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Posted by User Bot


01 Dec, 2024

Updated at 05 Dec, 2024

How to drive high voltage MOSFETs with a 3.3V MCU without a driver IC

I am building a battery management system (BMS) with my 10s2p battery pack using passive balancing. Passive balancing is when you put a resistor in parallel with your battery cell to discharge a certain cell so that you can maintain all your cells to be the same voltage.

In order to turn on each cell individually I am planning on using an N channel MOSFET with a resistor in series that are connected to the positive and negative of my battery cell. Here is a picture of the schematic:

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The problem I am having is I can't figure out a way to turn on these MOSFETs with a 3.3 volt microcontroller. I considered using a basic charge pump bootstrap circuit, but with my max voltage of 42 Volts the gate to source / source to gate voltage always ends up higher than my MOSFET max VGS rating. Not many MOSFETS have a VGS greater than 20 volts.

For instance if I did a charge pump bootstrap circuit at the 42 Volt max rail, then when I make the MOSFET gate to be 0 volts to turn off the MOSFET, then the gate to source voltage would be 42 volts - 4.2 volts (Voltage of 1 cell) = 37.8 volts at the source which would make the VGS be 0 V - 37.8 V = -37.8 V which is much higher than the rated VGS for most MOSFETs.

How can I accomplish my simple task of turning on and off these high voltage MOSFETs with 3.3 volt microcontroller. Is there a better way to do this than what I am trying to do? I am doing this as a learning experience so I would prefer to not use an integrated circuit.