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地点:深圳市(shi)宝安区西乡侨鸿(hong)盛(sheng)文明创意园写字楼A栋614-616
文(wen)章概况

DC-DC升压和降压电路电感参数挑选详解

日期:2021-09-01 19:32
阅读次数:2679
择要:

DC-DC升压和降压电路电感参数挑选详解

      
注:只要充实懂得电感在DC-DC电路中阐扬的感化,能力更优的设想DC-DC电路。本文还包含对同步DC-DC及异步DC-DC观点的诠释。DC-DC电路电感参数挑选详解
 
DC-DC电路电感的挑选简介
   在开(kai)关电(dian)源(yuan)的设想(xiang)中电(dian)感(gan)(gan)的设想(xiang)为工程(cheng)师带来的良多的挑(tiao)衅。工程(cheng)师不只要挑(tiao)选电(dian)感(gan)(gan)值,还要斟酌电(dian)感(gan)(gan)可蒙受的电(dian)流,绕线电(dian)阻,机(ji)器尺寸等等。本(ben)文专一(yi)于诠释:电(dian)感(gan)(gan)上(shang)的DC电(dian)流效应。这也会为挑(tiao)选适合(he)的电(dian)感(gan)(gan)供给须要的信息。
 
懂得电感的功效
   电(dian)感经(jing)常被懂得为开关(guan)电(dian)源(yuan)输入(ru)端中的(de)LC滤波电(dian)路中的(de)L(C是(shi)此中的(de)输入(ru)电(dian)容)。固然如许(xu)懂得是(shi)准确(que)的(de),可(ke)是(shi)为了懂得电(dian)感的(de)设(she)想就必须更深(shen)切的(de)领会电(dian)感的(de)行动。
   在降压(ya)(ya)转换中(Fairchild典(dian)范(fan)的开关(guan)节制器),电(dian)(dian)感(gan)的一端(duan)是毗连到(dao)(dao)DC输(shu)(shu)入电(dian)(dian)压(ya)(ya)。另(ling)外一端(duan)经由进程开关(guan)频次切(qie)换毗连到(dao)(dao)输(shu)(shu)入电(dian)(dian)压(ya)(ya)或GND。
   在状况1进程中,电感会经由进程(高边“high-side”)MOSFET毗连到输入电压。在状况2进程中,电感毗连到GND。由于操纵了这类的节制器,能够接纳两种体例完成电感接地:经由进程二极管接地或经由进程(低边“low-side”)MOSFET接地。若是是后一种体例,转换器就称为“同步(synchronus)”体例。DC-DC电路(lu)电感(gan)参数挑选详解
  此刻(ke)再(zai)斟酌(zhuo)一下在(zai)这(zhei)两个(ge)状(zhuang)况下贱过电(dian)(dian)(dian)感(gan)(gan)(gan)的电(dian)(dian)(dian)流是(shi)若是(shi)变更(geng)的。在(zai)状(zhuang)况1进程中(zhong),电(dian)(dian)(dian)感(gan)(gan)(gan)的一端(duan)(duan)(duan)毗(pi)连到输(shu)入(ru)(ru)电(dian)(dian)(dian)压(ya)(ya)(ya)(ya)(ya),另(ling)外一端(duan)(duan)(duan)毗(pi)连到输(shu)入(ru)(ru)电(dian)(dian)(dian)压(ya)(ya)(ya)(ya)(ya)。对一个(ge)降压(ya)(ya)(ya)(ya)(ya)转(zhuan)换器,输(shu)入(ru)(ru)电(dian)(dian)(dian)压(ya)(ya)(ya)(ya)(ya)必须比输(shu)入(ru)(ru)电(dian)(dian)(dian)压(ya)(ya)(ya)(ya)(ya)高(gao),是(shi)以会在(zai)电(dian)(dian)(dian)感(gan)(gan)(gan)上(shang)构(gou)成正向(xiang)压(ya)(ya)(ya)(ya)(ya)降。相反,在(zai)状(zhuang)况2进程中(zhong),本来毗(pi)连到输(shu)入(ru)(ru)电(dian)(dian)(dian)压(ya)(ya)(ya)(ya)(ya)的电(dian)(dian)(dian)感(gan)(gan)(gan)一端(duan)(duan)(duan)被毗(pi)连到地。对一个(ge)降压(ya)(ya)(ya)(ya)(ya)转(zhuan)换器,输(shu)入(ru)(ru)电(dian)(dian)(dian)压(ya)(ya)(ya)(ya)(ya)必然(ran)为正端(duan)(duan)(duan),是(shi)以会在(zai)电(dian)(dian)(dian)感(gan)(gan)(gan)上(shang)构(gou)成负向(xiang)的压(ya)(ya)(ya)(ya)(ya)降。
咱们操纵电感上电压计较公式:DC-DC电路(lu)电感参(can)数挑选详解
V=L(dI/dt)
   是以,当(dang)(dang)电(dian)(dian)感(gan)上的(de)电(dian)(dian)压为正(zheng)时(状况1),电(dian)(dian)感(gan)上的(de)电(dian)(dian)流(liu)就会(hui)增添;当(dang)(dang)电(dian)(dian)感(gan)上的(de)电(dian)(dian)压为负时(状况2),电(dian)(dian)感(gan)上的(de)电(dian)(dian)流(liu)就会(hui)减小。经(jing)由进程电(dian)(dian)感(gan)的(de)电(dian)(dian)流(liu)如图2所(suo)示(shi):
   经由进程上(shang)图咱(zan)们能够看(kan)到,流(liu)(liu)过电感的(de)(de)(de)*大(da)电流(liu)(liu)为DC电流(liu)(liu)加开关峰峰电流(liu)(liu)的(de)(de)(de)一半。上(shang)图也称为纹波电流(liu)(liu)。按照(zhao)上(shang)述的(de)(de)(de)公式,咱(zan)们能够计较出峰值(zhi)电流(liu)(liu):
   此中,ton是状况1的时候,T是开关周期(开关频次的倒数),DC为状况1的占空比。
 
   正(zheng)告:下(xia)面的(de)计较(jiao)是(shi)假定各元(yuan)器件(MOSFET上的(de)导(dao)通(tong)压(ya)(ya)(ya)降,电(dian)(dian)感的(de)导(dao)通(tong)压(ya)(ya)(ya)降或异步电(dian)(dian)路中肖特基二极管的(de)正(zheng)向(xiang)压(ya)(ya)(ya)降)上的(de)压(ya)(ya)(ya)降对(dui)照(zhao)输(shu)入和输(shu)入电(dian)(dian)压(ya)(ya)(ya)是(shi)能(neng)够疏忽的(de)。
若是,器件的降落不可疏忽,就要(yao)用以(yi)下公式作**计较:
同(tong)步转换电(dian)路:
异步转换电路(lu):
   此(ci)中,Rs为感(gan)到电(dian)(dian)阻阻抗加(jia)电(dian)(dian)感(gan)绕(rao)线电(dian)(dian)阻的(de)阻。Vf是肖(xiao)特基二极管的(de)正向(xiang)压降。R是Rs加(jia)MOSFET导通电(dian)(dian)阻,R=Rs+Rm。
电感磁芯的饱和度
   经(jing)(jing)由(you)(you)进(jin)程(cheng)已计较的(de)电(dian)(dian)感(gan)(gan)峰值电(dian)(dian)流(liu)(liu)(liu),咱们(men)能(neng)够发明电(dian)(dian)感(gan)(gan)上发生了甚(shen)么。很轻易(yi)会晓得,跟着经(jing)(jing)由(you)(you)进(jin)程(cheng)电(dian)(dian)感(gan)(gan)的(de)电(dian)(dian)流(liu)(liu)(liu)增添,它的(de)电(dian)(dian)感(gan)(gan)量会减小。这是由(you)(you)于磁芯材料的(de)物理特征决(jue)议的(de)。电(dian)(dian)感(gan)(gan)量会削减几多就很主要(yao)了:若是电(dian)(dian)感(gan)(gan)量减小良多,转换(huan)器就不会一(yi)般(ban)任务了。当经(jing)(jing)由(you)(you)进(jin)程(cheng)电(dian)(dian)感(gan)(gan)的(de)电(dian)(dian)流(liu)(liu)(liu)大到电(dian)(dian)感(gan)(gan)实效的(de)水平(ping),此时(shi)的(de)电(dian)(dian)流(liu)(liu)(liu)称为“饱和(he)电(dian)(dian)流(liu)(liu)(liu)”。这也是电(dian)(dian)感(gan)(gan)的(de)根基参数。
   现(xian)(xian)实(shi)上,转换电(dian)路中的(de)开关功率电(dian)感总会有一个(ge)“软”饱和度(du)。要(yao)领会这个(ge)观点能够察(cha)看现(xian)(xian)实(shi)丈量的(de)电(dian)感VsDC电(dian)流的(de)曲线(xian):
   当电流增(zeng)添到必然水平后(hou),电感量(liang)就不会(hui)急剧(ju)降落了(le),这就称为“软”饱和特征。若是电流再(zai)增(zeng)添,电感就会(hui)破坏了(le)。
   注重:电(dian)(dian)感(gan)量降落(luo)在(zai)良多类(lei)的电(dian)(dian)感(gan)中城市存在(zai)。比方:toroids,gappedE-cores等(deng)。可是,rodcore电(dian)(dian)感(gan)就不会有(you)这类(lei)变更。
有了这个软饱和的特(te)征,咱们就能够晓得在(zai)一切的转换器中(zhong)为(wei)甚么城(cheng)市划定(ding)在(zai)DC输(shu)入电(dian)流下(xia)的*小(xiao)电(dian)感(gan)(gan)量(liang);并且由(you)于(yu)(yu)纹(wen)(wen)波(bo)电(dian)流的变更(geng)也不会严峻(jun)影响(xiang)电(dian)感(gan)(gan)量(liang)。在(zai)一切的利用中(zhong)都但愿纹(wen)(wen)波(bo)电(dian)流尽可能的小(xiao),由(you)于(yu)(yu)它会影响(xiang)输(shu)入电(dian)压的纹(wen)(wen)波(bo)。这也便是为(wei)甚么大师老是很关(guan)怀DC输(shu)入电(dian)流下(xia)的电(dian)感(gan)(gan)量(liang),而会在(zai)Spec中(zhong)疏忽纹(wen)(wen)波(bo)电(dian)流下(xia)的电(dian)感(gan)(gan)量(liang)。
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