Patent ID: 8724347

Claim:
A switching control circuit for use in a power conversion circuit of a switching power supply apparatus, the switching control circuit comprising: a plurality of external terminals; a semiconductor integrated circuit arranged to control on/off operations of a switching device; a soft start terminal that receives a control voltage used to control of on/off switching operations of the switching device during a soft start period, which is an activation period from a start of an operation to a steady operation of the power conversion circuit; a soft start controller arranged and programmed to control an on-period of the switching device during the activation period based on a signal of the soft start terminal; and a maximum on-pulse period limiting device arranged to detect, as a determination object signal, a voltage induced in an external circuit that is connected to the soft start terminal and that includes at least a resistor element or a semiconductor element, and arranged to set a limit value of an on-period of the switching device during a normal period in accordance with the determination object signal.