TRANSFORMER FOR REDUCING ELECTROMAGNETIC INTERFERENCE AND POWER TRANSFORM CIRCUIT APPLIED THEREIN

摘要

A transformer for reducing the electromagnetic interference (EMI) effect is disclosed. The transformer includes a bobbin; a magnetic core assembly partially sleeved by the bobbin; a first primary winding coiled around the bobbin; a secondary winding coiled on the first primary winding; and a first shielded element disposed between the first primary winding and the secondary winding for disconnecting the EMI transmission from the first primary winding to the secondary winding. The first primary winding includes a first winding portion and a second winding portion, and the first winding portion has larger EMI comparing to the second winding portion. The first winding portion of the first primary winding is adjacently disposed to the magnetic core assembly for shielding the EMI of the first primary winding by using the magnetic core assembly. The second winding portion is coiled on the first winding portion and adjacently disposed to the secondary winding for increasing the electromagnetic coupling rate of the first primary winding and the secondary winding. In addition, a power transform circuit applied in the transformer for reducing the EMI effect is also disclosed. The power transform circuit includes a switch, a power input for receiving a power signal; and a transformer electrically connected to the power input and the switch, for receiving and transforming the power signal.