Saturday, 8 June 2019

microcontroller - Level shift circuit MCU to MOSFET


I have a H-bridge that is being supplied by 12V and using around 10A. I am turning it on/off with a microcontroller that has an output of 0V-5V. The switching frequency is "super low" so the gate charge of the MOSFET is not a problem. I am trying to "convert" this 5V logic to 12V logic (0V-12V), and thought of something like this:


schematic



simulate this circuit – Schematic created using CircuitLab


Is there any redundacy, any problem or anything missing from this design? I can see this work, but this will be in "somewhat of a commercial product", and would like it to be as robust as possible.



Answer



I suggest something more like this:


schematic


simulate this circuit – Schematic created using CircuitLab


Drive into a 10nF load looks like this:


enter image description here


Edit: The violet trace is your circuit- as you can see, very very slow and it does not have enough swing to turn the MOSFETs off reliably- Vgs(th) can be as bad as 2V (time scale changed to show response of slow circuit).


enter image description here



You really want this circuit to switch rapidly or to insert some dead time- both MOSFETs will be one for a time when it is switching which causes shoot-through current.


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