直流(liu)稳压(ya)电源(yuan)根(gen)据调整管(guan)的工作状态分成(cheng)两类：线性直流(liu)电源(yuan)和开关(guan)直流(liu)电源(yuan)。

　　线性直流电(dian)(dian)源(yuan)，是(shi)指调整(zheng)管(guan)工作在(zai)线性状(zhuang)态下(xia)的(de)稳压电(dian)(dian)源(yuan)。而在(zai)开关(guan)电(dian)(dian)源(yuan)中则不一样，开关(guan)管(guan)(在(zai)开关(guan)电(dian)(dian)源(yuan)中，我们一般(ban)把(ba)调整(zheng)管(guan)叫做开关(guan)管(guan))是(shi)工作在(zai)开、关(guan)两种状(zhuang)态下(xia)的(de)：开——电(dian)(dian)阻很小(xiao);关(guan)——电(dian)(dian)阻很大。

　　开(kai)(kai)关(guan)(guan)(guan)(guan)(guan)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)源是一种比较(jiao)新(xin)型(xing)的(de)(de)(de)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)源。它具有效率(lv)高，重量轻，可(ke)升(sheng)、降压(ya)，输(shu)(shu)出功(gong)率(lv)大(da)(da)等优点。但是由(you)(you)于电(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)工(gong)作在(zai)开(kai)(kai)关(guan)(guan)(guan)(guan)(guan)状(zhuang)态(tai)，所以噪(zao)声比较(jiao)大(da)(da)。 通(tong)过(guo)(guo)下图，我们(men)来(lai)简(jian)单的(de)(de)(de)说说降压(ya)型(xing)开(kai)(kai)关(guan)(guan)(guan)(guan)(guan)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)源的(de)(de)(de)工(gong)作原理。如(ru)图所示，电(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)由(you)(you)开(kai)(kai)关(guan)(guan)(guan)(guan)(guan)K(实(shi)际电(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)中为三极管(guan)或(huo)者场(chang)效应管(guan))，续流(liu)(liu)二(er)极管(guan)D，储能(neng)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)感(gan)(gan)(gan)L，滤波电(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)C等构成。当开(kai)(kai)关(guan)(guan)(guan)(guan)(guan)闭(bi)合(he)时，电(dian)(dian)(dian)(dian)(dian)(dian)(dian)源通(tong)过(guo)(guo)开(kai)(kai)关(guan)(guan)(guan)(guan)(guan)K、电(dian)(dian)(dian)(dian)(dian)(dian)(dian)感(gan)(gan)(gan)L给负载供(gong)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)，并将部分电(dian)(dian)(dian)(dian)(dian)(dian)(dian)能(neng)储存在(zai)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)感(gan)(gan)(gan)L以及电(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)C中。由(you)(you)于电(dian)(dian)(dian)(dian)(dian)(dian)(dian)感(gan)(gan)(gan)L的(de)(de)(de)自(zi)感(gan)(gan)(gan)，在(zai)开(kai)(kai)关(guan)(guan)(guan)(guan)(guan)接通(tong)后，电(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)增大(da)(da)得比较(jiao)缓(huan)慢，即输(shu)(shu)出不能(neng)立刻达(da)到电(dian)(dian)(dian)(dian)(dian)(dian)(dian)源电(dian)(dian)(dian)(dian)(dian)(dian)(dian)压(ya)值。一定时间(jian)后，开(kai)(kai)关(guan)(guan)(guan)(guan)(guan)断开(kai)(kai)，由(you)(you)于电(dian)(dian)(dian)(dian)(dian)(dian)(dian)感(gan)(gan)(gan)L的(de)(de)(de)自(zi)感(gan)(gan)(gan)作用(yong)(可(ke)以比较(jiao)形象的(de)(de)(de)认为电(dian)(dian)(dian)(dian)(dian)(dian)(dian)感(gan)(gan)(gan)中的(de)(de)(de)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)有惯性(xing)作用(yong))，将保持(chi)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)中的(de)(de)(de)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)不变，即从左往右(you)继续流(liu)(liu)。这(zhei)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)流(liu)(liu)过(guo)(guo)负载，从地线返(fan)回(hui)，流(liu)(liu)到续流(liu)(liu)二(er)极管(guan)D的(de)(de)(de)正极，经过(guo)(guo)二(er)极管(guan)D，返(fan)回(hui)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)感(gan)(gan)(gan)L的(de)(de)(de)左端，从而形成了一个(ge)回(hui)路(lu)(lu)。通(tong)过(guo)(guo)控制(zhi)(zhi)开(kai)(kai)关(guan)(guan)(guan)(guan)(guan)闭(bi)合(he)跟断开(kai)(kai)的(de)(de)(de)时间(jian)(即PWM——脉(mai)冲宽(kuan)度调制(zhi)(zhi))，就可(ke)以控制(zhi)(zhi)输(shu)(shu)出电(dian)(dian)(dian)(dian)(dian)(dian)(dian)压(ya)。如(ru)果通(tong)过(guo)(guo)检测输(shu)(shu)出电(dian)(dian)(dian)(dian)(dian)(dian)(dian)压(ya)来(lai)控制(zhi)(zhi)开(kai)(kai)、关(guan)(guan)(guan)(guan)(guan)的(de)(de)(de)时间(jian)，以保持(chi)输(shu)(shu)出电(dian)(dian)(dian)(dian)(dian)(dian)(dian)压(ya)不变，这(zhei)就实(shi)现了稳压(ya)的(de)(de)(de)目的(de)(de)(de)。

　　在(zai)(zai)开(kai)关(guan)闭(bi)合(he)期间(jian)，电感(gan)(gan)(gan)(gan)存储能量(liang);在(zai)(zai)开(kai)关(guan)断开(kai)期间(jian)，电感(gan)(gan)(gan)(gan)释(shi)放能量(liang)，所(suo)以电感(gan)(gan)(gan)(gan)L叫(jiao)做(zuo)储能电感(gan)(gan)(gan)(gan)。二极管(guan)D在(zai)(zai)开(kai)关(guan)断开(kai)期间(jian)，负责给电感(gan)(gan)(gan)(gan)L提供电流通路，所(suo)以二极管(guan)D叫(jiao)做(zuo)续流二极管(guan)。

　　在实际(ji)的(de)开关电源(yuan)中，开关K由三极管或场效应管代替(ti)。当开关断开时，电流(liu)很(hen)小;当开关闭(bi)合时，电压(ya)很(hen)小，所以发热功率U×I就会很(hen)小。这就是(shi)开关电源(yuan)效率高的(de)原(yuan)因。