Power supply device performing voltage conversion

A power supply device comprising:

• a first voltage generating unit configured to generate a first voltage;
• a controller configured to output a control signal specifying a voltage value;
• and
• a voltage conversion unit configured to convert the first voltage to a second voltage in response to a control signal specifying a voltage value output from the controller, and output the second voltage,
• wherein the voltage conversion unit converts the first voltage to a start voltage, as the second voltage, in response to a first control signal specifying a start voltage value output from the controller and further converts the first voltage to a target voltage, as the second voltage, in response to a second control signal specifying a target voltage value output from the controller,
• wherein a transition period of time is intervened between generation of the start voltage and generation of the target voltage during which the controller outputs a third control signal specifying the intermediate voltage value between the start voltage value and the target voltage value.