Electronics > Projects, Designs, and Technical Stuff

Conducted emissions conundrum

(1/5) > >>

colsramble:
We have an existing commercial product (mains powered with internal SMPS) which we're augmenting with an add-on module that by necessity requires it's own power supply. The existing product has been EMC certified, and the power supply we've chosen to power the add-on module is a Meanwell brick that is itself EMC certified. Unfortunately when we plug them together we're seeing excessive conducted emissions back through the existing product.

We're struggling to find a suitable workaround or address the root cause - the emissions themselves are quite low in frequency so ferrite beads don't help much, and the only real success has been placing an EMI filter inline with both devices.

Changing power supplies and isolating the Earth on both supplies gives some improvement but neither are practical or desirable long term.
 
I'm hoping this is a good place to find some ideas or expertise to help isolate the root cause and/or workaround the problem.

Thanks in advance!

T3sl4co1l:
Y cap across the new supply.

Tim

srb1954:
Add an additional common-mode choke on the mains input. These are more effective at reducing the lower frequency conducted emissions than ferrite beads.

colsramble:

--- Quote ---Y cap across the new supply.
--- End quote ---

Thanks Tim, it's my understanding that both SMPS have Y caps already, but given it's an off-the-shelf device I'm not sure how we'd add one externally? Do you mean external Y-caps between active/neutral and ground on the input of the new supply?


--- Quote ---Add an additional common-mode choke on the mains input. These are more effective at reducing the lower frequency conducted emissions than ferrite beads.
--- End quote ---

Thanks srb1954, yes I think that's pretty much what the inline EMI filter is, common mode choke with CX and CY. A combination of what you're both suggesting perhaps.

We've been hunting around for such a filter that we can just buy and add retrospectively - both devices have IEC connectors for power connection, so something that acts as a dual IEC adapter with inline filter would be perfect but the closest thing we've found so far was over $300 a piece ?!?     

Psi:

--- Quote from: colsramble on August 05, 2020, 07:33:22 am ---We have an existing commercial product (mains powered with internal SMPS) which we're augmenting with an add-on module that by necessity requires it's own power supply. The existing product has been EMC certified, and the power supply we've chosen to power the add-on module is a Meanwell brick that is itself EMC certified. Unfortunately when we plug them together we're seeing excessive conducted emissions back through the existing product.

--- End quote ---

Not sure i can offer any help, just some words of understanding with regard to meanwell and EMC

My bedroom is illuminated entirely by hidden LED strip lighting in two large rings around the ceiling.
It is powered by a meanwell brick PSU (one of the 5V 40A open frame ones, mounted in a box).
It totally f's up the alarm clock/FM radio on my bedside table, pretty much jamming the FM station out of existence whenever the light is on.
And before anyone asks, this meanwell psu was bought from mouser, it's definitely genuine.

Note: I'm not 100% sure it's really the meanwell PSUs fault, it might be my MCU switching frequency driving the RGBW addressable LEDs in a nice inductive ring around the room :)

Navigation

[0] Message Index

[#] Next page

There was an error while thanking
Thanking...
Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod