bu分fen通tong過guo電dian容rong把ba差cha模mo吸xi收shou掉diao。共gong模mo電dian容rong和he差cha模mo電dian容rong具ju有you抑yi製zhi傳chuan導dao幹gan擾rao的de作zuo用yong,對dui雷lei電dian也ye有you抑yi製zhi作zuo用yong,所suo以yi很hen多duo人ren也ye在zai問wen,電dian容rong接jie到dao前qian麵mian好hao還hai是shi接jie在zai後hou麵mian好hao?這zhe個ge東dong西xi看kan你ni有you什shen麼me作zuo用yong,如ru果guo隻zhi是shi為wei了le防fangEMI電(dian)磁(ci)幹(gan)擾(rao)的(de)話(hua),接(jie)在(zai)越(yue)前(qian)麵(mian)越(yue)好(hao),接(jie)在(zai)測(ce)試(shi)儀(yi)表(biao)的(de)輸(shu)入(ru)端(duan)最(zui)好(hao),接(jie)到(dao)那(na)裏(li)把(ba)信(xin)號(hao)全(quan)部(bu)短(duan)路(lu)掉(diao)了(le),就(jiu)看(kan)不(bu)到(dao)了(le)。但(dan)是(shi)對(dui)於(yu)雷(lei)電(dian),你(ni)接(jie)到(dao)後(hou)麵(mian)要(yao)好(hao)很(hen)多(duo),所(suo)以(yi)這(zhe)主(zhu)要(yao)是(shi)防(fang)雷(lei)的(de),你(ni)就(jiu)不(bu)要(yao)考(kao)慮(lv)電(dian)磁(ci)幹(gan)擾(rao)和(he)EMC了,盡量把兩個放在後麵。


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對於一些比較貴重的儀器、設(she)備(bei),在(zai)開(kai)關(guan)電(dian)容(rong)電(dian)壓(ya)器(qi)這(zhe)裏(li)最(zui)好(hao)做(zuo)靜(jing)電(dian)比(bi)例(li),在(zai)初(chu)次(ci)級(ji)線(xian)圈(quan)中(zhong)間(jian)做(zuo)一(yi)個(ge)鋁(lv)箔(bo)片(pian)都(dou)可(ke)以(yi),包(bao)一(yi)層(ceng),這(zhe)層(ceng)不(bu)能(neng)短(duan)路(lu),短(duan)路(lu)的(de)話(hua)變(bian)壓(ya)器(qi)就(jiu)會(hui)燒(shao)掉(diao),包(bao)在(zai)外(wai)麵(mian)可(ke)以(yi)短(duan)路(lu),包(bao)在(zai)裏(li)麵(mian)不(bu)能(neng)短(duan)路(lu),包(bao)在(zai)外(wai)麵(mian)吸(xi)收(shou)漏(lou)電(dian)電(dian)感(gan),包(bao)在(zai)裏(li)麵(mian)的(de)主(zhu)回(hui)路(lu)裏(li)麵(mian)會(hui)短(duan)路(lu),然(ran)後(hou)把(ba)它(ta)進(jin)行(xing)接(jie)地(di),這(zhe)相(xiang)當(dang)於(yu)可(ke)以(yi)隔(ge)離(li)掉(diao)。這(zhe)個(ge)有(you)一(yi)個(ge)教(jiao)訓(xun),前(qian)段(duan)時(shi)間(jian)康(kang)佳(jia)台(tai)灣(wan)裝(zhuang)LCD屏測試,打了一個隔離變壓器,後麵就是接測試儀表,每個月都有一台、兩(liang)台(tai)測(ce)試(shi)儀(yi)表(biao)損(sun)壞(huai),查(zha)不(bu)出(chu)原(yuan)因(yin),最(zui)後(hou)讓(rang)他(ta)們(men)把(ba)隔(ge)離(li)變(bian)壓(ya)器(qi)的(de)中(zhong)間(jian)屏(ping)蔽(bi)才(cai)好(hao)。屏(ping)蔽(bi)以(yi)後(hou),進(jin)一(yi)步(bu)有(you)機(ji)會(hui)的(de)話(hua),在(zai)接(jie)頭(tou)有(you)連(lian)接(jie)的(de)地(di)方(fang)加(jia)一(yi)個(ge)磁(ci)環(huan),讓(rang)共(gong)模(mo)電(dian)壓(ya)將(jiang)磁(ci)環(huan)速(su)度(du)放(fang)慢(man),緩(huan)衝(chong)一(yi)下(xia),讓(rang)瞬(shun)間(jian)能(neng)量(liang)降(jiang)低(di),瞬(shun)間(jian)能(neng)量(liang)緩(huan)慢(man)一(yi)點(dian),慢(man)慢(man)的(de)過(guo),損(sun)傷(shang)就(jiu)會(hui)少(shao)很(hen)多(duo)。所(suo)有(you)電(dian)路(lu)都(dou)可(ke)以(yi)把(ba)它(ta)看(kan)成(cheng)一(yi)個(ge)分(fen)布(bu)電(dian)流(liu),隻(zhi)要(yao)某(mou)地(di)方(fang)電(dian)壓(ya)電(dian)位(wei)在(zai)改(gai)變(bian),對(dui)後(hou)麵(mian)都(dou)會(hui)產(chan)生(sheng)充(chong)放(fang)電(dian),從(cong)這(zhe)上(shang)麵(mian)理(li)解(jie)就(jiu)知(zhi)道(dao)了(le),如(ru)果(guo)哪(na)個(ge)地(di)方(fang)構(gou)成(cheng)回(hui)路(lu),如(ru)果(guo)有(you)一(yi)個(ge)高(gao)電(dian)壓(ya)進(jin)來(lai)一(yi)直(zhi)傳(chuan)導(dao)到(dao)後(hou)麵(mian),最(zui)後(hou)充(chong)電(dian),充(chong)電(dian)可(ke)以(yi)理(li)解(jie)成(cheng)分(fen)布(bu)電(dian)容(rong),如(ru)果(guo)沒(mei)有(you)這(zhe)個(ge)也(ye)有(you)一(yi)個(ge)分(fen)布(bu)電(dian)容(rong)在(zai)裏(li)麵(mian),把(ba)分(fen)布(bu)電(dian)容(rong)放(fang)在(zai)這(zhe)裏(li),就(jiu)比(bi)較(jiao)形(xing)象(xiang)地(di)。就(jiu)像(xiang)以(yi)前(qian)的(de)絕(jue)緣(yuan)長(chang)效(xiao)濾(lv)管(guan)一(yi)樣(yang),手(shou)一(yi)摸(mo)沒(mei)有(you)造(zao)成(cheng)回(hui)路(lu)也(ye)壞(huai)掉(diao)了(le),絕(jue)緣(yuan)的(de)濾(lv)管(guan)很(hen)容(rong)易(yi)壞(huai),一(yi)從(cong)裏(li)麵(mian)拿(na)出(chu)來(lai),手(shou)一(yi)摸(mo)就(jiu)壞(huai)掉(diao),一(yi)個(ge)身(shen)上(shang)麵(mian)帶(dai)正(zheng)電(dian),或(huo)者(zhe)你(ni)作(zuo)為(wei)天(tian)線(xian)有(you)感(gan)應(ying)電(dian)壓(ya),感(gan)應(ying)一(yi)下(xia)來(lai)回(hui)充(chong)放(fang)電(dian)就(jiu)壞(huai)掉(diao)了(le)。
對於濾波電容,大家注意前麵的EMC濾lv波bo,這zhe個ge電dian容rong不bu是shi理li想xiang電dian容rong,裏li麵mian有you一yi個ge電dian感gan,還hai有you漏lou電dian電dian阻zu,裏li麵mian有you串chuan聯lian電dian阻zu,電dian感gan和he電dian容rong有you沒mei有you產chan生sheng串chuan聯lian諧xie振zhen?曲qu線xian是shi這zhe樣yang一yi條tiao斜xie線xian,串chuan聯lian諧xie振zhen相xiang當dang於yu把ba信xin號hao短duan路lu掉diao了le,信xin號hao短duan路lu的de阻zu礙ai很hen大da,這zhe裏li麵mian有you一yi個ge最zui佳jia值zhi,然ran後hou成cheng為wei感gan線xian,進jin行xingEMC電路設計的時候最好用不同的電容進行配模,這是0.4的曲線,33nFbinglianjiukeyibaozhengzaishangmianbushihaode,danduyigedianronghoumianfugaibudao,yihouyoujihuiwojiangzhexieyuanqijian,nimenzaidaxuelimianxuedeshifuhao,duidianzudianrongjibenshibudongde,haiyoudianzudianrongzhefangmiandewentizuiduo,haiyoudianrong,dianronglaihuijihuadeshihou,sudugenbushangwaimiandebianhua,huisunhaoxiangdangda,huishaohuai,tebieshimaiyadianrong,henduorenrenweitijiyuexiaoyuehao,danmeiyoukaolvzaikaiguanshangrongyichuxianwenti。



這是網友提出的一些問題,我放在這裏。大家討論一下:
1、防雷是否一定要接地?對於感應雷而言,局部等電位連接是否可以取代接地,設備能否得到足夠的保護?
大(da)家(jia)想(xiang)想(xiang)看(kan),跟(gen)前(qian)麵(mian)我(wo)們(men)所(suo)說(shuo)的(de),感(gan)應(ying)雷(lei)這(zhe)個(ge)東(dong)西(xi)沒(mei)有(you)一(yi)個(ge)標(biao)準(zhun)的(de)概(gai)念(nian)說(shuo)什(shen)麼(me)叫(jiao)做(zuo)感(gan)應(ying)雷(lei)。隻(zhi)要(yao)打(da)雷(lei)的(de)話(hua),外(wai)麵(mian)打(da)雷(lei),窗(chuang)戶(hu)上(shang)麵(mian)的(de)金(jin)屬(shu),如(ru)果(guo)夜(ye)間(jian)都(dou)可(ke)以(yi)看(kan)到(dao)放(fang)電(dian)產(chan)生(sheng)火(huo)花(hua),這(zhe)就(jiu)是(shi)通(tong)過(guo)電(dian)磁(ci)感(gan)應(ying)產(chan)生(sheng)的(de)位(wei)移(yi)電(dian)流(liu)原(yuan)理(li)。從(cong)原(yuan)理(li)上(shang)來(lai)說(shuo),三(san)相(xiang)四(si)線(xian)或(huo)三(san)相(xiang)五(wu)線(xian),發(fa)電(dian)機(ji)有(you)中(zhong)線(xian)接(jie)地(di),設(she)備(bei)使(shi)用(yong)者(zhe)的(de)外(wai)殼(ke)接(jie)地(di)是(shi)最(zui)有(you)效(xiao)的(de)避(bi)雷(lei)方(fang)法(fa),但(dan)現(xian)在(zai)很(hen)多(duo)設(she)備(bei)都(dou)不(bu)接(jie)地(di),沒(mei)有(you)辦(ban)法(fa)接(jie),隻(zhi)有(you)很(hen)貴(gui)重(zhong)的(de)進(jin)口(kou)設(she)備(bei)用(yong)三(san)相(xiang)電(dian)源(yuan),中(zhong)間(jian)那(na)一(yi)條(tiao)地(di)線(xian),地(di)線(xian)不(bu)是(shi)中(zhong)線(xian),大(da)家(jia)要(yao)搞(gao)清(qing)楚(chu)。中(zhong)線(xian)雖(sui)然(ran)是(shi)接(jie)地(di)的(de),但(dan)在(zai)這(zhe)裏(li)不(bu)能(neng)當(dang)成(cheng)地(di)線(xian),地(di)線(xian)一(yi)定(ding)是(shi)自(zi)己(ji)大(da)樓(lou)本(ben)身(shen)的(de)地(di),而(er)且(qie)要(yao)量(liang)好(hao)接(jie)地(di)的(de)地(di)線(xian)。因(yin)為(wei)地(di)線(xian)接(jie)進(jin)去(qu)以(yi)後(hou),大(da)樓(lou)對(dui)外(wai)麵(mian)的(de)電(dian)磁(ci)層(ceng)進(jin)行(xing)屏(ping)蔽(bi)了(le),大(da)樓(lou)相(xiang)對(dui)來(lai)說(shuo)也(ye)是(shi)導(dao)電(dian)的(de),就(jiu)算(suan)不(bu)導(dao)電(dian),現(xian)在(zai)國(guo)家(jia)都(dou)有(you)安(an)全(quan)要(yao)求(qiu),大(da)樓(lou)超(chao)過(guo)多(duo)少(shao)層(ceng)都(dou)要(yao)加(jia)上(shang)避(bi)雷(lei)針(zhen),就(jiu)是(shi)防(fang)雷(lei)的(de)。如(ru)果(guo)不(bu)能(neng)接(jie)地(di),你(ni)就(jiu)要(yao)考(kao)慮(lv)充(chong)放(fang)電(dian)的(de)問(wen)題(ti)。前(qian)麵(mian)最(zui)好(hao)的(de)共(gong)模(mo)電(dian)容(rong)我(wo)覺(jiao)得(de)還(hai)是(shi)要(yao),我(wo)認(ren)為(wei)這(zhe)個(ge)共(gong)模(mo)電(dian)容(rong)最(zui)好(hao)連(lian)接(jie)上(shang),不(bu)能(neng)接(jie)大(da)地(di),要(yao)接(jie)在(zai)外(wai)殼(ke)上(shang),接(jie)到(dao)外(wai)殼(ke)上(shang)有(you)什(shen)麼(me)好(hao)處(chu)?共(gong)模(mo)電(dian)壓(ya)一(yi)進(jin)來(lai),雖(sui)然(ran)電(dian)流(liu)沒(mei)有(you)通(tong)過(guo)地(di)放(fang)電(dian)回(hui)路(lu),把(ba)電(dian)壓(ya)舉(ju)高(gao)起(qi)來(lai)了(le),與(yu)外(wai)麵(mian)輸(shu)入(ru)電(dian)壓(ya)是(shi)一(yi)樣(yang)的(de),外(wai)殼(ke)電(dian)壓(ya)取(qu)的(de)一(yi)樣(yang),起(qi)到(dao)了(le)屏(ping)蔽(bi)作(zuo)用(yong)。如(ru)果(guo)這(zhe)個(ge)接(jie)地(di)的(de)話(hua)會(hui)更(geng)加(jia)安(an)全(quan),但(dan)是(shi)地(di)線(xian)要(yao)足(zu)夠(gou)粗(cu),回(hui)路(lu)也(ye)足(zu)夠(gou),因(yin)為(wei)放(fang)電(dian)的(de)電(dian)流(liu)很(hen)大(da),很(hen)容(rong)易(yi)燒(shao)掉(diao)。這(zhe)幾(ji)個(ge)東(dong)西(xi)是(shi)經(jing)過(guo)很(hen)多(duo)年(nian)的(de)試(shi)驗(yan),8shihenchengshudedongxi,buguanzuogongmohaishifangleidouyaozuoshang,ruguolianjikedoumeiyou,zhishisuliaoke,yeyaokaolvzhegenxianjiedaoshenmeweizhizuihao?shijiedaolimianmianjizuidadedifang,jiushigonggongdimianjizuidadedifang,rangdianweijuqilai,qitadianweichabuhuichanshenghendadedianronghuilu。zhuyaoshikaolvchongfangdianhuilu,dianliuyuexiaoyuehao,lianggedianweichayuexiaoyuehao。
2、我wo們men是shi做zuo防fang雷lei模mo塊kuai的de,在zai實shi際ji應ying用yong中zhong,現xian場chang通tong常chang會hui碰peng到dao沒mei有you地di可ke接jie,這zhe時shi我wo們men首shou先xian建jian議yi客ke戶hu做zuo一yi個ge接jie地di係xi統tong,但dan如ru果guo因yin為wei造zao價jia或huo者zhe其qi他ta原yuan因yin確que實shi接jie地di有you困kun難nan,我wo們men建jian議yi客ke戶hu把ba防fang雷lei器qi的de地di和he其qi他ta設she備bei做zuo等deng電dian位wei連lian接jie後hou懸xuan浮fu,是shi否fou妥tuo當dang?
這(zhe)個(ge)防(fang)雷(lei)模(mo)塊(kuai)一(yi)般(ban)都(dou)是(shi)放(fang)電(dian)管(guan),一(yi)般(ban)在(zai)外(wai)麵(mian)賣(mai)的(de)都(dou)是(shi)壓(ya)敏(min)電(dian)阻(zu)或(huo)者(zhe)氣(qi)體(ti)放(fang)電(dian)管(guan),相(xiang)當(dang)於(yu)穩(wen)壓(ya)二(er)極(ji)管(guan)一(yi)樣(yang)的(de),比(bi)較(jiao)先(xian)進(jin)一(yi)點(dian)的(de)就(jiu)是(shi)與(yu)矽(gui)一(yi)樣(yang)的(de),就(jiu)是(shi)電(dian)壓(ya)超(chao)過(guo)多(duo)少(shao)的(de)時(shi)候(hou),壓(ya)敏(min)管(guan)就(jiu)導(dao)通(tong),或(huo)者(zhe)氣(qi)體(ti)放(fang)電(dian)管(guan),壓(ya)敏(min)電(dian)阻(zu)比(bi)較(jiao)便(bian)宜(yi),但(dan)是(shi)最(zui)不(bu)可(ke)靠(kao)的(de)。首(shou)先(xian)壓(ya)敏(min)電(dian)阻(zu)過(guo)壓(ya)衝(chong)擊(ji)的(de)時(shi)候(hou),壽(shou)命(ming)有(you)限(xian)的(de),隻(zhi)有(you)十(shi)幾(ji)次(ci)就(jiu)不(bu)能(neng)用(yong)了(le),壓(ya)敏(min)電(dian)阻(zu)是(shi)一(yi)堆(dui)亂(luan)七(qi)八(ba)糟(zao)的(de)二(er)極(ji)管(guan)在(zai)裏(li)麵(mian)互(hu)相(xiang)接(jie)觸(chu),就(jiu)是(shi)兩(liang)個(ge)不(bu)同(tong)金(jin)屬(shu)氧(yang)化(hua)物(wu)之(zhi)間(jian)互(hu)相(xiang)接(jie)觸(chu)相(xiang)當(dang)於(yu)一(yi)個(ge)二(er)極(ji)管(guan),以(yi)前(qian)我(wo)們(men)用(yong)礦(kuang)石(shi)收(shou)音(yin)機(ji)或(huo)者(zhe)用(yong)礦(kuang)石(shi)整(zheng)流(liu),就(jiu)是(shi)拿(na)兩(liang)塊(kuai)氧(yang)化(hua)銅(tong)或(huo)者(zhe)氧(yang)化(hua)礦(kuang)石(shi)連(lian)接(jie)以(yi)後(hou)就(jiu)可(ke)以(yi)當(dang)成(cheng)整(zheng)流(liu)二(er)極(ji)管(guan)使(shi)用(yong),原(yuan)理(li)是(shi)一(yi)樣(yang)的(de),裏(li)麵(mian)一(yi)大(da)堆(dui)氧(yang)化(hua)鉛(qian),每(mei)個(ge)界(jie)麵(mian)都(dou)相(xiang)同(tong),相(xiang)當(dang)於(yu)一(yi)個(ge)二(er)極(ji)管(guan),二(er)極(ji)管(guan)有(you)一(yi)個(ge)耐(nai)壓(ya),通(tong)過(guo)裏(li)麵(mian)來(lai)控(kong)製(zhi)耐(nai)壓(ya)的(de)參(can)數(shu)。這(zhe)種(zhong)一(yi)次(ci)擊(ji)穿(chuan)以(yi)後(hou)二(er)極(ji)管(guan)壞(huai)掉(diao)了(le),選(xuan)另(ling)外(wai)一(yi)個(ge)渠(qu)道(dao)。二(er)極(ji)管(guan)都(dou)是(shi)哪(na)個(ge)電(dian)壓(ya)高(gao)擊(ji)就(jiu)穿(chuan)哪(na)一(yi)個(ge),另(ling)外(wai)一(yi)個(ge)低(di)的(de)就(jiu)不(bu)擊(ji)穿(chuan),哪(na)個(ge)電(dian)壓(ya)高(gao)就(jiu)損(sun)壞(huai)那(na)一(yi)個(ge),然(ran)後(hou)再(zai)損(sun)壞(huai)另(ling)外(wai)一(yi)個(ge),最(zui)多(duo)隻(zhi)能(neng)損(sun)十(shi)幾(ji)次(ci),壓(ya)敏(min)電(dian)阻(zu)就(jiu)壞(huai)了(le)。用(yong)普(pu)通(tong)穩(wen)壓(ya)二(er)極(ji)管(guan)功(gong)率(lv)不(bu)夠(gou),分(fen)布(bu)電(dian)容(rong)比(bi)較(jiao)大(da)。用(yong)空(kong)氣(qi)的(de)話(hua)相(xiang)對(dui)放(fang)電(dian)管(guan)恢(hui)複(fu)時(shi)間(jian)很(hen)長(chang),點(dian)火(huo)時(shi)間(jian)也(ye)長(chang),導(dao)通(tong)時(shi)間(jian)很(hen)長(chang),恢(hui)複(fu)時(shi)間(jian)很(hen)長(chang),對(dui)於(yu)高(gao)速(su)的(de)保(bao)護(hu)來(lai)不(bu)及(ji)。比(bi)如(ru)說(shuo)作(zuo)為(wei)傳(chuan)輸(shu)線(xian)之(zhi)類(lei)的(de)保(bao)護(hu)是(shi)不(bu)行(xing)的(de),過(guo)壓(ya)以(yi)後(hou)一(yi)導(dao)通(tong)了(le),導(dao)致(zhi)長(chang)時(shi)間(jian)難(nan)以(yi)恢(hui)複(fu)。防(fang)雷(lei)模(mo)塊(kuai)我(wo)建(jian)議(yi)用(yong)在(zai)最(zui)後(hou)麵(mian),就(jiu)是(shi)作(zuo)為(wei)後(hou)備(bei)來(lai)使(shi)用(yong),就(jiu)是(shi)在(zai)IC輸(shu)入(ru)角(jiao)可(ke)以(yi)接(jie)輸(shu)入(ru)輸(shu)出(chu)接(jie)口(kou)的(de)位(wei)置(zhi),在(zai)電(dian)源(yuan)輸(shu)入(ru)的(de)地(di)方(fang)絕(jue)對(dui)不(bu)能(neng)用(yong),一(yi)個(ge)是(shi)用(yong)上(shang)去(qu)沒(mei)有(you)效(xiao),另(ling)外(wai)成(cheng)本(ben)很(hen)高(gao),作(zuo)為(wei)輸(shu)入(ru)端(duan)用(yong)人(ren)工(gong)排(pai)一(yi)個(ge)放(fang)電(dian)裝(zhuang)置(zhi),在(zai)後(hou)麵(mian)再(zai)加(jia)上(shang)防(fang)雷(lei)模(mo)塊(kuai),互(hu)相(xiang)組(zu)合(he)起(qi)來(lai)使(shi)用(yong)。
3、關於EMI電磁幹擾,我們的防雷元器件是否能夠奏效?還是主要依靠設計、合理布局更有效?
按照道理EMI是電磁幹擾,避雷元器件按照道理並不聯係在一起,但EMC濾波裏麵,與EMC濾波器同樣有防雷功能,就是前麵的幾個電感和共模電容還有差模電容對防雷都起到作用,大家要理解,EMC濾lv波bo是shi用yong於yu設she備bei上shang的de,但dan反fan過guo來lai考kao慮lv雷lei電dian的de時shi候hou,你ni就jiu要yao把ba幹gan擾rao信xin號hao從cong外wai麵mian輸shu進jin來lai,要yao這zhe樣yang考kao慮lv了le,不bu能neng單dan方fang麵mian,最zui好hao在zai防fang雷lei加jia上shang一yi個ge放fang電dian裝zhuang置zhi加jia在zai電dian感gan後hou麵mian,共gong用yong共gong模mo濾lv波bo電dian容rong。
4、ESD在PCB設計中應注意的事項有哪些?
ESD一般除了防雷以外,還有一些別的相關內容,裏麵有一些IC很容易受到周邊電壓比較高的器件幹擾或損壞,比如說在電視機裏麵,電視機裏麵的高壓包產生的高壓是上萬的,裏麵的CPUdengmoshidianlunijueduibunengkaojingaoyadianyuanbufen,bixuyuanlita。yiqianwomenshiguo,doushiyinweiyugaoyabaokaodetaijinle,balimiandeqidongqiganrao,balimiandeshujudaluan,womenzhishizaishangmiantieleyikuaishibopian,zuikaishishiguolvzuixiangyanlimianyoushibopian,womenconglajiduilimianjianlai,yingjichuliwangshangmiantie,rangxiulibuzheyanglaiyingfuchuli。manmanwomenduizhegedongxirenshihenqingchule,xianzaihenduojichengdianlucaiquzhezhongfangshi,youdezaishangmiandaiyigesanrepian,benshenkeyizuopingbi,huozhezaishangmiantieyigejiaozhi,jiaozhiyoudaodiandezuoyong,keyifangshangqu,zheshiESD方fang麵mian的de防fang護hu方fang法fa。因yin為wei貼tie了le一yi塊kuai以yi後hou,哪na怕pa電dian離li層ceng很hen高gao的de打da下xia去qu都dou不bu會hui擊ji壞huai,所suo以yi在zai貴gui重zhong集ji成cheng電dian路lu裏li麵mian,在zai電dian路lu板ban上shang麵mian貼tie一yi塊kuai有you一yi邊bian絕jue緣yuan的de,兩liang邊bian的de絕jue緣yuan都dou是shi零ling,但dan是shi有you一yi塊kuai示shi波bo片pian,外wai麵mian都dou有you賣mai,非fei常chang方fang便bian。現xian在zai電dian視shi機ji裏li麵mian都dou大da量liang采cai用yong這zhe種zhong技ji術shu。對dui於yu排pai線xian的de輸shu入ru輸shu出chu線xian、xinhaoxiandoushikaodeyuejinyuehao,lianggenxianyidingyaozhaochulainageshishuru,nageshishuchu,dianliuliujinquhaishiliuchulaide,xiankaojindeyuejinyuehao,limiandemianjiyuesuoxiaoyuehao,ruguodianliuhenxiao,xinhaogonglvhenxiao,jinliangyongxiaoerbushiyongda,ruguodalefenbudianrongyeda,fenbudianrongdadeyihourongyijieshoudianziganraohedianrongsunhuai,limiandechangxiaoguanyongyanjingkanbudao,yongfangdajingfangdajibaibeiyeshikanbudaode,yinxiankeyikandao,limianyinxiandedianrongxiangduilaishuogaohenduo,jieyidiandianzhengdianjinquyihoujichuanle,suoyilimiandedaoxianyueduanyuehao。jichengdianludeshurushuchudouyiban,jialeyigeerjiguan,jiushiyudianrongjiezaiyiqi,benshenzaidianlulimiandouyoubaohuzuoyong,ruguomeiyoujiedaodianlulimianyongshouqumoshihuaidiaode,jiedaolimianyouxinhaozuoyonglejiubuhuihuai。
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5、在射頻電路中,敏感線路(如數據線等)如何保護?
shujuxiandajiadouyijingyouhenduofangfa,yibanshujuxianzuihaoyongchafen,jianglianggenxianniuzaiyiqi,niuzaiyiqiyihouyigeliujinqu,yigeliuchulai,shuangjiaozaiyiqi,waimianjiayicengpingbixian,waimianzhiyouyitiaojiedi,buyaoliangtiaodoujie,jieyitoujiukeyile,shuangjiaoxianduidianziganraohuxiangdixiao,tongyigefangxiangliuchulaidedianliuchanshengdefangxiangzhenghaoxiangfan,huxiangdixiao,chafenshizuihaode,buyaojiedaogonggongdishang,yongchafen。henjiandan,zhegexianjiayigecihuan,liangduandoujiayigecihuan,zhegecihuanduichamoyouxiangdangdengyuling,liuguodexinhaoyigeshichamoxinhao,ganraoxinhaodabufenshigongmode,jiashangdianganshangmianduigongmohenyouxiao,ESD放電基本上都是共模,加載上麵對ESD起qi到dao保bao護hu作zuo用yong。充chong放fang電dian加jia一yi個ge小xiao磁ci環huan,如ru果guo沒mei有you小xiao磁ci環huan,用yong適shi配pei器qi往wang插cha頭tou上shang一yi插cha,瞬shun間jian選xuan擇ze突tu然ran充chong電dian會hui有you損sun壞huai,不bu要yao輕qing易yi把ba磁ci環huan去qu掉diao,那na就jiu是shi讓rang你ni對dui充chong放fang電dian抑yi製zhi速su度du的de降jiang慢man。
6、IC引腳的靜電防護,加什麼器件既經濟又有效?
如果不考慮速度,最好是在輸入端加一個電阻,靠近IC加一個電容,這隻有幾十PU加大,如果信號頻率很高,盡量想辦法把信號線的阻耗降低,不要搞得很高。現在一般的信號線,高頻都是50歐姆,兩個之間接一個75安培或50安培的,把阻礙降低,直衝放電就是兩個電位。75歐姆以上,一根線上麵加的1v電壓上去,流過的電流多大?或者說一個毫安的電流在上麵的電壓也很小,因為ESD放電的電壓很高,電流很小,放電電壓馬上掉下來,不會衝擊到集成電路裏麵去。所以在要求不是特別高上麵,盡量把輸入降低。
7、ESD防護器件什麼時候應該放在端口處,什麼時候該放在芯片管角?
保bao護hu單dan個ge集ji成cheng電dian路lu就jiu放fang在zai集ji成cheng電dian路lu的de地di方fang最zui好hao,如ru果guo保bao護hu整zheng個ge設she備bei就jiu放fang在zai端duan口kou。放fang在zai集ji成cheng電dian路lu這zhe個ge地di方fang,後hou麵mian那na一yi段duan照zhao樣yang有you電dian壓ya可ke以yi感gan應ying到dao別bie的deIC上,對別的IC會產生損壞,所以你要保護好IC,就在IC加上ESD的保護,如果對整個設備進行保護的話,所有的接口都加ESD保護就足夠了,這個成本是最低的。因為你把數據輸出、輸入接一個保護,裏麵本身不會產生ESD放電,如果裏麵產生ESD放電早不能過關,ESD放(fang)電(dian)肯(ken)定(ding)從(cong)外(wai)麵(mian)進(jin)去(qu)的(de),把(ba)所(suo)有(you)的(de)口(kou)都(dou)封(feng)住(zhu)就(jiu)不(bu)會(hui)有(you)問(wen)題(ti)。所(suo)以(yi),我(wo)建(jian)議(yi)你(ni)如(ru)果(guo)從(cong)設(she)備(bei)考(kao)慮(lv),從(cong)成(cheng)本(ben)考(kao)慮(lv)就(jiu)接(jie)輸(shu)入(ru)輸(shu)出(chu)口(kou)的(de)地(di)方(fang),為(wei)了(le)保(bao)護(hu)集(ji)成(cheng)電(dian)路(lu),對(dui)其(qi)他(ta)不(bu)管(guan)的(de)話(hua)就(jiu)接(jie)在(zai)集(ji)成(cheng)電(dian)路(lu)上(shang)。
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