Kapanadze Cousin - DALLY FREE ENERGY

[itsu]

@verpies

Did you mess up your harmonics?

lol,  probably, especially with the 220pF cap the signals are all over the place.

I will try with 4.7 and 10nF tonight.


@Hoppy,

The waveform begins to distort badly with a just a small increase in frequency, which is why I think Itsu had problems.

I keep my repetition frequency stable all the time at about 10Khz, so only variable is the drain voltage and the duty cycle of the pulse (11ns -500ns)


@All,

i tried with a IRF840 MOSFET and managed to blow that up too, but in a kind of controlled way  ;-)

IRF840 MOSFET with 10 Ohm gate-ground resistor and drain snubber (1nF-1KOhm to ground).
MAX4420 MOSFET driver (my last one) running on 17V.
0.1 Ohm CSR resistor in series with 12t of the little toroid (6 turn side open).
Drain voltage was 40V.
Increasing the pulse width from 11ns till 500ns shows nice increasing ramp up current across the CSR as in the blue line on saturation diagram in post #325, so no saturation.
40V PS shows increasing current until it hits the ns to us flipping point of my nano-pulser where the current stabilize at 0.6A (at 40V) slowly frying the 10 Ohm gate/ground resistor.

After exceeding this threshold point severall times, the MOSFET blew up, resulting in a blackend 10 Ohm gate-ground resistor now measuring 5 Ohm, a source-gate resistance of the MOSFET of 0.9 Ohm and a blown MOSFET driver output stage.

No, no video available this time :-(

But i think i am pretty sure i have seen no saturation of the little toroid during these exercises.

I will try to make a video of this tonight when things are running again.

Regards Itsu

[Black_Bird]

@itsu

Are you using the 220uH at the VDD line with the 2 uF capacitor to ground? This inductor limits the current. Also, in my circuit I am using a snubber with a 3.3nF in series with a 4.7 ohms resitor from the drain to ground, besides the diode ( a MRU820) in parallel with the transformer primary. My transformer primary is about 3.5 uH and has 10turns. This keeps the current under 25 A in the peak, for a maximum pulse width of 400 ns. I hope this helps. PS: The toroidal I'm using has an AL of 35 nH/turns squared and dimensions are external diameter 12 mm internal diameter 4.5 mm and height  4 mm.

[verpies]

But I'm also using a TL494 for my nano pulser, the pulse is 200ns long.  That's as short as I can make it at any frequency and have it be stable.   

The TL494 is not the only PWM Controller in the world.
There are many faster ones on the market.

[Hoppy]

Itsu,

Try a transorb between gate and source and drain to source. The gate transorb (TVS diode) should be rated at around 300W or more at a breakdown voltage under the max vgs which is 30V abs max for the IRF 840. You could also increase the gate resistance up to say 22R (which I'm using) to reduce any gate oscillations due to your very fast waveform edges. Ferrite beads can be used on the gate lead but not too much as they will slow the edges.

You may also need a more powerful mosfet.

Regards
Hoppy

[verpies]

My toroid measured on a Peak Atlas LCR meter is 312uH for 12T Sec and 88uH for 6T Pri. Frequency 200KHz. Both readings taken with other winding open circuit.

Those values seem very reasonable. Their ratio is a little less than 4 which can be explained by stray inductance and capacitance.
What are the OD, ID and TH dimensions of your toroidal core?