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Fly back converter Design using UC3843

Balaji1998

Apr 18, 2023
3
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Apr 18, 2023
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I am designing a offline power supply which will 24V as output with 2.5A. I found UC3843 as better option. I used TI we bench tool to design my power supply. This is the schematic I got from it. The given transformer design, I given to one manufacturer and I got a transformer. I rigged up the circuit as it mentioned. But in this I am getting three Issues
1) Audible noise across the transformer.
2) Sometimes(randomly) restarts while I am connecting 1A load.
3) Small ripples present in output when there is no load.
how to solve these problems
 

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Delta Prime

Jul 29, 2020
2,042
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Jul 29, 2020
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Perhaps your architecture is of concern I usually use the laminate of the transformer as a chassis ground.
I make sure there is no galvanic connection between the power return and the internal signal ground or in your case "grounds" yeah chassis analog & digital grounds.
The enclosures chassis need to be connected to the internal grounds to eliminate parasitic feedbacks through capacitive coupling; but then they would create ground loops. Good circuit architectures require signals working with their own ground, isolated from the chassis, to prevent ground loops.
Only currents from lightning or other interference suppressed by the EMC ,EMI circuit blocks is allowed to be returned to the chassis.
 
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