Hi ,

I am looking for Bidirectional EMI filter. When i/p 110V is applied via filter on main board, it goes to another piggy board to generate 380V and this 380V is again brought on main board. This is switching 380V and hence sends noise back to AC lines cauisng failure.
I am looking for Bi directional filter which will reduce noise while applying input to main board as well as reduce noised which is reflected back to AC lines.
Is there any filter we can have PC mount or how to design this ?

Regards,
Amod

 

Hi ,

I am looking for Bidirectional EMI filter. When i/p 110V is applied via filter on main board, it goes to another piggy board to generate 380V and this 380V is again brought on main board. This is switching 380V and hence sends noise back to AC lines cauisng failure.
I am looking for Bi directional filter which will reduce noise while applying input to main board as well as reduce noised which is reflected back to AC lines.
Is there any filter we can have PC mount or how to design this ?

Regards,
Amod

It sounds like what you need is a common-mode choke cascaded with a differential mode choke. I can give you a link if this is of interest to you.

 

It sounds like what you need is a common-mode choke cascaded with a differential mode choke. I can give you a link if this is of interest to you.

Yes. Pl. share the link.

 

Yes. Pl. share the link.

This is part #12 in a series of videos on the design and analysis of a flyback converter. It is the best explanation I have found so far. It is bidirectional and prevents noise transmission in both directions. Videos 9-11 in this series explain the components in more detail.

 

Most commercial power line filters are at least partly bi-directional. Corcom (now a part of Tyco Electronics) is the big American name; Schurter and Schaffner are big in Europe. For best noise containment, the filter is part of the input connector rather than a board assembly, to reduce radiated noise pickup between the filter and the connector.



What is the AC input current? Also, are there any specific EMI/RFI standards you have to meet?

What are the frequencies of the power switching circuits?

ak

 

Most commercial power line filters are at least partly bi-directional. Corcom (now a part of Tyco Electronics) is the big American name; Schurter and Schaffner are big in Europe. For best noise containment, the filter is part of the input connector rather than a board assembly, to reduce radiated noise pickup between the filter and the connector.

View attachment 267926

What is the AC input current? Also, are there any specific EMI/RFI standards you have to meet?

What are the frequencies of the power switching circuits?

ak

The TS was posting about a DC-DC converter application, not necessarily related to problems with the AC line, but with other subsystems connected to the same AC line. That is what the chokes are designed to do, and they work in both directions. We're also not sure the TS has correctly identified and quantified the root cause of the problem. I suspect some amount of hopeful guesswork is involved. It won't hurt to run the experiment to confirm or refute the initial hypothesis.

 

The TS was posting about a DC-DC converter application,

We don't actually know that. Given a 110 Vac input, 380 V sounds a lot like the output of an AC/DC boost converter, maybe a power factor correcting stage that drives DC/DC converters like Vicor 2nd Gen bricks. He also talks about noise reflected back to "the AC lines", a very common PFC problem. He already has an input power line filter on his main board, which probably is not shielded, and clearly is not doing the job. EMI hopping over something like that and getting into the AC input wiring is a real thing. Shielded internal wiring and a shielded external line cord help, but nothing beats metal-to-metal contact between the body of the input filter and a metal chassis right at the input connector. For example, in my experience, it's the only way a system can pass TEMPEST.

ak

 

We don't actually know that. Given a 110 Vac input, 380 V sounds a lot like the output of an AC/DC boost converter, maybe a power factor correcting stage that drives DC/DC converters like Vicor 2nd Gen bricks. He also talks about noise reflected back to "the AC lines", a very common PFC problem. He already has an input power line filter on his main board, which probably is not shielded, and clearly is not doing the job. EMI hopping over something like that and getting into the AC input wiring is a real thing. Shielded internal wiring and a shielded external line cord help, but nothing beats metal-to-metal contact between the body of the filter and a metal chassis right at the input connector.

ak

You're right of course. WITHOUT A COMPLETE SCHEMATIC of all the boards we can only speculate about the problem and possible solutions. It was however my best guess based on my experience as to a possible solution. Your mileage might differ.

 

Most commercial power line filters are at least partly bi-directional. Corcom (now a part of Tyco Electronics) is the big American name; Schurter and Schaffner are big in Europe. For best noise containment, the filter is part of the input connector rather than a board assembly, to reduce radiated noise pickup between the filter and the connector.

View attachment 267926

What is the AC input current? Also, are there any specific EMI/RFI standards you have to meet?

What are the frequencies of the power switching circuits?

ak

Hi I am looking for PC mount filter. However thanks for inputs.

 

The TS was posting about a DC-DC converter application, not necessarily related to problems with the AC line, but with other subsystems connected to the same AC line. That is what the chokes are designed to do, and they work in both directions. We're also not sure the TS has correctly identified and quantified the root cause of the problem. I suspect some amount of hopeful guesswork is involved. It won't hurt to run the experiment to confirm or refute the initial hypothesis.

AC input current is 2A
Following IEC 61K

 

On this page are links to four types of pc mount filters.

https://www.schurter.com/en/Products/Catalog?(pg84)/1

ak