Patent ID: RE44228

Claim:
A switching mode power supply comprising: a power supply unit comprising a switching transistor, coupled to a primary coil at a primary side of a transformer for converting an input DC voltage and that supplies power to a secondary coil at a secondary side of the transformer and a tertiary coil at a secondary the primary side of the transformer according to an operation of the switching transistor; a switching controller configured to receive a feedback voltage corresponding to a first voltage generated in the tertiary coil at the secondary side of the transformer , and to receive a detection signal corresponding to a current flowing to the switching transistor to generate a switching control signal for controlling the turn on/off of the switching transistor; and a feedback signal generator configured to receive the first voltage and the switching control signal to set a sampling period, and to set a voltage level of the first voltage that is sampled by one pulse of a first pulse string within the sampling period as a feedback voltage, using a plurality of pulse strings comprising the first pulse string and a second pulse string, having a plurality of pulses.