Negative discharge effect

[nelsonrochaa]

The IRF630 data sheet from Vishay has the characteristics of the body diode.
At the moment I am tending to believe the following: The device might actually be picking up power from the house mains! Here's what I'm seeing. The 3.2V signal to the gate is indeed critical. If I go a little bit above this value the voltage does not accumulate on the capacitor and the signs of line power pickup on the scope decrease. If I go a little bit below this value the mosfet isn't stirred up enough to allow the voltage to accumulate on the cap. Pulse width is also critical but the effect is harder to explain, I'll just have to show it. The pulse width determines the shape of the spike response and if it's too wide the peak spike droops and the rate of voltage accumulation on the cap decreases or stops. I think that the coil acts as the pickup for the line power and the mosfet in its just-barely-turned on state allows the negative discharge effect to happen on the capacitor.
Maybe. I'm not sure about any explanations yet. I am sure that at low Gate drive voltages, right around and below the 3.2 V value, I definitely am picking up power from the mains somehow. I don't know if this is what is being stored on the capacitor though.

Hi ,
if you put a cap of 200nf in parallel with the coil the result will be better . and the output in large capacitor have to be a load , without a load the circuit will not work optimal and maybe will fry the mosfet because the collapsed magnetic of the coil.
If you you monitor the charge in the cap when the voltage increase you will observe a defective commutation of the mosfet . 
When the coil collapse will fill rapidly the cap , but if the cap  is already full i observe that high voltage peake produce in the coil will try to find the path to the ground and return by the gate create a mistaken pulse  and the fault of the mosfet.
Another think that i test with good results : if you put a full bridge rectifier after the fast diode and connect the big cap in the bridge you will see that cap will charge more fast and the mosfet will work better.If you put the full bridge without the diode the result will be poor 
So far my best result is with a coil  3 ohm resistance. Can i ask how much resistance have the coil in your tests ?

thanks

[ayeaye]

So far my best result is with a coil  3 ohm resistance. Can i ask how much resistance have the coil in your tests ?

Thank you for repeating.

The static resistance of my coil, measured in the 200 ohms range, is 20.5 ohms. But the resistance of the crocodile wires is 1.3 ohms, so the resistance is 19.2 ohms.

I measured 80 mH on an inductor on which it was likely written 8.2 mH. I also calculated that the inductance of my coil is 0.16 H, assuming that the relative permeability of that core is 100. So the inductance of my coil may indeed be 0.66 H, which is 660 mH. I still cannot understand how could i make a mistake one decimal point. Then the relative permeability of the core is approximately 400, which is possible, but quite low for ferrite. The relative permeability of steel is 100 and, as i understand, the permeability of ferrite 3C90, common for toroid cores, is 2300 http://www.ferroxcube.com/FerroxcubeCorporateReception/datasheet/3c90.pdf .

[ayeaye]

What concerns measuring the inductance with a resistor in series, i have seen 3 different equations, yes 3, and all claimed to be about sine. But in my simple mind, coil's impedance with a sine waveform is 2 * pi * f * L , so R = 2 * pi * f * L and thus L = R / (2 * pi * f) , simple. So this i think is the right equation of these 3. Measuring inductance with an AC adapter is not so reliable though, because it assumes that the waveform in the main power supply is sine, when it differs from it anyhow, then there would be an additional coefficient. So wrong equation together with not so perfect sine, likely caused in my case a 10 times error.

Nelsonrochaa, if you did an experiment, then you may put the results up somewhere. The best in a video, so that everything would be known about the experiment, some small details may be important.

[TinselKoala]

http://www.youtube.com/watch?v=qUMb6e6QQIA

[ayeaye]

Many thanks TinselKoala, and looks beautiful too. I added a reference to this image of your circuit to the description of my video, and said that you are not conclusive yet about where the energy comes. This i found the best way to say what the state of the things are so far.

My video https://archive.org/details/ndischarge