Toroid Transformers for DC to DC power supply
paysonbadboy
Posts: 81
just wondered if anyone here has had experience making toroid transofrmers for DC to DC power supplies form scratch.
I'm messing around making a mini-ATX 12VDC power supply for the computer's 12VDC, 5VDC, 3.3VDC, and -12VDC.
Thought I'd compare ideas. I can always learn from making mistakes and I know I can search the net. But thought I'd grab some ideas from some great hobbyiest in here
Ok. Today·I was playing a bit. Finally. Work has kept me TOO busy lately.
Anybody make pathetic messes like this?
On the right is a home brew PWM made from a 555 and a comparitor.
On that white test board is a IRFZ44 mosfet on a little heat sink.
That is driving the test toroids·I wound and is charging that small cap and running that large DC fan there. (It's moving, just not in the picture )
I set the feedback to the PWM to regulate near 12VDC.
I played with a few different toroids I wound. I used to mess with them in car amplifiers. Most of them stepped up the voltage by quite a bit and were push pull.
While this green one I made semmed efficient. it actually ran a little HOT. The mosfet ran near room temp with that heat sink.
I let that sucker run a good 30 minutes or so.
It seemed to regulate fairly well with the home brew PWM. I'd load down the fan by slowing it down with my hand! Only problem with the test was at one point the wall wart I was using to provide the 12VDC to this circuit would bog down to around 7 VDC when I really loaded down the fan and the PWM really drove the mosfet.
In the end, the thing will be ran from a car battery. No shortage of power there.
I·don't have a good 12VDC power supply in my house right now
Anyway. Anyone have any tips on winding toroid transformers?
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http://www.paysonarizona.net/
I'm messing around making a mini-ATX 12VDC power supply for the computer's 12VDC, 5VDC, 3.3VDC, and -12VDC.
Thought I'd compare ideas. I can always learn from making mistakes and I know I can search the net. But thought I'd grab some ideas from some great hobbyiest in here
Ok. Today·I was playing a bit. Finally. Work has kept me TOO busy lately.
Anybody make pathetic messes like this?
On the right is a home brew PWM made from a 555 and a comparitor.
On that white test board is a IRFZ44 mosfet on a little heat sink.
That is driving the test toroids·I wound and is charging that small cap and running that large DC fan there. (It's moving, just not in the picture
)I set the feedback to the PWM to regulate near 12VDC.
I played with a few different toroids I wound. I used to mess with them in car amplifiers. Most of them stepped up the voltage by quite a bit and were push pull.
While this green one I made semmed efficient. it actually ran a little HOT. The mosfet ran near room temp with that heat sink.
I let that sucker run a good 30 minutes or so.
It seemed to regulate fairly well with the home brew PWM. I'd load down the fan by slowing it down with my hand! Only problem with the test was at one point the wall wart I was using to provide the 12VDC to this circuit would bog down to around 7 VDC when I really loaded down the fan and the PWM really drove the mosfet.
In the end, the thing will be ran from a car battery. No shortage of power there.
I·don't have a good 12VDC power supply in my house right now
Anyway. Anyone have any tips on winding toroid transformers?
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
http://www.paysonarizona.net/
Comments
One tip I'm aware of for improving efficiency, albeit it only applies at fairly high frequencies probably beyond 100Khz, and that is to use Litz wire to reduce the skin effect.
Also, since we can't tell from your pictures, but it is important to have some capacitance at the supply side of the inductor, and to keep all high speed current lengths as short as possible. Its amazing the amount of ringing that can be introduced by even short lenghths of connecting wire.
Looks to me like you're well on your way though.
Peter (pjv)
I'm in the middle of a very sticky problem with a universal input, 5V 0.1A output offline power supply, so I can sympathize. It just won't stay stable, despite ST's claims about the infallible nature of their controller chip. Grr.
Good luck!
-dave
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This is not a sig. This is a duck. Quack.
Why the cap on the PRIMARY side?
I bought several PWM IC's a while back. Messed up and selected some for SURFACE mounting. OOPS. Too small to play with so they are sitting here.
My regulation actually stayed with in 1 volt. Surprisingly with just a small like 22MF cap on the secondary side and nothing in the primary side.·I'd probably be even closer if·I had used a bigger 12VDC power supply on the project rather than the wall wart that dropped to 8 VDC or so when·I loaded down my fan [noparse]:([/noparse]
I'm running it at a slow 10KHZ (which believe it or not I've seen car amps run fairly slow like that).
The regulation is made simple. You set up a 555. take the SAWTOOTH wave form off of the cap that is charging/discharging.
Feed that into the + side of a comparitor.
Set your voltage reference on the -
Basically the comparitor has NO output until the sawtooth wave reaches your reference. Then the pulse goes back to low once it drops below the reference.
It's amazing how good that actually works. It's something·I stumbled apon on the net somewhere.
I'm planning on using one 555 and one quad comparitor IC to output up to 4 Mosfet Driven transformers.
I guess·I COULD try UPPING the frequency and play around with that too.·I wouldn't want ANY noise being generated in that frequency range so close to all my audio amplifiers!
I pulled those toroids off of a DC to DC ATX power supply·I bought. It was too small I think.
Funny hing was it had only ONE winding on each toroid. So it must have been using the same winding as the primary and secondary, if you can say that, and just using current steering diodes.
Been a while since I actually saw that way being used as a DC to DC power supply.
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http://www.paysonarizona.net/