Really?
I would think 500hz plenty.

 

Really?
I would think 500hz plenty.

500hz is but when scanning but can the 3us dead-time mosfet switch from 0 to 1?
Is there any problem if I increase the dead time to 300us?

 

1 would go to 500us.

 

1 would go to 100us.

dead time=100us phả

1 would go to 500us.

Thank you

 

Does this circuit protect the mosfet gate via diode D4?
I need 24v->30v power supply is that ok?
What is the maximum switching speed of this circuit?

 

View attachment 359822
Does this circuit protect the mosfet gate via diode D4?
I need 24v->30v power supply is that ok?
What is the maximum switching speed of this circuit?

1)Yes, the zener protects the Gate of mosfet nicely.

2)It should work with 30V with any problems.

3)Since the Gate is discharged through 10k resistor only (slow), it will work up to 1KHz only. Also, at 3A current expect a significant switching losses since the mosfet will be in linear region too much time.

I would use a npn-pnp buffer as people here recommended you.

 

1)Yes, the zener protects the Gate of mosfet nicely.

2)It should work with 30V with any problems.

3)Since the Gate is discharged through 10k resistor only (slow), it will work up to 1KHz only. Also, at 3A current expect a significant switching losses since the mosfet will be in linear region too much time.

I would use a npn-pnp buffer as people here recommended you.

Is this circuit correct?

 

View attachment 359824

Is this circuit correct?

Looks correct, but not convinced it's needed IMHO.
I would try both circuits in real life not in a simulator and see if there's any reason that warrants one design over the other.

 

Please help me check if this circuit runs at 350khz ok?
I need to supply power from 12V to 48V with gate protection how?
How much current through Q4 Q3?

 

View attachment 359834

Please help me check if this circuit runs at 350khz ok?
I need to supply power from 12V to 48V with gate protection how?
How much current through Q4 Q3?

No it won't. You will get 48V on the MOSFET gate which will break it.

 

No it won't. You will get 48V on the MOSFET gate which will break it.

So how to protect mosfet gate with 48V power supply?

 

So how to protect mosfet gate with 48V power supply?

So how to protect mosfet gate with 12->24V power supply?

 

So how to protect mosfet gate with 48V power supply?

The driver in #27 works with 48V Vcc , but the AO4614b has 40Vds_max, so you have to change the mosfet type then. Also the bc337 is 45V Vce only (Q3).
The 12V zener ensures the mosfet gate is safe.

 

R37 about 1K to 10k I replace 100ohm is it ok?
how to check switching speed

 

View attachment 360099

R37 about 1K to 10k I replace 100ohm is it ok?
how to check switching speed

At 48V Vcc the current through R38 will be (48-12)/100=360mA. That makes quite high losses, about P=R.I.I=100x0.36^2=13W on R38 and about 4.3W on zener&R37.
But it would work.

 

Please help me check if this circuit runs at 350khz ok?

The turn on/off is through a 100 ohm resistor. That is not very good for 350khz.

Can you move the load to the supply and the N-MOSFET to Ground? This will solve all these problems.

 

At 48V Vcc the current through R38 will be (48-12)/100=360mA. That makes quite high losses, about P=R.I.I=100x0.36^2=13W on R38 and about 4.3W on zener&R37.
But it would work.

how to check switching speed
What is the switching frequency of my circuit with a 24V supply?

 

how to check switching speed
What is the switching frequency of my circuit with a 24V supply?

If you are satisfied with 3Watt losses….You can use a simulator with real transistors models like LTspice, etc..
It will show you the delay between input pulse (from Mcu) and load current. I prefer the delay to be less than 1/20 of pulse width, but some folks may have no problem with 1/10.

In numbers:
If pulse width is 20us i tolerate a 1us delay.

Also the simulator shows you the mosfet turning off transition, how much switching losses on mosfet you can expect.

Roughly, from my practice with 100 ohms in gate you can go up to 10khz.

 

I test the switching speed according to the picture is correct (Node A) R39=12ohm ?

 

It's slightly more complicated than this in real life, but a good approximation to the switching time is the RC time constant of the MOSFET's gate capacitance and the drive resistance. In you case, the drive resistance is equal to R37 in parallel with R38.