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Power Supply Current limit

blocka

Jul 7, 2010
18
Joined
Jul 7, 2010
Messages
18
Hi, I am working on a power supply based on the LM3478 chip in a SEPIC configuration that is used to charge 12V SLA batteries.

I have tried to implement a current limit as shown in picture but am having problems.
It all works well if i let the LM3478 current limit but the problem with this is the limit is proportional to Vin.

What seems to be happening is that my current limit kicks in and causes the LM3478 to shutdown after 3 cycles due to overvoltage on the FB pin, and then starts up and continues this cycle.

Can anyone suggest a way of making this work or a better current limiting scheme?

Thanks.

Will have to post cct after post 1 apparantly
 

blocka

Jul 7, 2010
18
Joined
Jul 7, 2010
Messages
18
98634193.jpg
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