In-Rush Current for power supply

Discussion in 'The Projects Forum' started by chimera, Mar 17, 2012.

  1. chimera

    Thread Starter Member

    Oct 21, 2010
    122
    2
    hello! Recently I decided to build a power supply. The one I have right now is big and really just gives fixed out put voltages.

    Sure, I can add an LM317s or LT3080 to give me the variable voltages, but the output range is limited and then there is matter of the heat sinks...eh just a heap of mess to deal with if I want to modify my current power supply.

    I have read up sufficiently on power supplies

    I have a transformer with 50VA @ 24V secondary. I am using the 1n5408 diodes for the rectification (full wave) and 30,000uF filter caps. The output power of my intended power supply is 40W (20V @ 2A).
    There are more elements present but for the sake of simplicity, I haven't included them here.

    So this is what i need help with:

    1- How do I calcuate the inrush current?

    2- Do I really need to be worried of inrush current for a 40W power supply?

    3- What are my options of implementing a in rush currrent limiting circuit---i.e soft start or an NTC thermistor.

    Any suggestions?
     
  2. chimera

    Thread Starter Member

    Oct 21, 2010
    122
    2
    wow...guys really? no one to help me out??..
     
  3. wayneh

    Expert

    Sep 9, 2010
    12,136
    3,054
    Usually NO. Your average wall wart works fine without concern about start-up. You haven't said whether your supply is SMPS or traditional transformer.
     
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