| 摘要 |
PURPOSE:To apply a sufficient inverse bias to a power switching element at the motivation and to prevent a destruction owing to a peak voltage applied to the element and the dv/dt by furnishing an auxiliary voltage source to maintain the voltage of a flat capacitor even when an inverter is stopped. CONSTITUTION:An inverse bias application circuit 27 is composed of a combination coil 12 combined magnetically to a heating coil 1, a flat capacitor 13, a rectifier element 14, a switching element 15 for driving, and an auxiliary voltage source 24, and the auxiliary voltage source 24 is composed of a transformer 25 and a diode 26. And the terminal voltage VC of the flat capacitor 13 maintains a constant voltage VCO by the operation of the auxiliary voltage source 24 even before the operation of an inverter 7, and when the inverter 7 is operated in such a condition, a current is fed from the combination coil 12 to the flat capacitor 13 to charge it. And since the VC is applied in the inverse bias condition making the VBE in a large inverse bias, the power switching element is never destroyed by the peak of the VCE and the dv/dt at the starting. |
