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Parallel FET Design

Parallel FET Design

Parallel FET Design


I am looking to create a circuit capable of handling a motor with a peak inrush current of 150-175 Amps and a continuous current of about 40 amps for a max of 10 seconds. I am using a micro-controller to turn the motor on and off which only has a 5V supply voltage. From what I read thus far I can achieve this level of current though a circuit outside of the micro-controller by placing MOSFETS in parallel. I was hoping that someone could shed some light on this topic seeing as how my EE skills are very amateur at best. Is this good practice, what are some of the things to look out for (balancing?), or are there better ways to do this? I appreciate the help.



RE: Parallel FET Design

FETs generally parallel quite well. If you are driving multiple devices or one large device then make sure your driver can sink and source enough current to charge / discharge the gate quickly so the device moves from a conducting to blocking state as quickly as possible. Your uP will not be able to do this without a buffer or driver stage.

RE: Parallel FET Design

Quote: 'capable of handling a motor with a peak inrush current of 150-175 Amps and a continuous current of about 40 amps'

You have not stated what kind of power this motor requires: a.c., a.c. three phase or d.c. so it would help to know these requirements. At the very least it would be best to have an opto-isolator interface to any external drive circuit to provide both voltage isolation and minimise interference from the motor circuit currents getting back into the micro controller.
Having said that, if it's a.c. powered then have you looked at some of the larger solid state switches? Some of these have large triacs which can switch the sort of currents you are looking at. It may also be possible to connect its optically isolated 'control' input directly to your micro controller without the need for further buffering via an auxiliary supply rail.

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