How to calculate Load Regulation

Discussion in 'Homework Help' started by jegues, Mar 17, 2011.

  1. jegues

    Thread Starter Well-Known Member

    Sep 13, 2010
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    How would I go about calculating the Load Regulation in this circuit? Note that we don't know the value of RL.

    After doing some wiki'ing, I have to find the Voltage(Full Load), where IL = 20mA, and Voltage(Min. Load), where IL = 0mA.

    I have done this correctly?

    Also if I calculate a load regulation of 84% does that mean that the output changes by 84% or that it regulates 84% of the output?

    See figure attached for my attempt and question statement.

    EDIT: Also, for part e), how do I calculate the maxmimum power dissipation if I've solved for the maximum current?
     
    Last edited: Mar 17, 2011
  2. jegues

    Thread Starter Well-Known Member

    Sep 13, 2010
    735
    43
    I'm pretty what I've got in my OP is incorrect.

    Here's my 2nd shot at it. Am I on the right track?

    What would IL be for no load? Is it modeled as a short circuit or an open circuit? If I know this I can find IL.

    Also, what do they mean by full load condition?

    Thanks again!
     
  3. Jony130

    AAC Fanatic!

    Feb 17, 2009
    3,957
    1,097
    No load = 0A for lad current.
    All current provides provided by R flow through Zener diode
    load current is equal 20mA.

    R = (15V - 9.825V)/ ( 25mA ) - 7Ω = 200Ω

    ΔVo = rz/(rz+R) * ΔVs = ± 169mV

    Output impedance is equal

    Rout = R||rz = 6.7632Ω ≈ 7Ω

    Load regulation
    ΔVo = Rout*ΔIL = -135mV
    ---> ΔVo/ΔIL = - 6.7632mV per 1mA of load current.

    Max diode Zener current
    Iz_max = (25V - 9.825V) / (200Ω + 7Ω) = 73.3mA
     
  4. jegues

    Thread Starter Well-Known Member

    Sep 13, 2010
    735
    43
    Thank you this is much more clear, however I don't think we are expected to recalculate the value of R each time, we just kept it at 205ohms as assumed.
     
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