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PCB Design with an IEC Input and Line Filtering

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Newbie level 2
Aug 11, 2015
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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

Good IEC input units have a metal shield around around them and often a fuse as well, so you get a lot for your money. There should also be a graph available for the filter performance, so you can work out if any further filtering could be required. I suspect that unless you are going to be making over a thousand units, a bought in unit will be cheaper and more straight forward.

Thanks very much chuckey. I have looked at various filters and IEC input connectors all graphs showing performance. A separate multistage filter has far greater performance than a single stage IEC filter. Most AC/DC converters have some type of line filter incorporated. Is it ok to run two filters inline with each other?

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