看了下UCC28060的spec,在功能框圖里,它的cs腳只用來做過流保護(hù),似乎并沒有參與電流環(huán),那它是如何實(shí)現(xiàn)PFC?
【問】UCC28060疑問
全部回復(fù)(2)
正序查看
倒序查看
Current sense input: Connect the current sense resistor and the negative terminal of the diode bridge to this pin. Connect the return of the current sense resistor to the AGND pin with a separate trace. As input current increases, the voltage on CS goes more negative. This cycle-by-cycle over-current protection limits input current by turning off both gate driver (GDx) outputs when CS is more negative than the CS rising threshold (approximately –200 mV). The GD outputs remain low until CS falls to the CS 10 I CfoSllofwalilninggththerefaslhlionlgde(adpgperoofxiemitahteerlyG–D15oumtpVu)t.. CTuhrisrebnltasnekninsgefiisltebrlsannkoeisdefothraatpopcrcouxrims watheelyn1c0u0rrnesnt switches from a power FET to a boost diode. In most cases, no additional current sense filtering is required. If filtering is required, the filter series resistance must be under 100 Ω to maintain accuracy. To prevent excessive negative voltage on the CS pin during inrush conditions, connect the current sensing resistor to the CS pin through a low value external resistor. As with the filter series resistance, this external resistor needs to be under 100 Ω to maintain accuracy.
這個(gè)是datasheet的引腳功能摘錄,明顯看出這個(gè)電流檢測(cè)還是參與了控制
0
回復(fù)
看看規(guī)格書中CS端的定義就知道了
CS: 電流檢測(cè)輸入,接到電流檢測(cè)電阻和整流橋的負(fù)端。電流檢測(cè)電阻的回流端用獨(dú)立軌跡接到模擬地。隨著電流的增大,CS上的電壓在增高,變得更負(fù)。這個(gè)逐個(gè)周期式過流保護(hù)限制輸入電流,它去關(guān)斷兩路柵驅(qū)動(dòng)脈沖。此時(shí)CS的電壓會(huì)超出-200mV閾值,輸出保持低電平直到CS端降回-15mv閾值。電流檢測(cè)信號(hào)被消隱100ns,跟隨每個(gè)GD脈沖的下降沿。這個(gè)消隱濾除在電流開關(guān)從MOSFET到升壓二極管時(shí)的噪聲。在多數(shù)情況下,沒有附加電流檢測(cè)濾波器的要求,如果需要可串一電阻,阻值在100Ω以下,以保持精度。為防止過負(fù)的電壓在CS端出現(xiàn),接在電流檢測(cè)電阻到CS端可用一低值外部電阻,此電阻小于100Ω以保持精度。
說明CS端還是有參與電流環(huán)控制的
0
回復(fù)