Patent ID: 6914794

Claim:
A power conversion device, comprising: n, n being an integer greater than one, input capacitors which are connected in series between output terminals of a DC input power supply; n inverter circuits which include n inverters whose input terminals are respectively connected to both ends of the input capacitors, and n transformers which have primary windings respectively connected to the n inverters and secondary windings electro-magnetically coupled with the primary windings; and n rectifying circuits which convert AC voltages across the secondary windings into DC voltages; a first error amplifier which generates a first error signal e 1 based on a predetermined reference value and a signal corresponding to the detected value of either one of an output power, a DC output voltage, or a DC output current obtained by combining outputs of the n rectifying circuits: a second error amplifier which generates second error signals e 2 by comparing the voltages across the n input capacitors: and a control circuit which controls the n inverters based on signals obtained by subtracting the respective second error signals e 2 from the first error signal e 1 and on signals obtained by adding the first error signal e 1 to the respective second error signals e 2 , wherein the DC voltages output from the rectifying circuits are combined with each other, semiconductor switching devices used in the inverter circuits have withstand voltages lower than the maximum value of an output voltage of the DC input power supply, and the inverter circuits are controlled such that input voltages applied to the respective inverter circuits are approximately equal to a voltage obtained by dividing the output voltage of the DC input power supply by n so as to balance the voltages across the input capacitors with each other and to voltages lower than the withstand voltages of the semiconductor switching devices are applied to the semiconductor switching devices.