I don't think a zener diode from gate to source would save anything.

 

Wouldn't a zener conduct when reaching its zener voltage and pass that excess voltage to GND ?

 

This article from AD seems to make sense.

 

This article from AD seems to make sense.
View attachment 195078

I apologize for my delay in responding to you. I had other things in my life that had to be done.

The main problem I have with your project is that so many things need to be fixed. You seem to think that a "comparator with hysteresis" is one simple, fixed thing. It isn't. A comparator with hysteresis is different for every application...and I am still not sure of your application (i.e. the details of your circuit) because every time you post something the circuit has changed. However, there are many other things that need to be fixed before you worry about the comparator with hysteresis.

Let's start with basics. Where does Vcc come from? What max current can be drawn from Vcc and what is Vcc when that current is drawn? Is the Vcc source grounded or isolated from ground? What polyfuse are you using? What is the cold resistance? What is the resistance at whatever max current you intend to pass through it during normal (i.e. not a fault condition) operation?

Next, it appears that you intend to provide power for the weld using the 2p3s supercap array. What voltage will one of the supercaps have across it when it is fully charged and ready to weld? After a weld, what is the voltage that remains on each supercap? Is that voltage sufficient for a second weld or do you intend to recharge the caps after each weld?

With that information the next step will be to discover a way to recharge the supercaps. I am not yet convinced that the scheme of your current schematic (that you posted as CD_SW.pdf) can do so without damage to the caps. Even if it can, the circuitry as currently shown will not work.

 

Let's start with basics. Where does Vcc come from? What max current can be drawn from Vcc and what is Vcc when that current is drawn? Is the Vcc source grounded or isolated from ground? What polyfuse are you using? What is the cold resistance? What is the resistance at whatever max current you intend to pass through it during normal (i.e. not a fault condition) operation?

Vcc as of now is generic power adaptor 20v 5A.
F1 fuse datasheet
F2 fuse datasheet
F3 fuse datasheet

Did not find anywhere mentioning about cold resistance.
Each pair of cap would be charged to 2.5v

 

Vcc as of now is generic power adaptor 20v 5A.
F1 fuse datasheet
F2 fuse datasheet
F3 fuse datasheet

Did not find anywhere mentioning about cold resistance.
Each pair of cap would be charged to 2.5v

Thanks for info. I can find only F1 in schematic CD_SW.pdf. Are F2, F3 different devices in schematic or alternate types/info for F1?

 

i have redrawn the schematic a bit. so its only F3 and F2 both on the right

 

i have redrawn the schematic a bit. so its only F3 and F2 both on the right

OK; I found F2, F3. You must keep me updated on schematic changes you make. Now we will work from CD_SW_3.pdf.