Abstract: A direct-current power supply apparatus includes a rectifier circuit that rectifies a power-supply voltage output from an alternating-current power supply, a smoothing capacitor that smooths an output voltage of the rectifier circuit and outputs a direct-current voltage, a switch connected between an output side of the rectifier circuit and an input side of the smoothing capacitor, a zero crossing detector that detects a zero crossing point of the power-supply voltage, and a controller. The controller includes an adjustment circuitry that sets a switching period such that timing of an on switching operation of the switch falls between a zero crossing period that is a period for the zero crossing point detected by the zero crossing detector, and a zero crossing average period, and a switch control circuitry that outputs an on signal to the switch in accordance with the switching period set by the adjustment circuitry.