Magamp AC source

I use this super-simple circuit (with an additional winding) to experiment with magamps and it seems to work correctly:

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But I found a weird circuit in this 1961 patent:

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What advandages does the second generator have? It contains coils connected to the emitters and collectors, with no obvious through-base feedback. I have never seen such an arrangement before -- what's that?

Best regards, Piotr

Reply to
Piotr Wyderski
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On a sunny day (Mon, 23 Nov 2015 10:40:05 +0100) it happened Piotr Wyderski wrote in :

It uses PNP, likely germanium in those days, and so should start at a lower voltage.

Reply to
Jan Panteltje

Right, but even the topology is unusual. Is it just a regular push-pull, or does it exploit non-linear effects too, as Royer does?

Best regards, Piotr

Reply to
Piotr Wyderski

On a sunny day (Mon, 23 Nov 2015 13:23:22 +0100) it happened Piotr Wyderski wrote in :

It is normal pushpull, with feedback in the emitters. Dunno about 'Royer'. But I think it will switch on saturation? So non-linear, probably. At some point the current in the coils is limited by base resistor Rb, so from that POV it is a current source, but not sure, it is easy to test if you have a ring core and 2 transistors and a meter or so wire? For the principle it does not make any difference NPN or PNP or Si or Ge.

5 minutes work on the lab supply?
Reply to
Jan Panteltje

On a sunny day (Mon, 23 Nov 2015 12:59:48 GMT) it happened Jan Panteltje wrote in :

PS, here is my saturatiiong multivibrator, I use the saturation peaks to drive some CMOS switches:

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It is part of this:

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Reply to
Jan Panteltje

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The scope will arrive on Wednesday, till then I'm blind. ;-)

Best regards, Piotr

Reply to
Piotr Wyderski

That is a Royer then. The idea of the Royer is the to use the saturable transformer to switch the transformer (so it will always run at max flux swing)

A better idea is the Royer-Jensen, which has a current sense transformer to act as the saturating element, so the main transformer is working below saturation and thus has potential lower losses

As far as I can see, both are Royers. The second one has added a constant current output

Regards

Klaus

Reply to
Klaus Kragelund

On a sunny day (Mon, 23 Nov 2015 15:00:15 +0100) it happened Piotr Wyderski wrote in :

In that article they use variants that make you think the author calls everything a 'Royer' Maybe he came from down under and believes in anthropogenic glowballworming (I see Baxandall mentioned).

Once you talk about a PWM drive it is a totally different beast IMO. For example the frequency is then set by the driver's oscillator, not by the core.

For this reason I have deliberate (?) amnesia if somebody wants to put a name of YAO oscillator, as _anything_ with a feedback gain of > 1 and the right phase will oscillate, so then there would be an infinite number of 'topologies', and there are.

We do not have that many words in all languages combined.

Yes a scope is a good thing to have. Best is an analog one, those do not lie.

CRTs may become extremely valuable collector items.

Reply to
Jan Panteltje

But why the emitter coupling? The classic base-coupled version would have spared them one winding, so I presume it is there for a reason.

Best regards, Piotr

Reply to
Piotr Wyderski

[standard blocking oscillator, two transistors, saturating xformer]

A disadvantage is that it'll be hard to start. The only advantage I see, is that the emitter windings operate at high current into a low-impedance emitter, rather than into a high-impedance base, so the turns count on those windings is low. It's easier to wind the transformer.

Reply to
whit3rd

Your circuit, which 'seems to work', relies on EB breakdown of one switch, in order for the other switch to conduct. It also has no base current limit. Drawn with a grounded feedback centertap, the avalanche can be avoided and feedback turns reduced. Add the resistor in the ground tap and the base current can be limited to account for a required overdrive to account for intended circuit loading.

The second circuit employs the high Veb ratings of germanium power transistors to shift a proportion of the load to the emitter winding. A typical 12 volt circuit might have 3x as many turns in the emitter winding, as in the collector winding.

Both circuits depend on main core saturation for determination of switching period. Feedback windings that supply only base currents are obviously easier to fool around with.

RL

Reply to
legg

Oh please don't say that NASTY word, it's going to invite, you know who!...

Jamie

Reply to
M Philbrook

why are some diodes solid black and others outlines?

Reply to
Cydrome Leader

I think it's like a differential pair, using inputs on the emitter rather than the base.

I have my doubts about it. RB is clearly wired up wrong unless those are SUPER leaky transistors.

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Reply to
Kevin McMurtrie

Not really, It has two centre-tapped widings same as Royer (variant with a single bias resistor), just in this patent one of the cenre-tapped coils is drawn as two coils. (typical patent obfuscation)

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Reply to
Jasen Betts

?? the transistors in a royer are common emitter, the base terminal is low impedance, the turns count for the bases only generates about 5V (any more risks avalanching B-E).

You do get fewer turns total wih this "Geyger" layput though, so less wasted space and no fragile fine wires needed the base.

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Reply to
Jasen Betts

It appears to be indicating current in each half cycle. check the text if it's important.

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Reply to
Jasen Betts

Oh, I thought the Subject: was Megaamp AC source. Now that would have been interesting.

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    - Win
Reply to
Winfield Hill

On a sunny day (25 Nov 2015 04:53:11 -0800) it happened Winfield Hill wrote in :

10,000 turns @ 100 A primary, metal bar (1 turn) secundary. Will need a truck. Reminds me of my first job.
Reply to
Jan Panteltje

Might have been interesting if it concerned the actual thread title as well, but should probably have been 'AC source for magamp'......or 'self-oscillating inverter'.

Do ignorance and interest have inverse relationships?

RL

Reply to
legg

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