Switching converter and ac adapter using the same

An alternating current (AC) adaptor comprising:

• a bridge rectifier rectifying an input AC voltage to convert the input AC voltage into direct current (DC) power;
• a switching converter inducing the DC power applied to a first coil of a transformer T to a secondary coil of the transformer T through a switch SW connected to the primary coil and rectifying the induced power by a synchronous rectifier (SR) connected to a secondary coil;
• a feedback unit sensing a state of a voltage finally output by the switching converter and transferring information on the sensed state of the voltage to a pulse width modulation (PWM) adjuster;
• and
• the PWM adjuster outputting a control signal of which a pulse width is modulated according to a signal fed back from the feedback unit to the switch SW,
• wherein the switching converter includes a delay locked loop connected between the secondary coil and the synchronous rectifier SR, the delay locked loop generating a signal synchronized with a turn-on control signal of the switch SW and outputting the generated signal to the synchronous rectifier SR to control a turn-off operation of the synchronous rectifier SR.