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SMPS for vacuum tube power amplifiers.(status: back at it)

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SK_Caterpilar_SK:
It definitely is a EMC hell, so far aiming for anything functionall.

I do have a solution for opto isolating the output with clasic method (TL431 and PC817). I can send you the schematic for that. It loads the supply at 500V with about 2W. It gives a little load for stability. I simply shunt regulated the opto diodes voltage so I dont kill the TL431. The primary side of the thing is simply text book grade stuff, sufficient enough.

Switching transformers provided by coilcraft are decent enough. I use the GA3459 for 12-24V to 500V conversion. Also the GA3460 does the same but the winding DCR is much lower and other things..

I planned using the HA4060 to try with line voltage but currently I just have the transformer and dont plan on doing such a dangerous project.
So far Im searching a suitable controller for the job. Not having bias windings in transformers is a pain, but solvable. If it would work out with temporary solutions I would go ahead and quote coilcraft for custom transformers but so far there is no point in doing that. Unless I find a viable solution for the first problem.

mrjoda:

A feedback of smps is never so easy as it looks. You have to think in frequency domain, not in time.

check this article :

https://www.onsemi.com/pub/Collateral/TND381-D.PDF

it gives you a long no sleep nights and headache.

TL431 is the most straightforward solution, but not the best.

I based my ideas on Viper 53 from ST. I was not able to find any reasons why is not suitable for this task,  but maybe someone with better experiences could find one. 

SK_Caterpilar_SK:
The 431 is the simplest all around solution and I like the Viper 53 unfortunately for me still trying to make a 12-24V input power supply and the switching transformers I have don't have aux windings. And in general I find PSR way more confusing than voltage feedback from the secondary side.
I would like to consider that option tho, I just don't have the literature to clarify some things

scatterandfocus:
I saw this thread some days ago, but I don't login to any sites from work machines and network, so I didn't reply.

It's an interesting project.  At least one manufacturer did produce some tube amps using switching supplies - Crate V series amps.  They didn't go over well in the long run because of audio quality (noise) and generally poor construction.  Keep in mind that these amps were not aimed at the vintage amp crowd.  They were low priced tube amps, where the crowd isn't so picky as long as things work as they should and sound ok.  I haven't seen any other tube amps that use a switching supply, but I haven't gone looking either.  If done well enough that I couldn't hear a difference between it and a linear supply AND the thing is well constructed AND it doesn't introduce noise into other devices, I would prefer the more efficient supply.

Oh,and I forgot about some of the scary failures of those Crate V series amps.  Just went on a little reading spree about those amps, as I haven't heard anything about them in a long time now.  Apparently Crate went out of business a couple of years after the release of the V series amps.

T3sl4co1l:
Dave Berning created a series of tube amps with DC transformers -- MOSFET choppers plus transformer coupling.  IIRC, they ran around 200kHz, and the primary side used as many windings in series to supply the voltage required for the tube, allowing otherwise fairly difficult-to-use types like transmitter tubes (e.g. 1kV 100mA, a high load impedance) to be used down to DC.

Tim

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