| 摘要 |
PURPOSE: To greatly improve reliability, a response, weight, a heat loss and a cost by insulating output-side power sources from each other and individually providing the output-side power source between respective gate driving circuits to electrically insulate the output-side power sources from each other between respective a.c. switches and connecting the change-over signal of a control circuit to the input side of the respective gate driving circuit. CONSTITUTION: The respective ends of a.c. switches SW1, SW2, SW3 all are connected in common to one end of an a.c. power source 1. The other end of the a.c. power source 1 is connected to one end C of a transformer TR1. The outputs of gate driving circuits ID1, ID2, ID3 are respectively connected to the gate inputs of the a.c. switches SW1, SW2, SW3. The input-side power source of the respective gate driving circuits ID1, ID2, ID3 is connected to a control circuit power source VC, and output-side power sources are respectively connected to exclusive power sources±V1,±V2,±V3 which are electrically insulated from each other. The control outputs S1, S2, S3 from a control circuit CONT are respectively connected to the input sides of the gate driving circuits ID1, ID2, ID3.
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