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A voltage regulated power supply consists of a full bridge rectifier feeding into a f

  1. Oct 25, 2011 #1
    1. The problem statement, all variables and given/known data

    A voltage regulated power supply consists of a full bridge rectifier feeding into a filter capacitor,
    and then into an NPN bipolar junction transistor (BJT) operating as an emitter follower, and
    with the base of the BJT biased using a resistor and a zener diode. The power supply is fed from
    a 240V (rms) 50Hz source, which is stepped down through a 15:1 transformer. The power
    supply must produce a +15V output for load currents up to 2A. The rectifier diodes have a
    forward voltage drop that is a constant 1.0V irrespective of the load current.
    a. Sketch the circuit arrangement for this type of voltage regulated power supply.
    b. Calculate the peak rectified voltage that appears across the filter capacitor.
    c. Select the zener breakdown voltage required to achieve the target regulated voltage.
    d. Choose an acceptable voltage ripple for the rectifier, and hence design the required bias
    resistor.
    e. Determine the maximum and minimum collector-emitter voltages for the BJT.
    f. Hence calculate the average power dissipated in the BJT.

    2. Relevant equations

    Vz=V°+0.7
    Iz*Rz + Ibe*Rz ≤ Vp - Vripple - Vz
    I(output current)= C * ( dv/dt )


    3. The attempt at a solution

    I took a photo of what I did so far ... :
    http://imageshack.us/photo/my-images/573/img00289201110260009.jpg/


    I'm not sure how I would solve this problem .. can you guys help me ?


    I was good with the sketch, I'm not sure about the rectified voltage and the BJT voltages required it to operate... I'm lost plz HELP!
     
    Last edited: Oct 25, 2011
  2. jcsd
  3. Oct 25, 2011 #2

    NascentOxygen

    User Avatar

    Staff: Mentor

    Re: A voltage regulated power supply consists of a full bridge rectifier feeding into

    It helps considerably if you have constructed & investigated such a power supply. I think it would be difficult if you haven't. Three is no substitute for hands-on practical lab work.
     
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