Ideas for winding power supply transformers?

[zebra50]

Hi!

I'm fishing for ideas and experience here.

I want to make some small power transformers for stepping up from about 9-12 V to about 150V. This would be for a tube mic B+ supply like the Gyraf G9, where the mains supply has already been stepped down to provide a suitable voltage for the tube heater. I'm looking for just a few milliamps for the B+.

I have some small toroidal power cores to play with, and I know the basic transformer rules, but what else do I need to factor into my design? Is it as simple as winding 12 turns of thick wire onto one side of the toroid and 150 of thinner onto the other? or double/x10 those figures? Should the windings overlap? Anything else to look out for?

I could just buy what I want, but this is DIY! :grin:

Many thanks

Stewart

 

[gyraf]

[quote author="zebra50"]
Is it as simple as winding 12 turns of thick wire onto one side of the toroid and 150 of thinner onto the other? [/quote]

No.

You will need to ensure a primary inductance that is large enough that the input impedance is dominated by inductance, not by winding resistance - at the frequency in question.

For very high frequencies, the 12turns to 150turns will probably work (depending on core Al value) but at 50 (60) Hz, you will need to ensure high enough inductance..

The easiest and cheapest way to do this would probably be to use a standard 110:8V power transformer..

Jakob E.

 

[mcs]

I can help you with standard EI transformers, but not toroids.

Best regards,

Mikkel C. Simonsen

 

[zebra50]

Thanks for the ideas

[quote author="gyraf"]
For very high frequencies, the 12turns to 150turns will probably work (depending on core Al value) but at 50 (60) Hz, you will need to ensure high enough inductance..
[/quote]

Good point - it begins to look like a lot of winding work.

[quote author="gyraf"]
The easiest and cheapest way to do this would probably be to use a standard 110:8V power transformer..
[/quote]

True, and this is what I have done in the past - but I thought if it was easy.....