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Load Balancing SMPS to Flyback help please!

MrSnips

Apr 7, 2021
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Apr 7, 2021
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Hi all,
This is my first post so please be gentle.
Firstly, I am aware of the dangers of this project but I'll be damned if that's going to stop me. So in the spirit of learning...
I need to balance the out put of a thermally protected 220 to 12v LED dimmable transformer(105w) with the input of a...flyback transformer. (Ex CRT)
Yes I am building a Jacobs Ladder, it is in a glass tube.

I have rudimentary electronics knowledge, I have never failed to repair domestic electronic things but in this case I'm stumped.

I tried a few different 12v lightbulbs ( as resistors) on the dc side of the transformer but it either didn't function or the arc extinguished in the same fashion as happens with a direct connection.
I assume that the transformer is getting into an over current or over voltage condition and shutting down as when I disconnect and reconnect a few second later it works again briefly.

So how do I match these so I can get an out put from my flyback? I assume 105 watts is plenty of power as the ladder is shaded from air flow so the thermals to raise the arc are undisturbed.

Any ideas?
 

MrSnips

Apr 7, 2021
8
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Apr 7, 2021
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That should be matching not balancing. Could I use a coupling transformer?
 

Technomaniac

Oct 31, 2020
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Oct 31, 2020
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100
Your 12v lightbulbs will probably have a lower resistance than you are expecting, when their filaments are cold. The resistance will increase when they are hot (lit).. I'm not quite understanding. Are you feeding the DC output from a LED power supply into a winding of an EHT transformer? If so,you are probably saturating the core of the EHT transformer, and there will be no output from it with a DC input, if that's what the LED supply puts out.
 

MrSnips

Apr 7, 2021
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Apr 7, 2021
Messages
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Hi Techomanic, thanks for the reply!
Yes, I am using the output of an LED power supply, however it is actually 20khz pulsed dc. (via my JYETech DSO150 scope)
Yes into a EHT transformer. In this case I have wrapped 6 turns of insulated wire around the free side of the ferrite of a salvaged flyback transformer from a CRT computer monitor.

The initial phase is working well for about 1-2 seconds, then it abruptly stops working. The power supply boasts thermal reset so I'm assuming that is the state it is getting into. However I'm open to suggestions!
 

MrSnips

Apr 7, 2021
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Apr 7, 2021
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Heehee Technomaniac! Sorry!.Tech-o-manic is a good one too:)
 

MrSnips

Apr 7, 2021
8
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Apr 7, 2021
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Am I correct to think about this problem this way...
If my power supply is capable of putting out 105 watts and be happy under that condition.(No over heat), and the voltage is 12v, then the power supply impedance is R=V/I

So I = 105/12 = 8.75A,
R = 12/8.75 = 1.37Ohm supply impedance.

Do I understand correctly that if I match this impedance on my output I will see 105watts more a less?
 

Technomaniac

Oct 31, 2020
100
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Oct 31, 2020
Messages
100
Maybe you could try coupling the EHT tranny to your pulsed power supply through a capacitor. Xc= 1/(2 pi FC) where Xc is the capacitive reactance which use as the impedance. So then with the capacitor in between, you could look at the waveform either side of the cap to see what attenuation it is giving you.
 

MrSnips

Apr 7, 2021
8
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Apr 7, 2021
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Superb! Thanks for that tip.
I must spend a few days getting to grips with this and related equations. TBH I have all but avoided them in the past but now it has a real world application which I really want to solve.
I find mathematics very abstract until there is an application with a tangible outcome, then it becomes real for me.
I will report back!
 

MrSnips

Apr 7, 2021
8
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Apr 7, 2021
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Here is what I got with my first random value: 10uF
C = 1/2*3.14*20,000*0.00001
C = 1/1.256
C =0.796Ohm

So I will reduce the value of my capacitor 5uF I get 1.61Ohm. I must go somewhere in between.
1.333Ohms is resulting from 6uF in that equation. I'll give that a shot later
 
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