| 摘要 |
The polarities of output voltages from a plurality of phases formed by means of switching elements S1 to S6 are switched by turning the switching elements S1 to S6 on or off. Voltages having a positive or negative polarity are formed across secondary coils L2, L4 and L6 of transformers T1 to T3, in accordance with the switching of the switching elements S1 to S6, and these voltages are combined. The switching of the switching elements S1 to S6 is controlled in such a way that a circulating path that is not supplied with electric power from a direct-current power supply 10 is formed by means of a switching element for generating a negative voltage, a capacitor connected to said switching element, and a transformer connected to said switching element. A negative voltage is generated by means of the circulating path employing said capacitor. |
