hello, I made a circuit to control the fan speed

1. first circuit

BAT -> 24V input







2. second circuit






both circuits work fine. But there's one difference

first circuit : FET temperature 38℃
the gate voltage is set to 12v to lower the temperature of the fet.
second circuit : FET temperature 28℃

Q1) why does the second circuit works better?(i think it's all about switching-time but how could i fix it?)
Q2) if first circuit is wrong, is there a gate driver circuit(totem pole, push-pull) that does not require the use of an extra 12 volt regulator?

It's my hypothesis.
1. first circuit's gate current is lower then second circuit
2. first circuit's gate resistor is too high (i changed R5 270R, R9 10R but i got same result)

 

The second circuit is active push/pull allowing the gate to charge and discharge faster than the first circuit.

I'm sure you can find a gate driver that will handle 24 volts at VDD, but you will still have to clamp the output to the MOSFET maximum gate voltage.

There may well be gate drivers with a built-in output clamp but I'm not familiar with any, someone else here will be better informed.

 

Is that the MOSFET gate voltage you are displaying for the first circuit?
If so, the rise-time is somewhat slow, which could increase the MOSFET dissipation, and thus its temperature.

You can speed up that rise-time by going to a totem-pole driver (sim below), which should reduce the MOSFET dissipation:
The D1 12V Zener clamps the output voltage, which allows it to operate from 24V without exceeding the MOSFET max gate voltage.
The MOSFET model I had has the same gate charge as the one you show, so should have a similar rise time.
The green trace is the MOSFET gate voltage, and the yellow trace is the simulated fan current.

But the MOSFET temperature rise for the first circuit does not seem excessive, so it's not clear that this extra circuitry is worth the added complexity, although it's just an added transistor and diode.

 

But the MOSFET temperature rise for the first circuit does not seem excessive, so it's not clear that this extra circuitry is worth the added complexity, although it's just an added transistor and diode.

because my firt circuit's pull-up resistor is too slow
i mean when the circuit is powered on, the Fan operates for about 0.3 seconds

 

when the circuit is powered on, the Fan operates for about 0.3 seconds

I don't understand.
What happens after 0.3 seconds?

 

I don't understand.
What happens after 0.3 seconds?

when powered on(my power supply on) 0.3 second fan is running and then off
my circuit is inverted. if PWM zero -> fan running

that's why i put R4(pull-up)

 

my circuit is inverted. if PWM zero -> fan running

That's not true for the circuit you posted.

 

That's not true for the circuit you posted.

oh i'm sorry. my wire was problem it works fine
i was confused because I was experimenting with another circuit

 

Why is Q12 to a PNP instead of the NPN I used for the totem-pole circuit??
Using a PNP causes a direct short through Q11 when on, and will likely zap Q11.

 

Why is Q12 to a PNP instead of the NPN I used for the totem-pole circuit??
Using a PNP causes a direct short through Q11 when on, and will likely zap Q11.

oh it's mistake i used npn both

but it didn't work it didn't turn off

 

but it didn't work it didn't turn off

Then there's likely a circuit error since you seem to have a problem reading schematics.
Double check all the connections.
Does the diode have the correct polarity connection?
Post the exact circuit you built.

 

Then there's likely a circuit error since you seem to have a problem reading schematics.
Double check all the connections.
Does the diode have the correct polarity connection?
Post the exact circuit you built.

oh i don't have D1 , is D1 12V zener diode?

 

oh i don't have D1 , is D1 12V zener diode?

Yes.
But the lack of that wouldn't keep the circuit from turning off.

Check the orientation of D2 in my circuit.
If that's backwards, the MOSFET won't turn off.

 

Yes.
But the lack of that wouldn't keep the circuit from turning off.

Check the orientation of D2 in my circuit.
If that's backwards, the MOSFET won't turn off.

the problem was my code
non-invert mode fast pwm

it works good but fet get's hot over 40 ℃

 

it works good but fet get's hot over 40 ℃

So can you look at the MOSFET gate voltage with the oscilloscope when it is running?

 

So can you look at the MOSFET gate voltage with the oscilloscope when it is running?

it's 24V, zener was broken and MCU was broken too.
i have to re wiring

 

So can you look at the MOSFET gate voltage with the oscilloscope when it is running?

this is MOSFET's gate

 

this is MOSFET's gate

Looks good.

 

Looks good.

it works good, but FET get's heat
4.5A -> 45 ℃
5A -> 60 ℃

3A -> 40 ℃ (my target Current)

and this circuit is inverted output so, how can i change this circuit to non-inverted?
can i change to push-pull circuit?

 

and this circuit is inverted output

How is it inverted?
High on the input causes the MOSFET to conduct.
If you want inversion, then just add a logic inverter at the input, or invert the generated PWM signal.