Power factor improvement circuit and semiconductor apparatus

A semiconductor apparatus that controls, on the basis of an output voltage when a switching power-supply apparatus is in a light-load state or a no-load state, a burst operation for switching between a stopped state in which a switching operation of a switching element is disabled and an operating state in which the switching operation of the switching element is enabled, the semiconductor apparatus comprising:

• a first circuit that outputs a first voltage that corresponds to an error between a reference voltage and a voltage obtained by dividing the output voltage;
• a second circuit that outputs a second voltage that starts to rise from a predetermined initial value in synchrony with the switching element being turned on;
• a third circuit that outputs a signal for turning off the switching element when the second voltage has reached the first voltage;
• and
• a clamp circuit that, while the burst operation is performed, clamps a lower limit of the first voltage, which decreases when the switching operation of the switching element in the stopped state is disabled, at a lower-limit voltage higher than a ground voltage of a power factor improvement circuit including the semiconductor apparatus and clamps an upper limit of the first voltage, which increases when the switching operation of the switching element in the operating state is performed, at an upper-limit voltage.