+ Post New Thread
Results 1 to 6 of 6
  1. #1
    Advanced Member level 2
    Points: 2,224, Level: 10

    Join Date
    Aug 2016
    Posts
    578
    Helped
    6 / 6
    Points
    2,224
    Level
    10

    Do The Input And Output Capacitors Effect Efficiency In Switching Regulators

    Would increasing the input and output capacitances were the load is~2mA @ 25v and input is ~8v prolong the battery life?

    For this switcher MT3608.pdf

    •   AltAdvertisement

        
       

  2. #2
    Super Moderator
    Points: 77,854, Level: 68
    Achievements:
    7 years registered
    Awards:
    Most Frequent Poster 3rd Helpful Member

    Join Date
    Apr 2014
    Posts
    15,793
    Helped
    3593 / 3593
    Points
    77,854
    Level
    68

    Re: Do The Input And Output Capacitors Effect Efficiency In Switching Regulators

    Hi,

    Theoretically yes, but it's only marginal. I don't think it's worth it.
    I expect far less than 1% prolong time.

    Klaus
    Please donīt contact me via PM, because there is no time to respond to them. No friend requests. Thank you.


    1 members found this post helpful.

    •   AltAdvertisement

        
       

  3. #3
    Advanced Member level 2
    Points: 2,224, Level: 10

    Join Date
    Aug 2016
    Posts
    578
    Helped
    6 / 6
    Points
    2,224
    Level
    10

    Re: Do The Input And Output Capacitors Effect Efficiency In Switching Regulators

    Quote Originally Posted by KlausST View Post
    Hi,

    Theoretically yes, but it's only marginal. I don't think it's worth it.
    I expect far less than 1% prolong time.

    Klaus
    Is this largely due impart MLCCs being leaky?



    •   AltAdvertisement

        
       

  4. #4
    Super Moderator
    Points: 77,854, Level: 68
    Achievements:
    7 years registered
    Awards:
    Most Frequent Poster 3rd Helpful Member

    Join Date
    Apr 2014
    Posts
    15,793
    Helped
    3593 / 3593
    Points
    77,854
    Level
    68

    Re: Do The Input And Output Capacitors Effect Efficiency In Switching Regulators

    Hi,

    I expect the ESR loss is higher than the leakage loss.
    But I did not calculate it ...

    Btw: without knowing voltage and current waveforms and exact part names calculation is impossible anyway.

    Klaus
    Please donīt contact me via PM, because there is no time to respond to them. No friend requests. Thank you.


    1 members found this post helpful.

  5. #5
    Advanced Member level 2
    Points: 2,224, Level: 10

    Join Date
    Aug 2016
    Posts
    578
    Helped
    6 / 6
    Points
    2,224
    Level
    10

    Re: Do The Input And Output Capacitors Effect Efficiency In Switching Regulators

    Quote Originally Posted by KlausST View Post
    Hi,

    I expect the ESR loss is higher than the leakage loss.
    But I did not calculate it ...

    Btw: without knowing voltage and current waveforms and exact part names calculation is impossible anyway.

    Klaus
    Wouldn't the ideal method to reduce ESR be to break up the recommended 22uF from switcher datasheet - into 3x 10uF capacitors thereby reducing ESR?



    •   AltAdvertisement

        
       

  6. #6
    Advanced Member level 5
    Points: 39,779, Level: 48

    Join Date
    Mar 2008
    Location
    USA
    Posts
    6,429
    Helped
    1878 / 1878
    Points
    39,779
    Level
    48

    Re: Do The Input And Output Capacitors Effect Efficiency In Switching Regulators

    Input filter capacitor ESR is a big deal in low voltage
    POL buck converters. The capacitor sees current
    equal to IOUT - charging during output switch "off"
    interval and discharging during "on" interval. So every
    electron you throw to the output gets dragged across
    the input filter cap ESR, twice. IIN of the DC-DC power
    stage is a square wave current, and in-the-moment
    on high fSW converters, little of it comes from the
    power source, most of it from the close-in decoupling.
    The less input voltage ripple you see, the more true
    this is.

    Output filter only sees the output inductor ripple current
    so its ESR matters a lot less to efficiency. ESR and ESL
    are however both key to minimize load-step deflection
    in the interval between application of the new load, and
    the control loop coming around.

    At 2mA however I'd bet it's all about switching losses
    and not so much either filter.


    1 members found this post helpful.

--[[ ]]--