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TOPSwitch SMPS circuit problem

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Taswar

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Hi,
I have about a few hundred pieces of TOPSwitch-GX devices, the TOP243, TOP245, TOP246, TOP248, TOP249 and TOP250. At first I made a few circuits using these and then tested them. They were okay and I left them lying there. Then, after a few months, I tried them again, and each and every single one of them had the same problem. They were all designed for 12-15v output. But, the output was fluctuating, going from 0v to 13v or 14v and then going back to 0. Each and every one of them.
Then I realized, my transformer winding was erroneous and I wound another transformer, and this time, strictly following everything in the PIExpert software, I made a new circuit. This worked fine, charging an SLA battery, running for about 8 to 10 hours. So, I thought that was the problem. So, I left it there.
Next when I tried the circuit again, the same problem showed. Why?
Since, I can't get readily wound cores here, I have to do the winding by myself, and I did that according to the software, using only one primary winding instead of as shown in the software.
But now, I want to know what could be causing these problems and how should I go about fixing them?
All my circuits are about 12-15v, 2-3A output max (these are all I designed upto now, I hope to go for more power later on).
I wound the transformer, all windings in same rotational direction.
Thanks in advance.
 

Hi,
Did you the designed inductances, its not a "air-gap" problem?
K.
 

Hi karez,
How can I know if it's an airgap problem? I bought the cores from the market, wound them and put a little piece of paper for the airgap. Is that okay?
 

Hi Taswar,
Its maybe exactly "the problem with air-gap" :)
You must know the paper thickness (or gap with) within so 10um-better less!
You must , as more easier-_ measure your inductances, all other is only thinking & dreaming-sorry...
Check pls. some calculation examples from PI applications(or with) the online/downloadable SW (your TOPSwitch is however from PI:)) for gap-problems-tolerances...
K.
 

    Taswar

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