The operating voltage of the switching power supply is the highest voltage that the insulating material can withstand when the device is operated at rated voltage under normal operating conditions.
            The safety extra low voltage (SELV) refers to a circuit with a safety voltage protection function. Under normal operating conditions and under single fault conditions, the voltage between any two adjacent parts of the secondary circuit or between the voltage of a part and the protective earth ground of a Class I device shall not exceed a safe voltage value.