详(xiang)解N沟(gou)道MOS管导通电压、导通条件(jian)及过(guo)程-KIA MOS管
信息来源：本站 日期：2018-08-27
场效(xiao)应(ying)管(guan)导(dao)通(tong)与截止由栅源电压(ya)来(lai)操(cao)控(kong)，关于增(zeng)强场效(xiao)应(ying)管(guan)方面来(lai)说(shuo)，N沟道(dao)的管(guan)子(zi)加(jia)正向电压(ya)即导(dao)通(tong)，P沟道(dao)的管(guan)子(zi)则加(jia)反向电压(ya)。一般2V～4V就OK了。
可是(shi)(shi)，场效应管分为增(zeng)(zeng)强(qiang)型和耗尽型，增(zeng)(zeng)强(qiang)型的管子(zi)是(shi)(shi)必须需(xu)求加(jia)电压才(cai)干导通(tong)的，而耗尽型管子(zi)本来(lai)就处于导通(tong)状(zhuang)况，加(jia)栅源电压是(shi)(shi)为了使其截止。
开(kai)(kai)关(guan)只有(you)两(liang)种状况(kuang)通和(he)断，三(san)极(ji)(ji)管(guan)和(he)场效应管(guan)作(zuo)业(ye)(ye)有(you)三(san)种状况(kuang)，1.截止，2.线性扩大(da)，3.饱满（基极(ji)(ji)电(dian)(dian)(dian)流持续添加(jia)而集(ji)电(dian)(dian)(dian)极(ji)(ji)电(dian)(dian)(dian)流不再添加(jia)）。使晶(jing)(jing)体(ti)(ti)(ti)(ti)管(guan)只作(zuo)业(ye)(ye)在1和(he)3状况(kuang)的电(dian)(dian)(dian)路(lu)称之为开(kai)(kai)关(guan)电(dian)(dian)(dian)路(lu)，一般以(yi)晶(jing)(jing)体(ti)(ti)(ti)(ti)管(guan)截止，集(ji)电(dian)(dian)(dian)极(ji)(ji)不吸(xi)收电(dian)(dian)(dian)流表明(ming)(ming)开(kai)(kai)关(guan)；以(yi)晶(jing)(jing)体(ti)(ti)(ti)(ti)管(guan)饱满，发射(she)极(ji)(ji)和(he)集(ji)电(dian)(dian)(dian)极(ji)(ji)之间的电(dian)(dian)(dian)压差挨(ai)近于(yu)(yu)0V时表明(ming)(ming)开(kai)(kai)。开(kai)(kai)关(guan)电(dian)(dian)(dian)路(lu)用于(yu)(yu)数字电(dian)(dian)(dian)路(lu)时，输出电(dian)(dian)(dian)位挨(ai)近0V时表明(ming)(ming)0，输出电(dian)(dian)(dian)位挨(ai)近电(dian)(dian)(dian)源(yuan)电(dian)(dian)(dian)压时表明(ming)(ming)1。所以(yi)数字集(ji)成电(dian)(dian)(dian)路(lu)内部的晶(jing)(jing)体(ti)(ti)(ti)(ti)管(guan)都工作(zuo)在开(kai)(kai)关(guan)状况(kuang)。
场(chang)效应管按沟道分可分为(wei)Ｎ沟道和Ｐ沟道管（在符号图中可看到中间(jian)的箭头方(fang)向不一样）。
按资料(liao)可分(fen)为(wei)结(jie)(jie)型(xing)管(guan)(guan)和绝缘(yuan)(yuan)(yuan)栅型(xing)管(guan)(guan)，绝缘(yuan)(yuan)(yuan)栅型(xing)又分(fen)为(wei)耗尽(jin)型(xing)和增强(qiang)型(xing)，一般主板(ban)上大多是绝缘(yuan)(yuan)(yuan)栅型(xing)管(guan)(guan)简称(cheng)(cheng)MOS管(guan)(guan)，而且大多选用(yong)增强(qiang)型(xing)的Ｎ沟(gou)道，其次是增强(qiang)型(xing)的Ｐ沟(gou)道，结(jie)(jie)型(xing)管(guan)(guan)和耗尽(jin)型(xing)管(guan)(guan)简直不(bu)用(yong)。 场(chang)效(xiao)应(ying)晶体(ti)(ti)(ti)管(guan)(guan)简称(cheng)(cheng)场(chang)效(xiao)应(ying)管(guan)(guan).由大都载(zai)流(liu)子(zi)参加导(dao)电,也称(cheng)(cheng)为(wei)单极型(xing)晶体(ti)(ti)(ti)管(guan)(guan).它(ta)归于电压操控(kong)型(xing)半导(dao)体(ti)(ti)(ti)器材. 场(chang)效(xiao)应(ying)管(guan)(guan)是使(shi)(shi)用(yong)大都载(zai)流(liu)子(zi)导(dao)电,所以(yi)称(cheng)(cheng)之为(wei)单极型(xing)器材,而晶体(ti)(ti)(ti)管(guan)(guan)是即(ji)有(you)大都载(zai)流(liu)子(zi),也使(shi)(shi)用(yong)少(shao)量载(zai)流(liu)子(zi)导(dao)电,被(bei)称(cheng)(cheng)之为(wei)双极型(xing)器材.有(you)些场(chang)效(xiao)应(ying)管(guan)(guan)的源极和漏极能够交换使(shi)(shi)用(yong),栅压也可正可负,灵活性(xing)比(bi)晶体(ti)(ti)(ti)管(guan)(guan)好。
开(kai)(kai)(kai)启(qi)(qi)(qi)电(dian)(dian)(dian)(dian)压(ya)(YGS（th））也(ye)称为“栅(zha)极阈值(zhi)电(dian)(dian)(dian)(dian)压(ya)”，这(zhei)个数值(zhi)的(de)(de)(de)(de)(de)选择在这(zhei)里(li)主要与用作(zuo)比拟器的(de)(de)(de)(de)(de)运(yun)放(fang)有火。VMOS不像BJT，栅(zha)极相关(guan)于(yu)源极需求有一定(ding)的(de)(de)(de)(de)(de)电(dian)(dian)(dian)(dian)压(ya)才干开(kai)(kai)(kai)通(tong)(tong)，这(zhei)个电(dian)(dian)(dian)(dian)压(ya)的(de)(de)(de)(de)(de)最(zui)(zui)低值(zhi)（通(tong)(tong)常(chang)是(shi)一个范围）称为开(kai)(kai)(kai)启(qi)(qi)(qi)电(dian)(dian)(dian)(dian)压(ya)，饱和导通(tong)(tong)电(dian)(dian)(dian)(dian)压(ya)普(pu)(pu)(pu)通(tong)(tong)为开(kai)(kai)(kai)启(qi)(qi)(qi)电(dian)(dian)(dian)(dian)压(ya)的(de)(de)(de)(de)(de)一倍(bei)左右(you)，假如(ru)技术手册给出(chu)(chu)的(de)(de)(de)(de)(de)开(kai)(kai)(kai)启(qi)(qi)(qi)电(dian)(dian)(dian)(dian)压(ya)是(shi)一个范围，取最(zui)(zui)大值(zhi)。VMOS的(de)(de)(de)(de)(de)开(kai)(kai)(kai)启(qi)(qi)(qi)电(dian)(dian)(dian)(dian)压(ya)普(pu)(pu)(pu)通(tong)(tong)为5V左右(you)，低开(kai)(kai)(kai)启(qi)(qi)(qi)电(dian)(dian)(dian)(dian)压(ya)的(de)(de)(de)(de)(de)种(zhong)类有2V左右(you)的(de)(de)(de)(de)(de)。假如(ru)采用5. 5V丁作(zuo)电(dian)(dian)(dian)(dian)压(ya)的(de)(de)(de)(de)(de)运(yun)放(fang)，其输出(chu)(chu)电(dian)(dian)(dian)(dian)平最(zui)(zui)大约(yue)为土2.5V，即(ji)便采用低开(kai)(kai)(kai)启(qi)(qi)(qi)电(dian)(dian)(dian)(dian)压(ya)的(de)(de)(de)(de)(de)VMOS，如(ru)图2.6中(zhong)的(de)(de)(de)(de)(de)2SK2313，最(zui)(zui)低驱动(dong)电(dian)(dian)(dian)(dian)平也(ye)至(zhi)少为土5V，因而(er)依据上文关(guan)于(yu)运(yun)放(fang)的(de)(de)(de)(de)(de)选择准绳，5.5V工(gong)(gong)作(zuo)电(dian)(dian)(dian)(dian)压(ya)的(de)(de)(de)(de)(de)运(yun)放(fang)实(shi)践(jian)上是(shi)不能用的(de)(de)(de)(de)(de)，引(yin)荐的(de)(de)(de)(de)(de)工(gong)(gong)作(zuo)电(dian)(dian)(dian)(dian)压(ya)最(zui)(zui)低为±6V，由于(yu)运(yun)放(fang)的(de)(de)(de)(de)(de)最(zui)(zui)高输出(chu)(chu)电(dian)(dian)(dian)(dian)平通(tong)(tong)常(chang)会略(lve)低于(yu)工(gong)(gong)作(zuo)电(dian)(dian)(dian)(dian)压(ya)，即(ji)便是(shi)近年(nian)来开(kai)(kai)(kai)端普(pu)(pu)(pu)遍应用的(de)(de)(de)(de)(de)“轨(gui)(gui)至(zhi)轨(gui)(gui)”输入／输出(chu)(chu)的(de)(de)(de)(de)(de)运(yun)放(fang)也(ye)是(shi)如(ru)此。
P沟(gou)(gou)(gou)(gou)道(dao)VMOS当然也能用(yong)，只是驱动办法与N沟(gou)(gou)(gou)(gou)道(dao)相反。不(bu)过(guo)，直到(dao)现在，与N沟(gou)(gou)(gou)(gou)通(tong)同一系列同电(dian)(dian)(dian)压规格的(de)P沟(gou)(gou)(gou)(gou)通(tong)的(de)VMOS，普通(tong)电(dian)(dian)(dian)流规格比(bi)N沟(gou)(gou)(gou)(gou)道(dao)的(de)低，而(er)饱和(he)导通(tong)电(dian)(dian)(dian)压比(bi)N沟(gou)(gou)(gou)(gou)道(dao)高。因而(er)选N沟(gou)(gou)(gou)(gou)道(dao)而(er)不(bu)选P沟(gou)(gou)(gou)(gou)道(dao)。
导(dao)通时(shi)序可分为to~t1、t1~t2、 t2~t3 、t3~t4四(si)个(ge)时(shi)间段，这四(si)个(ge)时(shi)间段有不(bu)同的等效电(dian)路。
1）t0-t1：C GS1 开始(shi)充(chong)电，栅极电压还没有(you)到达(da)V GS（th），导电沟道没有(you)形成，MOSFET仍处(chu)于关闭状态(tai)。
2）[t1-t2]区(qu)间, GS间电压(ya)到(dao)(dao)达Vgs（th），DS间导电沟道开始形成，MOSFET开启，DS电流增(zeng)加到(dao)(dao)ID, Cgs2 迅速充电，Vgs由(you)Vgs（th）指(zhi)数增(zeng)长(zhang)到(dao)(dao)Va。
3）[t2-t3]区间(jian),MOSFET的DS电(dian)(dian)(dian)压(ya)降至(zhi)与Vgs相同,产生Millier效应，Cgd电(dian)(dian)(dian)容(rong)大大增加,栅极电(dian)(dian)(dian)流持续流过(guo)，由于C gd 电(dian)(dian)(dian)容(rong)急剧(ju)增大，抑(yi)制了栅极电(dian)(dian)(dian)压(ya)对Cgs 的充(chong)电(dian)(dian)(dian),从(cong)而使得Vgs 近(jin)乎水平状态，Cgd 电(dian)(dian)(dian)容(rong)上(shang)电(dian)(dian)(dian)压(ya)增加,而DS电(dian)(dian)(dian)容(rong)上(shang)的电(dian)(dian)(dian)压(ya)继续减(jian)小(xiao)。
4）[t3-t4]区间,至(zhi)t3时(shi)刻,MOSFET的(de)(de)DS电(dian)(dian)(dian)压(ya)降(jiang)至(zhi)饱和导通时(shi)的(de)(de)电(dian)(dian)(dian)压(ya),Millier效应影响变小，Cgd 电(dian)(dian)(dian)容变小并和Cgs 电(dian)(dian)(dian)容一起由外部驱动电(dian)(dian)(dian)压(ya)充电(dian)(dian)(dian), Cgs 电(dian)(dian)(dian)容的(de)(de)电(dian)(dian)(dian)压(ya)上升,至(zhi)t4时(shi)刻为止.此时(shi)C gs 电(dian)(dian)(dian)容电(dian)(dian)(dian)压(ya)已达稳态(tai),DS间电(dian)(dian)(dian)压(ya)也达最小，MOSFET完全开启。
俗称(cheng)耐(nai)压，至少(shao)应(ying)该为(wei)主绕组的3倍，需求留意的是(shi)，主绕组的电(dian)压指的是(shi)图2.6中(zhong)的N2或者N3，而(er)不是(shi)二者相加(jia)。详(xiang)细而(er)言，图中(zhong)为(wei)10.5V，因而(er)Q1、Q2的电(dian)压规格至少(shao)为(wei)31.5V，思索到10%的动摇和1.5倍的保险系(xi)数(shu)，则电(dian)压规格不应(ying)该低于31.5 X 1.1X 1.5＝52V。图中(zhong)的2SK2313的电(dian)压规格为(wei)60v，契合请(qing)求。
其次，依据(ju)普通经(jing)历，电(dian)压(ya)规(gui)格超越200V的(de)VMOS，饱和导(dao)通电(dian)阻的(de)优势就不(bu)明显了(le)，而(er)本钱却比二极管高得多，电(dian)路也复(fu)杂。因而(er)，用(yong)作同步整流时(shi)，主绕组的(de)最(zui)高电(dian)压(ya)不(bu)应(ying)该高于40V。
这个问题主(zhu)要(yao)与最(zui)(zui)大耗散功率(lv)有关，由于计(ji)算办(ban)法复杂并且(qie)需求实(shi)验停止验证，因(yin)而也能够(gou)直接用(yong)理(li)论办(ban)法进行(xing)肯定，即在实(shi)践(jian)的(de)(de)工(gong)(gong)(gong)作环(huan)境中(zhong)，依照最(zui)(zui)极端(duan)的(de)(de)最(zui)(zui)高(gao)环(huan)境温(wen)度，比方夏(xia)天比拟热的(de)(de)温(wen)度，如35℃，依据实(shi)践(jian)所(suo)需求的(de)(de)工(gong)(gong)(gong)作电(dian)流，接上(shang)(shang)适宜的(de)(de)假(jia)负载(zai)，连续工(gong)(gong)(gong)作2小时左右，假(jia)如MOS管散热片(TAB)不烫(tang)手，就根(gen)本上(shang)(shang)能够(gou)运用(yong)。这个办(ban)法固然(ran)粗略，但是(shi)很简单适用(yong)。
越小(xiao)越好，典型(xing)值最好小(xiao)于10mQ，这个数值以从(cong)技(ji)术手册上查到。
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