Remove ac ripple from ckt

Discussion in 'General Electronics Chat' started by aamirali, Aug 5, 2014.

  1. aamirali

    Thread Starter Member

    Feb 2, 2012
    415
    1
    1. I have a board, which is getting +8V from a ac-dc power supply.
    Input to ac-dc power supply: 220V ac , 50Hz.
    output of ac-dc: +5V dc

    Now this output contain noise. What I think it will be 50hz noise from power supply riding over +7Vdc.

    I have put a 7805 regulator on my circuit which converts +8V to +5V.

    What capacitor value should I place on regulator which can remove the noise.


    2. In second case, I have a li-ion battery over which a boost converter is fitted, converted its voltage to +5V dc.
    It powers my circuit. But since its a boost conveter in contains noise depending upon the its frequency.

    How to remove this noise.
     
  2. MrChips

    Moderator

    Oct 2, 2009
    12,449
    3,365
    I would replace the 7805 with a low-drop-out (LDO) regulator such as LF50ABV-DG.

    To determine the value of the capacitor you need to specify the load current.
     
  3. aamirali

    Thread Starter Member

    Feb 2, 2012
    415
    1
    Load current on normal mltimeter , which will bypass high frequency reading goes upto 60mA
     
  4. aamirali

    Thread Starter Member

    Feb 2, 2012
    415
    1
    MCU is running at 120Mhz using 16Mhz internal oscillator by PLL
     
  5. MikeML

    AAC Fanatic!

    Oct 2, 2009
    5,450
    1,066
    Any available Low-Dropout 5V LDO regulator should work (not LM7805 series).
    Minimum capacitor values for your specific LDO are shown on the data sheet. Do not go below those values. If there is no "filter capacitor" on the output of the upstream rectifier, then you will also have to add this...
     
  6. D.T.

    New Member

    Aug 15, 2014
    4
    0
    I'm fighting a ripple problem on a plating rectifier my self. Just reading around to see how I can repair. 11% ripple from a 5A unit.

    Silicon old style rectifier.
     
  7. MikeML

    AAC Fanatic!

    Oct 2, 2009
    5,450
    1,066
    Your should start a new thread in a case like this...
    Read this recent thread.
     
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