Buck Converter 260-140

Discussion in 'The Projects Forum' started by Saxbel, Mar 31, 2013.

  1. Saxbel

    Thread Starter New Member

    Nov 29, 2011
    5
    0
    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 :)
     
  2. kubeek

    AAC Fanatic!

    Sep 20, 2005
    4,670
    804
    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.
     
  3. Saxbel

    Thread Starter New Member

    Nov 29, 2011
    5
    0
    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 ?
     
  4. Papabravo

    Expert

    Feb 24, 2006
    10,163
    1,796
    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.
     
  5. kubeek

    AAC Fanatic!

    Sep 20, 2005
    4,670
    804
    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.
     
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