Abstract: A direct current power unit has main and secondary direct current power supplies, a serial circuit, and first and second parallel circuits. One terminal of the secondary direct current power is connected to one terminal of the main direct current power supply. The serial circuit consists of a choke coil and a first capacitor, of which each terminal is connected to each terminal of the main direct current power supply. The first parallel circuit consists of a first diode and a first switching element, of which each terminal is connected to each terminal of the first capacitor. The second parallel circuit consists of a second capacitor, a second diode, and a second switching element connected between the serial connected point of the choke coil and the first capacitor and the other terminal of the secondary direct current power supply. Each terminal of a third capacitor is connected to each terminal of the secondary direct current power supply.