| 摘要 |
PURPOSE:To prevent overvoltage to the electronic switches by connecting auxiliary DC power sources of (n-1) units between the connecting points of the electronic switches of (n-1) units in the first and second series connected bodies comprising the electronic switches of n units. CONSTITUTION:The auxiliary DC power sources 22 and 23 whose voltage is lower than DC power source voltage 1 are connected between the connecting points 24 and 25, and between 26 and 27 in the series connected bodies comprising electronic switches 2-3, 4-5, 6-7, and 8-9. For example, when the electronic switches 2 and 3 are turned OFF, the electronic switch 2 is turned OFF at first. Then a closed circuit comprising a diode 5b, the power source 22, the electronic switch 3, a load 19, and the electronic switches 8 and 9 is formed. The voltage difference between the DC power source 1 and the auxiliary DC power source 22 is applied on the electronic switch 2. Therefore the overvoltae is not applied. |
