Boost regulator question

Discussion in 'General Electronics Chat' started by MattQ87, Apr 8, 2011.

  1. MattQ87

    Thread Starter New Member

    Apr 5, 2011
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    0
    So, I designed a boost regulator in LTSpice based on the LT3757 boost regulator. I'm using a 100uH inductor, MBRS130LT3G diode, FQT7N10 MOSFET, a 1000uF cap, and everything else matches with the datasheet for LT3757. It works great in LTSpice, but the actual circuit isn't giving me anything above the input voltage (12 Volts), and it should be producing about 24. Advice? I'm pretty new to boost regulators, any advice on how to debug the circuit? I notice that the gate voltage output of the LT3757 is a constant ~.6V, so the inductor isn't even switching.

    LT3757 http://cds.linear.com/docs/Datasheet/3757fb.pdf
    MBRS130LT3G: http://www.onsemi.com/pub_link/Collateral/MBRS130LT3-D.PDF
    FQT7N10: http://www.fairchildsemi.com/ds/FQ/FQT7N10.pdf
     
  2. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    You need to post an image of your circuit, and the LTSpice .asc file - or you're not going to get much input.

    You should also post your layout of the circuit, and a photo if possible. If you're trying to run it from a breadboard, then that's a problem - you won't get good results.
     
  3. MattQ87

    Thread Starter New Member

    Apr 5, 2011
    13
    0
    Fair enough. I've included the boost part of the circuit I'm working on. The board definitely needs to be tidied up a lot, but just for testing purposes, I was hoping to get a voltage above 12V (as opposed to 28, which I'm trying to get right now), but as I mentioned, its not even switching the FET. I really appreciate all the help!
     
  4. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    OK, what are the .brd and .sch attachments? I can't read Cadsoft Eagle above 4.16R2.
    If you can export them as .PNG files (portable network graphics) then anyone can view them without special software.

    You're also going to need to give details about the parts you installed. For example, L1's DC current in the simulation (even if the STARTUP option is removed) is nearly 11 Amperes. With the STARTUP option, it's much more.
     
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