DC power-supply device and refrigeration-cycle application device including the same

A DC power-supply device that converts an alternating current into a direct current and supplies the direct current to a load, comprising:

• a rectifier circuit to rectify the alternating current;
• a reactor connected to an input side or an output side of the rectifier circuit;
• a first capacitor and a second capacitor serially connected between output terminals to the load;
• a charging unit to selectively charge one or both of the first capacitor and the second capacitor;
• a first voltage detection unit to detect a voltage of the first capacitor;
• a second voltage detection unit to detect a voltage of the second capacitor;
• and
• a control unit to control the charging unit, wherein:
• the control unit controls at least one of a charging period of the first capacitor and a charging period of the second capacitor,
• by changing at least of one of the charging period of the first capacitor and the charging period of the second capacitor with respect to a voltage difference between the first capacitor and the second capacitor at a first time, a voltage difference between the first capacitor and the second capacitor at a second time, which is after the first time, is made small,
• the alternating current is a three-phase alternating current,
• the control unit controls the charging unit in such a manner that, when a period obtained by combining a charging period and a non-charging period of a pair of the first capacitor and the second capacitor is designated as one cycle, a charging frequency becomes 3n times (n is a natural number) higher than a frequency of the three-phase alternating current, and
• the charging frequency is an inverse number of the one cycle.