VMOS的选择原则

(1)电压规格(V_DSS)：俗称耐压，至少应该为主绕组的3倍，需求留意的是，主绕组的电压指的是图2.6中的N2或者N3，而不是二者相加。详细而言，图中为10.5V，因而Q1、Q2的电压规格至少为31.5V，思索到10%的动摇和1.5倍的保险系数，则电压规格不应该低于31.5 X 1.1X 1.5＝52V。图中的2SK2313的电压规格为60v，契合请求。
其次，依据普通经历，电压规格超越200V的VMOS，饱和导通电阻的优势就不明显了，而本钱却比二极管高得多，电路也复杂。因而，用作同步整流时，主绕组的最高电压不应该高于40V。

(2)电流规格(In)：这个问题主要与最大耗散功率有关，由于计算办法复杂并且需求实验停止验证，因而也能够直接用理论办法进行肯定，即在实践的工作环境中，依照最极端的最高环境温度，比方夏天比拟热的温度，如35℃，依据实践所需求的工作电流，接上适宜的假负载，连续工作2小时左右，假如MOS管散热片(TAB)不烫手，就根本上能够运用。这个办法固然粗略，但是很简单适用。

(3)mos饱和导通电阻(RDS（ON）)：当然越小越好，典型值最好小于10mQ，这个数值以从技术手册上查到。

(4)开启电压(YGS（_th））也(ye)称为(wei)(wei)(wei)“栅极阈值电(dian)(dian)(dian)压(ya)(ya)(ya)(ya)”，这(zhei)个(ge)(ge)数值的(de)(de)(de)(de)选择在这(zhei)里主要(yao)与用作(zuo)比拟(ni)器的(de)(de)(de)(de)运放(fang)(fang)有火。VMOS不像BJT，栅极相关(guan)于(yu)源极需求有一定的(de)(de)(de)(de)电(dian)(dian)(dian)压(ya)(ya)(ya)(ya)才(cai)干开(kai)通(tong)(tong)，这(zhei)个(ge)(ge)电(dian)(dian)(dian)压(ya)(ya)(ya)(ya)的(de)(de)(de)(de)最(zui)低(di)值（通(tong)(tong)常是一个(ge)(ge)范围）称为(wei)(wei)(wei)开(kai)启(qi)(qi)(qi)(qi)电(dian)(dian)(dian)压(ya)(ya)(ya)(ya)，饱和导(dao)通(tong)(tong)电(dian)(dian)(dian)压(ya)(ya)(ya)(ya)普(pu)通(tong)(tong)为(wei)(wei)(wei)开(kai)启(qi)(qi)(qi)(qi)电(dian)(dian)(dian)压(ya)(ya)(ya)(ya)的(de)(de)(de)(de)一倍左(zuo)右(you)，假如技术手册给出的(de)(de)(de)(de)开(kai)启(qi)(qi)(qi)(qi)电(dian)(dian)(dian)压(ya)(ya)(ya)(ya)是一个(ge)(ge)范围，取最(zui)大值。VMOS的(de)(de)(de)(de)开(kai)启(qi)(qi)(qi)(qi)电(dian)(dian)(dian)压(ya)(ya)(ya)(ya)普(pu)通(tong)(tong)为(wei)(wei)(wei)5V左(zuo)右(you)，低(di)开(kai)启(qi)(qi)(qi)(qi)电(dian)(dian)(dian)压(ya)(ya)(ya)(ya)的(de)(de)(de)(de)种(zhong)类有2V左(zuo)右(you)的(de)(de)(de)(de)。假如采(cai)用5. 5V丁作(zuo)电(dian)(dian)(dian)压(ya)(ya)(ya)(ya)的(de)(de)(de)(de)运放(fang)(fang)，其输出电(dian)(dian)(dian)平最(zui)大约为(wei)(wei)(wei)土2.5V，即便采(cai)用低(di)开(kai)启(qi)(qi)(qi)(qi)电(dian)(dian)(dian)压(ya)(ya)(ya)(ya)的(de)(de)(de)(de)VMOS，如图(tu)2.6中的(de)(de)(de)(de)2SK2313，最(zui)低(di)驱动电(dian)(dian)(dian)平也(ye)至(zhi)少为(wei)(wei)(wei)土5V，因(yin)而依(yi)据(ju)上(shang)文关(guan)于(yu)运放(fang)(fang)的(de)(de)(de)(de)选择准绳，5.5V工作(zuo)电(dian)(dian)(dian)压(ya)(ya)(ya)(ya)的(de)(de)(de)(de)运放(fang)(fang)实践(jian)上(shang)是不能用的(de)(de)(de)(de)，引(yin)荐的(de)(de)(de)(de)工作(zuo)电(dian)(dian)(dian)压(ya)(ya)(ya)(ya)最(zui)低(di)为(wei)(wei)(wei)±6V，由于(yu)运放(fang)(fang)的(de)(de)(de)(de)最(zui)高输出电(dian)(dian)(dian)平通(tong)(tong)常会略低(di)于(yu)工作(zuo)电(dian)(dian)(dian)压(ya)(ya)(ya)(ya)，即便是近年来开(kai)端普(pu)遍应用的(de)(de)(de)(de)“轨(gui)至(zhi)轨(gui)”输入／输出的(de)(de)(de)(de)运放(fang)(fang)也(ye)是如此。

P沟(gou)(gou)(gou)(gou)道(dao)VMOS当然也能用，只是驱动(dong)办(ban)法与N沟(gou)(gou)(gou)(gou)道(dao)相反。不过，直(zhi)到现在(zai)，与N沟(gou)(gou)(gou)(gou)通同一(yi)系列同电(dian)压(ya)规(gui)(gui)格的(de)P沟(gou)(gou)(gou)(gou)通的(de)VMOS，普(pu)通电(dian)流(liu)规(gui)(gui)格比N沟(gou)(gou)(gou)(gou)道(dao)的(de)低(di)，而饱和导通电(dian)压(ya)比N沟(gou)(gou)(gou)(gou)道(dao)高。因而选N沟(gou)(gou)(gou)(gou)道(dao)而不选P沟(gou)(gou)(gou)(gou)道(dao)。

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