Electronics > Beginners

How does a noise filter work?

<< < (4/4)

max.wwwang:

--- Quote from: EEEnthusiast on February 12, 2020, 10:03:25 am ---The battery is powering a UPS which creates a lot of switching noise. This noise can radiate from the wires connecting the batteries to the PCB as its length is long. The ferrite bead acts as a damper for these switching signals in order to minimise the EMI.


--- End quote ---

--- Quote from: radiolistener on February 13, 2020, 10:47:56 pm ---
--- Quote from: max.wwwang on February 12, 2020, 07:45:40 am ---It's simply a charging/discharging process, both would be pretty stable (I guess). How could there be EMI emissions in these 2 wires?

--- End quote ---

There are a lot of pulses in charger circuit, because it is based on Switched-Mode Power Supply. Any current change (any pulse) in the wire leads to EMI emission from this wire. So, there is a filter to minimize EMI produced by current pulses in the wire...

--- End quote ---

I understand the fact that in the switching circuits where could be high frequency noise components which we would not like it to propagate to outside of the unit. The problem is, because of the wiring (two wires go through the ferrite ring), any internal niose in one wire would cancel that in the other) then there would be no effect of cancelling the noise that is generated in the unit itself.

May be I was wrong, this should be called differential mode? Whatever the correct name is. How it works remains the same.

Furthermore, I recently came across some other UPS units and saw designs where these two wires actually wind around the ring (2-3 turns). I guess there is no right number of turns. We should have as many turns as is practicable to get the best noise cancelling effect?

 

Navigation

[0] Message Index

[*] Previous page

There was an error while thanking
Thanking...
Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod