Is that a joule thief?

[Jeg]

Hi Jeg,

The oscillator frequency will change based on how much you load the output.

GL.

Hi GL
I'd like to ask you if there is any way with this setup, to avoid this freq. changing. I am thinking to add a hand made smoothing capacitor of 0,5nF to smooth a 10KHz resonance. Flyback is already have the internal diode, so i calculated the capacitor with 10mA output, 20KV, 10% ripple, and 0,1ms between charging peaks. Do you think is a good idea first to fix the sparking gaps around the rotor and then to re-calculate the cap?

tnks in advance

[Groundloop]

Hi GL
I'd like to ask you if there is any way with this setup, to avoid this freq. changing. I am thinking to add a hand made smoothing capacitor of 35pf to smooth a 10KHz resonance. Flyback is already have the internal diode, so i calculated the capacitor with 10mA output, 20KV, 10% ripple, and 0,1ms between charging peaks. Do you think is a good idea first to fix the sparking gaps around the rotor and then to re-calculate the cap?

tnks in advance

Hi Jeg,

I think that the only way to avoid a frequency change with load is to use some sort of a feed back
from the output that control your oscillator. Or you can also use a fixed frequency oscillator that
control a switch connected to your fly-back transformer. If you look at a typical switch mode power
supply, then you will see that the SMPS uses a circuit to determine the output voltage and then
couple back to the input switch via opto-couplers to keep the output voltage at a constant level
during various loads. So I think your best option is to use a 4047N oscillator to keep your switch
at a constant frequency. One circuit that uses a 4047N IC as a constant frequency oscillator is
attached this post. The frequency is set by the 220K pot and the 100nF capacitor. These values
can be changed to suit your needs. My build of this circuit had a little more electronics on the board
than shown in the attached circuit drawing. Hope this help you in your quest.....

GL.

[Jeg]

Thanks a lot GL. Nice driver schematic. The reason i don't want to use it in this hobie project is because i 'd like to explore auto resonance and its effects. What if i add before the charging capacitor the following coil with the de-q-ing diode? Will it make it more steady in frequency?
By the way. Is it possible to show me the equation that calculates this change due to load?

tnks

http://www.richieburnett.co.uk/dcreschg.html

[Jeg]

I think i got it. The gap introduces a capacitance which varies with  electrode distance, so as the frequency. After the charging resonant circuit, this capacitance doesn't affect anymore the secondary coil, so frequency will be steady (as far as i think that i understand! )

[Groundloop]

Thanks a lot GL. Nice driver schematic. The reason i don't want to use it in this hobie project is because i 'd like to explore auto resonance and its effects. What if i add before the charging capacitor the following coil with the de-q-ing diode? Will it make it more steady in frequency?
By the way. Is it possible to show me the equation that calculates this change due to load?

tnks

http://www.richieburnett.co.uk/dcreschg.html

Jeg,

I'm more a builder type than a mathematical type, so I do not know much about the formula you ask about. :-)
You will need to look at the net or maybe some of the math experts on this forum can chip in with an explanation?

GL.