Inductor gap design
I'm about to test the circuit of the DER-285, that uses the LNK409. My question is about the inductor gap. The software says to build an inductor with 90 turns and a 0.5mm gapped core. I have a 0.85mm gapped core. To adjust the number of turns, can I just use the relation N= sqrt(L/AL)? Thanks.
Comments
I'll modify the DER-285 for my specific application at a later moment. By now, I want to test the application shown on DER-285. I bought all the circuit parts, but the ferrite core I got is a bit different. It is a PQ type aswell, but a little bigger and already has a 0.85 air gap. I put its specs on PIXIs spreadsheet, and the result was 90 turns with a 0.69mm air gap. Since my core already has a gap, if I use 90 turns the inductance will be lower. So can I modify the number of turns using N=sqrt(L/AL) to adjust the inductance value without any problems?
Thanks.
You could try doing that but you'll need to make sure to change your secondary turns as well to keep the same turns ratio as originally indicated in the software. You could also fiddle with some of the different parameters in PI Expert and see if you can get it to calculate a similar transformer design with a 0.85mm gap.
-The Traveler
Secondary is not a problem. DER-285 is a boost circuit, and has a single inductor. I have already tried it anyway, increasing a little the number of turns to achieve the required inductance.
It's my first design using Power Integrations's ICs. The result was pretty good - nothing blowed up yet... However there was a higher current ripple than expected, but I think a little more practice with the spreadsheets gonna help.
Well, about my initial question, I think since the core has the required size, there's no problem on increasing the gap lenght. We just have adjust the number of turns to achieve the proper inductance.
Thanks for the advice.
I'm confused about what you're asking. Are you using DER-285 as a starting point and then modifying it for your specific application?
-The Traveler