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120kv 10-20mA SMPS

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Proud Mary

Sun Apr 24 2011, 01:16PM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

Your overall costs in bringing a 120kV X-ray machine up to national safety standards will be so great, that it would hardly seem worthwhile worrying about the relatively small cost of suitable HV diodes.

For example only:

Linas

Sun Apr 24 2011, 03:30PM

Registered Member #1143 Joined: Sun Nov 25 2007, 04:55PM
Location: Vilnius, Lithuania
Posts: 721

tonight i going to make first insulation test for transformer, with 2x more voltage between layers, i hope it will hold, if not, probably will have to go with multiplier solution

also, is BYV26E is better than SUF4007 ? ( i can get for low price more around 400 of them)

BYV26E pdf

SUF4007 pdf

[Update]

i made ~1kT secondary, and i should get around 10-20Kv. but instead i get just 3kv.
after more test i made secondary with one turn and notice that i have just few volts per turn. how is that posible ? since i use 8T primary with 150V amplitude driving signal ( i tested, i really have 150Vac@60Khz )
oh, well, i will go with full wave multiplier,and i hope i will be able to reach some good voltage and low ringing.
Just need to find best solution for my case( i have 40kv 2nf capacitors, so i need 12x 40kv <0,05A fast diodes )
i can trade mosfets for diodes if someone have them

radhoo

Tue Apr 26 2011, 07:40PM

Registered Member #1938 Joined: Sun Jan 25 2009, 12:44PM
Location: Romania
Posts: 701

Linas you can build a few of these:

and hook them in series using a few diodes.

Or you can build a bipolar multiplier like this:

or this:

Linas

Mon May 02 2011, 08:59PM

Registered Member #1143 Joined: Sun Nov 25 2007, 04:55PM
Location: Vilnius, Lithuania
Posts: 721

is it good design ?
5,30nF are 15KV
2,65nF are 30kv
2,00nF are 40KV
diodes will be 45kv 0,1A 100ns
f=20-60KHz, 8KV<V<15KV

Adam Munich

Mon May 02 2011, 11:41PM

Registered Member #2893 Joined: Tue Jun 01 2010, 09:25PM
Location: Cali-forn. i. a.
Posts: 2242

Why not have all the capacitors the the same rating? Per stage voltage never changes.

Also, my reccomendation is to use a dual ended CW to generate +65kV and -65kV. This should save you a lot of headache.

teravolt

Tue May 03 2011, 04:34AM

Registered Member #195 Joined: Fri Feb 17 2006, 08:27PM
Location: Berkeley, ca.
Posts: 1111

hi Linas I built a multiplier and got carried away. this multiplier puts out a calculated +-80kv. I used plain 1n4007's and 30kv 500pf doorknobs. each half uses the full wave CCW dubilier you are proposing. Instead of a half wave transformer I use 4 flybacks 2 out of phase driven by a mazillii circuit. I could have easily made it single ended had I used grading rings or oil. The key I think is that you should use doorknob caps instead of disc. hear is my lame video.

When you get to those large voltages the losses can equal the power you are putting in it so it helps to have a AC source that can keep up with it.

Linas

Tue May 03 2011, 05:26AM

Registered Member #1143 Joined: Sun Nov 25 2007, 04:55PM
Location: Vilnius, Lithuania
Posts: 721

Grenadier wrote ...

Why not have all the capacitors the the same rating? Per stage voltage never changes.

Also, my reccomendation is to use a dual ended CW to generate +65kV and -65kV. This should save you a lot of headache.

I can't. Since all generator will have single 220v plug. I will have 65kv voltage differences in 50hz 4v tube heater supply.
Also i have just 8x2nf and 10x5nf capacitors, so the best i can do i show in schematic.

Patrick

Tue May 03 2011, 05:37AM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

Linas wrote ...

this is good looking work! nice. did you mill that tray, or mould it or what?

Wolfram

Tue May 03 2011, 05:39AM

Registered Member #33 Joined: Sat Feb 04 2006, 01:31PM
Location: Norway
Posts: 971

Linas wrote ...

is it good design ?
5,30nF are 15KV
2,65nF are 30kv
2,00nF are 40KV
diodes will be 45kv 0,1A 100ns
f=20-60KHz, 8KV<V<15KV

That looks like a very good design to me. Have you done simulations to see if it can deliver the power you need?

Linas

Tue May 03 2011, 05:49AM

Registered Member #1143 Joined: Sun Nov 25 2007, 04:55PM
Location: Vilnius, Lithuania
Posts: 721

simulation doesn't really works. . free run will do 80kv. but even small load and no voltage left...
hm, if all diodes and capacitors are ideal, i get very very nice results :)
(note that simulation doesn't work for 20KHz, program send error ,i use 2KHz, so in real life i should get better results)

Also very good output voltage, its stability is +-1KV (1% of output :D)

(1kv/div@3KHz)
sadly i believe in reality is not that perfect , but i will use square wave which is more "energetic" and also at least 5x more frequency

right now designing SMPS with some nice IGBT (IXGH40N60C2D1) so it will give me around 2KW, also have flybacks with 2500T@120Ohms

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