| 摘要 |
PURPOSE:To prevent an overvoltage from being applied to a power transistor for controlling a current at the starting time of a motor by connecting a voltage drop element before reaching the prescribed number of revolution of the motor at the starting time. CONSTITUTION:A switching controlling circuit 8 conducts transistors 9-11 connected in series with motor coils 13-15 ON in response to the output of a Hall element which detects the rotating position of a rotor. On the other hand, a transistor 12 is controlled by a number of revolution control signal. A current is flowed through the motor via a resistor 23 at the time of starting the motor. When the number of revolution of the motor becomes the prescribed value, a relay 25 is closed, thereby shortcircuiting the resistor 23. In this manner, overvoltage is prevented from being applied to a power transistor at the time of starting the motor. |
