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NE555 interrupter and GDT problems

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Tonic

Mon Nov 26 2007, 09:42PM

Registered Member #528 Joined: Fri Feb 16 2007, 10:32PM
Location: Warsaw, Poland
Posts: 166

Uzzors wrote ...

It worked well for me right from the start, but it wasn't the first time I played with GDTs. I got 1 Âµs rise-times when running two IRFP450s, so at 500kHz it was mostly sinewave drive. At lower frequencies the waveform was more acceptable. You seem to have it working now, your waveforms look good with the powdered iron core. The ringing at 500kHz is probably just due to leakage inductance. By using a trifilar winding style instead of delta you can minimize leakage massively.

If you are still having problems with the circuit check that the output from the BD1XX totem pole is good before running a GDT. That way you can tell whether the drive circuitry needs fixing or the GDT. But with the BD1XX collectors connected directly to ground and +12V it should work perfectly.

jmartis wrote ...

hey, of course it will not go upto 30V if youre driving it with just 12. Maybe you should learn some basics on transistors and you'll se why is this, the transistors work as "emitter followers" so when the input is high, the output of the totem pole will never go above the input (actually it will be few 100s of mV lower) and vice versa.

Thanks, now I'm a bit reliefed. Yes, I need a lot of reading, but hey, not all peoples born with soldering iron or oscilloscope probes

Now, since the BD's output without GDT is squarewave, like as NE555's output, and with jmartis's exclamation, we can tell NE555 is working properly and I must concentrate on GDT. I guess my ferrite cores are worst quality, so buying a one from Ferroxcube would be a good idea for start.

Linas

Tue Nov 27 2007, 06:27AM

Registered Member #1143 Joined: Sun Nov 25 2007, 04:55PM
Location: Vilnius, Lithuania
Posts: 721

use TS 555....

Tonic

Tue Nov 27 2007, 09:12AM

Registered Member #528 Joined: Fri Feb 16 2007, 10:32PM
Location: Warsaw, Poland
Posts: 166

And what are differences?

Anyway, I'm going to buy TN32/19/13-3F3 core, there's datasheet:

What do you think?

Linas

Tue Nov 27 2007, 11:22AM

Registered Member #1143 Joined: Sun Nov 25 2007, 04:55PM
Location: Vilnius, Lithuania
Posts: 721

Ne555 generate <300KHz, and fall time is not wery good, also driving specification not wery good , TS555 generate up to 2,7MHz.... and i don't have problems sstc driving :)
I using for GTD driving my one developed scheme
sory for misspell

here is 10nF 350KHz driving mosfet , 1cm 12V

sstc runs on 1KW, and no heating,

almost

Tonic

Tue Nov 27 2007, 10:41PM

Registered Member #528 Joined: Fri Feb 16 2007, 10:32PM
Location: Warsaw, Poland
Posts: 166

Wow, that's a such nice waveform at those frequency and big load. But the NE555's limit of frequency surprised me, I was able to run at 570kHz without problem.

Indeed, fall and rise times are lower in TS555, by 4-5 times. Okay, gotta to hunt those TS555, thanks for advice ;)

By the way, I've ordered two Ferroxcube cores, one 3F3 and second 3C90. Anybody had contact with them?

Linas

Wed Nov 28 2007, 05:08AM

Registered Member #1143 Joined: Sun Nov 25 2007, 04:55PM
Location: Vilnius, Lithuania
Posts: 721

If you put load on graund ant output, NE555 waveform will be not very good, but if you use TS555, vith load almost nothing gona happen :)
Hiere is schort video, how my sstc work's

Tonic

Wed Nov 28 2007, 06:54AM

Registered Member #528 Joined: Fri Feb 16 2007, 10:32PM
Location: Warsaw, Poland
Posts: 166

Hmm..

wrote ...

This video has been removed by the user.

Anyway, today seller will send those ferrite cores. Probably I will receive tomorrow or in two days. Also, I've bought two nice probes (actually I have only one and that's ancient one, big, rigid, ugly and without hook at probe's end), they were sent yesterday. :)

Linas

Wed Nov 28 2007, 11:53AM

Registered Member #1143 Joined: Sun Nov 25 2007, 04:55PM
Location: Vilnius, Lithuania
Posts: 721

sory...

Dr. Dark Current

Wed Nov 28 2007, 03:08PM

Registered Member #152 Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384

Linas wrote ...

sory...

Hey linas thats a really nice sstc, are you using feedback or not?

Tonic, IMHO you can get decent ferrite cores from any equipment that contains a higher power SMPS (TVs, monitors, photocopiers etc.etc.). Sometimes they are in the line filter, sometimes they have a few turns of the ground wire on it.
I found some large cores in an old photocopier SMPS, they are excellent and for SSTC frequencies I need just ~4 turns on them.

I think the NE555 will work up to few MHz, if you dont like the slow rise/fall times you can always put a schmitt trigger on the output (e.g. parallel all 6 inverters of 74HC14 to drive your transistor output stage)

Linas

Wed Nov 28 2007, 03:28PM

Registered Member #1143 Joined: Sun Nov 25 2007, 04:55PM
Location: Vilnius, Lithuania
Posts: 721

I don't use feedback, but what would be the difference, if I use it? Would the spark be longer?

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