12 volt dc power supply

Discussion in 'The Projects Forum' started by dane, Jan 31, 2009.

  1. dane

    Thread Starter New Member

    Jan 31, 2009
    3
    0
    am building a 12 volt dc power supply with the following specifications:


    output power- 1 watt

    output voltage- 12volt

    output current- 1amp

    ripple factor- <1%


    i need the formulas to calculate capacitance, diode, transformers and other components. i didnt get any values for the components thats why i need the formulas. plz help

    thank you!
     
  2. bertus

    Administrator

    Apr 5, 2008
    15,649
    2,348
    Hello,

    Your caculation for the power is wrong.
    A 12 Volts power supply that can deliver 1 A has a power of 12 Volts X 1 Ampere = 12 Watts.

    Here is a simple power supply schematic from bill bowdens webpage with a LM 317.
    It is capable of 1.5 Ampere.
    http://ourworld.compuserve.com/homepages/Bill_Bowden/page12.htm

    Greetings,
    Bertus
     
  3. dane

    Thread Starter New Member

    Jan 31, 2009
    3
    0
    that site is no help. sorry about that yes it it is 12 watts
     
  4. mik3

    Senior Member

    Feb 4, 2008
    4,846
    63
    Is this a school assignment or a personal project?
    If it is a personal project you can use a LM7812 to regulate the output voltage.
     
  5. bertus

    Administrator

    Apr 5, 2008
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  6. dane

    Thread Starter New Member

    Jan 31, 2009
    3
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    yes it is a school assignment
     
  7. mik3

    Senior Member

    Feb 4, 2008
    4,846
    63
    These equations were derived by assuming the ripple voltage as a triangular wave and give approximations of the actual values.

    Vr=Idc/(2*f*C)

    Vr=ripple voltage peak-peak
    Idc=DC current through the load
    f=supply frequency
    C=filter capacitance

    k=Vrms/Vdc

    k=ripple factor
    Vrms=Vr/(2*sqrt3) rms ripple voltage
    Vdc=DC voltage across the load

    Vdc=1/{1+1/[4*f*C*R]}

    Vdc=DC voltage across the load
    C=filter capacitance
    f=supply frequency
    R=load resistance
     
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