| 摘要 |
PURPOSE:To reduce the power loss in transistors by a method wherein the transistors used in a motor drive circuit are operated in saturation mode at all times, and another speed control transistor is used for controlling the rotational speed of the motor. CONSTITUTION:When a power supply switch is turned on, a bias current flows in the inputs of Hall elements H1, H2 via a constant-voltage diode ZD, and corresponding to the position of the rotor, a Hall voltage is produced in the output terminal of either one of the Hall elements H1, H2. By this output voltage, transistors Q1-Q4 operate switching. In response to this, transistors Q5-Q8, which always operate in saturation mode, operate switching, a current flows sequentially in drive coils L1-L4, and the rotor rotates. The transistors Q5-Q8 are connected to a speed control transistor Q9, and the currents flowing in coils L1-L4 are controlled by varying the impedance between the collector and the emitter of the transistor Q9. |
