Switching power supply

A switching power supply comprising:

• a switching output circuit configured to generate an output voltage from an input voltage according to ON/OFF control of an output transistor by a pulse width modulation signal;
• a first voltage generating circuit configured to generate a first voltage based on a difference between the output voltage or a corresponding feedback voltage and a predetermined reference voltage;
• and
• a digital signal processing circuit configured to generate the pulse width modulation signal,
• wherein the digital signal processing circuit sets a duty cycle (DUTY) of the pulse width modulation signal based on the following formula:
• DUTY=D1/{(Kslp×Sslp+Kcs×Scs)×T},
• where, D1 denotes a digital value of the first voltage, Sslp denotes a predetermined voltage slope, Scs denotes a current slope varied depending on the output current flown through the switching output circuit, Kslp denotes a voltage slope coefficient, Kcs denotes a current slope coefficient, and T denotes a switching period, and
• wherein at least one of the voltage slope coefficient and the current slope coefficient is randomly adjusted.

A switching power supply comprising:

• a switching output circuit configured to generate an output voltage from an input voltage according to ON/OFF control of an output transistor by a pulse width modulation signal;
• a first voltage generating circuit configured to generate a first voltage based on a difference between the output voltage or a corresponding feedback voltage and a predetermined reference voltage;
• a second voltage generating circuit configured to generate a triangular or sawtooth-waved second voltage;
• a comparing circuit configured to generate a comparison signal by comparing the first voltage and the second voltage;
• a clock oscillating circuit configured to generate a clock signal having a switching frequency;
• and
• a logic circuit configured to generate the pulse width modulation signal in response to the clock signal and the comparison signal,
• wherein the second voltage generating circuit generates the second voltage by adding a first slope voltage having a first slope and a second slope voltage having a second slope according to an output current flown through the switching output circuit, and at least one of the first slope or the second slope is set by a set value that is adjusted by a control circuit.