Low THD transformer circuit

Why not load the transformer secondary into a summing point and drive the primary through a resistor, or from a current source? That would keep the core at nearly zero flux.

John

Yep. I've used that trick to get low frequencies thru tiny transformers.

...Jim Thompson

--
|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
|  Phoenix, Arizona            Voice:(480)460-2350  |             |
|  E-mail Address at Website     Fax:(480)460-2142  |  Brass Rat  |
|       http://www.analog-innovations.com           |    1962     |
             
I love to cook with wine.      Sometimes I even put it in the food.

This is actually a bit stupid - the resistance of the transformer depends on the winding temperature.

Better is to drive the primary through a low resistance winding, and monitor the voltage generated in second winding, which can be wound with fine wire, since it doesn't have to carry much current, and use feedback to make sure that monitored voltage follows desired input.

Formed the basis for a very cheap and very accurate gadget for transferring DC voltages across an isolation barrier that I did for George Kent back in 1975. I've used it in other contexts since then.

Audio Precision hasn't even re-invented the wheel, but some kind of constant diameter roller.

--
Bill Sloman, Nijmegen

I think that works for input transformers, not output transformers

martin

Well, follow it with a floating-supply amp, just like the input case.

This has 16 floating output channels, each with its own dc/dc converter. I figure that there are about 86 different supply rails on this board.

We're using ISDN data transformers as the dc/dc things, about $1.10 each.

John

Ok you win.........:-)

martin

** Yawn ....... pukeeeeeee

yet another typically ASININE Slow Man Fuckwit knee jerk reaction.

The FOOL obviously did NOT even READ the supplied patent !!!!

The 0.4% per C tempco of resistance of copper wire in a transformer is likely not significant in the context of an item of audio test equipment intended to be used in an air conditioned lab. In any case, the effect of such a small tempco can be eliminated by using a thermistor in the negative impedance amplifier ccts.

See the final paras on page 4 of the supplied patent PDF

- that is EXACTLY what it says !!!

....... Phil

Or use a second tranformer to sample the output of the main one, and supply feedback. That one could work in zero-flux mode.

John

Hmm, +/-15 and +5, etc., for each of the 16 channels, that's 48 supply rails, plus some on the VME side, how do you get 86 rails?

--
 Thanks,
    - Win

5 rails in each channel. +-18 unreg, +5, +-2.5. The 2.5 rails are for the chopamps. You can hardly find a chopper amp that tolerates more than 5 volts r-r any more. So we wind up doing ppm-accuracy stuff with +-2 volt swings.

John

Phil doesn't seem to have heard of self-heating.

This would be aslightly better idea if the thermistor were embedded in the winding involved.

So what. Getting the winding resistance out of the loop is still a better solution.

--
Bill Sloman, Nijmegen

** The Slow Man Fuckwit has no sane case to present - as usual.

So the autistic cretin posts even more irrelevant shit.

** The Slow Man Fuckwit has no sane case to present - as usual.

So the autistic cretin posts even more irrelevant shit.

** The Slow Man Fuckwit has no sane case to present - as usual.

So the autistic cretin posts even more irrelevant shit.

** No case to answer here.

The Slow Man Fuckwit is guilty as charged.

....... Phil

Impressive. Not a single piece of new information in the entire post.

--
Bill Sloman, Nijmegen

** The Slow Man Fuckwit has no sane case to present - as bloody usual.

So the worthless, unemployable, autistic cretin posts even MORE irrelevant shit.

The Slow Man Fuckwit is GUILTY as charged, yet again.

........ Phil

Hi Phil - I'm in Sydney. Should I look up your address - it has been posted - and come visiting with a couple of my nephews, or would you prefer to suggesst neutral ground where we could drink some coffee together?

--
Bill Sloman, Nijmegen (but in Centennial Park at the moment)

Hi Phil - I'm in Sydney.

** Really ??

If true - that is just so appalling.

........ Phil

isnt it Unit 6, 19 Prospect Rd Summer Hill

Cheers Terry

That would be some 10km due west from Centenial Park, and a couple of social classes lower - my wife and I are house-sitting for a couple we've known since we were all undergraduates together at Melbourne in the 1960's.

--
Bill Sloman, Nijmegen (but in Sydney at the moment)

Don't play that game, Bill. It can end in tears:

Paul Burke