Switching mode power supply apparatus and power supply method thereof

A power supply for protection of insulation in an apparatus, comprising:

• a conversion unit to convert input power into output power having a predetermined voltage;
• an emitting unit to output an emittance upon the voltage of the output power exceeding a threshold voltage;
• a receiving unit to receive the emittance output from the emitting unit and output a signal indicative of the voltage of the output power;
• a controller to control an operation of the conversion unit based on the output signal from the receiving unit;
• and
• a disconnection unit to disconnect power applied to the receiving unit if a voltage of the power applied to the receiving unit exceeds a trigger voltage, the disconnection unit comprising:
• a detector to detect a voltage of power applied to a terminal of the controller, and
• a switch turned on based on the voltage of power applied to the terminal of the controller detected by the detector and making one end of a fusible element be grounded so that the fusible element is opened to protect insulation in the apparatus.