> Are you designing amp for Discopete?
No.
I know quite a bit about Jan's project.
It has been on his drawing board (and test bench) for quite a few years already.
But I promised not to disclose any details.
So I better leave him to satisfy your curiosity.
And he did consider tubes before.
Cheers,
Patrick
No.
I know quite a bit about Jan's project.
It has been on his drawing board (and test bench) for quite a few years already.
But I promised not to disclose any details.
So I better leave him to satisfy your curiosity.
And he did consider tubes before.
Cheers,
Patrick
" Just " ..........
well, a few 'small' details might be needed
But its a workable concept. More reliable than stressing one part to its limits.http://cmosedu.com/jbaker/papers/1993/RSI641993.pdf
Lots of help published on stacking (series) .... even push-pull stacked ...
THx-RNMarsh
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Kean, how do I 'bind' that symbol drawing to the model? Just learning LTspice and I'm not at that chapter yet. ;-)
Jan
Ah, that's cool, I have to admit I never really did pay too much attention to ESL and exotics in the past, that was until after reading one of the more recent threads under SS it got me a bit itchy too.
There really aren't many parts out there for the job of 4kV direct drive, IXTL2N450 could be interesting though, comes already isolated with a ceramic tab (IXYS DCB) incorporated into the package, but at a delicate cost.
Looking at the SOA limiting curves it suggests these parts can't take HV for prolonged time even at minuscule currents so a HP filter is needed.
Digikey.com IXTL2N450
And little brother..
Digikey.com IXTF1N450
There is an even smaller family, 02N450. Look at the Coss on these babies combined with the published SOA and the 4000V swing @ 20kHz and you get a feel for the tight spot I am in.
I did talk to IXYZ support about the 'hidden' part of the SOA graph, and basically the answer was: 'we don't know, we never use it there, and good luck to you'....
The problem is analogous to BJT 2nd breakdown. But it's not that local heating starts that spot to hog current, but in a MOSFET it is that local heating lowers the Vgs threshold in that spot, leading to current being concentrated there. Result is the same - release of copious amounts of black smoke.
But I will go forward, start the next PCB generation layout today. I will keep the option of a CPU cooler in, these things appear really nice, not expensive and some are really quiet.
No guts, no glory.
Jan
Remove the .txt from the .asy file, that prevents LTSpice from recognizing it (the forum won't let me upload anything with .asy). After that all you need is the .asy file to be in the same folder as the schematic file.
Face it Jan at least one of your builds on this will really let some spectacular smoke out. Make sure the 2KV supplies have a very low output impedance and lots of energy storage. We had an ADSL customer in China that called and said our parts were "holeing" we thought it was a mistranslation. It turned out one of their tests was shorting to the rail on the near side of the transformer, and the die was vaporizing and blowing a hole in the SMT power package.
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New Amp Testing Methodology
I hope I am not double posting, but as we all know, no existing tests quantify amplifier sound quality (ducks).
Here is a Master's thesis proposing an alternate method:
https://goo.gl/M6FpVu
...and he makes some interesting points, although I disagree with his conclusions in general. Of course being that the listening tests were conducted using a pair of 1960's Radio Shack 16 ohm PA monitors, skepticism is perhaps called for.
I just figured after all of that turkey you US audio dudes ate, some rousing theological conflict could stir you out of your torpor!
Happy Thanksgiving!
Howie
I hope I am not double posting, but as we all know, no existing tests quantify amplifier sound quality (ducks).
Here is a Master's thesis proposing an alternate method:
https://goo.gl/M6FpVu
...and he makes some interesting points, although I disagree with his conclusions in general. Of course being that the listening tests were conducted using a pair of 1960's Radio Shack 16 ohm PA monitors, skepticism is perhaps called for.
I just figured after all of that turkey you US audio dudes ate, some rousing theological conflict could stir you out of your torpor!
Happy Thanksgiving!
Howie
Mosfets can do strange stuff. I managed to blow holes through the tops of some TO-3's. They looked like they'd been hit with a laser or somesuch.
The manufacturer's engineer blamed it on ' plasma '
Nelson thanks for that, indeed this seems like they are aware and trying to solve. My communication was with support in Germany and this was never mentioned.
Jan
The 2.1kV supplies are regulated and current limited. So far no device has been lost, but I know it probably will happen one of these days. No reason to stop trying to finish it, of course.
I am planning to switch to 4.5kV IGBTs for the output stage, as these have more robust SOAs.
But for the Vas they have too much interelectrode capacitances. I can handle that in the output stage as a (sizeable) fraction of the load, but not in the Vas.
Then again, I really wonder if a class A quiescent of just 6mA would ever trigger this behaviour, even at +/-2kV - but eventually I'll have to prove the pudding. Haven't run it over +/-1kV so far.
Jan
This may be of interest Jan.
http://www.magazines007.com/pdf/High-Voltage-PCDesign.pdf
If you are having PCB's made I would recommend a high voltage laminate once you get over 2K. AT home so haven't got access to my work notes, but from memory there can be issues with normal PCB laminate. One problem is micro bubbles within the material that can cause micro arcs. I'll dig the stuff out it was interesting. It was for Ion containment electrodes so high voltage but low current, but reasonable switching speeds, . Nightmare for spacing so multi-layer PCBs are best with ALL high voltage tracks on inner layers, then you only have to worry about pads and component legs for external spacing's. Multi layer boards also give you the ability to add screening layers if required.
For your thermal stuff have you thought of looking at Avvid or similar, had some fun with thermal pipes and thermal ribbon pipes, allowing a good thermal pathway from hard to reach areas or devices to a thermal radiator.
On these designs when it goes wrong it can be spectacular, I once had some diodes put in the wrong way on a PCB, in a prototype high voltage (35kV, 10-15KV 2X2.5kV and 6x1kV) all shorted together for one illuminating instance, for some reason I did not get the employer of the month award but a verbal a*** kicking.
http://www.magazines007.com/pdf/High-Voltage-PCDesign.pdf
If you are having PCB's made I would recommend a high voltage laminate once you get over 2K. AT home so haven't got access to my work notes, but from memory there can be issues with normal PCB laminate. One problem is micro bubbles within the material that can cause micro arcs. I'll dig the stuff out it was interesting. It was for Ion containment electrodes so high voltage but low current, but reasonable switching speeds, . Nightmare for spacing so multi-layer PCBs are best with ALL high voltage tracks on inner layers, then you only have to worry about pads and component legs for external spacing's. Multi layer boards also give you the ability to add screening layers if required.
For your thermal stuff have you thought of looking at Avvid or similar, had some fun with thermal pipes and thermal ribbon pipes, allowing a good thermal pathway from hard to reach areas or devices to a thermal radiator.
On these designs when it goes wrong it can be spectacular, I once had some diodes put in the wrong way on a PCB, in a prototype high voltage (35kV, 10-15KV 2X2.5kV and 6x1kV) all shorted together for one illuminating instance, for some reason I did not get the employer of the month award
but a verbal a*** kicking.
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