High input voltage Joule Thief (12-15V)

[d3x0r]

How can I make a joule thief which is able to run on 12-15V input?


I find that if I make the voltage that high, the gate never triggers off...


is it possible to make an P-Channel mosfet sort of thing that can work from the high side of voltage instead of from ground?

[Groundloop]

How can I make a joule thief which is able to run on 12-15V input?


I find that if I make the voltage that high, the gate never triggers off...


is it possible to make an P-Channel mosfet sort of thing that can work from the high side of voltage instead of from ground?

d3x0r,

You can try increase the number of turns on your coil.
10 turns for each input Volt will probably do it.

GL.

[d3x0r]

Okay thanx, I had tried that a little (only went from 1 to 4), and didn't see any improvement, going from 1 to 12 worked better;


So now I get about the same current draw at 12 as 4 previously.


Thanx again.

[Groundloop]

Okay thanx, I had tried that a little (only went from 1 to 4), and didn't see any improvement, going from 1 to 12 worked better;


So now I get about the same current draw at 12 as 4 previously.


Thanx again.

d3x0r,

Also increase the bias voltage resistor value. A 10K variable resistor with a 1K series resistor will do fine.
It is easier to tune the JT with a variable resistor when using higher input voltages.

GL.

[d3x0r]

Okay again, that works pretty good; I can limit the current that way at any given voltage, and produce the desired output voltage.  (I can actually way overdrive my target voltage)


The system, though, contains a lot of other OSC (oscillating shuttle circuits).


Illustrated here...


https://www.circuitlab.com/circuit/qb8znp/oscillators-joule-thief-signal-generator/


I used to have a signal generator source (TL494 tunable PWM module); replacing this with a joule thief has simplified the generation of voltage into C1+180V.  (oops I have two C1's)


Tuning the capacitor which is (C4+C5) (have to include a ground in every floating loop for simulators to be happy, so it's hidden between 1/2 the cap on each side)


The ground connection on L4-L6 loop is very important.  Depending on the side, it neuters the signal or allows it through with more power.... Since This is a joule thief and it's by nature mono-polar, that single pole is encouraged in all systems; so this ground point is on the low side of L4 as L1+L3 induce its voltage.


L1+L3 are currently two separate windings that are tied together; but can be used independantly for 1/2 the inductance which is about the same effect.  Just changes the tuning of resistance to M1.   The mosfet is not specified; but it is 30V, 20Vgate, 22A, 330pf gate capacitance, 8ns on, 4ns rise, 8ns off, 8ns fall...


Running with 12V input, and 0.06A (up to 0.10A) provides a good level of voltage.


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However, the frequency isn't really affected; though it is a composite of effects from itself, the feedback from L7 flywheel oscillator, and, I can include the capacitor C1 -HV, which changes the frequency most.


But here's where I'm a little stuck.  I've tuned L7:C4+C5 to be 2-4 times the freqency that the joule thief seems to run at with only itself connected.  Windings L5 and L4 I disconnected from their respective parts, and it seems to run about 43Khz (give or take a bit), with everything connected it oscillates at 357Khz; the capacitor used at C1+180V is a 400V 80uf capacitor... but as it charges its impedance (to L5?) increases...


I dunno; but then now I'm at a point that changing capacitance on L7 isn't having much of an effect +/-50% of itself; so with so many things working in tandem, is the resonant tuning less important, since other parts end up limiting the full swing?  Surely if everything is WRONG, it flattens out, and basically I can't drive the joule thief to start without allowing higher voltage (reducing the resistance) significantly; but then the joule thief's frequency is the prevailant one....


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I just wish I knew someone I could have a conversation, that would bear with that I have 0 clue what the vernacular is for this field.