The switch 12 and the primary winding Wp are electrically connected in series, and are electrically connected between the input terminal I/P and a ground.

The low loss snubber 11 includes a clamping winding Wc, a first capacitor C1, a second capacitor C2, a first diode D1, a second diode D2, a third diode D3, and a first inductor L1.

The first capacitor C1 is electrically connected between an anode of the first diode D1 and a first node n1 connected by the primary winding Wp and the switch 12. A cathode of the first diode D1 is electrically connected to the input terminal I/P.

A cathode of the third diode D3 is electrically connected to the anode of the first diode DE The first inductor L1 is electrically connected between an anode of the third diode D3 and a cathode of the second diode D2.

The second capacitor C2 is electrically connected between the cathode of the second diode D2 and the ground.

The clamping winding Wc is magnetically coupled with the primary winding Wp, and the clamping winding Wc is electrically connected between the ground and an anode of the second diode D2.

The secondary winding Ws is magnetically coupled with the primary winding Wp and the clamping winding Wc, and the secondary winding Ws is electrically connected between the first output terminal O/P1 and the second output terminals O/P2. In a first embodiment of the present invention, a polarity of the clamping winding Wc is opposite to a polarity of the primary winding Wp.