Continue to Site

Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Common mode choke off board gives better EMC pass?

Status
Not open for further replies.
T

treez

Guest
Hello,
We have failed Conducted mode emissions with our offline 150W LED driver. However, we added a Common Mode Choke in the mains cable (as in the attached) and then it passed conducted EMC.
We now are wondering about making room on the LED driver PCB so that we can fit the common mode choke on the PCB.
However, do you agree that if we place the very SAME common mode choke on the PCB, then we will have less chance of passing conducted emissions, because common mode noise is high frequency and can “radiate” around the common mode choke on the PCB and get into the earth return wire like that?
(The common mode noise is doubtless coming from the 1W Buck bias supply on this 150W Linear LED driver. The Earth wire in the mains cable does not actually get onto the PCB, but rather is screwed to the heatsink.)
 

Attachments

  • Common mode choke off board.jpg
    Common mode choke off board.jpg
    46.1 KB · Views: 95

The incoming and outgoing currents who carry noise signals will be cleaned through Common Mode Choke coil due to 180 degree summing.
Leakage from the coil can always be present but it is negligible due to closed form structure of the choke.In additional to, GND connection can also be "beaded" just before it exits.
 

Thanks, but the ground connection gets the 25A of current continuity test in production...i dont think we can bead it, as it will make the earth connection too high impedance
 

Thanks, but the ground connection gets the 25A of current continuity test in production...i dont think we can bead it, as it will make the earth connection too high impedance
The main target is to reduce the "induced" high frequency currents who want to exit from the closure, right ?? They will essentially be relatively low, I think it's possible.
Another option is to shield the GND cable.. If it's possible thru a metallic pipe ..just an idea to protect this clean side from induction.
 

Status
Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Back
Top