mos管(guan)电(dian)子开(kai)关电(dian)路(lu)图-mos管(guan)电(dian)子开(kai)关电(dian)路(lu)基(ji)本知识(shi)及特点、导通性等详解-KIA MOS管(guan)
信息来源(yuan)：本站 日期：2018-09-04
MOS管(guan)开关电路(lu)是利用(yong)MOS管(guan)栅(zha)极（g）控制MOS管(guan)源极（s）和漏极（d）通断的原理(li)构(gou)造的电路(lu)。因MOS管(guan)分为(wei)N沟(gou)道(dao)与(yu)P沟(gou)道(dao)，所以开关电路(lu)也主要分为(wei)两(liang)种。
一(yi)般情况下(xia)普遍用于(yu)高端驱动(dong)的(de)(de)MOS，导通(tong)时(shi)(shi)需要(yao)(yao)是栅极电压(ya)(ya)大(da)于(yu)源极电压(ya)(ya)。而高端驱动(dong)的(de)(de)MOS管(guan)导通(tong)时(shi)(shi)源极电压(ya)(ya)与漏极电压(ya)(ya)（VCC）相同，所以这时(shi)(shi)栅极电压(ya)(ya)要(yao)(yao)比VCC大(da)4V或(huo)10V.如(ru)果在同一(yi)个系统里，要(yao)(yao)得到比VCC大(da)的(de)(de)电压(ya)(ya)，就(jiu)要(yao)(yao)专(zhuan)门的(de)(de)升压(ya)(ya)电路了(le)。很多马达(da)驱动(dong)器都集成了(le)电荷泵，要(yao)(yao)注意的(de)(de)是应该选择合适(shi)的(de)(de)外接电容(rong)，以得到足够(gou)的(de)(de)短(duan)路电流(liu)去驱动(dong)MOS管(guan)。
MOS管是电(dian)(dian)压(ya)驱(qu)动，按理说只要(yao)栅(zha)(zha)极(ji)(ji)(ji)(ji)电(dian)(dian)压(ya)到到开(kai)启(qi)电(dian)(dian)压(ya)就能(neng)导通(tong)DS，栅(zha)(zha)极(ji)(ji)(ji)(ji)串多(duo)大(da)(da)电(dian)(dian)阻(zu)均能(neng)导通(tong)。但如(ru)果要(yao)求(qiu)开(kai)关频率较高(gao)时，栅(zha)(zha)对(dui)地(di)或VCC可以看(kan)做是一个电(dian)(dian)容，对(dui)于一个电(dian)(dian)容来说，串的(de)电(dian)(dian)阻(zu)越(yue)大(da)(da)，栅(zha)(zha)极(ji)(ji)(ji)(ji)达到导通(tong)电(dian)(dian)压(ya)时间(jian)越(yue)长，MOS处(chu)于半(ban)导通(tong)状态时间(jian)也越(yue)长，在(zai)半(ban)导通(tong)状态内阻(zu)较大(da)(da)，发热也会增大(da)(da)，极(ji)(ji)(ji)(ji)易(yi)损(sun)坏(huai)MOS，所以高(gao)频时栅(zha)(zha)极(ji)(ji)(ji)(ji)栅(zha)(zha)极(ji)(ji)(ji)(ji)串的(de)电(dian)(dian)阻(zu)不但要(yao)小(xiao)，一般要(yao)加前(qian)置驱(qu)动电(dian)(dian)路的(de)。
电(dian)(dian)子开关电(dian)(dian)源(yuan)的电(dian)(dian)路组成如下：
开关电(dian)(dian)(dian)(dian)源的主要电(dian)(dian)(dian)(dian)路(lu)(lu)是由(you)输(shu)(shu)入(ru)电(dian)(dian)(dian)(dian)磁干扰滤波(bo)器（EMI）、整流(liu)滤波(bo)电(dian)(dian)(dian)(dian)路(lu)(lu)、功率(lv)变换电(dian)(dian)(dian)(dian)路(lu)(lu)、PWM控(kong)制(zhi)器电(dian)(dian)(dian)(dian)路(lu)(lu)、输(shu)(shu)出(chu)(chu)整流(liu)滤波(bo)电(dian)(dian)(dian)(dian)路(lu)(lu)组(zu)成(cheng)。IC根据输(shu)(shu)出(chu)(chu)电(dian)(dian)(dian)(dian)压和电(dian)(dian)(dian)(dian)流(liu)时刻调整着⑥脚锯形波(bo)占空比(bi)的大小，从(cong)而不乱了整机的输(shu)(shu)出(chu)(chu)电(dian)(dian)(dian)(dian)流(liu)和电(dian)(dian)(dian)(dian)压。从(cong)R3测得的电(dian)(dian)(dian)(dian)流(liu)峰值信号介入(ru)当前工作周波(bo)的占空比(bi)控(kong)制(zhi)，因此(ci)是当前工作周波(bo)的电(dian)(dian)(dian)(dian)流(liu)限制(zhi)。
Q1的栅(zha)极受控电(dian)压(ya)(ya)为锯(ju)形(xing)波，当其占(zhan)空(kong)比越(yue)大(da)时，Q1导通(tong)时间越(yue)长(zhang)，变(bian)(bian)压(ya)(ya)器(qi)(qi)所储(chu)存(cun)的能(neng)(neng)量也就(jiu)越(yue)多；当Q1截止时，变(bian)(bian)压(ya)(ya)器(qi)(qi)通(tong)过D1、D2、R5、R4、C3开释能(neng)(neng)量，同时也达(da)到(dao)了磁场复位(wei)的目的，为变(bian)(bian)压(ya)(ya)器(qi)(qi)的下(xia)一(yi)(yi)次存(cun)储(chu)、传递能(neng)(neng)量做好(hao)了预备。在开关管Q1关断时，变(bian)(bian)压(ya)(ya)器(qi)(qi)的原边(bian)线圈易产生尖(jian)峰(feng)电(dian)压(ya)(ya)和(he)(he)尖(jian)峰(feng)电(dian)流，这(zhei)些元件组合一(yi)(yi)起(qi)，能(neng)(neng)很好(hao)地(di)吸收(shou)尖(jian)峰(feng)电(dian)压(ya)(ya)和(he)(he)电(dian)流。
1:输(shu)入(ru)滤波(bo)电(dian)(dian)(dian)路：C1、L1、C2组(zu)成的双π型滤波(bo)网络主要是(shi)对(dui)输(shu)入(ru)电(dian)(dian)(dian)源的电(dian)(dian)(dian)磁噪(zao)声及杂波(bo)信号进(jin)行(xing)按捺(na)，防止对(dui)电(dian)(dian)(dian)源干扰，同时也(ye)防止电(dian)(dian)(dian)源本身产生(sheng)的高(gao)频杂波(bo)对(dui)电(dian)(dian)(dian)网干扰。Z1通常将MOS管的GS电(dian)(dian)(dian)压(ya)限制(zhi)在(zai)18V以下，从而保护了MOS管。因瞬时能(neng)量全消耗在(zai)RT1电(dian)(dian)(dian)阻上，一定时间后温度升高(gao)后RT1阻值减（RT1是(shi)负温系数元(yuan)件(jian)），这时它消耗的能(neng)量非常小，后级电(dian)(dian)(dian)路可正(zheng)常工作。C3、C4 为(wei)安(an)规电(dian)(dian)(dian)容(rong)，L2、L3为(wei)差模(mo)电(dian)(dian)(dian)感。
2:输入(ru)滤波(bo)电路：C1、L1、C2、C3组成的双π型(xing)滤波(bo)网(wang)络主要(yao)是对输入(ru)电源(yuan)的电磁噪声及杂波(bo)信号进(jin)行按捺，防(fang)止对电源(yuan)干扰，同(tong)时也(ye)防(fang)止电源(yuan)本身产生的高频杂波(bo)对电网(wang)干扰。
3:工作原理：R4、C3、R5、R6、C4、D1、D2组成(cheng)缓冲器，和开(kai)关MOS管(guan)并接，使开(kai)关管(guan)电(dian)(dian)压应力减少，EMI减少，不发生(sheng)二次击穿。辅助(zhu)电(dian)(dian)路有输入过欠压保(bao)(bao)护电(dian)(dian)路、输出过欠压保(bao)(bao)护电(dian)(dian)路、输出过流保(bao)(bao)护电(dian)(dian)路、输出短路保(bao)(bao)护电(dian)(dian)路等。
MOSFET管是FET的一种（另一种是JFET），可以被制造成增强型(xing)(xing)或(huo)耗尽(jin)型(xing)(xing)，P沟道(dao)或(huo)N沟道(dao)共4种类型(xing)(xing)，但(dan)实际应用(yong)(yong)的只有(you)增强型(xing)(xing)的N沟道(dao)MOS管和(he)增强型(xing)(xing)的P沟道(dao)MOS管，所以通(tong)(tong)常提到NMOS，或(huo)者PMOS指(zhi)的就是这两(liang)种。至于为什么(me)不使用(yong)(yong)耗尽(jin)型(xing)(xing)的MOS管，不建议(yi)刨根问(wen)底。对于这两(liang)种增强型(xing)(xing)MOS管，比较常用(yong)(yong)的是NMOS.原(yuan)因是导(dao)通(tong)(tong)电阻小，且容易(yi)制造。所以开关电源和(he)马达驱动的应用(yong)(yong)中，一般都用(yong)(yong)NMOS.下面的介绍(shao)中，也多(duo)以NMOS为主(zhu)。
MOS管的(de)三个(ge)管脚之(zhi)间(jian)(jian)有寄(ji)(ji)生电(dian)容存在(zai)，这不(bu)是我们需要的(de)，而是由于制(zhi)造工(gong)艺限制(zhi)产生的(de)。寄(ji)(ji)生电(dian)容的(de)存在(zai)使得在(zai)设(she)计(ji)或(huo)选择驱动(dong)电(dian)路的(de)时候(hou)要麻烦一些(xie)，但没有办(ban)法避免，后边再详细介(jie)绍。在(zai)MOS管原(yuan)理图上可以看到(dao)，漏极(ji)(ji)和源(yuan)极(ji)(ji)之(zhi)间(jian)(jian)有一个(ge)寄(ji)(ji)生二(er)极(ji)(ji)管。这个(ge)叫体二(er)极(ji)(ji)管，在(zai)驱动(dong)感(gan)性负载（如马达），这个(ge)二(er)极(ji)(ji)管很重要。顺便说一句，体二(er)极(ji)(ji)管只(zhi)在(zai)单个(ge)的(de)MOS管中存在(zai)，在(zai)集成电(dian)路芯片内部通常是没有的(de)。
导(dao)通的意思是作为开关，相当于开关闭合。
NMOS的特性，Vgs大于(yu)一定的值就(jiu)会导通，适合(he)用(yong)于(yu)源极(ji)接地时的情况（低端驱动），只要(yao)栅极(ji)电压达到4V或10V就(jiu)可(ke)以了。
PMOS的(de)(de)特性(xing)，Vgs小于(yu)一(yi)定的(de)(de)值就会导通，适合用(yong)于(yu)源极接VCC时的(de)(de)情况（高端(duan)(duan)驱动）。但是，虽然PMOS可以很方(fang)便地用(yong)作高端(duan)(duan)驱动，但由于(yu)导通电阻大，价格(ge)贵，替换种类(lei)少等原因，在高端(duan)(duan)驱动中(zhong)，通常还是使用(yong)NMOS.
不(bu)管(guan)(guan)是NMOS还是PMOS，导(dao)通后都有(you)导(dao)通电阻(zu)(zu)存在(zai)(zai)(zai)，这样电流就会在(zai)(zai)(zai)这个(ge)电阻(zu)(zu)上消耗能(neng)量，这部分消耗的(de)(de)(de)能(neng)量叫做导(dao)通损耗。选择(ze)导(dao)通电阻(zu)(zu)小(xiao)的(de)(de)(de)MOS管(guan)(guan)会减(jian)小(xiao)导(dao)通损耗。现在(zai)(zai)(zai)的(de)(de)(de)小(xiao)功率MOS管(guan)(guan)导(dao)通电阻(zu)(zu)一般(ban)在(zai)(zai)(zai)几十毫(hao)(hao)欧左右，几毫(hao)(hao)欧的(de)(de)(de)也有(you)。
MOS在(zai)导通(tong)和截止的(de)(de)(de)时候，一定不是(shi)(shi)在(zai)瞬间完成的(de)(de)(de)。MOS两端的(de)(de)(de)电压有一个(ge)下降(jiang)的(de)(de)(de)过程(cheng)，流(liu)过的(de)(de)(de)电流(liu)有一个(ge)上(shang)升的(de)(de)(de)过程(cheng)，在(zai)这段时间内，MOS管的(de)(de)(de)损(sun)失是(shi)(shi)电压和电流(liu)的(de)(de)(de)乘积，叫做开(kai)关(guan)损(sun)失。通(tong)常开(kai)关(guan)损(sun)失比导通(tong)损(sun)失大得多，而且开(kai)关(guan)频率越快(kuai)，损(sun)失也(ye)越大。
导(dao)通瞬间电压和电流的(de)乘积很(hen)大，造成的(de)损(sun)(sun)失也就很(hen)大。缩短开关(guan)时间，可(ke)以(yi)(yi)减小每次导(dao)通时的(de)损(sun)(sun)失;降低开关(guan)频率，可(ke)以(yi)(yi)减小单位时间内的(de)开关(guan)次数。这两种办法都可(ke)以(yi)(yi)减小开关(guan)损(sun)(sun)失。
跟双极性晶(jing)体管(guan)(guan)相比，一般认为使MOS管(guan)(guan)导通不需要(yao)电流，只(zhi)要(yao)GS电压高于一定的值，就可以(yi)了。这个很容易做到，但是，我们还(hai)需要(yao)速度。
在MOS管(guan)(guan)的(de)(de)(de)结构中可(ke)(ke)以(yi)看(kan)到，在GS，GD之间存(cun)在寄生电(dian)(dian)(dian)(dian)容(rong)(rong)，而MOS管(guan)(guan)的(de)(de)(de)驱动，实际上就是对(dui)(dui)电(dian)(dian)(dian)(dian)容(rong)(rong)的(de)(de)(de)充放(fang)电(dian)(dian)(dian)(dian)。对(dui)(dui)电(dian)(dian)(dian)(dian)容(rong)(rong)的(de)(de)(de)充电(dian)(dian)(dian)(dian)需要(yao)一(yi)(yi)个电(dian)(dian)(dian)(dian)流，因为对(dui)(dui)电(dian)(dian)(dian)(dian)容(rong)(rong)充电(dian)(dian)(dian)(dian)瞬(shun)间可(ke)(ke)以(yi)把电(dian)(dian)(dian)(dian)容(rong)(rong)看(kan)成(cheng)短(duan)路，所以(yi)瞬(shun)间电(dian)(dian)(dian)(dian)流会比较大。选择/设计MOS管(guan)(guan)驱动时(shi)第一(yi)(yi)要(yao)注意的(de)(de)(de)是可(ke)(ke)提(ti)供瞬(shun)间短(duan)路电(dian)(dian)(dian)(dian)流的(de)(de)(de)大小。
而在(zai)进行MOSFET的(de)选择时(shi)，因为(wei)MOSFET有两大(da)类型(xing)：N沟道(dao)和P沟道(dao)。在(zai)功率系统中，MOSFET可(ke)被看成电(dian)(dian)气开关(guan)(guan)(guan)(guan)。当(dang)(dang)在(zai)N沟道(dao)MOSFET的(de)栅极(ji)(ji)(ji)和源(yuan)极(ji)(ji)(ji)间(jian)加上正电(dian)(dian)压(ya)时(shi)，其开关(guan)(guan)(guan)(guan)导(dao)通。导(dao)通时(shi)，电(dian)(dian)流(liu)(liu)可(ke)经开关(guan)(guan)(guan)(guan)从漏极(ji)(ji)(ji)流(liu)(liu)向源(yuan)极(ji)(ji)(ji)。漏极(ji)(ji)(ji)和源(yuan)极(ji)(ji)(ji)之(zhi)间(jian)存(cun)在(zai)一个内阻(zu)，称(cheng)为(wei)导(dao)通电(dian)(dian)阻(zu)RDS（ON）。必须清楚(chu)MOSFET的(de)栅极(ji)(ji)(ji)是个高阻(zu)抗端，因此(ci)，总是要(yao)在(zai)栅极(ji)(ji)(ji)加上一个电(dian)(dian)压(ya)。这就(jiu)是后面介绍电(dian)(dian)路图中栅极(ji)(ji)(ji)所接电(dian)(dian)阻(zu)至地。如果栅极(ji)(ji)(ji)为(wei)悬空，器(qi)件(jian)将不能按设计(ji)意图工作(zuo)，并可(ke)能在(zai)不恰(qia)当(dang)(dang)的(de)时(shi)刻导(dao)通或关(guan)(guan)(guan)(guan)闭(bi)(bi)，导(dao)致系统产生(sheng)潜在(zai)的(de)功率损(sun)耗。当(dang)(dang)源(yuan)极(ji)(ji)(ji)和栅极(ji)(ji)(ji)间(jian)的(de)电(dian)(dian)压(ya)为(wei)零时(shi)，开关(guan)(guan)(guan)(guan)关(guan)(guan)(guan)(guan)闭(bi)(bi)，而电(dian)(dian)流(liu)(liu)停止通过器(qi)件(jian)。虽(sui)然(ran)这时(shi)器(qi)件(jian)已经关(guan)(guan)(guan)(guan)闭(bi)(bi)，但(dan)仍然(ran)有微(wei)小(xiao)电(dian)(dian)流(liu)(liu)存(cun)在(zai)，这称(cheng)之(zhi)为(wei)漏电(dian)(dian)流(liu)(liu)，即(ji)IDSS.
图中电(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)的(de)(de)(de)正电(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)通(tong)(tong)(tong)(tong)过开(kai)(kai)关S1接到场效应(ying)管(guan)Q1的(de)(de)(de)2脚(jiao)(jiao)源极(ji)(ji)(ji)(ji)，由于(yu)Q1是(shi)一个(ge)(ge)P沟道(dao)管(guan)，它(ta)的(de)(de)(de)1脚(jiao)(jiao)栅极(ji)(ji)(ji)(ji)通(tong)(tong)(tong)(tong)过R20电(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)提(ti)供(gong)一个(ge)(ge)正电(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)位电(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)压(ya)(ya)，所以不(bu)能(neng)(neng)通(tong)(tong)(tong)(tong)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)，电(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)压(ya)(ya)不(bu)能(neng)(neng)继续通(tong)(tong)(tong)(tong)过，3v稳压(ya)(ya)IC输(shu)入(ru)脚(jiao)(jiao)得不(bu)到电(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)压(ya)(ya)所以就(jiu)(jiu)不(bu)能(neng)(neng)工作(zuo)不(bu)开(kai)(kai)机(ji)(ji)！这(zhei)(zhei)时(shi)，如果我(wo)们按(an)下SW1开(kai)(kai)机(ji)(ji)按(an)键时(shi)，正电(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)通(tong)(tong)(tong)(tong)过按(an)键、R11、R23、D4加(jia)到三(san)(san)极(ji)(ji)(ji)(ji)管(guan)Q2的(de)(de)(de)基极(ji)(ji)(ji)(ji)，三(san)(san)极(ji)(ji)(ji)(ji)管(guan)Q2的(de)(de)(de)基极(ji)(ji)(ji)(ji)得到一个(ge)(ge)正电(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)位，三(san)(san)极(ji)(ji)(ji)(ji)管(guan)导(dao)(dao)通(tong)(tong)(tong)(tong)（前面讲到三(san)(san)极(ji)(ji)(ji)(ji)管(guan)的(de)(de)(de)时(shi)候已经讲过），由于(yu)三(san)(san)极(ji)(ji)(ji)(ji)管(guan)的(de)(de)(de)发射极(ji)(ji)(ji)(ji)直接接地，三(san)(san)极(ji)(ji)(ji)(ji)管(guan)Q2导(dao)(dao)通(tong)(tong)(tong)(tong)就(jiu)(jiu)相当于(yu)Q1的(de)(de)(de)栅极(ji)(ji)(ji)(ji)直接接地，加(jia)在它(ta)上(shang)面的(de)(de)(de)通(tong)(tong)(tong)(tong)过R20电(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)的(de)(de)(de)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)压(ya)(ya)就(jiu)(jiu)直接入(ru)了(le)地，Q1的(de)(de)(de)栅极(ji)(ji)(ji)(ji)就(jiu)(jiu)从高(gao)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)位变(bian)为(wei)低电(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)位，Q1导(dao)(dao)通(tong)(tong)(tong)(tong)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)就(jiu)(jiu)从Q1同过加(jia)到3v稳压(ya)(ya)IC的(de)(de)(de)输(shu)入(ru)脚(jiao)(jiao)，3v稳压(ya)(ya)IC就(jiu)(jiu)是(shi)那个(ge)(ge)U1输(shu)出(chu)3v的(de)(de)(de)工作(zuo)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)压(ya)(ya)vcc供(gong)给主(zhu)控，主(zhu)控通(tong)(tong)(tong)(tong)过复位清0，读取固件(jian)程(cheng)序检测等一系(xi)列动作(zuo)，输(shu)处一个(ge)(ge)控制(zhi)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)压(ya)(ya)到PWR_ON再通(tong)(tong)(tong)(tong)过R24、R13分(fen)压(ya)(ya)送到Q2的(de)(de)(de)基极(ji)(ji)(ji)(ji)，保(bao)持(chi)Q2一直处于(yu)导(dao)(dao)通(tong)(tong)(tong)(tong)状(zhuang)态(tai)，即使你松开(kai)(kai)开(kai)(kai)机(ji)(ji)键断开(kai)(kai)Q1的(de)(de)(de)基极(ji)(ji)(ji)(ji)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)压(ya)(ya)，这(zhei)(zhei)时(shi)候有(you)主(zhu)控送来的(de)(de)(de)控制(zhi)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)压(ya)(ya)保(bao)持(chi)着，Q2也就(jiu)(jiu)一直能(neng)(neng)够处于(yu)导(dao)(dao)通(tong)(tong)(tong)(tong)状(zhuang)态(tai)，Q1就(jiu)(jiu)能(neng)(neng)源源不(bu)断的(de)(de)(de)给3v稳压(ya)(ya)IC提(ti)供(gong)工作(zuo)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)压(ya)(ya)！SW1还(hai)同时(shi)通(tong)(tong)(tong)(tong)过R11、R30两个(ge)(ge)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)的(de)(de)(de)分(fen)压(ya)(ya)，给主(zhu)控PLAYON脚(jiao)(jiao)送去时(shi)间长短、次(ci)数不(bu)同的(de)(de)(de)控制(zhi)信号，主(zhu)控通(tong)(tong)(tong)(tong)过固件(jian)鉴别是(shi)播放、暂停(ting)、开(kai)(kai)机(ji)(ji)、关机(ji)(ji)而输(shu)出(chu)不(bu)同的(de)(de)(de)结(jie)果给相应(ying)的(de)(de)(de)控制(zhi)点(dian)，以达(da)到不(bu)同的(de)(de)(de)工作(zuo)状(zhuang)态(tai)！
下图是(shi)两种(zhong)MOS管的(de)典型应用(yong)：其(qi)中第(di)一(yi)种(zhong)NMOS管为(wei)(wei)高(gao)电平(ping)(ping)导(dao)通(tong)，低电平(ping)(ping)截断(duan)，Drain端接后面(mian)电路的(de)接地(di)端；第(di)二(er)种(zhong)为(wei)(wei)PMOS管典型开关电路，为(wei)(wei)高(gao)电平(ping)(ping)断(duan)开，低电平(ping)(ping)导(dao)通(tong)，Drain端接后面(mian)电路的(de)VCC端。
驱(qu)动电路(lu)加(jia)速MOS管关(guan)断时间，为(wei)了满足如图(tu)所(suo)示高端MOS管的(de)(de)驱(qu)动，经常会采(cai)用变压(ya)器驱(qu)动，有时(shi)为(wei)了满足安全隔(ge)离也使用变压(ya)器驱(qu)动。其中(zhong)R1目的(de)(de)是抑制PCB板上寄生的(de)(de)电感(gan)与C1形(xing)成LC振荡(dang)，C1的(de)(de)目的(de)(de)是隔(ge)开直流，通过交流，同时(shi)也能防止磁(ci)芯饱和(he)。
如图所示为(wei)常用的小功率(lv)驱动(dong)电(dian)路，简单可靠成本低(di)。适(shi)用于不(bu)要(yao)求隔(ge)(ge)离的小功率(lv)开关设备。如图所示驱动(dong)电(dian)路开关速(su)度很快，驱动(dong)能力(li)强，为(wei)防(fang)止(zhi)两个MOSFET管直通，通常串接(jie)一个0.5～1Ω小电(dian)阻用于限流，该电(dian)路适(shi)用于不(bu)要(yao)求隔(ge)(ge)离的中功率(lv)开关设备。这(zhei)两种电(dian)路特点是(shi)结构简单。
功率MOSFET属于(yu)(yu)电(dian)(dian)压(ya)型控制(zhi)器件，只要(yao)栅(zha)(zha)极和(he)源(yuan)极之间施(shi)加的电(dian)(dian)压(ya)超过(guo)其阀值电(dian)(dian)压(ya)就会导通。由于(yu)(yu)MOSFET存在(zai)(zai)结(jie)电(dian)(dian)容，关(guan)断(duan)时其漏(lou)源(yuan)两端(duan)(duan)电(dian)(dian)压(ya)的突然(ran)上(shang)升将会通过(guo)结(jie)电(dian)(dian)容在(zai)(zai)栅(zha)(zha)源(yuan)两端(duan)(duan)产生干(gan)扰电(dian)(dian)压(ya)。常用的互补(bu)驱动电(dian)(dian)路(lu)的关(guan)断(duan)回路(lu)阻(zu)抗(kang)小，关(guan)断(duan)速度较(jiao)快(kuai)，但它不能提供(gong)负压(ya)，故抗(kang)干(gan)扰性较(jiao)差。为了提高电(dian)(dian)路(lu)的抗(kang)干(gan)扰性，可在(zai)(zai)此(ci)种驱动电(dian)(dian)路(lu)的基础上(shang)增加一(yi)级有V1、V2、R组成的电(dian)(dian)路(lu)，产生一(yi)个负压(ya)，电(dian)(dian)路(lu)原理(li)图如图所(suo)示。
正激(ji)式(shi)驱动电路
电(dian)(dian)路(lu)(lu)原理(li)如(ru)(ru)图(tu)所(suo)示，N3为去磁(ci)绕组，S2为所(suo)驱(qu)(qu)(qu)动(dong)的(de)(de)功率(lv)(lv)管。R2为防止功率(lv)(lv)管栅极(ji)(ji)(ji)、源(yuan)极(ji)(ji)(ji)端电(dian)(dian)压振荡(dang)(dang)的(de)(de)一(yi)个阻(zu)(zu)尼电(dian)(dian)阻(zu)(zu)。因(yin)不要求漏(lou)感较(jiao)小(xiao)，且从(cong)速(su)度(du)(du)(du)方面考虑(lv)，一(yi)般R2较(jiao)小(xiao)，故(gu)在分析中(zhong)忽略不计(ji)。其等效(xiao)电(dian)(dian)路(lu)(lu)图(tu)如(ru)(ru)图(tu)所(suo)示脉冲不要求的(de)(de)副(fu)边并联一(yi)电(dian)(dian)阻(zu)(zu)R1，它做为正(zheng)(zheng)激变(bian)(bian)(bian)换器的(de)(de)假(jia)负载，用于(yu)消除关(guan)断期间输出电(dian)(dian)压发(fa)生振荡(dang)(dang)而(er)误导(dao)通。同时(shi)(shi)它还(hai)可以作(zuo)为功率(lv)(lv)MOSFET关(guan)断时(shi)(shi)的(de)(de)能量泄放回(hui)路(lu)(lu)。该驱(qu)(qu)(qu)动(dong)电(dian)(dian)路(lu)(lu)的(de)(de)导(dao)通速(su)度(du)(du)(du)主(zhu)要与(yu)被驱(qu)(qu)(qu)动(dong)的(de)(de)S2栅极(ji)(ji)(ji)、源(yuan)极(ji)(ji)(ji)等效(xiao)输入电(dian)(dian)容的(de)(de)大小(xiao)、S1的(de)(de)驱(qu)(qu)(qu)动(dong)信(xin)号的(de)(de)速(su)度(du)(du)(du)以及S1所(suo)能提供(gong)的(de)(de)电(dian)(dian)流大小(xiao)有(you)关(guan)。由仿真(zhen)及分析可知，占空比D越(yue)(yue)小(xiao)、R1越(yue)(yue)大、L越(yue)(yue)大，磁(ci)化电(dian)(dian)流越(yue)(yue)小(xiao)，U1值越(yue)(yue)小(xiao)，关(guan)断速(su)度(du)(du)(du)越(yue)(yue)慢。该电(dian)(dian)路(lu)(lu)具有(you)以下(xia)优点：①电(dian)(dian)路(lu)(lu)结构简单(dan)可靠，实现了隔离驱(qu)(qu)(qu)动(dong)。②只(zhi)需单(dan)电(dian)(dian)源(yuan)即可提供(gong)导(dao)通时(shi)(shi)的(de)(de)正(zheng)(zheng)、关(guan)断时(shi)(shi)负压。③占空比固定时(shi)(shi)，通过(guo)合(he)理(li)的(de)(de)参数设计(ji)，此驱(qu)(qu)(qu)动(dong)电(dian)(dian)路(lu)(lu)也具有(you)较(jiao)快(kuai)的(de)(de)开关(guan)速(su)度(du)(du)(du)。该电(dian)(dian)路(lu)(lu)存在的(de)(de)缺点：一(yi)是由于(yu)隔离变(bian)(bian)(bian)压器副(fu)边需要噎(ye)嗝(ge)假(jia)负载防振荡(dang)(dang)，故(gu)电(dian)(dian)路(lu)(lu)损耗较(jiao)大;二是当占空比变(bian)(bian)(bian)化时(shi)(shi)关(guan)断速(su)度(du)(du)(du)变(bian)(bian)(bian)化较(jiao)大。脉宽较(jiao)窄时(shi)(shi)，由于(yu)是储存的(de)(de)能量减少导(dao)致MOSFET栅极(ji)(ji)(ji)的(de)(de)关(guan)断速(su)度(du)(du)(du)变(bian)(bian)(bian)慢。
有隔离变压器(qi)的互补(bu)驱(qu)动电(dian)路(lu)
如图所(suo)示，V1、V2为(wei)(wei)互补工作(zuo)，电(dian)容C起隔(ge)离直(zhi)流(liu)的(de)(de)作(zuo)用，T1为(wei)(wei)高频、高磁(ci)(ci)(ci)率的(de)(de)磁(ci)(ci)(ci)环或磁(ci)(ci)(ci)罐。导(dao)通(tong)时(shi)隔(ge)离变压(ya)(ya)器(qi)上(shang)的(de)(de)电(dian)压(ya)(ya)为(wei)(wei)（1-D）Ui、关断时(shi)为(wei)(wei)DUi，若主功(gong)率管S可(ke)靠导(dao)通(tong)电(dian)压(ya)(ya)为(wei)(wei)12V，而隔(ge)离变压(ya)(ya)器(qi)原副边匝比N1/N2为(wei)(wei)12/［（1-D）Ui］。为(wei)(wei)保证导(dao)通(tong)期间GS电(dian)压(ya)(ya)稳定C值可(ke)稍取大些。该电(dian)路具有以下(xia)优(you)点：
①电路(lu)结构简单可靠(kao)，具有(you)电气隔离作用。当脉宽(kuan)变化时，驱(qu)动的关断能力不会随着变化。
②该电(dian)(dian)路只需一(yi)个电(dian)(dian)源，即(ji)为(wei)单电(dian)(dian)源工(gong)作。隔(ge)直(zhi)电(dian)(dian)容(rong)C的作用(yong)可以(yi)在关断(duan)所驱动的管(guan)子(zi)时提供一(yi)个负压，从而加速(su)了功率管(guan)的关断(duan)，且(qie)有(you)较高的抗干扰(rao)能力(li)。
但该电(dian)(dian)(dian)(dian)路(lu)(lu)存在的(de)(de)一个(ge)较大(da)缺点是(shi)输(shu)出电(dian)(dian)(dian)(dian)压(ya)(ya)(ya)的(de)(de)幅值会随着占空(kong)比(bi)(bi)的(de)(de)变(bian)化(hua)而变(bian)化(hua)。当D较小(xiao)时，负向(xiang)电(dian)(dian)(dian)(dian)压(ya)(ya)(ya)小(xiao)，该电(dian)(dian)(dian)(dian)路(lu)(lu)的(de)(de)抗干扰性变(bian)差，且正向(xiang)电(dian)(dian)(dian)(dian)压(ya)(ya)(ya)较高，应该注意(yi)使其幅值不(bu)超过(guo)MOSFET栅极(ji)的(de)(de)允(yun)许(xu)电(dian)(dian)(dian)(dian)压(ya)(ya)(ya)。当D大(da)于0.5时驱动电(dian)(dian)(dian)(dian)压(ya)(ya)(ya)正向(xiang)电(dian)(dian)(dian)(dian)压(ya)(ya)(ya)小(xiao)于其负向(xiang)电(dian)(dian)(dian)(dian)压(ya)(ya)(ya)，此(ci)时应该注意(yi)使其负电(dian)(dian)(dian)(dian)压(ya)(ya)(ya)值不(bu)超过(guo)MOAFET栅极(ji)允(yun)许(xu)电(dian)(dian)(dian)(dian)压(ya)(ya)(ya)。所以(yi)该电(dian)(dian)(dian)(dian)路(lu)(lu)比(bi)(bi)较适用于占空(kong)比(bi)(bi)固定或占空(kong)比(bi)(bi)变(bian)化(hua)范围不(bu)大(da)以(yi)及占空(kong)比(bi)(bi)小(xiao)于0.5的(de)(de)场(chang)合。
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