Switching power supply device

A switching power supply device including a switching element connected to a primary winding of a transformer to which direct current power is supplied, a control circuit that performs switching-control of the switching element, and a load that is connected to a secondary side of the transformer and to which an output voltage is supplied via a rectifier circuit, the switching power supply device comprising:

• an output voltage detection unit that detects the output voltage and outputs an output voltage detection value,
• wherein the control circuit comprises:
• a target voltage generation unit that generates an output voltage setting value for setting the output voltage that is supplied to the load;
• an A/D conversion unit that converts an error between the output voltage setting value and the output voltage detection value into a digital signal and outputs the digital signal;
• a digital compensation unit that computes an amount of control based on an output signal of the A/D conversion unit;
• and
• a PWM signal generation unit that generates a PWM signal for the switching element based on an output signal of the digital compensation unit and outputs the PWM signal, and
• the target voltage generation unit detects a standby state based on the output voltage detection value, the output signal of the A/D conversion unit, and the output signal of the digital compensation unit, and, when detecting the standby state, switches the output voltage setting value to a second setting voltage value lower than a first setting voltage value for a state other than the standby state.