Voltage controlled constant AC current source

Discussion in 'General Electronics Chat' started by NittuThakur, Dec 21, 2010.

  1. NittuThakur

    Thread Starter New Member

    Aug 23, 2010
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    Hi :cool:
    I am designing a voltage controlled constant AC current source of 5 mA, and it is capable for supplying current up to 10 -500 ohm resistance range but my requirement is 1 - 20,000 ohms. can any one provide me the idea how to proceed.
     
  2. t_n_k

    AAC Fanatic!

    Mar 6, 2009
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    There are high voltage current regulators around.

    Not sure if this type can be configured as an ac source .....

    IXYS also produce AC (non switchable) type current regulators

    http://www.ixys.com/

    Do a part search on the site with the term "IXC" and you get a complete listing.
     
    Last edited: Dec 21, 2010
  3. NittuThakur

    Thread Starter New Member

    Aug 23, 2010
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    My requirement is maintain constant current as the load varies from 1 to 20k at 20 hz frequency.
     
  4. t_n_k

    AAC Fanatic!

    Mar 6, 2009
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    The reason I mentioned the high voltage current regulators is that at 20kΩ load and 5mA (rms?) the load voltage requirement would be 100V (rms). So this is a high voltage application - which presents some design challenges. Also because it is an ac source that also complicates matters.

    Another option might be a pwm inverter circuit with some load filtering to minimize harmonics. An isolation transformer with secondary side current feedback might be a useful option.

    Does the 20Hz AC have to be a sine wave or would a square wave suffice? Your design specs are rather non-specific.
     
    NittuThakur likes this.
  5. blueroomelectronics

    AAC Fanatic!

    Jul 22, 2007
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    What is it for?
     
  6. NittuThakur

    Thread Starter New Member

    Aug 23, 2010
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    this is my assignment to design a AC constant current source. which is capable to supply constant current of 1 ohm to 20k. In my circuit I used instrumentation amplifier in the feedback circuit.
     
  7. t_n_k

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    Mar 6, 2009
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    I was interested in pursuing the PWM inverter "solution" to the problem.

    I've attached a general feedback control schematic diagram which I have tested as a simulation. Seemed to work OK. So the solution is achievable but wouldn't be simple or cheap.
     
  8. NittuThakur

    Thread Starter New Member

    Aug 23, 2010
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    it seems to be quit complicated and quit costly circuit. I am trying to send my circuit to you, but due to larger size, unable to upload the circuit. can you plz send me your email id so that I can send you my circuit.
     
  9. t_n_k

    AAC Fanatic!

    Mar 6, 2009
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    This is something other forum members would probably also like to view and discuss.

    What image format or file format are you trying to upload? How big is it?

    If you have access to a scanner you can upload scanned files quite easily. If you are trying to upload a big image file then try re-sampling it to a smaller size before sending. Sometimes it can take some time to upload a file if the server is slow.
     
  10. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
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    If you can use pdf or zip for your file, both have 5 MB limits.

    John
     
  11. NittuThakur

    Thread Starter New Member

    Aug 23, 2010
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    Here I have attach the zip file. see it and suggest how I can draw 5 mA through the range 1 ohm to 20k resistance range.
     
  12. t_n_k

    AAC Fanatic!

    Mar 6, 2009
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    You should also post a table or listing of the circuit values, amplifier component types and supply voltages, etc. Is the input control source a sinusoidal 20Hz?

    1Ω to 20kΩ is quite a substantial dynamic load range.
     
  13. NittuThakur

    Thread Starter New Member

    Aug 23, 2010
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    Yes the input source is sinusoidal 20 Hz. supplying from the function generator.
     
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