目前1000W以上大功率开关电源,短路电路方式通常采用有以下两种:
一、利用电流取样放大器,电流越大放大器输出电压就越高,然后与限流运放基准比较,输出高电平或低电平,拉低PWM脚电压或关断PWM.此种短路电路能做短路时输出电压为零,且短路电流可做到设定安全最大电流值,也就是一种(短路电流回缩原理).此种电路方式我认为应用在半桥和全桥移项电路上相当好,因为输出一般有个教大稳压电感.
优点;可长期短路,应用在负载电流波动较大场合,负载抗冲击能力强.
缺点;对保护限流运放动作响应时间要快,PCB线路设计合理,否则叫声很难解决.
二、利用电流互感器在主变初级取样,然后整流,加一级双稳态电路,短路时让电源处于关又开这样的一种脉冲方式工作.
优点;可长期短路,灵敏度能做到比较高.
缺点;灵敏度高要求很高,负载抗冲击能力差.灵敏度高,容易误保护,灵敏对削差些短路很容易炸管.
以上两钟短路消除都可以自恢复.
我现在做的LLC不对称谐振电源,主要用在大系统上,而且大多是几台机器并联运行,要求负载抗冲击能力要强,因为考虑LLC谐振输出没有稳压电感,当时就采用的是第二种短路方式,现在调起来感觉好痛苦,经常有误保护.且现电源现已大量产,要改方案可能性不大.请问各位有其它好的短路方案吗?
关于大功率LLC谐振电源短路保护电路探讨!
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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.
但是如何实现恒流输出呢?突然短路时LLC可能会跑到ZCS区,而且短路时输出电压折算到变压器原边的电压接近0,和正常工作时有很大的不同
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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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