2.7 Common Mode Filter

Since this application report only summaries the techniques to improve radiated and current method conducted EMI, which mainly comes from the common mode noise, it won’t discuss the design of the input differential mode filter, which has been verified to make little difference. The measurement results with and without the common mode choke are shown in Figure 20 and Figure 21.

(a) With common mode choke

(b) Without common mode choke

Figure 20. Radiated Emissions: Common Mode Filter

(a) With common mode choke

(b) Without common mode choke

Figure 21. Conducted Emissions: Common Mode Filter