What are the reverse voltages here ?

Discussion in 'General Electronics Chat' started by Externet, Jan 7, 2016.

  1. Externet

    Thread Starter AAC Fanatic!

    Nov 29, 2005
    758
    57
    For these 3 circuits, what Vr are LEDs exposed to ?

    P1010596.JPG
     
  2. Dodgydave

    Distinguished Member

    Jun 22, 2012
    4,969
    744
    Zero,
     
    Last edited: Jan 7, 2016
  3. MikeML

    AAC Fanatic!

    Oct 2, 2009
    5,450
    1,066
    Not clear if you mean 20Vrms or 20Vp-p?

    If 20Vp-p, then here are all the relevant Voltages and Currents. Note that there is never any reverse voltage across the LEDs, so your reverse diode is redundant.

    339.gif

    Same without the capacitor...

    339nc.gif
     
  4. Externet

    Thread Starter AAC Fanatic!

    Nov 29, 2005
    758
    57
    Thanks.
    20 VRMS supply. The LEDs are rated for a maximum of 5 Vr. Are they safe to operate this way considering the negative excursions of the AC ?
     
  5. MikeML

    AAC Fanatic!

    Oct 2, 2009
    5,450
    1,066
    Did you miss this sentence:

    Note that there is never any reverse voltage across the LEDs, so your reverse diode is redundant.
     
  6. Sinus23

    Member

    Sep 7, 2013
    160
    396
    You already have a half wave rectifier with a smoothing capacitor. The voltage that the led are experiencing is only positive.
     
Loading...