• Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

Y capacitors downstream of common mode choke in an offline SMPS

Status
Not open for further replies.

Flyback

Well-Known Member
Hello,

We have seen a report detailing that Y capacitors in an offline SMPS should be placed upstream of a common mode choke. (as in the attached schematic)

However, I always thought that it was better if they were downstream of it. If one only has two Y capacitors, then surely they should best be placed downstream of the Common mode choke, as in page 4 of the following….
Do you agree?

Page 4 shows Y capacitors downstream of common mode choke…
http://www.ti.com/lit/ug/sluu263c/sluu263c.pdf
 

Attachments

JimB

Super Moderator
Most Helpful Member
Do you agree?
Not necessarily.

I guess it all depends if you want to stop noise entering the PSU, or, noise leaving the PSU.
The capacitors, in conjunction with the CM Choke will give different attenuation in each direction.

JimB
 
Status
Not open for further replies.

Latest threads

EE World Online Articles

Loading
Top