Kapanadze Cousin - DALLY FREE ENERGY

[verpies]

Video to show both the incorrect functioning using the both primaries attached and the correct functioning with 2 100 Ohm resistors attached:
https://www.youtube.com/watch?v=BhkQw19txPU

I watched your video again and I noticed, that while you have the primary windings disconnected and dummy resistors connected in their place, then the drain voltage falls rapidly when the gate goes high, but the drain voltage rises slowly (appears rounded off) when the gate goes low.

With resistive loads, the rise times and fall times of the drains should follow the rise times and fall times of the gates, but they do not.

This leads me to the conclusion that your MOSFET driving circuit sources a lot of current but sinks very little current and does not discharge the gate quickly to ground and does not keep it well grounded, leaving it defenseless against Miller turn-ON.

Why would that be?
Maybe the driver's "enable" input is not tied up ?  Maybe the driver is half-blown?  ...or the driver has a grounding problem?  ...or a diode is between the driver and the gate instead of a low-ohm resistor?  ...or the gate resistor is fried, ...or the gate resistor is accidentally a high-ohm resistor in parallel with a diode ..."Bad Boys Rаpe Our Young Girls, But..."

[itsu]

I watched your video again and I noticed, that while you have the primary windings disconnected and dummy resistors connected in their place, then the drain voltage falls rapidly when the gate goes high, but the drain voltage rises slowly (appears rounded off) when the gate goes low.

With resistive loads, the rise times and fall times of the drains should follow the rise times and fall times of the gates, but they do not.

This leads me to the conclusion that your MOSFET driving circuit sources a lot of current but sinks very little current and does not discharge the gate quickly to ground and does not keep it well grounded, leaving it defenseless against Miller turn-ON.

Why would that be?
Maybe the driver's "enable" input is not tied up ?  Maybe the driver is half-blown?  ...or the driver has a grounding problem?  ...or a diode is between the driver and the gate instead of a low-ohm resistor?  ...or the gate resistor is fried, ...or the gate resistor is accidentally a high-ohm resistor in parallel with a diode ..."Bad Boys Rаpe Our Young Girls, But..."

Hmmm,   food for thought,  thanks.

Maybe the driver's "enable" input is not tied up ?                                             correct, its floating like can be seen in many diagrams.  I will tie it up.
Maybe the driver is half-blown?                                                                      unlikely, as i have 2 having the same behaviour and have replaced recently  one of them
or the driver has a grounding problem?                                                           the both grounding legs are directly soldered on the MOSFET source which is grounded solidly.
or a diode is between the driver and the gate instead of a low-ohm resistor?      there is a low ohm (1.8 ) resistor for sourcing and a bat42 diode (anode to gate) for sinking i will double check them
or the gate resistor is fried,                                                                            unlikely, see answer 2, but will check
or the gate resistor is accidentally a high-ohm resistor in parallel with a diode.   i will check on that.

Regards Itsu

[verpies]

Maybe the BAT46 diode with C3/C4 in the drain snubber are causing this drain waveform asymmetry and rounding.
Forgive me for bringing it up if I had lost track and you had already removed the drain snubbers in that video. 

[verpies]

It is normal for the 1:1 autotransformer action, between the primary halves, to cause 2*V_CC to appear on the drain of the OFF MOSFET when the other MOSFET is ON and driving current through the other half of the primary winding by grounding its end.

More than 2*V_CC on the drain (2*24V in Itsu's case) is caused by the leakage inductance of the transformer (the inductance of one primary half, measured while the secondary^* is shorted).



^* or when the other primary half is shorted (because the autotransformer action makes the other primary half behave as a secondary winding)

[Hoppy]

More than 2*V_CC on the drain (2*24V in Itsu's case) is caused by the leakage inductance of the transformer (the inductance of one primary half, measured while the secondary^* is shorted).

That would question Itsu's choice of TVS voltage ratings, given that they could start conducting below 54V.