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How to drive a low Rdson mosfet for PWM

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Zero999:

--- Quote from: langwadt on May 23, 2022, 07:48:42 pm ---
--- Quote from: Zero999 on May 23, 2022, 10:48:10 am ---
--- Quote from: DavidAlfa on May 23, 2022, 10:35:56 am ---Assuming the temperature need to be read several times per second, does a relay switch make any sense to you?
It'll die in no time.
The series TC is pretty common even for big brands like JBC.

Just get a cheap P-ch mosfet like the AOD403, make your life easier!

--- End quote ---
I agree. A P-MOSFET is easier.

Here's an example circuit. It will work with a 24V supply and 5V MCU signal, but the AO6407 must be replaced with a MOSFET with a drain-source voltage rating of at least 30V. The AOD403 is a decent suggestion.


--- End quote ---

~2.5mA * 2.2K = ~5.5V

stick a zener across R1 you you want to be sure

--- End quote ---
If you go for the zener, why bother with the resistor?

The OP is running the MCU at 5V, so the gate-source voltage will be about -9.5V. Another possibility is adding an LED in series with Q1's collector, to act as an indicator.

langwadt:

--- Quote from: Zero999 on May 23, 2022, 08:26:11 pm ---
--- Quote from: langwadt on May 23, 2022, 07:48:42 pm ---
--- Quote from: Zero999 on May 23, 2022, 10:48:10 am ---
--- Quote from: DavidAlfa on May 23, 2022, 10:35:56 am ---Assuming the temperature need to be read several times per second, does a relay switch make any sense to you?
It'll die in no time.
The series TC is pretty common even for big brands like JBC.

Just get a cheap P-ch mosfet like the AOD403, make your life easier!

--- End quote ---
I agree. A P-MOSFET is easier.

Here's an example circuit. It will work with a 24V supply and 5V MCU signal, but the AO6407 must be replaced with a MOSFET with a drain-source voltage rating of at least 30V. The AOD403 is a decent suggestion.


--- End quote ---

~2.5mA * 2.2K = ~5.5V

stick a zener across R1 you you want to be sure

--- End quote ---
If you go for the zener, why bother with the resistor?

--- End quote ---

you need something to turn off M1

Zero999:

--- Quote from: langwadt on May 23, 2022, 09:36:13 pm ---
--- Quote from: Zero999 on May 23, 2022, 08:26:11 pm ---
--- Quote from: langwadt on May 23, 2022, 07:48:42 pm ---
--- Quote from: Zero999 on May 23, 2022, 10:48:10 am ---
--- Quote from: DavidAlfa on May 23, 2022, 10:35:56 am ---Assuming the temperature need to be read several times per second, does a relay switch make any sense to you?
It'll die in no time.
The series TC is pretty common even for big brands like JBC.

Just get a cheap P-ch mosfet like the AOD403, make your life easier!

--- End quote ---
I agree. A P-MOSFET is easier.

Here's an example circuit. It will work with a 24V supply and 5V MCU signal, but the AO6407 must be replaced with a MOSFET with a drain-source voltage rating of at least 30V. The AOD403 is a decent suggestion.


--- End quote ---

~2.5mA * 2.2K = ~5.5V

stick a zener across R1 you you want to be sure

--- End quote ---
If you go for the zener, why bother with the resistor?

--- End quote ---

you need something to turn off M1

--- End quote ---
You're right.  :palm:

I wouldn't bother with the zener, then.

DavidAlfa:
Why keep going with this and the silly overcomplicated thing?
Switching a heater at 36KHz is plain stupid, a normal implementation will be 10-100Hz, so the turn-off resistor will do the job fine, neither a zener is required, just a resistor divider.

CMTan:

--- Quote from: DavidAlfa on May 23, 2022, 11:32:27 pm ---Why keep going with this and the silly overcomplicated thing?
Switching a heater at 36KHz is plain stupid, a normal implementation will be 10-100Hz, so the turn-off resistor will do the job fine, neither a zener is required, just a resistor divider.

--- End quote ---
Agree totally.

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