目前1000W以上大功率開關電源,短路電路方式通常采用有以下兩種:
一、利用電流取樣放大器,電流越大放大器輸出電壓就越高,然后與限流運放基準比較,輸出高電平或低電平,拉低PWM腳電壓或關斷PWM.此種短路電路能做短路時輸出電壓為零,且短路電流可做到設定安全最大電流值,也就是一種(短路電流回縮原理).此種電路方式我認為應用在半橋和全橋移項電路上相當好,因為輸出一般有個教大穩壓電感.
優點;可長期短路,應用在負載電流波動較大場合,負載抗沖擊能力強.
缺點;對保護限流運放動作響應時間要快,PCB線路設計合理,否則叫聲很難解決.
二、利用電流互感器在主變初級取樣,然后整流,加一級雙穩態電路,短路時讓電源處于關又開這樣的一種脈沖方式工作.
優點;可長期短路,靈敏度能做到比較高.
缺點;靈敏度高要求很高,負載抗沖擊能力差.靈敏度高,容易誤保護,靈敏對削差些短路很容易炸管.
以上兩鐘短路消除都可以自恢復.
我現在做的LLC不對稱諧振電源,主要用在大系統上,而且大多是幾臺機器并聯運行,要求負載抗沖擊能力要強,因為考慮LLC諧振輸出沒有穩壓電感,當時就采用的是第二種短路方式,現在調起來感覺好痛苦,經常有誤保護.且現電源現已大量產,要改方案可能性不大.請問各位有其它好的短路方案嗎?
關于大功率LLC諧振電源短路保護電路探討!
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In my experince in short circuit of LLC,it is really a headache. Finally, we used two modes of current protection. There is a delayed OCP and also a Constant current mode. The delay time can be set from 1s to 6s, default is 3s, during this 3s delay, the constant current mode will take place,limiting the output current, if the overload current is not removed after 3s, the unit will ented hiccup mode. Try to add a delay to your OCP circuit.
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@bud_guy
InmyexperinceinshortcircuitofLLC,itisreallyaheadache. Finally,weusedtwomodesofcurrentprotection. ThereisadelayedOCPandalsoaConstantcurrentmode. Thedelaytimecanbesetfrom1sto6s,defaultis3s,duringthis3sdelay,theconstantcurrentmodewilltakeplace,limitingtheoutputcurrent,iftheoverloadcurrentisnotremovedafter3s,theunitwillentedhiccupmode. TrytoaddadelaytoyourOCPcircuit.
但是如何實現恒流輸出呢?突然短路時LLC可能會跑到ZCS區,而且短路時輸出電壓折算到變壓器原邊的電壓接近0,和正常工作時有很大的不同
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@bud_guy
InmyexperinceinshortcircuitofLLC,itisreallyaheadache. Finally,weusedtwomodesofcurrentprotection. ThereisadelayedOCPandalsoaConstantcurrentmode. Thedelaytimecanbesetfrom1sto6s,defaultis3s,duringthis3sdelay,theconstantcurrentmodewilltakeplace,limitingtheoutputcurrent,iftheoverloadcurrentisnotremovedafter3s,theunitwillentedhiccupmode. TrytoaddadelaytoyourOCPcircuit.
A realy good idea, but how to realise the hiccup mode? espacial when the output short circuit happened, also after a 3s delay then enter the hiccup mode? could you pls share us what's the IC do you choose?
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