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Steve Conner

Fri Dec 03 2010, 11:34AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

Well Pinky, you better ask if his transformer cores are gapped, if they're not then no cookies for you.

How big was the last SMPS you designed anyway? (Full disclosure: my last one was a 5 watt DC-DC converter for a battery-powered instrument

)

Pinky's Brain

Fri Dec 03 2010, 11:39AM

Registered Member #2901 Joined: Thu Jun 03 2010, 01:25PM
Location:
Posts: 837

Tiny, some uC power supply in farming equipment controller ... it was said in jest.

radhoo

Fri Dec 03 2010, 11:46AM

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

Steve McConner wrote ...

Well Pinky, you better ask if his transformer cores are gapped, if they're not then no cookies for you.

You two are funny, hope you can help me with the "regularized" driver as well.

To answer the above: no cookies, just an "air" gap ( some very thin insulator ).

The board connected before the multiplier looks like this:

I might be able to get one, but it looks very complex.

So I wonder if I can do something close to the original supply, but with a simpler approach: driver+feedback for regularization+displaying the voltage on a meter + some basic protection.

Steve Conner

Fri Dec 03 2010, 11:59AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

Regularized? Oh, I get it, you mean "regulated".

If the core had an air gap, then maybe it was driven as a flyback after all. But sometimes forward converters have an air gap too.

But then, the 2N5039 transistors seen on that board are only 90V rated. That doesn't seem like enough for a flyback driver. It doesn't seem like enough for any sort of driver!

Some old HV power supplies in smaller sizes had a big iron-cored transformer that supplied a low voltage to a linear preregulator before the inverter, where more modern designs would use a buck converter running straight off rectified line voltage. The 90V rating of the transistors makes me think that's what might be the case here. The inverter always ran at full duty cycle, and the output voltage sense divider fed back to the linear preregulator.

That would probably be the easiest approach for a hobbyist, especially if you're a bit of an electronics noob.

radhoo

Fri Dec 03 2010, 12:19PM

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

Thanks for the reply,
I don't have the 2N5039 board, but I might be able to get one. Is it worthy?
What would be the approach to go, using that board?

What about a driver from scratch, without using the 2N5039 board? What kind of oscillator should I consider? How do I correlate the divider's feedback with the oscillator?

Ash Small

Fri Dec 03 2010, 12:46PM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

radhoo wrote ...

Thanks, Ash.

On the schematics I've also printed the board's ID. Do you perhaps have access to the original schematics, including the driver?

I still try to resist the temptation of connecting a 555 timer driver to this board, but I should come with a better solution soon, since I really want to power it up.

The EDI RM800B info I supplied relates to a 100Kv 10 stage Glassman multiplier.

The custom diode used in that circuit is pictured below.

The earlier schematics I provided relate to Glassman EW series power supplies 0f 500W and up to 60KV.

I assume the RM800B is suitable for your circuit as it is rated for 8KV, (your capacitors are rated for 7.5KV)

I think the relevant bit is the 250 nanosecond recovery time.

EDIT: I've since discovered that this diode is used in a 20mA 100KV multiplier, not 100mA as I originally stated.

Pinky's Brain

Fri Dec 03 2010, 12:55PM

Registered Member #2901 Joined: Thu Jun 03 2010, 01:25PM
Location:
Posts: 837

Steve McConner wrote ...
If the core had an air gap, then maybe it was driven as a flyback after all. But sometimes forward converters have an air gap too.

Without a split secondary or primary and a DC load wouldn't you pretty much always need an air gap no matter how you drove it?

Radhoo, if you want a regulated supply then just getting the Glassman driver seems worth it. Saves a lot of headaches.

radhoo

Fri Dec 03 2010, 01:04PM

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

Pinky's Brain wrote ...

Radhoo, if you want a regulated supply then just getting the Glassman driver seems worth it. Saves a lot of headaches.

Thanks. The 6 pins connector to the multiplier board is easy and "approachable" , but I'm concerned about the other board, the left side connector is giving me headaches. Since I don't even have the schematics for this, it is even more complicated.

Ash Small

Fri Dec 03 2010, 01:12PM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

Ash Small wrote ...

EDIT: I messed up here, tried to edit the post but ended up quoting and replicating.

radhoo

Tue Dec 07 2010, 10:16PM

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

Probably by tomorrow I'll be getting the driver board:

Hope this will provide some progress. However there is still a lot to figure out before I can re-use the multiplier modules.

The temptation to drive them blindly by some kind of PWM is getting higher. Not sure what to do.

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