| 摘要 |
PURPOSE:To definitely prevent the short-circuit of a bidirectional control element by detecting ON/OFF state of the bidirectional control element, performing a positional control of the bidirectional control element and suppressing the application of a steep voltage during commutation. CONSTITUTION:A current detector 2 check whether currents are flowing to six bidirectional control elements 4 forming a power conversion circuit 3. If the currents flow, two bidirectional control elements 4 are being fired; if no current flowing, all of the six bidirectional control elements 4 are not fired and in off state. A processing controller 1 inputs a current signal from the current detector 2 and shifts the gate firing timing until a current absence signal enters if a current presence signal enters during gate firing for the bidirectional control element 4. Because of this, the occurrence of a steep voltage change can be prevented during the commutation of bidirectional control element 4. |
