PI DAMPING EQUATION CHALLENGE

[detectormods]

Why not use two or more different value resistors switched in by a couple of small mosfets or even use the resistance of a mosfet in a controlled manner to optimize the damping.

[moodz]

Why not use two or more different value resistors switched in by a couple of small mosfets or even use the resistance of a mosfet in a controlled manner to optimize the damping.

Using resistors ... switched or not .. or mosfets as variable resistors is a variation of classical damping and exponential decay curves which is what we are trying to move away from.

[moodz]

Here is a simulation of nearly the same circuit I have on the bench. You have to let it run to the end. [ATTACH]n419164[/ATTACH]
I can also show you the real one functioning on the bench.

This is an example of energy conservation not damping .. the flyback energy is conserved to the next pulse .. hence the ability to generate substantial squarewave pulses from low voltages.

BTW have you got shares in a mosfet company ... there are 4 mosfets in excess in your circuit.

[detectormods]

Counter wound thin gauge interwinding to redirect fly back back to battery supply? Leyden jar?

[moodz]

This is an example of energy conservation not damping .. the flyback energy is conserved to the next pulse .. hence the ability to generate substantial squarewave pulses from low voltages.

Actually thinking about it the key solution to the Challenge is indirectly hiding in plain site in the type of pulse circuits like Tinkerers or CCPI types.
Using "The Formula" the damped current in the coil immediately ( eg 50 nanoseconds ) after fly back is 146 microamps. ( and this error is probably due to the coil resistance -- the formula does not adjust for this yet .. in this case 0.5 ohms )
So instead of conserving the energy for the next pulse ... you have to absorb it somehow

[detectormods]

https://patentimages.storage.googlea...ngs-page-4.png

This patent is near expiring.

[Tinkerer]

This is an example of energy conservation not damping .. the flyback energy is conserved to the next pulse .. hence the ability to generate substantial squarewave pulses from low voltages.

BTW have you got shares in a mosfet company ... there are 4 mosfets in excess in your circuit.

You are right, it is a manner of fast discharge of a (relatively) high inductance coil with energy conservation.
What I meant to say, is that the impedance of the capacitor is the perfect match for the fastest discharge. Would it be possible to generate a resistive load that imitates this impedance?

Also, does the well known snubber circuit fall into that category?

The mosfets? ha, ha, yes there are too many. This was a much larger simulation and I quickly removed most of the other parts to make it simpler.

[ivconic]

I follow your posts but I don't interfere because I don't like maths too much (read as; I'm bad at maths).
But there are times when math is not even needed to understand some things.
If you look at the electronic symbol for a mosfet; you will also clearly see the capacitor symbol on the gate.
I am of the opinion that this capacitance is a much bigger problem than the coil capacitance itself.
How is the coil discharged? Via mosfet, of course.
Then the capacitance of the coil is added to the capacitance of the mosfet junction.
And the problem becomes bigger, that is, the delay is bigger.
I think that a way to discharge both capacitances as quickly as possible should be found on the mosfet itself.
I'm currently transitioning to much faster computer hardware, so I haven't had time to install all the software.
It would be good to simulate the following:
As soon as the pulse on the gate goes out; if some negative voltage is immediately added; what is happening, what process?
Will the "capacitor" discharge faster?
A higher frequency (PPS) also increases the capacitance effect.
The proposed 25kHz at AMX makes sense and has its own explanation, but there is certainly a more pronounced effect of capacitance
than if the frequency were lower, say 1-3kHz.
Another dilemma; coil geometry, what happens if the TX coil is a "figure 8" type? Or if it's an "Omega" type?
Logically, it follows that a smaller number of windings of wire equals a smaller capacitance.
But in practice, it has also been shown that the capacitance is smaller even if the windings are relatively far from each other.
That's why "spider" and "basket" coils show better characteristics.
A larger distance between the wires allows a slightly larger number of windings.
But first of all I would like to see a simulation of adding a negative voltage to the gate after the pulse.
Those are some of my thoughts, questions and dilemmas. I hope they don't get in the way of the main discussion.

[Teleno]

Using resistors ... switched or not .. or mosfets as variable resistors is a variation of classical damping and exponential decay curves which is what we are trying to move away from.

But then your formula R = ????? implies a variable resistor. This is getting confusing.

Once I posted a technique that speeds up damping by discharging into a second inductor .

[moodz]

But then your formula R = ????? implies a variable resistor. This is getting confusing.

Once I posted a technique that speeds up damping by discharging into a second inductor .

I remember that circuit .. the sim ran really well ..... however this is something else if its true then its going to stand coil damping physics on its head ( maybe an overstatement ).

Who's interested in a patent ?

[Teleno]

I remember that circuit .. the sim ran really well ..... however this is something else if its true then its going to stand coil damping physics on its head ( maybe an overstatement ).

Who's interested in a patent ?

The peak discharge current is in the order of 50A. How do you deal with that?

I've been a patent examiner for 35 years, now retired for more than 2 yeats so I'm allowed to file patents myself. However they're very ecpensive and as individuals totally unable to defend any violations in court where the costs escalate to 5 or even 6 figures.

[Teleno]

Here's the best I can do.

R =4*3.1416*sqrt(L/C)*I(L2)+ 0.00001

[Gunghouk]

There is a fundamental priniciple at the heart of ( most ) PI technology and that is the damping of the coil.
I have seen almost endless discussion on how to improve it ... but what is it really ?

"That's easy" some will be saying .. you just calculate your critical damping resistance and off you go. .... well yessss ...

but what if I told you there is further improvement to be made ??
This is not a another PI circuit ... its the fundamental mathematics.

THE CHALLENGE .... What is the missing damping formula below ??? Its a a straight up formula that holds for all cases that the "classical" damping resistor holds for.
Its a much better damping method.

The trace for the standard damping is in top pane and the new formulat damping is in the lower trace pane.
Its not a trick question ... standard LTSPICE modelling.

Are these supposed to be on the same horizontal axis , thats not possible with this pulse setting ?
Why are the flyback voltages different for the same coil ?

[moodz]

Are these supposed to be on the same horizontal axis , thats not possible with this pulse setting ?
Why are the flyback voltages different for the same coil ?

Yes they are on the same axis.

Coil voltage is proportional to di/dt ... for the same coil and starting current .. if the you damp the coil faster the current drops faster so the di/dt is greater thus the voltage is higher.

[Gunghouk]

Thanks for your reply. An interesting challenge.