Power supply

Discussion in 'The Projects Forum' started by dharanir.26, Oct 11, 2011.

  1. dharanir.26

    Thread Starter New Member

    Oct 11, 2011
    3
    0
    Hi,
    I have designed the simple power supply circuit for 24V/2A.and i simulated the circuit using NI Multisim.The circuit is working fine.But when i was testing practically with the load the output voltage is decreasing.
     
  2. crutschow

    Expert

    Mar 14, 2008
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    3,220
    That's interesting.....
     
  3. t_n_k

    AAC Fanatic!

    Mar 6, 2009
    5,448
    782
    Presumably it's a simple unregulated supply. If so, then it's not surprising this happens. Any practical unregulated DC supply will suffer from regulation issues as the load varies.
     
  4. dharanir.26

    Thread Starter New Member

    Oct 11, 2011
    3
    0
    When i am connecting the load of 24E,The DC output is coming down to 20VDC and across the transformer output terminals voltage also coming down.But the transformer is rated as it is capable of giving 2A.
     
  5. ashokcp

    Active Member

    Mar 8, 2007
    50
    2
    Transformer load regulation! The parameters for the transformer model you have used, may have been simplified.
     
  6. SgtWookie

    Expert

    Jul 17, 2007
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    Until you start posting images of your simulation schematic, there is not much we can do for you except to say "Your circuit is broken. Post a schematic."
     
  7. dharanir.26

    Thread Starter New Member

    Oct 11, 2011
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    Here is the circuit attached what i have tested and also tried with the 7815 regulator. Even though the during load regulation the output is decreasing to 8V and load current is 1A.
     
  8. SgtWookie

    Expert

    Jul 17, 2007
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    If your input is really 20VAC, then the peak-to-peak voltage will be ~28.3v, and at the rated source load, you should see around 24.5v average on the cap C3.
    You show R1 as 11 Ohms. To get 1A current through R1 will require 11v. If you were trying to output 15v, there would be 1.363.. Amperes current flowing through R1.

    With only 8v at the output, current flow through R1 would be 0.727... Amperes.

    If you did not have a really large heat sink on the 7815, it would shut down due to excess power dissipation in the regulator.
     
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