Question about the Inductors and Capacitors used at output of SMPS

Thread Starter


Joined Jan 18, 2016
Hi, I was going through a switch mode power supply and was wondering how the capacitor and inductor size are chosen for the outputs. I'm assuming its used for filtering and to smooth out ripples. One other thing I noticed was that for the -12V output different size of inductors and capacitors were used compared to the 12V output. I would greatly appreciate if someone could share a light on this and help me wrap my head around it. Thanks in advance

*I have attached the schematic diagram of the part I'm talking about.



Joined Sep 17, 2013
As I read it, C5/7/10 are reservoir caps, C8/11 provide additional smoothing. I would guess the -12V rail is intended to drive a higher-current load than the -24V rail, hence C7 is bigger than C5 to keep the voltage up. The +12V rail is clearly intended to provide the most current.


Joined Mar 14, 2008
The inductor is generally an integral part of the SMPS as it stores energy between the switch-mode pulses to generate the desired average output voltage as filtered by the capacitor.