POWER ADAPTER HAVING ULTRA LOW STANDBY POWER

A standby power system for a flyback converter is disclosed. The flyback converter includes a primary-side, a secondary-side, an output terminal at the secondary-side, and a secondary-side controller, where the output terminal is configured to electrically connect to a load. The standby power system comprises a comparator at the secondary-side, an opto-coupler in signal communication with the primary-side, the secondary-side, and the comparator, and a cable detach detector (or load detector). The cable detach detector is configured to determine whether a device is electrically connected to the flyback converter through a charging cable and to set the flyback converter into a standby mode if the deice is disconnected from the charging cable.