目前1000W以上大功率開關(guān)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(yùn)放基準(zhǔn)比較,輸出高電平或低電平,拉低PWM腳電壓或關(guān)斷PWM.此種短路電路能做短路時(shí)輸出電壓為零,且短路電流可做到設(shè)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(rèn)為應(yīng)用在半橋和全橋移項(xiàng)電路上相當(dāng)好,因?yàn)檩敵鲆话阌袀€(gè)教大穩(wěn)壓電感.
優(yōu)點(diǎn);可長(zhǎng)期短路,應(yīng)用在負(fù)載電流波動(dòng)較大場(chǎng)合,負(fù)載抗沖擊能力強(qiáng).
缺點(diǎn);對(duì)保護(hù)限流運(yùn)放動(dòng)作響應(yīng)時(shí)間要快,PCB線路設(shè)計(jì)合理,否則叫聲很難解決.
二、利用電流互感器在主變初級(jí)取樣,然后整流,加一級(jí)雙穩(wěn)態(tài)電路,短路時(shí)讓電源處于關(guān)又開這樣的一種脈沖方式工作.
優(yōu)點(diǎn);可長(zhǎng)期短路,靈敏度能做到比較高.
缺點(diǎn);靈敏度高要求很高,負(fù)載抗沖擊能力差.靈敏度高,容易誤保護(hù),靈敏對(duì)削差些短路很容易炸管.
以上兩鐘短路消除都可以自恢復(fù).
我現(xiàn)在做的LLC不對(duì)稱諧振電源,主要用在大系統(tǒng)上,而且大多是幾臺(tái)機(jī)器并聯(lián)運(yùn)行,要求負(fù)載抗沖擊能力要強(qiáng),因?yàn)榭紤]LLC諧振輸出沒(méi)有穩(wěn)壓電感,當(dāng)時(shí)就采用的是第二種短路方式,現(xiàn)在調(diào)起來(lái)感覺好痛苦,經(jīng)常有誤保護(hù).且現(xiàn)電源現(xiàn)已大量產(chǎn),要改方案可能性不大.請(qǐng)問(wèn)各位有其它好的短路方案嗎?
關(guān)于大功率LLC諧振電源短路保護(hù)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(shí)現(xiàn)恒流輸出呢?突然短路時(shí)LLC可能會(huì)跑到ZCS區(qū),而且短路時(shí)輸出電壓折算到變壓器原邊的電壓接近0,和正常工作時(shí)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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