full wave CW multiplier won't work very well / High Voltage / Forums

Forums

4hv.org :: Forums :: High Voltage

« Previous topic | Next topic »

full wave CW multiplier won't work very well

previous 1 2 3 next

Move Thread

LAN_403

Mat

Tue Nov 04 2008, 06:27PM

Registered Member #1795 Joined: Sun Nov 02 2008, 02:05PM
Location:
Posts: 8

Hi,

thanks for that link.
I have been searching around for flybacks now and the circuits doesn't look too difficult to build.
That 1000W was way too much, I've made a mistake there. 500W should be sufficient.
But what makes a 500W flyback? The drive circuit or the flyback itself. Or both?
And how can I regulate the output current from the flyback? I guess by regulating the input voltage on the driver?

And can I still use my full wave rectifier in the case of a flyback or will I have to make it an half wave then?

thanks

Backyard Skunkworks

Tue Nov 04 2008, 06:55PM

Registered Member #1262 Joined: Fri Jan 25 2008, 05:22AM
Location: Maryland, USA
Posts: 451

Be warned! Running any flyback transformer at insane powers will cause it to die a firey death in short order!

You will need to run your laser in VERY short bursts to prevent the flyback from "releasing the mysterious blue smoke", if your driving it at hundreds of watts.

Dr. Dark Current

Tue Nov 04 2008, 07:04PM

Registered Member #152 Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384

You can put a resonant cap (usually ~50-100pF) on the output of the flyback to extract more real power from it (by real here I mean the opposite of reactive).

Theoretically, you could get up to 4x the power, so 500W seems perfectly doable. Just be sure you won't let the output voltage rise too high (open circuit) as this couold damage your transformer.

I have plans for a big (~2000W) HV SMPS which uses this resonance, so then I'll know how well it does really work.

Mat

Tue Nov 04 2008, 07:21PM

Registered Member #1795 Joined: Sun Nov 02 2008, 02:05PM
Location:
Posts: 8

The laser will have to run continuously. So short bursts are not good.
@Uzzors:
So you think it can continuously or not? 10min would be the max I think but apparently this is a long time for a flyback?

Does anyone know something more if doorknobs would work with NST because NST are the most common power supply for home built co2 lasers.

Arcstarter

Tue Nov 04 2008, 09:57PM

Registered Member #1225 Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253

Dr. Kilovolt wrote ...

You can put a resonant cap (usually ~50-100pF) on the output of the flyback to extract more real power from it (by real here I mean the opposite of reactive).

Lol noob question but this is only with ac flybacks, correct? Otherwise, it makes no since to me :P.

Myke

Wed Nov 05 2008, 12:19AM

Registered Member #540 Joined: Mon Feb 19 2007, 07:49PM
Location: MIT
Posts: 969

Yes, for a CW multiplier you need AC. For a marx generator you need DC.

Arcstarter

Wed Nov 05 2008, 04:18AM

Registered Member #1225 Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253

Myke wrote ...

Yes, for a CW multiplier you need AC. For a marx generator you need DC.

No, i am talking about the resonant cap for a flyback.

Myke

Wed Nov 05 2008, 07:01AM

Registered Member #540 Joined: Mon Feb 19 2007, 07:49PM
Location: MIT
Posts: 969

Whoops.
For resonance you need an AC flyback and a resonant cap...

uzzors2k

Wed Nov 05 2008, 07:45PM

Registered Member #95 Joined: Thu Feb 09 2006, 04:57PM
Location: Norway
Posts: 1308

Arcstarter wrote ...

Lol noob question but this is only with ac flybacks, correct? Otherwise, it makes no since to me :P.

Totally. Rectified flybacks provide semi-DC, so reactances are either zero or infinite.

Mat wrote ...

So you think it can continuously or not? 10min would be the max I think but apparently this is a long time for a flyback?

I've heard that flybacks are only rated for some tens of watts continuously, and that's under engineered conditions. When driven in an non-ideal manner and at much more power than intended I kinda doubt it would last more than a few minutes. CO2 lasers only need ca. 25kV to ignite and then 10kV or so to run on, right? Just add another stage or two to your current CW with the same ceramic caps, and it should be able to ignite, even if it can't supply 500W. Your NST is rated for 1kW, so if you just bypass the CW after the tube has ignited...

Dr. Dark Current

Wed Nov 05 2008, 07:57PM

Registered Member #152 Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384

I had one flyback run at ~400W CONTINUOUSLY for 6 hours and it survived.
It was the old style transformer with bare-wire secondary and without any resonance.

I really hope to get the resonant PSU finished someday, school and other things are getting in the way, but I believe if it works, it'll be something new in the high voltage SMPS world (such as resonant MOT arcs were in the mains-frequency "world")

previous 1 2 3 next

Moderator(s): Chris Russell, Noelle, Alex, Tesladownunder, Dave Marshall, Dave Billington, Bjørn, Steve Conner, Wolfram, Kizmo, Mads Barnkob