I want to implement some PID control for a 48 W heater cartridge. I have a microcontroller which can only putout a PWM output at 3.3 V and 8.1 mA. I current am trying to use a IRLZ44N MOSFET. Is the circuit I have sketched below suitable for controlling the MOSFET?
Thanks for any help.
I current am trying to use a irlz44n mosfet. Is the circuit I have sketched below suitable for controlling the mosefet?
The maximum gate-source voltage for the IRLZ44N is +/- 16 volts: -
Your circuit is turning it on with 24 volts and this is a big no-no. Most MOSFETs are not rated above +/- 20 volts so, I would urge you to use a proper MOSFET driver controlled from (say) a 12 volt regulated supply.
Or, split R4 into two resistors and voltage limit the junction with a 12 volt Zener diode like this: -
You will need to make calculation regarding the split resistors to see what power rating is needed. The upper split resistor should not push more current into the zener so that the maximum power of the zener is approached for instance.
50 kHz is quite high for this application; if you used (say) 100 Hz you would minimize unwanted power dissipation in the driving circuits.
Also, add ~ 100 Ω in series with the gate of the FET. This will slow down the turn off and avoid damage from inductive spikes. Also add 1-10 uF between supply and ground on the board where you have the driver circuit. If there is excessive inductance (wire length) between the 24 V supply and the circuit, then it would possibly oscillate during turn-on and -off.
Lastly, if this circuit's input could be disconnected from the MCU, it would be safer to add a 10k pulldown at the input to ensure it remains off.
To simplify the circuit, you can eliminate R5, and make R2 10 kΩ.
