Transformer cannot Sampled

Posted by: MikeOC on 08/09/2013

Hi I have a designed a 13.7V @37W SMPS using PI Expert and have had a PCB tracked for the design. I chose the design that used the EF25/13/7 core size.

I have sent the transformer and PI design of to ICE Components for them to quote on a prototype transformer. They have emailed me back saying:

We have used an EF25 bobbin to wind a test sample according to the PI drawing. But the fill factor is over 90% as you can see by the picture below. The core cannot be assembled to coil.

Is this a bug in the software?

I have attached the design and image from ICE Components

回應

Hi Mike.

The design didn't get attached. Can you please resend?

Thanks

Hi Wesley,

File attached for investigation.

Regards

Mike.

Hi Mike.

If you look at the design report the fit factor is indeed above 90% as per ICE indications. I see that we should have a warning or info under these circumstances, so I will be sure to add this for future versions. Thanks for pointing it out

I modified your design a little bit so that you will get a transformer that fits (please just make a final verification of the pinout). The modifications I made will change the value of the resistor next to the X-pin, but should allow you to keep the existing pcb you made.

Basically what I did is change the current limit of the device, which guarantees a lower peak flux density during a fault condition (like a short circuit).