在電(dian)(dian)(dian)源適(shi)配器的(de)設(she)計(ji)中電(dian)(dian)(dian)感(gan)(gan)的(de)設(she)計(ji)為工(gong)程(cheng)(cheng)師帶來(lai)的(de)許多的(de)挑戰。工(gong)程(cheng)(cheng)師不僅要(yao)選擇電(dian)(dian)(dian)感(gan)(gan)值，還要(yao)考(kao)慮電(dian)(dian)(dian)感(gan)(gan)可(ke)承受的(de)電(dian)(dian)(dian)流，繞線(xian)電(dian)(dian)(dian)阻，機(ji)械尺(chi)寸等等。接下來(lai)飛天鷹電(dian)(dian)(dian)源適(shi)配器廠家為大家解(jie)釋一下電(dian)(dian)(dian)感(gan)(gan)上的(de)DC電(dian)(dian)(dian)流效(xiao)應，這(zhe)也可(ke)以(yi)為選擇合適(shi)的(de)電(dian)(dian)(dian)感(gan)(gan)提供必要(yao)的(de)信息。

感常常被理解(jie)為(wei)電(dian)(dian)(dian)源適配器輸(shu)(shu)(shu)出端(duan)中(zhong)的(de)(de)LC濾波(bo)電(dian)(dian)(dian)路中(zhong)的(de)(de)L（C是(shi)(shi)其(qi)中(zhong)的(de)(de)輸(shu)(shu)(shu)出電(dian)(dian)(dian)容）。雖然這樣理解(jie)是(shi)(shi)正確的(de)(de)，但是(shi)(shi)為(wei)了理解(jie)電(dian)(dian)(dian)感的(de)(de)設計就必須更深入(ru)的(de)(de)了解(jie)電(dian)(dian)(dian)感的(de)(de)行為(wei)。在(zai)降(jiang)壓(ya)轉換(huan)中(zhong)，電(dian)(dian)(dian)感的(de)(de)一端(duan)是(shi)(shi)連接(jie)到(dao)DC輸(shu)(shu)(shu)出電(dian)(dian)(dian)壓(ya)。另一端(duan)通(tong)過開關(guan)頻率切換(huan)連接(jie)到(dao)輸(shu)(shu)(shu)入(ru)電(dian)(dian)(dian)壓(ya)或GND。

在狀態(tai)1過(guo)程(cheng)中(zhong)，電感(gan)會通過(guo)（高邊 “high-side”）MOSFET連(lian)(lian)接到(dao)(dao)輸入電壓(ya)。在狀態(tai)2過(guo)程(cheng)中(zhong)，電感(gan)連(lian)(lian)接到(dao)(dao)GND。由于使用了這(zhe)類的控制(zhi)器(qi)，可以采用兩種方式(shi)(shi)實(shi)現電感(gan)接地(di)：通過(guo)二極(ji)管接地(di)或通過(guo)（低邊“low-side”）MOSFET接地(di)。如(ru)果是后一種方式(shi)(shi)，轉換器(qi)就(jiu)稱為“同(tong)步（synchronus）”方式(shi)(shi)。

現在(zai)(zai)(zai)再考慮一下在(zai)(zai)(zai)這兩個(ge)狀(zhuang)態下流(liu)過(guo)電(dian)感(gan)(gan)的電(dian)流(liu)是(shi)如果變(bian)化的。在(zai)(zai)(zai)狀(zhuang)態1過(guo)程中，電(dian)感(gan)(gan)的一端(duan)連接到(dao)輸入電(dian)壓(ya)，另一端(duan)連接到(dao)輸出電(dian)壓(ya)。對于(yu)一個(ge)降(jiang)壓(ya)轉(zhuan)換器，輸入電(dian)壓(ya)必須比輸出電(dian)壓(ya)高，因此會在(zai)(zai)(zai)電(dian)感(gan)(gan)上(shang)形成正(zheng)向壓(ya)降(jiang)。相反，在(zai)(zai)(zai)狀(zhuang)態2過(guo)程中，原來連接到(dao)輸入電(dian)壓(ya)的電(dian)感(gan)(gan)一端(duan)被連接到(dao)地。對于(yu)一個(ge)降(jiang)壓(ya)轉(zhuan)換器，輸出電(dian)壓(ya)必然為(wei)正(zheng)端(duan)，因此會在(zai)(zai)(zai)電(dian)感(gan)(gan)上(shang)形成負向的壓(ya)降(jiang)。我們利用電(dian)感(gan)(gan)上(shang)電(dian)壓(ya)計算(suan)公式：V=L(dI/dt)

因此，當(dang)電(dian)(dian)感(gan)上(shang)的(de)電(dian)(dian)壓為(wei)正時（狀態1），電(dian)(dian)感(gan)上(shang)的(de)電(dian)(dian)流就會增加；當(dang)電(dian)(dian)感(gan)上(shang)的(de)電(dian)(dian)壓為(wei)負時（狀態2），電(dian)(dian)感(gan)上(shang)的(de)電(dian)(dian)流就會減小(xiao)。通過電(dian)(dian)感(gan)的(de)電(dian)(dian)流如圖(tu)2所示：

通過上圖(tu)我(wo)們(men)可以看到，流(liu)(liu)過電感的(de)最(zui)大電流(liu)(liu)為DC電流(liu)(liu)加開(kai)(kai)(kai)關(guan)峰峰電流(liu)(liu)的(de)一(yi)半(ban)。上圖(tu)也稱為紋(wen)波(bo)電流(liu)(liu)。根據上述(shu)的(de)公式(shi)，我(wo)們(men)可以計算出峰值電流(liu)(liu)：其中(zhong)，ton是狀態1的(de)時間，T是開(kai)(kai)(kai)關(guan)周期（開(kai)(kai)(kai)關(guan)頻率的(de)倒(dao)數），DC為狀態1的(de)占(zhan)空比。

通過(guo)已經計算的(de)(de)電(dian)(dian)(dian)(dian)(dian)感(gan)(gan)峰值電(dian)(dian)(dian)(dian)(dian)流(liu)，我們可以(yi)發現電(dian)(dian)(dian)(dian)(dian)感(gan)(gan)上產生了(le)(le)什么(me)。很(hen)容易會(hui)知道(dao)，隨著通過(guo)電(dian)(dian)(dian)(dian)(dian)感(gan)(gan)的(de)(de)電(dian)(dian)(dian)(dian)(dian)流(liu)增加，它的(de)(de)電(dian)(dian)(dian)(dian)(dian)感(gan)(gan)量會(hui)減小(xiao)(xiao)。這是(shi)由于(yu)磁(ci)芯材料(liao)的(de)(de)物(wu)理特性決定的(de)(de)。電(dian)(dian)(dian)(dian)(dian)感(gan)(gan)量會(hui)減少多(duo)少就很(hen)重要(yao)了(le)(le)：如果電(dian)(dian)(dian)(dian)(dian)感(gan)(gan)量減小(xiao)(xiao)很(hen)多(duo)，轉(zhuan)換(huan)器(qi)就不會(hui)正常工作(zuo)了(le)(le)。當(dang)通過(guo)電(dian)(dian)(dian)(dian)(dian)感(gan)(gan)的(de)(de)電(dian)(dian)(dian)(dian)(dian)流(liu)大到(dao)電(dian)(dian)(dian)(dian)(dian)感(gan)(gan)實效的(de)(de)程度，此時的(de)(de)電(dian)(dian)(dian)(dian)(dian)流(liu)稱(cheng)為“飽和電(dian)(dian)(dian)(dian)(dian)流(liu)”。這也是(shi)電(dian)(dian)(dian)(dian)(dian)感(gan)(gan)的(de)(de)基本(ben)參數。

實(shi)際上，轉換(huan)電(dian)路中的(de)(de)開關功率電(dian)感總會有一個“軟(ruan)(ruan)”飽和度。要了(le)解這(zhe)個概念(nian)可(ke)以觀察實(shi)際測量的(de)(de)電(dian)感Vs DC電(dian)流(liu)(liu)的(de)(de)曲線：當電(dian)流(liu)(liu)增加到(dao)(dao)一定程度后，電(dian)感量就(jiu)不會急劇(ju)下(xia)降了(le)，這(zhe)就(jiu)稱為“軟(ruan)(ruan)”飽和特性。如果電(dian)流(liu)(liu)再增加，電(dian)感就(jiu)會損(sun)壞(huai)了(le)。相關的(de)(de)知(zhi)識(shi)今天就(jiu)分(fen)享到(dao)(dao)這(zhe)里，想要了(le)解更(geng)多的(de)(de)電(dian)源適配(pei)器(qi)的(de)(de)知(zhi)識(shi)，大家(jia)可(ke)以關注飛天鷹科技(ji)。