Kapanadze Cousin - DALLY FREE ENERGY

[nul-points]

I first tried to lower the drain voltage from 24V all the way down to 2V but the spikes and early activating of the MOSFETs were still there.

Then i added a 100uH toroid choke between center tap and drains supply rail, which made the spikes wider and increase tremendes, but shows that the drains are now kind of following the gate signals, see screenshot.
I had to lower the duty cycle as with max duty cycle (44%) the spikes are way up.

Hi Itsu

The gate-off behaviour of each device looks suspiciously like regular flyback spike & ringing (you can see the ringing truncated as the opposing device turns on) so i think you're seeing interaction between both halves of the push-pull arrangement, through the winding, enabled by the inherent body-diode of each device

ie. when one side switches off, flyback current is continuing to flow in from the opposite winding via the body-diode there

Since there is evidence of both turn-off spikes in each devices output, this *could* suggest that the ouput of your 24V PSU  has a higher drive impedance for some reason (output capacitor dry joint/failure maybe?!?)

Another possibility is that your secondaries are providing flyback output, rather than regular feed-forward output (not sure which output operation you intended)

You win this week's prize for Interesting circuit behaviour!  ;-)

All the best
np

[Hoppy]

Thanks Hoppy,

i will do some experimenting on this setup, but somehow i think that we all must have this specific problem, not me alone.
But i have taken already to much space on this thread with this.

I have wound a "verpies lossless clamp" yoke, so i could see later this week if that will work any better.


Regards Itsu

I think you could well be right that others have had this issue. I certainly had a problem with my PWM, in that it worked far better when I disconnected one of the mosfets which gave me much better power transfer and the flashing light 'effect'. My D to S waveforms were never very clean and I recall that the duty cycle pot on my PWM never gave me much adjustment.

I think I mentioned in a previous post that I tried Verpies lossless clamp and it did seem to work well until I inadvertently disconnected one of the electrolytic caps, which resulted in my PWM, drivers and voltage regulators going up in smoke: so keep your clamp circuitry intact!


Regards
Hoppy

PS. NP raises a good point about mosfet body diodes. These integrated diodes do not have very good specs, so could be breaking-down. It may just be a case of using higher voltage rated mosfets or moving over to IGBT's.

[Jeg]

Itsu, can you please attach the link to the video of you containing allega's blue box working with the Tesla secondary? I remember that you had feed it by some 130V dc. Do I remember right?

[itsu]

Hi Itsu

The gate-off behaviour of each device looks suspiciously like regular flyback spike & ringing (you can see the ringing truncated as the opposing device turns on) so i think you're seeing interaction between both halves of the push-pull arrangement, through the winding, enabled by the inherent body-diode of each device

ie. when one side switches off, flyback current is continuing to flow in from the opposite winding via the body-diode there

Since there is evidence of both turn-off spikes in each devices output, this *could* suggest that the ouput of your 24V PSU  has a higher drive impedance for some reason (output capacitor dry joint/failure maybe?!?)


Another possibility is that your secondaries are providing flyback output, rather than regular feed-forward output (not sure which output operation you intended)

You win this week's prize for Interesting circuit behaviour!  ;-)

All the best
np

Hi NP,

I used both a 24V battery and just lately a regulated PS (to vary the drain voltage from 24V to 2V) but both show the same behaviour (bypassing the drain voltage filtering choke/caps shows same thing).

Thanks for the prize   

Itsu

[itsu]

I think you could well be right that others have had this issue. I certainly had a problem with my PWM, in that it worked far better when I disconnected one of the mosfets which gave me much better power transfer and the flashing light 'effect'. My D to S waveforms were never very clean and I recall that the duty cycle pot on my PWM never gave me much adjustment.

I think I mentioned in a previous post that I tried Verpies lossless clamp and it did seem to work well until I inadvertently disconnected one of the electrolytic caps, which resulted in my PWM, drivers and voltage regulators going up in smoke: so keep your clamp circuitry intact!


Regards
Hoppy

PS. NP raises a good point about mosfet body diodes. These integrated diodes do not have very good specs, so could be breaking-down. It may just be a case of using higher voltage rated mosfets or moving over to IGBT's.

Even with only 2V on the drains?

Itsu