升压电路原理分析-DC/DC升压电路原理及工作方式详解

升压电路简介

升(sheng)压(ya)(ya)电(dian)(dian)(dian)(dian)路原理是本文的重点，我们先来了解(jie)什么是升(sheng)压(ya)(ya)电(dian)(dian)(dian)(dian)路。升(sheng)压(ya)(ya)电(dian)(dian)(dian)(dian)路也叫自(zi)举电(dian)(dian)(dian)(dian)路，是利用自(zi)举升(sheng)压(ya)(ya)二极管(guan)，自(zi)举升(sheng)压(ya)(ya)电(dian)(dian)(dian)(dian)容(rong)等电(dian)(dian)(dian)(dian)子元件，使电(dian)(dian)(dian)(dian)容(rong)放电(dian)(dian)(dian)(dian)电(dian)(dian)(dian)(dian)压(ya)(ya)和电(dian)(dian)(dian)(dian)源电(dian)(dian)(dian)(dian)压(ya)(ya)叠加，从而(er)使电(dian)(dian)(dian)(dian)压(ya)(ya)升(sheng)高(gao)，有的电(dian)(dian)(dian)(dian)路升(sheng)高(gao)的电(dian)(dian)(dian)(dian)压(ya)(ya)能达到数倍电(dian)(dian)(dian)(dian)源电(dian)(dian)(dian)(dian)压(ya)(ya)。

升压电路原理

升(sheng)压(ya)电(dian)(dian)(dian)路(lu)(lu)(lu)(lu)原理如(ru)下(xia)：举(ju)个(ge)简单的(de)例(li)子：有一(yi)个(ge)12V的(de)电(dian)(dian)(dian)路(lu)(lu)(lu)(lu)，电(dian)(dian)(dian)路(lu)(lu)(lu)(lu)中有一(yi)个(ge)场效应(ying)管(guan)需要15V的(de)驱动电(dian)(dian)(dian)压(ya)，这个(ge)电(dian)(dian)(dian)压(ya)怎(zen)么(me)弄(nong)出来？就是用(yong)(yong)自举(ju)。通常(chang)用(yong)(yong)一(yi)个(ge)电(dian)(dian)(dian)容和一(yi)个(ge)二(er)极(ji)管(guan)，电(dian)(dian)(dian)容存储电(dian)(dian)(dian)荷，二(er)极(ji)管(guan)防止电(dian)(dian)(dian)流倒灌，频率较(jiao)高的(de)时候，自举(ju)电(dian)(dian)(dian)路(lu)(lu)(lu)(lu)的(de)电(dian)(dian)(dian)压(ya)就是电(dian)(dian)(dian)路(lu)(lu)(lu)(lu)输入(ru)的(de)电(dian)(dian)(dian)压(ya)加上电(dian)(dian)(dian)容上的(de)电(dian)(dian)(dian)压(ya)，起到升(sheng)压(ya)的(de)作(zuo)用(yong)(yong)。

自(zi)举(ju)电(dian)(dian)(dian)路(lu)只(zhi)是在(zai)(zai)(zai)实践(jian)中(zhong)定的(de)名称(cheng)(cheng)，在(zai)(zai)(zai)理论上没有这个概念。自(zi)举(ju)电(dian)(dian)(dian)路(lu)主(zhu)要(yao)是在(zai)(zai)(zai)甲(jia)乙类单(dan)(dan)电(dian)(dian)(dian)源互补对(dui)(dui)称(cheng)(cheng)电(dian)(dian)(dian)路(lu)中(zhong)使(shi)用较为普遍。甲(jia)乙类单(dan)(dan)电(dian)(dian)(dian)源互补对(dui)(dui)称(cheng)(cheng)电(dian)(dian)(dian)路(lu)在(zai)(zai)(zai)理论上可以使(shi)输出电(dian)(dian)(dian)压(ya)Vo达到Vcc的(de)一半，但在(zai)(zai)(zai)实际的(de)测试中(zhong)，输出电(dian)(dian)(dian)压(ya)远达不到Vcc的(de)一半。其中(zhong)重(zhong)要(yao)的(de)原因就需(xu)要(yao)一个高于Vcc的(de)电(dian)(dian)(dian)压(ya)。所以采用自(zi)举(ju)电(dian)(dian)(dian)路(lu)来升压(ya)。

常用自举电(dian)路(lu)（摘自fairchild，使用说明书(shu)AN-6076《供高电(dian)压(ya)栅(zha)极驱动器IC 使用的(de)自举电(dian)路(lu)的(de)设计和使用准则(ze)》），开关直流升压(ya)电(dian)路（即所谓(wei)的boost或者(zhe)step-up电(dian)路）原理，the boost converter，或者叫step-up converter，是(shi)一种(zhong)开关(guan)直流升压(ya)电路(lu)，它可以(yi)是(shi)输出电压(ya)比输入电压(ya)高(gao)。基本(ben)电路(lu)图见(jian)图1.

升压电路原理

假定(ding)那个(ge)开关（三极管或者mos管）已经(jing)断开了很长时间，所有的元(yuan)件(jian)都处于理想状态，电(dian)(dian)(dian)容电(dian)(dian)(dian)压等于输入(ru)电(dian)(dian)(dian)压。下面要分充(chong)电(dian)(dian)(dian)和放(fang)电(dian)(dian)(dian)两个(ge)部分来说明这个(ge)电(dian)(dian)(dian)路。

（1）充电过程

升压电(dian)(dian)(dian)(dian)路原理的(de)充电(dian)(dian)(dian)(dian)过程(cheng)，在充电(dian)(dian)(dian)(dian)过程(cheng)中，开(kai)关闭合(三极管(guan)导(dao)通)，等效(xiao)电(dian)(dian)(dian)(dian)路如图(tu)二(er)，开(kai)关(三极管(guan))处用导(dao)线代替。这时，输(shu)入(ru)电(dian)(dian)(dian)(dian)压流过电(dian)(dian)(dian)(dian)感(gan)。二(er)极管(guan)防止电(dian)(dian)(dian)(dian)容对地放电(dian)(dian)(dian)(dian)。由于输(shu)入(ru)是直(zhi)流电(dian)(dian)(dian)(dian)，所以电(dian)(dian)(dian)(dian)感(gan)上(shang)的(de)电(dian)(dian)(dian)(dian)流以一定(ding)的(de)比率线性增加，这个比率跟电(dian)(dian)(dian)(dian)感(gan)大小有关。随着电(dian)(dian)(dian)(dian)感(gan)电(dian)(dian)(dian)(dian)流增加，电(dian)(dian)(dian)(dian)感(gan)里储存(cun)了一些能量。

升压电路原理

（2）放电过程

升(sheng)压(ya)(ya)电(dian)(dian)(dian)路原理的(de)放电(dian)(dian)(dian)过(guo)程(cheng)。如(ru)图，这(zhei)是(shi)当(dang)开(kai)(kai)(kai)关(guan)断开(kai)(kai)(kai)(三(san)(san)极管(guan)截(jie)止)时的(de)等效(xiao)电(dian)(dian)(dian)路。当(dang)开(kai)(kai)(kai)关(guan)断开(kai)(kai)(kai)(三(san)(san)极管(guan)截(jie)止)时，由(you)于(yu)(yu)电(dian)(dian)(dian)感的(de)电(dian)(dian)(dian)流保(bao)持(chi)特性，流经电(dian)(dian)(dian)感的(de)电(dian)(dian)(dian)流不(bu)会马上变为0，而(er)是(shi)缓(huan)慢(man)的(de)由(you)充(chong)(chong)电(dian)(dian)(dian)完(wan)(wan)毕时的(de)值变为0。而(er)原来的(de)电(dian)(dian)(dian)路已断开(kai)(kai)(kai)，于(yu)(yu)是(shi)电(dian)(dian)(dian)感只(zhi)能通过(guo)新电(dian)(dian)(dian)路放电(dian)(dian)(dian)，即电(dian)(dian)(dian)感开(kai)(kai)(kai)始给电(dian)(dian)(dian)容充(chong)(chong)电(dian)(dian)(dian)，电(dian)(dian)(dian)容两端电(dian)(dian)(dian)压(ya)(ya)升(sheng)高，此时电(dian)(dian)(dian)压(ya)(ya)已经高于(yu)(yu)输入电(dian)(dian)(dian)压(ya)(ya)了，升(sheng)压(ya)(ya)完(wan)(wan)毕。

升压电路原理

升压(ya)过(guo)程(cheng)就是(shi)一个电(dian)(dian)(dian)感的能(neng)(neng)(neng)量(liang)(liang)传递(di)过(guo)程(cheng)。充(chong)电(dian)(dian)(dian)时，电(dian)(dian)(dian)感吸(xi)收(shou)能(neng)(neng)(neng)量(liang)(liang)，放电(dian)(dian)(dian)时电(dian)(dian)(dian)感放出能(neng)(neng)(neng)量(liang)(liang)。如(ru)果电(dian)(dian)(dian)感量(liang)(liang)足够(gou)大(da)，那(nei)么在(zai)(zai)(zai)输出端就可以(yi)在(zai)(zai)(zai)放电(dian)(dian)(dian)过(guo)程(cheng)中保(bao)持(chi)一个持(chi)续的电(dian)(dian)(dian)流。如(ru)果这个通断的过(guo)程(cheng)不断重复(fu)，就可以(yi)在(zai)(zai)(zai)电(dian)(dian)(dian)容两端得到高于输入电(dian)(dian)(dian)压(ya)的电(dian)(dian)(dian)压(ya)。

升压电路原理

常用升压电路

1、P沟道高(gao)端栅极(ji)驱(qu)动器(qi)

直接式驱动器(qi)：适(shi)用(yong)于(yu)(yu)最大(da)输入电(dian)压小于(yu)(yu)器(qi)件的(de)栅- 源极击穿电(dian)压。

开放式(shi)收(shou)集器：方法简单(dan)，但是不适用于直(zhi)接驱动高(gao)速电(dian)路中(zhong)的MOSFET。

电平转换驱(qu)动器(qi)：适用于高速应用，能够与常见PWM 控制(zhi)器(qi)无(wu)缝式工(gong)作。

2、N沟(gou)道(dao)高端栅极(ji)驱动器

直(zhi)接式驱(qu)动(dong)器(qi)：MOSFET最简单的(de)高端应(ying)用，由PWM 控制(zhi)器(qi)或以地为基(ji)准的(de)驱(qu)动(dong)器(qi)直(zhi)接驱(qu)动(dong)，但(dan)它必须满足下面两个条件：

1、VCC<Vgs,max

2、Vdc<VCC-Vgs,miller

浮动(dong)电(dian)源栅极(ji)驱动(dong)器(qi):独立电(dian)源的(de)成本影响是很显著的(de)。光(guang)耦合器(qi)相(xiang)对(dui)昂贵，而(er)且带宽有限(xian)，对(dui)噪(zao)声(sheng)敏感。

变(bian)压器耦合式驱(qu)动器:在不确定(ding)的(de)周期内充分控(kong)制(zhi)栅极(ji)，但(dan)在某种程度上，限制(zhi)了(le)开关性能。但(dan)是(shi)，这是(shi)可以(yi)改善的(de)，只是(shi)电(dian)路(lu)更(geng)复杂了(le)。

电(dian)(dian)荷泵驱动器:对于开关应(ying)用，导通时间往往很长。由(you)于电(dian)(dian)压(ya)倍(bei)增电(dian)(dian)路的效率低，可能需要更多(duo)低电(dian)(dian)压(ya)级泵。

自举式驱动器:简单，廉价，也(ye)有局限；例如，占空比和导通(tong)时间都受到刷新自举电容的限制。

DC/DC 升压电路原理

升压式DC/DC变(bian)换(huan)器主要用(yong)于输出(chu)电(dian)流较小的场合(he)，只要采用(yong)1~2节电(dian)池便(bian)可获(huo)得3~12V工(gong)作(zuo)电(dian)压，工(gong)作(zuo)电(dian)流可达几十毫(hao)安(an)(an)至几百毫(hao)安(an)(an)，其转换(huan)效率可达70%-80%。

升(sheng)压(ya)(ya)式DC/DC变换器(qi)的(de)基本工作原理如(ru)图(tu)所示(shi)。电(dian)(dian)路中的(de)VT为开关管(guan)，当脉冲振荡器(qi)对双(shuang)稳态(tai)电(dian)(dian)路置位(wei)(即Q端(duan)为1)时(shi)，VT导通，电(dian)(dian)感(gan)VT中流(liu)过电(dian)(dian)流(liu)并储(chu) 存能(neng)量，直(zhi)到电(dian)(dian)感(gan)电(dian)(dian)流(liu)在RS上的(de)压(ya)(ya)降等于(yu)比较器(qi)设定的(de)闽值电(dian)(dian)压(ya)(ya)时(shi)，双(shuang)稳态(tai)电(dian)(dian)路复位(wei)，即Q端(duan)为0。

此时(shi)VT截(jie)止，电(dian)感LT中储存的能量通(tong)过一极(ji)管VD1供给负载(zai)，同时(shi)对(dui)C进行充电(dian)。当负载(zai)电(dian)压(ya)(ya)(ya)要跌落时(shi)，电(dian)容C放(fang)电(dian)，这时(shi)输出端可获(huo)得高于输大端的稳定电(dian)压(ya)(ya)(ya)。输出的电(dian)压(ya)(ya)(ya)由分压(ya)(ya)(ya)器R1和R2分压(ya)(ya)(ya)后输入误差放(fang)大器，并与基准(zhun)电(dian)压(ya)(ya)(ya)一起去控制脉冲(chong)宽度，由(you)此(ci)而获得所需要的电(dian)压，即V0=VR*(R1/R2+1)式中:VR——基准电(dian)压。

降压式(shi)DC/DC变(bian)换(huan)器的输出电(dian)流较大(da)，多(duo)为数百毫安至(zhi)几安，因此(ci)适(shi)用于输出电(dian)流较大(da)的场合(he)。降压式(shi)DC/DC变(bian)换(huan)器基(ji)本工作原理电(dian)路如(ru)图所示。VT1为开(kai)关管，当(dang)VT1导通(tong)时，输入电(dian)压Vi通(tong)过电(dian)感L1向负载RL供(gong)电(dian)，与此(ci)同时也向电(dian)容C2充电(dian)。

在这个过程中，电(dian)(dian)容C2及电(dian)(dian)感L1中储存能量。当VT1截止(zhi)时，由储存在电(dian)(dian)感L1中的(de)能量继续向RL供电(dian)(dian)，当输(shu)出电(dian)(dian)压(ya)(ya)要下降(jiang)时，电(dian)(dian)容C2中的(de)能量也向RL放电(dian)(dian)，维持输(shu)出电(dian)(dian)压(ya)(ya)不(bu)变。二(er)(er)极(ji)管VD1为(wei)续流二(er)(er)极(ji)管，以便构成电(dian)(dian)路回路。输(shu)出的(de)电(dian)(dian)压(ya)(ya)Vo经R1和R2组(zu)成的(de)分(fen)压(ya)(ya)器分(fen)压(ya)(ya)，把(ba)输(shu)出电(dian)(dian)压(ya)(ya)的(de)信号(hao)反馈至(zhi)控(kong)制电(dian)(dian)路，由控(kong)制电(dian)(dian)路来控(kong)制开关管的(de)导通及截止(zhi)时间，使输(shu)出电(dian)(dian)压(ya)(ya)保持不(bu)变。

升压电路原理