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自举电路

自(zi)举(ju)电(dian)(dian)路(lu)(lu)也(ye)叫升(sheng)压(ya)电(dian)(dian)路(lu)(lu)，是(shi)利用自(zi)举(ju)升(sheng)压(ya)二极管，自(zi)举(ju)升(sheng)压(ya)电(dian)(dian)容(rong)等电(dian)(dian)子元件，使电(dian)(dian)容(rong)放(fang)电(dian)(dian)电(dian)(dian)压(ya)和电(dian)(dian)源(yuan)电(dian)(dian)压(ya)叠加，从而(er)使电(dian)(dian)压(ya)升(sheng)高．有的电(dian)(dian)路(lu)(lu)升(sheng)高的电(dian)(dian)压(ya)能达到(dao)数倍电(dian)(dian)源(yuan)电(dian)(dian)压(ya)。

MOS管自举电路原理

举(ju)个(ge)(ge)(ge)简单(dan)的(de)(de)(de)(de)例子：有(you)一个(ge)(ge)(ge)12V的(de)(de)(de)(de)电(dian)(dian)路，电(dian)(dian)路中(zhong)有(you)一个(ge)(ge)(ge)场效应管需(xu)要15V的(de)(de)(de)(de)驱动电(dian)(dian)压，这(zhei)个(ge)(ge)(ge)电(dian)(dian)压怎(zen)么弄(nong)出来？就是(shi)用(yong)(yong)自(zi)举(ju)。通常用(yong)(yong)一个(ge)(ge)(ge)电(dian)(dian)容(rong)(rong)和(he)一个(ge)(ge)(ge)二(er)极(ji)管，电(dian)(dian)容(rong)(rong)存储电(dian)(dian)荷，二(er)极(ji)管防止(zhi)电(dian)(dian)流倒灌，频(pin)率较高的(de)(de)(de)(de)时候，自(zi)举(ju)电(dian)(dian)路的(de)(de)(de)(de)电(dian)(dian)压就是(shi)电(dian)(dian)路输入的(de)(de)(de)(de)电(dian)(dian)压加上电(dian)(dian)容(rong)(rong)上的(de)(de)(de)(de)电(dian)(dian)压，起到升压的(de)(de)(de)(de)作用(yong)(yong)。

自(zi)(zi)举电(dian)(dian)路只是(shi)在实(shi)践(jian)中(zhong)定的名称，在理(li)论上没有这个概(gai)念。自(zi)(zi)举电(dian)(dian)路主要(yao)(yao)是(shi)在甲(jia)乙类单电(dian)(dian)源互补对称电(dian)(dian)路中(zhong)使(shi)用较为普遍。甲(jia)乙类单电(dian)(dian)源互补对称电(dian)(dian)路在理(li)论上可以(yi)使(shi)输出(chu)电(dian)(dian)压(ya)(ya)Vo达(da)到(dao)(dao)Vcc的一半(ban)，但在实(shi)际的测试(shi)中(zhong)，输出(chu)电(dian)(dian)压(ya)(ya)远达(da)不到(dao)(dao)Vcc的一半(ban)。其中(zhong)重(zhong)要(yao)(yao)的原因就需(xu)要(yao)(yao)一个高于(yu)Vcc的电(dian)(dian)压(ya)(ya)。所以(yi)采用自(zi)(zi)举电(dian)(dian)路来升压(ya)(ya)。

常(chang)用(yong)自(zi)举(ju)电路(lu)（摘自(zi)fairchild，使用(yong)说明书AN-6076《供高(gao)电压(ya)(ya)栅极驱(qu)动(dong)器IC 使用(yong)的(de)自(zi)举(ju)电路(lu)的(de)设计和使用(yong)准则》）the boost converter,或者叫step-up converter，是一种(zhong)开(kai)关直流(liu)升(sheng)压(ya)(ya)电路(lu)，它可以是输(shu)出(chu)电压(ya)(ya)比(bi)输(shu)入电压(ya)(ya)高(gao)。假定那(nei)个(ge)开(kai)关(guan)(三极管或者mos管)已经断开(kai)了很长时间，所有的元件都处于理想状态，电(dian)容(rong)电(dian)压等于输入电(dian)压。下面要分(fen)充电(dian)和(he)放电(dian)两个(ge)部分(fen)来(lai)说明(ming)这个(ge)电(dian)路(lu)。

MOS管自举电容工作原理

自(zi)举电(dian)容，内部高(gao)端(duan)MOS需要得(de)到(dao)高(gao)出IC的(de)VCC的(de)电(dian)压，通过(guo)自(zi)举电(dian)路(lu)升压得(de)到(dao)，比VCC高(gao)的(de)电(dian)压，否则，高(gao)端(duan)MOS无法驱动。

自(zi)(zi)举是指通(tong)(tong)过(guo)(guo)(guo)开关电(dian)(dian)(dian)源MOS管和(he)电(dian)(dian)(dian)容组(zu)成的(de)(de)(de)(de)(de)升(sheng)(sheng)(sheng)压(ya)(ya)电(dian)(dian)(dian)路,通(tong)(tong)过(guo)(guo)(guo)电(dian)(dian)(dian)源对电(dian)(dian)(dian)容充电(dian)(dian)(dian)致其电(dian)(dian)(dian)压(ya)(ya)高(gao)于(yu)VCC。最简单(dan)的(de)(de)(de)(de)(de)自(zi)(zi)举电(dian)(dian)(dian)路由一(yi)个电(dian)(dian)(dian)容构成，为了防止升(sheng)(sheng)(sheng)高(gao)后(hou)(hou)的(de)(de)(de)(de)(de)电(dian)(dian)(dian)压(ya)(ya)回灌到原(yuan)始的(de)(de)(de)(de)(de)输入电(dian)(dian)(dian)压(ya)(ya)，会加一(yi)个Diode.自(zi)(zi)举的(de)(de)(de)(de)(de)好处在于(yu)利用电(dian)(dian)(dian)容两(liang)端电(dian)(dian)(dian)压(ya)(ya)不能(neng)突变(bian)的(de)(de)(de)(de)(de)特性来(lai)升(sheng)(sheng)(sheng)高(gao)电(dian)(dian)(dian)压(ya)(ya)。举个例子(zi)来(lai)说，如(ru)果MOS的(de)(de)(de)(de)(de)Drink极(ji)(ji)电(dian)(dian)(dian)压(ya)(ya)为12V，Source极(ji)(ji)电(dian)(dian)(dian)压(ya)(ya)原(yuan)为0V，Gate极(ji)(ji)驱动(dong)电(dian)(dian)(dian)压(ya)(ya)也为12V，那么(me)(me)当MOS在导(dao)(dao)(dao)通(tong)(tong)瞬间，Soure极(ji)(ji)电(dian)(dian)(dian)压(ya)(ya)会升(sheng)(sheng)(sheng)高(gao)为Drink减压(ya)(ya)减去(qu)一(yi)个很(hen)小(xiao)的(de)(de)(de)(de)(de)导(dao)(dao)(dao)通(tong)(tong)压(ya)(ya)降，那么(me)(me)Vgs电(dian)(dian)(dian)压(ya)(ya)会接近于(yu)0V，MOS在导(dao)(dao)(dao)通(tong)(tong)瞬间后(hou)(hou)又会关断(duan)，再导(dao)(dao)(dao)通(tong)(tong)，再关断(duan)。如(ru)此下去(qu)，长时间在MOS的(de)(de)(de)(de)(de)Drink极(ji)(ji)与Source间通(tong)(tong)过(guo)(guo)(guo)的(de)(de)(de)(de)(de)是一(yi)个N倍于(yu)工作频率的(de)(de)(de)(de)(de)高(gao)频脉(mai)冲(chong)，这样的(de)(de)(de)(de)(de)脉(mai)冲(chong)尖峰(feng)在MOS上会产生(sheng)过(guo)(guo)(guo)大的(de)(de)(de)(de)(de)电(dian)(dian)(dian)压(ya)(ya)应力，很(hen)快(kuai)MOS管会被损坏。如(ru)果在MOS的(de)(de)(de)(de)(de)Gate与Source间接入一(yi)个小(xiao)电(dian)(dian)(dian)容，在MOS未导(dao)(dao)(dao)通(tong)(tong)时给电(dian)(dian)(dian)容充电(dian)(dian)(dian)，在MOS导(dao)(dao)(dao)通(tong)(tong)，Source电(dian)(dian)(dian)压(ya)(ya)升(sheng)(sheng)(sheng)高(gao)后(hou)(hou)，自(zi)(zi)动(dong)将Gate极(ji)(ji)电(dian)(dian)(dian)压(ya)(ya)升(sheng)(sheng)(sheng)高(gao)，便可使MOS保持继续导(dao)(dao)(dao)通(tong)(tong)。

mos管自举电路工作原理

升压自举电路原理

自举电(dian)路(lu)也(ye)叫(jiao)升(sheng)压(ya)(ya)(ya)电(dian)路(lu)，利用自举升(sheng)压(ya)(ya)(ya)二极管,自举升(sheng)压(ya)(ya)(ya)电(dian)容(rong)等电(dian)子元件(jian)，使电(dian)容(rong)放电(dian)电(dian)压(ya)(ya)(ya)和(he)电(dian)源(yuan)电(dian)压(ya)(ya)(ya)叠加，从而(er)使电(dian)压(ya)(ya)(ya)升(sheng)高．有的电(dian)路(lu)升(sheng)高的电(dian)压(ya)(ya)(ya)能达到数倍电(dian)源(yuan)电(dian)压(ya)(ya)(ya)。

升压电路原理

举(ju)个简单的例子：有一(yi)个12V的电(dian)(dian)(dian)(dian)路(lu)，电(dian)(dian)(dian)(dian)路(lu)中有一(yi)个场效应管需(xu)要15V的驱(qu)动电(dian)(dian)(dian)(dian)压(ya)，这个电(dian)(dian)(dian)(dian)压(ya)怎(zen)么弄(nong)出来？就(jiu)是用自举(ju)。通(tong)常用一(yi)个电(dian)(dian)(dian)(dian)容和一(yi)个二极(ji)管，电(dian)(dian)(dian)(dian)容存储电(dian)(dian)(dian)(dian)压(ya)，二极(ji)管防止电(dian)(dian)(dian)(dian)流(liu)倒灌，频率较高的时候，自举(ju)电(dian)(dian)(dian)(dian)路(lu)的电(dian)(dian)(dian)(dian)压(ya)就(jiu)是电(dian)(dian)(dian)(dian)路(lu)输入的电(dian)(dian)(dian)(dian)压(ya)加上电(dian)(dian)(dian)(dian)容上的电(dian)(dian)(dian)(dian)压(ya)，起到(dao)升压(ya)的作(zuo)用。

升压(ya)电(dian)路只是在(zai)实(shi)践中定(ding)的(de)名称，在(zai)理(li)论上没有这个概(gai)念。升压(ya)电(dian)路主要是在(zai)甲乙类(lei)单(dan)电(dian)源(yuan)互(hu)补对称电(dian)路中使用较为普(pu)遍。甲乙类(lei)单(dan)电(dian)源(yuan)互(hu)补对称电(dian)路在(zai)理(li)论上可(ke)以使输出(chu)电(dian)压(ya)Vo达(da)到Vcc的(de)一半(ban)，但在(zai)实(shi)际的(de)测试中，输出(chu)电(dian)压(ya)远(yuan)达(da)不到Vcc的(de)一半(ban)。其中重要的(de)原因就(jiu)需(xu)要一个高于Vcc的(de)电(dian)压(ya)。所以采用升压(ya)电(dian)路来(lai)升压(ya)。

开关直(zhi)流(liu)(liu)升压(ya)电路(lu)(即所谓的boost或者(zhe)step-up电路(lu))原理the boost converter,或者(zhe)叫step-up converter，是(shi)一种开关直(zhi)流(liu)(liu)升压(ya)电路(lu)，它可以是(shi)输出(chu)电压(ya)比输入电压(ya)高(gao)。基本电路(lu)图(tu)见图(tu)1.

假定那个开关(三极管(guan)(guan)或者(zhe)mos管(guan)(guan))已经断开了很长时(shi)间，所有的元件都处于(yu)(yu)理想(xiang)状态，电(dian)容(rong)电(dian)压(ya)等于(yu)(yu)输入电(dian)压(ya)。下面要分(fen)充(chong)电(dian)和(he)放电(dian)两个部分(fen)来说明这(zhei)个电(dian)路。

充电过程

在充(chong)电(dian)(dian)过程(cheng)中，开关(guan)闭(bi)合(三极(ji)管(guan)导通)，等(deng)效电(dian)(dian)路如图(tu)二(er)(er)，开关(guan)(三极(ji)管(guan))处(chu)用(yong)导线代替。这时(shi)，输入(ru)电(dian)(dian)压流过电(dian)(dian)感。二(er)(er)极(ji)管(guan)防止电(dian)(dian)容对地放电(dian)(dian)。由于(yu)输入(ru)是直流电(dian)(dian)，所以电(dian)(dian)感上的(de)电(dian)(dian)流以一定的(de)比(bi)率(lv)线性增加(jia)，这个比(bi)率(lv)跟电(dian)(dian)感大小有关(guan)。随着(zhe)电(dian)(dian)感电(dian)(dian)流增加(jia)，电(dian)(dian)感里储存了(le)一些能量(liang)。

放电过程

如(ru)图，这是当(dang)(dang)开(kai)(kai)关(guan)断(duan)开(kai)(kai)(三极(ji)管截止(zhi))时(shi)的(de)(de)等效电(dian)(dian)(dian)(dian)(dian)(dian)路。当(dang)(dang)开(kai)(kai)关(guan)断(duan)开(kai)(kai)(三极(ji)管截止(zhi))时(shi)，由(you)于(yu)电(dian)(dian)(dian)(dian)(dian)(dian)感(gan)的(de)(de)电(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu) 保(bao)持(chi)特性，流(liu)(liu)经电(dian)(dian)(dian)(dian)(dian)(dian)感(gan)的(de)(de)电(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)不会马上变为(wei)0，而(er)是缓慢(man)的(de)(de)由(you)充电(dian)(dian)(dian)(dian)(dian)(dian)完毕(bi)(bi)时(shi)的(de)(de)值变为(wei)0。而(er)原来的(de)(de)电(dian)(dian)(dian)(dian)(dian)(dian)路已断(duan)开(kai)(kai)，于(yu)是电(dian)(dian)(dian)(dian)(dian)(dian)感(gan)只能通过(guo)新电(dian)(dian)(dian)(dian)(dian)(dian)路放电(dian)(dian)(dian)(dian)(dian)(dian)，即电(dian)(dian)(dian)(dian)(dian)(dian)感(gan)开(kai)(kai)始给电(dian)(dian)(dian)(dian)(dian)(dian)容(rong)充电(dian)(dian)(dian)(dian)(dian)(dian)， 电(dian)(dian)(dian)(dian)(dian)(dian)容(rong)两端电(dian)(dian)(dian)(dian)(dian)(dian)压升高(gao)，此时(shi)电(dian)(dian)(dian)(dian)(dian)(dian)压已经高(gao)于(yu)输入(ru)电(dian)(dian)(dian)(dian)(dian)(dian)压了(le)。升压完毕(bi)(bi)。

说起来升压(ya)过(guo)程(cheng)(cheng)就是一(yi)(yi)个(ge)电(dian)感(gan)(gan)的能量传(chuan)递过(guo)程(cheng)(cheng)。充电(dian)时，电(dian)感(gan)(gan)吸收能量，放电(dian)时电(dian)感(gan)(gan)放出(chu)(chu)能量。如果(guo)电(dian)容(rong)量足(zu)够(gou)大，那(nei)么在(zai)输(shu)出(chu)(chu)端就可以(yi)在(zai)放电(dian)过(guo)程(cheng)(cheng)中保持(chi)一(yi)(yi)个(ge)持(chi)续的电(dian)流。如果(guo)这个(ge)通断(duan)的过(guo)程(cheng)(cheng)不断(duan)重复，就可以(yi)在(zai)电(dian)容(rong)两端得到高于输(shu)入电(dian)压(ya)的电(dian)压(ya)。

常用升压电路(lu)

P 沟道高端栅极驱动器

直接式驱(qu)动器：适用(yong)于(yu)最大输入电压(ya)小(xiao)于(yu)器件的栅(zha)- 源极击穿电压(ya)。

开(kai)放式收集(ji)器：方法(fa)简(jian)单，但是不适用(yong)于直接驱动高速电路中(zhong)的MOSFET。

电(dian)平转换驱动器：适用于高速应用，能够与常见PWM 控制器无缝式(shi)工作(zuo)。

N 沟道高端栅极驱动器

直(zhi)接(jie)式驱(qu)动器：MOSFET最(zui)简单的高端应用，由PWM 控制器或以地为基准的驱(qu)动器直(zhi)接(jie)驱(qu)动，但它必须满足下面两(liang)个条件：

1、VCC

2、Vdc

浮(fu)动电(dian)源(yuan)栅极(ji)驱动器(qi):独(du)立电(dian)源(yuan)的成本影(ying)响是(shi)很显(xian)著的。光(guang)耦合(he)器(qi)相对昂贵(gui)，而且带宽有限，对噪声敏感。

变压器(qi)耦合式驱动器(qi):在不确定的(de)周期(qi)内充分(fen)控(kong)制(zhi)栅极(ji)，但在某种程度上，限(xian)制(zhi)了开关(guan)性能(neng)。但是(shi)，这是(shi)可(ke)以改(gai)善(shan)的(de)，只是(shi)电路更复杂了。

电(dian)荷泵驱动器(qi):对于(yu)(yu)开关应用(yong)，导通时(shi)间(jian)往往很长。由于(yu)(yu)电(dian)压倍增电(dian)路的(de)效率低，可能需要(yao)更多低电(dian)压级泵。

自举式驱动器:简单，廉价，也(ye)有(you)局限；例如，占空比和导(dao)通时间都受到(dao)刷(shua)新(xin)自举电容的限制。

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