Rectification-what does good regulation mean?

Discussion in 'General Electronics Chat' started by kod, Nov 22, 2009.

  1. kod

    Thread Starter New Member

    Nov 22, 2009
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    Hi all,
    I'm new to the site and would firstly like to say hello to all.I am wondering can anyone explain to me what the term 'good regulation' means when applied to D.C. rectifier power outputs, utilised for electronic circuits.
     
  2. jut

    Senior Member

    Aug 25, 2007
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    Hello. Welcome to the forum. You've come to a good place with smart/knowledgeable people.

    From what I know, one aspect of a good DC rectifier means that there's isn't much AC ripple in the resulting DC output of a rectifier circuit. Think of it this way, you have AC coming into the circuit and DC coming out. Some of that fluctuating AC voltage ends up at the output. The less the better, i.e., the less ripple the better regulation.

    A measure of good regulation would be to measure the voltage (peak-to-peak) of the ripple and divide it by the amount of DC voltage.

    The picture below shows a DC voltage of 5 volts at the output, but there's an AC voltage "riding" on it. The percent ripple would be 0.4/5 = 8%

    [​IMG]
     
    Last edited: Nov 22, 2009
  3. t_n_k

    AAC Fanatic!

    Mar 6, 2009
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    Good regulation would mean the ability of the power supply to maintain a nearly constant DC output terminal voltage for the permissible range of current loading that might be drawn from the power supply.

    Simple DC [i.e. transformer plus rectifier diode(s) plus filter capacitor] rectifier circuits are rarely capable of achieving good regulation performance of themselves - which has led to the development of a large range of purpose designed semiconductor voltage regulator devices that are used in conjunction with simple DC rectifiers to achieve improved DC regulation - e.g. LM7805 etc.
     
  4. jut

    Senior Member

    Aug 25, 2007
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    tnk, would you say my explanation is not a good definition of regulation?
     
  5. studiot

    AAC Fanatic!

    Nov 9, 2007
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    The term 'regulation' (at stated load or current) is defined as the difference between no load output and the output at stated load, expressed as a % of the no load figure.

    Regulation % = 100(Vo - Vl) / Vo

    % ripple is another important term and is a measure of the smoothing or filtering of the DC supply.
     
  6. Wendy

    Moderator

    Mar 24, 2008
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    All of the above is correct.

    Another aspect of DC is impedance, or resistance, of the power supply.

    A battery has an internal resistance. This resistance dictates how much current it can give max. It also dictates what the battery voltage is for a specific current.

    This concept translates somewhat to a DC power supply, especially since the wires connecting the output of the regulator to the load also have resistance (abet very low). Electronics, with feedback loops and whatnot, make this resistance as low as it can be.
     
  7. t_n_k

    AAC Fanatic!

    Mar 6, 2009
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    One might also include the degree to which variations in the input supply voltage [such as the AC mains supply voltage in a typical rectifier circuit] influence the regulation of the output DC side voltage.

    It's interesting to look at specifications for switch mode power supplies which can routinely & reliably operate over wide AC supply voltage range [typically 85 - 265V AC] without any loss of regulation performance. These are a testimony to the skill and art of the electronic design engineers.
     
  8. ntmarwade

    New Member

    Nov 3, 2009
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    I agree with studiot.

    The AC component in DC output causes ripple. This directly affects line regulation.

    There also load regulation.
     
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