Increase current for 10V output having 5V power source

Discussion in 'General Electronics Chat' started by palkapalka, Aug 15, 2015.

  1. palkapalka

    Thread Starter New Member

    Aug 15, 2015
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    Hi,

    I have output of 10V with low current. I also have power source of 5V with 500mA current (USB).
    How can I combine these things to get 10V with high current?
    I thought about buffer opamp - but output will be limeted to rails voltage (5V).
    I do not want to use additional step-up converters.
     
  2. dl324

    Distinguished Member

    Mar 30, 2015
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    Can't be done. Even if you use a step-up converter, you'll get less than a couple hundred mA at 10V. Additionally, you can't draw more than 100mA from a USB port unless you negotiate with the host and are allowed a higher current.
     
  3. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    The best you can do is about 200mA @ 10V, and that is only by using a step up converter.

    I never cease to be amazed at why folks want to steal power from a USB port when these things are almost free at thrift shops and garage sales.
     
    #12 likes this.
  4. #12

    Expert

    Nov 30, 2010
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    I think we're having a problem with the definition of, "step-up converter". What else could increase the voltage of a 5VDC source? Until DC transformers are invented, you are stuck with making some sort of a converter.
     
  5. palkapalka

    Thread Starter New Member

    Aug 15, 2015
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    Thank for the prompt response.
    200 mA limit I understand.
    Can I boost 10V signal to say 50mA?
    The only reason I do not want step-up converters is to avoid additional coils in my schematic.
     
  6. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    We don't know..
    Where is the 10V "signal" coming from?
    Whats its source?
     
  7. palkapalka

    Thread Starter New Member

    Aug 15, 2015
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    I use voltage doubler to get 10V from 5V usb - but it drops current. And I want my usb current back - at least portion of it.
     
  8. #12

    Expert

    Nov 30, 2010
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    This might work.
     
  9. palkapalka

    Thread Starter New Member

    Aug 15, 2015
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    Thank #12.
    I will consider this ic
     
  10. dl324

    Distinguished Member

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    It still requires an inductor.
     
  11. #12

    Expert

    Nov 30, 2010
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    If you don't like inductors, you are welcome to name a switched capacitor converter for this job...or any other method.

    Perhaps a 555 used as an oscillator with a voltage doubler rectifier configuration?
     
  12. palkapalka

    Thread Starter New Member

    Aug 15, 2015
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    Is this what you mean: http://www.instructables.com/id/555-Voltage-Doubler/
    It says - "This circuit is only practical for low current devises".
    But "low" current is different for different applications.
    What current can I get from this circuit?
     
  13. #12

    Expert

    Nov 30, 2010
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    The comments on that page show this:

    "my multimeter showed 18v@ 0.20A on the 10A setting, while using the circuit to power my 80mm 3-wire pc case fan at the Vin pin of the 555ic chip. i had 14v @ 0.14A from Vout to the pc fan."
     
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