Control circuit and switching power supply

A switching power supply device comprising:

• a switching element connected to a first output terminal and a second output terminal of the switching power supply device, the first output terminal being higher in voltage level than the second output terminal;
• and
• a control circuit connected to the switching element and configured to control switching element,
• the control circuit comprising:
• a reference voltage source:
• a constant voltage source having a positive terminal and a negative terminal, the positive terminal being connected to the first output terminal, and a voltage between the positive terminal and the negative terminal being constant;
• a comparator having at least a first input terminal, a second input terminal, and a third output terminal, the first input terminal being connected to the negative terminal of the constant voltage source, and the second input terminal being connected to the reference voltage source;
• and
• a controller connected between the third output terminal of the comparator and the switching element, the controller being configured to control the switching element based on an output of the comparator,
• wherein a voltage of the reference voltage source becomes a first voltage in a case that the output of the comparator is at a first voltage level,
• the voltage of the reference voltage source becomes a second voltage in a case that the output of the comparator is at a second voltage level different from the first voltage level, and
• the second voltage is different from the first voltage.