Power supply apparatus

A charging apparatus that charges a direct current battery, comprising:

• a step-down converter unit that is configured to convert a direct current voltage input from a power supply, to which a direct current voltage from a power supply is input and that converts the direct current voltage, wherein when a voltage of the direct current battery is between a predetermined first voltage lower than a charge completion voltage of the direct current battery and the charge completion voltage, a variable voltage that increases from the first voltage to the charge completion voltage in accordance with charging of the direct current battery is input to the step-down converter unit;
• a step-up converter unit to which a direct current voltage from a power supply is input and that converts the direct current voltage, wherein
• the direct current voltage converted by the step-up converter unit is input in the step-down converter unit,
• the first voltage is input in the step-up converter unit,
• when the voltage of the direct current battery is lower than the first voltage, the step-down converter unit is subjected to voltage control such that an input voltage to the step-down converter unit is the first voltage, and
• when the voltage of the direct current battery is between the first voltage and the charge completion voltage, the step-down converter unit is subjected to the voltage control such that the input voltage to the step-down converter unit is the voltage of the direct current battery.