利盈娱乐(中国)创新平台有限公司

普通状况下普遍用于高端驱动的MOS,导通时需求是栅极电压大于源极电压。而高端驱动的MOS管导通时源极电压与漏极电压（VCC）相同，所以这时栅极电压要比VCC大4V或10V.假如在同一个系统里，要得到比VCC大的电压，就要特地的升压电路了。很多马达驱动器都集成了电荷泵，要留意的是应该选择适宜的外接电容，以得到足够的短路电流去驱动MOS管。

MOS管(guan)是电压驱动，按理(li)说只需栅(zha)(zha)(zha)极(ji)(ji)电(dian)(dian)(dian)压(ya)到到开(kai)(kai)启电(dian)(dian)(dian)压(ya)就能导(dao)(dao)通(tong)(tong)(tong)(tong)DS,栅(zha)(zha)(zha)极(ji)(ji)串(chuan)多(duo)大(da)电(dian)(dian)(dian)阻均能导(dao)(dao)通(tong)(tong)(tong)(tong)。但假如请求开(kai)(kai)关频(pin)率较高(gao)(gao)时，栅(zha)(zha)(zha)对地(di)或(huo)VCC能够看做是一个电(dian)(dian)(dian)容，关于一个电(dian)(dian)(dian)容来说，串(chuan)的电(dian)(dian)(dian)阻越(yue)大(da)，栅(zha)(zha)(zha)极(ji)(ji)到达导(dao)(dao)通(tong)(tong)(tong)(tong)电(dian)(dian)(dian)压(ya)时间(jian)越(yue)长(zhang)，MOS处于半导(dao)(dao)通(tong)(tong)(tong)(tong)状态(tai)时间(jian)也越(yue)长(zhang)，在半导(dao)(dao)通(tong)(tong)(tong)(tong)状态(tai)内阻较大(da)，发热(re)也会增大(da)，极(ji)(ji)易(yi)损坏(huai)MOS,所以高(gao)(gao)频(pin)时栅(zha)(zha)(zha)极(ji)(ji)栅(zha)(zha)(zha)极(ji)(ji)串(chuan)的电(dian)(dian)(dian)阻不但要(yao)小，普通(tong)(tong)(tong)(tong)要(yao)加(jia)前置驱动电(dian)(dian)(dian)路的。下面(mian)我们先来理(li)解一下MOS管(guan)开(kai)(kai)关的根底(di)学(xue)问。

MOS管的开关特性(xing)

一、静态特性
MOS管作为开关元(yuan)(yuan)件，同(tong)样是工作在截(jie)止或(huo)导通两种(zhong)状(zhuang)态(tai)。由(you)(you)于MOS管是电压控制(zhi)元(yuan)(yuan)件，所以主要由(you)(you)栅源电压uGS决议其工作状(zhuang)态(tai)。　　工作特性如下：

 uGS<开启电(dian)压UT:MOS管(guan)工作(zuo)在(zai)截止区，漏(lou)源电(dian)流(liu)iDS根本为0,输(shu)出电(dian)压uDS≈UDD,MOS管(guan)处(chu)于(yu)“断开”状态，其(qi)等效电(dian)路如下图所示。

uGS>开启电压UT:MOS管(guan)(guan)(guan)工作(zuo)在导(dao)通(tong)区，漏源电流(liu)iDS=UDD/（RD+rDS）。其中，rDS为MOS管(guan)(guan)(guan)导(dao)通(tong)时(shi)的漏源电阻。输出电压UDS=UDD·rDS/（RD+rDS），假如(ru)rDS《RD,则uDS≈0V,MOS管(guan)(guan)(guan)处于“接(jie)通(tong)”状态，其等效电路如(ru)上图（c）所示。

二、动态特性
MOS管在导通(tong)与截(jie)止(zhi)两种状态(tai)发作转换时(shi)同(tong)样存(cun)在过渡过程，但其动态(tai)特性(xing)主(zhu)要取决于与电(dian)路(lu)有(you)关的杂散电(dian)容(rong)充、放电(dian)所需的时(shi)间，而管子(zi)自身导通(tong)和(he)(he)(he)截(jie)止(zhi)时(shi)电(dian)荷(he)积(ji)聚和(he)(he)(he)消散的时(shi)间是很(hen)小的。下图 （a）和(he)(he)(he)（b）分别给(ji)出了一个NMOS管组成(cheng)的电(dian)路(lu)及其动态(tai)特性(xing)表示图。

NMOS管动(dong)态(tai)特性表(biao)示(shi)图

当(dang)输入(ru)电压(ya)ui由(you)高变(bian)低(di)，MOS管由(you)导通状(zhuang)态转换(huan)为(wei)截止(zhi)(zhi)状(zhuang)态时(shi)，电源UDD经(jing)过RD向杂散(san)电容(rong)CL充(chong)电，充(chong)电时(shi)间常数τ1=RDCL.所以，输出电压(ya)uo要经(jing)过一定延(yan)时(shi)才由(you)低(di)电平变(bian)为(wei)高电平；当(dang)输入(ru)电压(ya)ui由(you)低(di)变(bian)高，MOS管由(you)截止(zhi)(zhi)状(zhuang)态转换(huan)为(wei)导通状(zhuang)态时(shi)，杂散(san)电容(rong)CL上的电荷经(jing)过rDS停止(zhi)(zhi)放(fang)电，其放(fang)电时(shi)间常数τ2≈rDSCL.可见，输出电压(ya)Uo也要经(jing)过一定延(yan)时(shi)才干(gan)转变(bian)成(cheng)低(di)电平。但(dan)由(you)于rDS比(bi)RD小得多(duo)，所以，由(you)截止(zhi)(zhi)到(dao)导通的转换(huan)时(shi)间比(bi)由(you)导通到(dao)截止(zhi)(zhi)的转换(huan)时(shi)间要短(duan)。

由于MOS管(guan)导通时(shi)的(de)漏源电(dian)(dian)(dian)(dian)阻(zu)(zu)(zu)rDS比(bi)晶(jing)体(ti)三极管(guan)的(de)饱和电(dian)(dian)(dian)(dian)阻(zu)(zu)(zu)rCES要(yao)大(da)得多(duo)，漏极外接电(dian)(dian)(dian)(dian)阻(zu)(zu)(zu)RD也(ye)比(bi)晶(jing)体(ti)管(guan)集电(dian)(dian)(dian)(dian)极电(dian)(dian)(dian)(dian)阻(zu)(zu)(zu)RC大(da)，所以，MOS管(guan)的(de)充(chong)(chong)、放电(dian)(dian)(dian)(dian)时(shi)间较长，使(shi)MOS管(guan)的(de)开关速(su)(su)度(du)比(bi)晶(jing)体(ti)三极管(guan)的(de)开关速(su)(su)度(du)低。不过(guo)，在CMOS电(dian)(dian)(dian)(dian)路中，由于充(chong)(chong)电(dian)(dian)(dian)(dian)电(dian)(dian)(dian)(dian)路和放电(dian)(dian)(dian)(dian)电(dian)(dian)(dian)(dian)路都(dou)(dou)是低阻(zu)(zu)(zu)电(dian)(dian)(dian)(dian)路，因而(er)(er)，其充(chong)(chong)、放电(dian)(dian)(dian)(dian)过(guo)程(cheng)都(dou)(dou)比(bi)拟(ni)快，从而(er)(er)使(shi)CMOS电(dian)(dian)(dian)(dian)路有(you)较高的(de)开关速(su)(su)度(du)。

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