Patent ID: 8228152

Claim:
A transformer, applied in a flyback transformer device which comprises a transistor for performing switch operation and used with a single first capacitor, comprising: a magnetic element; a first winding and a second winding, both of which are disposed around the magnetic element, wherein a terminal of the first winding and a terminal of the second winding have the same polarity; and a shield disposed between the first winding and the second winding, wherein a terminal of the shield is directly electrically connected to a first terminal of the first capacitor, and a second terminal of the first capacitor is electrically connected to an electrical potential point with an invariable voltage level and the transistor; wherein the first terminal of the first capacitor is a floating point and the second terminal of the first capacitor is electrically connected to a fixed point of the first winding, and wherein the shield cooperates with the first capacitor to balance the common mode current between the first winding and the second winding so as to reduce a common-mode noise.