Common mode choke in smps

[eem2am]

common mode choke layout

hi

on page 33

**broken link removed**

...do you think the common mode filter could just use the capacitors Ccmf and avoid using the common mode choke?

 

[dipnirvana]

layout common mode choke

yes it can , but again that will depend on the amount of noise you expect from your smps .

if it's only Ccmf , it's simple RC filter . But as u add an inductor (CM choke) it become 2 pole LC filter that has sharper stopband compare to single pole RC filter.

Some time you also want to add more CM choke and capacitor to make ur filter 3 or 4 pole .

 

[eem2am]

common-mode choke application

thanks dipnirvana,

you say "RC" filter...but where is the "R".....are you referring to the resistance of the circuit tracks and conductors?

 

[dipnirvana]

common mode choke lc filter

No, but when u will do the thevnin analysis of ur smps u will find out some source resistance of ur emittin resistance.