12VDC to 1.5V-13V power supply

Discussion in 'The Projects Forum' started by BruceMellen, Oct 1, 2011.

  1. BruceMellen

    Thread Starter New Member

    Jun 25, 2011
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    Part of a hobby project…I want to design/put together a number of small/inexpensive relatively efficient off/1.5V-13VDC variable voltage power supplies that can drive 0.6W to 18W rated (30W LRA) brushless motors from a PWM source (to vary the voltage), using only 12VDC as the input power source.

    Can someone give me some search clues/keywords, as I’m not yet coming up with anything relatively clear here/online. I’ve already looked at a relatively simple buck approach w/driver, higher bias, & N-channel MOSFET, and that meets most needs except that it seems to only take me up to about 11.6VDC.
    ...not an EE
     
  2. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    If your input supply voltage is 12v and you want 1.5v-13v out, then you will need more than PWM or a BUCK supply. To get that wide of a range, you'll need something more like a buck-boost, SEPIC or CUK.

    Have a look at this page to get an idea of different topologies:
    http://www.smps.us/topologies.html

    Since your input is low voltage, you can use the non-isolated topologies - unless you really want to use a buck-boost, and you need the grounds to be common; as the buck-boost is an inverting topology.
     
  3. iONic

    AAC Fanatic!

    Nov 16, 2007
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    Do you want this variable supply to vary the voltage to the motors or do you want PWM to vary the average voltage to the motors? Or do you want some odd combination of both for some reason?
     
  4. SgtWookie

    Expert

    Jul 17, 2007
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    iONic,
    From the OP's problem statement, they want to use a 12v supply to provide anywhere from 1.5v to 13v to their motor. Plain PWM isn't going to work. They're going to need a buck-boost, SEPIC or CUK supply - except at low voltage, they may need to go with PWM to overcome motor stiction.
     
  5. iONic

    AAC Fanatic!

    Nov 16, 2007
    1,420
    68
    I'm not exactly convinced of your assessment. Some of the confusion lies in the nomenclature used in the OPs description.

    I was reading "off/1.5V-13VDC" as the range of the avg voltage of a PWM circuit, 13V being a slightly high version of a 12V LA Batt. Why the OP would need 13V is not clear as I have not come across a 13V motor.

    So, until the OP comes back with some additional information or to at least debunk your's or my assessment I am open for either interpretation.
     
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