| 摘要 |
PURPOSE:To provide a contactless motor having high reliability by branching and controlling the input current of a Hall element, amplifying the output voltage of the Hall element and switching it by a transistor, and controlling the bias of the transistor. CONSTITUTION:When the driving current is increased by the rise of a power source voltage or by the increase of a load, the voltage drop of a motor driving current detecting resistor 49 will increase and the voltage between the base and the emitter of a controlling transistor 46 will rise. Accordingly, the transistor 46 is conducted, the input current of the Hall element 41 is branched, and consequently the input current will become small, and the Hall output voltage will become low. Therefore, it becomes a driving current limiting circuit to the set resistance value of the resistor 49. Further, the bias potentials of the transistors 42, 43 are also controlled. When the driving current is limited, the locking of a rotor can be prevented, and the burnout and damage of the driving coil and the transistors can be prevented. |
