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mag amplifier and zvs drivers

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cedric

Tue Feb 22 2011, 11:52AM

Registered Member #2941 Joined: Fri Jun 25 2010, 08:08AM
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Posts: 143

does any one know about such combination?
I looking for a way to control the output power of a zvs driver (with out using a switch mode power supply before it)
I am ready to try the system but it would be nice to know if it have been done before(probably)and what was the parameter...

radiotech

Wed Feb 23 2011, 04:12AM

Registered Member #2463 Joined: Wed Nov 11 2009, 03:49AM
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Posts: 1546

Please explain 'mag amp' Do you mean magnetic amplifier ?
If yes - what is the voltage and DC current range you wish to control?

cedric

Wed Feb 23 2011, 09:21AM

Registered Member #2941 Joined: Fri Jun 25 2010, 08:08AM
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the topologies would be the one from a magnetic amplifier but I would use it to control the current going to the LC tank,in a zvs the transistor are working in push pool so it feed the LC with alternative current (stop me if I am wrong) ,if some saturable inductor are on the way ,it's become possible to control the amount of current going to the tank by applying a small dc current to the saturable inductor,like an old fashion light regulator. if properly design this system should work great,the frequency is high so the inductors don't need to be big ,and it open the door for all sort of modulation or regulation...

cedric

Wed Feb 23 2011, 09:44AM

Registered Member #2941 Joined: Fri Jun 25 2010, 08:08AM
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actually I was planing to use this oscillator witch is a bit different than the other zvs http://4hv.org/e107_files/public/1251129162_89_FT1630_through_hole_wireless-schematic.pdf from marko.

radiotech

Fri Feb 25 2011, 07:56AM

Registered Member #2463 Joined: Wed Nov 11 2009, 03:49AM
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I think I understand now. Your are controlling the current from a power oscillator by connecting an impedance in series with both
output wires leading to the work coil, and adjusting the permeability of the impeder cores with a DC bias.

This sounds more like the operation of an 'increductor' than a magnetic amplifier.

Perhaps you could draw a diagram of the hookup.
'
Would the reactance not add another variable inductance to the power output matching network?

The isuue that comes to mind is distortion of the drive current by
the core operating at the top end of the B-H curve.

cedric

Fri Feb 25 2011, 09:53AM

Registered Member #2941 Joined: Fri Jun 25 2010, 08:08AM
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this is the idea:

with the rest of the oscillator represented by the the alternative current source ,and the tank (lc) circuit at the top..
I run some test already and it work a little but the inductor are getting really warm..

Marko

Fri Feb 25 2011, 01:25PM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

Hi,

Just to note, shouldn't your power coils of the mag-amp be connected in (anti)series, not parallel? Note that in parallel you'll still get both coils pass one half-wave.
There used to be small mag-amps in old tv's with power coils wound with few turns on outer legs of an E core (and connected in series) with the DC biasing coil in the middle.
I think that a parallel connection as you drew might work though, if you used diodes in series with each power coil.

Marko

cedric

Fri Feb 25 2011, 02:41PM

Registered Member #2941 Joined: Fri Jun 25 2010, 08:08AM
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Marko wrote ...

Hi,

Just to note, shouldn't your power coils of the mag-amp be connected in (anti)series, not parallel? Note that in parallel you'll still get both coils pass one half-wave.
There used to be small mag-amps in old tv's with power coils wound with few turns on outer legs of an E core (and connected in series) with the DC biasing coil in the middle.
I think that a parallel connection as you drew might work though, if you used diodes in series with each power coil.

Marko

to me it make more sens to put them in parallels and to let one of the inductor deal with one side of the sinus and the other take the other side because by saturating both ferrite you create a free-pass(that's why I connect both inductor in antiserie for the dc bias ),however most doc on the web do it differently but I could not make sens of it .what would be the purpose of the diodes?

Marko

Sat Feb 26 2011, 03:35PM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

Hi -

If you still haven't figured it out, this is what the second result on google returns... parallel connection without the diodes will apparently alsowork, just not as good.

I guess you can play with all of the circuits and see what works best for your needs.

Marko

cedric

Mon Feb 28 2011, 01:09PM

Registered Member #2941 Joined: Fri Jun 25 2010, 08:08AM
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Posts: 143

I think I am gonna explore some other possibilities,the system is working but my ferrite are getting very hot and like it is said in the document you link ,some ac start para-siting the dc control voltage ,witch does not mater if you use a good hold fashion potentiometer but fore me I need to control it electronically via a rc system ,
I guess the next fret should be: how to pwm a zvs...

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