In-Rush Current for power supply

Thread Starter


Joined Oct 21, 2010
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 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?