功率因数校正

功率因数校正简介

PFC的(de)英文全称为“Power Factor Correction”，意思是(shi)(shi)“功(gong)(gong)率(lv)因(yin)数(shu)校正”，功(gong)(gong)率(lv)因(yin)数(shu)指的(de)是(shi)(shi)有效(xiao)功(gong)(gong)率(lv)与(yu)总(zong)耗(hao)电量(liang)(liang)(liang)（视(shi)在(zai)(zai)功(gong)(gong)率(lv)）之间的(de)关(guan)系，也(ye)就(jiu)是(shi)(shi)有效(xiao)功(gong)(gong)率(lv)除以总(zong)耗(hao)电量(liang)(liang)(liang)（视(shi)在(zai)(zai)功(gong)(gong)率(lv)）的(de)比值(zhi)。 基本(ben)上功(gong)(gong)率(lv)因(yin)数(shu)可以衡量(liang)(liang)(liang)电力被有效(xiao)利用(yong)的(de)程度，当功(gong)(gong)率(lv)因(yin)数(shu)值(zhi)越(yue)大，代(dai)表其电力利用(yong)率(lv)越(yue)高。

功(gong)率(lv)因数是用来衡量用电设备(bei)用电效率(lv)的(de)参(can)数，低功(gong)率(lv)因数代(dai)表低电力效能。为了(le)提高用电设备(bei)功(gong)率(lv)因数的(de)技术(shu)就称为功(gong)率(lv)因数校正(zheng)。

计算机开(kai)关电(dian)源是一(yi)种(zhong)电(dian)容(rong)输入型电(dian)路(lu)，其电(dian)流和电(dian)压(ya)之间(jian)的(de)相位差会造成交(jiao)换功(gong)率(lv)的(de)损失，此时(shi)便需要PFC电(dian)路(lu)提高功(gong)率(lv)因数。目(mu)前的(de)PFC有两种(zhong)，一(yi)种(zhong)为被(bei)动式(shi)(shi)PFC（也称(cheng)无(wu)源PFC）和主动式(shi)(shi)PFC（也称(cheng)有源式(shi)(shi)PFC）。

功率因数校正电路工作原理

功(gong)率(lv)因数校正补偿：在(zai)上(shang)世纪(ji)五十年(nian)代，已经(jing)针对具(ju)有感(gan)性负(fu)(fu)载(zai)的(de)(de)(de)(de)(de)交流(liu)(liu)用(yong)电(dian)(dian)(dian)(dian)器(qi)(qi)具(ju)的(de)(de)(de)(de)(de)电(dian)(dian)(dian)(dian)压和(he)(he)电(dian)(dian)(dian)(dian)流(liu)(liu)不(bu)同相（图1）从(cong)而引起的(de)(de)(de)(de)(de)供电(dian)(dian)(dian)(dian)效率(lv)低下(xia)提出了改(gai)进(jin)方法（由于(yu)感(gan)性负(fu)(fu)载(zai)的(de)(de)(de)(de)(de)电(dian)(dian)(dian)(dian)流(liu)(liu)滞后所加电(dian)(dian)(dian)(dian)压，由于(yu)电(dian)(dian)(dian)(dian)压和(he)(he)电(dian)(dian)(dian)(dian)流(liu)(liu)的(de)(de)(de)(de)(de)相位(wei)不(bu)同使(shi)供电(dian)(dian)(dian)(dian)线(xian)(xian)路的(de)(de)(de)(de)(de)负(fu)(fu)担加重导致供电(dian)(dian)(dian)(dian)线(xian)(xian)路效率(lv)下(xia)降，这就要(yao)求在(zai)感(gan)性用(yong)电(dian)(dian)(dian)(dian)器(qi)(qi)具(ju)上(shang)并(bing)联一个电(dian)(dian)(dian)(dian)容(rong)(rong)器(qi)(qi)用(yong)以(yi)调(diao)整其该用(yong)电(dian)(dian)(dian)(dian)器(qi)(qi)具(ju)的(de)(de)(de)(de)(de)电(dian)(dian)(dian)(dian)压、电(dian)(dian)(dian)(dian)流(liu)(liu)相位(wei)特(te)性，例如：当(dang)时要(yao)求所使(shi)用(yong)的(de)(de)(de)(de)(de)40W日光灯必须并(bing)联一个4.75μF的(de)(de)(de)(de)(de)电(dian)(dian)(dian)(dian)容(rong)(rong)器(qi)(qi)）。用(yong)电(dian)(dian)(dian)(dian)容(rong)(rong)器(qi)(qi)并(bing)连在(zai)感(gan)性负(fu)(fu)载(zai)，利用(yong)其电(dian)(dian)(dian)(dian)容(rong)(rong)上(shang)电(dian)(dian)(dian)(dian)流(liu)(liu)超前电(dian)(dian)(dian)(dian)压的(de)(de)(de)(de)(de)特(te)性用(yong)以(yi)补偿电(dian)(dian)(dian)(dian)感(gan)上(shang)电(dian)(dian)(dian)(dian)流(liu)(liu)滞后电(dian)(dian)(dian)(dian)压的(de)(de)(de)(de)(de)特(te)性来使(shi)总的(de)(de)(de)(de)(de)特(te)性接(jie)近于(yu)阻性，从(cong)而改(gai)善(shan)效率(lv)低下(xia)的(de)(de)(de)(de)(de)方法叫功(gong)率(lv)因数补偿（交流(liu)(liu)电(dian)(dian)(dian)(dian)的(de)(de)(de)(de)(de)功(gong)率(lv)因数可以(yi)用(yong)电(dian)(dian)(dian)(dian)源电(dian)(dian)(dian)(dian)压与负(fu)(fu)载(zai)电(dian)(dian)(dian)(dian)流(liu)(liu)两者相位(wei)角的(de)(de)(de)(de)(de)余弦函数值cosφ表示）。

图1

在具有感性(xing)负载中(zhong)供(gong)电线路中(zhong)电压和电流的波形(xing)

而(er)在上世纪80年代起，用电(dian)器(qi)具大量的采(cai)用效率高的开关电(dian)源，由于开关电(dian)源都是在整流后用一个大容(rong)量的滤波电(dian)容(rong)，使该用电(dian)器(qi)具的负载特性(xing)呈现(xian)容(rong)性(xing)，这就造成了交流220V在对该用电(dian)器(qi)具供电(dian)时，由于滤波电(dian)容(rong)的充、放(fang)电(dian)作用，在其两端的直(zhi)流电(dian)压(ya)出现(xian)略呈锯齿(chi)波的纹波。

滤波(bo)(bo)电(dian)(dian)(dian)(dian)(dian)(dian)容上电(dian)(dian)(dian)(dian)(dian)(dian)压(ya)的(de)(de)(de)最小值(zhi)远非为零，与其最大(da)值(zhi)(纹波(bo)(bo)峰值(zhi))相差并不多。根据整流(liu)(liu)二(er)极(ji)管的(de)(de)(de)单(dan)向导(dao)电(dian)(dian)(dian)(dian)(dian)(dian)性，只有在AC线(xian)路(lu)电(dian)(dian)(dian)(dian)(dian)(dian)压(ya)瞬时值(zhi)高于滤波(bo)(bo)电(dian)(dian)(dian)(dian)(dian)(dian)容上的(de)(de)(de)电(dian)(dian)(dian)(dian)(dian)(dian)压(ya)时，整流(liu)(liu)二(er)极(ji)管才(cai)(cai)会因正向偏(pian)置而导(dao)通(tong)，而当AC输(shu)入(ru)电(dian)(dian)(dian)(dian)(dian)(dian)压(ya)瞬时值(zhi)低于滤波(bo)(bo)电(dian)(dian)(dian)(dian)(dian)(dian)容上的(de)(de)(de)电(dian)(dian)(dian)(dian)(dian)(dian)压(ya)时，整流(liu)(liu)二(er)极(ji)管因反向偏(pian)置而截止。也就是(shi)说(shuo)，在AC线(xian)路(lu)电(dian)(dian)(dian)(dian)(dian)(dian)压(ya)的(de)(de)(de)每个半(ban)周期(qi)内(nei)，只是(shi)在其峰值(zhi)附近，二(er)极(ji)管才(cai)(cai)会导(dao)通(tong)。虽(sui)然AC输(shu)入(ru)电(dian)(dian)(dian)(dian)(dian)(dian)压(ya)仍大(da)体保持正弦波(bo)(bo)波(bo)(bo)形(xing)，但AC输(shu)入(ru)电(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)却(que)呈高幅值(zhi)的(de)(de)(de)尖峰脉冲，如图2所示。这种严重失(shi)真的(de)(de)(de)电(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)波(bo)(bo)形(xing)含(han)有大(da)量的(de)(de)(de)谐波(bo)(bo)成份(fen)，引起(qi)线(xian)路(lu)功率因数严重下降。

在正(zheng)半个(ge)周期内(nei)（1800），整流二极(ji)管的(de)(de)(de)导(dao)通角大大的(de)(de)(de)小于1800甚至只有(you)300－700，由于要(yao)保证(zheng)负(fu)(fu)载功(gong)率的(de)(de)(de)要(yao)求，在极(ji)窄的(de)(de)(de)导(dao)通角期间会(hui)产生(sheng)极(ji)大的(de)(de)(de)导(dao)通电(dian)(dian)(dian)(dian)流，使(shi)供(gong)电(dian)(dian)(dian)(dian)电(dian)(dian)(dian)(dian)路(lu)中的(de)(de)(de)供(gong)电(dian)(dian)(dian)(dian)电(dian)(dian)(dian)(dian)流呈脉冲状态，它(ta)不(bu)仅降低了(le)供(gong)电(dian)(dian)(dian)(dian)的(de)(de)(de)效率，更为严(yan)重的(de)(de)(de)是它(ta)在供(gong)电(dian)(dian)(dian)(dian)线路(lu)容(rong)量不(bu)足，或电(dian)(dian)(dian)(dian)路(lu)负(fu)(fu)载较大时会(hui)产生(sheng)严(yan)重的(de)(de)(de)交流电(dian)(dian)(dian)(dian)压的(de)(de)(de)波(bo)形(xing)畸变（图3），并产生(sheng)多(duo)次(ci)谐波(bo)，从(cong)而，干(gan)扰了(le)其(qi)它(ta)用电(dian)(dian)(dian)(dian)器具的(de)(de)(de)正(zheng)常工作（这就是电(dian)(dian)(dian)(dian)磁干(gan)扰－EMI和电(dian)(dian)(dian)(dian)磁兼(jian)容(rong)－EMC问题）。

图2

自从用(yong)电(dian)(dian)(dian)(dian)器具(ju)从过(guo)去的(de)(de)感(gan)性负载（早期的(de)(de)电(dian)(dian)(dian)(dian)视机、收(shou)音机等(deng)的(de)(de)电(dian)(dian)(dian)(dian)源(yuan)均采用(yong)电(dian)(dian)(dian)(dian)源(yuan)变压(ya)(ya)器的(de)(de)感(gan)性器件）变成带整流(liu)(liu)及滤波电(dian)(dian)(dian)(dian)容器的(de)(de)容性负载后，其功率因素补偿的(de)(de)含(han)义不(bu)(bu)仅是(shi)供电(dian)(dian)(dian)(dian)的(de)(de)电(dian)(dian)(dian)(dian)压(ya)(ya)和电(dian)(dian)(dian)(dian)流(liu)(liu)不(bu)(bu)同相位(wei)的(de)(de)问(wen)题，更(geng)为(wei)严重的(de)(de)是(shi)要解决因供电(dian)(dian)(dian)(dian)电(dian)(dian)(dian)(dian)流(liu)(liu)呈强脉冲状态而引起的(de)(de)电(dian)(dian)(dian)(dian)磁干扰(rao)（EMI）和电(dian)(dian)(dian)(dian)磁兼容（EMC）问(wen)题。

这就是(shi)在上世纪末发展起来(lai)的一项(xiang)新技(ji)术（其(qi)背景源(yuan)于开关电(dian)(dian)(dian)源(yuan)的迅速(su)发展和(he)广泛应用）。其(qi)主要目(mu)的是(shi)解决因容性(xing)负载导(dao)致(zhi)电(dian)(dian)(dian)流(liu)波形(xing)严(yan)重畸变而产(chan)生的电(dian)(dian)(dian)磁干(gan)扰(rao)(EMl)和(he)电(dian)(dian)(dian)磁兼容(EMC)问题。所以现代的PFC技(ji)术完全(quan)不(bu)同于过(guo)去的功率(lv)因数(shu)补偿技(ji)术，它是(shi)针对(dui)非正弦电(dian)(dian)(dian)流(liu)波形(xing)畸变而采(cai)取的，迫使交流(liu)线(xian)路(lu)电(dian)(dian)(dian)流(liu)追踪电(dian)(dian)(dian)压波形(xing)瞬时变化(hua)轨迹，并使电(dian)(dian)(dian)流(liu)和(he)电(dian)(dian)(dian)压保持同相位，使系统呈纯电(dian)(dian)(dian)阻性(xing)技(ji)术（线(xian)路(lu)电(dian)(dian)(dian)流(liu)波形(xing)校(xiao)正技(ji)术），这就是(shi)PFC（功率(lv)因数(shu)校(xiao)正）。

所以(yi)现(xian)代(dai)的PFC技(ji)术(shu)完成了电流(liu)波形的校正也(ye)解决了电压、电流(liu)的同(tong)相问题(ti)。

图3

于以上原因，要求用(yong)电(dian)功率(lv)大于85W以上（有的(de)资料显示大于75W）的(de)容性(xing)(xing)负载(zai)用(yong)电(dian)器具，必须(xu)增加校正其负载(zai)特(te)性(xing)(xing)的(de)校正电(dian)路，使其负载(zai)特(te)性(xing)(xing)接(jie)近(jin)于阻性(xing)(xing)（电(dian)压和电(dian)流波(bo)形(xing)同相且波(bo)形(xing)相近(jin)）。这就是现代的(de)功率(lv)因数校正（PFC）电(dian)路。

功率因数校正电路图

功率因数校正电路专用碳化硅二极管-利盈娱乐（KIA）半导体

PFC电(dian)路(lu)专用碳(tan)化(hua)硅二极管型号如下(xia)：

KIA半导体碳化硅二极管产品特点

KIA半导体设计生产(chan)的(de)(de)碳化(hua)硅二(er)(er)极管(guan)具(ju)(ju)有较短的(de)(de)恢复(fu)时(shi)间、温度对于(yu)开(kai)关(guan)行(xing)为的(de)(de)影响较小(xiao)、标准工(gong)作温度范围(wei)为-55℃到175℃，大(da)大(da)降低散热器的(de)(de)需求。碳化(hua)硅二(er)(er)极管(guan)的(de)(de)主要优势在于(yu)它具(ju)(ju)有超快(kuai)的(de)(de)开(kai)关(guan)速度且无反向(xiang)恢复(fu)电流(liu)，与硅器件相(xiang)比，它能(neng)够大(da)大(da) 降低开(kai)关(guan)损耗并实现卓(zhuo)越的(de)(de)能(neng)效。更快(kuai)的(de)(de)开(kai)关(guan)速度同时(shi)也能(neng)让制(zhi)造(zao)商减(jian)小(xiao)产(chan)品(pin)电磁线圈以及相(xiang)关(guan)无源组(zu)件的(de)(de)尺寸，从而提高组(zu)装效率(lv)，减(jian)轻系统(tong)重量，并降低物料（BOM）成本(ben)。

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