MOS管损坏(huai)是什么(me)原因(yin) 开关耗损详细原因(yin)
信息来源：本站 日期：2017-07-06
mos在控制器电路中的工作状态：开经过程（由截止到导通的过渡过程）、导通状态、关断过程（由导通到截止的过渡过程）、截止状态。Mos主要损耗也对应这几个状态，开关损耗（开经过程和关断过程），导通损耗，截止损耗（漏电流惹起的，这个忽略不计），还有雪崩能量损耗。只需把这些损耗控制在mos承受规格之内，mos即会正常工作，超出承受范围，即发作损坏。
而开关损耗常常大于导通状态损耗（不同mos这个差距可能很大)。
Mos损坏主要缘由： 过流----------持续大电流或瞬间超大电流惹起的结温过高而烧毁；
过压----------源漏过压击穿、源栅极过压击穿；静电----------静电击穿。CMOS电路都怕静电； Mos开关原理（扼要）。Mos是电压驱动型器件，只需栅极和源级间给一个恰当电压，源级和漏级间通路就构成。这个电流通路的电阻被成为mos内阻，就是导通电阻
Mos问题远没这么简单，省事在它的栅极和源级间，源级和漏级间，栅极和漏级间MOS管三个(ge)极内(nei)部都(dou)有等效电(dian)容(rong)。所以(yi)(yi)给(ji)栅(zha)极电(dian)压的(de)过(guo)程就是给(ji)电(dian)容(rong)充(chong)电(dian)的(de)过(guo)程（电(dian)容(rong)电(dian)压不(bu)能突(tu)变），所以(yi)(yi)mos源级和(he)漏级间由(you)截(jie)止到导(dao)通的(de)开经(jing)过(guo)程受栅(zha)极电(dian)容(rong)的(de)充(chong)电(dian)过(guo)程限制。
但是(shi)，这(zhei)三个(ge)(ge)(ge)(ge)等效(xiao)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)是(shi)构成(cheng)串并(bing)联组合关(guan)系(xi)，它们相互(hu)影响，并(bing)不(bu)(bu)是(shi)独立的(de)，假设独立的(de)就(jiu)很简单了。其中一(yi)(yi)个(ge)(ge)(ge)(ge)关(guan)键电(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)就(jiu)是(shi)栅极(ji)和漏(lou)(lou)级间的(de)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)Cgd，这(zhei)个(ge)(ge)(ge)(ge)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)业界称为(wei)米(mi)(mi)勒电(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)。这(zhei)个(ge)(ge)(ge)(ge)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)不(bu)(bu)是(shi)恒(heng)定的(de)，随栅极(ji)和漏(lou)(lou)级间电(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)压变化而疾速变化。这(zhei)个(ge)(ge)(ge)(ge)米(mi)(mi)勒电(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)是(shi)栅极(ji)和源级电(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)充(chong)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)的(de)绊脚(jiao)石，由于(yu)(yu)栅极(ji)给(ji)栅-源电(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)Cgs充(chong)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)抵(di)(di)达一(yi)(yi)个(ge)(ge)(ge)(ge)平(ping)(ping)(ping)台(tai)后，栅极(ji)的(de)充(chong)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流必需给(ji)米(mi)(mi)勒电(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)Cgd充(chong)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)，这(zhei)时栅极(ji)和源级间电(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)压不(bu)(bu)再升高，抵(di)(di)达一(yi)(yi)个(ge)(ge)(ge)(ge)平(ping)(ping)(ping)台(tai)，这(zhei)个(ge)(ge)(ge)(ge)是(shi)米(mi)(mi)勒平(ping)(ping)(ping)台(tai)（米(mi)(mi)勒平(ping)(ping)(ping)台(tai)就(jiu)是(shi)给(ji)Cgd充(chong)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)的(de)过程），米(mi)(mi)勒平(ping)(ping)(ping)台(tai)大家首先想到的(de)省事就(jiu)是(shi)米(mi)(mi)勒振荡。（即，栅极(ji)先给(ji)Cgs充(chong)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)，抵(di)(di)达一(yi)(yi)定平(ping)(ping)(ping)台(tai)后再给(ji)Cgd充(chong)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)）由于(yu)(yu)这(zhei)个(ge)(ge)(ge)(ge)时分源级和漏(lou)(lou)级间电(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)压疾速变化，内(nei)部电(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)相应疾速充(chong)放电(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)，这(zhei)些电(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流脉冲(chong)会招致mos寄生电(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)感(gan)产生很大感(gan)抗，这(zhei)里面(mian)就(jiu)有(you)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)，电(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)感(gan)，电(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻组成(cheng)震(zhen)荡电(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路（能构成(cheng)2个(ge)(ge)(ge)(ge)回路），并(bing)且电(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流脉冲(chong)越(yue)强频率越(yue)高震(zhen)荡幅度越(yue)大。所以(yi)最关(guan)键的(de)问(wen)题就(jiu)是(shi)这(zhei)个(ge)(ge)(ge)(ge)米(mi)(mi)勒平(ping)(ping)(ping)台(tai)如何过渡。
Gs极加电(dian)容，减慢mos管(guan)导通(tong)(tong)时间(jian)，有助于(yu)减小米勒(le)(le)振荡(dang)。防止mos管(guan)烧毁。过快的(de)充电(dian)会(hui)(hui)招致猛(meng)烈的(de)米勒(le)(le)震荡(dang)，但过慢的(de)充电(dian)虽(sui)减小了震荡(dang)，但会(hui)(hui)延长开(kai)(kai)关从(cong)而(er)增加开(kai)(kai)关损(sun)耗。Mos开(kai)(kai)经(jing)(jing)过程(cheng)(cheng)源(yuan)级(ji)和漏(lou)级(ji)间(jian)等效电(dian)阻(zu)(zu)相当于(yu)从(cong)无(wu)量(liang)大电(dian)阻(zu)(zu)到(dao)(dao)阻(zu)(zu)值很(hen)小的(de)导通(tong)(tong)内(nei)阻(zu)(zu)（导通(tong)(tong)内(nei)阻(zu)(zu)普通(tong)(tong)低压(ya)mos只需(xu)几毫欧(ou)姆）的(de)一个(ge)(ge)转变过程(cheng)(cheng)。比如一个(ge)(ge)mos最大电(dian)流(liu)100a，电(dian)池电(dian)压(ya)96v，在(zai)开(kai)(kai)经(jing)(jing)过程(cheng)(cheng)中(zhong)，有那(nei)么一瞬(shun)间(jian)（刚进(jin)入(ru)米勒(le)(le)平台时）mos发(fa)热功(gong)(gong)(gong)率(lv)(lv)是(shi)P=V*I(此时电(dian)流(liu)已达最大，负载尚未跑(pao)起(qi)来，一切的(de)功(gong)(gong)(gong)率(lv)(lv)都降落(luo)在(zai)MOS管(guan)上)，P=96*100=9600w！这(zhei)时它(ta)发(fa)热功(gong)(gong)(gong)率(lv)(lv)最大，然后发(fa)热功(gong)(gong)(gong)率(lv)(lv)疾速降低直到(dao)(dao)完好导通(tong)(tong)时功(gong)(gong)(gong)率(lv)(lv)变成100*100*0.003=30w（这(zhei)里假定这(zhei)个(ge)(ge)mos导通(tong)(tong)内(nei)阻(zu)(zu)3毫欧(ou)姆）。开(kai)(kai)关过程(cheng)(cheng)中(zhong)这(zhei)个(ge)(ge)发(fa)热功(gong)(gong)(gong)率(lv)(lv)变化(hua)是(shi)惊人的(de)。
假(jia)设开(kai)(kai)(kai)通时间慢，意味着发热从9600w到30w过渡的慢，mos结温会(hui)升高的凶猛。所以开(kai)(kai)(kai)关(guan)越慢，结温越高，容(rong)(rong)易烧mos。为了(le)不(bu)烧mos，只(zhi)能降(jiang)(jiang)低(di)(di)mos限流或者降(jiang)(jiang)低(di)(di)电池电压，比如给它(ta)限制(zhi)50a或电压降(jiang)(jiang)低(di)(di)一(yi)半成48v，这(zhei)(zhei)样(yang)(yang)开(kai)(kai)(kai)关(guan)发热损(sun)(sun)耗(hao)也降(jiang)(jiang)低(di)(di)了(le)一(yi)半。不(bu)烧管子了(le)。这(zhei)(zhei)也是(shi)(shi)高压控(kong)(kong)容(rong)(rong)易烧管子缘由，高压控(kong)(kong)制(zhi)器和(he)(he)低(di)(di)压的只(zhi)需开(kai)(kai)(kai)关(guan)损(sun)(sun)耗(hao)不(bu)一(yi)样(yang)(yang)（开(kai)(kai)(kai)关(guan)损(sun)(sun)耗(hao)和(he)(he)电池端电压基本成正比，假(jia)定限流一(yi)样(yang)(yang)），导(dao)通损(sun)(sun)耗(hao)完好受(shou)mos内阻决议，和(he)(he)电池电压没任何关(guan)系。其实(shi)整个mos开(kai)(kai)(kai)经(jing)(jing)过程(cheng)非常复杂(za)。里面变量太多(duo)。总之就(jiu)是(shi)(shi)开(kai)(kai)(kai)关(guan)慢不(bu)容(rong)(rong)易米(mi)(mi)勒震(zhen)荡(dang)，但开(kai)(kai)(kai)关(guan)损(sun)(sun)耗(hao)大，管子发热大，开(kai)(kai)(kai)关(guan)速(su)度快理论上开(kai)(kai)(kai)关(guan)损(sun)(sun)耗(hao)低(di)(di)（只(zhi)需能有效抑止米(mi)(mi)勒震(zhen)荡(dang)），但是(shi)(shi)常常米(mi)(mi)勒震(zhen)荡(dang)很(hen)凶猛（假(jia)设米(mi)(mi)勒震(zhen)荡(dang)很(hen)严重，可能在米(mi)(mi)勒平台就(jiu)烧管子了(le)），反而开(kai)(kai)(kai)关(guan)损(sun)(sun)耗(hao)也大，并且上臂(bei)mos震(zhen)荡(dang)更有可能惹起(qi)下(xia)臂(bei)mos误导(dao)通，构(gou)成上下(xia)臂(bei)短路。所以这(zhei)(zhei)个很(hen)考验(yan)设计师的驱动电路布线(xian)和(he)(he)主回路布线(xian)技艺。最终就(jiu)是(shi)(shi)找(zhao)个平衡点（普通开(kai)(kai)(kai)经(jing)(jing)过程(cheng)不(bu)超越1us）。
开通(tong)损耗(hao)这(zhei)(zhei)个(ge)(ge)最简单(dan)，只(zhi)和(he)导通(tong)电(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)成正(zheng)比(bi)，想大(da)电(dian)(dian)(dian)(dian)(dian)(dian)流(liu)低损耗(hao)找(zhao)内(nei)阻(zu)低的(de)。下面引见下对普通(tong)用户适用点(dian)的(de)。 Mos选择的(de)重要(yao)参数扼(e)要(yao)说明。以datasheet举例说明。 栅极电(dian)(dian)(dian)(dian)(dian)(dian)荷。Qgs， Qgd Qgs:指的(de)是栅极从0v充电(dian)(dian)(dian)(dian)(dian)(dian)到对应电(dian)(dian)(dian)(dian)(dian)(dian)流(liu)米勒(le)平(ping)台(tai)时总充入电(dian)(dian)(dian)(dian)(dian)(dian)荷（理论电(dian)(dian)(dian)(dian)(dian)(dian)流(liu)不同(tong)，这(zhei)(zhei)个(ge)(ge)平(ping)台(tai)高度(du)不同(tong)，电(dian)(dian)(dian)(dian)(dian)(dian)流(liu)越(yue)大(da)，平(ping)台(tai)越(yue)高，这(zhei)(zhei)个(ge)(ge)值(zhi)越(yue)大(da)）。这(zhei)(zhei)个(ge)(ge)阶段是给Cgs充电(dian)(dian)(dian)(dian)(dian)(dian)（也相(xiang)当于Ciss，输(shu)入电(dian)(dian)(dian)(dian)(dian)(dian)容(rong)）。 Qgd:指的(de)是整个(ge)(ge)米勒(le)平(ping)台(tai)的(de)总充电(dian)(dian)(dian)(dian)(dian)(dian)电(dian)(dian)(dian)(dian)(dian)(dian)荷（在这(zhei)(zhei)称为米勒(le)电(dian)(dian)(dian)(dian)(dian)(dian)荷）。这(zhei)(zhei)个(ge)(ge)过程给Cgd（Crss，这(zhei)(zhei)个(ge)(ge)电(dian)(dian)(dian)(dian)(dian)(dian)容(rong)随着gd电(dian)(dian)(dian)(dian)(dian)(dian)压不同(tong)疾速变(bian)化）充电(dian)(dian)(dian)(dian)(dian)(dian)。
开关(guan)过(guo)冲(chong)中，mos主(zhu)要(yao)发(fa)热(re)区(qu)(qu)间(jian)(jian)是(shi)粗红(hong)色(se)标注的阶段。从Vgs开端(duan)超越(yue)阈值(zhi)电(dian)压(ya)，到米(mi)勒(le)(le)平(ping)台终(zhong)了是(shi)主(zhu)要(yao)发(fa)热(re)区(qu)(qu)间(jian)(jian)。其中米(mi)勒(le)(le)平(ping)台终(zhong)了后mos基本(ben)完(wan)好翻(fan)开这(zhei)时损(sun)耗是(shi)基本(ben)导通损(sun)耗（mos内(nei)阻(zu)越(yue)低损(sun)耗越(yue)低）。阈值(zhi)电(dian)压(ya)前，mos没(mei)有(you)翻(fan)开，几(ji)乎没(mei)损(sun)耗（只(zhi)需漏电(dian)流惹起的一点损(sun)耗）。其中又以红(hong)色(se)拐弯中央损(sun)耗最大（Qgs充电(dian)将近终(zhong)了，快到米(mi)勒(le)(le)平(ping)台和刚进入米(mi)勒(le)(le)平(ping)台这(zhei)个(ge)(ge)过(guo)程发(fa)热(re)功率(lv)最大（更粗线表示）。 所(suo)以一定(ding)(ding)充电(dian)电(dian)流下，红(hong)色(se)标注区(qu)(qu)间(jian)(jian)总电(dian)荷小(xiao)的管子会(hui)很快渡过(guo)，这(zhei)样发(fa)热(re)区(qu)(qu)间(jian)(jian)时间(jian)(jian)就(jiu)短，总发(fa)热(re)量(liang)就(jiu)低。所(suo)以理论上选(xuan)择Qgs和Qgd小(xiao)的mos管能快速渡过(guo)开关(guan)区(qu)(qu)。导通内(nei)阻(zu)。Rds（on）。这(zhei)个(ge)(ge)耐压(ya)一定(ding)(ding)情(qing)况(kuang)下是(shi)越(yue)低越(yue)好。不(bu)过(guo)不(bu)同(tong)厂家标的内(nei)阻(zu)是(shi)有(you)不(bu)同(tong)测(ce)试条件的。测(ce)试条件不(bu)同(tong)，内(nei)阻(zu)丈(zhang)量(liang)值(zhi)会(hui)不(bu)一样。
同一管子(zi)，温度越高(gao)内阻越大(da)(da)（这是硅半导(dao)体材料在mos制造工(gong)艺的(de)特性(xing)，改动不了，能稍改善）。所以(yi)大(da)(da)电(dian)流(liu)测(ce)试(shi)(shi)(shi)内阻会增(zeng)大(da)(da)（大(da)(da)电(dian)流(liu)下(xia)结(jie)温会显著升(sheng)高(gao)），小电(dian)流(liu)或脉冲电(dian)流(liu)测(ce)试(shi)(shi)(shi)，内阻降低（由于结(jie)温没(mei)有大(da)(da)幅升(sheng)高(gao)，没(mei)热积聚）。有的(de)管子(zi)标称典(dian)型内阻和你自己(ji)用小电(dian)流(liu)测(ce)试(shi)(shi)(shi)几乎一样，而有的(de)管子(zi)自己(ji)小电(dian)流(liu)测(ce)试(shi)(shi)(shi)比标称典(dian)型内阻低很多(duo)（由于它的(de)测(ce)试(shi)(shi)(shi)标准是大(da)(da)电(dian)流(liu)）
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