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大功率濾波電容的主要作用
大功率濾波電容主要分為有源濾波器和無源濾波器。主要作用是讓有用信號盡可能無衰減的通過,對無用信號盡可能大的反射。濾波器一般有兩個端口,一個輸入信號、一個輸出信號,利用這個特性可以選通通過濾波器的一個方波群或復合噪波,而得到一個特定頻率的正弦波。濾波器的功能就是允許某一部分頻率的信號順利的通過,而另外一部分頻率的信號則受到較大的抑制,它實質上是一個選頻電路。
大(da)功率(lv)濾(lv)(lv)波(bo)(bo)電(dian)(dian)(dian)容中(zhong),把信號能夠(gou)通(tong)(tong)過的(de)(de)(de)頻(pin)率(lv)范圍,稱(cheng)為通(tong)(tong)頻(pin)帶(dai)(dai)(dai)或通(tong)(tong)帶(dai)(dai)(dai);反之(zhi),信號受到很大(da)衰(shuai)減或完全被抑制的(de)(de)(de)頻(pin)率(lv)范圍稱(cheng)為阻帶(dai)(dai)(dai);通(tong)(tong)帶(dai)(dai)(dai)和(he)阻帶(dai)(dai)(dai)之(zhi)間的(de)(de)(de)分界頻(pin)率(lv)稱(cheng)為截(jie)止頻(pin)率(lv);濾(lv)(lv)波(bo)(bo)器(qi)(qi)(qi)(qi)是由電(dian)(dian)(dian)感(gan)器(qi)(qi)(qi)(qi)和(he)電(dian)(dian)(dian)容器(qi)(qi)(qi)(qi)構成的(de)(de)(de)網路,可(ke)使混(hun)合的(de)(de)(de)交直流(liu)(liu)(liu)電(dian)(dian)(dian)流(liu)(liu)(liu)分開。電(dian)(dian)(dian)源整流(liu)(liu)(liu)器(qi)(qi)(qi)(qi)中(zhong),即借(jie)助此網路濾(lv)(lv)凈脈動直流(liu)(liu)(liu)中(zhong)的(de)(de)(de)漣波(bo)(bo),而獲得比(bi)較純凈的(de)(de)(de)直流(liu)(liu)(liu)輸出(chu)。較基本(ben)的(de)(de)(de)濾(lv)(lv)波(bo)(bo)器(qi)(qi)(qi)(qi),是由一個(ge)電(dian)(dian)(dian)容器(qi)(qi)(qi)(qi)和(he)一個(ge)電(dian)(dian)(dian)感(gan)器(qi)(qi)(qi)(qi)構成,稱(cheng)為L型(xing)(xing)濾(lv)(lv)波(bo)(bo)。所(suo)有各型(xing)(xing)的(de)(de)(de)濾(lv)(lv)波(bo)(bo)器(qi)(qi)(qi)(qi),都是集合L型(xing)(xing)單(dan)(dan)節濾(lv)(lv)波(bo)(bo)器(qi)(qi)(qi)(qi)而成。基本(ben)單(dan)(dan)節式(shi)濾(lv)(lv)波(bo)(bo)器(qi)(qi)(qi)(qi)由一個(ge)串聯臂及(ji)一個(ge)并聯臂所(suo)組成,串聯臂為電(dian)(dian)(dian)感(gan)器(qi)(qi)(qi)(qi),并聯臂為電(dian)(dian)(dian)容器(qi)(qi)(qi)(qi)。在(zai)電(dian)(dian)(dian)源及(ji)聲頻(pin)電(dian)(dian)(dian)路中(zhong)之(zhi)濾(lv)(lv)波(bo)(bo)器(qi)(qi)(qi)(qi),通(tong)(tong)用者(zhe)為L型(xing)(xing)及(ji)π型(xing)(xing)兩種。就L型(xing)(xing)單(dan)(dan)節濾(lv)(lv)波(bo)(bo)器(qi)(qi)(qi)(qi)而言(yan),其電(dian)(dian)(dian)感(gan)抗XL與電(dian)(dian)(dian)容抗XC,對任一頻(pin)率(lv)為一常數,其關系為XL·XC=K2。
理想(xiang)的(de)(de)(de)低通(tong)(tong)濾波(bo)(bo)器應(ying)(ying)該(gai)能使所有低于(yu)截止(zhi)頻率的(de)(de)(de)信(xin)號無(wu)損通(tong)(tong)過(guo),而所有高于(yu)截止(zhi)頻率的(de)(de)(de)信(xin)號都應(ying)(ying)該(gai)被無(wu)限(xian)的(de)(de)(de)衰(shuai)減,從而在幅頻特性(xing)曲線上呈(cheng)現(xian)矩(ju)形,故而也(ye)稱為矩(ju)形濾波(bo)(bo)器。遺憾的(de)(de)(de)是(shi),如(ru)此理想(xiang)的(de)(de)(de)特性(xing)是(shi)無(wu)法實現(xian)的(de)(de)(de),所有的(de)(de)(de)設(she)計只不(bu)過(guo)是(shi)力(li)圖逼(bi)近(jin)矩(ju)形濾波(bo)(bo)器的(de)(de)(de)特性(xing)而已。根據所選的(de)(de)(de)逼(bi)近(jin)函數的(de)(de)(de)不(bu)同,可以得到(dao)不(bu)同的(de)(de)(de)響(xiang)應(ying)(ying)。雖然逼(bi)近(jin)函數多(duo)種多(duo)樣,但是(shi)考(kao)慮到(dao)實際電路的(de)(de)(de)使用需(xu)求,通(tong)(tong)常會選用“巴(ba)特沃斯響(xiang)應(ying)(ying)”或“切比(bi)雪(xue)夫響(xiang)應(ying)(ying)”。