利盈娱乐(中国)创新平台有限公司

三端稳(wen)压(ya)(ya)管(guan)是一(yi)种直到临界反向击穿电(dian)压(ya)(ya)前都具有很高(gao)电(dian)阻的半导体(ti)器(qi)件。稳(wen)压(ya)(ya)管(guan)在反向击穿时，在一(yi)定(ding)的电(dian)流范围内（或(huo)者说在一(yi)定(ding)功(gong)率损耗范围内），端电(dian)压(ya)(ya)几乎(hu)不变，表现出(chu)稳(wen)压(ya)(ya)特性，因而广泛应(ying)用于(yu)稳(wen)压(ya)(ya)电(dian)源(yuan)与限幅电(dian)路之中。

主要有两种，一种输出电压是固定的，另一种输出电压是可调的，称为可调输出三端稳压管产品，其基本原理相同，均采用串联型稳压电路。因为固定它属于串联型稳压电路，因此它的原理等同于串联型稳压电路。
其中R1、Rp、R2组成的分压器是取样电路，从输出端取出部分电压UB2作为取样电压加至三极管T2的基极。稳压管Dz以其稳定电压Uz作为基准电压，加在T2的发射极上。R3是稳压管的限流电阻。三极管T2组成比较放大电路，它将取样电压UB2与基准电压Uz加以比较和放大，再去控制三极管T1的基极电位。输入电压Ui加在三极管T1与负载RL相串联的电路上，因此，改变T1集电极间的电压降UCE1便可调节RL两端的电压Uo。也就是说，稳压电路的输出电压Uo可以通过三极管T1加以调节，所以T1称为调整管。由于调整元件是晶体管管，而且在电路中与负载相串联，故称为晶体管串联型稳压电路。电阻R4和T1的基极偏置电阻，也是T2的集电极负载电阻。

当电(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)压(ya)(ya)降(jiang)(jiang)(jiang)低(di)或负(fu)(fu)载电(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻减(jian)小(xiao)(xiao)而使输出(chu)端电(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)压(ya)(ya)有所下降(jiang)(jiang)(jiang)时，其(qi)取样电(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)压(ya)(ya)UB2相应减(jian)小(xiao)(xiao)，T2基(ji)极(ji)(ji)(ji)(ji)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)位(wei)下降(jiang)(jiang)(jiang)。但因T2发(fa)射(she)极(ji)(ji)(ji)(ji)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)位(wei)既稳(wen)压(ya)(ya)管(guan)的(de)稳(wen)定Uz保(bao)持(chi)不变(bian)，所以(yi)发(fa)射(she)极(ji)(ji)(ji)(ji)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)压(ya)(ya)UBE2减(jian)小(xiao)(xiao)，导(dao)(dao)致T2集(ji)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)极(ji)(ji)(ji)(ji)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流减(jian)小(xiao)(xiao)而集(ji)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)极(ji)(ji)(ji)(ji)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)位(wei)Uc2升高(gao)。由于放大管(guan)T2的(de)集(ji)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)极(ji)(ji)(ji)(ji)与(yu)调(diao)整(zheng)管(guan)T1的(de)基(ji)极(ji)(ji)(ji)(ji)接在一起，故T1基(ji)极(ji)(ji)(ji)(ji)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)位(wei)升高(gao)，导(dao)(dao)致集(ji)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)极(ji)(ji)(ji)(ji)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流增(zeng)大而管(guan)压(ya)(ya)降(jiang)(jiang)(jiang)UCE1减(jian)小(xiao)(xiao)。因为T1与(yu)RL串联，所以(yi)，输出(chu)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)压(ya)(ya)Uo基(ji)本(ben)不变(bian)。同理,当电(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)压(ya)(ya)或负(fu)(fu)载发(fa)生变(bian)化引起输出(chu)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)压(ya)(ya)Uo增(zeng)大时，通过取样、比较放大、调(diao)整(zheng)等过程，将使调(diao)整(zheng)调(diao)整(zheng)管(guan)的(de)管(guan)压(ya)(ya)降(jiang)(jiang)(jiang)UCE1增(zeng)加，结(jie)果(guo)抑(yi)制(zhi)了(le)输出(chu)端电(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)压(ya)(ya)的(de)增(zeng)大，输出(chu)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)压(ya)(ya)仍(reng)基(ji)本(ben)保(bao)持(chi)不变(bian)。调(diao)节电(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)位(wei)器Rp，可对输出(chu)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)压(ya)(ya)进(jin)行微调(diao)。调(diao)整(zheng)管(guan)T1与(yu)负(fu)(fu)载电(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻RL组成的(de)是射(she)极(ji)(ji)(ji)(ji)输出(chu)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路，所以(yi)具有稳(wen)定输出(chu)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)压(ya)(ya)的(de)特(te)点。

在串联型稳压电源电路的工作过程中，要求调整管始终处在放大状态。通过调整管的电流等于负载电流，因此必须选用适当的大功率管作调整管，并按规定安装散热装置。为了防止短路或长期过载烧坏调整管，在直流稳压器中一般还设有短路保护和过载保护等电路。
在(zai)使(shi)用(yong)时(shi)必须(xu)注意：(VI)和(he)(Vo)之(zhi)间(jian)的(de)关系，以(yi)7805为例，该(gai)固(gu)定输(shu)出电压(ya)(ya)是5V，而输(shu)入(ru)(ru)(ru)电压(ya)(ya)至少大(da)于(yu)7V，这样输(shu)入(ru)(ru)(ru)/输(shu)出之(zhi)间(jian)有(you)2－3V及以(yi)上的(de)压(ya)(ya)差。使(shi)调整(zheng)管(guan)保证工作在(zai)放(fang)大(da)区。但压(ya)(ya)差取得大(da)时(shi)，又会(hui)增加集(ji)成块的(de)功耗(hao)，所以(yi)，两者应兼顾(gu)，即既保证在(zai)最大(da)负载电流时(shi)调整(zheng)管(guan)不进(jin)入(ru)(ru)(ru)饱和(he)，又不致于(yu)功耗(hao)偏大(da)。另外一般在(zai)三端稳压(ya)(ya)管(guan)的(de)输(shu)入(ru)(ru)(ru)输(shu)出端接一个(ge)二极管(guan)，用(yong)来防止(zhi)输(shu)入(ru)(ru)(ru)端短路时(shi),输(shu)出端存储的(de)电荷(he)通过稳压(ya)(ya)器(qi),而损坏器(qi)件(jian)。

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