Coupled Inductor Design

[sabu31]

Hi

I wanted to have some references for calculating L1, L2 in a coupled inductor used in coupled inductor boost converter. Do we calculate in the same method as that for a simple boost converter, ie. we calculate L1 using input current ripple.?


Thanks

 

[BradtheRad]

The formulas are different.

It has something to do with a 50 % duty cycle (or close to it) being desirable in a coupled inductor boost converter.
It is because it is a different inductance through which the flux field collapses, from the inductance through which it grew.
And at a different turns ratio.

Hence the transformer primary is calculated differently than for a simple boost converter.

 

[sabu31]

The formulas are different.

It has something to do with a 50 % duty cycle (or close to it) being desirable in a coupled inductor boost converter.
It is because it is a different inductance through which the flux field collapses, from the inductance through which it grew.
And at a different turns ratio.

Hence the transformer primary is calculated differently than for a simple boost converter.

Hi

Thanks for the reply. Could you give some references for the formula used to calculate required inductance in coupled inductor...

 

[BradtheRad]

A coupled inductor is used in the flyback, forward, push-pull, etc.

The link below is an article about switched coil power supplies. It specifically states the transformer in the boost converter does the jobs of both energy storage and step up/down. (Page 22 of 62 pages, see first paragraph.) The forward mode topologies use a transformer only for step up/down, and a separate coil for energy storage.

**broken link removed**

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Online calculator of transformer for flyback converter:



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Calculator of coil for plain boost converter:



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How to design a plain boost converter, including transformer formula:

http://www.simonbramble.co.uk/dc_dc_converter_design/boost_converter/boost_converter_design.htm

 

[sabu31]

Hi

Thanks for giving the links. I had used the second link earlier for inductor design of boost converter. However, the link does not have design for a coupled inductor . I am not sure if the same formula meant for flyback inductor design can be used for coupled inductor

Do u have references for formula used to decide the primary inductance in coupled inductor for use in Coupled inductor boost converter. I have got some reference for use in sepic converter https://www.ti.com/lit/an/slyt411/slyt411.pdf.

Thanks