Switching power supply device comparing first and second voltage ranges

A switching power supply device comprising:

• n (where n is an integer of two or higher) converter units that are connected in parallel between a direct current (DC) input unit and a DC output unit;
• and
• a control unit that executes driving control over the n converter units,
• wherein the switching power supply device generates a DC output voltage based on a DC input voltage inputted from the DC input unit and outputs the DC output voltage from the DC output unit to a load,
• the switching power supply device further comprises a voltage comparator unit that compares the DC output voltage with voltage ranges of a first voltage range set in advance and a second voltage range, which is set in advance, has an upper limit value lower than an upper limit value of the first voltage range and has a lower limit value lower than a lower limit value of the first voltage range, and outputs a comparison result to the control unit,
• the control unit is configured to be capable of executing first driving control that drives k1 (where k1 is an integer set so that 0≤k1<n) converter units out of the n converter units, second driving control that drives k2 (where k2 is an integer set so that k1<k2<n) converter units out of the n converter units, third driving control that drives k3 (where k3 is an integer set so that k1<k3<n) converter units out of the n converter units, and fourth driving control that drives k4 (where k4 is an integer set so as to exceed k2 and k3 but be equal to or below n) converter units out of the n converter units,
• the control unit executes the first driving control when, in an execution state of the second driving control, the comparison result has been obtained indicating that the DC output voltage has risen and reached the upper limit value of the first voltage range,
• the control unit executes the second driving control when, in an execution state of the first driving control, the comparison result has been obtained indicating that the DC output voltage has fallen and reached the lower limit value of the first voltage range,
• the control unit executes the third driving control when, in an execution state of the fourth driving control, the comparison result has been obtained indicating that the DC output voltage has risen and reached the upper limit value of the second voltage range,
• the control unit executes the fourth driving control when, in an execution state of the third driving control, the comparison result has been obtained indicating that the DC output voltage has fallen and reached the lower limit value of the second voltage range,
• the control unit executes the fourth driving control when, in an execution state of the second driving control, the comparison result has been obtained indicating that the DC output voltage has fallen and reached the lower limit value of the second voltage range, and
• the control unit executes the first driving control when, in an execution state of the third driving control, the comparison result has been obtained indicating that the DC output voltage has risen and reached the upper limit value of the first voltage range.