+ Post New Thread
Results 1 to 5 of 5
  1. #1
    Full Member level 5
    Points: 2,680, Level: 12
    Achievements:
    7 years registered
    kappa_am's Avatar
    Join Date
    Jul 2012
    Location
    Vancouver
    Posts
    311
    Helped
    19 / 19
    Points
    2,680
    Level
    12

    Dc/Dc controller LT8316 power limit

    Hi,
    I am designing a wide-range input DC/DC converter. I came to LT8316. It is a controller and we should use an external switch, but in datasheet, it is stated that the power limit is 100W. My question is why? while we can use any switch on output and scale feedbacks. Why limits the output power?

    Thank you
    Good world needs knowledge, kindness and courage.

    •   AltAdvertisement

        
       

  2. #2
    Advanced Member level 5
    Points: 11,955, Level: 26

    Join Date
    Aug 2015
    Location
    Melbourne
    Posts
    1,955
    Helped
    714 / 714
    Points
    11,955
    Level
    26

    Re: Dc/Dc controller LT8316 power limit

    above ~ 100 watt, layout, RFI, and transformer construction issues tend to dominate and need an experienced power electronics designer - the RFI especially can upset the control, the leakage inductance causes extra losses and over volt spikes on the main switch ..... and more ...



    •   AltAdvertisement

        
       

  3. #3
    Advanced Member level 3
    Points: 6,274, Level: 18

    Join Date
    Feb 2014
    Posts
    904
    Helped
    298 / 298
    Points
    6,274
    Level
    18

    Re: Dc/Dc controller LT8316 power limit

    100W is often considered the upper useful limit for a flyback.

    Flybacks make relatively poor use of the transformer meaning its size increases quickly with power. Around 100W other topologies become more attractive (like forward, push-pull, half bridge). There is a general tradeoff where higher switch count topologies allow more efficient use of the transformer.



    •   AltAdvertisement

        
       

  4. #4
    Advanced Member level 1
    Points: 3,652, Level: 14

    Join Date
    Sep 2013
    Posts
    402
    Helped
    162 / 162
    Points
    3,652
    Level
    14

    Re: Dc/Dc controller LT8316 power limit

    Why 100W max because this IC designed for 100W operation, Internal Gate Driver Bias Voltage of IC is about 12 V this voltage cant drive Power MOSFET, with use of a gate driver it is possible.
    For Flyback application below 100W is reasonable because flyback topology required MOSFET current ratting 5.5times required current. For example 1000W offline flybac(200V input), input current will be 5A so we need to select 27.5A MOSFET at 400V or above, this mosfet will be cost high. So above 100W application other forward topologies are selecting.



  5. #5
    Advanced Member level 3
    Points: 6,274, Level: 18

    Join Date
    Feb 2014
    Posts
    904
    Helped
    298 / 298
    Points
    6,274
    Level
    18

    Re: Dc/Dc controller LT8316 power limit

    To be clear I don't think there is a 100W limit. The 100W number is Analog/Linear trying to be realistic and helpful (and they sell controllers better suited for higher power).

    12V is fine for high power gate drive but the internal gate driver probably isn't strong enough to drive a large fet.

    Otherwise yes I think you answered it. You could use this controller, perhaps with an external gate driver and very large fet to make a 1kw flyback converter. But it would be more expensive and larger than other topologies.



--[[ ]]--