I have recently bought a book to learn about SMPS design and have learned some of the basics and fundamentals about SMPS design. However, when reading this book, and looking at some of the design procedure and schematics, they always refer to designing custom transformers for the PWM output. As in one big primary winding and multiple smaller secondary winding for multiple voltage outputs. It seems as if I wanted to build these circuits, all of the parts are readily available from digikey except these custom transformers that have one primary winding and multiple secondary winding and are designed to operate at the PWM frequencies of 40-60khz.

My question is if there any kind of readily available type of transformer I can use for SMPS instead of the custom wound transformers referred to in my book? Also, instead of one big primary winding and mulitple secondary windings for multiple voltage outputs, is it possible to use multiple transformers in parallel with the PWM output feeding all the transformers?

Thanks.

 

Check out:

http://www.pulseeng.com

For some off the shelf choices suitable for small switch-mode designs.

There are other companies as well.

 

It seems that they don't sell directly from their site, and list digikey as one of their distrubuters but it seems as if digikey doesnt sell their high frequency transformers.

Do you have any websites that sell their stuff, or any other companies smps transformers?

 

Try J.W. Miller

 

I just checked out their website and it seems as if the only transformers they have are 50/60hz transformers, am I missing something?

 

Can you use the 3000 series signal transformers, or the 6700 series toroids?

 

I dont think so, I need a transformer like the ones pulse sells for the step down capability.

 

anymore help?

 

Let me check the parts list on the SEPIC converter. I'll get back to you.

 

Hmm looks like these guys might have some that you can buy.

http://www.wcmagnetics.com/catalog/p...ansformer.html

Also, did you look at Mouser?

I'd like to add another thought that might help you. It is much easier to get the actual core material than it is to get an assembled transformer.

You could design you own. If you need them mass produced, then you can have a company like Hi-rel or similar design it for you. If you need just a couple of them for your own purposes, consider winding you own.

 

We used the folowing part in a SEPIC converter.

Coiltronics CTX33-3A

 

Is there any reason why you don't want to wind your own?

It isn't that difficult, I haven't wound a smps transformer before but I've wound plenty of flyback transfomers for high voltage projects like flourescent tube drivers and light bulb plasma balls, I strongly recommend it, it's cheaper and easy to get the specification you require.

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Designing a transformer is not easy, the parameters are complex. You need to select a core that has low loss and high permability at the frequency of operation, and enough cross-sectional area to support the power. Data is available at www.mag-inc.com. I use ferrite cores, but others may be suitable.

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My book actually walks my thru how to design the transformers and want kind of cores would be appropriate and what-not. I was just looking for a possible off the shelf solutions instead of winding my own.

Looks like I will have to be winding my own.