DC POWER SUPPLY DEVICE AND AIR CONDITIONER

Provided is a DC power supply device and an air conditioner configured so that an element can be protected even when power-supply voltage disturbance such as lightning surge occurs. The DC power supply device (1) includes a bridge rectifier circuit (10) configured such that rectification-side converter elements (Q3, Q4) and switching elements (Q1, Q2) are in bridge connection, a reactor (L1) provided between an AC power supply (Vs) and the bridge rectifier circuit (10), a smoothing capacitor (C1) connected to an output side of the bridge rectifier circuit (10) and configured to smooth voltage applied from the bridge rectifier circuit (10), a zero-cross determination portion (14) configured to determine zero-cross at which the positive and negative polarities of the AC power supply (Vs) are switched from each other, and a converter control portion ( 18) configured to execute the converter element protection operation of turning off the rectification-side converter elements (Q3, Q4) in a case where voltage opposite to determined voltage is detected after determination by the zero-cross determination portion (14).