Switching power supply device

A switching power supply device comprising:

• a main switching element connected to a DC power supply;
• an ON-timer configured to control a period of time in which the main switching element is on;
• a voltage detecting circuit configured to detect an output voltage of a filter circuit connected to the main switching element;
• a triangular wave generator configured to generate a triangular wave signal;
• a feed-forward circuit configured to generate a feed-forward output whose value decreases as a value of a DC voltage from the DC power supply increases;
• and
• a comparator configured to compare a second reference voltage generated by adding together a first reference voltage, the triangular wave signal from the triangular wave generator, and the feed-forward output from the feed-forward circuit, with the output voltage from the voltage detecting circuit, and based on a result of the comparison, output an ON-trigger signal for turning on the main switch element to the ON-timer.