| 摘要 |
PURPOSE:To obtain a brushless motor driving circuit with low power loss by consisting a control current changing in exponential function form for a motor speed control voltage as the base current of a switching transistor for the switching and conduction of an exciting coil. CONSTITUTION:When the speed control voltage Vs is small, a transistor Q5 is fixed at an operating point decided by resistors R6-R9 in accordance with the OFF of the diode D to fix a collector electric potential and constant base current Ib are flowed into driving transistors Q3, Q4 through transistors, Q6, Q7 which are turned on and off by switching signals, (a), (b). With the speed control voltage Vs increased, a current starts to flow into the diode D to increase the base voltage of the transistor Q5 and to decrease the collector electric potential of the transistor Q5. Therefore, the collector currents of transistors Q8, Q9 increase to raise the base currents IB of the driving transistors Q3, Q4 as well. The rate of increase of the base currents IB is decided by the operating current of the diode D caused by installing split resistors R3, R4. |
