Power circuit protection apparatus

A power circuit protection apparatus comprising:

• a transformer comprised of a primary side coil and a plurality of said transformer receiving voltage at the primary side coil and inducing a different voltage in the secondary side coil;
• an output unit which receives a voltage output from the secondary side coils of the transformer, rectifies and smoothes the received voltage, and outputs the rectified and smoothed voltage;
• a pulse width modulation (PWM) controller which receives the voltage output from the output unit and outputs a PWM signal with an adjusted duty cycle;
• a voltage sensing unit which senses the voltage induced in the secondary side coils of the transformer;
• a blocking unit which blocks interference between the voltage sensed in the voltage sensing unit and a first reference voltage;
• and
• a comparison unit which compares a variation value of the first reference voltage with respect to a second reference voltage and outputs a signal determining an on/off operation of the PWM controller.