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The 5AM SSTC

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ragnar

Thu May 18 2006, 07:21PM

Registered Member #63 Joined: Thu Feb 09 2006, 06:18AM
Location:
Posts: 1425

Pics now.. explanation later... tired... must.. sleep...

HV Enthusiast

Thu May 18 2006, 07:58PM

Registered Member #15 Joined: Thu Feb 02 2006, 01:11PM
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Posts: 3068

Cool. Is that completely powered off that lead acid battery??

...

Thu May 18 2006, 11:44PM

Registered Member #56 Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445

Looks good BP

I am guessing that toroidal transformer is powering the bridge, and the 12v cell is doing at least one of the isolated gate drives...

And for the most important question... How are the fets doing?

From the looks of it you are using a 4046 pll driver feeding a pair of your isolated gate drivers... But with only 2 of them I don't quite see how they are being used as designed, is one fet just connected in reverse of each driver so that it is off when the other is on?

I am also curious... Those sparks look really hot, which implies cw operation... But that is a pretty small cap on the transformer... What is the current draw?

Eagerly awaiting more results...

Oh, and if that is a 4046, have you tried audiomod? Still waiting for results on your mazzilli audiomod...

Good Luck!

Steve Ward

Fri May 19 2006, 01:15AM

Registered Member #146 Joined: Sun Feb 12 2006, 04:21AM
Location: Austin Tx
Posts: 1055

Looking at the waveforms posted, you certainly werent getting zero current switching. When you get ZCS, almost all of that noise dissappears.

ragnar

Fri May 19 2006, 06:21AM

Registered Member #63 Joined: Thu Feb 09 2006, 06:18AM
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Posts: 1425

Seemingly as I get closer to ZCS, the output dies down to about 1/4 what it is now and goes all noisy. I tuned this as to what gave the least hiss, drew the most current, and gave the smoothest gate waveforms.

A few kilohertz either way and the waveforms get even yuckier - it could be a coupling thing... or a leakage inductance thing? =)

Steve Conner

Fri May 19 2006, 10:10AM

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

Hey Matt,

That's pretty impressive for 5AM >_<

As regards the waveforms, did you find that maximum spark output happened at roughly the same PLL setting that gave smoothest waveforms? That's what should happen. If not, there could be a problem.

Desmogod

Fri May 19 2006, 01:58PM

Registered Member #139 Joined: Sat Feb 11 2006, 11:01AM
Location: Perth, Western Australia
Posts: 358

I found that the PLL needed a fair bit of power fed into it before it would stop spluttering, and locked onto a frequency. After that, she ran really nicely. Whereas the 74hc feedback circuit ran straight from the word go.
Could have something to do with my dodgy breadboarded PLL circuit though.
I just used the 10K pot, and my scope to tune it, and as steve said, the cleanest waveforms gave the largest output. Something is awry!
Also, how much power are you putting through that fullbridge?

ragnar

Fri May 19 2006, 09:42PM

Registered Member #63 Joined: Thu Feb 09 2006, 06:18AM
Location:
Posts: 1425

Aw thanks guys =)

EVR: Unfortunately not, the big lead acid battery is ~13V to the gatedrivers, and regulated to 12V for the VCO. The toroidal transformer you see to the left is providing 60V at ~4A.

Peter/...: The FETs do quite nicely - there's just enough dissipation on longer runs to take the chill off the heatsink, but not much more. Considering it was BLOODY COLD in there, I was more than happy to warm my hands on the heatsink occassionally :P

Yup, it's running CW. Depending on how far up I move the primary on the secondary, it draws between 3 and 10 amps. The capacitor looks small, however it's a 63V 10,000uF cap I daringly placed on the 60V-under-load winding of the transformer

No isolated drive boards here, there's just two pairs of gatedriver chips, each driving one half of the bridge through a GDT. I tried out some new cores and the waveforms looked (compared to my past work) very nice.

For your information guys, there's an alligator clip connecting pin14 of the PLL chip to ground! Nothing but the VCO running here, since I'm out of 555s and TL494s and won't have a board for the MAX038 until this weekend.

Steve Ward: this is as smooth as the waveforms get - F goes either way and they only get uglier.. :P

Power into the fullbridge has varied from ~180W to 660W... I blew my bridge rectifier to hell pulling 11A from it, but it didn't die in vain! It died short, and smoked for long enough for me to yank the power out. None of the FETs died! =-D

This afternoon I'll (fingers crossed, touch wood) hopefully be doing some engraved/drilled boards for, err... isolated gate drivers, lil mazilli/zvs, MAX038 boards... and a +-5V supply board to run the MAX038

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