Do-it-Yourself RFI/EMI filter

[hardcore misery]

anyone? yung pwedeng gamitin sa PSU.

[zer0w1ng]

Ferrite bead on your PS wires. Ok na yan.
Or add an inductor 10uH in series + 2 100nF ceramic caps in parallel before and after the inductor.

['yus]

may way ba para malaman kung effective yung ginawa mong filter? 

[hardcore misery]

Ferrite bead on your PS wires. Ok na yan.
Or add an inductor 10uH in series + 2 100nF ceramic caps in parallel before and after the inductor.

nakaseries lang sa positive terminal ng PSU yung 10uH na inductor?

papano kung mas mataas na inductance ang ginamit? or mag DIY din ng inductor?( concrete nail with magnetic wires?)

[Born2BeWired]

I could guess na kaya mo gusto ang RFI filter is you are experiencing interference problem with some of your equipment everytime you switch ON your power supply.

If your interference problem disappears after you installed your RFI filter, then it must be effective

Otherwise, if you want to make some measurements, maybe you want to check if your power supply product to conforms to FCC conducted emission limits, then you will need at the very least a spectrum analyzer and a LISN (Line Impedance Stabilization Network).

In my experience, passing a single turn of your offending wires through a ferrite core, as suggested by zer0wing, will solve the problem.

[hardcore misery]

Available ba locally yung ferrite cores? ferrite beads ba yung madalas makita sa mga USB cables,?

san ba makakabili nun?

[zer0w1ng]

may way ba para malaman kung effective yung ginawa mong filter? 

Using a spectrum analyzer.
Connect the tracking generator and put the filter in series.
The resulting should be high at low freq and cut at high freq.

[zer0w1ng]

nakaseries lang sa positive terminal ng PSU yung 10uH na inductor?

papano kung mas mataas na inductance ang ginamit? or mag DIY din ng inductor?( concrete nail with magnetic wires?)

The higher the inductance the better.
But if the inductance goes high, its resistance (because of long wires) will get higher also.
This will entail voltage loss/drop on high current loads (E=IR).

[zer0w1ng]

Available ba locally yung ferrite cores? ferrite beads ba yung madalas makita sa mga USB cables,?

san ba makakabili nun?

Yes that is the one. I don't know where to buy them here in the Philippines. Alexan maybe.
You could use the E-I core of switching transformers in computer PSUs and round a single loop there.

[Born2BeWired]

The higher the inductance the better.
But if the inductance goes high, its resistance (because of long wires) will get higher also.
This will entail voltage loss/drop on high current loads (E=IR).

I beg to differ.

Although your voltage loss/drop IR concern is a valid one, the real problem here is the increase in the stray capacitance brought about by the increased number of turns (to get higher inductance). Higher inductance results in higher stray capacitance. And these two put together, lowers the self resonance frequency of the inductor. An inductor, beyond its self resonant frequency, no longer functions as an inductor. It in fact starts to behave like a capacitor!

Reputable inductor manufacturers includes the self resonance frequency in their product specifications. This sets the limit on how much inductance you can put in your filter circuit.

[paranz]

Although your voltage loss/drop IR concern is a valid one, the real problem here is the increase in the stray capacitance brought about by the increased number of turns (to get higher inductance). Higher inductance results in higher stray capacitance. And these two put together, lowers the self resonance frequency of the inductor. An inductor, beyond its self resonant frequency, no longer functions as an inductor. It in fact starts to behave like a capacitor!

Reputable inductor manufacturers includes the self resonance frequency in their product specifications. This sets the limit on how much inductance you can put in your filter circuit.

thanx for the info. ngayun ko lang alam ito ah 

[hardcore misery]

sige, susubukan ko yung capacitor-inductor circuit pati narin yung E-I core... thanks!

[zer0w1ng]

Although your voltage loss/drop IR concern is a valid one, the real problem here is the increase in the stray capacitance brought about by the increased number of turns (to get higher inductance). Higher inductance results in higher stray capacitance. And these two put together, lowers the self resonance frequency of the inductor. An inductor, beyond its self resonant frequency, no longer functions as an inductor. It in fact starts to behave like a capacitor!

Yes this is very true. I  missed it.
If working on very high frequency, and inductor becomes a capacitor due to capacitance between each wind/turn will be bigger as the number of turns increase.

Also capacitors, tend to become inductors on high freq especially electrolytics because the plates are wound to each other. Capacitor legs also adds to this.  That is why on high freq ckts, SMD components are advisable.

[Born2BeWired]

@paranz,zer0w1ng

Yes sirs! At RF frequencies, component leads are unwelcome. And the solution is straightforward: remove the component leads! Who would suspect this? Another reason why electronics is never boring.

@hardcore
picture ng wire passing through a ferrite core for RFI reduction:



Note that the two wires are twisted together. This will help in reducing RFI further (by reducing the loop between the power source (+) wire and ground return). Palagay ko may mabibili kang ganitong ferrite core sa mga sidewalk vendors sa raon.

This simple solution solved my interference problem dito sa SMPS power supply I am currently working on:

[zer0w1ng]

Nice PCB layout! 

[ftdc]

@Born2BeWire

Ano topology yan sir?

[Born2BeWired]

Voltage mode DC/DC converter ito. Converts 24VDC to 150VDC. First protoype pa lang kaya maraming revisions pang dadaanan ito

[hardcore misery]

@paranz,zer0w1ng

Yes sirs! At RF frequencies, component leads are unwelcome. And the solution is straightforward: remove the component leads! Who would suspect this? Another reason why electronics is never boring.

@hardcore
picture ng wire passing through a ferrite core for RFI reduction:



Note that the two wires are twisted together. This will help in reducing RFI further (by reducing the loop between the power source (+) wire and ground return). Palagay ko may mabibili kang ganitong ferrite core sa mga sidewalk vendors sa raon.

This simple solution solved my interference problem dito sa SMPS power supply I am currently working on:

yung wires na nakapuluput sa ferrite core, yan na yung + and - terminals?

sige, scout ako sa raon pagnagkataon.

[Born2BeWired]

yung wires na nakapuluput sa ferrite core, yan na yung + and - terminals?

Yes

[subzer0]

@Born2beWired

Flyback ba yung ginamit mpo na topology sir?