Power convertor

A power conversion device comprising:

• a first rectification circuit which rectifies AC power inputted from an AC power supply;
• an inverter circuit having a first leg, a second leg, and a DC capacitor connected in parallel to each other, the first leg having a first switching element and a second switching element connected in series to each other, a positive-side DC terminal of the first rectification circuit being connected to a first AC end which is a connection point between the first switching element and the second switching element, the second leg having a third switching element and a fourth switching element to which diodes are respectively connected in antiparallel, the third switching element and the fourth switching element being connected in series to each other, the inverter circuit having a negative-side DC bus connected to a negative-side DC terminal of the first rectification circuit;
• a transformer having a primary winding and a secondary winding, one end of the primary winding being connected to the first AC end of the inverter circuit, and another end of the primary winding being connected to a second AC end which is a connection point between the third switching element and the fourth switching element;
• a second rectification circuit having one end connected to the secondary winding of the transformer and another end connected to a DC load via a smoothing capacitor, the second rectification circuit rectifying AC power inputted from the transformer, and outputting the resultant power to the DC load;
• a control circuit which controls operation of the inverter circuit;
• a voltage detector which detects DC voltage of the DC capacitor;
• and
• a current detector which detects current outputted from the first rectification circuit, wherein
• the control circuit determines an ON period for the first leg on the basis of a detection result of the current detector, and controls the first switching element and the second switching element on the basis of the determined ON period for the first leg, thereby controlling current outputted from the first rectification circuit, and
• on the basis of a detection result of the voltage detector and the determined ON period for the first leg, the control circuit controls an ON period for the second leg and a phase shift amount between the ON period for the first leg and the ON period for the second leg, thereby controlling voltage of the DC capacitor to be constant.