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SMPS Flyback question

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zippotix

Tue Jun 12 2012, 06:26PM

Registered Member #5208 Joined: Thu Jun 07 2012, 06:12PM
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Posts: 86

Yea, but I would like to have some juicy arcs. Like here

. I'm wondering what's that sound as the electrode is withdrawn, you can hear a cracky noise? Why it's not happening with other drivers, but only ZVS?

Dri0m

Wed Jun 13 2012, 05:26AM

Registered Member #4497 Joined: Thu Apr 19 2012, 12:53PM
Location: Behind you
Posts: 62

zippotix wrote ...

Yea, but I would like to have some juicy arcs. Like here

. I'm wondering what's that sound as the electrode is withdrawn, you can hear a cracky noise? Why it's not happening with other drivers, but only ZVS?

becuase //probably//, the arc collapses, but because of highly ionized air, it will instantly catch again, and that sound is spark.

zippotix

Wed Jun 13 2012, 04:19PM

Registered Member #5208 Joined: Thu Jun 07 2012, 06:12PM
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Posts: 86

Dri0m, that makes sense. I'm planning on using components from this circuit (

I have no clue where to get indcutor though, everything else is avaible.

Dri0m

Fri Jun 15 2012, 12:20PM

Registered Member #4497 Joined: Thu Apr 19 2012, 12:53PM
Location: Behind you
Posts: 62

zippotix wrote ...

Dri0m, that makes sense. I'm planning on using components from this circuit (

I have no clue where to get indcutor though, everything else is avaible.

don't buy inductors, the ones that fit into ZVS are quite expensive, buy only ferrite core and wind your own ;)

in case if you don't have LC meter:
1. get ferrite toroidal core 25mm outer dia, 15mm inner dia
2. wind 15-25 turns.

if you wind more turns, you will get higher but "shorter" voltage peaks; low current and higher voltage
if you wind less turns, you will get lower but "longer" voltage peaks; higher current and lower voltage, but arcs are more stable

m4ge123

Fri Jun 15 2012, 07:12PM

Registered Member #4118 Joined: Mon Oct 03 2011, 04:50PM
Location: MD
Posts: 140

Dri0m wrote ...

in case if you don't have LC meter:
1. get ferrite toroidal core 25mm outer dia, 15mm inner dia
2. wind 15-25 turns.

if you wind more turns, you will get higher but "shorter" voltage peaks; low current and higher voltage
if you wind less turns, you will get lower but "longer" voltage peaks; higher current and lower voltage, but arcs are more stable

Actually, the inductance of the input inductor shouldn't affect anything, but it should be at least 10x the inductance of the primary coil, preferably close to 100. An iron powder core is best for this.

zippotix

Sat Jun 16 2012, 10:10AM

Registered Member #5208 Joined: Thu Jun 07 2012, 06:12PM
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Posts: 86

Thanks, so I will wind my own :). I think I have toroidal ferrite lying somewhere. While I'm waiting for delivery of ZVS parts, I'm wondering how to limit current output from SMPS? Some ballast? A LED diode placed between SMPS output and flyback primary?

Sulaiman

Sat Jun 16 2012, 11:43AM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

To have a go at the original question;
Can you describe how you are driving the flyback with the halogen transformer?
especially how many turns of wire did you wind around the core?

zippotix

Sat Jun 16 2012, 03:21PM

Registered Member #5208 Joined: Thu Jun 07 2012, 06:12PM
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Posts: 86

Hello Sulaiman. It's a 11,5V 200W dimmable electronic halogen transformer. As far as I know, it outputs at frequency good for driving a flyback, so I guess it's about 15-20kHz. I just wound a new primary on the flyback, depends on the mood, right now it's 7 turns, but it can handle 3 turns too (although primary wire starts to smoke, insulation is melting after a while), and connected to halogen transformer output.

Sulaiman

Sat Jun 16 2012, 04:46PM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

Reducing the number of turns was going to be my suggestion ....
suppose you want the full 200W at 11.5V, current = 200/11.5 = 17.39 Arms !
You need thick wire - but NOT single strand (e.g. magnet wire)
Ideal would be several thin strands of 'magnet' wire twisted together,
or a few normal multi-strand household wires in parallel,
or some flattened copper pipe etc.

For more output reduce the number of primary turns,
for even more output put a capacitor across the primary winding
so that the primary inductance resonates with the primary capacitance at the output frequency of the halogen transformer.
Since I guess you don't have the equipment to measure inductance, frequency etc.
it will have to be trial and error.
Use film capacitors .. polypropylene foil/film as you would have to for a 'zvs' primary.
Look for capacitors that have KP, MMKP or MKP printed on them.
You should get output comparable to a 200W zvs !

I have to say this .... 200W at 10's of kHz and tens of kV is VERY dangerous.

zippotix

Sat Jun 16 2012, 05:41PM

Registered Member #5208 Joined: Thu Jun 07 2012, 06:12PM
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Posts: 86

Thanks for answer Sulaiman. But where to place a cap? Do you think 0.68uF MKP would do?

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