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Multi (wide) Voltage LED using LM317

Malcolm
Just a thought, we know you can change a linear voltage regulator like the LM317 into a series constant current regulator by just adding one resistor (loads of application notes on Farnell Web site) but can it be done with the LM431 adjustable shunt regulator?
Anyone know?

 

Regs (regards not regulator)

Malcolm

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    Ah so it can be used as a constant current source.

     

    Just one (or two points) The resistor is ok if the input voltage is constant, I wanted to a wide input voltage range with a constant brightness, hence the constant current feed.

     

    Now is it always more efficient to use a switching regulator (certainly not cheaper)? I read an article that asked that same question and the answer was not always. It seems that if the differential voltage is small then it may be more efficient to use a linear regulator.

     

    Regards

    Malc

    image

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    Ah so it can be used as a constant current source.

     

    Just one (or two points) The resistor is ok if the input voltage is constant, I wanted to a wide input voltage range with a constant brightness, hence the constant current feed.

     

    Now is it always more efficient to use a switching regulator (certainly not cheaper)? I read an article that asked that same question and the answer was not always. It seems that if the differential voltage is small then it may be more efficient to use a linear regulator.

     

    Regards

    Malc

    image

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