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4hv.org :: Forums :: High Voltage
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ZVS Video

Author Post
Adam Munich
Sun Dec 26 2010, 07:44PM Print View
Registered Member #2893
Joined: Tue Jun 01 2010, 09:25PM
Location: Cali-forn. i. a.
Posts: 2237
Finally got around to making one.
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Myke
Sun Dec 26 2010, 09:16PM
Registered Member #540
Joined: Mon Feb 19 2007, 07:49PM
Location: MIT
Posts: 969
You shouldn't even be holding the "ground" wire in the video... It may be sitting at a couple kV higher than the ZVS circuit due to leakage currents and such...

Always use a chicken stick
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Wyatt
Sun Dec 26 2010, 10:01PM
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Joined: Wed Dec 08 2010, 11:55PM
Location: The Granite State
Posts: 34
Nice.Very nice.
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quicksilver
Sun Dec 26 2010, 10:26PM
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Joined: Fri Mar 21 2008, 03:49PM
Location: Oracle, AZ
Posts: 679
You know, I really like the way you display your schematics on your pages. It's clean, neat and useful for a discussion. I've said this before but I notice now that you have made that type of illustration a "style" in your site. Frankly I really like it.
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Adam Munich
Sun Dec 26 2010, 11:44PM
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Joined: Tue Jun 01 2010, 09:25PM
Location: Cali-forn. i. a.
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I did it to help the n00bs. I think it's the most simple way to display things.

I'm also not holding the ground electrode, I'm holding the rubberized clip lead below it; my hand blocks the view.

Just noticed a lot of typos. Fix'd.
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Ash Small
Mon Dec 27 2010, 01:16AM
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Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4118
A picture tells a thousand words. Impressive schematics, Grenadier.

One point, and I'm probably wrong here, but I've been reading a bit on zero current switching and zero voltage switching on other sites, and I'd got the impression that the 'zero switching' concerned the transformer rather than the transistor(s).

I was under the impression, specifically, that if the transformer was switched when the current was zero, there would be no field to collapse, therefore no (in theory) transient voltages or wasted energy.

I was also (and I may well be mistaken here) under the impression that the discussion between zero voltage switching and zero current switching was something to do with phase lags, etc.


Some of this was read in the context of using current transformers controlling phase locked loops to control transistors via feedback.

Coming back to my original point, I was under the impression that the trick in a zero voltage switching circuit was to switch the transistor at a point when the voltage in the transformer was zero. Am I getting confused with something else?

(If you don't ask, you don't learn.)

EDIT: I think, specifically, that if the voltage across the primary is zero, the current, lagging by 90 degrees, is at a maximun, and that if it is switched at that point, the maximum amount of energy is delivered to the secondary, thereby producing a very efficient transformer.

This is what I thought ZVS meant.
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Adam Munich
Mon Dec 27 2010, 01:24AM
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I'm not certain myself. Anyone want to clear this up?
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Ash Small
Mon Dec 27 2010, 03:17AM
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Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4118
I found this:



Not read it all yet, but from what I've read so far, it appears we may both be correct.

EDIT: It seems to say you switch it when the voltage at the drain is zero. I think this means the voltage across the primary is also zero.

Maybe someone else can clarify things here?

EDIT: also found this, mostly about buck converters, but I think it suggests I'm wrong and Grenadier is correct.



and this, from wikipedia:

"Quasi-resonant zero-current/zero-voltage switch

Quasi-resonant switching switches when the voltage is at a minimum and a valley is detectedA quasi-resonant zero-current/zero-voltage switch (ZCS/ZVS) where "each switch cycle delivers a quantized 'packet' of energy to the converter output, and switch turn-on and turn-off occurs at zero current and voltage, resulting in an essentially lossless switch."[13] Quasi-resonant switching, also known as valley switching, reduces EMI in the power supply by two methods:

1.By switching the bipolar switch when the voltage is at a minimum (in the valley) to minimize the hard switching effect that causes EMI.
2.By switching when a valley is detected, rather than at a fixed frequency, introduces a natural frequency jitter that spreads the RF emissions spectrum and reduces overall EMI."

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Steve Conner
Mon Dec 27 2010, 02:00PM
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
ZVS means that the transistors switch after the voltage across them has been brought to zero by some other method. ZCS means likewise for current.

Either one reduces switching losses in the transistors quite a bit. I don't think it reduces losses in the magnetics. Although, in the Mazzilli circuit that you guys call "The ZVS", the tank capacitor recycles energy that would otherwise be lost through leakage inductance between the half primaries.
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HVPaul
Mon Dec 27 2010, 10:04PM
Registered Member #2321
Joined: Fri Aug 28 2009, 05:13PM
Location: Boston, MA
Posts: 34
Is that point to point construction?
Would you kindly post the the reverse side of the board?

Thanks

Grenadier wrote ...

Finally got around to making one.

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quicksilver
Mon Dec 27 2010, 10:13PM
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Joined: Fri Mar 21 2008, 03:49PM
Location: Oracle, AZ
Posts: 679
Blow up his pic: his leads ("traces") appear to be straight felt pen lines to his pin-outs. . It's a good enough pic so when you blow it up you can see the leads to the pin-outs drawn clearly. It's rather cute. I think it one of the more concise ones I've seen. Unless I have it all wrong and the reverse much more overlap than the felt-tip pen lines.
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Adam Munich
Mon Dec 27 2010, 10:31PM
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Location: Cali-forn. i. a.
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Here's the bottom of the board. I forgot to put this pic on the page.
I used a dremel to cut out the copper I didn't need, then I thickened the traces with solder. I then colored it with marker because I was bored. I designed the board on the fly as I always do. Somehow it usually works out.

Oh, that shiny stuff isn't flux, it's water. I used snow as a background for the last photo.



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quicksilver
Mon Dec 27 2010, 10:47PM
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Joined: Fri Mar 21 2008, 03:49PM
Location: Oracle, AZ
Posts: 679
I don't remember who did this one but it may be the best point to point I can remember for a Mazelli driver.

There is a certain imaging skill that just seems to be a gift with some folks. I sure haven't got it.

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Adam Munich
Mon Dec 27 2010, 10:57PM
Registered Member #2893
Joined: Tue Jun 01 2010, 09:25PM
Location: Cali-forn. i. a.
Posts: 2237
I'm very good with point to point, it's just a matter of finding a suitable base to keep it all steady. Point to point things just look so cool IMO, kind of like an art.
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radhoo
Mon Dec 27 2010, 11:15PM
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Myke
Tue Dec 28 2010, 01:23AM
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Joined: Mon Feb 19 2007, 07:49PM
Location: MIT
Posts: 969
quicksilver wrote ...

I don't remember who did this one but it may be the best point to point I can remember for a Mazelli driver.

There is a certain imaging skill that just seems to be a gift with some folks. I sure haven't got it.




Hahaha. That's my driver I made a while ago.
Thank you for the compliment.
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quicksilver
Tue Dec 28 2010, 04:25PM
Registered Member #1408
Joined: Fri Mar 21 2008, 03:49PM
Location: Oracle, AZ
Posts: 679
Well Myke, I don't want to be obsequious however let me say that I have used your model since I saw it! I just don't have the chops for what seems almost like "puzzle art". There were a great many things to consider in such a point to point size reduction.

I have a friend who actually does have some EE education (I have none) & I showed him (both pics of yours) & HE said "the guy is gifted" when I told him I was pirating the design.
My old buddy was the guy who actually explained how the Mazelli functioned in it's relationship to both frequency alteration and why it was a better choice design than others I had played with. The first thing he noticed (in the design) was that the significant components were brought together with higher current in mind: short, thick, stout connections, etc. Muy' suave, senior.


Thinking this over realistically, all the people who have made quality examples of this driver started with a decent heat-sink. IMO - if a person can get a hold of a heat-sink that will hold both MOSFETS; the wiring CAN be simplified better and better the more you build them! Perhaps one of the nicest schematics are on Grenadier's site. extrapolating from that I think that if one were to build one with some fore-thought - that particular item may just be a serious help to making a unit that not only lasts and works well but is something to be proud of.
One thing that has helped me was to put the schematic in a graphics program environment and shortening the traces. Certainly there are those folks that can build them right out of their head but if you're like me & don't have that gift......well - copying is the most sincerest form of flattery.
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