SMPS, without filtering caps?

Thread Starter

NoelSof

Joined Sep 22, 2015
12
Hi,
I dismantled this welder, an inverter type rated at maximum 120A @55V, I noticed there's no filtering capacitor at the output. Opened another one and again there's no capacitor. It's all working good though, my work there was just to clean it from dust.
So, what kind of SMPS is this that doesn't need filtering capacitors?IMG_20170814_194720.jpg
 

AlbertHall

Joined Jun 4, 2014
12,345
An SMPS will work just fine with or without smoothing capacaitors. With then you get smooth (ish) DC, without the you get a series of pulses. If you are powering, say, an audio amplifier then you need the smooth DC. Now I don't know much about welding but it would seem that you can weld just as well, or possibly better, with pulses.
 

recklessrog

Joined May 23, 2013
985
Welder Inverters do not need smoothing capacitors to work, they are not powering circuits, just melting metal.
The only one I ever worked on had active ripple suppression I think, also it had an active phase correction circuit.
As Alberthall suggests, the feedback would probably be a sample that is smoothed separately, or peak ripple detection.
 
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