Series/Shunt Regulator

Discussion in 'General Electronics Chat' started by phuzionz, Jan 4, 2009.

  1. phuzionz

    Thread Starter Active Member

    Dec 5, 2008
    47
    0
    Dear members,

    Yesterday i look into the stuff of the series and shunt regulators.
    I build the two circuits and did a few measurements.
    These circuits are used for a better line and load regulation.
    Line regulation = when there are variations on the power supply.
    Load regulation = when there are variations on the current trough the load.
    Please, Correct me if i'am wrong.

    Sunt regulator:

    Rs= 320
    diode 8.2V
    Rload1 = 460
    Rload2 = 1.47k

    When i measured the voltage over Rload(460), i measure 6.8V.
    I measured that the current through Rs and Rload1 was the same.

    When i measured the voltage over Rload(1,47k), i measure 8.2V.
    I measured that the current through Rs was 10mA and through Rload2 was 5.5mA.
    With this measurement i want to simulate the load regulation.(diffrent current).
    Is that normal ?
    Can i assume that i have the same problem as described in the link.
    http://www.allaboutcircuits.com/vol_3/chpt_3/11.html

    Series Regulator:

    Rs= 320
    diode 8.2V
    Rload1 = 460
    Rload2 = 1.47k

    When i measured the voltage over Rload(460), i measure 6.8V.
    When i measured the voltage over Rload(1,47k), i measure 8.2V.


    Circuits:
    http://www.tpub.com/content/neets/14179/css/14179_230.htm

    Jef
     
  2. mik3

    Senior Member

    Feb 4, 2008
    4,846
    63
    It is not normal to measure voltages lower than the zener voltage on the zener regulator. This happens because your load resistance is too low. Theoretically, the zener regulates if the voltage across the load without the zener in the circuit is greater than the zener voltage (use the voltage divider rule to find it). Practically, it won't work like that, the voltage across the zener varies with the load through the zener diode.
     
  3. italo

    New Member

    Nov 20, 2005
    205
    1
    The zener to be able to regulate the voltage across the load must be able to dissipate the load current plus its own forward current when there is no load. It is a matter of power and dissipation of the device to be considered for stable regulation. A zener must have enough current to make sure that is on a stable breakdown curve. If too little then it will be sitting on the very breakdown knee. A very stable zener at low voltage is the breakdown of Vbe on a transisto. Great except you cannot predict the voltage breakdown to be exact. But it is sharp practically no knee to speak of. As zeners approaches < 5v the knees becomes more pronounced. Some old devices were in fact diodes in series.
     
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