Charge Pump

Discussion in 'The Projects Forum' started by falconite, Nov 6, 2010.

  1. falconite

    Thread Starter New Member

    Nov 6, 2010
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    Hello...I am trying to implement a system(for the time being on paper) whereby i have a dc voltage source of 2V, and i have to generate dc voltages of 2V,4V,6V...20V to charge capacitors....i also have a clock signal of 2V(peak-to-peak)...now i may multiply the 2V using a charge pump IC....but it can only be multiplied upto 8 V right????(current available is negligibly small at this stage itself)....Is there any way to generate voltages as high as 20V????
     
  2. Audioguru

    New Member

    Dec 20, 2007
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    I already answered your questions on the other website.
     
  3. hgmjr

    Moderator

    Jan 28, 2005
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    We at AAC don't mind if you want to post your question here to get other suggestions.

    hgmjr
     
  4. hgmjr

    Moderator

    Jan 28, 2005
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    Sounds like you may want to look into boost type DC to DC converter.

    One thing to keep in mind is that you can't get more power out of the DC-to-DC converter than you put in.

    For example, if you boost the voltage from 2V to 10V, you will only be able to get 20% of the current that you put in. Actually you will get slightly less than that since some power is consumed by the voltage regulation circuitry.


    hgmjr
     
  5. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    Please do not wirte everything in one line.
    This makes it hard to read.

    Take a look at this thread:
    http://forum.allaboutcircuits.com/showthread.php?t=43859

    See post #15 for the multiplier circuit.

    Bertus
     
  6. Audioguru

    New Member

    Dec 20, 2007
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    The input voltage is only 2.0V!
    A 555 and voltage multiplier made with diodes won't work with such a low supply voltage.
    Two ICL7660 charge pump ICs can be cascaded to make 8V at almost no current which is not enough current to power a 555 voltage multiplier. 20V is much too high for an ICL7660A charge pump IC.

    Maybe the 8V can power a Cmos 555 voltage multiplier circuit.
     
  7. falconite

    Thread Starter New Member

    Nov 6, 2010
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    @Audioguru....
    I posted this question over here as well coz this seems to be a dedicated site for circuits,while the previous one was for electronics/electrical in general....i did go thru ur posts over there...no offence plz...:)
    @bertus...
    point noted.....
     
  8. falconite

    Thread Starter New Member

    Nov 6, 2010
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    @hgmjr....
    ya a bit of power will b wasted...but thts ok i guess....moreover i need the o/p current to charge the capacitor...so evn if the current is low the capactrs will get charged eventually.....
     
  9. hgmjr

    Moderator

    Jan 28, 2005
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    Can you describe you application in more detail?

    hgmjr
     
  10. falconite

    Thread Starter New Member

    Nov 6, 2010
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    Okkk heres the problem....it actually consists of 2 stages...
    I am concerned wth the frst stage for the tym being...

    I have 10 capacitors (same value,no particular value mentioned)....
    I have to charge the first to 2V, the 2nd to 4V, and so on,in an AP series,upto 20V for the final one...

    I have a 2V power supply and a clock of 2 V peak-to-peak....

    I was initially thinking of connecting 4 voltage doubler IC s in cascade...
    but audioguru mentioned that i would get negligible current from the 2nd IC itself....
    so theres no question of cascading 4 ICs....
     
  11. Kermit2

    AAC Fanatic!

    Feb 5, 2010
    3,779
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    Cheat and use a transformer. use the clock to PWM a switch that sends the 2volts through a coil. Wind another coil to give you a higher voltage and use that to charge your caps. Or just send the clock to a step up transformer and use that to charge the caps. 2v clock into a 5 volt secondary should give you more than 20 volts out on the primary side, but only a few micro amps to work with.
     
  12. Audioguru

    New Member

    Dec 20, 2007
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    Before you had only a 2.0V power supply. Now you also have a clock signal that is 2V p-p. It might be able to drive a voltage multiplier that uses diodes.
    How much is its output current?

    The datasheet for the ICL7660 charge pump IC shows how to connect them for double the voltage and how to cascade them for doubling again so the output voltage is 4 times (at a very low current).
    The datasheet also shows how to parallel them for double the current.
    Then if you use enough of them then you will get close to 8V at a low but useable current.
     
  13. falconite

    Thread Starter New Member

    Nov 6, 2010
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    @Kermit2....
    actually i did think about using the clock and transformer once....:D
    @Audioguru...
    i had the clock from the beginning...didnt thnk it wud b reqd....
    actually i am thinking of using a SIPO regiester for the 2nd stage....
    so the clock wud b reqd ovr thr.....n i dnt thnk i shud be using it for any other purpose cept for synchronization purposes....
     
  14. Audioguru

    New Member

    Dec 20, 2007
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    Please type in full English words.

    We can't help you unless you tell us how much AC and DC current is available for the input. Maybe there is not enough input current to make a voltage stepup circuit.
     
  15. falconite

    Thread Starter New Member

    Nov 6, 2010
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    Okk...the problem is nothing has been mentioned about the currents....
    Only the voltages have been mentioned....
    I guess we may assume the DC voltage source can provide as much current as required....
    and that the FINAL o/p current may be negligibly small, as long as it is sufficient to charge the capacitor (upto as high as 20V).....
    Even the frequency of the AC source hasnt been mentioned....
     
  16. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    Please use full english and not everything on one line.
    Also a schematic of the circuit you have upto now would help.
    That way we can have a look at it and give ideas how to improve it.

    Bertus
     
  17. retched

    AAC Fanatic!

    Dec 5, 2009
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    I am guessing you are using a cellphone to access the forum?

    It can be quite difficult to format your posts in a legible way, but do keep it in mind. It helps take you seriously and that leads to more, quality responses.

    Dont be scared off, just some helpful tips to get you the help you need. ;)
     
  18. falconite

    Thread Starter New Member

    Nov 6, 2010
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    @retched....

    Actually i am accessing the site from my home PC.
    Its just that this is the way i usually type,so its taking a bit of time being gramatically correct.:D
    I do see your point.Hope this post i ok. :)

    @bertus....

    I am working on the circuit.
    One schematic coming up.

    @Audioguru....

    Sorry i cant be more specific about the problem parameters.
    This is all the information that has been supplied.
     
  19. Audioguru

    New Member

    Dec 20, 2007
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    I have never needed and never used a charge pump IC so the ICL7660 and ICL7660A are the only ones I know. Research the manufacturers to see if they make a better more suitable one. Maybe Maxim has one.

    There is an IC called an Energy Harvesting IC (look in Google) that takes a very small charge from a piezo disc that is in your shoe which is produced with each step when walking. It boosts the voltage. It ends up charging a capacitor which charges a cell phone battery.
     
  20. falconite

    Thread Starter New Member

    Nov 6, 2010
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    I was going through the data sheets of some charge pump ICs on the net.
    None of them seem satisfactory enough to generate a voltage of 20V from 2V

    Can i build a Dickson charge pump of 10 stages using capacitors and MOSFETs, as given in the figure???

    There are a couple of issues.

    1. I will never get an o/p voltage of 20V due to the voltage drop across the FETs.
    But will the o/p voltage be a close approximation??
    What sort of FET may i use to minimize this voltage drop???

    2.There would be a good amount of ripple in the o/p voltage.
    Can this problem be solved using a zener voltage regulator???

    3. The given clock has an amplitude of 1 V, while the last MOSFET would require something around 20 V.
    Can i use a transformer to step up the clock voltage 20 times???
    Will the clock signal get heavily distorted in that case???
     
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