Help with an ESC schematic

[joelsurfer]

Hi everyone! I need help with the following:
I want to design an ESC (for a three-phase brushless motor) and I am looking at a schematic that does not explain the reason for the use of switching cells in parallel. ESCs often have 6 MOSFETs of the same type, but this one has 12, 4 per phase (2 P-type above and two N-type below), with the switching cells in parallel as shown in the image. Does anyone really know why it does this? The boy says "For greater safety and to reduce the effort of the components, two elementary cells are placed in parallel for each phase of the motor." The only thing I can think of is that you implement it to divide the current that each MOSFET has to support.
Thanks for any possible answers!

 

[Martaine2005]

implement it to divide the current that each MOSFET has to support.

That is the main reason for having mosfets in parallel.

Martin

 

[Bluejets]

One would wonder why you would want to make your own as there are literally gazillions of them out there and at a far less cost than it would be for the bare mosfets.

 

[joelsurfer]

That is the main reason for having mosfets in parallel.

Martin

Thank you!! The thing is that I am doing my final year project at the university and I want to know if it would be appropriate to implement this circuit for a current of 30A (I know that to withstand that current, more powerful MOSFETs may be needed). I am attaching the final circuit with drivers on which we would base it, but what I don't know is if it would really be interesting to have those MOSFET cells in parallel or we could achieve it simply with one MOSFET cell per phase.

 

[Harald Kapp]

we could achieve it simply with one MOSFET cell per phase.

You can, provided you use suitably powerful MOSFETs and possibly cooling by a heatsink.

 

[Martaine2005]

There are considerations to be aware of when paralleling MOSFETs.
Have a read here.


Martin

 

[joelsurfer]

Well thanks to all but finally I´m using another circuit, can anyone help me with the schematic part of the BEMF voltage divider? Thanks. What do you think A0, A1, A2 and D6 are doing? I think that D6 detects when it´s a 0 crosing and A0, A1, A2 detect during all the time if they´re floating or if they are active phases. So then, knowing with phase is floating and knowing how the other two phases are, we can know wich is the next step sequence.