Magnetic device

A magnetic device, comprising:

• a magnetic core assembly comprising:
• a first magnetic leg, a second magnetic leg and a third magnetic leg;
• a primary winding wound around the second magnetic leg;
• at least one secondary winding wound around the second magnetic leg or the third magnetic leg, wherein the at least one secondary winding comprises a first secondary winding;
• and
• an auxiliary winding electrically connected with an auxiliary inductor and wound around at least one of the first magnetic leg, the second magnetic leg or the third magnetic leg, wherein the auxiliary winding is magnetically coupled with the primary winding and the at least one secondary winding;
• wherein the primary winding is electrically connected with a first switch circuit of a power device, and the at least one secondary winding is electrically connected with a second switch circuit of the power device, wherein when switches of the first switch circuit turn off and switches of the second switch circuit turn on, an superposed AC voltage coupled by the auxiliary winding is applied on the auxiliary inductor.