求助：控制芯片在次級，電源怎么啟動？
想做一個雙管正激電路，想把PWM控制芯片放在次級。芯片供電次級的儲能電感加一個繞組。初級開關(guān)管用MOSFET，驅(qū)動用變壓器。想知道電源開機時怎么啟動的？
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這個搞笑了@ymyangyong
對呀！雙管正激如何實現(xiàn)自激啟動？這個真有點難！
這個是電路圖，我看不明白啟動電路。
原文就這么一點文字描述。Start-up circuit
As already mentioned in the introduction section, the controller is located on the secondary side of the power
transformer, and for this reason, a start-up circuit has to be provided for a correct system activation.
The start-up circuit is based on a diac sending a train of controlled pulses to the low side drive section; the floating
drive section is energised by the second secondary gate driv
e transformer winding .
As soon as the L5991a wakes-up, it generates a pwm signal enabling the start-up circuit.
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@grtang
這個是電路圖，我看不明白啟動電路。原文就這么一點文字描述。Start-upcircuitAsalreadymentionedintheintroductionsection,thecontrollerislocatedonthesecondarysideofthepowertransformer,andforthisreason,astart-upcircuithastobeprovidedforacorrectsystemactivation.Thestart-upcircuitisbasedonadiacsendingatrainofcontrolledpulsestothelowsidedrivesection;thefloatingdrivesectionisenergisedbythesecondsecondarygatedriv[圖片] etransformerwinding.AssoonastheL5991awakes-up,itgeneratesapwmsignalenablingthestart-upcircuit.
啟動電路
由于已經(jīng)在引言部分提到，位于電源的二次側(cè)控制器變壓器，因為這個原因，啟動電路必須提供正確的系統(tǒng)激活。
發(fā)送DIAC 低側(cè)驅(qū)動部分 列車的控制脈沖啟動電路是基于浮動
驅(qū)動部分由第二柵極驅(qū)動變壓器繞組通電。一旦作為L5991a喚醒的，它會產(chǎn)生一個PWM信號，使啟動電路。
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@grtang
這個是電路圖，我看不明白啟動電路。原文就這么一點文字描述。Start-upcircuitAsalreadymentionedintheintroductionsection,thecontrollerislocatedonthesecondarysideofthepowertransformer,andforthisreason,astart-upcircuithastobeprovidedforacorrectsystemactivation.Thestart-upcircuitisbasedonadiacsendingatrainofcontrolledpulsestothelowsidedrivesection;thefloatingdrivesectionisenergisedbythesecondsecondarygatedriv[圖片] etransformerwinding.AssoonastheL5991awakes-up,itgeneratesapwmsignalenablingthestart-upcircuit.
左下角那個三極管自激啟動電路?好像能工作,但不知道實際效果和對電路的影響會怎樣！
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@ymyangyong
驅(qū)動變壓器次級2個繞組是同相耦合的，下管有啟動脈沖時上管不是就有同相感應(yīng)驅(qū)動脈沖了嗎？
這樣分析對不對：開機后，當C25電壓充到32V時，DB3導通，電壓加到驅(qū)動繞組上，相互耦合，上管也感應(yīng)出電壓，此時上下管導通。此時傳遞能量到次級。延遲零點幾uS（R20C28的時間常數(shù)為2.5uS0后，C28充電試三極管T3導通，驅(qū)動線圈無電壓，上下管截止。如果一次啟動的能量不夠，延遲幾個mS（R16C25的時間常數(shù)36mS），DB3再次導通。
電路正常后，DB3是會周期導通。如果導通時間剛好是開關(guān)管截止時間，會短時間把開關(guān)管再次導通，對電路還是有點影響。
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