Patent ID: 7023717

Claim:
An isolated type switching power supply apparatus which comprises a power supply, a transformer connected to said power supply and comprising a core including primary and secondary sides having primary and secondary windings, respectively, and a switching means for switching an electric current going through the primary winding of said transformer so that an energy generated on the primary side of said transformer is sent to the secondary side in accordance with the operation of said switching means, the apparatus further comprising: a modulating means for modulating an output on the secondary side of said transformer; a transmitting means for transmitting an output of said modulating means through the core of the transformer from the secondary side to the primary side of said transformer; a demodulating means for demodulating the output transmitted by the transmitting means; and a switching means controlling circuit for controlling said switching means, wherein the operation of said switching means is controlled in accordance with an output of said demodulating circuit.