Switching mode power supply and method for protection operation thereof

The present invention relates to a switched mode power supply and a protection method of operation. According to the invention, the switching mode, the switching control unit of the power supply, receives the feedback information corresponding to the current sensing information and the output voltage corresponding to the current flowing through the main switch to one terminal, the voltage on the terminals is lower than the reference voltage If the period lasts longer than a predetermined time performs the protection operation. This can reduce the number of terminals with which, at the same time it provides protection operation function. SMPS, the protection operation, the current sensing information, feedback information,