I am currently working on some hobby project. I have a 24V 2A DC motor that I want to drive. I designed a board with a designated IC on it to drive the motor, it wirked just fine. But then I thought that I would try to design my own H-bridge motor driver so that I am not bound by the parameters of the IC (current limit of 4A, it gets overheated easily, etc.)
So my question is: is this a good H-bridge design?
I am not looking for a 3 pin design, so my question is not regarding that. I want a 4 pin H-bridge, where I can control each pin with an MCU. I have seen some designs over the internet, nearly all of them agree on the N-channel MOSFET on the low side, and the P-channel MOSFET on the high side, with the flyback diodes parallel to each MOSFET.
But what about the BJT? Is it a good idea to drive the P-MOSFET through BJTs? Let's assume an STM32 3.3V MCU as the control unit, the pins that you can see here are directly connected to the GPIO pins of the MCU. Are the resistors of the correct value?
As I understand, R15 and R42 are "used" as current limiting resistors, but there is not so much current flowing that way, so small values like a 100ohm or 1k is okay?
R31 and R40 are pull down resistors, they need a high value like 10k, 100k to have only a small current there?
R17 and R22 are pull-up resistors when the BJT is off, same large values as the previous pull-down resistors?
I guess that R1 and R39 also limit the current, but I have no idea what is a good size there.
What else should I pay attention to? I guess I should choose P channel transistors that can handle high currents and high voltages, also the 24V gate voltage. N channel MOSFETs to be able to handle large currents. And what about the BJT? How do I choose that one?
So yeah, alltogether my question is: is this a good circuit, will it work, how to choose resistor sizes and BJT?
Based on the comments that I got (thank you very much), I re-designed the schematic:
The low-side PWM was a good suggestion, I did not think about that. I reduced the pull-down resistor sizes to make the switching faster. Based on an other very useful comment, I introduced a 15V zener diode to both sides to protect my MOSFET's gate from over-voltage. I also replaced the BJT with the exact same N-MOSFET switch that I use on the low side.
I did not get the boost-capacitor thing though :(
What do you think now?