Apparatus for controlling power converter

An apparatus for controlling a power converter, the power converter comprising:

• a first converter configured to convert an AC voltage supplied from an alternating current (AC) power source into a direct-current (DC) voltage by operations of an input side switch;
• a DC link capacitor configured to be charged with the DC voltage supplied from the first converter;
• a second converter comprising a primary side circuit including one or more output side switches, a secondary side circuit electrically connected to an object to be powered, and a transformer isolating the primary side circuit and the secondary side circuit from each other, the second converter being configured to step down the DC voltage supplied from the DC link capacitor by operations of the one or more output side switches and supply the stepped down voltage to the object to be powered;
• and
• a voltage detector configured to detect an output voltage of the second converter,
• wherein the apparatus comprises:
• a lower limit calculator configured to calculate a lower limit of a voltage across the DC link capacitor based on an output voltage detected by the voltage detector, a turns ratio of the transformer, and a ratio of a turn-on period to one switching period for the one or more output side switches;
• and
• a switch controller configured to operate the input side switch to control a link voltage that is a voltage across the DC link capacitor to a command voltage higher than the lower limit.