DC Power Supply

Discussion in 'Homework Help' started by Ahmed Zafar Khan, Feb 18, 2016.

  1. Ahmed Zafar Khan

    Thread Starter New Member

    Feb 18, 2016
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    I have designed a 5V ,350mA fixed power supply with a 12 Vrms step down transformer. the voltage across filtering capicitor should be almost peak value i.e 15V or 16V . but I am getting 12 volts acrossthe capacitor why is it so.
     
  2. AnalogKid

    Distinguished Member

    Aug 1, 2013
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    Schematic.

    Is the supply loaded at 350 mA when you are measuring the voltage?

    Schematic.

    What is the size of the filter capacitor?

    Schematic.

    ak
     
  3. Ahmed Zafar Khan

    Thread Starter New Member

    Feb 18, 2016
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    YES IT IS WHEN THE CIRCUIT IS LOADED .
    5500MICRO FARAD 25VOLTS

    Please answer it
     
    Last edited by a moderator: Feb 18, 2016
  4. Dodgydave

    Distinguished Member

    Jun 22, 2012
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    745
    POST YOUR CIRCUIT PLEASE.
     
  5. Ahmed Zafar Khan

    Thread Starter New Member

    Feb 18, 2016
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    image
     
  6. crutschow

    Expert

    Mar 14, 2008
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    We mean the schematic.
     
  7. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    Your question has been answered in the other forums.
     
  8. Ahmed Zafar Khan

    Thread Starter New Member

    Feb 18, 2016
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    MAY IT WORK
     
  9. Dodgydave

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    Jun 22, 2012
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    NO, you have resistors in series with the output supply, and the zener is pulling too much current through the resistors, i would use a lm7805 regulator instead of the resistors and zener.
     
  10. Ahmed Zafar Khan

    Thread Starter New Member

    Feb 18, 2016
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    SIR THIS IS OUR LAB PROJECT USING ZENER MY QUESTION IS WHY VOLTAGE DROPS ACROSS CAPACITOR THEORY BASED ANSWER NEEDED
     
  11. bertus

    Administrator

    Apr 5, 2008
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  12. ronv

    AAC Fanatic!

    Nov 12, 2008
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    The capacitor gets charged by the peaks only so the charge current is quite high. This makes the drop across the 1 ohm and the diodes higher than you think.
     
  13. WBahn

    Moderator

    Mar 31, 2012
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    What is the average current through the 15 Ω resistor between the cap and the zener?

    What fraction of the time do the diodes spend conducting?

    What is the average current through the 1 Ω resistor between the bridge and the cap?

    What is the average voltage drop across that 1 Ω resistor?
     
  14. WBahn

    Moderator

    Mar 31, 2012
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    Typing in all caps on a forum (or e-mail) is considered the equivalent of shouting and it is also considered quite rude. Please refrain from the practice (except, of course, when your intent is to shout and be rude).
     
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