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how to tune SSTC?

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haikara

Fri Feb 18 2011, 11:11AM

Registered Member #3599 Joined: Mon Jan 10 2011, 05:50PM
Location:
Posts: 15

plz be gentle,
this is my first time making an sstc since i got a lil bored in sgtc. i think i want to step up another level of making TCs
ive made a schematic of my driver base on sumones schematic. its a high frquency sstc driver and i want to audio modulate it.

all is tested and simulated in spice and it give me a nice square wave output in my fets but after hooking a GDT, my ic and fet got pretty hot and draws 13A!!! yes 13 A only for that stupid driver but didnt destroyed itself.

tried several ferrites that didnt draw much current and power up the bridge. unfortunately there was no current draw in my bridge. my gdt is 14-20 turns 1:1 centertapped primary. i play with turns in gdt but i cant get an output. there was no current draw in the half bridge either. I dont have scope yet. so its hard to see wave form. im trying to power up the bridge up to 40v for testing.

btw i wound quadfilar, is that the correct term? on my gdt

EDIT:

how you tune ur SSTC?
say, i have 2mhz secondary coil freq
my driver can be adjusted 1khz to 2.2mhz of frequency through gdt
what can be adjusted to tune it to resonance?
thanks

Goodchild

Fri Feb 18 2011, 04:56PM

Registered Member #2292 Joined: Fri Aug 14 2009, 05:33PM
Location: The Wild West AKA Arizona
Posts: 795

Your problem is quit simple really, You need a DC blocking cap in series with your GDT leads, also the reason it didn't explode is because the MOSFETs you are driving the GDT with are more than capable of handling 13A.

I would highly recommend finding a new design to start with, this one is not very good. It is lacking gate protection on the MOSFETs no filtering or GDT DC block and no self resonance.

I would recommend Steve Ward's mini SSTC. I built it as my first SSTC and I can vouch for it's completeness and ease of building and testing.

(and yes it can be audio modulated)

If you don't use it, at least study it as it is very well documented and will provide some in-site on the problems you are having with your current design.

Wolfram

Sat Feb 19 2011, 02:01AM

Registered Member #33 Joined: Sat Feb 04 2006, 01:31PM
Location: Norway
Posts: 971

Goodchild wrote ...

Your problem is quit simple really, You need a DC blocking cap in series with your GDT leads, also the reason it didn't explode is because the MOSFETs you are driving the GDT with are more than capable of handling 13A.

He's using a push pull driver to drive the GDT. There is nowhere to put a DC blocking cap on the primary side.

Gregory

Sat Feb 19 2011, 03:25AM

Registered Member #2922 Joined: Sun Jun 13 2010, 12:08AM
Location:
Posts: 226

put a resistor on the central tap terminal of the GDT primary, it will limit the current..

Sat Feb 19 2011, 10:48AM

Registered Member #2485 Joined: Fri Nov 27 2009, 02:31PM
Location: Germany
Posts: 11

try using gateresistors for Q1 and Q2
something around 10 Ohm should work

Adam Munich

Sat Feb 19 2011, 04:38PM

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

May I suggest:

Edit: DIP model.

cjk2

Sat Feb 19 2011, 04:49PM

Registered Member #51 Joined: Thu Feb 09 2006, 04:17AM
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Posts: 263

Does the 4046 have complimentary outputs? If not I suspect that is the problem.

haikara

Sat Feb 19 2011, 07:16PM

Registered Member #3599 Joined: Mon Jan 10 2011, 05:50PM
Location:
Posts: 15

o yea, i had an output last night, i input 70v and i got 1cm arcs. my variac hums so much cuz its only 2A. after about 15 secs mosfet blew because of over heating...
i suspect that my mosfet not fully turning ON? so it dissipates lots of power. am i correct?

damn i dont have scope. i will wait my moms decision if she can buy me one and i hope so :c

is tektronix tds220 good?

@gregory, i did that already, but i think it messes up the output in GDT, didnt have a breakout. tried several ohms 5-100 @ 5w cuz i dont have required values that has high wattage.

@mb, will try that and see what happens

thanks for the inputs guys

EDIT:
ok i think it works now, the reason it draws 13A because the 4046 chip died. i think it was shorting something so..
the only problem now is my cap in half bridge heats a lot. it is a polypropylene capacitor (red colour) i will change it to a higher quality cuz it is only a temporary.
Also i will change my secondary coil to 2.xx MHz cuz my driver max freq can get up to 2MHz

I wonder how to tune sstc's? any suggestions?first approach? i might read other thread as well while waiting for replies.

thanks

nem96

Mon Feb 28 2011, 10:40AM

Registered Member #3722 Joined: Sun Feb 27 2011, 03:26PM
Location:
Posts: 7

I am sorry to interrupt, but i have a simmilar problem. I want to make audio-modulated vttc for science fair. Can I apply audio-input to some of the grids of two Ei-nis pl519 penthodes. Should I use some transformer to amplify the input to 200 vAC to drive the grid and what grid should I use. I also have two pl504 penthodes, so could I connect in parallel 2xpl519 and 2xpl504 so i can get more power input?

uzzors2k

Mon Feb 28 2011, 04:39PM

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

I've only skimmed over the posts here, but is your 4046 oscillating? From what I can see you have no resistors setting the frequency range, among other things. Maybe start here and confirm that you actually have a signal to amplify.

EDIT: Oh, I see you got breakout.

Never mind then.

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