Controlling a high side with an N ch mosfet

[sandorex]

Hello, my soldering iron died 6 days after buying it >:( (KSGER T12 from banggood) so i want to make my own cause it seems like a fun project and isn't that complex

I've used these schematics as inspiration
Electronoobs
jurgis DIY T12 Soldering Iron

I didn't want to mess with charge pump and i only have N channel mosfets salvaged from a power supply currently, so remade the schematic and im interesting will this work with PWM ?

I need the mosfet to be fully on so heat dissipation will be minimal and i wont need to use a heatsink

[raschemmel]

Any mosfet will work with PWM. It just depends on whether the PWM is correct.

High side switching is generally done with P-channel mosfets.
That's an N-channel in your schematic:
Mosfet symbols

[Paul_B]

sandorex:
I didn't want to mess with charge pump and I only have N channel mosfets salvaged from a power supply currently, so remade the schematic and I'm interesting will this work with PWM ?

Of course not!

sandorex:
I need the mosfet to be fully on so heat dissipation will be minimal and i wont need to use a heatsink

So you absolutely need the charge pump.

sandorex:

The electronoobs circuit from which you have copied uses a P-channel FET.

The second circuit from Jurgis shows a charge pump - it will generally work as long as the PWM value does not approach either 100% or zero - but is OK if the PWM is zero - switched off.

[sandorex]

Thank you a lot for the input

High side switching is generally done with P-channel mosfets.
That's an N-channel in your schematic:
Mosfet symbols

The electronoobs circuit from which you have copied uses a P-channel FET.

Yes unfortunately i do not have a P channel (mos)fet at hand, i will change the schematics when i get one, this is my only real iron the other one is the transformer one so i want to make it work

The second circuit from Jurgis shows a charge pump - it will generally work as long as the PWM value does not approach either 100% or zero - but is OK if the PWM is zero - switched off.

I honestly don't know much about charge pumps, but what i've seen from the simulations it doubles the voltage right?
In the simulations the Vgs with a charge pump exceeds 20V which is maximum for my mosfet (STP40NF03L), the simulation i've done, won't that damage the mosfet? should i add a zener maybe?

I was banging my head would it be possible to use the mosfet to switch the low side but i cannot think of a way of reading the PTC then, if you have some suggestions / solutions im all ears

[raschemmel]

You still believe this : ?
"cause it seems like a fun project and isn't that complex

I guess we have a different definition of 'fun':

"I was banging my head would it be possible to use the mosfet to switch the low side but i cannot think of a way of reading the PTC then, if you have some suggestions / solutions im all ears"

Where's the charge pump ?

"Yes unfortunately i do not have a P channel (mos)fet at hand"

Usually if you're going to make an omelette it's
kind of important to have eggs...

[sandorex]

You still believe this : ?
"cause it seems like a fun project and isn't that complex

I guess we have a different definition of 'fun':

"I was banging my head would it be possible to use the mosfet to switch the low side but i cannot think of a way of reading the PTC then, if you have some suggestions / solutions im all ears"

Well it was more fun at first :), learning about mosfets but i still find it fun as im learning about opamps and things

_{I guess im just cheap cause i don't want to pay $3 shipping for couple of mosfets}

[raschemmel]

"I didn't want to mess with charge pump and i only have N channel mosfets "

If you take away the long neck do you stll have
a giraffe ?

Where's your op amp circuit for the temp sensor ?

Have you breadboarded the circuit you posted in your OP ?

Have you done this sort of thing before or is this
your first rodeo ?

[Paul_B]

sandorex:
In the simulations the Vgs with a charge pump exceeds 20V which is maximum for my mosfet (STP40NF03L), the simulation I've done, won't that damage the mosfet? should i add a Zener maybe?

That should reasonably take care of the V_GS problem.

Can't make head nor tail of the simulation.

[sandorex]

If you take away the long neck do you stll have
a giraffe ?

Im pretty sure i don't have a 10uF capacitor for the charge pump so i was trying to avoid buying components

Have you breadboarded the circuit you posted in your OP ?

Yes and it did not work out well, the mosfet was heating up a lot
I may have worded the original post a bit weird as i wrote it at 3 am, sorry

Have you done this sort of thing before or is this
your first rodeo ?

First time

Where's your op amp circuit for the temp sensor ?

The op amp circuit is the same as in Jurgis' schematic

Can't make head nor tail of the simulation.

Is the simulator bad or you're just not familiar with it?

I guess ill just order a P channel mosfet
It will make my life easier i guess

[raschemmel]

Where is the charge pump ?
Is it C1 & R3 &D2?

[sandorex]

raschemmel:
Where is the charge pump ?
Is it C1 & R3 &D2?

Yes

[raschemmel]

Thanks .
I didn't see the "CHARGE PUMP HERE " sign.
My bad.