Buck converter with isolated auxiliary output
Based on DER-226, I have built a circuit using a coupled inductor (1:1) and keeping the auxiliary output floating in order to provide some electrical isolation. The problem is that the ripple of the auxiliary output is around 2Vpp while the main output is around 0.2Vpp. If I join both return paths the ripple current shrinks to almost the same level. Have anyone tried this and get good results with the auxiliary output isolated?
Comments
I guess the issue is most likely caused by the common mode noise between the two windings of the buck inductor. PLS float the the auxiliary winding, and place a cap between the return of these two outputs, and the issue should be solved.The cap is a Ycap, and the common mode noise is circulated between these windings.
Thank you very much for your quick repply.
We have added a 1.8nF capacitor and works pretty well.
Best regards and thanks again.
I guess the issue is most likely caused by the common mode noise between the two windings of the buck inductor. PLS float the the auxiliary winding, and place a cap between the return of these two outputs, and the issue should be solved.The cap is a Ycap, and the common mode noise is circulated between these windings.