各位大俠，本人看到一個比較復雜的電路，想和探討一個精確定電流輸出的LED反饋回路。輸出電流采樣電阻R10，通過鏡像電流源反饋，改變R18的阻值，即可以調節(jié)輸出Io大小。同時D11/12，R13是輸出的OVP反饋電路。
有沒有基礎知識抓實點的人物，理論計算和分析一下鏡像電流源，幫我推導出輸出電流與電阻的數學關系，謝謝！
只要有人看了這個帖子，就可以用于很多通用的電源IC中，那么就會有所收獲。當然電路你可以設計的更簡單化點。
高手探討——探討一個精確定電流輸出的LED電源反饋回路
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@超光速
差分放大，建議再復習一下模電。
沒有意義的回復不需要了?。∫貜途蛯懗鐾茖н^程，數據才是硬道理！！
否則，就省省筆墨吧。
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The board is equipped with a feedback loop to regulate the output current. This feedback loop senses the LED current over sense resistor R10, and a current mirror is made from transistors Q10a/Q10b. Using R18, the current level can then be set. The same feedback loop is also used to provide overvoltage protection. If the LED voltage exceeds 33 V, a current through R17 and D11, D12 and D13 will start running. The current through the opto coupler IC2 will pull up the REG pin. At values above 2.7 V, the ‘on time’ of the internal MOSFET is zero. The feedback loop has a proportional, and partially integrated action. The gain is critical due to the phase shift caused by the converter and the output capacitor C10. Increased gain will make the feedback loop intrinsically unstable.
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@zxd414
沒有意義的回復不需要了?。∫貜途蛯懗鐾茖н^程，數據才是硬道理??！否則，就省省筆墨吧。--------------------------------------------- Theboardisequippedwithafeedbacklooptoregulatetheoutputcurrent.ThisfeedbackloopsensestheLEDcurrentoversenseresistorR10,andacurrentmirrorismadefromtransistorsQ10a/Q10b.UsingR18,thecurrentlevelcanthenbeset.Thesamefeedbackloopisalsousedtoprovideovervoltageprotection.IftheLEDvoltageexceeds33V,acurrentthroughR17andD11,D12andD13willstartrunning.ThecurrentthroughtheoptocouplerIC2willpulluptheREGpin.Atvaluesabove2.7V,the‘ontime’oftheinternalMOSFETiszero.Thefeedbackloophasaproportional,andpartiallyintegratedaction.ThegainiscriticalduetothephaseshiftcausedbytheconverterandtheoutputcapacitorC10.Increasedgainwillmakethefeedbackloopintrinsicallyunstable.
推導過程已有解，如下附件所示，僅供參考。
@CM4FB_SMPS
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@zxd414
沒有意義的回復不需要了??！要回復就寫出推導過程，數據才是硬道理！！否則，就省省筆墨吧。--------------------------------------------- Theboardisequippedwithafeedbacklooptoregulatetheoutputcurrent.ThisfeedbackloopsensestheLEDcurrentoversenseresistorR10,andacurrentmirrorismadefromtransistorsQ10a/Q10b.UsingR18,thecurrentlevelcanthenbeset.Thesamefeedbackloopisalsousedtoprovideovervoltageprotection.IftheLEDvoltageexceeds33V,acurrentthroughR17andD11,D12andD13willstartrunning.ThecurrentthroughtheoptocouplerIC2willpulluptheREGpin.Atvaluesabove2.7V,the‘ontime’oftheinternalMOSFETiszero.Thefeedbackloophasaproportional,andpartiallyintegratedaction.ThegainiscriticalduetothephaseshiftcausedbytheconverterandtheoutputcapacitorC10.Increasedgainwillmakethefeedbackloopintrinsicallyunstable.
是呀!本來想要省筆墨,但是希望你不要瞧不起人,你提供的方案由市場來決定
我倒是可以說明我的看法,這是電流鏡的變化型,屬於線性控制範圍
對Switching RD而言,直接做初級迴授不須photo,不只懶得看,他們也沒買過配對晶體BCM875D
對Linear RD而言,安規(guī)的人不讓他碰Photo,沒折
對我而言,Switching的DC/DC專利一堆,直接做在IC內,不想花力氣打樣完還要依每批晶體特性調適電阻
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