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ZVS Video

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Adam Munich

Sun Dec 26 2010, 07:44PM

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

Finally got around to making one.

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

Wyatt

Sun Dec 26 2010, 10:01PM

Registered Member #3490 Joined: Wed Dec 08 2010, 11:55PM
Location: The Granite State
Posts: 34

Nice.Very nice.

quicksilver

Sun Dec 26 2010, 10:26PM

Registered Member #1408 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.

Adam Munich

Sun Dec 26 2010, 11:44PM

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

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.

Ash Small

Mon Dec 27 2010, 01:16AM

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

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.

Adam Munich

Mon Dec 27 2010, 01:24AM

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

I'm not certain myself. Anyone want to clear this up?

Ash Small

Mon Dec 27 2010, 03:17AM

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

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."

Steve Conner

Mon Dec 27 2010, 02:00PM

Registered Member #30 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.

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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