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Improved single transistor flyback driver

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Dr. Dark Current

Sat Jan 19 2008, 04:10PM

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

This could be interesting for the HV newbies that want to build their first flyback driver (maybe it can even be "implemented" in the Hv Wiki?)

I wanted a quick&dirty HV power supply for some lightbulb plasma experiments so I threw together the single transistor flyback driver. I played with it a bit and here's the result of my experimenting:

The 0.47uF cap should be a high-quality foil or film one. The value is not critical , my circuit starts to work well from 0.22uF.

The transistor gets warm but not as hot as with the original driver, but mainly the arcs are 3x as big and hot. The output voltage is also a bit higher.

I used an old transistor by "Tesla" (KD606), I think it should work just as well with 2N3055 or similar. (Note: a HOT or any other higher voltage transistor will not work, because they have different internal structure and the circuit will fail to oscillate)

Video here:]1200758621_152_FT0_pict0289.wmv[/file]

It is still not "fine tuned", maybe other people could try it and experiment with number of turns etc and post what works best for them?

HvHaxor05

Sat Jan 19 2008, 07:05PM

Registered Member #1116 Joined: Tue Nov 13 2007, 02:11AM
Location:
Posts: 35

WOW i am impressed i will be sure to make this circuit and try it out my self ty

Firnagzen

Sun Jan 20 2008, 01:23AM

Registered Member #567 Joined: Tue Mar 06 2007, 10:55AM
Location: Singapore
Posts: 147

I'll point out that since this circuit depends on the transistor being saturated to switch, the lower the saturatin voltage, the better. The MJE13007/8/9 transistors are fantastic for this.

MRacerxdl

Sun Jan 20 2008, 02:56AM

Registered Member #989 Joined: Sat Sept 08 2007, 02:15AM
Location: SÃ£o Paulo, Brazil
Posts: 476

Very impressive arcs :D I will try some time the driver with a MJE13007 that are High Speed Transistor (up to 100Mhz if I am't mistake)

Dr. Dark Current

Sun Jan 20 2008, 08:39AM

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

Firnagzen wrote ...

I'll point out that since this circuit depends on the transistor being saturated to switch, the lower the saturatin voltage, the better. The MJE13007/8/9 transistors are fantastic for this.

I don't know if they will work, they are 400V transistors.. Something is wrong with the HV transistors, they have much higher Toff time and lower Hfe (I was trying to find out the difference and I believe it was in how the base was made - epitaxial vs. triple diffused IIRC)

The MJ15003 is a nice transistor for this circuit

flannelhead

Sun Jan 20 2008, 12:52PM

Registered Member #952 Joined: Mon Aug 13 2007, 11:07AM
Location: Finland
Posts: 388

It looks a bit dangerous... Isn't it too dangerous to recommend to a beginner?
However, very nice arcs from such a simple circuit!!

Zum Beispiel

Sun Jan 20 2008, 03:35PM

Registered Member #514 Joined: Sun Feb 11 2007, 12:27AM
Location: Somewhere in Pirkanmaa, Finland
Posts: 295

That is *very* impressive

I would expect to see such arcs from a halfbridge or fullbridge, but certainly not from a single transistor! I'll have to try this some time.

flannelhead

Mon Jan 21 2008, 02:08PM

Registered Member #952 Joined: Mon Aug 13 2007, 11:07AM
Location: Finland
Posts: 388

I was wondering could this kind of circuit work for an sstc? Here is something similar:

Some beginners would really like it...

Dr. Dark Current

Mon Jan 21 2008, 03:24PM

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

spark wrote ...

I was wondering could this kind of circuit work for an sstc? Here is something similar:

Some beginners would really like it...

I don't know, since this circuit relies on the saturation of the ferrite core... Maybe it would work but the capacitor would need to be adjusted or removed completely. For single transistor SSTC see

DuartmaN

Wed Jan 23 2008, 12:20PM

Registered Member #1257 Joined: Wed Jan 23 2008, 08:59AM
Location: Beja
Posts: 1

Amazing! i can use this HV generator to excite a tesla coil? congratulations for this forum im from portugal, and in my contry dontÂ´t existe foruns abaut tesla coil and electronics either.

When i 14 yrs i contruct smal PVC tesla coil with a relÃ© and a iverted 12v 200v transformer! but workÂ´s with a smal sparkÂ´s, now i wold like to contruct a biger tesla coil but i need a HV generator, maybe contructed with a flybak T like thise on thius topic!

*sory my englis

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