1.5 to 3.3 volts efficiency

Discussion in 'General Electronics Chat' started by zoom, Aug 2, 2015.

  1. zoom

    Thread Starter New Member

    Jul 11, 2014
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    I am not quite familiar with boost converters. So, I have some questions;

    Looking for this IC;
    http://www.electroschematics.com/wp-content/uploads/2015/01/MCP1640-datasheet.pdf

    It claims up to 96% efficiency.

    Now, assume I have a 1.5 Volts alkaline 3000mAh battery. If I use this battery with a boost converter to get steady 3.3 volts output, I will for sure not be getting 3000mAh spec anymore. How can I calculate the new capacity with 3.3 volts output ?
     
  2. dl324

    Distinguished Member

    Mar 30, 2015
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    Without external components, you'll only get 150mA with 1.5V in and 3.3V out; from page 3 of the datasheet.
     
  3. Bordodynov

    Active Member

    May 20, 2015
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    Csource=3000*(1.2V/3.3V)*90%=980mAH
     
  4. dl324

    Distinguished Member

    Mar 30, 2015
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    Efficiency takes a nose dive past 100mA, max input current limited to 800mA; will take external components to get above 150mA.

    From the datasheet:

    Efficiency
    33eff.jpg

    Current ratings
    33typI.jpg

    33dcChar_.jpg

    Vin=1.5V, Iout=200mA
    33maxI.jpg
     
    Last edited: Aug 3, 2015
  5. zoom

    Thread Starter New Member

    Jul 11, 2014
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    So, is the only thing I compromise is maximum current I get with the boosted 3.3 voltage ? Is my 3000mAh still there ?
     
  6. dl324

    Distinguished Member

    Mar 30, 2015
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    You can increase output current, but it will require external components to workaround limitations of the regulator.
    Most of it. The regulator will be operating closer to 80% efficiency with a 1.5V input and the battery will still have self discharge.
     
  7. Dr.killjoy

    Well-Known Member

    Apr 28, 2013
    1,190
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    With booster converter you have to remember the energy has to come from some where to make up the difference and it uses the current to make the difference in order for everything to work ..
     
  8. jjw

    Member

    Dec 24, 2013
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    31
    Look at post #3, you have about 1000 mAh from 3.3V output.
     
  9. dl324

    Distinguished Member

    Mar 30, 2015
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    You're neglecting the fact that efficiency with an input of approx 1.5V varies from 65-85% and that the regulator will not provide more than a couple hundred mA with 1.5V input/3.3V output.

    For this regulator, efficiency @ 1.2V in peaks at 85% @ 30mA and falls off rapidly @ 100mA. At max current supported by the regulator, efficiency falls to 65%.
     
  10. jjw

    Member

    Dec 24, 2013
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    I was not sure if op thinks he can get 3000mAh from 3.3V output, so just in rough figures 700 - 1000mAh from output depending on load current.
     
  11. dl324

    Distinguished Member

    Mar 30, 2015
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    Except that without external components, it's going to be closer to 200mA due to regulator limitations.
     
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