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How to amplify a DC voltage

  1. Oct 2, 2013 #1
    Hi, a newb on eleng here.

    Recently i've been working on my project. I need to get a high DC (1000V - 10000V ) output voltage, low current (10-30mA would be fine) from a DC input voltage (9-12V). I'm thinking to use a transformer but it only able to amplify an AC voltage right?

    Thanks!
     
  2. jcsd
  3. Oct 2, 2013 #2

    meBigGuy

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    30ma @ 10,000 volts is pretty deadly. And, it's 300 watts to boot.

    You need a switching power supply utilizing one heck of a transformer. One heck of a switcher, too.

    For example, if 100% efficient, 30ma @10000 volts is the same power as 30 amps at 10 volts.

    Are your initial specs real?
     
  4. Oct 2, 2013 #3

    Simon Bridge

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    10A 240V (rms) is the NZ domestic supply.
    One way would be to build a PSU specifically for the project ... but the answer to the question is that transformers can "amplify" DC voltages too.

    I agree with meBigGuy's concerns. The 20-30mA current sounds like a guesstimate. Considering the danger - calculate it. How small can you have the current? What are you trying to do?
     
  5. Oct 3, 2013 #4
    Well, maybe 10kV is too high, i will lower the specs then. Infact, it's okay for the amp to go lower than 10mA.

    How can we use this transformer to "amplify" the DC voltage?
     
  6. Oct 3, 2013 #5

    Simon Bridge

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  7. Oct 3, 2013 #6
    Thank you very much sir! :)
     
  8. Oct 3, 2013 #7

    berkeman

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    You say you are new to electronics. What exactly are you wanting to do with this high voltage? What do you know about creepage and clearance requirements when working with high voltages?
     
  9. Oct 3, 2013 #8

    Simon Bridge

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    I share these concerns.

    Variable, gut-reaction specs and an unwillingness to say what you want this for generally raise concerns. If you let us in on it we can help you avoid some of the hazards involved - they are not always obvious. It is certainly best practice for us to at least attempt to make sure of your knowledge. Maybe it's all fine and we are worrying for nothing?
     
  10. Oct 3, 2013 #9
    Actually it's nothing really, my teacher told us to do a project that amplify a low DC voltage to higher one. Well he didn't told us to make it into 10kV though, i was just wandering IF i want to be that high, what should i do.
    anyway thanks for your concerns guys :)
     
  11. Oct 3, 2013 #10

    Bobbywhy

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    Transformers do not amplify DC voltages. Have you tried a "Google" search for "DC Amplifier". There are thousands of them.

    If you are serious about building a HIGH VOLTAGE supply, you can do so safely by learning the basics of "switchmode power supplies for HVDC". You can also purchase small, sealed packages that use low voltage inputs and give you kilovolts out. Just learn to use Google search to find what you want.
     
  12. Oct 4, 2013 #11

    Simon Bridge

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    Well that's extremely open ended but it is almost certain that your teacher does not intend the kid of high-power application you are thinking of. In fact, it may even be against the law.

    You want to end up with a box which takes a few volts in and puts a few more out or what?
    You should get a clarification on that from your teacher.

    Look up "DC amplifier".

    If you want to have fun, there's always building a van-der-Graaf generator ... it's the sort of thing I did at High School level but things have changed since then and it may be against some sort of regs. Check.

    It could just be a second PSU ...

    You can use a transformer as part of a project that steps-up a DC voltage, but a transformer by itself won't do that.
     
  13. Oct 4, 2013 #12
    yes something like that and a low amps too
     
  14. Oct 4, 2013 #13

    Simon Bridge

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    Yep - so are you given an input and a target output?
    Can you have an extra power lead into the box or does it have to be driven entirely off the input voltage?

    It sounds like what you really need is help narrowing down a very open-ended assignment.
    If I know the parameters I can do that really fast.
     
  15. Oct 4, 2013 #14
    the input would be from a DC battery, 9v to be exact.
    Sorry but what do you mean by that? if i'm not mistaken understanding your question, i think yes i can, the power output doesn't really matter

    yes, it seems like that :)
     
  16. Oct 5, 2013 #15

    Simon Bridge

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    Have an extra power lead into the box?
    I mean - connected to another voltage source. I mean: if your box could have another 9V battery in it, you can easily turn a 9V input to a 18V output right?
     
  17. Oct 5, 2013 #16

    berkeman

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    Then don't think about large voltage multiplications right now, since you do not yet have the skills to understand how to handle high voltages safely.

    Instead, focus on DC voltage doubling (Google is your friend), or DC voltage boost DC-DC converters (Google is your friend).

    :smile:
     
  18. Oct 5, 2013 #17

    meBigGuy

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    The question is whether you want an amplifier (take a low dc voltage and amplify it to a higher one, which requires a separate power supply at the higher voltage) or a DC-DC boost converter power supply, which takes a DC voltage and creates a higher DC voltage from it alone (without a separate higher voltage) (essentially a DC transformer, but complex).

    Google or wikipedia "boost converter" to see if that is what you want.
     
  19. Oct 5, 2013 #18
    No i can't put another battery. Only 1 of them.

    I've read about Boost Converter, but i don't really understand how it works. Can someone give me a simple schematic or an example on how it's work?
     
  20. Oct 5, 2013 #19

    meBigGuy

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    Read the wikipedia artilcle on "boost converter". In the "operating principle" section, read (a) and (b) over and over until you understand what they are saying. If you can't get it. look at a few more examples. If you are still stuck, post your questions.

    The single inductor boost converter described above is 1 approach to DC to DC conversion. You can also use a transformer based architecture. You essentially switch the DC (essentially creating AC), go through the transformer, and rectify back to DC. http://www.electroniq.net/power-supply/dc-dc-converters/low-power-variable-voltage-converter.html is one simple example.

    EDIT: This is a better tutorial:
    http://www.maximintegrated.com/app-notes/index.mvp/id/2031
    Here is a more advanced tutorial. http://www.maximintegrated.com/app-notes/index.mvp/id/1109
     
  21. Oct 5, 2013 #20

    Simon Bridge

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    Good. That's a restriction you didn't mention :)
    Any others now you know what sort of thing to look for?

    You seem to be settling on a boost-converter though. Enjoy.
    If you are having trouble understanding it, that may be because you are expected to use information from your classes to date. (Which would be another restriction.)

    If you have covered electric motors, electric generation, and transformers, then you have a likely candidate that fits the bill.
     
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