It is called UVLO for short. Also known as an undervoltage protection circuit. It is the function to stop the power supply when the input voltage gets too low. When the input voltage drops, the input current increases if the load is constant. If the input voltage drops below the input voltage range, it may become a problem as the temperature of the input part rises (loss due to resistance component increases) due to the increase in current. In the absence of UVLO, overcurrent protection of the power supply (of pre-stage) may work at the start-up, causing a problem such that the power supply does not start up. Not all power supplies have this feature.