dml wrote:Nice project. Is it aimed just at STs or others in the line?
dml wrote:I'm almost surprised to see a transformer without switchmode stuff, but I like the idea
dlfrsilver wrote:That's awesome This is very interesting ! You have my support
Will it be the same size as the old atari ST/E PSUs ?
exxos wrote:It has 2 switchmode regulators to generate the 5V &12V. This is done at about 20VDC instead of switching 350VDC on a pulse transformer (which is a huge heat loss)
Either way, a transformer would be needed. If I had gone down the pulse transformer route, I would have to get some made (expensive) or re-use the transformer on the existing PSU, which gets a bit pointless as its basically re-inventing the same design. I'm not a fan of 350V switching, so 20V is a lot safer and more reliable. The torodials are not to expensive to use anyway
dml wrote:The last time I worked on a switchmode supply was in the other direction - 12V in to 350v (pulsed) out, then stepped up again to ~2000v. It was built into an ATX box using some of the salvaged parts. No - don't ask
exxos wrote:The hardest parts were the inductors. This always drives me nuts as there are so many terrible types on the market that I could write a book on it it, in fact I think I did write a paper on it at some point With physical size constrictions and cost being a factor, some small compromises had to be made. Mostly it is the heat dissipation of the inductor. I worked it out at less than a watt which isn't much really, but this could be reduced further with more expensive inductors, but the cost jumps up to like £10 a pop. 4 of them is £40 so you can see my problem there. Really the more expensive inductors just are higher current rated, so thicker wire, larger core, so wattage lost isn't as much. But not worth paying £40 just to save about half a watt of heat dissipation. Overall, it shouldn't get as hot as the original PSU's anyway.
exxos wrote:Step ups are cool . My step ups tend to be in the 100's of KV area though http://www.exxoshost.co.uk/IMPULSE2015/ Hopefully I can get back working on this stuff in a couple years time. For some reason all my free time is taken up on Atari projects
stimpy wrote:That sounds very expensive, a quick look at Farnell suggests you get get 68uH inductors for around a £1, such as MSS1583-683MED although the current rating might be too close? What about shifting the frequency higher and taking a small hit on the switching losses? You got provision for putting an RC snubber across the diodes too?
dml wrote:Woah. Ok so you're an HV addict. Noted.
I'll saynomore here - but you might find some of my previous antics there: https://www.flickr.com/photos/kalidetro ... 608887415/
Not quite 100kv - but lotsa amps
exxos wrote: The problem with other machines is they need -12V and sometimes -5V so it makes the design more complicated.
DarkLord wrote:exxos wrote: The problem with other machines is they need -12V and sometimes -5V so it makes the design more complicated.
And that's not even counting the STacy with it's -20v !
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