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Bridge rectifiers and voltage regulators

Discussion in 'General Electronics Discussion' started by Zellarman, Nov 10, 2011.

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  1. Zellarman


    Nov 9, 2011
    I'm working on an led lighting project, and was hoping to make it work on any (within a reasonable range) type and rated transformer, a low (under say 35v) AC or DC power source. I'm just an amatuer, so could be off a bit, but was thinking about using a bridge rectifier and voltage regulator to do this. Now as I'm typing, I realize the power source will also have a minimum power requirement I'm guessing 2v above whatever the circuit needs because that's the cut off (?) of most regulators?

    But even more of a question to me, is what happens if you feed DC to a Bridge rectifier? Does it cut the signal in half or something like that? I mean if it keeps the sign wave of an AC source all on the positive side, essentially flipping the 'bottom' half of the AC sine wave, then what does it actually do w/ the DC current, or would it pass through unaffected?

    Also what happens w/ DC power through a voltage regulator, if the regulator has a 2v cutoff (?) and you feed 12-14 volts to a 12 volt regulator, does it still pass the voltage unregulated, not at all, or what?
  2. davenn

    davenn Moderator

    Sep 5, 2009
    DC in DC out :) yes and you will loose ~ 0.6 of a Volt

    I often use a bridge rectif. on the input to expensive gear. Its a great way to protect against accidental power reversal. As it doent matter the polarity of the input you will always get the correct polarity out :)

    Voltage regulators .... depends on the regulator... eg. a 7812 wont start regulating properly till the input Voltage is ~ 2V higher than the output so 14V upwards to it max input, ~ 30V

    there are other low dropout regulators that you can bring the input Voltage down closer to the regulated output Voltage

    Last edited: Nov 10, 2011
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