Patent ID: 7894717

Claim:
A control circuit for a self-exciting DC/DC converter comprising: a switching transistor connected to the primary coil of a transformer; a first resistor, of which one end is connected to said switching transistor, and of which the other end is grounded; a voltage source which generates a predetermined first threshold voltage; a first voltage comparator which compares a first detection voltage, which occurs at the connection between said first resistor and said switching transistor, with the first threshold voltage; a second voltage comparator which compares a second detection voltage, which corresponds to the current that flows through the secondary coil of said transformer, with a predetermined second threshold voltage; and a switching control unit which controls the ON/OFF state of said switching transistor according to the output signals of said first and second voltage comparators, wherein said voltage source has a configuration that allows the first threshold voltage to be adjusted, wherein the control circuit is integrally formed on a single semiconductor substrate, and wherein a first electrode pad is provided to a terminal via which said switching transistor is to be connected to said transformer, and wherein a second electrode pad is provided to a connection that connects said first resistor and said switching transistor, and wherein a third electrode pad is provided to a terminal via which said first resistor is grounded, and wherein a fourth electrode pad is provided to an input terminal of said first voltage comparator, the input terminal being connected to said second electrode pad via an external wiring line.