Kapanadze Cousin - DALLY FREE ENERGY

[Void]

Hi Nick. Yes, with the duty cycle pot set to max duty cycle it looks like
my dead time is about 7%, as the scope measures the duty cycle for
each output at 43%. Yeah, I would think that 43% should be good enough,
but I was curious if any of you guys were running at closer to 50% duty cycle.
See the duty cycle measurements in the attached scope shot.

[NickZ]

   No. No one that I know of. But I wish that it could be run at 50%, or closer to it.
   Thanks for showing your duty cycle readings. Now I know where to set it up, to be able to see it showing the readings.

[Void]

Hi Nick. I see. I did a bit more experimenting with it by applying some voltage to pin 4,
the dead time adjust pin, and it looks like I won't be able to get the dead time
any less than the 7% I have now. Applying voltage to pin 4 (0V to 3V) actually
increases the dead time even more. I just checked, and, according to the TL494 data sheet,
grounding pin 4 gives the maximum duty cycle, so it looks like 43% is about the best I can
get with a TL494.

If you ever have any questions on the Siglent scope, feel free to ask.
BTW, what model of Siglent scope do you have?

[itsu]

Hi Itsu, guys:

I am bread boarding a TL494 PWM driver circuit this evening, and I am wondering if you left
the dead time at the default as I have done so far (which I think is maybe 5%), and if you think
having this much dead time between the outputs of the TL494 (Pins 9 and 10) will be detrimental
in any way, other than having a little less output? See the attached scope shot of the outputs on
pins 9 and 10 showing the default dead time.

Void

according to the data sheets like https://www.onsemi.com/pub/Collateral/TL494-D.PDF (page 6),

the TL494 has a deadtime control comparator with a fixed 120 mV input offset which limits the minimum output deadtime.

It limits the minimum output deadtime to approximately the first 4% of the sawtooth−cycle time.

This results in a maximum duty cycle on a given output of 96% with the output control grounded (singel ended operation), and 48% with it connected to the reference line
(push pull operation as we use it).

Additional deadtime may be imposed on the output by setting the deadtime−control input to a fixed voltage, ranging between 0 V to 3.3 V.

In my tests with TL494's, the max duty cycle in push pull mode is around 44 to 45%, but it differs.
When i decrease the duty cycle i have less output and / or more distortion on the MOSFETs drains, so i leave it at max. (45%) duty cycle.
If 50% would be even better i don't know as the TL494 won't go there, perhaps other PWM's can, but i doubt it.

Itsu 

[Void]

Hi Itsu. Yes, thanks, that is what I had determined as well for push pull mode.
The best duty cycle I can get with my current setup is 43%. Maybe with some circuit
tweaking I could maybe get it to 45%. Anyway, 43% should be good enough.