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Boost converter current calculation

Discussion in 'General Electronics Discussion' started by BlackMelon, Aug 21, 2014.

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  1. BlackMelon

    BlackMelon

    188
    5
    Aug 7, 2012
    Hello there!

    I'm designing a boost converter by using this book:

    http://www.mediafire.com/view/00awc...tronics_-_D._Hart_(McGraw-Hill,_2010)_BBS.pdf

    From Example 6-4 of page 216, I want to calculate an inductor current but my load resistance is only 1 ohms (since I want the circuit to be able to supply 12V 12A dc motor from a 1.5V battery). The result that I've got is 123.45A of inductor current. My questions are..

    1) Did I make any mistakes?
    2) If not, do I need a very very large wire to withstand the current?


    Thank you
    BlackMelon
     
  2. OLIVE2222

    OLIVE2222

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    25
    Oct 2, 2011
    for the inductor Inom = (Uout/Uin)* Iout, so rawly 100A
    do yo really expect to supply the motor from a 1.5v cell?
     
  3. BlackMelon

    BlackMelon

    188
    5
    Aug 7, 2012
    Yeah, I think may be 2-3 cells in parallel might be lighter than a 12V battery...

    So how to deal with the current? It's kind of massive >_<
     
  4. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,482
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    Jan 21, 2010
    Get a large 2V lead acid battery.

    It will need to be somewhat larger than a 12V battery used to power the same load due to the inefficiencies of the boost converter and higher I²R losses.
     
  5. OLIVE2222

    OLIVE2222

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    Oct 2, 2011
    definitively the better way to drive a 12V motor is a 12V battery , you must have very good reason to don't do it so.
     
  6. BobK

    BobK

    7,682
    1,688
    Jan 5, 2010
    For the same chemistry, the same weight of battery will provide roughly the same amount of power no matter what the voltage is. So adding a boost converter (which, in this case would be heavy because of the massive inductor you would need), does not help at all. Use a 12V battery.

    Bob
     
  7. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

    8,393
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    Nov 28, 2011
    Of course he does! Why not?

    newbattery.jpg
     
    BlackMelon and OLIVE2222 like this.
  8. OLIVE2222

    OLIVE2222

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    Oct 2, 2011
    That's cool thank you Kris, may I ask you the battery Digi-key part number? ;)
     
  9. BobK

    BobK

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    1,688
    Jan 5, 2010
    Damn, I just looked it up in Digikey and they only sell in QTY 1000.

    Bob
     
    Arouse1973 likes this.
  10. BlackMelon

    BlackMelon

    188
    5
    Aug 7, 2012
    My idea just collapsed!!! lol, 14.8V or 11.1V LiPO might be the best solution :D

    PS: If I want to drive 12V DC Motor with 14.8V, can I just control the maximum duty cycle of a motor driver board to be less than 12/14.8?

    Thank you everyone
     
  11. Arouse1973

    Arouse1973 Adam

    5,165
    1,087
    Dec 18, 2013
    Oh Kris you do make me laugh PSML :)
    Love it
    Adam
     
  12. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

    8,393
    1,271
    Nov 28, 2011
    You get the battery free when you buy the truck!
     
    Arouse1973 likes this.
  13. OLIVE2222

    OLIVE2222

    690
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    Oct 2, 2011
    14.8 for a 12V motor will probably not be a problem, but yes if you have a driver board you can adapt the duty cycle accordingly.
    Whta's your battery capacity?
     
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