zener diode

Discussion in 'The Projects Forum' started by kfrazie1, Feb 10, 2010.

  1. kfrazie1

    Thread Starter New Member

    Jan 4, 2010
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    I'm thinking of using a zener diode to regulate 12 V from a voltage source that produces a max of 24 Volts and about 14 Amps. Would I need a zener diode that has a power rating of 14*12=168 Watts?
     
  2. SgtWookie

    Expert

    Jul 17, 2007
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    What current do you need at 12v?

    A Zener is a shunt regulator. They are cheap, and useful for small loads, but not very efficient.
     
  3. russ_hensel

    Well-Known Member

    Jan 11, 2009
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    Linear regulators are one step up from zeners, almost as cheap. I think the part number is 7812.
     
  4. SgtWookie

    Expert

    Jul 17, 2007
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    If your load is up to perhaps 40mA, you could use just a Zener and a resistor. Regulation won't be very good.

    A 7812 is good for about 1A, but with a 24v supply, you will dissipate 1/2 the power of the load in the regulator itself. You will need a heat sink for a load greater than around 80mA.

    Switching regulators are much more efficient, but are more complex.
     
  5. kfrazie1

    Thread Starter New Member

    Jan 4, 2010
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    My current can reach up to around 14 amps....
     
  6. mik3

    Senior Member

    Feb 4, 2008
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    The most efficient solution is a buck DC/DC converter.
     
  7. spacewrench

    Member

    Oct 5, 2009
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    Are there any other solutions? I suppose you could design something using a transformer where a buck converter has its inductor, but that fits in pretty much the same mental "box" for me. How else could you provide such a large amount of current?
     
  8. mik3

    Senior Member

    Feb 4, 2008
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    You can use a linear regulator but this will be very inefficient due to the significant amount of current. What is more, a big heat sink is needed to dissipate heat fast which occupies large space. For DC to DC voltage level conversions switching regulators are the most efficient until now.
     
  9. SgtWookie

    Expert

    Jul 17, 2007
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    You'd be pretty hard-pressed to step down 24v to 12v using a linear regulator; the power dissipation in the regulator would be the same as the dissipation in the load. Not a happy situation.
     
  10. russ_hensel

    Well-Known Member

    Jan 11, 2009
    818
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    It is not a happy situation, but if a resistor is added in series with the regulator the same power will be wasted but the power will go into the resistor instead of the regulator. Leave enough voltage at the input of the regulator for it to regulate ( and consider droop in the 24 v input )

    All that said, if you really need 14 amps out for any period of time, some sort of switching regulator is really required.
     
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