Kapanadze Cousin - DALLY FREE ENERGY

[verpies]

I modified my nano-pulser to use the 74HCT02.

Now Hoppy will kill you and he might be right

Now no more flip-over from ns to us and the pulse width range is between 15 and 765ns (10Kohm pot.).

That is an excellent pulse width range.

Also i went back to using a MOSFET (IRF840) and driver (ucc27511), as with the KT926a transistor i doubt it if we will ever get it and the toroid saturated.
Video:  http://www.youtube.com/watch?v=avcGWerjM0M&feature=youtu.be

What if the Dally effect happens when the toroid is not saturated. Am I making Hoppy's point again

My objections:
Take a look at this time-indexed video link.
Isn't that a 100Ω resistor yet you are saying that it's a 0.1Ω resistor.

Also, forget the russian dots on the transformer diagram and make sure that your DSR Diode on the secondary side is conducting forward when your MOSFET is switched ON, on the primary side !!!

My suggestions:
You probably read in the UCC27511 datasheet that the two resistor on its output individually control the rise time and fall time on the gate of the MOSFET. 
Try to decrease the gate "sink resistor" to such resistance that the fall time is equal to the rise time when the drain is loaded only with a 4.7Ω-10Ω load resistor.  For this measurement disconnect the RC snubber and the transformer+flyback diode from the drain circuit. 
You can put your scope probe across the source/drain or across the 4.7Ω-10Ω resistor (which would make it a CSR as well as a Load).

The next step is to reconnect the flyback diode across the primary winding of the saturable transformer and connect them in the drain circuit (in series with a 0.1Ω CSR), disconnect the secondary winding and observe the current waveform across the CSR for saturation (curving up) with different pulse widths and drain supply voltages.   

Measure the slope of the rising edge of your current waveform - if you get much steeper slope than 300mA/μs at a 50V power supply voltage, then it means that you have saturated the core a long time ago.
This is because according to the latest table, the unsaturated inductance of your 6t primary is 173μH and because di/dt = V / L , that gives you di/dt = 289mA/μs.

Do this measurement carefully !!! - stop when the drain current approaches the max MOSFET rating.
If still you get no sign of saturation at the MOSFET current limit then add more primary turns (...or use the 12t secondary as the primary. Note that your 12t winding has inductance of 669μH, thus with the 50V drain supply, the unsaturated current slope is di/dt = 75mA/μs ).

[itsu]

My objections:
Take a look at this time-indexed video link.
Isn't that a 100Ω resistor yet you are saying that it's a 0.1Ω resistor.

Looks like it yes,  but there is a little point (.) in front of the 100, see picture (mind you that with shorted leads my meter reads 0.1 Ohm).

Also, forget the russian dots on the transformer diagram and make sure that your DSR Diode on the secondary side is conducting forward when your MOSFET is switched ON, on the primary side !!!

Ok, will take note of that, thanks.

By the way, i added a 2e video in the above post showing MOSFET gate/drain voltages with this new setup.

Regards Itsu

[verpies]

By the way, i added a 2e video in the above post showing MOSFET gate/drain voltages with this new setup.

I edited my previous post, too.

I just started to watch that 2nd video and I had to pause it when I saw that the gate voltage reached 20V (including ringing).
Lower it immediately or your MOSFET will get damaged. Even approaching this limit shortens the lifespan of the MOSFET considerably.

Also the IRF840 is a 8A, 500V transistor, isn't it?
Since the flyback diode protects it from HV flyback spikes you should have used a lower blocking voltage MOSFET with higher max drain current rating and lower R_DS-ON. , e.g. 300V and 20A.

[itsu]

I edited my previous post, too.

Ok, seen,  good info.

I just started to watch that 2nd video and I had to pause it when I saw that the gate voltage reached 20V (including ringing).
Lower it immediately or your MOSFET will get damaged. Even approaching this limit shortens the lifespan of the MOSFET considerably.

From IRF840 datasheet:

Gate to Source Voltage  . .VGS  ±20 V

Also the IRF840 is a 8A, 500V transistor, isn't it?
Since the flyback diode protects it from HV flyback spikes you should have used a lower blocking voltage MOSFET with higher max drain current rating and lower R_DS-ON. , e.g. 300V and 20A.

Correct,  ok, lets see what i have in the junk box  :-)

Regards Itsu

[verpies]

That ramp that I marked in blue color is caused by the action of the flyback diode connected across the primary of the transformer.

Ideally this flyback diode should be a low forward voltage-drop Silicon Carbide (SiC) Schottky diode rated at as much forward current as the MOSFET is conducting and at least the max drain supply voltage (2x is better - if possible).

With a good Schottky flyback diode, the falling edge of the current waveform has a long and gentle slope (low di/dt).

If for any reason you require a short and steep slope (high di/dt), e.g. in order to kill the current in the inductor quickly, then a flyback Transil should be used instead of the flyback Schottky diode (the Transil's breakdown voltage should be a little lower than the maximum blocking voltage of the MOSFET but higher than the drain supply voltage)

P.S.
Also, I like to connect another Schottky diode across the source/drain of the MOSFET in order to offload the parasitic diode inside this MOSFET, because when this internal parasitic diode starts conducting, it degrades the switching characteristics of the whole transistor.
The internal parasitic diode is a slow crappy diode, with high forward voltage-drop, and often needs help from its bigger brother - Mr. SiC Schottky.