A multi-stage EMI-Filter for DC Power-Supplies Pt.1: Noise sources and noise-coupling
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- čas přidán 11. 07. 2024
- Link for Pt.2: • A multi-stage EMI-Filt...
The filter is now available readily assembled in 3 different ratings as well as bare PCBs for self-assembly in our shop:
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(This is the shop for customers from Europe. For customers from overseas it will be available from February 2018 in our new shop:
www.ak-modul-bus.de/eng)
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Roger explains 4 sources of noise and on which ways they couple into sensitive circuits like AM radio-receivers or precision analog-circuits. There is a fifth source of noise with SMPS working in so-called "discontinous mode". Will be explained in Pt. 3 of this series.
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Thank you! Finding this information very valuable!
Amazing tutorial👏🏿Thank you sir!
Awesome tutorial. Why do some manufactures put a capacitor between the low side and side of the switchable power supply. I always thought they were separated by op-amps for controlling the frequency, you cut a trace on the PCB to eliminate interference. Thanks Hope any one can help me...
What you mean is probaly the separation of primary (mains-connected) and secondary side (output) of the SMPS.
The slot there bridges an optocoupler, not an opamp.
But the noise is transferred via the flyback-transformer/inductor between primary and secondary side (and additionally by the sometimes present capacitor between primary and secondary side).
From Wikipedia: "The primary and secondary sides may be connected with a capacitor to reduce EMI and compensate for various capacitive couplings in the converter circuit, where the transformer is one. This may result in electric shock in some cases. The current flowing from line or neutral through a 2 kΩ resistor to any accessible part must, according to IEC 60950, be less than 250 μA for IT equipment."
I'm sorry I meant to say optocoupler and not opamps. The cap is to reduce EMI. Got it!!! I will read up.. Thank you so much for answering my question and your time. Good day sir....
u know about plasma cutter frequency?
No. Why u ask?
@@KainkaLabs
i made cnc plasma cutting machine.when plasma cutter start my computer screen blink and crashing computer output data because of plasma cutter highly frequency and it emission lots of radio frequency.
so how to protect computer from rf frequency?
First your computer should get it´s power from a different phase of your mains-power. Here in Europe we have a 3 phase-system where the 3 phases are distributed evenly to the wall-outlets in a house. So try checking to connect your PC to a different wall outlet (with some distance to the outlet where the plasma-cutter gets its power from).
You have to find out if the RFI is through radiation or conducted noise through the cables (main power cable).
With high-frequency AND high currents it could be both.
For radiated RFI the only help is more distance to the plasma-cutter and/or an extra metal-shielding for your PC and screen ("Faraday Cage").
For conducted RFI the only help is a different phase of your mains-power and/or a highly efficient AC EMI-Filter (our one is for DC).
@@KainkaLabs
thanks a lot👍
hello I confuse for Faraday cage.
grounding required for Faraday cage? suppose grounding required so what type grounding
Why is common mode noise a problem if it affects both - the negative and positive line by the same magnitude and at the same time? The parts attached on those lines only care about voltage relative to the negative line - which remains same even with common mode noise. If I have understood it right they can't even sense common mode noise. So why bother?
Explained in more detail in Pt.3:
czcams.com/video/2ZjKieigydc/video.html
Common mode and noise is a huge problem with radio frequency communication because the common mode signal present on any cable effectively acts as an antenna. Radio signals are weak, typically a few microvolts. The output from a switch mode power supply if not properly filtered will contain broadband hash at several 10's of millivolts which can completely wipe out everything but the strongest radio stations.