Hello everybody,

I try to make a Buck converter from 260V DC to 140V 25A DC Maximum, in order to supply a motor. I have an idea to to the buck, but I've got a problem with the mosfet. I don't know how to choose it and I control it by a PWM signal by a PIC ==> How can I control the mosfet ? Driver maybe ?

If you help me, I will be very happy because I searched on Internet 2 weeks and I don't find it.

N.B. : Excuse me for my English, I'm Belgian

 

I seriously doubt that you can do a 3500W simple buck converter. Even if the mosfet took just 5% of the overall power as a loss, it is 175W dissipation, and the overall losses will probably be much much more. I doubt that even mutliple paralleled bucks running multiple phase will be able to cut it, you would need like 20 in parallel.
I´d say such power calls for fullbridge configuration which means you will have to design the transformer. Or maybe even multiple transformers.

 

Thank you, but I will drive a motor with that from 0 to 140 V and I don't often go to 25 A. But if I do a buck, how can I choose the mofset and how can I drive it ?

 

DC-DC converters are good for constant loads. They are poor performers when it comes to load transients required by motors. I feel that you should avoid wasting your time on this quest because a motor that requires even 10A to run may require 40A to 50A on startup. I predict that the first time you try this with a real motor the supply will fall to its knees and it won't bother to stop there.

 

No single mosfet will be able to withstand what you want. You will need a bank of at least 10 switching devices to drive such motor. What is it´s stall current? That is the most important spec.