I am measuring conducted emission at the input of a SEPIC converter.
At first, the emissions are only about 45 dBµV at switching frequency.
But when I put my finger on the SEPIC (coupled) inductor, the emissions go up to about 65 dBµV (!).
Even worse, if I move the input cable close to the SEPIC (coupled) inductor, the emissions can go up to 70 dBµV.
If I stick a piece of copper foil on top of the inductor and connect the foil to GND, then the emissions go only up to 48 dBµV.
In a larger production, it is not feasible to use copper foil. Also, I cannot stop the cable from touching the inductor. Therefore:
- What else can could be done to solve my problem?
- How can this behaviour be explained?