| 摘要 |
PURPOSE:To provide a current-type inverter including an arc self-extinction element in a main circuit under control with a power factor of about 1 without using a specific switching surge absorbing means. CONSTITUTION:A frequency of a voltage control oscillator 11, which is put under control so that an output frequency is set to an oscillation frequency at the center of a resonance frequency of a load 2, is compensated. A pulse (A) with a width in accordance with a term from the start of commutation to a zero voltage is obtained in a blip flop 15 through a current change detection circuit 13 in an inverter 1A and a zero-cross output-voltage detection circuit 14. A voltage signal corresponding to the pulse width is entered in a pulse width/voltage conversion circuit 16 so that a power factor is always made almost equal to zero under control. In addition, while the commutation of the main circuit is obtained full at an output of the current change detection circuit 13, the cut-off of the transistor under off-control can be retarded until this timing. Consequently, the transistor is cut off at a current of zero and the switching surge current can be prevented. |
