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Dotted convetion of couple innductor matter for SEPIC config

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Winsu

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Hi All,

I am designing a SEPIC using a LM3488 and I am planning to use coupled inductors instead of two discreates inductor. My problem is that the couple inductosr that I find are not in phase, in other words, the dots on both inductor are not at the same end of each coil. I am not sure if the coupled inductors needs to be in phase or not to configurate properly a SEPIC. The datasheet stated this about the inductors. Anyone can let me know please?

1592585465275.png
 

SEPIC sim attached for you in the free LTspice simulator which you can download.
This shows a coupled sepic with its “sister” flyback…….look at the diode and fet currents..they are the same in each case.

So the coupled sepic and flyback are in fact almost identical twins, just run the sim and see......the fet and diode currents exactly the same !


The coupled sepic is like a flyback but with the coupling cap connected as you see in the sim.

So do your transformer like a flyback...
 

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  • SEPIC _coupled inductors.txt
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treez said:
SEPIC sim attached for you in the free LTspice simulator which you can download.
This shows a coupled sepic with its “sister” flyback…….look at the diode and fet currents..they are the same in each case.

So the coupled sepic and flyback are in fact almost identical twins, just run the sim and see......the fet and diode currents exactly the same !


The coupled sepic is like a flyback but with the coupling cap connected as you see in the sim.

So do your transformer like a flyback...
Click to expand...

Thanks Tree, I have LTSPICE , the file you sent is a .txt, I would expect a .asc

Regards,
Winsu

5 minutues later I just changed the extension and it worked,thanks
 
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Yes, you will see that coupled SEPIC and Flyback are indeed sisters
 

for a coupled choke, if the dot is on the Vin side - the corresponding dot needs to go to gnd on the other wdg ...

( if non-dot is on the Vin side, then non-dot goes to gnd on the other )
 

    d123

    d123

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