Line Filtering

[bean3]

Hi everyone,

I am trying to design a PCB with an IEC input , line filter and AC-DC converter and I need a bit of help with line filters.

100 - 240vac to 15vdc. about 2 amps. All mains components are to be PCB mounted.

I want this device to be EMC compliant but we are not a big company with large budgets for EMC testing. We do aim to have this device (a sensor display) tested but we would prefer to avoid repeat testing. We are looking as BS 61326 (Electrical equipment for measurement, control and laboratory use) So lets begin with the power inlet and PSU...

I have found some IEC inlet connectors with single stage filters, pcb mount filters and various AC-DC converters.

I'd like to know if it is better to have an unfiltered IEC then use a multistage filter after it then off to the ACDC converter or can I use an IEC with a single stage filter then another single or multi stage filter inline after it?

Any thoughts or further info required?

Cheers, Ben

[stj]

Re: Line Filtering

it will depend on the actual psu.
how are you converting mains to 15v?

[budm]

Re: Line Filtering

It depends on how bad you switching power supply is, you need to reduce its noise generated by the SMPS from injecting (conductive) back into the power line and radiating.
It is tough without having your own test equipment to do the pre-test (Radiate and Conductive) first, I know the EMC/EMI/CE testing not cheap, we spend hundreds of thousand dollars for the US and EURO products. You can design your own common mode/diff mode filer but it is specialized field, we have our own in-house Engr to do that.
Example of EMI, EMC reports.
https://cdn.badcaps-static.com/pdfs/...604886b3cb.pdf

http://www.iec.ch/emc/basic_emc/basic_61000.htm

https://cdn.badcaps-static.com/pdfs/...b26fcd22b4.pdf

http://www.schurter.com/en/Component...es-with-Filter

[bean3]

Re: Line Filtering

I was going to use a simpler AC to DC converter something like this...
https://cdn.badcaps-static.com/pdfs/...a32e146f0e.pdf

It has some type of line filter built in. Do I need another before this?

[budm]

Re: Line Filtering

It looks like it has been through the compliance testing already by itself, but your product will need be tested as a completed products. The circuit that will be running using this power supply has high frequency Oscillator which will injecting/radiating high frequency?
EMC
EMI Compliance with EN55022 Class B
EMS Compliance with EN55024, EN55014-1, EN550

[bean3]

Re: Line Filtering

There is an 18Mhz crystal to clock the PIC. Other than that, nothing else that should act as an oscillator