| 摘要 |
PURPOSE:To enhance the reliability by forming a base drive circuit of two base current supply circuits, and selecting the base current supply circuit of high output value at starting time. CONSTITUTION:An AC is converted into a DC by a rectifier 1, and converted into an AC by an inverter 3 having switching transistors 4P-6N through a smoothing capacitor 2 to drive an AC load 9 such as a 3-phase AC motor. Base amplifiers 10P-12N, a start timing circuit 13 and a controller 8 are provided, and the amplifier 10P-12N are composed of controller 21, the first and second base current supply circuits 22H, 22L and a base reverse bias supply circuit 23. Thus, the base current may be output only during a short time of inverter starting time to reduce the rated current of the circuit 22H and a small base current is sufficient at normal time to reduce the size and the weight of the circuits 22. |
