Patent ID: 7031128

Claim:
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.