Switching power-supply circuit and semiconductor integrated circuit

A semiconductor integrated circuit that generates a predetermined output voltage by controlling a first switching transistor connected to a power supply and a second switching transistor connected between the first switching transistor and the ground, the semiconductor integrated circuit comprising:

• a first driver configured to drive the first switching transistor;
• a second driver configured to drive the second switching transistor;
• a reference voltage generator configured to generate a reference voltage;
• a soft-start voltage generator configured to generate a soft-start voltage that increases gradually after the time of start;
• and
• an error amplifier configured to amplify an error voltage between a feedback voltage based on the predetermined output voltage and the soft-start voltage, and to control the first and second drivers in accordance with an amplified error voltage,
• wherein the reference voltage is inputted to the error amplifier, and
• the error amplifier includes an offset applying circuit having a resistor configured to apply an offset voltage to the feedback voltage and the reference voltage, and
• the error amplifier does not start outputting the amplified error voltage until the soft-start voltage increases to a predetermined value.

A switching power-supply circuit that generates a predetermined output voltage by controlling a first switching transistor connected to a power supply and a second switching transistor connected between the first switching transistor and the ground, comprising:

• a first driver configured to drive the first switching transistor;
• a second driver configured to drive the second switching transistor;
• and
• a controller, configured to permit, upon receipt of an externally inputted signal for directing the controller to start operation, the second driver to turn on the second switching transistor after the first driver has turned on the first switching transistor at least one time;
• wherein the controller comprises:
• a latch circuit configured to receive a signal inputted to the first driver and a start signal for starting an operation of the switching power-supply circuit;
• and
• a logic circuit configured to output a high level signal when an output signal of the latch circuit and the signal inputted to the first driver are high levels;
• wherein the second driver includes a delay circuit configured to delay a signal inputted form the controller.